home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
kermit.columbia.edu
/
kermit.columbia.edu.tar
/
kermit.columbia.edu
/
e
/
id-rfc2941bis.txt
< prev
next >
Wrap
Text File
|
2002-04-14
|
34KB
|
741 lines
Network Working Group T. Ts'o, Editor
Internet-Draft: draft-altman-rfc2941bis-02
Obsoletes: 2941 J. Altman
Columbia University
April 2002
Telnet Authentication Option
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. 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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
Abstract
This document describes the authentication option to the telnet [1]
protocol as a generic method for negotiating an authentication type
and mode including whether encryption should be used and if
credentials should be forwarded. While this document summarizes
currently utilized commands and types it does not define a specific
authentication type. Separate documents are to be published defining
each authentication type.
This document updates a previous specification of the telnet
authentication option, RFC 2941 [2], to allow the AUTHENTICATION
option to be used in conjunction with the START_TLS option [5].
0. Changes since RFC 2941
. Consolidates and expands the security considerations section
. Describes integration with START_TLS
1. Command Names and Codes
AUTHENTICATION 37
Authentication Commands
IS 0
SEND 1
REPLY 2
NAME 3
Authentication Types
NULL 0
KERBEROS_V4 1
KERBEROS_V5 2
SPX* 3
MINK* 4
SRP 5
RSA*[also used by SRA*] 6
SSL* 7
[unassigned] 8
[unassigned] 9
LOKI* 10
SSA* 11
KEA_SJ 12
KEA_SJ_INTEG 13
DSS 14
NTLM* 15
Authentication types followed by (*) were never submitted to the
IETF for consideration as an Internet standard.
Following historical practice, future authentication type numbers
and authentication modifiers will be assigned by the IANA under a
First Come First Served policy as outlined by RFC 2434 [4].
Despite the fact that authentication type numbers are allocated
out of an 8-bit number space (as are most values in the telnet
specification) it is not anticipated that the number space is or
will become in danger of being exhausted. However, if this
should become an issue, when over 50% of the number space becomes
allocated, the IANA shall refer allocation requests to either the
IESG or a designated expert for approval. IANA is instructed not
to issue new suboption values without submission of documentation
of their use.
Modifiers
AUTH_WHO_MASK 1
AUTH_CLIENT_TO_SERVER 0
AUTH_SERVER_TO_CLIENT 1
AUTH_HOW_MASK 2
AUTH_HOW_ONE_WAY 0
AUTH_HOW_MUTUAL 2
ENCRYPT_MASK 20
ENCRYPT_OFF 0
ENCRYPT_USING_TELOPT 4
ENCRYPT_AFTER_EXCHANGE 16
ENCRYPT_START_TLS 20
INI_CRED_FWD_MASK 8
INI_CRED_FWD_OFF 0
INI_CRED_FWD_ON 8
2. Command Meanings
This document makes reference to a "server" and a "client". For the
purposes of this document, the "server" is the side of the connection
that performed the passive TCP open (TCP LISTEN state), and the "client" is
the side of the connection that did the active open.
IAC WILL AUTHENTICATION
The client side of the connection sends this command to indicate
that it is willing to send and receive authentication information.
IAC DO AUTHENTICATION
The servers side of the connection sends this command to indicate
that it is willing to send and receive authentication information.
IAC WONT AUTHENTICATION
The client side of the connection sends this command to indicate
that it refuses to send or receive authentication information; the
server side must send this command if it receives a DO
AUTHENTICATION command.
IAC DONT AUTHENTICATION
The server side of the connection sends this command to indicate
that it refuses to send or receive authentication information; the
client side must send this command if it receives a WILL
AUTHENTICATION command.
IAC SB AUTHENTICATION SEND authentication-type-pair-list IAC SE
The sender of this command (the server) requests that the remote
side send authentication information for one of the authentication
types listed in "authentication-type-pair-list". The
"authentication-type-pair-list" is an ordered list of
"authentication-type" pairs. Only the server side (DO
AUTHENTICATION) is allowed to send this.
IAC SB AUTHENTICATION IS authentication-type-pair <auth data> IAC SE
The sender of this command (the client) is sending the
authentication information for authentication type
"authentication-type-pair". Only the client side (WILL
AUTHENTICATION) is allowed to send this.
IAC SB AUTHENTICATION REPLY authentication-type-pair <auth data> IAC
SE
The sender of this command (the server) is sending a reply to the
the authentication information received in a previous IS command.
Only the server side (DO AUTHENTICATION) is allowed to send this.
IAC SB AUTHENTICATION NAME remote-user IAC SE
This optional command is sent to specify the account name on the
remote host that the user wishes to be authorized to use. Note
that authentication may succeed, and the authorization to use a
particular account may still fail. Some authentication mechanisms
may ignore this command. (See Security Considerations.)
The "authentication-type-pair" is two octets, the first is the
authentication type, and the second is a modifier to the type. The
authentication type may or may not include built-in encryption. For
instance, when the Kerberos 5 authentication type is negotiated
encryption must be negotiated with either the Telnet START_TLS or
ENCRYPT options. However, the SSL and KEA_SJ authentication types
provide an encrypted channel as part of a successful Telnet AUTH
option negotiation.
There are currently five one bit fields defined in the modifier. The
first two of these bits are processed as a pair, the AUTH_WHO_MASK
bit and the AUTH_HOW_MASK bit. There are four possible combinations
of these two bits:
AUTH_CLIENT_TO_SERVER
AUTH_HOW_ONE_WAY
The client will send authentication information about the local
user to the server. If the negotiation is successful, the
server will have authenticated the user on the client side of
the connection.
AUTH_SERVER_TO_CLIENT
AUTH_HOW_ONE_WAY
The server will authenticate itself to the client. If the
negotiation is successful, the client will know that it is
connected to the server that it wants to be connected to.
AUTH_CLIENT_TO_SERVER
AUTH_HOW_MUTUAL
The client will send authentication information about the local
user to the server, and then the server will authenticate
itself to the client. If the negotiation is successful, the
server will have authenticated the user on the client side of
the connection, and the client will know that it is connected
to the server that it wants to be connected to.
AUTH_SERVER_TO_CLIENT
AUTH_HOW_MUTUAL
The server will authenticate itself to the client, and then the
client will authenticate itself to the server. If the
negotiation is successful, the client will know that it is
connected to the server that it wants to be connected to, and
the server will know that the client is who it claims to be.
The third and fifth bits in the modifier are the ENCRYPT_MASK
bits. These bits are used to determine if and how encryption
should be enabled. Of the four possible combinations only three
are currently defined:
ENCRYPT_OFF
Encryption will not be used for this session. TELOPT
ENCRYPT SHOULD NOT be negotiated. This mode MUST be used
with all AUTH types that do not provide a shared secret to
be used as a session key.
ENCRYPT_USING_TELOPT
Encryption will be negotiated via the use of TELOPT ENCRYPT.
Immediately after authentication has completed TELOPT
ENCRYPT MUST be negotiated in both directions. This is
required to occur before credentials forwarding; other
telnet options are negotiated; or any user data is
transmitted. A failure to successfully negotiate TELOPT
ENCRYPT in either direction MUST result in immediate session
termination.
ENCRYPT_AFTER_EXCHANGE
Encryption will be activated in both directions immediately
after the successful exchange of the shared secret to be
used as the session key. The encryption algorithm to be
used MUST be implied by the AUTH type.
ENCRYPT_START_TLS
Encryption is provided by TLS which MUST have been negotiated
prior to use of this flag. If TLS has not been previous
negotiated, authentication-type-pairs including this flag
MUST NOT be offered by the server, not accepted by the client.
Authentication methods that support this option MUST verify
the client's and server's TLS Finished Messages as part of the
authentication exchange.
The fourth bit field in the modifier is the INI_CRED_FWD_MASK bit.
This bit is either set to INI_CRED_FWD_ON or INI_CRED_FWD_OFF.
This bit is set by the client to advise the server to expect
forwarded credentials from the client.
INI_CRED_FWD_OFF
The client will not be forwarding credentials to the server.
This mode must be used if the selected authentication method
does not support credentials forwarding.
INI_CRED_FWD_ON
Once authentication, and perhaps encryption, completes, the
client will immediately forward authentication credentials
to the server.
The motivation for this advisory bit is that the server may wish
to wait until the forwarded credentials have been sent before
starting any operating system specific login procedures which may
depend on these credentials. Note that credentials forwarding may
not be supported by all authentication mechanisms. It is a
protocol error to set this bit if the underlying authentication
mechanism does not support credentials forwarding.
Credentials forwarding MUST NOT be performed if
AUTH_CLIENT_TO_SERVER|AUTH_HOW_ONE_WAY was used since the identity
of the server can not be assured. Credentials SHOULD NOT be
forwarded if the telnet connection is not protected using some
encryption or integrity protection services.
Note that older implementations of the telnet authentication
option will not understand the ENCRYPT_MASK and INI_CRED_FWD_MASK
bits. Hence any implementation wishing to offer these bits will
have to offer authentication type pairs with these bits both set
and not set if backwards compatibility is required. (See Security
Considerations.)
3. Default Specification
The default specification for this option is
WONT AUTHENTICATION DONT AUTHENTICATION
meaning there will not be any exchange of authentication information.
4. Motivation
One of the deficiencies of the Telnet protocol is that in order to
log into remote systems, users have to type their passwords, which
are passed in clear text through the network. If the connection
go through untrusted networks, there is the possibility that
passwords will be compromised by someone watching the packets while
in transit.
The purpose of the AUTHENTICATION option is to provide a framework
for the passing of authentication information through the TELNET
session, and a mechanism to enable encryption of the data stream as a
side effect of successful authentication or via subsequent use of the
telnet ENCRYPT option. This means that: 1) the users password will
not be sent in clear text across the network, 2) if the front end
telnet process has the appropriate authentication information, it can
automatically send the information, and the user will not have to
type any password. 3) once authentication has succeeded, the data
stream can be encrypted to provide protection against active attacks.
It is intended that the AUTHENTICATION option be general enough that
it can be used to pass information for any authentication and
encryption system.
5. Implementation Rules
WILL and DO are used only at the beginning of the connection to
obtain and grant permission for future negotiations.
The authentication is only negotiated in one direction; the server
must send the "DO", and the client must send the "WILL". This
restriction is due to the nature of authentication; there are three
possible cases; server authenticates client, client authenticates
server, and server and client authenticate each other. By only
negotiating the option in one direction, and then determining which
of the three cases is being used via the suboption, potential
ambiguity is removed. If the server receives a "DO", it must respond
with a "WONT". If the client receives a "WILL", it must respond with
a "DONT".
Once the two hosts have exchanged a DO and a WILL, the server is free
to request authentication information. In the request, a list of
supported authentication types is sent. Only the server may send
requests ("IAC SB AUTHENTICATION SEND authentication-type-pair-list
IAC SE"). Only the client may transmit authentication information
via the "IAC SB AUTHENTICATION IS authentication-type ... IAC SE"
command. Only the server may send replies ("IAC SB AUTHENTICATION
REPLY authentication-type ... IAC SE"). As many IS and REPLY
suboptions may be exchanged as are needed for the particular
authentication scheme chosen.
If the client does not support any of the authentication types listed
in the authentication-type-pair-list, a type of NULL should be used
to indicate this in the IS reply. Note that if the client responds
with a type of NULL, the server may choose to close the connection.
When the server has concluded that authentication cannot be
negotiated with the client it should send IAC DONT AUTH to the
client.
The order of the authentication types MUST be ordered to indicate a
preference for different authentication types, the first type being
the most preferred, and the last type the least preferred.
As long as the server is WILL AUTH it may request authentication
information at any time. This is done by sending a new list of
supported authentication types. Requesting authentication
information may be done as a way of verifying the validity of the
client's credentials after an extended period of time or to negotiate
a new session key for use during encryption.
7. Integration with TELNET START_TLS option
The Telnet START_TLS option [5] enables the Telnet client and server
to negotiate the use of the TLS protocol to secure the connection.
TLS is most frequently used with X.509 server-side certificates. When
properly verified by the client the TLS session provides strong
encryption and protects against a wide range of passive and active
man in the middle attacks. When certificates are not used or not
verified by the client, the session (although encrypted) is susceptible
to man in the middle attacks. These attacks can be detected by verifying
the TLS Client and Server Finished Messages during the Telnet
AUTHENTICATION protocol exchange. The method for performing this
verification is authentication type specific.
8. User Interface
Normally protocol specifications do not address user interface
specifications. However, due to the fact that the user will probably
want to be able to configure the authentication and
encryption and know whether or not the negotiations succeeded, some
guidance needs to be given to implementors to provide some minimum
level of user control.
The user of the client MUST be able to specify whether or not
authentication is to be used, and whether or not encryption is to used
if the authentication succeeds. There SHOULD be at least four settings,
REQUIRE, PROMPT, WARN and DISABLE. Setting the authentication switch
to REQUIRE means that if the authentication fails, then an
appropriate error message must be displayed and the TELNET connection
must be terminated. Setting the authentication switch to PROMPT
means that if the authentication fails, then an appropriate error
message must be displayed and the user must be prompted for
confirmation before continuing the TELNET session. Setting the
authentication switch to WARN means that if the authentication fails,
then an appropriate error message must be displayed before continuing
the TELNET session. Setting the authentication switch to DISABLE
means that authentication will not be attempted. The encryption
switch SHOULD have the same settings as the authentication switch;
however its settings are only used when authentication succeeds. The
default setting for both switches should be WARN. Both of these
switches may be implemented as a single switch, though having them
separate gives more control to the user.
The server must provide the system administrator the ability to
specify whether or not authentication is required and which
authentication type pairs should be offered to the client and
in what order of preference.
9. Security Considerations
This memo describes a general framework for adding authentication and
encryption to the telnet protocol. The actual authentication
mechanism is described in the authentication suboption
specifications, and the security of the authentication option is
dependent on the strengths and weaknesses of the authentication
suboption.
The ability to negotiate a common authentication mechanism between
client and server is a feature of the authentication option that
should be used with caution. When the negotiation is performed, no
authentication has yet occurred. Therefore each system has no way of
knowing whether or not it is talking to the system it intends. An
intruder could attempt to negotiate the use of an authentication
system which is either weak, or already compromised by the intruder.
It should be noted that the negotiation of the authentication
type pair is not protected, thus allowing an attacker to force the
result of the authentication to the weakest mutually acceptable
method. (For example, even if both sides of the negotiation can
accept a "strong" mechanism and a "40-bit" mechanism, an attacker
could force selection of the "40-bit" mechanism.) An implementation
should therefore only accept an authentication mechanism to be
negotiated if it is willing to trust the resulting channel as being
secure.
If the START_TLS option has not been negotiated and the authentication
type requires that encryption be enabled as a separate optional negotiation
there will be a window of vulnerability from the completion of the
AUTH option until the successful negotiation to activiate bidirectional
encryption. During this window an active attack may be successfully
implemented. An active attack is one where the underlying TCP stream
can be modified or taken over by the active attacker.
The active attack can be prevented if the server only offers
authentication type pairs that include the ENCRYPT_USING_TELOPT or
ENCRYPT_START_TLS bits set in the ENCRYPT_MASK field, since both parties
will agree that an encryption capability must be successfully negotiated.
When the ENCRYPT_USING_TELOPT bit is negotiated, the ENCRYPT option MUST
be negotiated immediately following the successful completion of the
AUTH option.
Authentication types that link the enabling of encryption as a side
effect of successful authentication are not vulnerable to this active
attack. The ENCRYPT_AFTER_EXCHANGE bit allows these authentication types
to optionally negotiate the activation of encryption.
Another opportunity for active attacks is presented when encryption
may be turned on and off without re-authentication. Once encryption
is disabled, an attacker may hijack the telnet stream, and interfere
with attempts to restart encryption. Therefore, a client SHOULD NOT
support the ability to turn off encryption. Once encryption is
disabled, if an attempt to re-enable encryption fails, the client
MUST terminate the telnet connection.
It is important that in all cases the authentication type pair be
integrity protected at the end of the authentication exchange. This
must be specified for each authentication type to ensure that the
result of the telnet authentication option negotiation is agreed to
by both the client and the server. To prevent downgrade attacks
authentication type suboptions SHOULD (if possible) include either
the entire auth-type pair list; or all of the telnet authentication
negotiation exchanges in the integrity checksum.
Each side MUST verify the consistency of the auth-type-pairs in each
message received. Any variation in the auth-type-pair MUST be
treated as a fatal protocol error.
It should also be noted that the transmission of the username in
the IAC SB AUTHENTICATION NAME name IAC SE message is not protected.
Implementations should verify the value by a secure method before
using this untrusted value when there is a possibility of a man in
the middle attack. One method of verifying this value is for the
server to request the USER using the NEW ENVIRONMENT option [6].
9. Example
The following is an example of use of the option:
Client Server
IAC DO AUTHENTICATION
IAC WILL AUTHENTICATION
[ The server is now free to request authentication information. ]
IAC SB AUTHENTICATION SEND
KERBEROS_V5 CLIENT|MUTUAL
KERBEROS_V5 CLIENT|ONE_WAY IAC
SE
[ The server has requested mutual Kerberos authentication, but is
willing to do just one-way Kerberos authentication. The client
will now respond with the name of the user that it wants to log
in as, and the Kerberos ticket. ]
IAC SB AUTHENTICATION NAME "joe"
IAC SE
IAC SB AUTHENTICATION IS
KERBEROS_V5 CLIENT|MUTUAL AUTH 4
7 1 67 82 65 89 46 67 7 9 77 0
48 24 49 244 109 240 50 208 43
35 25 116 104 44 167 21 201 224
229 145 20 2 244 213 220 33 134
148 4 251 249 233 229 152 77 2
109 130 231 33 146 190 248 1 9
31 95 94 15 120 224 0 225 76 205
70 136 245 190 199 147 155 13
IAC SE
[ The server responds with an ACCEPT command to state that the
authentication was successful. ]
IAC SB AUTHENTICATION REPLY
KERBEROS_V5 CLIENT|MUTUAL ACCEPT
IAC SE
[ Next, the client sends across a CHALLENGE to verify that it is
really talking to the right server. ]
IAC SB AUTHENTICATION IS
KERBEROS_V5 CLIENT|MUTUAL
CHALLENGE xx xx xx xx xx xx xx
xx IAC SE
[ Lastly, the server sends across a RESPONSE to prove that it
really is the right server. ]
IAC SB AUTHENTICATION REPLY
KERBEROS_V5 CLIENT|MUTUAL
RESPONSE yy yy yy yy yy yy yy yy
IAC SE
The following is an example of use of the option with encryption
negotiated via telnet ENCRYPT:
Client Server
IAC DO AUTHENTICATION
IAC WILL AUTHENTICATION
[ The server is now free to request authentication information. ]
IAC SB AUTHENTICATION SEND
KERBEROS_V5
CLIENT|MUTUAL|ENCRYPT_USING_TELOPT
KERBEROS_V5 CLIENT|ONE_WAY IAC
SE
[ The server has requested mutual Kerberos authentication, but is
willing to do just one-way Kerberos authentication. In both
cases it is willing to encrypt the data stream. The client
will now respond with the name of the user that it wants to log
in as, and the Kerberos ticket. ]
IAC SB AUTHENTICATION NAME "joe"
IAC SE
IAC SB AUTHENTICATION IS
KERBEROS_V5
CLIENT|MUTUAL|ENCRYPT_USING_TELOPT
AUTH 4 7 1 67 82 65 89 46 67 7 9
77 0 48 24 49 244 109 240 50 208
43 35 25 116 104 44 167 21 201
224 229 145 20 2 244 213 220 33
134 148 4 251 249 233 229 152 77
2 109 130 231 33 146 190 248 1 9
31 95 94 15 120 224 0 225 76 205
70 136 245 190 199 147 155 13
IAC SE
[ The server responds with an ACCEPT command to state that the
authentication was successful. ]
IAC SB AUTHENTICATION REPLY
KERBEROS_V5
CLIENT|MUTUAL|ENCRYPT_USING_TELOPT
ACCEPT IAC SE
[ Next, the client sends across a CHALLENGE to verify that it is
really talking to the right server. ]
IAC SB AUTHENTICATION IS
KERBEROS_V5
CLIENT|MUTUAL|ENCRYPT_USING_TELOPT
CHALLENGE xx xx xx xx xx xx xx
xx IAC SE
[ The server sends across a RESPONSE to prove that it really is
the right server. ]
IAC SB AUTHENTICATION REPLY
KERBEROS_V5
CLIENT|MUTUAL|ENCRYPT_USING_TELOPT
RESPONSE yy yy yy yy yy yy yy yy
IAC SE
[ At this point, the client and server begin to negotiate the
telnet ENCRYPT option in each direction for a secure channel.
If the option fails in either direction for any reason the
connection must be immediately terminated. ]
The following is an example of use of the option with integrated
encryption:
Client Server
IAC DO AUTHENTICATION
IAC WILL AUTHENTICATION
[ The server is now free to request authentication information. ]
IAC SB AUTHENTICATION SEND
KEA_SJ
CLIENT|MUTUAL|ENCRYPT_AFTER_EXCHANGE
IAC SE
[ The server has requested mutual KEA authentication with
SKIPJACK encryption. The client will now respond with the name
of the user that it wants to log in as and the KEA cert. ]
IAC SB AUTHENTICATION NAME "joe"
IAC SE IAC SB AUTHENTICATION IS
KEA_SJ
CLIENT|MUTUAL|ENCRYPT_AFTER_EXCHANGE
'1' CertA||Ra IAC SE
[ The server responds with its KEA Cert. ]
IAC SB AUTHENTICATION REPLY
KEA_SJ
CLIENT|MUTUAL|ENCRYPT_AFTER_EXCHANGE
'2'
CertB||Rb||IVb||Encrypt(NonceB)
IAC SE
[ Next, the client sends across a CHALLENGE to verify that it is
really talking to the right server. ]
IAC SB AUTHENTICATION IS KEA_SJ
CLIENT|MUTUAL|ENCRYPT_AFTER_EXCHANGE
'3' IVa||Encrypt( NonceB xor
0x0C18 || NonceA ) IAC SE
[ At this point, the client begins to encrypt the outgoing data
stream, and the server, after receiving this command, begins to
decrypt the incoming data stream. Lastly, the server sends
across a RESPONSE to prove that it really is the right server. ]
IAC SB AUTHENTICATION REPLY
KEA_SJ
CLIENT|MUTUAL|ENCRYPT_AFTER_EXCHANGE
'4' Encrypt( NonceA xor 0x0C18 )
IAC SE
[ At this point, the server begins to encrypt its outgoing data
stream, and the client, after receiving this command, begins to
decrypt its incoming data stream. ]
It is expected that any implementation that supports the Telnet
AUTHENTICATION option will support all of this specification.
10. Acknowledgements
Many people have worked on this document over the span of many years.
Dave Borman was a document editor and author of much of the original
text. Other folks who have contributed ideas and suggestions to this
text include: David Carrel, Jeff Schiller, and Richard Basch.
11. References
[1] Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD
8, RFC 854, May 1983.
[2] T'so, T. and Altman, J., "Telnet Authentication Option", RFC 2941,
September 2000.
[3] Ts'o, T., "Telnet Data Encryption Option", RFC 2946, September
2000.
[4] Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[5] Altman, J. and Boe, M., "TLS-based Telnet Security",
draft-ietf-tn3270e-telnet-tls-??.txt.
[6] Alexander, S., "Telnet Environment Option", RFC 1572, January 1994
12. Authors' Addresses
Theodore Ts'o, Editor
43 Pleasant St.
Medford, MA 02155
Phone: (781) 391-3464
EMail: tytso@mit.edu
Jeffrey Altman
Columbia University
Watson Hall Room 716
612 West 115th Street
New York NY 10025
Phone: +1 (212) 854-1344
EMail: jaltman@columbia.edu
Mailing List: telnet-wg@BSDI.COM
13. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.