X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/3348576fbe3b012b66076e49e5414cd04bbafbaa..d515a9174a5ea517bc3d27bc4d40223b24d7a47f:/doc/doc-txt/NewStuff diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff index 143fb6cb0..8338b2371 100644 --- a/doc/doc-txt/NewStuff +++ b/doc/doc-txt/NewStuff @@ -1,4 +1,4 @@ -$Cambridge: exim/doc/doc-txt/NewStuff,v 1.46 2005/05/25 09:58:16 fanf2 Exp $ +$Cambridge: exim/doc/doc-txt/NewStuff,v 1.97 2006/03/16 11:51:09 ph10 Exp $ New Features in Exim -------------------- @@ -8,410 +8,212 @@ but have not yet made it into the main manual (which is most conveniently updated when there is a relatively large batch of changes). The doc/ChangeLog file contains a listing of all changes, including bug fixes. - -Exim version 4.52 ------------------ - -TF/01 Support for checking Client SMTP Authorization has been added. CSA is a - system which allows a site to advertise which machines are and are not - permitted to send email. This is done by placing special SRV records in - the DNS, which are looked up using the client's HELO domain. At this - time CSA is still an Internet-Draft. - - Client SMTP Authorization checks are performed by the ACL condition - verify=csa. This will fail if the client is not authorized. If there is - a DNS problem, or if no valid CSA SRV record is found, or if the client - is authorized, the condition succeeds. These three cases can be - distinguished using the expansion variable $csa_status, which can take - one of the values "fail", "defer", "unknown", or "ok". The condition - does not itself defer because that would be likely to cause problems - for legitimate email. - - The error messages produced by the CSA code include slightly more - detail. If $csa_status is "defer" this may be because of problems - looking up the CSA SRV record, or problems looking up the CSA target - address record. There are four reasons for $csa_status being "fail": - the client's host name is explicitly not authorized; the client's IP - address does not match any of the CSA target IP addresses; the client's - host name is authorized but it has no valid target IP addresses (e.g. - the target's addresses are IPv6 and the client is using IPv4); or the - client's host name has no CSA SRV record but a parent domain has - asserted that all subdomains must be explicitly authorized. - - The verify=csa condition can take an argument which is the domain to - use for the DNS query. The default is verify=csa/$sender_helo_name. - - This implementation includes an extension to CSA. If the query domain - is an address literal such as [192.0.2.95], or if it is a bare IP - address, Exim will search for CSA SRV records in the reverse DNS as if - the HELO domain was e.g. 95.2.0.192.in-addr.arpa. Therefore it is - meaningful to say, for example, verify=csa/$sender_host_address - in - fact, this is the check that Exim performs if the client does not say - HELO. This extension can be turned off by setting the main - configuration option dns_csa_use_reverse = false. - - If a CSA SRV record is not found for the domain itself, then a search - is performed through its parent domains for a record which might be - making assertions about subdomains. The maximum depth of this search is - limited using the main configuration option dns_csa_search_limit, which - takes the value 5 by default. Exim does not look for CSA SRV records in - a top level domain, so the default settings handle HELO domains as long - as seven (hostname.five.four.three.two.one.com) which encompasses the - vast majority of legitimate HELO domains. - - The dnsdb lookup also has support for CSA. Although dnsdb already - supports SRV lookups, this is not sufficient because of the extra - parent domain search behaviour of CSA, and (as with PTR lookups) - dnsdb also turns IP addresses into lookups in the reverse DNS space. - The result of ${lookup dnsdb {csa=$sender_helo_name} } has two - space-separated fields: an authorization code and a target host name. - The authorization code can be "Y" for yes, "N" for no, "X" for explicit - authorization required but absent, or "?" for unknown. - -PH/01 The amount of output produced by the "make" process has been reduced, - because the compile lines are often rather long, making it all pretty - unreadable. The new style is along the lines of the 2.6 Linux kernel: - just a short line for each module that is being compiled or linked. - However, it is still possible to get the full output, by calling "make" - like this: - - FULLECHO='' make -e - - The value of FULLECHO defaults to "@", the flag character that suppresses - command reflection in "make". When you ask for the full output, it is - given in addition to the the short output. - -TF/02 There have been two changes concerned with submission mode: - - Until now submission mode always left the return path alone, whereas - locally-submitted messages from untrusted users have the return path - fixed to the user's email address. Submission mode now fixes the return - path to the same address as is used to create the Sender: header. If - /sender_retain is specified then both the Sender: header and the return - path are left alone. - - Note that the changes caused by submission mode take effect after the - predata ACL. This means that any sender checks performed before the - fix-ups will use the untrusted sender address specified by the user, not - the trusted sender address specified by submission mode. Although this - might be slightly unexpected, it does mean that you can configure ACL - checks to spot that a user is trying to spoof another's address, for - example. - - There is also a new /name= option for submission mode which allows you - to specify the user's full name to be included in the Sender: header. - For example: - - accept authenticated = * - control = submission/name=${lookup {$authenticated_id} \ - lsearch {/etc/exim/namelist} } - - The namelist file contains entries like - - fanf: Tony Finch - - And the resulting Sender: header looks like - - Sender: Tony Finch - -TF/03 The control = fakereject ACL modifier now has a fakedefer counterpart, - which works in exactly the same way except it causes a fake SMTP 450 - response after the message data instead of a fake SMTP 550 response. - You must take care when using fakedefer because it will cause messages - to be duplicated when the sender retries. Therefore you should not use - fakedefer if the message will be delivered normally. - -TF/04 There is a new ratelimit ACL condition which can be used to measure - and control the rate at which clients can send email. This is more - powerful than the existing smtp_ratelimit_* options, because those - options only control the rate of commands in a single SMTP session, - whereas the new ratelimit condition works across all connections - (concurrent and sequential) to the same host. - - The syntax of the ratelimit condition is: - - ratelimit = /

/ / - - If the average client sending rate is less than m messages per time - period p then the condition is false, otherwise it is true. - - The parameter p is the smoothing time constant, in the form of an Exim - time interval e.g. 8h for eight hours. A larger time constant means it - takes Exim longer to forget a client's past behaviour. The parameter m is - the maximum number of messages that a client can send in a fast burst. By - increasing both m and p but keeping m/p constant, you can allow a client - to send more messages in a burst without changing its overall sending - rate limit. Conversely, if m and p are both small then messages must be - sent at an even rate. - - The key is used to look up the data used to calcluate the client's - average sending rate. This data is stored in a database maintained by - Exim in its spool directory alongside the retry database etc. For - example, you can limit the sending rate of each authenticated user, - independent of the computer they are sending from, by setting the key - to $authenticated_id. The default key is $sender_host_address. - - Each ratelimit condition can have up to two options. The first option - specifies what Exim measures the rate of, and the second specifies how - Exim handles excessively fast clients. - - The per_mail option means that it measures the client's rate of sending - messages. This is the default if none of the per_* options is specified. - - The per_conn option means that it measures the client's connection rate. - - The per_byte option limits the sender's email bandwidth. Note that it - is best to use this option in the DATA ACL; if it is used in an earlier - ACL it relies on the SIZE parameter on the MAIL command, which may be - inaccurate or completely missing. You can follow the limit m in the - configuration with K, M, or G to specify limits in kilobytes, - megabytes, or gigabytes respectively. - - The per_cmd option means that Exim recomputes the rate every time the - condition is processed, which can be used to limit the SMTP command rate. - The alias per_rcpt is provided for use in the RCPT ACL instead of per_cmd - to make it clear that the effect is to limit the rate at which recipients - are accepted. Note that in this case the rate limiting engine will see a - message with many recipients as a large high-speed burst. - - If a client's average rate is greater than the maximum, the rate - limiting engine can react in two possible ways, depending on the - presence of the strict or leaky options. This is independent of the - other counter-measures (e.g. rejecting the message) that may be - specified by the rest of the ACL. The default mode is leaky, which - avoids a sender's over-aggressive retry rate preventing it from getting - any email through. - - The strict option means that the client's recorded rate is always - updated. The effect of this is that Exim measures the client's average - rate of attempts to send email, which can be much higher than the - maximum. If the client is over the limit it will be subjected to - counter-measures until it slows down below the maximum rate. - - The leaky option means that the client's recorded rate is not updated - if it is above the limit. The effect of this is that Exim measures the - client's average rate of successfully sent email, which cannot be - greater than the maximum. If the client is over the limit it will - suffer some counter-measures, but it will still be able to send email - at the configured maximum rate, whatever the rate of its attempts. - - As a side-effect, the ratelimit condition will set the expansion - variables $sender_rate containing the client's computed rate, - $sender_rate_limit containing the configured value of m, and - $sender_rate_period containing the configured value of p. - - Exim's other ACL facilities are used to define what counter-measures - are taken when the rate limit is exceeded. This might be anything from - logging a warning (e.g. while measuring existing sending rates in order - to define our policy), through time delays to slow down fast senders, - up to rejecting the message. For example, - - # Log all senders' rates - warn - ratelimit = 0 / 1h / strict - log_message = \ - Sender rate $sender_rate > $sender_rate_limit / $sender_rate_period - - # Slow down fast senders - warn - ratelimit = 100 / 1h / per_rcpt / strict - delay = ${eval: 10 * ($sender_rate - $sender_rate_limit) } - - # Keep authenticated users under control - deny - ratelimit = 100 / 1d / strict / $authenticated_id - - # System-wide rate limit - defer - message = Sorry, too busy. Try again later. - ratelimit = 10 / 1s / $primary_hostname - - # Restrict incoming rate from each host, with a default rate limit - # set using a macro and special cases looked up in a table. - defer - message = Sender rate $sender_rate exceeds \ - $sender_rate_limit messages per $sender_rate_period - ratelimit = ${lookup {$sender_host_address} \ - cdb {DB/ratelimits.cdb} \ - {$value} {RATELIMIT} } - - -Version 4.51 +Version 4.61 ------------ -PH/01 The format in which GnuTLS parameters are written to the gnutls-param - file in the spool directory has been changed. This change has been made - to alleviate problems that some people had with the generation of the - parameters by Exim when /dev/random was exhausted. In this situation, - Exim would hang until /dev/random acquired some more entropy. +PH/01 There is a new global option called disable_ipv6, which does exactly what + its name implies. If set true, even if the Exim binary has IPv6 support, + no IPv6 activities take place. AAAA records are never looked up for host + names given in manual routing data or elsewhere. AAAA records that are + received from the DNS as additional data for MX records are ignored. Any + IPv6 addresses that are listed in local_interfaces, manualroute route + data, etc. are also ignored. If IP literals are enabled, the ipliteral + router declines to handle IPv6 literal addresses. + +PH/02 There are now 20 of each type of ACL variable by default (instead of 10). + It is also possible to change the numbers by setting ACL_CVARS and/or + ACL_MVARS in Local/Makefile. Backward compatibility is maintained if you + upgrade to this release with existing messages containing ACL variable + settings on the queue. However, going in the other direction + (downgrading) will not be compatible; the values of ACL variables will be + lost. + +PH/03 If quota_warn_message contains a From: header, Exim now refrains from + adding the default one. Similarly, if it contains a Reply-To: header, the + errors_reply_to option, if set, is not used. + +PH/04 The variables $auth1, $auth2, $auth3 are now available in authenticators, + containing the same values as $1, $2, $3. The new variables are provided + because the numerical variables can be reset during string expansions + (for example, during a "match" operation) and so may lose the + authentication data. The preferred variables are now the new ones, with + the use of the numerical ones being deprecated, though the support will + not be removed, at least, not for a long time. + +PH/05 The "control=freeze" ACL modifier can now be followed by /no_tell. If + the global option freeze_tell is set, it is ignored for the current + message (that is, nobody is told about the freezing), provided all the + "control=freeze" modifiers that are obeyed in the current message have + the /no_tell option. + +PH/06 In both GnuTLS and OpenSSL, an expansion of tls_privatekey that results + in an empty string is now treated as unset. + +PH/07 There is a new log selector called sender_verify_fail, which is set by + default. If it is unset, the separate log line that gives details of a + sender verification failure is not written. Log lines for the rejection + of SMTP commands (e.g. RCPT) contain just "sender verify failed", so some + detail is lost. + +PH/08 The default for dns_check_names_pattern now allows slashes within names, + as there are now some PTR records that contain slashes. This check is + only to protect against broken name servers that fall over on strange + characters, so the fact that it applies to all lookups doesn't matter. + +PH/09 The default for rfc4131_query_timeout has been changed from 30s to 5s. + +PH/10 When compiled on FreeBSD, NetBSD, or BSD/OS, the pipe transport has a new + Boolean option called use_classresources, defaulting false. If it is set + true, the setclassresources() function is used to set resource limits + when a pipe transport is run to perform a delivery. The limits for the + uid under which the pipe is to run are obtained from the login class + database. + +PH/11 If retry_interval_max is set greater than 24 hours, it is quietly reset + to 24 hours. This avoids potential overflow problems when processing G + and H retry rules, and it seems reasonable to require a retry at least + once a day. + +PH/12 When the plaintext authenticator is running as a client, the server + challenges are now checked to ensure they are valid base64 strings. The + default action on failure is to abort the authentication. However, if + client_ignore_invalid_base64 is set true, invalid responses are ignored. + +PH/13 When the plaintext authenticator is running as a client, the challenges + from the server are placed in $auth1, $auth2, etc. as they are received. + Thus, the challege that is received in response to sending the first + string (with the AUTH command) can be used in the expansion of the second + string, and so on. Currently, up to 3 challenge strings are available in + this way. If an invalid base64 string is received when client_ignore_ + invalid_base64 is set, an empty string is put in the $auth variable. + +PH/14 Messages created by the autoreply transport now contain a References: + header. This is constructed in accordance with rules that are described + in section 3.64 of RFC 2822, which states that replies should contain + such a header line, and section 3.14 of RFC 3834, which states that + automatic responses are not different in this respect. However, because + some mail processing software does not cope well with very long header + lines, no more than 12 message IDs are copied from the References: header + line in the incoming message. If there are more than 12, the first one + and then the final 11 are copied, before adding the message ID of the + incoming message. + +PH/15 The smtp transport has a new option called authenticated_sender_force. + When set true, it allows the authenticated_sender option's value to be + used, even if Exim has not authenticated as a client. + +PH/16 The expansion ${time_eval:} converts an Exim time string such as + 2d4h1m into a number of seconds. + +PH/17 The ACL modifier control=allow_auth_unadvertised can be used to permit a + client host to use the SMTP AUTH command even when it has not been + advertised in response to EHLO. Furthermore, because there are apparently + some really broken clients that do this, Exim will even accept AUTH after + HELO when this control is set. It should only be used if you really need + it, and you should limit its use to those broken hosts that do not work + without it. For example: + + warn hosts = 192.168.34.25 + control = allow_auth_unadvertised + + This control is permitted only in the connection and HELO ACLs. + +PH/18 There is a new ACL modifier called "add_header" which does what its name + implies. It specifies one of more header lines that are to be added to an + incoming message, assuming, of course, that the message is ultimately + accepted. + + This modifier is permitted in the MAIL, RCPT, PREDATA, DATA, MIME, and + non-SMTP ACLs (in other words, those that are concerned with accepting a + message). Added header lines are accumulated during the MAIL, RCPT, and + PREDATA ACLs, with any duplicates being discarded. They are then added to + the message before processing the DATA and MIME ACLs, during which + further added header lines are accumulated, again with duplicates + discarded. Thus, it is possible to add two identical header lines to an + SMTP message, but only if one is added before DATA and one after. + + In the case of non-SMTP messages, new headers are accumulated during the + non-SMTP ACL, and added to the message at the end. + + The add_header modifier is available for use with all ACL verbs. In the + case of the WARN verb, add_header supersedes the use of "message" for + this purpose; for the other verbs, it provides a new facility. If both + add_header and "message" are present on a WARN verb, both are processed + according to their specifications. + + The add_header modifier acts immediately it is encountered during the + processing of an ACL. This is different to the (now-deprecated) use of + "message" on a WARN verb, where the action is taken only if all the + conditions are true. Notice the difference between these two cases on a + RCPT ACL: + + deny add_header = ADDED: some text + + + deny + add_header = ADDED: some text + + In the first case, the header is always added, whether or not the current + recipient is rejected. In the second case, the header is added only if + the recipient is rejected. + + If add_header appears more than once on an ACL statement, multiple + headers are added, provided that they have different content. (In the + case of WARN with "message", only the last value of "message" is used.) + + The facility for specifying where the new header is to be inserted, as + described for WARN with "message" in section 39.19 of the 4.60 manual, is + supported. + +PH/19 The following errors can now be detected in retry rules: + + mail_4xx This is like rcpt_4xx, but applies to MAIL commands + + data_4xx This is like rcpt_4xx, but applies to DATA commands and the + response code after the end of the data + + lost_connection This error occurs when the server unexpectedly closes + the SMTP connection. There may, of course, legitmate reasons + for this (host died, network died), but if it repeats a lot + for the same host, it indicates something odd. + + tls_required The server was required to use TLS (hosts_require_tls), + but either did not offer it, or responded with 4xx to + STARTTLS, or there was a problem setting up the TLS connection + + Note that a 5xx response to STARTTLS is a permanent error. + +PH/20 There are now two options for the exicyclog script: - The new code exports and imports the DH and RSA parameters in PEM - format. This means that the parameters can be generated externally using - the certtool command that is part of GnuTLS. + -k specifies the number of old logs to keep, overriding the + default that is set when Exim is built. + + -l specifies the log file path, in the same format as the + log_file_path option (e.g. /var/log/exim_%slog), again, + overriding the script's default - which is to find the setting + from Exim's configuration. - To replace the parameters with new ones, instead of deleting the file - and letting Exim re-create it, you can generate new parameters using - certtool and, when this has been done, replace Exim's cache file by - renaming. The relevant commands are something like this: - # rm -f new.params - # touch new.params - # chown exim:exim new.params - # chmod 0400 new.params - # certtool --generate-privkey --bits 512 >new.params - # echo "" >>new.params - # certtool --generate-dh-params --bits 1024 >> new.params - # mv new.params params +Version 4.60 +------------ - If Exim never has to generate the parameters itself, the possibility of - stalling is removed. +The documentation is up-to-date for the 4.60 release. Major new features since +the 4.50 release are: -PH/02 A new expansion item for dynamically loading and calling a locally- - written C function is now provided, if Exim is compiled with +. Support for SQLite. - EXPAND_DLFUNC=yes +. Support for IGNOREQUOTA in LMTP. - set in Local/Makefile. The facility is not included by default (a - suitable error is given if you try to use it when it is not there.) +. Extensions to the "submission mode" features. - If you enable EXPAND_DLFUNC, you should also be aware of the new redirect - router option forbid_filter_dlfunc. If you have unprivileged users on - your system who are permitted to create filter files, you might want to - set forbid_filter_dlfunc=true in the appropriate router, to stop them - using ${dlfunc to run code within Exim. +. Support for Client SMTP Authorization (CSA). - You load and call an external function like this: - - ${dlfunc{/some/file}{function}{arg1}{arg2}...} - - Once loaded, Exim remembers the dynamically loaded object so that it - doesn't reload the same object file in the same Exim process (but of - course Exim does start new processes frequently). - - There may be from zero to eight arguments to the function. When compiling - a local function that is to be called in this way, local_scan.h should be - included. The Exim variables and functions that are defined by that API - are also available for dynamically loaded functions. The function itself - must have the following type: - - int dlfunction(uschar **yield, int argc, uschar *argv[]) - - Where "uschar" is a typedef for "unsigned char" in local_scan.h. The - function should return one of the following values: - - OK Success. The string that is placed in "yield" is put into - the expanded string that is being built. - - FAIL A non-forced expansion failure occurs, with the error - message taken from "yield", if it is set. - - FAIL_FORCED A forced expansion failure occurs, with the error message - taken from "yield" if it is set. - - ERROR Same as FAIL, except that a panic log entry is written. - - When compiling a function that is to be used in this way with gcc, - you need to add -shared to the gcc command. Also, in the Exim build-time - configuration, you must add -export-dynamic to EXTRALIBS. - -TF/01 $received_time is a new expansion variable containing the time and date - as a number of seconds since the start of the Unix epoch when the - current message was received. - -PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in - Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API, - in use from radiusclient 0.4.0 onwards, be used. It does not appear to be - possible to detect the different versions automatically. - -PH/04 There is a new option called acl_not_smtp_mime that allows you to scan - MIME parts in non-SMTP messages. It operates in exactly the same way as - acl_smtp_mime - -PH/05 It is now possible to redefine a macro within the configuration file. - The macro must have been previously defined within the configuration (or - an included file). A definition on the command line using the -D option - causes all definitions and redefinitions within the file to be ignored. - In other words, -D overrides any values that are set in the file. - Redefinition is specified by using '==' instead of '='. For example: - - MAC1 = initial value - ... - MAC1 == updated value - - Redefinition does not alter the order in which the macros are applied to - the subsequent lines of the configuration file. It is still the same - order in which the macros were originally defined. All that changes is - the macro's value. Redefinition makes it possible to accumulate values. - For example: - - MAC1 = initial value - ... - MAC1 == MAC1 and something added - - This can be helpful in situations where the configuration file is built - from a number of other files. - -PH/06 Macros may now be defined or redefined between router, transport, - authenticator, or ACL definitions, as well as in the main part of the - configuration. They may not, however, be changed within an individual - driver or ACL, or in the local_scan, retry, or rewrite sections of the - configuration. - -PH/07 $acl_verify_message is now set immediately after the failure of a - verification in an ACL, and so is available in subsequent modifiers. In - particular, the message can be preserved by coding like this: +. Support for ratelimiting hosts and users. - warn !verify = sender - set acl_m0 = $acl_verify_message +. New expansion items to help with the BATV "prvs" scheme. - Previously, $acl_verify_message was set only while expanding "message" - and "log_message" when a very denied access. - -PH/08 The redirect router has two new options, sieve_useraddress and - sieve_subaddress. These are passed to a Sieve filter to specify the :user - and :subaddress parts of an address. Both options are unset by default. - However, when a Sieve filter is run, if sieve_useraddress is unset, the - entire original local part (including any prefix or suffix) is used for - :user. An unset subaddress is treated as an empty subaddress. - -PH/09 Quota values can be followed by G as well as K and M. - -PH/10 $message_linecount is a new variable that contains the total number of - lines in the header and body of the message. Compare $body_linecount, - which is the count for the body only. During the DATA and - content-scanning ACLs, $message_linecount contains the number of lines - received. Before delivery happens (that is, before filters, routers, and - transports run) the count is increased to include the Received: header - line that Exim standardly adds, and also any other header lines that are - added by ACLs. The blank line that separates the message header from the - body is not counted. Here is an example of the use of this variable in a - DATA ACL: - - deny message = Too many lines in message header - condition = \ - ${if <{250}{${eval: $message_linecount - $body_linecount}}} - - In the MAIL and RCPT ACLs, the value is zero because at that stage the - message has not yet been received. - -PH/11 In a ${run expansion, the variable $value (which contains the standard - output) is now also usable in the "else" string. - -PH/12 In a pipe transport, although a timeout while waiting for the pipe - process to complete was treated as a delivery failure, a timeout while - writing the message to the pipe was logged, but erroneously treated as a - successful delivery. Such timeouts include transport filter timeouts. For - consistency with the overall process timeout, these timeouts are now - treated as errors, giving rise to delivery failures by default. However, - there is now a new Boolean option for the pipe transport called - timeout_defer, which, if set TRUE, converts the failures into defers for - both kinds of timeout. A transport filter timeout is now identified in - the log output. - - -Version 4.50 ------------- +. A "match_ip" condition, that matches an IP address against a list. -The documentation is up-to-date for the 4.50 release. +There are many more minor changes. ****