Check return values of setgid/setuid.
[exim.git] / doc / doc-txt / NewStuff
1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.176 2010/06/14 18:51:10 pdp Exp $
3 New Features in Exim
4 --------------------
6 This file contains descriptions of new features that have been added to Exim.
7 Before a formal release, there may be quite a lot of detail so that people can
8 test from the snapshots or the CVS before the documentation is updated. Once
9 the documentation is updated, this file is reduced to a short list.
12 Version 4.74
13 ------------
15 1. SECURITY FIX: privilege escalation flaw fixed. On Linux (and only Linux)
16 the flaw permitted the Exim run-time user to cause root to append to
17 arbitrary files of the attacker's choosing, with the content based
18 on content supplied by the attacker.
20 2. Exim now supports loading some lookup types at run-time, using your
21 platform's dlopen() functionality. This has limited platform support
22 and the intention is not to support every variant, it's limited to
23 dlopen(). This permits the main Exim binary to not be linked against
24 all the libraries needed for all the lookup types.
27 Version 4.73
28 ------------
30 NOTE: this version is not guaranteed backwards-compatible, please read the
31 items below carefully
33 1. A new main configuration option, "openssl_options", is available if Exim
34 is built with SSL support provided by OpenSSL. The option allows
35 administrators to specify OpenSSL options to be used on connections;
36 typically this is to set bug compatibility features which the OpenSSL
37 developers have not enabled by default. There may be security
38 consequences for certain options, so these should not be changed
39 frivolously.
41 2. A new pipe transport option, "permit_coredumps", may help with problem
42 diagnosis in some scenarios. Note that Exim is typically installed as
43 a setuid binary, which on most OSes will inhibit coredumps by default,
44 so that safety mechanism would have to be overriden for this option to
45 be able to take effect.
47 3. ClamAV 0.95 is now required for ClamAV support in Exim, unless
48 Local/Makefile sets: WITH_OLD_CLAMAV_STREAM=yes
49 Note that this switches Exim to use a new API ("INSTREAM") and a future
50 release of ClamAV will remove support for the old API ("STREAM").
52 The av_scanner option, when set to "clamd", now takes an optional third
53 part, "local", which causes Exim to pass a filename to ClamAV instead of
54 the file content. This is the same behaviour as when clamd is pointed at
55 a Unix-domain socket. For example:
57 av_scanner = clamd: 1234:local
59 ClamAV's ExtendedDetectionInfo response format is now handled.
61 4. There is now a -bmalware option, restricted to admin users. This option
62 takes one parameter, a filename, and scans that file with Exim's
63 malware-scanning framework. This is intended purely as a debugging aid
64 to ensure that Exim's scanning is working, not to replace other tools.
65 Note that the ACL framework is not invoked, so if av_scanner references
66 ACL variables without a fallback then this will fail.
68 5. There is a new expansion operator, "reverse_ip", which will reverse IP
69 addresses; IPv4 into dotted quad, IPv6 into dotted nibble. Examples:
71 ${reverse_ip:}
72 ->
73 ${reverse_ip:2001:0db8:c42:9:1:abcd:}
74 ->
76 6. There is a new ACL control called "debug", to enable debug logging.
77 This allows selective logging of certain incoming transactions within
78 production environments, with some care. It takes two options, "tag"
79 and "opts"; "tag" is included in the filename of the log and "opts"
80 is used as per the -d<options> command-line option. Examples, which
81 don't all make sense in all contexts:
83 control = debug
84 control = debug/tag=.$sender_host_address
85 control = debug/opts=+expand+acl
86 control = debug/tag=.$message_exim_id/opts=+expand
88 7. It has always been implicit in the design and the documentation that
89 "the Exim user" is not root. src/EDITME said that using root was
90 "very strongly discouraged". This is not enough to keep people from
91 shooting themselves in the foot in days when many don't configure Exim
92 themselves but via package build managers. The security consequences of
93 running various bits of network code are severe if there should be bugs in
94 them. As such, the Exim user may no longer be root. If configured
95 statically, Exim will refuse to build. If configured as ref:user then Exim
96 will exit shortly after start-up. If you must shoot yourself in the foot,
97 then henceforth you will have to maintain your own local patches to strip
98 the safeties off.
100 8. There is a new expansion operator, bool_lax{}. Where bool{} uses the ACL
101 condition logic to determine truth/failure and will fail to expand many
102 strings, bool_lax{} uses the router condition logic, where most strings
103 do evaluate true.
104 Note: bool{00} is false, bool_lax{00} is true.
106 9. Routers now support multiple "condition" tests,
108 10. There is now a runtime configuration option "tcp_wrappers_daemon_name".
109 Setting this allows an admin to define which entry in the tcpwrappers
110 config file will be used to control access to the daemon. This option
111 is only available when Exim is built with USE_TCP_WRAPPERS. The
112 default value is set at build time using the TCP_WRAPPERS_DAEMON_NAME
113 build option.
115 11. [POSSIBLE CONFIG BREAKAGE] The default value for system_filter_user is now
116 the Exim run-time user, instead of root.
118 12. [POSSIBLE CONFIG BREAKAGE] ALT_CONFIG_ROOT_ONLY is no longer optional and
119 is forced on. This is mitigated by the new build option
120 TRUSTED_CONFIG_LIST which defines a list of configuration files which
121 are trusted; one per line. If a config file is owned by root and matches
122 a pathname in the list, then it may be invoked by the Exim build-time
123 user without Exim relinquishing root privileges.
125 13. [POSSIBLE CONFIG BREAKAGE] The Exim user is no longer automatically
126 trusted to supply -D<Macro[=Value]> overrides on the command-line. Going
127 forward, we recommend using TRUSTED_CONFIG_LIST with shim configs that
128 include the main config. As a transition mechanism, we are temporarily
129 providing a work-around: the new build option WHITELIST_D_MACROS provides
130 a colon-separated list of macro names which may be overriden by the Exim
131 run-time user. The values of these macros are constrained to the regex
132 ^[A-Za-z0-9_/.-]*$ (which explicitly does allow for empty values).
135 Version 4.72
136 ------------
138 1. TWO SECURITY FIXES: one relating to mail-spools which are globally
139 writable, the other to locking of MBX folders (not mbox).
141 2. MySQL stored procedures are now supported.
143 3. The dkim_domain transport option is now a list, not a single string, and
144 messages will be signed for each element in the list (discarding
145 duplicates).
147 4. The 4.70 release unexpectedly changed the behaviour of dnsdb TXT lookups
148 in the presence of multiple character strings within the RR. Prior to 4.70,
149 only the first string would be returned. The dnsdb lookup now, by default,
150 preserves the pre-4.70 semantics, but also now takes an extended output
151 separator specification. The separator can be followed by a semicolon, to
152 concatenate the individual text strings together with no join character,
153 or by a comma and a second separator character, in which case the text
154 strings within a TXT record are joined on that second character.
155 Administrators are reminded that DNS provides no ordering guarantees
156 between multiple records in an RRset. For example:
158 foo.example. IN TXT "a" "b" "c"
159 foo.example. IN TXT "d" "e" "f"
161 ${lookup dnsdb{>/ txt=foo.example}} -> "a/d"
162 ${lookup dnsdb{>/; txt=foo.example}} -> "def/abc"
163 ${lookup dnsdb{>/,+ txt=foo.example}} -> "a+b+c/d+e+f"
166 Version 4.70 / 4.71
167 -------------------
169 1. Native DKIM support without an external library.
170 (Note that if no action to prevent it is taken, a straight upgrade will
171 result in DKIM verification of all signed incoming emails. See spec
172 for details on conditionally disabling)
174 2. Experimental DCC support via dccifd (contributed by Wolfgang Breyha).
176 3. There is now a bool{} expansion condition which maps certain strings to
177 true/false condition values (most likely of use in conjunction with the
178 and{} expansion operator).
180 4. The $spam_score, $spam_bar and $spam_report variables are now available
181 at delivery time.
183 5. exim -bP now supports "macros", "macro_list" or "macro MACRO_NAME" as
184 options, provided that Exim is invoked by an admin_user.
186 6. There is a new option gnutls_compat_mode, when linked against GnuTLS,
187 which increases compatibility with older clients at the cost of decreased
188 security. Don't set this unless you need to support such clients.
190 7. There is a new expansion operator, ${randint:...} which will produce a
191 "random" number less than the supplied integer. This randomness is
192 not guaranteed to be cryptographically strong, but depending upon how
193 Exim was built may be better than the most naive schemes.
195 8. Exim now explicitly ensures that SHA256 is available when linked against
196 OpenSSL.
198 9. The transport_filter_timeout option now applies to SMTP transports too.
201 Version 4.69
202 ------------
204 1. Preliminary DKIM support in Experimental.
207 Version 4.68
208 ------------
210 1. The body_linecount and body_zerocount C variables are now exported in the
211 local_scan API.
213 2. When a dnslists lookup succeeds, the key that was looked up is now placed
214 in $dnslist_matched. When the key is an IP address, it is not reversed in
215 this variable (though it is, of course, in the actual lookup). In simple
216 cases, for example:
218 deny dnslists = spamhaus.example
220 the key is also available in another variable (in this case,
221 $sender_host_address). In more complicated cases, however, this is not
222 true. For example, using a data lookup might generate a dnslists lookup
223 like this:
225 deny dnslists = spamhaus.example/<|||...
227 If this condition succeeds, the value in $dnslist_matched might be
228 (for example).
230 3. Authenticators now have a client_condition option. When Exim is running as
231 a client, it skips an authenticator whose client_condition expansion yields
232 "0", "no", or "false". This can be used, for example, to skip plain text
233 authenticators when the connection is not encrypted by a setting such as:
235 client_condition = ${if !eq{$tls_cipher}{}}
237 Note that the 4.67 documentation states that $tls_cipher contains the
238 cipher used for incoming messages. In fact, during SMTP delivery, it
239 contains the cipher used for the delivery. The same is true for
240 $tls_peerdn.
242 4. There is now a -Mvc <message-id> option, which outputs a copy of the
243 message to the standard output, in RFC 2822 format. The option can be used
244 only by an admin user.
246 5. There is now a /noupdate option for the ratelimit ACL condition. It
247 computes the rate and checks the limit as normal, but it does not update
248 the saved data. This means that, in relevant ACLs, it is possible to lookup
249 the existence of a specified (or auto-generated) ratelimit key without
250 incrementing the ratelimit counter for that key.
252 In order for this to be useful, another ACL entry must set the rate
253 for the same key somewhere (otherwise it will always be zero).
255 Example:
257 acl_check_connect:
258 # Read the rate; if it doesn't exist or is below the maximum
259 # we update it below
260 deny ratelimit = 100 / 5m / strict / noupdate
261 log_message = RATE: $sender_rate / $sender_rate_period \
262 (max $sender_rate_limit)
264 [... some other logic and tests...]
266 warn ratelimit = 100 / 5m / strict / per_cmd
267 log_message = RATE UPDATE: $sender_rate / $sender_rate_period \
268 (max $sender_rate_limit)
269 condition = ${if le{$sender_rate}{$sender_rate_limit}}
271 accept
273 6. The variable $max_received_linelength contains the number of bytes in the
274 longest line that was received as part of the message, not counting the
275 line termination character(s).
277 7. Host lists can now include +ignore_defer and +include_defer, analagous to
278 +ignore_unknown and +include_unknown. These options should be used with
279 care, probably only in non-critical host lists such as whitelists.
281 8. There's a new option called queue_only_load_latch, which defaults true.
282 If set false when queue_only_load is greater than zero, Exim re-evaluates
283 the load for each incoming message in an SMTP session. Otherwise, once one
284 message is queued, the remainder are also.
286 9. There is a new ACL, specified by acl_smtp_notquit, which is run in most
287 cases when an SMTP session ends without sending QUIT. However, when Exim
288 itself is is bad trouble, such as being unable to write to its log files,
289 this ACL is not run, because it might try to do things (such as write to
290 log files) that make the situation even worse.
292 Like the QUIT ACL, this new ACL is provided to make it possible to gather
293 statistics. Whatever it returns (accept or deny) is immaterial. The "delay"
294 modifier is forbidden in this ACL.
296 When the NOTQUIT ACL is running, the variable $smtp_notquit_reason is set
297 to a string that indicates the reason for the termination of the SMTP
298 connection. The possible values are:
300 acl-drop Another ACL issued a "drop" command
301 bad-commands Too many unknown or non-mail commands
302 command-timeout Timeout while reading SMTP commands
303 connection-lost The SMTP connection has been lost
304 data-timeout Timeout while reading message data
305 local-scan-error The local_scan() function crashed
306 local-scan-timeout The local_scan() function timed out
307 signal-exit SIGTERM or SIGINT
308 synchronization-error SMTP synchronization error
309 tls-failed TLS failed to start
311 In most cases when an SMTP connection is closed without having received
312 QUIT, Exim sends an SMTP response message before actually closing the
313 connection. With the exception of acl-drop, the default message can be
314 overridden by the "message" modifier in the NOTQUIT ACL. In the case of a
315 "drop" verb in another ACL, it is the message from the other ACL that is
316 used.
318 10. For MySQL and PostgreSQL lookups, it is now possible to specify a list of
319 servers with individual queries. This is done by starting the query with
320 "servers=x:y:z;", where each item in the list may take one of two forms:
322 (1) If it is just a host name, the appropriate global option (mysql_servers
323 or pgsql_servers) is searched for a host of the same name, and the
324 remaining parameters (database, user, password) are taken from there.
326 (2) If it contains any slashes, it is taken as a complete parameter set.
328 The list of servers is used in exactly the same was as the global list.
329 Once a connection to a server has happened and a query has been
330 successfully executed, processing of the lookup ceases.
332 This feature is intended for use in master/slave situations where updates
333 are occurring, and one wants to update a master rather than a slave. If the
334 masters are in the list for reading, you might have:
336 mysql_servers = slave1/db/name/pw:slave2/db/name/pw:master/db/name/pw
338 In an updating lookup, you could then write
340 ${lookup mysql{servers=master; UPDATE ...}
342 If, on the other hand, the master is not to be used for reading lookups:
344 pgsql_servers = slave1/db/name/pw:slave2/db/name/pw
346 you can still update the master by
348 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...}
350 11. The message_body_newlines option (default FALSE, for backwards
351 compatibility) can be used to control whether newlines are present in
352 $message_body and $message_body_end. If it is FALSE, they are replaced by
353 spaces.
356 Version 4.67
357 ------------
359 1. There is a new log selector called smtp_no_mail, which is not included in
360 the default setting. When it is set, a line is written to the main log
361 whenever an accepted SMTP connection terminates without having issued a
362 MAIL command.
364 2. When an item in a dnslists list is followed by = and & and a list of IP
365 addresses, the behaviour was not clear when the lookup returned more than
366 one IP address. This has been solved by the addition of == and =& for "all"
367 rather than the default "any" matching.
369 3. Up till now, the only control over which cipher suites GnuTLS uses has been
370 for the cipher algorithms. New options have been added to allow some of the
371 other parameters to be varied.
373 4. There is a new compile-time option called ENABLE_DISABLE_FSYNC. When it is
374 set, Exim compiles a runtime option called disable_fsync.
376 5. There is a new variable called $smtp_count_at_connection_start.
378 6. There's a new control called no_pipelining.
380 7. There are two new variables called $sending_ip_address and $sending_port.
381 These are set whenever an SMTP connection to another host has been set up.
383 8. The expansion of the helo_data option in the smtp transport now happens
384 after the connection to the server has been made.
386 9. There is a new expansion operator ${rfc2047d: that decodes strings that
387 are encoded as per RFC 2047.
389 10. There is a new log selector called "pid", which causes the current process
390 id to be added to every log line, in square brackets, immediately after the
391 time and date.
393 11. Exim has been modified so that it flushes SMTP output before implementing
394 a delay in an ACL. It also flushes the output before performing a callout,
395 as this can take a substantial time. These behaviours can be disabled by
396 obeying control = no_delay_flush or control = no_callout_flush,
397 respectively, at some earlier stage of the connection.
399 12. There are two new expansion conditions that iterate over a list. They are
400 called forany and forall.
402 13. There's a new global option called dsn_from that can be used to vary the
403 contents of From: lines in bounces and other automatically generated
404 messages ("delivery status notifications" - hence the name of the option).
406 14. The smtp transport has a new option called hosts_avoid_pipelining.
408 15. By default, exigrep does case-insensitive matches. There is now a -I option
409 that makes it case-sensitive.
411 16. A number of new features ("addresses", "map", "filter", and "reduce") have
412 been added to string expansions to make it easier to process lists of
413 items, typically addresses.
415 17. There's a new ACL modifier called "continue". It does nothing of itself,
416 and processing of the ACL always continues with the next condition or
417 modifier. It is provided so that the side effects of expanding its argument
418 can be used.
420 18. It is now possible to use newline and other control characters (those with
421 values less than 32, plus DEL) as separators in lists.
423 19. The exigrep utility now has a -v option, which inverts the matching
424 condition.
426 20. The host_find_failed option in the manualroute router can now be set to
427 "ignore".
430 Version 4.66
431 ------------
433 No new features were added to 4.66.
436 Version 4.65
437 ------------
439 No new features were added to 4.65.
442 Version 4.64
443 ------------
445 1. ACL variables can now be given arbitrary names, as long as they start with
446 "acl_c" or "acl_m" (for connection variables and message variables), are at
447 least six characters long, with the sixth character being either a digit or
448 an underscore.
450 2. There is a new ACL modifier called log_reject_target. It makes it possible
451 to specify which logs are used for messages about ACL rejections.
453 3. There is a new authenticator called "dovecot". This is an interface to the
454 authentication facility of the Dovecot POP/IMAP server, which can support a
455 number of authentication methods.
457 4. The variable $message_headers_raw provides a concatenation of all the
458 messages's headers without any decoding. This is in contrast to
459 $message_headers, which does RFC2047 decoding on the header contents.
461 5. In a DNS black list, if two domain names, comma-separated, are given, the
462 second is used first to do an initial check, making use of any IP value
463 restrictions that are set. If there is a match, the first domain is used,
464 without any IP value restrictions, to get the TXT record.
466 6. All authenticators now have a server_condition option.
468 7. There is a new command-line option called -Mset. It is useful only in
469 conjunction with -be (that is, when testing string expansions). It must be
470 followed by a message id; Exim loads the given message from its spool
471 before doing the expansions.
473 8. Another similar new command-line option is called -bem. It operates like
474 -be except that it must be followed by the name of a file that contains a
475 message.
477 9. When an address is delayed because of a 4xx response to a RCPT command, it
478 is now the combination of sender and recipient that is delayed in
479 subsequent queue runs until its retry time is reached.
481 10. Unary negation and the bitwise logical operators and, or, xor, not, and
482 shift, have been added to the eval: and eval10: expansion items.
484 11. The variables $interface_address and $interface_port have been renamed
485 as $received_ip_address and $received_port, to make it clear that they
486 relate to message reception rather than delivery. (The old names remain
487 available for compatibility.)
489 12. The "message" modifier can now be used on "accept" and "discard" acl verbs
490 to vary the message that is sent when an SMTP command is accepted.
493 Version 4.63
494 ------------
496 1. There is a new Boolean option called filter_prepend_home for the redirect
497 router.
499 2. There is a new acl, set by acl_not_smtp_start, which is run right at the
500 start of receiving a non-SMTP message, before any of the message has been
501 read.
503 3. When an SMTP error message is specified in a "message" modifier in an ACL,
504 or in a :fail: or :defer: message in a redirect router, Exim now checks the
505 start of the message for an SMTP error code.
507 4. There is a new parameter for LDAP lookups called "referrals", which takes
508 one of the settings "follow" (the default) or "nofollow".
510 5. Version 20070721.2 of exipick now included, offering these new options:
511 --reverse
512 After all other sorting options have bee processed, reverse order
513 before displaying messages (-R is synonym).
514 --random
515 Randomize order of matching messages before displaying.
516 --size
517 Instead of displaying the matching messages, display the sum
518 of their sizes.
519 --sort <variable>[,<variable>...]
520 Before displaying matching messages, sort the messages according to
521 each messages value for each variable.
522 --not
523 Negate the value for every test (returns inverse output from the
524 same criteria without --not).
527 Version 4.62
528 ------------
530 1. The ${readsocket expansion item now supports Internet domain sockets as well
531 as Unix domain sockets. If the first argument begins "inet:", it must be of
532 the form "inet:host:port". The port is mandatory; it may be a number or the
533 name of a TCP port in /etc/services. The host may be a name, or it may be an
534 IP address. An ip address may optionally be enclosed in square brackets.
535 This is best for IPv6 addresses. For example:
537 ${readsocket{inet:[::1]:1234}{<request data>}...
539 Only a single host name may be given, but if looking it up yield more than
540 one IP address, they are each tried in turn until a connection is made. Once
541 a connection has been made, the behaviour is as for ${readsocket with a Unix
542 domain socket.
544 2. If a redirect router sets up file or pipe deliveries for more than one
545 incoming address, and the relevant transport has batch_max set greater than
546 one, a batch delivery now occurs.
548 3. The appendfile transport has a new option called maildirfolder_create_regex.
549 Its value is a regular expression. For a maildir delivery, this is matched
550 against the maildir directory; if it matches, Exim ensures that a
551 maildirfolder file is created alongside the new, cur, and tmp directories.
554 Version 4.61
555 ------------
557 The documentation is up-to-date for the 4.61 release. Major new features since
558 the 4.60 release are:
560 . An option called disable_ipv6, to disable the use of IPv6 completely.
562 . An increase in the number of ACL variables to 20 of each type.
564 . A change to use $auth1, $auth2, and $auth3 in authenticators instead of $1,
565 $2, $3, (though those are still set) because the numeric variables get used
566 for other things in complicated expansions.
568 . The default for rfc1413_query_timeout has been changed from 30s to 5s.
570 . It is possible to use setclassresources() on some BSD OS to control the
571 resources used in pipe deliveries.
573 . A new ACL modifier called add_header, which can be used with any verb.
575 . More errors are detectable in retry rules.
577 There are a number of other additions too.
580 Version 4.60
581 ------------
583 The documentation is up-to-date for the 4.60 release. Major new features since
584 the 4.50 release are:
586 . Support for SQLite.
588 . Support for IGNOREQUOTA in LMTP.
590 . Extensions to the "submission mode" features.
592 . Support for Client SMTP Authorization (CSA).
594 . Support for ratelimiting hosts and users.
596 . New expansion items to help with the BATV "prvs" scheme.
598 . A "match_ip" condition, that matches an IP address against a list.
600 There are many more minor changes.
602 ****