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Network Working Group C. Newman
Internet Draft: ACAP Innosoft
Document: draft-ietf-acap-spec-04.txt J. G. Myers
Netscape
June 1997
Expires in six months
ACAP -- Application Configuration Access Protocol
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
To view the entire list of current Internet-Drafts, please check the
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
Abstract
The Application Configuration Access Protocol (ACAP) is designed to
support remote storage and access of program option, configuration
and preference information. The data store model is designed to
allow a client relatively simple access to interesting data, to allow
new information to be easily added without server re-configuration,
and to promote the use of both standardized data and custom or
proprietary data. Key features include "inheritance" which can be
used to manage default values for configuration settings and access
control lists which allow interesting personal information to be
shared and group information to be restricted.
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Table of Contents
Status of this Memo ............................................... i
Abstract .......................................................... i
ACAP Protocol Specification ....................................... 1
0. Changes from version -03 to version -04 .................. 1
0.1. Open Issues .............................................. 3
1. Introduction ............................................. 3
1.1. Conventions Used in this Document ........................ 3
1.2. ACAP Data Model .......................................... 3
1.3. ACAP Design Goals ........................................ 3
1.4. Validation ............................................... 4
1.5. Definitions .............................................. 4
1.6. ACAP Command Overview .................................... 6
2. Protocol Framework ....................................... 6
2.1. Link Level ............................................... 6
2.2. Commands and Responses ................................... 6
2.2.1. Client Protocol Sender and Server Protocol Receiver ...... 6
2.2.2. Server Protocol Sender and Client Protocol Receiver ...... 7
2.3. Server States ............................................ 8
2.3.1. Non-Authenticated State .................................. 8
2.3.2. Authenticated State ...................................... 8
2.3.3. Logout State ............................................. 8
2.4. Operational Considerations ............................... 9
2.4.1. Untagged Status Updates .................................. 9
2.4.2. Response when No Command in Progress ..................... 9
2.4.3. Auto-logout Timer ........................................ 9
2.4.4. Multiple Commands in Progress ............................ 10
2.5. Server Command Continuation Request ...................... 10
2.6. Data Formats ............................................. 10
2.6.1. Atom ..................................................... 11
2.6.2. Number ................................................... 11
2.6.3. String ................................................... 11
2.6.3.1. 8-bit and Binary Strings ................................. 12
2.6.4. Parenthesized List ....................................... 12
2.6.5. NIL ...................................................... 12
3. Protocol Elements ........................................ 12
3.1. Entries and Attributes ................................... 12
3.1.1. Predefined Attributes .................................... 13
3.1.2. Attribute metadata ....................................... 14
3.2. ACAP URL scheme .......................................... 15
3.2.1. ACAP URL User Name and Authentication Mechanism .......... 15
3.2.2. Relative ACAP URLs ....................................... 16
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3.3. Contexts ................................................. 16
3.4. Comparators .............................................. 17
3.5. Access Control Lists (ACLs) .............................. 18
3.6. Server Response Codes .................................... 20
4. Namespace Conventions .................................... 22
4.1. Dataset Namespace ........................................ 22
4.2. Attribute Namespace ...................................... 23
4.3. Formal Syntax for Dataset and Attribute Namespace ........ 23
5. Dataset Management ....................................... 25
5.1. Dataset Inheritance ...................................... 25
5.2. Dataset Attributes ....................................... 25
5.3. Dataset Creation ......................................... 26
5.4. Dataset Class Capabilities ............................... 26
5.5. Dataset Quotas ........................................... 27
6. Command and Response Specifications ...................... 28
6.1. Initial Connection ....................................... 29
6.1.1. ACAP Untagged Response ................................... 29
6.2. Any State ................................................ 30
6.2.1. NOOP Command ............................................. 30
6.2.2. LANG Command ............................................. 30
6.2.3. LANG Untagged Response ................................... 31
6.2.4. LOGOUT Command ........................................... 31
6.2.5. OK Response .............................................. 31
6.2.6. NO Response .............................................. 32
6.2.7. BAD Response ............................................. 32
6.2.8. BYE Untagged Response .................................... 33
6.2.9. ALERT Untagged Response .................................. 33
6.3. Non-Authenticated State .................................. 33
6.3.1. AUTHENTICATE Command ..................................... 34
6.4. Searching ................................................ 35
6.4.1. SEARCH Command ........................................... 35
6.4.2. ENTRY Intermediate Response .............................. 40
6.4.3. MODTIME Intermediate Response ............................ 40
6.4.4. REFER Intermediate Response .............................. 40
6.5. Contexts ................................................. 41
6.5.1. FREECONTEXT Command ...................................... 41
6.5.2. UPDATECONTEXT Command .................................... 41
6.5.3. ADDTO Untagged Response .................................. 42
6.5.4. REMOVEFROM Untagged Response ............................. 42
6.5.5. CHANGE Untagged Response ................................. 43
6.5.6. MODTIME Untagged Response ................................ 43
6.6. Dataset modification ..................................... 44
6.6.1. STORE Command ............................................ 44
6.6.2. DELETEDSINCE Command ..................................... 45
6.6.3. DELETED Intermediate Response ............................ 46
6.7. Access Control List Commands ............................. 46
6.7.1. SETACL Command ........................................... 46
6.7.2. DELETEACL Command ........................................ 47
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6.7.3. MYRIGHTS Command ......................................... 47
6.7.4. MYRIGHTS Intermediate Response ........................... 48
6.7.5. LISTRIGHTS Command ....................................... 48
6.7.6. LISTRIGHTS Intermediate Response ......................... 49
6.8. Quotas ................................................... 49
6.8.1. GETQUOTA Command ......................................... 49
6.8.3. QUOTA Untagged Response .................................. 50
6.9. Extensions ............................................... 50
7. Registration Procedures .................................. 50
7.1. Comparators .............................................. 51
7.2. ACAP Capabilities ........................................ 51
7.3. ACAP Response Codes ...................................... 52
7.4. Dataset Classes .......................................... 52
7.5. Vendor Subtree ........................................... 53
8. Formal Syntax ............................................ 53
9. Multi-lingual Considerations ............................. 63
10. Security Considerations .................................. 64
11. Acknowledgments .......................................... 64
12. Authors' Addresses ....................................... 64
Appendices ........................................................ 65
A. References ............................................... 65
B. ACAP Keyword Index ....................................... 67
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ACAP Protocol Specification
0. Changes from version -03 to version -04
1) Changed ABNF reference to use new ABNF spec, added UTF-8 syntax
and got rid of all <description> stuff in grammar.
2) Added length limit of 32 on tags.
3) Renamed "ordering function" to "comparator"
4) Put "" around comparator, made "+" / "-" optional.
5) Added SUBSTRING and PREFIX search keys.
6) Added multi-valued attributes.
7) Restricted numbers to 32-bit values.
8) Added description of data model and design goals.
9) Permit multiple referrals.
10) Simplified ACAP URL.
11) Noted that UNCHANGEDSINCE with a time of "00000101000000" will
always fail if the entry exists.
12) Used "base dataset" rather than "inherited dataset"
13) Fixed ABNF to group results for each RETURN item.
14) Forbid use of "*" or "%" in attribute name.
15) Added TRYCACHE response code.
16) Clarified that any two STORE operations must result in different
modtimes, even if simultaneous.
17) Added recommendation that all servers support the PLAIN SASL
mechanism and SHOULD support an encryption layer or stronger
standards track SASL mechanism.
18) Added a bunch of text to security considerations section after
being warned that the IESG is becoming much more stringent about
security considerations. Comments would be appreciated.
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19) Noted that change responses are not issued for implicit
renumbering.
20) Removed ".bin" attribute naming convention.
21) Removed partial fetch attribute.
22) Removed "o" ACL bit.
23) Added acl-object argument to PERMISSION error.
24) Atoms must begin with a letter to distinguish them from numbers.
Added that atoms are used for protocol keywords.
25) Make ALERT a separate untagged response
26) Change NOTIFYCONTEXT to MAKECONTEXT [ENUMERATE] [NOTIFY]
27) Added Multi-lingual considerations section
28) Updated STORE grammar to deal with multiple writable metadata
items and multi-valued attributes.
29) make metadata item names be quoted strings
30) Fixed LISTRIGHTS, SETACL examples.
31) Added dataset creation section, dataset capabilities section.
32) Added NOINHERIT SEARCH modifier.
33) Added NOEXIST response code and NOCREATE store modifier.
34) Added LANG command.
35) Added user specific and site specific attribute namespaces.
36) Removed SETQUOTA command, added description of /quota dataset
class. SETQUOTA was broken because it didn't fall under the auspices
of ACAP's ACL system.
37) Allow servers to implement schemes to defeat client polling with
UPDATECONTEXT.
38) Forbid duplicate search modifiers, store modifiers, store
entries, store entry attributes, store attribute metadata.
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0.1. Open Issues
1) Consider making ACL model more precise. Would like to pick AFS
semantics over POSIX semantics since AFS semantics are more
intuitive. Currently both ACL semantics are permitted.
2) Need more examples.
3) Descriptive comparator naming, including vendor naming.
1. Introduction
1.1. Conventions Used in this Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively. If such lines are wrapped without a new "C:" or
"S:" label, then the wrapping is for editorial clarity and is not
part of the command.
The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
and "MAY" in this document are to be interpreted as described in "Key
words for use in RFCs to Indicate Requirement Levels" [KEYWORDS].
1.2. ACAP Data Model
An ACAP server exports a hierarchical tree of entries. Each level of
the tree is called a dataset, and each dataset is made up of a list
of entries. Each entry has a unique name and may contain any number
of named attributes. Each attribute within an entry may be single
valued or multi-valued and may have associated metadata to assist
access and interpretation of the value.
The rules with which a client interprets the data within a portion of
ACAP's tree of entries are called a dataset class.
1.3. ACAP Design Goals
ACAP's primary purpose is to allow users access to their
configuration data from multiple network-connected computers. Users
can then sit down in front of any network-connected computer, run any
ACAP-enabled application and have access to their own configuration
data. Because it is hoped that many applications will become ACAP-
enabled, client simplicity was preferred to server or protocol
simplicity whenever reasonable.
ACAP is designed to be easily manageable. For this reason, it
includes "inheritance" which allows one dataset to inherit default
attributes from another dataset. In addition, access control lists
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are included to permit delegation of management and quotas are
included to prevent storage abuse. Finally, an ACAP server which is
conformant to this base specification should be able to support most
dataset classes defined in the future without requiring a server
reconfiguration or upgrade.
ACAP is designed to operate well with a client that only has
intermittent access to an ACAP server. For this reason, each entry
has a server maintained modification time so that the client may
detect changes. In addition, the client may ask the server for a
list of entries which have been removed since it last accessed the
server.
ACAP presumes that a dataset may be potentially large and/or the
client's network connection may be slow, and thus offers server
sorting, selective fetching and change notification for entries
within a dataset.
As required for most Internet protocols, security, scalability and
internationalization were important design goals.
Given these design goals, an attempt was made to keep ACAP as simple
as possible. It is a traditional Internet text based protocol which
massively simplifies protocol debugging. It was designed based on
the successful IMAP [IMAP4] protocol framework, with a few minor
simplifications.
1.4. Validation
By default, any value may be stored in any attribute for which the
user has appropriate permission and quota. This rule is necessary to
allow the addition of new simple dataset classes without
reconfiguring or upgrading the server.
In some cases, such as when the value has special meaning to the
server, it is useful to have the server enforce validation by
returning the INVALID response code to a STORE command. These cases
MUST be explicitly identified in the dataset class specification
which SHOULD include specific fixed rules for validation. Since a
given ACAP server may be unaware of any particular dataset class
specification, clients MUST NOT depend on the presence of enforced
validation on the server.
1.5. Definitions
access control list (ACL)
A set of identifier, rights pairs associated with an object. An
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ACL is used to determine which operations a user is permitted to
perform on that object. See section ###.
attribute
A named value within an entry. See section ###.
comparator
A named function which can be used to perform one or more of
three comparison operations: ordering, equality and substring
matching. See section ###.
context
An ordered subset of entries in a dataset, created by a SEARCH
command with a MAKECONTEXT modifier. See section ###.
dataset
One level of hierarchy in ACAP's tree of entries. See section
###.
dataset class specification
The rules which allow a client to interpret the data within a
portion of ACAP's tree of entries.
entry
A set of attributes with a unique entry name. See section ###.
metadata
Information describing an attribute, its value and any access
controls associated with that attribute. See section ###.
NIL This represents the non-existence of a particular data item.
NUL A control character encoded as 0 in US-ASCII [US-ASCII].
octet
An 8-bit value. On most modern computer systems, an octet is
one byte.
SASL Simple Authentication and Security Layer [SASL].
UTC Universal Coordinated Time as maintained by the Bureau
International des Poids et Mesures (BIPM).
UTF-8
An 8-bit transformation format of the Universal Character Set
[UTF8]. Note that an incompatible change was made to the coded
character set referenced by [UTF8], so for the purpose of this
document, UTF-8 refers to the UTF-8 encoding as defined by
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version 2.0 of Unicode [UNICODE-2], or ISO 10646 [ISO-10646]
including amendments one through seven.
1.6. ACAP Command Overview
The AUTHENTICATE, NOOP, LANG and LOGOUT commands provide basic
protocol services. The SEARCH command is used to select, sort, fetch
and monitor changes to attribute values and metadata. The
UPDATECONTEXT and FREECONTEXT commands are also used to assist in
monitoring changes in attribute values and metadata. The STORE
command is used to add, modify and delete entries and attributes.
The DELETEDSINCE command is used to assist a client in
re-synchronizing a cache with the server. The GETQUOTA, SETACL,
DELETEACL, LISTRIGHTS and MYRIGHTS commands are used to examine
storage quotas and examine or modify access permissions.
2. Protocol Framework
2.1. Link Level
The ACAP protocol assumes a reliable data stream such as provided by
TCP. When TCP is used, an ACAP server listens on port 674.
2.2. Commands and Responses
An ACAP session consists of the establishment of a client/server
connection, an initial greeting from the server, and client/server
interactions. These client/server interactions consist of a client
command, server data, and a server completion result.
All interactions transmitted by client and server are in the form of
lines; that is, strings that end with a CRLF. The protocol receiver
of an ACAP client or server is either reading a line, or is reading a
sequence of octets with a known count followed by a line. Both
clients and servers must be capable of handling lines of arbitrary
length.
2.2.1. Client Protocol Sender and Server Protocol Receiver
The client command begins an operation. Each client command is
prefixed with a identifier (an alphanumeric string of no more than 32
characters, e.g., A0001, A0002, etc.) called a "tag". A different
tag is generated by the client for each command.
There are two cases in which a line from the client does not
represent a complete command. In one case, a command argument is
quoted with an octet count (see the description of literal in section
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###); in the other case, the command arguments require server
feedback (see the AUTHENTICATE command). In some of these cases, the
server sends a command continuation request if it is ready for the
next part of the command. This response is prefixed with the token
"+".
Note: If, instead, the server detected an error in the
command, it sends a BAD completion response with tag
matching the command (as described below) to reject the
command and prevent the client from sending any more of the
command.
It is also possible for the server to send a completion or
intermediate response for some other command (if multiple
commands are in progress), or untagged data. In either
case, the command continuation request is still pending;
the client takes the appropriate action for the response,
and reads another response from the server.
The ACAP server reads a command line from the client, parses the
command and its arguments, and transmits server data and a server
command completion result.
2.2.2. Server Protocol Sender and Client Protocol Receiver
Data transmitted by the server to the client come in four forms:
command continuation requests, command completion results,
intermediate responses, and untagged responses.
A command continuation request is prefixed with the token "+".
A command completion result indicates the success or failure of the
operation. It is tagged with the same tag as the client command
which began the operation. Thus, if more than one command is in
progress, the tag in a server completion response identifies the
command to which the response applies. There are three possible
server completion responses: OK (indicating success), NO (indicating
failure), or BAD (indicating protocol error such as unrecognized
command or command syntax error).
An intermediate response returns data which can only be interpreted
within the context of a command in progress. It is tagged with the
same tag as the client command which began the operation. Thus, if
more than one command is in progress, the tag in an intermediate
response identifies the command to which the response applies. A
tagged response other than "OK", "NO", or "BAD" is an intermediate
response.
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An untagged response returns data or status messages which may be
interpreted outside the context of a command in progress. It is
prefixed with the token "*". Untagged data may be sent as a result
of a client command, or may be sent unilaterally by the server.
There is no syntactic difference between untagged data that resulted
from a specific command and untagged data that were sent
unilaterally.
The protocol receiver of an ACAP client reads a response line from
the server. It then takes action on the response based upon the
first token of the response, which may be a tag, a "*", or a "+" as
described above.
A client MUST be prepared to accept any server response at all times.
This includes untagged data that it may not have requested.
This topic is discussed in greater detail in the Server Responses
section.
2.3. Server States
An ACAP server is in one of three states. Most commands are valid in
only certain states. It is a protocol error for the client to
attempt a command while the server is in an inappropriate state for
that command. In this case, a server will respond with a BAD command
completion result.
2.3.1. Non-Authenticated State
In non-authenticated state, the user must supply authentication
credentials before most commands will be permitted. This state is
entered when a connection starts.
2.3.2. Authenticated State
In authenticated state, the user is authenticated and most commands
will be permitted. This state is entered when acceptable
authentication credentials have been provided.
2.3.3. Logout State
In logout state, the session is being terminated, and the server will
close the connection. This state can be entered as a result of a
client request or by unilateral server decision.
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+--------------------------------------+
|initial connection and server greeting|
+--------------------------------------+
|| (1) || (2)
VV ||
+-----------------+ ||
|non-authenticated| ||
+-----------------+ ||
|| (4) || (3) ||
|| VV ||
|| +----------------+ ||
|| | authenticated | ||
|| +----------------+ ||
|| || (4) ||
VV VV VV
+--------------------------------------+
| logout and close connection |
+--------------------------------------+
(1) connection (ACAP greeting)
(2) rejected connection (BYE greeting)
(3) successful AUTHENTICATE command
(4) LOGOUT command, server shutdown, or connection closed
2.4. Operational Considerations
2.4.1. Untagged Status Updates
At any time, a server can send data that the client did not request.
2.4.2. Response when No Command in Progress
Server implementations are permitted to send an untagged response
while there is no command in progress. Server implementations that
send such responses MUST deal with flow control considerations.
Specifically, they must either (1) verify that the size of the data
does not exceed the underlying transport's available window size, or
(2) use non-blocking writes.
2.4.3. Auto-logout Timer
If a server has an inactivity auto-logout timer, that timer MUST be
of at least 30 minutes duration. The receipt of ANY command from the
client during that interval MUST suffice to reset the auto-logout
timer.
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2.4.4. Multiple Commands in Progress
The client is not required to wait for the completion result of a
command before sending another command, subject to flow control
constraints on the underlying data stream. Similarly, a server is
not required to process a command to completion before beginning
processing of the next command, unless an ambiguity would result
because of a command that would affect the results of other commands.
If there is such an ambiguity, the server executes commands to
completion in the order given by the client.
2.5. Server Command Continuation Request
The command continuation request is indicated by a "+" token instead
of a tag. This indicates that the server is ready to accept the
continuation of a command from the client.
This response is used in the AUTHENTICATE command to transmit server
data to the client, and request additional client data. This
response is also used if an argument to any command is a
synchronizing literal.
The client is not permitted to send the octets of a synchronizing
literal unless the server indicates that it expects it. This permits
the server to process commands and reject errors on a line-by-line
basis, assuming it checks for non-synchronizing literals at the end
of each line. The remainder of the command, including the CRLF that
terminates a command, follows the octets of the literal. If there
are any additional command arguments the literal octets are followed
by a space and those arguments.
Example: C: A099 FREECONTEXT {10}
S: + "Ready for additional command text"
C: FRED
C: FOOB
S: A099 OK "FREECONTEXT completed"
C: A044 BLURDYBLOOP {102856}
S: A044 BAD "No such command as 'BLURDYBLOOP'"
2.6. Data Formats
ACAP uses textual commands and responses. Data in ACAP can be in one
of five forms: atom, number, string, parenthesized list or NIL.
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2.6.1. Atom
An atom consists of one to 1024 non-special characters. It must
begin with a letter. Atoms are used for protocol keywords.
2.6.2. Number
A number consists of one or more digit characters, and represents a
numeric value. Numbers are restricted to the range of an unsigned
32-bit integer: 0 < number < 4,294,967,296.
2.6.3. String
A string is in one of two forms: literal and quoted string. The
literal form is the general form of string. The quoted string form
is an alternative that avoids the overhead of processing a literal at
the cost of restrictions of what may be in a quoted string.
A literal is a sequence of zero or more octets (including CR and LF),
prefix-quoted with an octet count in the form of an open brace ("{"),
the number of octets, close brace ("}"), and CRLF. In the case of
literals transmitted from server to client, the CRLF is immediately
followed by the octet data.
There are two forms of literals transmitted from client to server.
The form where the open brace ("{") and number of octets is
immediately followed by a close brace ("}") and CRLF is called a
synchronizing literal. When sending a synchronizing literal, the
client must wait to receive a command continuation request (described
later in this document) before sending the octet data (and the
remainder of the command). The other form of literal, the
non-synchronizing literal, is used to transmit a string from client
to server without waiting for a command continuation request. The
non-synchronizing literal differs from the synchronizing literal by
having a plus ("+") between the number of octets and the close brace
("}") and by having the octet data immediately following the CRLF.
A quoted string is a sequence of zero to 1024 octets excluding NUL,
CR and LF, with double quote (<">) characters at each end.
The empty string is represented as "" (a quoted string with zero
characters between double quotes), as {0} followed by CRLF (a
synchronizing literal with an octet count of 0), or as {0+} followed
by a CRLF (a non-synchronizing literal with an octet count of 0).
Note: Even if the octet count is 0, a client transmitting a
synchronizing literal must wait to receive a command
continuation request.
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2.6.3.1. 8-bit and Binary Strings
Most strings in ACAP are restricted to UTF-8 characters and may not
contain NUL octets. Attribute values MAY contain any octets
including NUL.
2.6.4. Parenthesized List
Data structures are represented as a "parenthesized list"; a sequence
of data items, delimited by space, and bounded at each end by
parentheses. A parenthesized list can contain other parenthesized
lists, using multiple levels of parentheses to indicate nesting.
The empty list is represented as () -- a parenthesized list with no
members.
2.6.5. NIL
The special atom "NIL" represents the non-existence of a particular
data item that is represented as a string or parenthesized list, as
distinct from the empty string "" or the empty parenthesized list ().
3. Protocol Elements
This section defines data formats and other protocol elements used
throughout the ACAP protocol.
3.1. Entries and Attributes
Within a dataset, each entry name is made up of zero or more UTF-8
characters other than slash ("/"). A slash separated list of
entries, one at each level of the hierarchy, forms the full path to
an entry.
Each entry is made up of a set of attributes. Each attribute has a
hierarchical name in UTF-8, with each component of the name separated
by a period (".").
The value of an attribute is either single or multi-valued. A single
value is NIL (has no value), or a string of zero or more octets. A
multi-value is a list of zero or more strings, each of zero or more
octets.
Attribute names are not permitted to contain asterisk ("*") or
percent ("%") and MUST be valid UTF-8 strings which do not contain
NUL. Invalid attribute names result in a BAD response. Entry names
are not permitted to begin with "." or contain slash ("/") and MUST
be valid UTF-8 strings which do not contain NUL. Invalid entry names
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in the entry field of a command result in a BAD response.
Use of non-visible UTF-8 characters in attribute and entry names is
discouraged.
3.1.1. Predefined Attributes
Attribute names which do not contain a dot (".") are reserved for
standardized attributes which have meaning in any dataset. The
following attributes are defined by the ACAP protocol.
entry
Contains the name of the entry. MUST be single valued.
Attempts to use illegal or multi-valued values for the entry
attribute are protocol errors and MUST result in a BAD
completion response. This is a special case.
modtime
Contains the date and time any read-write metadata in the entry
was last modified. This value MUST be in UTC, MUST be
automatically updated by the server.
The value consists of 14 or more US-ASCII digits. The first
four indicate the year, the next two indicate the month, the
next two indicate the day of month, the next two indicate the
hour (0 - 23), the next two indicate the minute, and the next
two indicate the second. Any further digits indicate fractions
of a second.
The time, particularly fractions of a second, need not be
accurate. It is REQUIRED, however, that any two entries in a
dataset changed by successive modifications have strictly
ascending modtime values. In addition, each STORE command
within a dataset (including simultaneous stores from different
connections) MUST use different modtime values.
This attribute has enforced validation, so any attempt to STORE
a value in this attribute MUST result in a NO response with an
INVALID response code.
subdataset
If this attribute is set, it indicates the existence of a sub-
dataset of this entry.
The value consists of a list of relative ACAP URLs (see section
###) which may be used to locate the sub-dataset. The base URL
is the full path to the entry followed by a slash ("/"). The
value "." indicates a subdataset is located directly under this
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one. Multiple values indicate replicated copies of the
subdataset.
For example, if the dataset "/folder/site/" has an entry
"public-folder" with a subdataset attribute of ".", then there
exists a dataset "/folder/site/public-folder/". If the value of
the subdataset attribute was instead
"//other.acap.domain//folder/site/public-folder/" that would
indicate the dataset is actually located on a different ACAP
server.
A dataset can be created by storing a "subdataset" attribute
including ".", and a sub-hierarchy of datasets is deleted by
storing a NIL value to the "subdataset" attribute on the entry
in the parent dataset.
This attribute has enforced syntax validation. Specifically, if
an attempt is made to STORE a single-value (other than NIL), an
empty list, or one of the values does not follow the URL syntax
rules [BASIC-URL], then this will result in a NO response with
an INVALID response code.
3.1.2. Attribute metadata
Each attribute is made up of metadata items which describe that
attribute, its value and any associated access controls. Metadata
items may be either read-only in which case the client is never
permitted to modify the item, or read-write, in which case the client
may modify the item if the access control list (ACL) permits.
The following metadata items are defined in this specification:
acl The access control list for the attribute, if one exists. If
the attribute does not have an ACL, NIL is returned.
Read-write. See section ### for the contents of an ACL.
attribute
The attribute name. Read-only.
myrights
The set of rights that the client has to the attribute.
Read-only. See section ### for the possible rights.
size This is the length of the value. In the case of a
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multi-value, this is a list of lengths for each of the values.
value The value. For a multi-value, this is a list of single
values.
Additional items of metadata may be defined in extensions to this
protocol. Servers MUST respond to queries of unrecognized metadata
by returning a BAD command completion result.
3.2. ACAP URL scheme
ACAP URLs are used within the ACAP protocol for the "subdataset"
attribute, referrals and inheritance. They provide a convenient
syntax for referring to other ACAP datasets. The ACAP URL follows
the common Internet scheme syntax as defined in [BASIC-URL]. If
:<port> is omitted, the port defaults to 674.
An ACAP URL has the following general form:
url-acap = "acap://" url-server "/" url-enc-entry [url-filter]
The <url-server> element includes the hostname, and optional user
name, authentication mechanism and port number. The <url-enc-entry>
element contains the name of an entry path encoded according to the
rules in [BASIC-URL].
The <url-filter> element is an optional list of interesting attribute
names. If omitted, the URL refers to all attributes of the named
entry.
Note that unsafe or reserved characters such as " " or "?" MUST be
hex encoded as described in the URL specification [BASIC-URL]. Hex
encoded octets are interpreted according to UTF-8 [UTF8].
3.2.1. ACAP URL User Name and Authentication Mechanism
A user name and/or authentication mechanism may be supplied. They
are used in the "AUTHENTICATE" command after making the connection to
the ACAP server. If no user name or authentication mechanism is
supplied, then the SASL ANONYMOUS [SASL-ANON] mechanism is used by
default. If the URL supplies just a user name, the program
interpreting the ACAP URL SHOULD request a password from the user if
necessary.
An authentication mechanism can be expressed by adding
";AUTH=<enc_auth_type>" to the end of the user name. When such an
<enc_auth_type> is indicated, the client SHOULD request appropriate
credentials from that mechanism and use the "AUTHENTICATE" command.
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If no user name is specified, one SHOULD be obtained from the
mechanism or requested from the user as appropriate.
The string ";AUTH=*" indicates that the client SHOULD select an
appropriate authentication mechanism. It MAY use any mechanism
listed in the initial ACAP response. If no user name is specified
and no appropriate authentication mechanisms are available, the
client SHOULD fall back to anonymous login as described above. This
allows a URL which grants read-write access to authorized users, and
read-only anonymous access to other users.
Note that if unsafe or reserved characters such as " " or ";" are
present in the user name or authentication mechanism, they MUST be
encoded as described in the URL specification [BASIC-URL].
3.2.2. Relative ACAP URLs
Because ACAP uses "/" as the hierarchy separator for dataset paths,
it works well with the relative URL rules defined in the relative URL
specification [REL-URL].
The <aauth> grammar element is considered part of the user name for
purposes of resolving relative ACAP URLs.
The base URL for a relative URL stored in an attribute's value is
formed by taking the path to the dataset containing that attribute,
appending a "/" followed by the entry name of the entry containing
that attribute followed by "/".
3.3. Contexts
A context is subset of entries in a dataset or datasets, created by a
SEARCH command with a MAKECONTEXT modifier. Context names are
client-generated strings and must not start with the slash ('/')
character.
When a client creates a context, it may request automatic
notification of changes. A client may also request enumeration of
entries within a context. Enumeration simplifies the implementation
of a "virtual scrollbar" by the client.
A context exists only within the ACAP session it was created. When
the connection is closed, all contexts associated with that
connection are automatically discarded. A server is required to
support at least 100 active contexts within a session. If the server
supports a larger limit it must advertise it in a CONTEXTLIMIT
capability.
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3.4. Comparators
A comparator is a named function which takes two input values and can
be used to perform one or more of three comparison operations:
ordering, equality and substring matching.
The ordering operation is used both for the SORT search modifier and
the COMPARE and COMPARESTRICT search keys. Ordering comparators can
determine the ordinal precedence of any two values. When used for
ordering, a comparator's name can be prefixed with "+" or "-" to
indicate that the ordering should be normal order or reversed order
respectively. If no prefix is included, "+" is assumed.
For the purpose of ordering, a comparator may designate certain
values as having an undefined ordinal precedence. Such values always
collate with equal value after all other values regardless of whether
normal or reversed ordering is used. Unless the comparator
definition specifies otherwise, multi-values and NIL values have an
undefined ordinal precedence.
The equality operation is used for the EQUAL search modifier, and
simply determines if the two values are considered equal under the
comparator function. When comparing a single value to a multi-value,
the two are considered equal if any one of the multiple values is
equal to the single value.
The substring match operation is used for the PREFIX and SUBSTRING
search modifiers, and simply determines if search value is a prefix
or a substring of the item being searched. In the case of substring
search on a multi-valued attribute, the match is successful if the
value is a prefix or substring of any one of the multiple values.
Additional comparators may be registered with the Internet Assigned
Number Authority (IANA) according to the rules in section ###.
Servers MUST respond to unknown or improperly used comparators with a
BAD command completion result.
The following comparators are defined by this standard:
octet
Operations: Ordering, Equality, Substring match
For collation, the octet comparator interprets the value of
an attribute as a series of unsigned octets with ordinal
values from 0 to 255. When ordering two strings, each octet
pair is compared in sequence until the octets are unequal or
the end of the string is reached. When collating two strings
where the shorter is a prefix of the longer, the shorter
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string is interpreted as having a smaller ordinal value. The
"octet" or "+octet" forms collate smaller ordinal values
earlier, and the "-octet" form collates larger ordinal values
earlier.
For the equality function, two strings are equal if they are
the same length and contain the same octets in the same
order. NIL is equal only to itself.
For non-binary, non-nil single values, octet ordering is
equivalent to the ANSI C [ISO-C] strcmp() function applied to
C string representations of the values. For non-binary,
non-nil single values, octet substring match is equivalent to
the ANSI C strstr() function applied to the C string
representations of the values.
en-nocase
Operations: Ordering, Equality, Substring match
The en-nocase comparator first applies a mapping to the
attribute values which translates all US-ASCII letters to
uppercase (octet values 0x61 to 0x7A are translated to octet
values 0x41 to 0x5A respectively), then applies the octet
comparator as described above. With this function the values
"hello" and "HELLO" have the same ordinal value and are
considered equal.
numeric
Operations: Ordering, Equality
The numeric comparator interprets strings as decimal positive
integers represented as US-ASCII digits. All values which do
not begin with a US-ASCII digit are considered equal with an
ordinal value higher than all non-NIL single-valued
attributes. Otherwise, all US-ASCII digits (octet values
0x30 to 0x39) are interpreted starting from the beginning of
the string to the first non-digit or the end of the string.
3.5. Access Control Lists (ACLs)
An access control list is a set of identifier,rights pairs used to
restrict access to a given dataset, attribute or attribute within an
entry. An ACL is represented by a multi-value with each value
containing the identifier followed by a tab character followed by the
rights. The syntax is defined by the "acl" rule in the formal syntax
in section ###.
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Identifier is a UTF-8 string. The identifier "anyone" is reserved to
refer to the universal identity (all authentications, including
anonymous). All user name strings accepted by the AUTHENTICATE
command to authenticate to the ACAP server are reserved as
identifiers for the corresponding user. Identifiers starting with a
dash ("-") are reserved for "negative rights", described below. All
other identifier strings have implementation-defined meanings.
Rights is a string listing a (possibly empty) set of alphanumeric
characters, each character listing a set of operations which is being
controlled. Letters are reserved for "standard" rights, listed
below. The set of standard rights may only be extended by a
standards-track or IESG approved experimental RFC. Digits are
reserved for implementation or site defined rights. The currently
defined standard rights are:
r - read
w - write
i - insert (perform store on a previously NIL value)
a - administer (perform store on ACL attribute/metadata)
An implementation may force rights to always or never be granted. In
particular, implementations are expected to grant implicit read and
administer rights to a user's personal dataset storage in order to
avoid denial of service problems. Rights are never tied, unlike the
IMAP ACL extension [IMAP-ACL].
It is possible for multiple identifiers in an access control list to
apply to a given user (or other authentication identity). For
example, an ACL may include rights to be granted to the identifier
matching the user, one or more implementation-defined identifiers
matching groups which include the user, and/or the identifier
"anyone". How these rights are combined to determine the user's
access is implementation-defined. An implementation may choose, for
example, to use the union of the rights granted to the applicable
identifiers. An implementation may instead choose, for example, to
only use those rights granted to the most specific identifier present
in the ACL. A client may determine the set of rights granted to the
logged-in user for a given mailbox by using the MYRIGHTS command.
When an identifier in an ACL starts with a dash ("-"), that indicates
that associated rights are to be removed from the identifier that is
prefixed by the dash. For example, if the identifier "-fred" is
granted the "w" right, that indicates that the "w" right is to be
removed from users matching the identifier "fred". Implementations
need not support having identifiers which start with a dash in ACLs.
Each attribute of each entry of a dataset may potentially have an
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ACL. If an attribute in an entry does not have an ACL, then access
is controlled by a default ACL for that attribute in the dataset, if
it exists. If there is no default ACL for that attribute in the
dataset, access is controlled by a default ACL for that dataset. The
default ACL for a dataset must exist.
In order to perform any access or manipulation on an entry in a
dataset, the client must have 'r' rights on the "entry" attribute of
the entry. Implementations should take care not to reveal via error
messages the existence of an entry for which the client does not have
attribute of the parent dataset in order to access the contents of a
dataset.
Many of the ACL commands and responses include an "acl object"
parameter, for specifying what the ACL applies to. This is a
parenthesized list. The list contains just the dataset name when
referring to the default ACL for a dataset. The list contains a
dataset name and an attribute name when referring to the default ACL
for an attribute in a dataset. The list contains a dataset name, an
attribute name, and an entry name when referring to the ACL for an
attribute of an entry of a dataset.
3.6. Server Response Codes
An OK, NO, BAD, ALERT or BYE response from the server MAY contain a
response code to describe the event in a more detailed machine
parsable fashion. A response code consists of data inside
parentheses in the form of an atom, possibly followed by a space and
arguments. Response codes are defined when there is a specific
action that a client can take based upon the additional information.
The currently defined response codes are:
ENCRYPT-NEEDED
This response code is returned on a tagged NO result from an
AUTHENTICATE command. It indicates that site security policy
requires the use of a strong encryption mechanism for the
specified authentication identity.
INVALID
This response code indicates that a STORE command included
data which the server implementation does not permit. It
MUST NOT be used unless the dataset class specification for
the attribute in question explicitly permits enforced server
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validation. The argument is the attribute which was invalid.
MODIFIED
This response code indicates that a conditional store failed
because the modtime on the entry is later than the modtime
specified with the STORE command UNCHANGEDSINCE modifier.
The argument is the entry which had been modified.
NOEXIST
This response code indicates that a search or NOCREATE store
failed because a specified dataset did not exist. The
argument is the dataset which does not exist.
PERMISSION
A command failed due to insufficient permission based on the
access control list or implicit rights. The argument is the
acl-object which caused the permission failure.
PLAINTEXT-DENIED
This response code is returned on a tagged NO result from an
AUTHENTICATE PLAIN command. It indicates that site security
policy forbids the use of plain text passwords for the
specified authentication identity.
QUOTA
A STORE command which would have increased the size of the
dataset failed due to insufficient quota.
REFER
This response code may be returned in a tagged NO response to
any command that takes a dataset name as a parameter. It has
one or more arguments with the syntax of relative URLs. It
is a referral, indicating that the command should be retried
using one of the relative URLs.
TOOMANY
This response code may be returned in a tagged OK response to
a SEARCH command which includes the LIMIT modifier. The
argument returns the total number of matching entries.
TRANSITION-NEEDED
This response code occurs on a NO response to an AUTHENTICATE
command with a mechanism other than PLAIN or ANONYMOUS. It
indicates that the PLAIN SASL [SASL-PLAIN] mechanism is
needed prior to using the stronger mechanism requested.
TRYCACHE
A STORE or SETACL command failed due to a temporary server
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failure. If the client caches the command, it may succeed
during a later cache replay.
TRYFREECONTEXT
This response code may be returned in a tagged NO response to
a SEARCH command which includes the MAKECONTEXT modifier. It
indicates that a new context may not be created due to the
server's limit on the number of existing contexts.
WAYTOOMANY
This response code may be returned in a tagged NO response to
a SEARCH command which includes a HARDLIMIT search modifier.
It indicates that the SEARCH would have returned more entries
than the HARDLIMIT permitted.
Additional response codes MUST be registered with IANA according
to the proceedures in section ###. Client implementations MUST
ignore response codes that they do not recognize.
4. Namespace Conventions
4.1. Dataset Namespace
The dataset namespace is a slash-separated hierarchy. The first
component of the dataset namespace is a dataset class. Dataset
classes MUST have a vendor prefix (vendor.<vendor/product>) or be
standards track or IESG approved experimental RFCs. See section ###
for the registration template.
The second component of the dataset name is "site", "group", "host",
or "user" referring to server-wide data, administrative group data,
per-host data and per-user data respectively.
For "group", "host", and "user" areas, the third component of the
path is the group name, the fully qualified host domain name, or the
user name. A path of the form "/<dataset-class>/~/" is a convenient
abbreviation for "/<dataset-class>/user/<current-user>/".
Dataset names which begin with "/byowner/" are reserved as an
alternate view of the namespace. This provides a way to see all the
dataset classes which a particular owner uses. For example,
"/byowner/~/<dataset-class>/" is an alternate name for "/<dataset-
class>/~/". Byowner provides a way to view a list of dataset classes
owned by a given user; this is done using the dataset
"/byowner/user/<current-user>/" with the NOINHERIT SEARCH modifier.
The dataset "/" may be used to find all dataset classes visible to
the current user. A dataset of the form "/<dataset-class>/user/" may
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be used to find all users which have made a dataset or entry of that
class visible to the current user.
The formal syntax for a dataset name is defined by the "dataset-name"
terminal in section ###.
4.2. Attribute Namespace
Attribute names which do not contain a dot (".") are reserved for
standardized attributes which have meaning in any dataset. In order
to simplify implementations, the attribute namespace is intended to
be unique across all datasets. To achieve this, attribute names are
prefixed with the dataset class name followed by a dot (".").
Attributes which effect management of the dataset are prefixed with
"dataset.". In addition, a subtree of the "vendor." attribute
namespace may be registered with IANA according to the rules in
section ###. ACAP implementors are encouraged to help define
interoperable dataset classes specifications rather than using the
private attribute namespace.
Finally, the "user.<user-name>." and "site." subtrees of the
attribute namespace are reserved for user-specific and site-specific
attributes respectively. Such attributes are not interoperable so
are discouraged in favor of defining standard attributes. A future
extension is expected to permit discovery of syntax for user or
site-specific attributes. Clients wishing to support display of user
or site-specific attributes should display the value of any non-NIL
single-valued "user.<user-name>." or "site." attribute which has
valid UTF-8 syntax.
The formal syntax for an attribute name is defined by the
"attribute-name" terminal in the next section.
4.3. Formal Syntax for Dataset and Attribute Namespace
The naming conventions for datasets and attributes are defined by the
following ABNF. Note that this grammar is not part of the ACAP
protocol syntax in section ###, as dataset names and attribute names
are encoded as strings within the ACAP protocol.
attribute-dacl = "dataset.acl" *("." name-component)
attribute-dset = dataset-std 1*("." name-component)
;; MUST be defined in a dataset class specification
attribute-name = attribute-std / attr-site / attr-user / vendor-name
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attribute-std = "entry" / "subdataset" / "modtime" / "dataset.inherit"
/ attribute-dacl / attribute-dset
attr-site = "site" 1*("." name-component)
attr-user = "user." name-component 1*("." name-component)
byowner = "/byowner/" owner "/" [dataset-class "/" dataset-sub]
dataset-class = dataset-std / vendor-name
dataset-normal = "/" [dataset-class "/" (owner-prefix / dataset-tail)]
dataset-name = byowner / dataset-normal
dataset-std = name-component
;; MUST be registered with IANA and the spec MUST
;; be published as a standards track or
;; IESG-approved experimental RFC
dataset-sub = *(dname-component "/")
;; The rules for this portion of the namespace may
;; be further restricted by the dataset class
;; specification.
dataset-tail = owner "/" dataset-sub
dname-component = 1*UTF8-CHAR
;; MUST NOT begin with "." or contain "/"
name-component = 1*UTF8-CHAR
;; MUST NOT contain ".", "/", "%", or "*"
owner = "site" / owner-host / owner-group / owner-user / "~"
owner-group = "group/" dname-component
owner-host = "host/" dname-component
owner-prefix = "group/" / "host/" / "user/"
owner-user = "user/" dname-component
vendor-name = vendor-token *("." name-component)
vendor-token = "vendor." name-component
;; MUST be registered with IANA
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5. Dataset Management
The entry with an empty name ("") in the dataset is used to hold
management information for the dataset as a whole.
5.1. Dataset Inheritance
It is possible for one dataset to inherit data from another. The
dataset from which the data is inherited is called the base dataset.
Data in the base dataset appears in the inheriting dataset, except
where overridden by data in the inheriting dataset.
The base dataset is usually a system-wide or group-wide set of
defaults. A system-wide dataset usually has one inheriting dataset
per user, allowing each user to add to or modify the defaults as
appropriate.
An entry which exists in both the inheriting and inherited dataset
has a modtime equal to the greater of the modtimes for the purposes
of a SEARCH command and context notification. Inheritance has no
effect on the STORE command, except that if NIL is stored to an
attribute and there is a default value in a base dataset, then an
ENTRY response is returned to notify the client of the change.
The "subdataset" attribute is not directly inherited. If the base
dataset includes a "subdataset" attribute and the inheriting dataset
does not, then the "subdataset" attribute will inherit a virtual
value of a list containing a ".". The subdataset at that node is
said to be a "virtual" dataset as it is simply a virtual copy of the
appropriate base dataset with all "subdataset" attributes changed to
a list containing a ".". A virtual dataset is not visible if
NOINHERIT is specified on the SEARCH command.
Servers MUST support at least two levels of inheritance. This
permits a user's dataset such as "/options/user/fred/common" to
inherit from a group dataset such as "/options/group/dinosaur
operators/common" which in turn inherits from a server-wide dataset
such as "/options/site/common".
5.2. Dataset Attributes
The following attributes apply to management of the dataset when
stored in the "" entry of a dataset. These attributes are not
inherited.
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dataset.acl
This holds the default access control list for the dataset. It
can not be modified by the STORE command, only by the SETACL and
DELETEACL commands.
dataset.acl.<attribute>
This holds the default access control list for an attribute
within the dataset. It can not be modified by the STORE command,
only by the SETACL and DELETEACL commands.
dataset.inherit
This holds the name of a dataset to inherit according to the
rules in section ###. This attribute may refer to a non-
existent dataset, in which case nothing is inherited.
5.3. Dataset Creation
When a dataset is first created (by storing a "." in the subdataset
attribute or storing an entry in a previously non-existent dataset),
the dataset attributes are initialized with the values from the
parent dataset in the "/byowner/" hierarchy. In the case of the
"dataset.inherit" attribute, the appropriate hierarchy component is
added. For example, given the following entry:
entry path "/byowner/user/joe/"
dataset.acl ("joe" "rwia")
dataset.inherit "/byowner/site"
If a new dataset class "/byowner/~/new" is created, it will have the
following dataset attributes:
entry path "/byowner/user/joe/new/"
dataset.acl ("joe" "rwia")
dataset.inherit "/byowner/site/new"
Note that the dataset "/byowner/user/joe/new/" is equivalent to
"/new/user/joe/".
5.4. Dataset Class Capabilities
Certain dataset classes or dataset class features may only be useful
if there is an active updating client or integrated server support
for the feature. The dataset class "capability" is reserved to allow
clients or servers to advertise such features. The "entry" attribute
within this dataset class is the name of the dataset class whose
features are being described. The attributes are prefixed with
"capability.<dataset-class>." and are defined by the appropriate
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dataset class specification.
Since it is possible for an unprivileged user to run an active client
for himself, a per-user capability dataset is useful. The dataset
"/capability/~/" holds information about all features available to
the user (via inheritance), and the dataset "/capability/site/" holds
information about all features supported by the site.
5.5. Dataset Quotas
The dataset class "quota" is reserved for quota management. Each
node of the "/byowner" view of the ACAP namespace MAY have an
associated entry in the quota dataset class. A quota root is a quota
limit and usage listed in the "quota" dataset class which applies to
a sub-tree of the ACAP "/byowner" name-space exempting all parts of
that sub-tree with their own quota root.
A quota limit specifies the total number of bytes a sub-tree of the
ACAP name-space may consume exempting all parts of that sub-tree with
their own quota roots. The actual number of bytes which a dataset or
entry consumes is implementation dependent. However two rules are
necessary to promote interoperability:
1) Removing an entry or dataset MUST reduce the quota usage.
2) A STORE command MUST NOT fail with a quota error if for all entry
modifications under a given quota root the sum of the lengths of the
attribute names and values is less then the quota limit minus the
quota usage. For some implementations, it MAY be necessary to allow
the quota usage to exceed the quota limit in order to satisfy this
rule. Note that a STORE command MAY succeed even if there does not
appear to be enough space.
The algorithm for locating a quota root for a dataset is as follows.
First, if the dataset name does not begin with "/byowner", then the
name is mapped appropriately. Second, the "/byowner" is replaced
with "/quota". Third, any trailing "/" is removed. If the resulting
entry-path contains a "quota.limit" attribute, that is the quota
root. Otherwise, the last component of the entry path is removed,
and the previous step is repeated. The GETQUOTA command implements
this algorithm in order to simplify ACAP clients.
The quota dataset class itself is exempt from quota management. ACAP
implementations SHOULD apply a very restrictive default ACL to quota
datasets.
The creation of a new quota root SHOULD NOT be automatically linked
to the creation of a dataset. Quota roots MAY be completely
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independent, or MAY reduce the limit of their parent quota root on
creation. Quota roots SHOULD NOT be nested -- modifying data should
only effect the usage within one quota root. When a quota limit is
removed (by storing NIL in quota.limit), its usage is added to the
parent quota root, and its limit MAY be added to the parent quota
root.
The following attributes are defined within the quota dataset class:
quota.limit
This is single-valued. The syntax for this value follows the
"number" rule defined below. This represents the quota limit,
in bytes, as defined in section ###.
quota.usage
This is single-valued. The syntax for this value follows the
"number" rule defined below. This is the quota usage in bytes.
It MAY be greater than the quota limit.
Because it can require excessive computation for some
implementations, ACAP servers MAY respond with NO to a SEARCH command
requesting context notification for the quota.usage attribute.
6. Command and Response Specifications
ACAP commands and responses are described in this section. Commands
are organized first by the state in which the command is permitted,
then by a general category of command type.
Command arguments, identified by "Arguments:" in the command
descriptions below, are described by function, not by syntax. The
precise syntax of command arguments is described in the Formal Syntax
section.
Some commands cause specific server data to be returned; these are
identified by "Data:" in the command descriptions below. See the
response descriptions in the Responses section for information on
these responses, and the Formal Syntax section for the precise syntax
of these responses. It is possible for server data to be transmitted
as a result of any command; thus, commands that do not specifically
require server data specify "no specific data for this command"
instead of "none".
The "Result:" in the command description refers to the possible
tagged status responses to a command, and any special interpretation
of these status responses.
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6.1. Initial Connection
Upon session startup, the server sends one of two untagged responses:
ACAP or BYE. The untagged BYE response is described in section ###.
6.1.1. ACAP Untagged Response
Data: capability list
The untagged ACAP response indicates the session is ready to
accept commands and contains a space-separated listing of
capabilities that the server supports. Each capability is
represented by a list containing the capability name optionally
followed by capability specific string arguments.
ACAP capability names MUST be defined in a standards track or IESG
approved experimental RFC and registered with IANA according to
the rules in section ###.
Client implementations SHOULD NOT require any capability name, and
MUST ignore any unknown capability names.
The following initial capabilities are defined:
COMPARATORS
The COMPARATORS capability includes a list of the comparator
functions which the server supports. See section ### for a
description of comparators.
CONTEXTLIMIT
The CONTEXTLIMIT capability has one argument which is a
number describing the maximum number of contexts the server
supports per connection. The number 0 indicates the server
has no limit, otherwise this number MUST be greater than
100.
IMPLEMENTATION
The IMPLEMENTATION capability has one argument which is a
string describing the server implementation. ACAP clients
MUST NOT alter their behavior based on this value. It is
intended primarily for debugging purposes.
SASL The SASL capability includes a list of the authentication
mechanisms supported by the server. See section ###.
Example: S: * ACAP (IMPLEMENTATION "ACME v3.5")
(SASL "CRAM-MD5" "PLAIN") (CONTEXTLIMIT "200")
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6.2. Any State
The following commands and responses are valid in any state.
6.2.1. NOOP Command
Arguments: none
Data: no specific data for this command (but see below)
Result: OK - noop completed
BAD - command unknown or arguments invalid
The NOOP command always succeeds. It does nothing. It can be
used to reset any inactivity auto-logout timer on the server.
Example: C: a002 NOOP
S: a002 OK "NOOP completed"
6.2.2. LANG Command
Arguments: optional list of language preferences
Data: untagged response: LANG
Result: OK - lang completed
NO - no matching language available
BAD - command unknown or arguments invalid
The LANG command with no arguments generates an untagged LANG
response including a list of languages which the server supports
for localized error text strings. If one or more arguments are
supplied they indicate the client's preferred languages for error
messages. The server will match each client preference in order
against its internal table of available error strings languages.
For a client preference to match a server language table, the
client's language tag MUST be a prefix of the server's tag and
match up to a "-" or the end of string. If a match is found, the
server returns an OK response. If no match is found, the server
returns an untagged LANG response followed by a NO response.
If no LANG command is issued, all error text strings MUST be in
English. This rule is necessary because the default error text
has to be in a language which is understandable by any pair of
client and server vendors (since both have to diagnose problems).
In addition, the default language for errors has to use the
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US-ASCII subset of UTF-8, since it can be displayed on the largest
number of computers.
Example: C: A003 LANG "fr-ca" "fr" "en-ca" "en-uk"
S: A003 OK "Bonjour"
6.2.3. LANG Untagged Response
Data: list of supported language tags
The LANG response indicates the languages supported for server
error messages.
Example: C: N004 LANG
S: * LANG "fr-ca" "en-ca"
S: N004 OK "LANG completed"
6.2.4. LOGOUT Command
Arguments: none
Data: mandatory untagged response: BYE
Result: OK - logout completed
BAD - command unknown or arguments invalid
The LOGOUT command informs the server that the client is done with
the session. The server must send a BYE untagged response before
the (tagged) OK response, and then close the network connection.
Example: C: A023 LOGOUT
S: * BYE "ACAP Server logging out"
S: A023 OK "LOGOUT completed"
(Server and client then close the connection)
6.2.5. OK Response
Data: optional response code
human-readable text
The OK response indicates an information message from the server.
When tagged, it indicates successful completion of the associated
command. The human-readable text may be presented to the user as
an information message. The untagged form indicates an
information-only message; the nature of the information may be
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indicated by a response code.
Example: S: * OK "XXX - need good example"
6.2.6. NO Response
Data: optional response code
human-readable text
The NO response indicates an operational error message from the
server. When tagged, it indicates unsuccessful completion of the
associated command. The untagged form indicates a warning; the
command may still complete successfully. The human-readable text
describes the condition.
Example: C: A010 SEARCH ...
S: * NO "Master ACAP server is down, your data may
be out of date."
S: A010 OK "search done"
...
C: A222 STORE ("/folder/comp.mail.misc"
"folder.creation-time" "19951206103412")
S: A222 NO (PERMISSION ("/folder/")) "Permission denied"
6.2.7. BAD Response
Data: optional response code
human-readable text
The BAD response indicates an error message from the server. When
tagged, it reports a protocol-level error in the client's command;
the tag indicates the command that caused the error. The untagged
form indicates a protocol-level error for which the associated
command can not be determined; it may also indicate an internal
server failure. The human-readable text describes the condition.
Example: C: ...empty line...
S: * BAD "Empty command line"
C: A443 BLURDYBLOOP
S: A443 BAD "Unknown command"
C: A444 NOOP Hello
S: A444 BAD "invalid arguments"
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6.2.8. BYE Untagged Response
Data: optional response code
human-readable text
The untagged BYE response indicates that the server is about to
close the connection. The human-readable text may be displayed to
the user in a status report by the client. The BYE response may
be sent as part of a normal logout sequence, or as a panic
shutdown announcement by the server. It is also used by some
server implementations as an announcement of an inactivity auto-
logout.
This response is also used as one of two possible greetings at
session startup. It indicates that the server is not willing to
accept a session from this client.
Example: S: * BYE "Auto-logout; idle for too long"
6.2.9. ALERT Untagged Response
Data: optional response code
human-readable text
The human-readable text contains a special human generated alert
message that MUST be presented to the user in a fashion that calls
the user's attention to the message. This is intended to be used
for vital messages from the server administrator to the user, such
as a warning that the server will soon be shut down for
maintenance.
Example: S: * ALERT "This ACAP server will be shut down in
10 minutes for system maintenance."
6.3. Non-Authenticated State
In non-authenticated state, the AUTHENTICATE command establishes
authentication and enters authenticated state. The AUTHENTICATE
command provides a general mechanism for a variety of authentication
techniques.
Server implementations may allow non-authenticated access to certain
information by supporting the SASL ANONYMOUS [SASL-ANON] mechanism.
Once authenticated (including as anonymous), it is not possible to
re-enter non-authenticated state.
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Only the any-state commands (NOOP, LANG and LOGOUT) and the
AUTHENTICATE command are valid in non-authenticated state.
6.3.1. AUTHENTICATE Command
Arguments: SASL mechanism name
optional initial response
Data: continuation data may be requested
Result: OK - authenticate completed, now in authenticated state
NO - authenticate failure: unsupported authentication
mechanism, credentials rejected
BAD - command unknown or arguments invalid,
authentication exchange cancelled
The AUTHENTICATE command indicates an authentication mechanism to
the server. If the server supports the requested authentication
mechanism, it performs an authentication protocol exchange to
authenticate and identify the user. Optionally, it also
negotiates a security layer for subsequent protocol interactions.
If the requested authentication mechanism is not supported, the
server rejects the AUTHENTICATE command by sending a tagged NO
response.
The authentication protocol exchange consists of a series of
server challenges and client answers that are specific to the
authentication mechanism. A server challenge consists of a
command continuation request with the "+" token followed by a
BASE64 encoded string. The client answer consists of a line
consisting of a BASE64 encoded string. If the client wishes to
cancel an authentication exchange, it should issue a line with a
single "*". If the server receives such an answer, it must reject
the AUTHENTICATE command by sending a tagged BAD response.
The optional initial-response argument to the AUTHENTICATE command
is used to save a round trip when using authentication mechanisms
that are defined to send no data in the initial challenge. When
the initial-response argument is used with such a mechanism, the
initial empty challenge is not sent to the client and the server
uses the data in the initial-response argument as if it were sent
in response to the empty challenge. If the initial-response
argument to the AUTHENTICATE command is used with a mechanism
that sends data in the initial challenge, the server rejects the
AUTHENTICATE command by sending a tagged NO response.
The service name specified by this protocol's profile of SASL is
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"acap".
If a security layer is negotiated through the SASL authentication
exchange, it takes effect immediately following the CRLF that
concludes the authentication exchange for the client, and the CRLF
of the tagged OK response for the server.
All ACAP implementations MUST support the PLAIN SASL mechanism
[SASL-PLAIN], although they MAY offer a configuration option to
disable plaintext passwords if site security policy dictates.
ACAP implementations SHOULD support an external encryption service
or a stronger standards track SASL mechanism.
If an AUTHENTICATE command fails with a NO response, the client
may try another authentication mechanism by issuing another
AUTHENTICATE command. In other words, the client may request
authentication types in decreasing order of preference.
Example: S: * ACAP (IMPLEMENTATION "Blorfysoft v3.5")
(SASL "PLAIN" "KERBEROS_V4")
C: A001 AUTHENTICATE KERBEROS_V4
S: + AmFYig==
C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT
+nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd
WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh
S: + or//EoAADZI=
C: DiAF5A4gA+oOIALuBkAAmw==
S: A001 OK "Kerberos V4 authentication successful"
6.4. Searching
This section describes the SEARCH command, for retrieving data from
datasets.
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6.4.1. SEARCH Command
Arguments: dataset or context name
optional list of modifiers
search criteria
Data: intermediate responses: ENTRY, MODTIME, REFER
untagged responses: ADDTO, REMOVEFROM, CHANGE, MODTIME
Result: OK - search completed
NO - search failure: can't perform search
BAD - command unknown or arguments invalid
The SEARCH command identifies a subset of entries in a dataset and
returns information on that subset to the client.
The first argument to SEARCH identifies what is to be searched.
If the string begins with a slash ("/"), it is the name of a
dataset to be searched, otherwise it is a name of a context that
was created by a SEARCH command given previously in the session.
A successful SEARCH command MUST result in a MODTIME intermediate
response.
Following that are zero or more modifiers to the search. Each
modifier may be specified at most once. The defined modifiers
are:
DEPTH number
The SEARCH command will traverse the dataset tree up to the
specified depth. ENTRY responses will include the full path
to the entry. A value of "0" indicates that the search
should traverse the entire tree. A value of "1" is the
default and indicates only the specified dataset should be
searched. If a dataset is traversed which is not located on
the current server, then a REFER intermediate response is
returned for that subtree and the search continues.
HARDLIMIT number
If the SEARCH command would result in more than number
entries, the SEARCH fails with a NO completion result with a
WAYTOOMANY response code.
LIMIT number number
Limits the number of intermediate ENTRY responses that the
search may generate. The first numeric argument specifies
the limit, the second number specifies the number of entries
to return if the number of matches exceeds the limit. If the
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limit is exceeded, the SEARCH command still succeeds,
returning the total number of matches in a TOOMANY response
code in the tagged OK response.
MAKECONTEXT [ENUMERATE] [NOTIFY] context
The SEARCH command creates a context with the name given in
the argument to refer to the matching entries. If the SEARCH
is successful, the context name may then be given as an
argument to subsequent SEARCH commands to search the set of
matching entries. If a context with the specified name
already exists, it is first freed. If a new context may not
be created due to the server's limit on the number of
existing contexts, the command fails, returning a
TRYFREECONTEXT response code in the NO completion response.
The optional "ENUMERATE" and "NOTIFY" arguments may be
included to request enumeration of the context (for virtual
scroll bars) or change notifications for the context.
ENUMERATE requests that the contents of the context be
ordered according to the SORT modifier and that sequential
numbers, starting with one, be assigned to the entries in the
context. This permits the RANGE modifier to be used to fetch
portions of the ordered context.
NOTIFY requests that the server send untagged ADDTO,
REMOVEFROM, CHANGE, and MODTIME responses while the context
created by this SEARCH command exists. The server MAY issue
untagged ADDTO, REMOVEFROM, CHANGE and MODTIME notifications
for a context at any time between the issuing of the SEARCH
command with MAKECONTEXT NOTIFY and the completion of a
FREECONTEXT command for the context. Notifications are only
issued for changes which occur after the server receives the
SEARCH command which created the context. After issuing a
sequence of ADDTO, REMOVEFROM or CHANGE notifications, the
server MUST issue an untagged MODTIME notification indicating
that the client has all updates to the entries in the context
up to and including the given modtime value. Servers are
permitted a reasonable delay to batch change notifications
before sending them to the client.
The position arguments of the ADDTO, REMOVEFROM and CHANGE
notifications are 0 if ENUMERATE is not requested.
NOINHERIT
This causes the SEARCH command to operate without
inheritance. It can be used to tell which values are
explicit overrides. If MAKECONTEXT is also specified, the
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created context is also not effected by inheritance.
RETURN (metadata...)
Specifies what is to be returned in intermediate ENTRY
responses. If this modifier is not specified, no
intermediate ENTRY responses are returned.
Inside the parentheses is a list of attributes, each
optionally followed by a parenthesized list of metadata. If
the parenthesized list of metadata is not specified, it
defaults to "(value)".
An attribute name with a trailing "*" requests all attributes
with that prefix. A "*" by itself requests all attributes.
If the parenthesized list of metadata is not specified for an
attribute with a trailing "*", it defaults to "(attribute
value)".
Following the last intermediate ENTRY response, the server
returns a single intermediate MODTIME response.
SORT (attribute comparator ...)
Specifies the order in which any resulting ENTRY replies are
to be returned to the client. The SORT modifier takes as an
argument a parenthesized list of one or more
attribute/comparator pairs. Attribute lists the attribute to
sort on, comparator specifies the name of the collation rule
to apply to the values of the attribute. Successive
attribute/comparator pairs are used to order two entries only
when all preceding pairs indicate the two entries collate the
same.
If the SORT modifier is used in conjunction with the
MAKECONTEXT modifier, the SORT modifier specifies the
ordering of entries in the created context.
If no SORT modifier is specified, or none of the
attribute/comparator pairs indicates an order for the two
entries, the server uses the order of the entries that exists
in the context or dataset being searched.
Following the modifiers is the search criteria. Searching
criteria consist of one or more search keys. Search keys may be
combined using the AND, and OR search keys. For example, the
criteria (the newline is for readability and not part of the
criteria):
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AND COMPARE "modtime" "+octet" "19951206103400"
COMPARE "modtime" "-octet" "19960112000000"
refers to all entries modified between 10:34 December 6 1995 and
midnight January 12, 1996 UTC.
The currently defined search keys are as follows.
ALL This matches all entries.
AND search-key1 search-key2
Entries that match both search keys.
COMPARE attribute comparator value
Entries for which the value of the specified attribute
collates using the specified comparator the same or later
than the specified value.
COMPARESTRICT attribute comparator value
Entries for which the specified attribute collates using the
specified comparator later than the specified value.
EQUAL attribute comparator value
Entries for which the value of the attribute is equal to the
specified value using the specified comparator.
NOT search-key
Entries that do not match the specified search key.
OR search-key1 search-key2
Entries that match either search key.
PREFIX attribute comparator value
Entries which begin with the specified value using the
specified comparator. If the specified comparator doesn't
support substring matching, a BAD response is returned.
RANGE start end time
Entries which are within the specified range of the
enumerated context's ordering. The lowest-ordered entry in
the context is assigned number one, the next lowest entry is
assigned number two, and so on. The numeric arguments
specify the lowest and highest numbers to match. The time
specifies that the client has processed notifications for the
context up to the specified time. If the context has been
modified since then, the server MUST either return a NO with
a MODIFIED response code, or return the results that the
SEARCH would have returned if none of the changes since that
time had been made.
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RANGE is only permitted on contexts. If RANGE is used with a
dataset, the server MUST return a BAD response.
SUBSTRING attribute comparator value
Entries which contain the specified value, using the
specified comparator. If the specified comparator doesn't
support substring matching, a BAD response is returned.
Example: C: [TODO - write examples]
6.4.2. ENTRY Intermediate Response
Data: entry name
entry data
The ENTRY intermediate response occurs as a result of a SEARCH
command. This is the means by which dataset entries are returned
to the client. The entry with the given name matches the search.
Following the entry name is a set of zero or more lists, one for
each item in the RETURN search modifier, each containing the
requested metadata for the requested attribute(s) within the
entry.
6.4.3. MODTIME Intermediate Response
Data: modtime value
The MODTIME intermediate response occurs as a result of a SEARCH
command. It indicates that the just created context or the
previously returned ENTRY responses include all updates to the
returned entries up to and including the modtime value in the
argument.
6.4.4. REFER Intermediate Response
Data: dataset path
ACAP URL
The REFER intermediate response occurs as a result of a
multi-level SEARCH where one of the levels is located on a
different server. The response indicates the dataset which is not
located on the current server and an ACAP URL for where that
dataset may be found.
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6.5. Contexts
The following commands use contexts created by a SEARCH command with
a MAKECONTEXT modifier.
6.5.1. FREECONTEXT Command
Arguments: context name
Data: no specific data for this command
Result: OK - freecontext completed
NO - freecontext failure: no such context
BAD - command unknown or arguments invalid
The FREECONTEXT command causes the server to free all state
associated with the named context. The context may no longer be
searched and the server will no longer issue any untagged
responses for the context. The context is no longer counted
against the server's limit on the number of contexts.
Example: C: A683 FREECONTEXT "blurdybloop"
S: A683 OK "Freecontext completed"
6.5.2. UPDATECONTEXT Command
Arguments: list of context names
Data: untagged responses: ADDTO REMOVEFROM CHANGE MODTIME
Result: OK - Updatecontext completed: all updates completed
NO - Updatecontext failed: no such context
not a notify context
BAD - command unknown or arguments invalid
The UPDATECONTEXT command causes the server to ensure that the
client is notified of all changes to the contexts listed as
arguments up to the current time. The contexts listed in the
arguments must have been previously given to a successful SEARCH
command with a MAKECONTEXT NOTIFY modifier. A MODTIME untagged
response MUST be returned if any read-write metadata in the
context changed since the last MODTIME for that context. This
includes metadata which is not listed in the RETURN modifier for
the context.
While a server may issue untagged ADDTO, REMOVEFROM, CHANGE, and
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MODTIME at any time, the UPDATECONTEXT command is used to "prod"
the server to send any notifications it has not sent yet.
The UPDATECONTEXT command SHOULD NOT be used to poll for updates.
If two or more UPDATECONTEXT commands occur between the delay
period the server uses to generate unsolicited change
notifications, then the server MAY treat all UPDATECONTEXT
commands after the first as NOOP commands to discourage client
polling.
Example: C: Z4S9 UPDATECONTEXT "blurdybloop" "blarfl"
S: Z4S9 OK "client has been notified of all changes"
6.5.3. ADDTO Untagged Response
Data: context name
entry name
position
metadata list
The untagged ADDTO response informs the client that an entry has
been added to a context. The response includes the position
number of the added entry (the first entry in the context is
numbered 1) and those metadata contained in the entry which match
the RETURN statement when the context was created.
The ADDTO response implicitly adds one to the position of all
members of the context which had position numbers that were
greater than or equal to the ADDTO position number.
Example: S: * ADDTO "blurdybloop" "fred" 15
("addressbook.email" "fred@rock.org")
6.5.4. REMOVEFROM Untagged Response
Data: context name
entry name
old position
The untagged REMOVEFROM response informs the client that an entry
has been removed from a context. The response includes the
position number that the removed entry used to have (the first
entry in the context is numbered 1).
The REMOVEFROM response implicitly subtracts one from the position
numbers of all members of the context which had position numbers
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greater than the REMOVEFROM position number.
Example: S: * REMOVEFROM "blurdybloop" "fred" 15
6.5.5. CHANGE Untagged Response
Data: context name
entry name
old position
new position
metadata list
The untagged CHANGE response informs the client that an entry in a
context has either changed position in the context or has changed
the values of one or more of the attributes specified in the
RETURN modifier when the context was created.
The response includes the previous and current position numbers of
the entry (if ENUMERATE was specified on the context) and the
attribute metadata requested in the RETURN modifier when the
context was created.
The CHANGE response implicitly changes the position numbers of all
entries which had position numbers between the old and new
position. If old position is less than new position, than one is
subtracted from all entries which had position numbers in that
range. Otherwise one is added to all entries which had position
numbers in that range. If the old position and new position are
the same, then no implicit position renumbering occurs.
CHANGE responses are not issued for entries which have changed
position implicitly due to another ADDTO, REMOVEFROM or CHANGE
response.
Example: S: * CHANGE "blurdybloop" "fred" 15 10
("addressbook.email" "fred@stone.org")
6.5.6. MODTIME Untagged Response
Data: context name
modtime value
The untagged MODTIME response informs the client that it has
received all updates to entries in the context which have modtime
values less than or equal to the modtime value in the argument.
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Example: S: * MODTIME mycontext "19970320162338"
6.6. Dataset modification
The following commands and responses handle modification of datasets.
6.6.1. STORE Command
Arguments: entry store list
Data: intermediate responses: ENTRY
Result: OK - store completed
NO - store failure: can't store that name
UNCHANGEDSINCE specified and entry changed
BAD - command unknown or arguments invalid
invalid UTF-8 syntax in attribute name
Creates, modifies or deletes the named entries in the named
datasets. The values of metadata not specified in the command are
not changed. Setting the "value" metadata of an attribute to NIL
removes that attribute from the entry. Setting the "value" of the
"entry" attribute to NIL removes that entry from the dataset.
Changing the value of the "entry" attribute renames the entry.
The STORE command is followed by one or more entry store lists.
Each entry store list begins with an entry path followed by STORE
modifiers, followed by zero or more attribute store items. Each
attribute store item is made up of the attribute name followed by
a NIL (to remove the attribute's value), a single value (to set
the attribute's single value), or a list of metadata items to
modify. The following STORE modifiers may be specified:
NOCREATE
By default, the server MUST create any datasets necessary to
store the entry. If NOCREATE is specified, the STORE command
will fail with a NOEXIST error unless the containing dataset
already exists.
UNCHANGEDSINCE
If the "modtime" of the entry is later than the
unchangedsince time, then the store fails with a MODIFIED
response code. Use of UNCHANGEDSINCE with a time of
"00000101000000" will always fail if the entry exists.
Clients writing to a shared dataset are encouraged to use
UNCHANGEDSINCE when modifying an existing entry.
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The server MUST either make all the changes specified or make none
of them. If successful, the server MUST update the "modtime"
attribute for every entry which was changed.
It is illegal to list any metadata item within an attribute twice,
any attribute within an entry twice or to any entry path twice.
The server MUST return a BAD response if this happens. If the
"modtime" attribute is included in the STORE command, then the
server MUST return a NO response with an ILLEGAL response code.
When NIL is stored to an attribute, and there is an inherited
default value, then an ENTRY intermediate response is generated to
notify the client of this change, this response includes the
attribute name and value metadata for each attribute which
reverted to a non-NIL inherited setting.
Example: C: A342 STORE ("/addressbook/user/fred/ABC547"
"addressbook.phone" "555-1234"
"addressbook.CommonName" "Barney Rubble"
"addressbook.email" NIL)
S: A342 OK "Store completed"
C: A343 STORE ("/addressbook/user/joe/ABD42"
UNCHANGEDSINCE "19970320162338"
"user.joe.hair-length" "10 inches")
S: A343 NO (MODIFIED) "'ABD42' has been changed
by somebody else."
C: A344 STORE ("/addressbook/group/Tech/ACD54"
"entry" NIL)
S: A344 OK "Store completed"
C: A345 STORE ("/option/~/mail/SMTPserver" "value" NIL)
S: A345 ENTRY "SMTPserver" "value" "smtp.server.do.main"
S: A345 OK "Store completed"
6.6.2. DELETEDSINCE Command
Arguments: dataset name
time
Data: intermediate response: DELETED
Result: OK - DELETED completed
NO - DELETED failure: can't read dataset
date too far in the past
BAD - command unknown or arguments invalid
The DELETEDSINCE command returns in intermediate DELETED replies
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the names of entries that have been deleted from the named dataset
since the given time.
Servers may impose a limit on the number or age of deleted entry
names they keep track of. If the server does not have information
going back to the specified time, the command fails, returning a
TOOOLD response code in the tagged NO response.
Example: C: Z4S9 DELETEDSINCE "/folder/site" 19951205103412
S: Z4S9 DELETED "blurdybloop"
S: Z4S9 DELETED "anteaters"
S: Z4S9 OK "DELETEDSINCE completed"
C: Z4U3 DELETEDSINCE "/folder/site" 19951009040854
S: Z4U3 NO (TOOOLD) "Don't have that information"
6.6.3. DELETED Intermediate Response
Data: entry name
The intermediate DELETED response occurs as a result of a
DELETEDSINCE command. It returns an entry that has been deleted
from the dataset specified in the DELETEDSINCE command.
Example: S: Z4S9 DELETED "blurdybloop"
6.7. Access Control List Commands
The commands in this section are used to manage access control lists.
6.7.1. SETACL Command
Arguments: acl object
authentication identifier
access rights
Data: no specific data for this command
Result: OK - setacl completed
NO - setacl failure: can't set acl
BAD - command unknown or arguments invalid
The SETACL command changes the access control list on the
specified object so that the specified identifier is granted the
permissions enumerated in rights. If the object did not
previously have an access control list, one is created.
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Example: C: A123 SETACL ("/addressbook/~/public/") "anyone" "r"
S: A123 OK "Setacl complete"
C: A124 SETACL ("/folder/site/") "B1FF" "rwa"
S: A124 NO (PERMISSION ("/folder/site/")) "'B1FF' not
permitted to modify access rights
for '/folder/site/'"
6.7.2. DELETEACL Command
Arguments: acl object
optional authentication identifier
Data: no specific data for this command
Result: OK - deleteacl completed
NO - deleteacl failure: can't delete acl
BAD - command unknown or arguments invalid
If given the optional identifier argument, the DELETEACL command
removes any portion of the access control list on the specified
object for the specified identifier.
If not given the optional identifier argument, the DELETEACL
command removes the ACL from the object entirely, causing access
to be controlled by a higher-level default ACL. This form of the
DELETEACL command is not permitted on the default ACL for a
dataset and servers MUST return a BAD.
Example: C: A223 DELETEACL ("/addressbook/~/public") "anyone"
S: A223 OK "Deleteacl complete"
C: A224 DELETEACL ("/folder/site")
S: A224 BAD "Can't delete ACL from dataset"
C: A225 DELETEACL ("/addressbook/user/fred"
"addressbook.email" "barney")
S: A225 OK "Deleteacl complete"
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6.7.3. MYRIGHTS Command
Arguments: acl object
Data: intermediate responses: MYRIGHTS
Result: OK - myrights completed
NO - myrights failure: can't get rights
BAD - command unknown or arguments invalid
The MYRIGHTS command returns the set of rights that the client has
to the given dataset or dataset attribute.
Example: C: A003 MYRIGHTS ("/folder/site")
S: A003 MYRIGHTS "r"
S: A003 OK "Myrights complete"
6.7.4. MYRIGHTS Intermediate Response
Data: rights
The MYRIGHTS response occurs as a result of a MYRIGHTS command.
The argument is the set of rights that the client has for the
object referred to in the MYRIGHTS command.
6.7.5. LISTRIGHTS Command
Arguments: acl object
authentication identifier
Data: untagged responses: LISTRIGHTS
Result: OK - listrights completed
NO - listrights failure: can't get rights list
BAD - command unknown or arguments invalid
The LISTRIGHTS command takes an object and an identifier and
returns information about what rights may be granted to the
identifier in the ACL for the object.
Example: C: a001 LISTRIGHTS ("/folder") "smith"
S: a001 LISTRIGHTS "r" "w"
S: a001 OK Listrights completed
C: a005 LISTRIGHTS ("/folder/archive.imap") "anyone"
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S: a005 LISTRIGHTS "" "r" "w"
S: a005 OK Listrights completed
6.7.6. LISTRIGHTS Intermediate Response
Data: required rights
list of optional rights
The LISTRIGHTS response occurs as a result of a LISTRIGHTS
command. The first argument is a string containing the (possibly
empty) set of rights the identifier will always be granted on the
dataset or attribute.
Following this are zero or more strings each containing a single
right the identifier may be granted in the dataset or attribute.
The same right MUST NOT be listed more than once in the LISTRIGHTS
response.
6.8. Quotas
The section defines the commands and responses relating to quotas.
6.8.1. GETQUOTA Command
Arguments: dataset
Data: untagged responses: QUOTA
Result: OK - Quota information returned
NO - Quota failure: can't access resource limit
no resource limit
BAD - command unknown or arguments invalid
The GETQUOTA command takes the name of a dataset, and returns in
an untagged QUOTA response the name of the dataset, its quota
root, the quota limit on that root and the quota usage within that
root.
Example: C: A043 GETQUOTA "/option/user/fred/common"
S: * QUOTA "/option/user/fred/common" "/quota/user/fred"
1048576 2475
S: A043 OK "Getquota completed"
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6.8.3. QUOTA Untagged Response
Data: dataset
quota root
quota limit in bytes
amount of quota limit used
The QUOTA untagged response is generated as a result of a GETQUOTA
command or MAY be generated by the server in response to a SEARCH
or STORE command to warn about high usage of a quota. It includes
the name of the applicable dataset, the quota root, the quota
limit in bytes and the quota usage.
6.9. Extensions
In order to simplify the process of extending the protocol, clients
MUST ignore unknown server responses which meet the syntax of
response-extend. In addition, clients MUST ignore server response
codes which meet the syntax of resp-code-ext. Availability of new
commands MUST be announced via a capability on the initial greeting
line and such commands SHOULD meet the syntax of command-extend.
Servers MUST respond to unknown commands with a BAD command
completion result. Servers MUST skip over non-synchronizing literals
contained in an unknown command. This may be done by assuming the
unknown command matches the command-extend syntax, or by reading a
line at a time and checking for the non-synchronizing literal syntax
at the end of the line.
7. Registration Procedures
ACAP's usefulness comes from providing a structured storage model for
all sorts of configuration data. However, for its potential to be
achieved, it is important that the Internet community strives for the
following goals:
(1) Standardization. It is very important to standardize dataset
classes. The authors hope that ACAP achieves the success that SNMP
has seen with the definition of numerous standards track MIBs.
(2) Community Review. In the absence of standardization, it is
important to get community review on a proposal to improve its
engineering quality. Community review is strongly recommended prior
to registration. The ACAP implementors mailing list
<ietf-acap@andrew.cmu.edu> should be used for this purpose.
(3) Registration. Registration serves a two-fold purpose. First it
prevents use of the same name for different purposes, and second it
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provides a one-stop list which can be used to locate existing
extensions or dataset classes to prevent duplicate work.
The following registration templates may be used to register ACAP
protocol elements.
7.1. Comparators
Additional comparators may be registered with IANA on a first-come,
first-served basis. Comparators intended for interoperable use MUST
be defined as a standards-track or IESG-approved-experimental RFC.
To: XXX@XXX.XXX
Subject: Registration of new comparator
Comparator name:
Scope:
(Describe any limitations on intended use in terms of standards scope,
dataset classes, and specific locales.)
Operations: Ordering, Equality, Substring match
Published Specification(s):
(If the published specification is not standards track, or no
published specification is referenced then the comparator is
assumed to be for limited use.)
Person and email address to contact for further information:
7.2. ACAP Capabilities
New ACAP capabilities MUST be standards track or IESG approved
experimental RFCs. Registration provides a simple way to locate all
extensions. Careful consideration should be made before extending
the protocol, as it can lead to complexity or interoperability
problems.
To: XXX@XXX.XXX
Subject: Registration of ACAP capability
Capability name:
Capability keyword:
Capability arguments:
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Published Specification(s):
(Standards track or IESG approved experimental RFC)
Person and email address to contact for further information:
7.3. ACAP Response Codes
ACAP response codes are registered on a first come, first served
basis. Proposals SHOULD be reviewed by the acap implementors mailing
list mentioned above.
To: XXX@XXX.XXX
Subject: Registration of ACAP response code
Response Code:
Arguments:
Purpose:
Published Specification(s):
(Optional, but encouraged)
Person and email address to contact for further information:
7.4. Dataset Classes
A dataset class provides a core set of attributes for use in a
specified hierarchy. It may also define rules for the dataset
hierarchy underneath that class. Dataset class specifications must
be standards track or IESG approved experimental RFCs.
To: XXX@XXX.XXX
Subject: Registration of ACAP dataset class
Dataset class name/attribute prefix:
Purpose:
Published Specification(s):
(Standards track or IESG approved experimental RFC)
Person and email address to contact for further information:
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7.5. Vendor Subtree
Vendors may reserve a portion of the ACAP namespace for private use.
Dataset class names beginning with "vendor.<company/product name>."
are reserved for use by that company or product. In addition, all
attribute names beginning with "vendor.<company/product name>." are
reserved for use by that company or product. Registration is on a
first come, first served basis. Whenever possible, private
attributes and dataset classes should be avoided in favor of
improving interoperable dataset class definitions.
To: XXX@XXX.XXX
Subject: Registration of ACAP vendor subtree
Private Prefix: vendor.<company/product name>.
Person and email address to contact for further information:
(company names and addresses should be included when appropriate)
8. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in [ABNF].
Except as noted otherwise, all alphabetic characters are
case-insensitive. The use of upper or lower case characters to
define token strings is for editorial clarity only. Implementations
MUST accept these strings in a case-insensitive fashion.
The "command" rule below defines the syntax for commands sent by the
client. The "response" rule below defines the syntax for responses
sent by the server.
ALPHA = %x41..5A / %x61..7A
;; alphabetic letters
ATOM-CHAR = "!" / %x23..27 / %x2A..5B / %x5D..7A / %x7C..7E
;; Any CHAR except ATOM-SPECIALS
ATOM-SPECIALS = "(" / ")" / "{" / SPACE / CTL / QUOTED-SPECIALS
BASE64-CHAR = ALPHA / DIGIT / "+" / "/"
;; case-sensitive
CHAR = %x01..7F
CR = %x0C
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CRLF = CR LF
CTL = %x00..1F / %x7F
DIGIT = "0" / DIGIT-NZ
DIGIT-NZ = %x31..39
; non-zero digits ("1" - "9")
LF = %x0A
OCTET = %x00..FF
QUOTED-CHAR = SAFE-UTF8-CHAR / "\" QUOTED-SPECIALS
QUOTED-SPECIALS = <"> / "\"
SAFE-CHAR = %x01..09 / %x0B..0C / %x0E..21 /
%x23..5B / %x5D..7F
;; any TEXT-CHAR except QUOTED-SPECIALS
SAFE-UTF8-CHAR = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4 /
UTF8-5 / UTF8-6
SPACE = %x20
TAG-CHAR = %x21 / %x23..27 / %x2C..5B / %x5D..7A / %x7C..7E
;; Any ATOM-CHAR except "*" or "+"
TEXT-CHAR = %x01..09 / %x0B..0C / %x0E..7F
;; any CHAR except CR and LF
TEXT-UTF8-CHAR = SAFE-UTF8-CHAR / QUOTED-SPECIALS
UTF8-1 = %x80..BF
UTF8-2 = %xC0..DF UTF8-1
UTF8-3 = %xE0..EF 2UTF8-1
UTF8-4 = %xF0..F7 3UTF8-1
UTF8-5 = %xF8..FB 4UTF8-1
UTF8-6 = %xFC..FD 5UTF8-1
UTF8-CHAR = TEXT-UTF8-CHAR / CR / LF
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acl = "(" *acl-identrights ")"
acl-identifier = string-utf8
;; MUST NOT contain TAB
acl-identrights = string-utf8
;; The identifier followed by a TAB, followed by
;; the rights.
acl-object = "(" dataset [SPACE attribute [SPACE entry-name]] ")"
acl-rights = quoted
atom = ALPHA *1023ATOM-CHAR
attribute = string-utf8
;; dot-separated attribute name
;; MUST NOT contain "*" or "%"
attribute-store = attribute SPACE (value-nil /
"(" 1*(metadata-write-q SPACE value-store) ")")
;; MUST NOT include the same metadata twice
auth-type = iana-token
;; as defined in SASL [SASL]
base64-token = *(4BASE64-CHAR) [base64-terminal]
base64-terminal = (2BASE64-CHAR "==") / (3BASE64-CHAR "=")
command = tag SPACE (command-any / command-auth /
command-nonauth) CRLF
;; Modal based on state
command-authent = "AUTHENTICATE" SPACE auth-type [SPACE base64-token]
*(CRLF base64-token)
command-any = "NOOP" / command-lang / "LOGOUT"
command-auth = command-delacl / command-dsince /
command-freectx / command-getquota /
command-lrights / command-myrights /
command-search / command-setacl /
command-store
;; only valid in authenticated state
command-delacl = "DELETEACL" SPACE acl-object [SPACE acl-identifier]
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command-dsince = "DELETEDSINCE" SPACE dataset SPACE time
command-extend = extend-token [SPACE extension-data]
command-freectx = "FREECONTEXT" SPACE context
command-getquota = "GETQUOTA" SPACE dataset
command-lang = "LANG" *(SPACE lang-tag)
command-lrights = "LISTRIGHTS" SPACE acl-object
command-myrights = "MYRIGHTS" SPACE acl-object
command-nonauth = command-authent
;; only valid in non-authenticated state
command-search = "SEARCH" SPACE (dataset / context)
*(SPACE search-modifier)
SPACE search-criteria
;; MUST NOT include same search-modifier twice
command-setacl = "SETACL" SPACE acl-object SPACE acl-identifier
SPACE acl-rights
command-store = "STORE" SPACE store-entry-list
comparator = <"> comparator-name <">
comparator-name = ["+" / "-"] iana-token
context = string-utf8
;; MUST NOT begin with slash ("/")
dataset = string-utf8
;; slash-separated dataset name
;; begins with slash
entry = entry-name / entry-path
entry-name = string-utf8
;; entry name MUST NOT contain slash
;; MUST NOT begin with "."
entry-path = string-utf8
;; slash-separated path to entry
;; begins with slash
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entry-relative = string-utf8
;; potentially relative path to entry
extend-token = atom
;; MUST be defined by a standards track or
;; IESG approved experimental protocol extension
extension-data = extension-item *(SPACE extension-item)
extension-item = extend-token / string / number /
"(" [extension-data] ")"
iana-token = atom
;; MUST be registered with IANA
initial-greeting = "*" SPACE "ACAP" *(SPACE "(" init-capability ")") CRLF
init-capability = init-cap-compare / init-cap-context /
init-cap-extend / init-cap-implem / init-cap-sasl
init-cap-compare = "COMPARATORS" SPACE string-list
init-cap-context = "CONTEXTLIMIT" SPACE string
init-cap-extend = iana-token [SPACE string-list]
init-cap-implem = "IMPLEMENTATION" SPACE string
init-cap-sasl = "SASL" SPACE string-list
lang-tag = <"> Language-Tag <">
;; Language-Tag rule is defined in [LANG-TAGS]
literal = "{" number [ "+" ] "}" CRLF *OCTET
;; The number represents the number of octets
;; MUST be literal-utf8 except for values
literal-utf8 = "{" number [ "+" ] "}" CRLF *UTF8-CHAR
;; The number represents the number of octets
;; not the number of characters
metadata = attribute [ "(" metadata-type-list ")" ]
;; attribute MAY end in "*" as wildcard.
metadata-list = metadata *(SPACE metadata)
metadata-type = "attribute" / "myrights" / "size" /
"count" / metadata-write
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metadata-type-q = <"> metadata-type <">
metadata-type-list = metadata-type-q *(SPACE metadata-type-q)
metadata-write = "value" / "acl"
metadata-write-q = <"> metadata-write <">
nil = "NIL"
nstring = nil / string
number = *DIGIT
;; A 32-bit unsigned number.
;; (0 <= n < 4,294,967,296)
nz-number = DIGIT-NZ *DIGIT
;; A 32-bit unsigned non-zero number.
;; (0 < n < 4,294,967,296)
position = number
;; "0" if context is not enumerated
;; otherwise this is non-zero
quota-limit = number
quota-root = entry-path
quota-usage = number
quoted = <"> *QUOTED-CHAR <">
;; limited to 1024 octets between the <">s
response = response-addto / response-alert / response-bye /
response-change / response-cont /
response-deleted / response-done / response-entry /
response-extend / response-listr /
response-lang / response-mtimei / response-mtimeu /
response-myright / response-quota /
response-refer / response-remove / response-stat
response-addto = "*" SPACE "ADDTO" SPACE context SPACE entry-name
SPACE position SPACE return-data-list
response-alert = "*" SPACE "ALERT" SPACE resp-body CRLF
;; Client MUST display alert text to user
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response-bye = "*" SPACE "BYE" SPACE resp-body CRLF
;; Server will disconnect condition
response-change = "*" SPACE "CHANGE" SPACE context SPACE entry-name
SPACE position SPACE position SPACE return-data-list
response-cont = "+" SPACE (quoted / base64-token)
response-deleted = tag SPACE "DELETED" SPACE entry-name
response-done = tag SPACE resp-cond-state CRLF
response-entry = tag SPACE "ENTRY" SPACE entry SPACE return-data-list
response-extend = (tag / "*") SPACE extend-token [SPACE extension-data]
response-lang = "*" SPACE "LANG" SPACE lang-tag *(SPACE lang-tag)
response-listr = tag SPACE "LISTRIGHTS" SPACE acl-rights
*(SPACE acl-rights)
response-mtimei = tag SPACE "MODTIME" SPACE time
response-mtimeu = "*" SPACE "MODTIME" SPACE context SPACE time
response-myright = tag SPACE "MYRIGHTS" SPACE acl-rights
response-quota = "*" SPACE "QUOTA" SPACE dataset SPACE quota-root
SPACE quota-limit SPACE quota-usage
response-refer = tag SPACE "REFER" SPACE dataset 1*(SPACE
<"> url-relative <">)
response-remove = "*" SPACE "REMOVEFROM" SPACE context SPACE
entry-name SPACE position
response-stat = "*" SPACE resp-cond-state CRLF
resp-body = ["(" resp-code ")" SPACE] quoted
resp-code = "ENCRYPT-NEEDED" / resp-code-inval /
resp-code-many / resp-code-mod /
resp-code-noexist / resp-code-perm /
"PLAINTEXT-DENIED" / "QUOTA" / resp-code-refer /
"TRANSITION-NEEDED" / "TRYCACHE" /
"TRYFREECONTEXT" / resp-code-way / resp-code-ext
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resp-code-ext = iana-token [SPACE extension-data]
;; unknown response codes are ignored by the client.
resp-code-inval = "INVALID" 1*(SPACE entry-path SPACE attribute)
resp-code-many = "TOOMANY" SPACE nz-number
resp-code-mod = "MODIFIED" SPACE entry-path
resp-code-noexist = "NOEXIST" SPACE dataset
resp-code-perm = "PERMISSION" SPACE acl-object
resp-code-refer = "REFER" 1*(SPACE <"> url-relative <">)
resp-code-way = "WAYTOOMANY"
resp-cond-state = ("OK" / "NO" / "BAD") SPACE resp-body
;; Status condition
return-data = "(" return-metadata *(SPACE return-metadata) ")"
;; one return-data list is included per item in
;; the RETURN statement
return-data-list = return-data *(SPACE return-data)
return-metadata = nil / string / value-list / acl
searchkey-equal = "EQUAL" SPACE attribute SPACE comparator
SPACE value-nil
searchkey-comp = "COMPARE" SPACE attribute SPACE comparator SPACE value
searchkey-prefix = "PREFIX" SPACE attribute SPACE comparator SPACE value
searchkey-range = "RANGE" SPACE nz-number SPACE nz-number
SPACE time
searchkey-strict = "COMPARESTRICT" SPACE attribute SPACE comparator
SPACE value
searchkey-substr = "SUBSTRING" SPACE attribute SPACE comparator
SPACE value
searchmod-depth = "DEPTH" SPACE number
searchmod-hard = "HARDLIMIT" SPACE nz-number
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searchmod-limit = "LIMIT" SPACE number SPACE number
searchmod-make = "MAKECONTEXT" [SPACE "ENUMERATE"]
[SPACE "NOTIFY"] SPACE context
searchmod-ninh = "NOINHERIT"
searchmod-return = "RETURN" SPACE "(" [metadata-list] ")"
searchmod-sort = "SORT" SPACE "(" sort-list ")"
search-criteria = "ALL" / searchkey-equal / searchkey-comp /
searchkey-strict / searchkey-range /
searchkey-prefix / searchkey-substr /
"NOT" SPACE search-criteria /
"OR" SPACE search-criteria SPACE search-criteria /
"AND" SPACE search-criteria SPACE search-criteria
search-modifier = searchmod-depth / searchmod-hard /
searchmod-limit / searchmod-make / searchmod-ninh /
searchmod-return / searchmod-sort
sort-list = sort-item *(SPACE sort-item)
sort-item = attribute SPACE comparator
store-entry = "(" entry-path *(SPACE store-modifier)
*(SPACE attribute-store) ")"
;; MUST NOT include the same store-modifier twice
;; MUST NOT include the same attribute twice
store-entry-list = store-entry *(SPACE store-entry)
;; MUST NOT include the same entry twice
store-modifier = store-mod-unchang / store-mod-nocreate
store-mod-nocreate = "NOCREATE"
store-mod-unchang = "UNCHANGEDSINCE" SPACE time
string = quoted / literal
string-list = string *(SPACE string)
string-utf8 = quoted / literal-utf8
tag = 1*32TAG-CHAR
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time = <"> time-year time-month time-day time-hour
time-minute time-second time-subsecond <">
;; Timestamp in UTC
time-day = 2DIGIT ;; 01-31
time-hour = 2DIGIT ;; 00-23
time-minute = 2DIGIT ;; 00-59
time-month = 2DIGIT ;; 01-12
time-second = 2DIGIT ;; 00-60
time-subsecond = *DIGIT
time-year = 4DIGIT
value = string
value-any = value-nil / value-list
value-list = "(" [value *(SPACE value)] ")"
value-nil = value / nil
value-store = value-any / acl
url-acap = "acap://" url-server "/" url-enc-entry [url-filter]
;; url-enc-entry interpreted relative to "/"
url-attr-list = url-enc-attr *("&" url-enc-attr)
url-auth = ";AUTH=" ("*" / url-enc-auth)
url-achar = uchar / "&" / "=" / "~"
;; See RFC 1738 for definition of "uchar"
url-char = uchar / "=" / "~" / ":" / "@" / "/"
;; See RFC 1738 for definition of "uchar"
url-enc-attr = 1*url-char
;; encoded version of attribute name
url-enc-auth = 1*url-achar
;; encoded version of auth-type above
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url-enc-entry = 1*url-char
;; encoded version of entry-relative above
url-enc-user = *url-achar
;; encoded version of login userid
url-filter = "?" url-attr-list
url-relative = url-acap / [url-enc-entry] [url-filter]
;; url-enc-entry is relative to base URL
url-server = [url-user [url-auth] "@"] hostport
;; See RFC 1738 for definition of "hostport"
9. Multi-lingual Considerations
The IAB charset workshop [IAB-CHARSET] came to a number of
conclusions which influenced the design of ACAP. The decision to use
UTF-8 as the character encoding scheme was based on that work. The
LANG command to negotiate a language for error messages is also
included.
Section 3.4.5 of the IAB charset workshop report states that there
should be a way to identify the natural language for human readable
strings. Several promising proposals have been made for use within
ACAP, but no clear consensus on a single method is apparent at this
stage. The following rules are likely to permit the addition of
multi-lingual support in the future:
(1) A work in progress called Multi-Lingual String Format (MLSF)
proposes a layer on top of UTF-8 which uses otherwise illegal UTF-8
sequences to store language tags. In order to permit its addition to
a future version of this standard, client-side UTF-8 interpreters
SHOULD silently ignore illegal multi-byte UTF-8 characters, and treat
illegal single-byte UTF-8 characters as end of string markers.
Servers, for the time being, MUST silently accept illegal UTF-8
characters, except in attribute names and entry names. Clients MUST
NOT send illegal UTF-8 characters to the server unless a future
standard changes this rule.
(2) There is a proposal to add language tags to Unicode. To support
this, servers MUST be able to store UTF-8 characters of up to 20 bits
of data.
(3) The metadata item "language" is reserved for future use.
(4) The ";" character in attribute names is reserved for future use.
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10. Security Considerations
The AUTHENTICATE command uses SASL [SASL] to provide basic
authentication, authorization, integrity and privacy services. This
is described in section ###. The security considerations for the
PLAIN SASL mechanism [SASL-PLAIN] also apply.
ACAP protocol transactions are susceptible to passive observers or
man in the middle attacks which alter the data, unless the optional
encryption and integrity services of the AUTHENTICATE command are
offered, or an external security mechanism is used for protection.
It may be useful to allow configuration of both clients and servers
to refuse to transfer sensitive information in the absence of strong
encryption.
ACAP access control lists provide fine grained authorization for
access to attributes. A number of related security issues are
described in section ###.
ACAP clients are encouraged to consider the security problems
involved with a lab computer situation. Specifically, a client cache
of ACAP configuration information MUST NOT allow access by an
unauthorized user. One way to assure this is for an ACAP client to
be able to completely flush any non-public cached configuration data
when a user leaves.
As laptop computers can be easily stolen and a cache of configuration
data may contain sensitive information, a disconnected mode ACAP
client may wish to encrypt and password protect cached configuration
information.
11. Acknowledgments
Many thanks to the follow people who helped design ACAP over the past
four years: Wallace Colyer, Mark Crispin, Jack DeWinter, Rob Earhart,
Ned Freed, Randy Gellens, Terry Gray, J. S. Greenfield, Steve Hole,
Steve Hubert, Dave Roberts, Bart Schaefer, Matt Wall and other
participants of the IETF ACAP working group.
12. Authors' Addresses
Chris Newman
Innosoft International, Inc.
1050 Lakes Drive
West Covina, CA 91790 USA
Email: chris.newman@innosoft.com
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John Gardiner Myers
Netscape Communications
501 East Middlefield Road
Mail Stop MV-029
Mountain View, CA 94043
Email: jgmyers@netscape.com
Appendices
A. References
[ABNF] Crocker, D., "Augmented BNF for Syntax Specifications: ABNF",
Work in progress: draft-ietf-drums-abnf-xx.txt
[BASIC-URL] Berners-Lee, Masinter, McCahill, "Uniform Resource
Locators (URL)", RFC 1738, CERN, Xerox Coproration, University of
Minnesota, December 1994.
<ftp://ds.internic.net/rfc/rfc1738.txt>
[IAB-CHARSET] Weider, Preston, Simonsen, Alvestrand, Atkinson,
Crispin, Svanberg, "The Report of the IAB Character Set Workshop held
29 February - 1 March, 1996", RFC 2130, April 1997.
<ftp://ds.internic.net/rfc/rfc2130.txt>
[IMAP4] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 2060, University of Washington, December 1996.
<ftp://ds.internic.net/rfc/rfc2060.txt>
[IMAP-ACL] Myers, J., "IMAP4 ACL extension", RFC 2086, Carnegie
Mellon, January 1997.
<ftp://ds.internic.net/rfc/rfc2086.txt>
[ISO-10646] ISO/IEC 10646-1:1993(E) "Information Technology--
Universal Multiple-octet Coded Character Set (UCS)." See also
amendments 1 through 7, plus editorial corrections.
[ISO-C] "Programming languages -- C", ISO/IEC 9899:1990,
International Organization for Standardization. This is effectively
the same as ANSI C standard X3.159-1989.
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[KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997.
<ftp://ds.internic.net/rfc/rfc2119.txt>
[LANG-TAGS] Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766.
<ftp://ds.internic.net/rfc/rfc1766.txt>
[REL-URL] Fielding, "Relative Uniform Resource Locators", RFC 1808,
UC Irvine, June 1995.
<ftp://ds.internic.net/rfc/rfc1808.txt>
[SASL] Myers, J., "Simple Authentication and Security Layer (SASL)",
Work in progress: draft-myers-auth-sasl-xx.txt
[SASL-ANON] Newman, "Anonymous SASL Mechanism", Work in progress:
draft-newman-sasl-anon-xx.txt.
[SASL-PLAIN] Newman, "Plaintext Password SASL Mechanism and
Transition Codes", Work in progress: draft-newman-sasl-plaintrans-
xx.txt.
[UNICODE-2] The Unicode Consortium, "The Unicode Standard, Version
2.0", Addison-Wesley, 1996. ISBN 0-201-48345-9.
[US-ASCII] "USA Standard Code for Information Interchange," X3.4.
American National Standards Institute: New York (1968).
[UTF8] Yergeau, F. "UTF-8, a transformation format of Unicode and ISO
10646", RFC 2044, Alis Technologies, October 1996.
<ftp://ds.internic.net/rfc/rfc2044.txt>
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B. ACAP Keyword Index
ACAP (untagged response) ................................... 29
ADDTO (untagged response) .................................. 42
ALERT (untagged response) .................................. 33
ALL (search keyword) ....................................... 39
AND (search keyword) ....................................... 39
AUTHENTICATE (command) ..................................... 34
BAD (response) ............................................. 32
BYE (untagged response) .................................... 33
CHANGE (untagged response) ................................. 43
COMPARATORS (ACAP capability) .............................. 29
COMPARE (search keyword) ................................... 39
COMPARESTRICT (search keyword) ............................. 39
CONTEXTLIMIT (ACAP capability) ............................. 29
DELETEACL (command) ........................................ 47
DELETED (intermediate response) ............................ 46
DELETEDSINCE (command) ..................................... 45
DEPTH (search modifier) .................................... 36
ENCRYPT-NEEDED (response code) ............................. 20
ENTRY (intermediate response) .............................. 40
EQUAL (search keyword) ..................................... 39
FREECONTEXT (command) ...................................... 41
GETQUOTA (command) ......................................... 49
HARDLIMIT (search modifier) ................................ 36
IMPLEMENTATION (ACAP capability) ........................... 29
INVALID (response code) .................................... 20
LANG (command) ............................................. 30
LANG (untagged response) ................................... 31
LIMIT (search modifier) .................................... 36
LISTRIGHTS (command) ....................................... 48
LISTRIGHTS (intermediate response) ......................... 49
LOGOUT (command) ........................................... 31
MAKECONTEXT (search modifier) .............................. 37
MODIFIED (response code) ................................... 21
MODTIME (intermediate response) ............................ 40
MODTIME (untagged response) ................................ 43
MYRIGHTS (command) ......................................... 47
MYRIGHTS (intermediate response) ........................... 48
NO (response) .............................................. 32
NOCREATE (store modifier) .................................. 44
NOEXIST (response code) .................................... 21
NOINHERIT (search modifier) ................................ 37
NOOP (command) ............................................. 30
NOT (search keyword) ....................................... 39
OK (response) .............................................. 31
OR (search keyword) ........................................ 39
PERMISSION (response code) ................................. 21
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PLAINTEXT-DENIED (response code) ........................... 21
PREFIX (search keyword) .................................... 39
QUOTA (response code) ...................................... 21
QUOTA (untagged response) .................................. 50
RANGE (search keyword) ..................................... 39
REFER (intermediate response) .............................. 40
REFER (response code) ...................................... 21
REMOVEFROM (untagged response) ............................. 42
RETURN (search modifier) ................................... 38
SASL (ACAP capability) ..................................... 29
SEARCH (command) ........................................... 35
SETACL (command) ........................................... 46
SORT (search modifier) ..................................... 38
STORE (command) ............................................ 44
SUBSTRING (search keyword) ................................. 40
TOOMANY (response code) .................................... 21
TRANSITION-NEEDED (response code) .......................... 21
TRYCACHE (response code) ................................... 21
TRYFREECONTEXT (response code) ............................. 22
UNCHANGEDSINCE (store modifier) ............................ 44
UPDATECONTEXT (command) .................................... 41
WAYTOOMANY (response code) ................................. 22
acl (attribute metadata) ................................... 14
anyone (ACL identifier) .................................... 19
attribute (attribute metadata) ............................. 14
dataset.acl (dataset attribute) ............................ 26
dataset.acl.<attribute> (dataset attribute) ................ 26
dataset.inherit (dataset attribute) ........................ 26
en-nocase (comparator) ..................................... 18
entry (predefined attribute) ............................... 13
modtime (predefined attribute) ............................. 13
myrights (attribute metadata) .............................. 14
numeric (comparator) ....................................... 18
octet (comparator) ......................................... 17
quota.limit (predefined attribute) ......................... 28
quota.usage (predefined attribute) ......................... 28
size (attribute metadata) .................................. 14
subdataset (predefined attribute) .......................... 13
value (attribute metadata) ................................. 15
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