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Text File | 1994-05-01 | 16.1 KB | 449 lines

SUMMARY OF CHANGES BETWEEN SENDMAIL V5 and V8 @(#)CHANGES-R5-R8 8.1 (Berkeley) 2/26/94 The following is a summary of the changes between the last commonly available version of sendmail from Berkeley (5.67) and the latest version (8.6). I can't guarantee that it is complete. Many of these are ideas that had been tried in IDA, albeit many of them with a more general syntax. Connection Caching Instead of closing SMTP connections immediately, open connections are cached for possible future use. There is a limit to the number of simultaneous open connections and the idle time of any individual connection. This is of best help during queue processing (since there is the potential of many different messages going to one site), although it can also help when processing MX records which aren't handled by MX Piggybacking. MX Piggybacking If two hosts with different names in a single message happen to have the same set of MX hosts, they can be sent in the same transaction. Version 8 notices this and tries to batch the messages. For example, if two sites ``foo.com'' and ``bar.com'' are both served by UUNET, they will have the same set of MX hosts and will be sent in one transaction. UUNET will then split the message and send it to the two individual hosts. RFC 1123 Changes A number of changes have been made to make sendmail ``conditionally compliant'' (that is, it satisfies all of the MUST clauses and most but not all of the SHOULD clauses in RFC 1123). The major areas of change are (numbers are RFC 1123 section numbers): 5.2.7 Response to RCPT command is fast. Previously, sendmail expanded all aliases as far as it could -- this could take a very long time, particularly if there were name server delays. Version 8 only checks for the existence of an alias and does the expansion later. 5.2.8 Numeric IP addresses are logged in Received: lines. This helps tracing spoofed messages. 5.2.17 Self domain literal is properly handled. Previously, if someone sent to user@[a.b.c.d], where a.b.c.d is your IP address, the mail would probably be rejected. Version 8 special cases these addresses. 5.3.2 Better control over individual timeouts. RFC 821 specified no timeouts. Older versions of sendmail had a single timeout, typically set to two hours. Version 8 allows the configuration file to set timeouts for various SMTP commands individually. 5.3.3 Error messages are sent as From:<>. This was urged by RFC 821 and reiterated by RFC 1123, but older versions of sendmail never really did it properly. Version 8 does. However, some systems cannot handle this perfectly legal address; if necessary, you can create a special mailer that uses the `g' flag to disable this. 5.3.3 Error messages are never sent to <>. Previously, sendmail was happy to send responses-to-responses which sometimes resulted in responses-to-responses-to-responses which resulted in .... you get the idea. 5.3.3 Route-addrs (the ugly ``<@hosta,@hostb:user@hostc>'' syntax) are pruned. RFC 821 urged the use of this bletcherous syntax. RFC 1123 has seen the light and officially deprecates them, further urging that you eliminate all but ``user@hostc'' should you receive one of these things. Version 8 is slightly more generous than the standards suggest; instead of stripping off all the route addressees, it only strips hosts off up to the one before the last one known to DNS, thus allowing you to have pseudo-hosts such as foo.BITNET. The 'R' option will turn this off. The areas in which sendmail is not ``unconditionally compliant'' are: 5.2.6 Sendmail does do header munging. 5.2.10 Sendmail doesn't always use the exact SMTP message text from RFC 821. This is a rather silly requirement. 5.3.1.1 Sendmail doesn't guarantee only one connect for each host on queue runs. Connection caching gives you most of this, but it does not provide a guarantee. 5.3.1.1 Sendmail doesn't always provide an adequate limit on concurrency. That is, there can be several independent sendmails running at once. My feeling is that doing an absolute limit would be a mistake (it might result in lost mail). However, if you use the XLA contributed software, most of this will be guaranteed (but I don't guarantee the guarantee). Extended SMTP Support Version 8 includes both sending and receiving support for Extended SMTP support as defined by RFC 1425 (basic) and RFC 1427 (SIZE); and limited support for RFC 1426 (BODY). Eight-Bit Clean Previous versions of sendmail used the 0200 bit for quoting. This version avoids that use. However, for compatibility with RFC 822, you can set option `7' to get seven bit stripping. Individual mailers can still produce seven bit out put using the `7' mailer flag. User Database The user database is an as-yet experimental attempt to provide unified large-site name support. We are installing it at Berkeley; future versions may show significant modifications. The user database allows you to map both incoming and outgoing addresses, much like IDA. However, the interface set is still better with IDA. Improved BIND Support The BIND support, particularly for MX records, had a number of annoying ``features'' which have been removed in this release. In particular, these more tightly bind (pun intended) the name server to sendmail, so that the name server resolution rules are incorporated directly into sendmail. The major change has been that the $[ ... $] operator didn't fully qualify names that were in DNS as A or MX records. Version 8 does this qualification. Keyed Files Generalized keyed files is an idea taken directly from IDA sendmail (albeit with a completely different implementation). They can be useful on large sites. Version 8 includes an "NIS" map class to support NIS/YP maps. Multi-Word Classes & Macros in Classes Classes can now be multiple words. For example, CShofmann.CS.Berkeley.EDU allows you to match the entire string ``hofmann.CS.Berkeley.EDU'' using the single construct ``$=S''. Class definitions are now allowed to include macros -- for example: Cw$k is legal. Deferred Macro Expansion The $&x construct has been adopted from IDA. IDENT Protocol Support The IDENT protocol as defined in RFC 1413 is supported. Parsing Bug Fixes A number of small bugs having to do with things like backslash-escaped quotes inside of comments have been fixed. Separate Envelope/Header Processing Since the From: line is passed in separately from the envelope sender, these have both been made visible; the $g macro is set to the envelope sender during processing of mailer argument vectors and the header sender during processing of headers. It is also possible to specify separate per-mailer envelope and header processing. The SenderRWSet and RecipientRWset arguments for mailers can be specified as ``envelope/header'' to give different rewritings for envelope versus header addresses. Owner-List Propagates to Envelope When an alias has an associated owner-list name, that alias is used to change the envelope sender address. This will cause downstream errors to be returned to that owner. Dynamic Header Allocation The fixed size limit on header lines has been eliminated. New Command Line Flags The -B flag has been added to pass in body type information. The -p flag has been added to pass in protocol information. The -X flag has been added to allow logging of all protocol in and out of sendmail for debugging. Enhanced Command Line Flags The -q flag can limit limit a queue run to specific recipients, senders, or queue ids using -qRsubstring, -qSsubstring, or -qIsubstring respectively. New and Old Configuration Line Types The `T' (Trusted users) configuration line has been deleted. It will still be accepted but will be ignored. The `K' line has been added to declare database maps. The `V' line has been added to declare the configuration version level. The `M' (mailer) line takes a D= field to specify execution directory. New Options Several new options have been added, many to support new features, others to allow tuning that was previously available only by recompiling. Briefly: b Insist on a minimum number of disk blocks. C Delivery checkpoint interval. Checkpoint the queue (to avoid duplicate deliveries) every C addresses. E Default error message. This message (or the contents of the indicated file) are prepended to error messages. G Enable GECOS matching. If you can't find a local user name and this option is enabled, do a sequential scan of the passwd file to match against full names. Previously a compile option. h Maximum hop count. Previously this was compiled in. j Send errors in MIME-encapsulated format. J Forward file path. Where to search for .forward files -- defaults to $HOME/.forward. k Connection cache size. The total number of connections that will be kept open at any time. K Connection cache lifetime. The amount of time any connection will be permitted to sit idle. l Enable Errors-To: header. These headers violate RFC 1123; this option is included to provide back compatibility with old versions of sendmail. O Incoming daemon options (e.g., use alternate SMTP port). p Privacy options. These can be used to make your SMTP server less friendly. R Don't prune route-addrs. Normally, if version 8 sees an address like "<@hostA,@hostB:user@hostC>, sendmail will try to strip off as much as it can (up to user@hostC) as suggested by RFC 1123. This option disables that behaviour. U User database spec. This is still experimental. V Fallback ``MX'' host. This can be thought of as an MX host that applies to all addresses that has a very high preference value (that is, use it only if everything else fails). w If set, assume that if you are the best MX host for a host, you should send directly to that host. This is intended for compatibility with UIUC sendmail, and may have some use on firewalls. 7 Do not run eight bit clean. Technically, you have to assert this option to be RFC 821 compatible. Extended Options The `r' (read timeout), `I' (use BIND), and `T' (queue timeout) options have been extended to pass in more information. The `A' (alias file) option has been extended to allow multiple alias files of different types. New Mailer Keyletters L= Set the allowable line length. In V5, the L mailer flag implied a line length limit of 990 characters; this is now settable to an arbitrary value. New Mailer Flags F=a Try to use ESMTP. It will fall back to SMTP if the initial EHLO packet is rejected. F=b Ensure a blank line at the end of messages. Useful on the *file* mailer. F=c Strip all comments from addresses; this should only be used as a last resort when dealing with cranky mailers. F=g Never use the null sender as the envelope sender, even when running SMTP. This violates RFC 1123. F=7 Strip all output to this mailer to 7 bits. Changed Mailer Flags F=L Used to set the line limit to 990 bytes for SMTP compatibility. It now does that only if the L= keyletter is not specified. This flag is obsolete and should not be used. New or Changed Pre-Defined Macros $k UUCP node name from uname(2). $m Domain part of our full hostname. $_ RFC 1413-provided sender address. $w Previously was sometimes the full domain name, sometimes just the first word. Now guaranteed to be the first word of the domain name (i.e., the host name). $j Previously had to be defined -- it is now predefined to be the full domain name, if that can be determined. That is, it is equivalent to $w.$m. New Classes $=k Initialized to contain $k. New LHS Token Version 8 allows `$@' on the Left Hand Side of an `R' line to match zero tokens. This is intended to be used to match the null input. Bigger Defaults Version 8 allows up to 100 rulesets instead of 30. It is recommended that rulesets 0-9 be reserved for sendmail's dedicated use in future releases. The total number of MX records that can be used has been raised to 20. The number of queued messages that can be handled at one time has been raised from 600 to 1000. Different Default Tuning Parameters Version 8 has changed the default parameters for tuning queue costs to make the number of recipients more important than the size of the message (for small messages). This is reasonable if you are connected with reasonably fast links. Auto-Quoting in Addresses Previously, the ``Full Name <email address>'' syntax would generate incorrect protocol output if ``Full Name'' had special characters such as dot. This version puts quotes around such names. Symbolic Names On Error Mailer Several names have been built in to the $@ portion of the $#error mailer. For example: $#error $@NOHOST $: Host unknown New Built-In Mailers Two new mailers, *file* and *include*, are included to define options when mailing to a file or a :include: file respectively. Previously these were overloaded on the local mailer. SMTP VRFY Doesn't Expand Previous versions of sendmail treated VRFY and EXPN the same. In this version, VRFY doesn't expand aliases or follow .forward files. As an optimization, if you run with your default delivery mode being queue-only, the RCPT command will also not chase aliases and .forward files. It will chase them when it processes the queue. This speeds up RCPT processing. [IPC] Mailers Allow Multiple Hosts When an address resolves to a mailer that has ``[IPC]'' as its ``Path'', the $@ part (host name) can be a colon-separated list of hosts instead of a single hostname. This asks sendmail to search the list for the first entry that is available exactly as though it were an MX record. The intent is to route internal traffic through internal networks without publishing an MX record to the net. MX expansion is still done on the individual items. Aliases Extended The implementation has been merged with maps. Among other things, this supports multiple alias files and NIS-based aliases. For example: OA/etc/aliases,nis:mail.aliases Portability and Security Enhancements A number of internal changes have been made to enhance portability. Several fixes have been made to increase the paranoia factor. In particular, the permissions required for .forward and :include: files have been tightened up considerably. V5 would pretty much read any file it could get to as root, which exposed some security holes. V8 insists that all directories leading up to the .forward or :include: file be searchable ("x" permission) by the controlling user" (defined below), that the file itself be readable by the controlling user, and that .forward files be owned by the user who is being forwarded to or root. The "controlling user" is the user on whose behalf the mail is being delivered. For example, if you mail to "user1" then the controlling user for ~user1/.forward and any mailers invoked by that .forward file, including :include: files. Previously, anyone who had a home directory could create a .forward could forward to a program. Now, sendmail checks to make sure that they have an "approved shell", that is, a shell listed in the /etc/shells file. Miscellaneous Enhancements Sendmail writes a /etc/sendmail.pid file with the current process id and the current invocation flags. Two people using the same program (e.g., submit) are considered "different" so that duplicate elimination doesn't delete one of them. For example, two people forwarding their email to |submit will be treated as two recipients. The mailstats program prints mailer names and gets the location of the sendmail.st file from /etc/sendmail.cf. Many minor bugs have been fixed, such as handling of backslashes inside of quotes. A hook has been added to allow rewriting of local addresses after aliasing.