X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/b79bf0ff013a1cbb22845ffa15411d5af30bf278..6681531ad79b73f4e811037481a0055ace41e46d:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index ec01e1669..c412c1e16 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2013 +2014 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -553,11 +553,9 @@ key &'0x403043153903637F'&, although that key is expected to be replaced in 2013 A trust path from Nigel's key to Phil's can be observed at &url(https://www.security.spodhuis.org/exim-trustpath). -.new Releases have also been authorized to be performed by Todd Lyons who signs with key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil Pennock and Todd Lyons through a common associate. -.wen The signatures for the tar bundles are in: .display @@ -871,14 +869,12 @@ SOFTWARE. .endblockquote .next -.new .cindex "opendmarc" "acknowledgment" The DMARC implementation uses the OpenDMARC library which is Copyrighted by The Trusted Domain Project. Portions of Exim source which use OpenDMARC derived code are indicated in the respective source files. The full OpenDMARC license is provided in the LICENSE.opendmarc file contained in the distributed source code. -.wen .next Many people have contributed code fragments, some large, some small, that were @@ -1382,7 +1378,7 @@ Setting the &%verify%& option actually sets two options, &%verify_sender%& and &%verify_recipient%&, which independently control the use of the router for sender and recipient verification. You can set these options directly if you want a router to be used for only one type of verification. -.new "Note that cutthrough delivery is classed as a recipient verification for this purpose." +Note that cutthrough delivery is classed as a recipient verification for this purpose. .next If the &%address_test%& option is set false, the router is skipped when Exim is run with the &%-bt%& option to test an address routing. This can be helpful @@ -1392,7 +1388,7 @@ having to simulate the effect of the scanner. .next Routers can be designated for use only when verifying an address, as opposed to routing it for delivery. The &%verify_only%& option controls this. -.new "Again, cutthrough delivery counts as a verification." +Again, cutthrough delivery counts as a verification. .next Individual routers can be explicitly skipped when running the routers to check an address given in the SMTP EXPN command (see the &%expn%& option). @@ -2714,14 +2710,12 @@ no arguments. This option is an alias for &%-bV%& and causes version information to be displayed. -.new .vitem &%-Ac%& &&& &%-Am%& .oindex "&%-Ac%&" .oindex "&%-Am%&" These options are used by Sendmail for selecting configuration files and are ignored by Exim. -.wen .vitem &%-B%&<&'type'&> .oindex "&%-B%&" @@ -2982,7 +2976,6 @@ use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files if this is required. If the &%bi_command%& option is not set, calling Exim with &%-bi%& is a no-op. -.new . // Keep :help first, then the rest in alphabetical order .vitem &%-bI:help%& .oindex "&%-bI:help%&" @@ -3008,7 +3001,6 @@ useful for ManageSieve (RFC 5804) implementations, in providing that protocol's &`SIEVE`& capability response line. As the precise list may depend upon compile-time build options, which this option will adapt to, this is the only way to guarantee a correct response. -.wen .vitem &%-bm%& .oindex "&%-bm%&" @@ -3123,11 +3115,9 @@ configuration file is output. If a list of configuration files was supplied, the value that is output here is the name of the file that was actually used. -.new .cindex "options" "hiding name of" If the &%-n%& flag is given, then for most modes of &%-bP%& operation the name will not be output. -.wen .cindex "daemon" "process id (pid)" .cindex "pid (process id)" "of daemon" @@ -3732,7 +3722,6 @@ if &%-f%& is also present, it overrides &"From&~"&. .vitem &%-G%& .oindex "&%-G%&" .cindex "submission fixups, suppressing (command-line)" -.new This option is equivalent to an ACL applying: .code control = suppress_local_fixups @@ -3743,7 +3732,6 @@ in future. As this affects audit information, the caller must be a trusted user to use this option. -.wen .vitem &%-h%&&~<&'number'&> .oindex "&%-h%&" @@ -3761,7 +3749,6 @@ line by itself should not terminate an incoming, non-SMTP message. I can find no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'& command in Solaris 2.4 uses it. See also &%-ti%&. -.new .vitem &%-L%&&~<&'tag'&> .oindex "&%-L%&" .cindex "syslog" "process name; set with flag" @@ -3772,7 +3759,6 @@ read and parsed, to determine access rights, before this is set and takes effect, so early configuration file errors will not honour this flag. The tag should not be longer than 32 characters. -.wen .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~... .oindex "&%-M%&" @@ -4012,13 +3998,11 @@ routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to the message, and applies to any subsequent delivery attempts that may happen for that message. -.new .vitem &%-n%& .oindex "&%-n%&" This option is interpreted by Sendmail to mean &"no aliasing"&. For normal modes of operation, it is ignored by Exim. When combined with &%-bP%& it suppresses the name of an option from being output. -.wen .vitem &%-O%&&~<&'data'&> .oindex "&%-O%&" @@ -4638,12 +4622,10 @@ National Language Support extended characters in the body of the mail item"&). It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores this option. -.new .vitem &%-X%&&~<&'logfile'&> .oindex "&%-X%&" This option is interpreted by Sendmail to cause debug information to be sent to the named file. It is ignored by Exim. -.wen .endlist .ecindex IIDclo1 @@ -6949,7 +6931,6 @@ 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. -.new .cindex "A+" "in &(dnsdb)& lookup" The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA and then an A lookup. All results are returned; defer processing @@ -6957,7 +6938,6 @@ and then an A lookup. All results are returned; defer processing .code ${lookup dnsdb {>; a+=$sender_helo_name}} .endd -.wen .section "Multiple dnsdb lookups" "SECID67" @@ -7060,6 +7040,18 @@ With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular LDAP connections, rather than the SSL-on-connect &`ldaps`&. See the &%ldap_start_tls%& option. +.new +Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly +controlled. Every part of the TLS configuration can be configured by settings in +&_exim.conf_&. Depending on the version of the client libraries installed on +your system, some of the initialization may have required setting options in +&_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed +certificates. This revealed a nuance where the current UID that exim was +running as could affect which config files it read. With Exim 4.83, these +methods become optional, only taking effect if not specifically set in +&_exim.conf_&. +.wen + .section "LDAP quoting" "SECID68" .cindex "LDAP" "quoting" @@ -8306,7 +8298,6 @@ Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same list. The effect of each one lasts until the next, or until the end of the list. -.new To explain the host/ip processing logic a different way for the same ACL: .ilist @@ -8336,7 +8327,6 @@ If the first &%accept%& fails, Exim goes on to try the second one. See chapter &`+ignore_unknown`&, which was discussed in depth in the first example in this section. .endlist -.wen @@ -8843,7 +8833,6 @@ This item inserts &"basic"& header lines. It is described with the &%header%& expansion item below. -.new .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&" .cindex "expansion" "calling an acl" .cindex "&%acl%&" "call from expansion" @@ -8858,7 +8847,6 @@ the result of the expansion. If no message is set and the ACL returns accept or deny the expansion result is an empty string. If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails. -.wen .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&& @@ -9193,6 +9181,44 @@ of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with &%strlen%&, which gives the length of a string. +.vitem "&*${listextract{*&<&'number'&>&*}&&& + {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" +.cindex "expansion" "extracting list elements by number" +.cindex "&%listextract%&" "extract list elements by number" +.cindex "list" "extracting elements by number" +The <&'number'&> argument must consist entirely of decimal digits, +apart from an optional leading minus, +and leading and trailing white space (which is ignored). + +After expansion, <&'string1'&> is interpreted as a list, colon-separated by +default, but the separator can be changed in the usual way. + +The first field of the list is numbered one. +If the number is negative, the fields are +counted from the end of the list, with the rightmost one numbered -1. +The numbered element of the list is extracted and placed in &$value$&, +then <&'string2'&> is expanded as the result. + +If the modulus of the +number is zero or greater than the number of fields in the string, +the result is the expansion of <&'string3'&>. + +For example: +.code +${listextract{2}{x:42:99}} +.endd +yields &"42"&, and +.code +${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}} +.endd +yields &"result: 99"&. + +If {<&'string3'&>} is omitted, an empty string is used for string3. +If {<&'string2'&>} is also omitted, the value that was +extracted is used. +You can use &`fail`& instead of {<&'string3'&>} as in a string extract. + + .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&& {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" This is the first of one of two different types of lookup item, which are both @@ -9491,7 +9517,6 @@ can be the word &"fail"& (not in braces) to force expansion failure if the command does not succeed. If both strings are omitted, the result is contents of the standard output/error on success, and nothing on failure. -.new .vindex "&$run_in_acl$&" The standard output/error of the command is put in the variable &$value$&. In this ACL example, the output of a command is logged for the admin to @@ -9505,7 +9530,6 @@ shell must be invoked directly, such as with: .code ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}} .endd -.wen .vindex "&$runrc$&" The return code from the command is put in the variable &$runrc$&, and this @@ -9667,7 +9691,6 @@ expansion item, which extracts the working address from a single RFC2822 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of processing lists. -.new To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows a strict interpretation of header line formatting. Exim parses the bare, unquoted portion of an email address and if it finds a comma, treats it as an @@ -9691,7 +9714,6 @@ Last:user@example.com # exim -be '${addresses:From: "Last, First" }' user@example.com .endd -.wen .vitem &*${base62:*&<&'digits'&>&*}*& .cindex "&%base62%& expansion item" @@ -9847,7 +9869,6 @@ be useful for processing the output of the MD5 and SHA-1 hashing functions. -.new .vitem &*${hexquote:*&<&'string'&>&*}*& .cindex "quoting" "hex-encoded unprintable characters" .cindex "&%hexquote%& expansion item" @@ -9855,7 +9876,6 @@ This operator converts non-printable characters in a string into a hex escape form. Byte values between 33 (!) and 126 (~) inclusive are left as is, and other byte values are converted to &`\xNN`&, for example a byte value 127 is converted to &`\x7f`&. -.wen .vitem &*${lc:*&<&'string'&>&*}*& @@ -9883,7 +9903,6 @@ See the description of the general &%length%& item above for details. Note that when &%length%& is used as an operator. -.new .vitem &*${listcount:*&<&'string'&>&*}*& .cindex "expansion" "list item count" .cindex "list" "item count" @@ -9901,7 +9920,6 @@ If the optional type is given it must be one of "a", "d", "h" or "l" and selects address-, domain-, host- or localpart- lists to search among respectively. Otherwise all types are searched in an undefined order and the first matching list is returned. -.wen .vitem &*${local_part:*&<&'string'&>&*}*& @@ -10153,6 +10171,14 @@ number of larger units and output in Exim's normal time format, for example, .cindex "expansion" "case forcing" .cindex "&%uc%& expansion item" This forces the letters in the string into upper-case. + +.vitem &*${utf8clean:*&<&'string'&>&*}*& +.cindex "correction of invalid utf-8 sequences in strings" +.cindex "utf-8" "utf-8 sequences" +.cindex "incorrect utf-8" +.cindex "expansion" "utf-8 forcing" +.cindex "&%utf8clean%& expansion item" +This replaces any invalid utf-8 sequence in the string by the character &`?`&. .endlist @@ -10201,7 +10227,6 @@ In all cases, a relative comparator OP is testing if <&'string1'&> OP 10M, not if 10M is larger than &$message_size$&. -.new .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&& {*&<&'arg2'&>&*}...}*& .cindex "expansion" "calling an acl" @@ -10216,7 +10241,6 @@ a value using a "message =" modifier the variable $value becomes the result of the expansion, otherwise it is empty. If the ACL returns accept the condition is true; if deny, false. If the ACL returns defer the result is a forced-fail. -.wen .vitem &*bool&~{*&<&'string'&>&*}*& .cindex "expansion" "boolean parsing" @@ -10412,7 +10436,7 @@ ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} The value of &$item$& is saved and restored while &*forany*& or &*forall*& is being processed, to enable these expansion items to be nested. -.new "To scan a named list, expand it with the &*listnamed*& operator." +To scan a named list, expand it with the &*listnamed*& operator. .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& @@ -10957,7 +10981,6 @@ the value of &$authenticated_id$& is normally the login name of the calling process. However, a trusted user can override this by means of the &%-oMai%& command line option. -.new .vitem &$authenticated_fail_id$& .cindex "authentication" "fail" "id" .vindex "&$authenticated_fail_id$&" @@ -10968,7 +10991,6 @@ available for processing in the ACL's, generally the quit or notquit ACL. A message to a local recipient could still be accepted without requiring authentication, which means this variable could also be visible in all of the ACL's as well. -.wen .vitem &$authenticated_sender$& @@ -11181,13 +11203,11 @@ inserting the message header line with the given name. Note that the name must be terminated by colon or white space, because it may contain a wide variety of characters. Note also that braces must &'not'& be used. -.new .vitem &$headers_added$& .vindex "&$headers_added$&" Within an ACL this variable contains the headers added so far by the ACL modifier add_header (section &<>&). The headers are a newline-separated list. -.wen .vitem &$home$& .vindex "&$home$&" @@ -11859,13 +11879,11 @@ envelope sender. .vindex "&$return_size_limit$&" This is an obsolete name for &$bounce_return_size_limit$&. -.new .vitem &$router_name$& .cindex "router" "name" .cindex "name" "of router" .vindex "&$router_name$&" During the running of a router this variable contains its name. -.wen .vitem &$runrc$& .cindex "return code" "from &%run%& expansion" @@ -11958,7 +11976,6 @@ driver that successfully authenticated the client from which the message was received. It is empty if there was no successful authentication. See also &$authenticated_id$&. -.new .vitem &$sender_host_dnssec$& .vindex "&$sender_host_dnssec$&" If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or @@ -11969,7 +11986,7 @@ other times, this variable is false. It is likely that you will need to coerce DNSSEC support on in the resolver library, by setting: .code -dns_use_dnssec = 1 +dns_dnssec_ok = 1 .endd Exim does not perform DNSSEC validation itself, instead leaving that to a @@ -11980,7 +11997,6 @@ with DNSSEC, only the reverse DNS. If you have changed &%host_lookup_order%& so that &`bydns`& is not the first mechanism in the list, then this variable will be false. -.wen .vitem &$sender_host_name$& @@ -12181,7 +12197,6 @@ command in a filter file. Its use is explained in the description of that command, which can be found in the separate document entitled &'Exim's interfaces to mail filtering'&. -.new .vitem &$tls_in_bits$& .vindex "&$tls_in_bits$&" Contains an approximation of the TLS cipher's bit-strength @@ -12280,7 +12295,6 @@ the outbound. During outbound SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on the transport. -.wen .vitem &$tod_bsdinbox$& .vindex "&$tod_bsdinbox$&" @@ -12323,13 +12337,11 @@ This variable contains the numerical value of the local timezone, for example: This variable contains the UTC date and time in &"Zulu"& format, as specified by ISO 8601, for example: 20030221154023Z. -.new .vitem &$transport_name$& .cindex "transport" "name" .cindex "name" "of transport" .vindex "&$transport_name$&" During the running of a transport, this variable contains its name. -.wen .vitem &$value$& .vindex "&$value$&" @@ -13186,10 +13198,10 @@ See also the &'Policy controls'& section above. .row &%disable_ipv6%& "do no IPv6 processing" .row &%dns_again_means_nonexist%& "for broken domains" .row &%dns_check_names_pattern%& "pre-DNS syntax check" +.row &%dns_dnssec_ok%& "parameter for resolver" .row &%dns_ipv4_lookup%& "only v4 lookup for these domains" .row &%dns_retrans%& "parameter for resolver" .row &%dns_retry%& "parameter for resolver" -.row &%dns_use_dnssec%& "parameter for resolver" .row &%dns_use_edns0%& "parameter for resolver" .row &%hold_domains%& "hold delivery for these domains" .row &%local_interfaces%& "for routing checks" @@ -13252,12 +13264,10 @@ A more detailed analysis of the issues is provided by Dan Bernstein: &url(http://cr.yp.to/smtp/8bitmime.html) .endd -.new To log received 8BITMIME status use .code log_selector = +8bitmime .endd -.wen .option acl_not_smtp main string&!! unset .cindex "&ACL;" "for non-SMTP messages" @@ -13688,6 +13698,9 @@ a very large time at the end of the list. For example: .code delay_warning = 2h:12h:99d .endd +Note that the option is only evaluated at the time a delivery attempt fails, +which depends on retry and queue-runner configuration. +Typically retries will be configured more frequently than warning messages. .option delay_warning_condition main string&!! "see below" .vindex "&$domain$&" @@ -13809,6 +13822,17 @@ This option controls whether or not an IP address, given as a CSA domain, is reversed and looked up in the reverse DNS, as described in more detail in section &<>&. + +.option dns_dnssec_ok main integer -1 +.cindex "DNS" "resolver options" +.cindex "DNS" "DNSSEC" +If this option is set to a non-negative number then Exim will initialise the +DNS resolver library to either use or not use DNSSEC, overriding the system +default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. + +If the resolver library does not support DNSSEC then this option has no effect. + + .option dns_ipv4_lookup main "domain list&!!" unset .cindex "IPv6" "DNS lookup for AAAA records" .cindex "DNS" "IPv6 lookup for AAAA records" @@ -13839,18 +13863,6 @@ to set in them. See &%dns_retrans%& above. -.new -.option dns_use_dnssec main integer -1 -.cindex "DNS" "resolver options" -.cindex "DNS" "DNSSEC" -If this option is set to a non-negative number then Exim will initialise the -DNS resolver library to either use or not use DNSSEC, overriding the system -default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. - -If the resolver library does not support DNSSEC then this option has no effect. -.wen - - .option dns_use_edns0 main integer -1 .cindex "DNS" "resolver options" .cindex "DNS" "EDNS0" @@ -14076,7 +14088,6 @@ server. This reduces security slightly, but improves interworking with older implementations of TLS. -.new option gnutls_allow_auto_pkcs11 main boolean unset This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with the p11-kit configuration files in &_/etc/pkcs11/modules/_&. @@ -14084,7 +14095,6 @@ the p11-kit configuration files in &_/etc/pkcs11/modules/_&. See &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs) for documentation. -.wen @@ -14838,9 +14848,7 @@ Possible options may include: .next &`no_tlsv1_2`& .next -.new &`safari_ecdhe_ecdsa_bug`& -.wen .next &`single_dh_use`& .next @@ -14857,14 +14865,12 @@ Possible options may include: &`tls_rollback_bug`& .endlist -.new As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects all clients connecting using the MacOS SecureTransport TLS facility prior to MacOS 10.8.4, including email clients. If you see old MacOS clients failing to negotiate TLS then this option value might help, provided that your OpenSSL release is new enough to contain this work-around. This may be a situation where you have to upgrade OpenSSL to get buggy clients working. -.wen .option oracle_servers main "string list" unset @@ -16135,7 +16141,6 @@ The available primes are: Some of these will be too small to be accepted by clients. Some may be too large to be accepted by clients. -.new The TLS protocol does not negotiate an acceptable size for this; clients tend to hard-drop connections if what is offered by the server is unacceptable, whether too large or too small, and there's no provision for the client to @@ -16150,7 +16155,6 @@ used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many mail user agents (MUAs). The lower bound comes from Debian installs of Exim4 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum acceptable bound from 1024 to 2048. -.wen .option tls_on_connect_ports main "string list" unset @@ -16219,10 +16223,8 @@ use OpenSSL with a directory. See &<>& for discussion of when this option might be re-expanded. -.new A forced expansion failure or setting to an empty string is equivalent to being unset. -.wen .option tls_verify_hosts main "host list&!!" unset @@ -16762,10 +16764,8 @@ The &%headers_add%& option is expanded after &%errors_to%&, but before the expansion is forced to fail, the option has no effect. Other expansion failures are treated as configuration errors. -.new Unlike most options, &%headers_add%& can be specified multiple times for a router; all listed headers are added. -.wen &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)& router that has the &%one_time%& option set. @@ -17440,7 +17440,7 @@ Setting this option has the effect of setting &%verify_sender%& and .oindex "&%-bv%&" .cindex "router" "used only when verifying" If this option is set, the router is used only when verifying an address, -.new "delivering in cutthrough mode or" +delivering in cutthrough mode or testing with the &%-bv%& option, not when actually doing a delivery, testing with the &%-bt%& option, or running the SMTP EXPN command. It can be further restricted to verifying only senders or recipients by means of @@ -18811,7 +18811,6 @@ quote just the command. An item such as .endd is interpreted as a pipe with a rather strange command name, and no arguments. -.new Note that the above example assumes that the text comes from a lookup source of some sort, so that the quotes are part of the data. If composing a redirect router with a &%data%& option directly specifying this command, the @@ -18821,7 +18820,6 @@ are two main approaches to get around this: escape quotes to be part of the data itself, or avoid using this mechanism and instead create a custom transport with the &%command%& option set and reference that transport from an &%accept%& router. -.wen .next .cindex "file" "in redirection list" @@ -19763,10 +19761,8 @@ so on when debugging driver configurations. For example, if a &%headers_add%& option is not working properly, &%debug_print%& could be used to output the variables it references. A newline is added to the text if it does not end with one. -.new The variables &$transport_name$& and &$router_name$& contain the name of the transport and the router that called it. -.wen .option delivery_date_add transports boolean false .cindex "&'Delivery-date:'& header line" @@ -19811,10 +19807,8 @@ routers. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. -.new Unlike most options, &%headers_add%& can be specified multiple times for a transport; all listed headers are added. -.wen .option headers_only transports boolean false @@ -21871,7 +21865,6 @@ inserted in the argument list at that point &'as a separate argument'&. This avoids any problems with spaces or shell metacharacters, and is of use when a &(pipe)& transport is handling groups of addresses in a batch. -.new If &%force_command%& is enabled on the transport, Special handling takes place for an argument that consists of precisely the text &`$address_pipe`&. It is handled similarly to &$pipe_addresses$& above. It is expanded and each @@ -21880,7 +21873,6 @@ argument is inserted in the argument list at that point the only item in the argument; in fact, if it were then &%force_command%& should behave as a no-op. Rather, it should be used to adjust the command run while preserving the argument vector separation. -.wen After splitting up into arguments and expansion, the resulting command is run in a subprocess directly from the transport, &'not'& under a shell. The @@ -22034,7 +22026,6 @@ a bounce message is sent. If &%freeze_signal%& is set, the message will be frozen in Exim's queue instead. -.new .option force_command pipe boolean false .cindex "force command" .cindex "&(pipe)& transport", "force command" @@ -22051,7 +22042,6 @@ force_command Note that &$address_pipe$& is handled specially in &%command%& when &%force_command%& is set, expanding out to the original argument vector as separate items, similarly to a Unix shell &`"$@"`& construct. -.wen .option ignore_status pipe boolean false If this option is true, the status returned by the subprocess that is set up to @@ -22414,10 +22404,8 @@ appropriate values for the outgoing connection, and these are the values that are in force when any authenticators are run and when the &%authenticated_sender%& option is expanded. -.new These variables are deprecated in favour of &$tls_in_cipher$& et. al. and will be removed in a future release. -.wen .section "Private options for smtp" "SECID146" @@ -22552,7 +22540,6 @@ See the &%search_parents%& option in chapter &<>& for more details. -.new .option dscp smtp string&!! unset .cindex "DCSP" "outbound" This option causes the DSCP value associated with a socket to be set to one @@ -22566,7 +22553,6 @@ The outbound packets from Exim will be marked with this value in the header that these values will have any effect, not be stripped by networking equipment, or do much of anything without cooperation with your Network Engineer and those of all network operators between the source and destination. -.wen .option fallback_hosts smtp "string list" unset @@ -22701,14 +22687,12 @@ that matches this list, even if the server host advertises PIPELINING support. Exim will not try to start a TLS session when delivering to any host that matches this list. See chapter &<>& for details of TLS. -.new .option hosts_verify_avoid_tls smtp "host list&!!" * .cindex "TLS" "avoiding for certain hosts" Exim will not try to start a TLS session for a verify callout, or when delivering in cutthrough mode, to any host that matches this list. Note that the default is to not use TLS. -.wen .option hosts_max_try smtp integer 5 @@ -22974,7 +22958,6 @@ This option specifies a certificate revocation list. The expanded value must be the name of a file that contains a CRL in PEM format. -.new .option tls_dh_min_bits smtp integer 1024 .cindex "TLS" "Diffie-Hellman minimum acceptable size" When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman @@ -22984,7 +22967,6 @@ If the parameter offered by the server is too small, then the TLS handshake will fail. Only supported when using GnuTLS. -.wen .option tls_privatekey smtp string&!! unset @@ -23045,6 +23027,14 @@ unknown state), opens a new one to the same host, and then tries the delivery in clear. +.option tls_try_verify_hosts smtp "host list&!! unset +.cindex "TLS" "server certificate verification" +.cindex "certificate" "verification of server" +For OpenSSL only, this option gives a list of hosts for which, on encrypted connections, +certificate verification will be tried but need not succeed. +The &%tls_verify_certificates%& option must also be set. + + .option tls_verify_certificates smtp string&!! unset .cindex "TLS" "server certificate verification" .cindex "certificate" "verification of server" @@ -23059,6 +23049,20 @@ single file if you are using GnuTLS. The values of &$host$& and &$host_address$& are set to the name and address of the server during the expansion of this option. See chapter &<>& for details of TLS. +For back-compatability, or when GnuTLS is used, +if neither tls_verify_hosts nor tls_try_verify_hosts are set +and certificate verification fails the TLS connection is closed. + + +.option tls_verify_hosts smtp "host list&!! unset +.cindex "TLS" "server certificate verification" +.cindex "certificate" "verification of server" +For OpenSSL only, this option gives a list of hosts for which. on encrypted connections, +certificate verification must succeed. +The &%tls_verify_certificates%& option must also be set. +If both this option and &%tls_try_verify_hosts%& are unset +operation is as if this option selected all hosts. + @@ -24295,12 +24299,10 @@ client_condition = ${if !eq{$tls_out_cipher}{}} .endd -.new .option client_set_id authenticators string&!! unset When client authentication succeeds, this condition is expanded; the result is used in the log lines for outbound messasges. Typically it will be the user name used for authentication. -.wen .option driver authenticators string unset @@ -24671,7 +24673,6 @@ expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&. For any other result, a temporary error code is returned, with the expanded string as the error text -.new ", and the failed id saved in &$authenticated_fail_id$&." &*Warning*&: If you use a lookup in the expansion to find the user's password, be sure to make the authentication fail if the user is unknown. @@ -25547,12 +25548,10 @@ option). The &%tls_require_ciphers%& options operate differently, as described in the sections &<>& and &<>&. .next -.new The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS. When using OpenSSL, this option is ignored. (If an API is found to let OpenSSL be configured in this way, let the Exim Maintainers know and we'll likely use it). -.wen .next Some other recently added features may only be available in one or the other. This should be documented with the feature. If the documentation does not @@ -25855,10 +25854,8 @@ example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS documentation for more details. -.new For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged (again depending on the &%tls_cipher%& log selector). -.wen .section "Requesting and verifying client certificates" "SECID183" @@ -25967,6 +25964,12 @@ for OpenSSL only (not GnuTLS), a directory, that contains a collection of expected server certificates. The client verifies the server's certificate against this collection, taking into account any revoked certificates that are in the list defined by &%tls_crl%&. +Failure to verify fails the TLS connection unless either of the +&%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set. + +The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict +certificate verification to the listed servers. Verification either must +or need not succeed respectively. If &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a @@ -26144,15 +26147,19 @@ validation to succeed, of course, but if it's not preinstalled, sending the root certificate along with the rest makes it available for the user to install if the receiving end is a client MUA that can interact with a user. +Note that certificates using MD5 are unlikely to work on today's Internet; +even if your libraries allow loading them for use in Exim when acting as a +server, increasingly clients will not accept such certificates. The error +diagnostics in such a case can be frustratingly vague. + + .section "Self-signed certificates" "SECID187" .cindex "certificate" "self-signed" You can create a self-signed certificate using the &'req'& command provided with OpenSSL, like this: -.new . ==== Do not shorten the duration here without reading and considering . ==== the text below. Please leave it at 9999 days. -.wen .code openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \ -days 9999 -nodes @@ -26165,7 +26172,6 @@ that you are prompted for, and any use that is made of the key causes more prompting for the passphrase. This is not helpful if you are going to use this certificate and key in an MTA, where prompting is not possible. -.new . ==== I expect to still be working 26 years from now. The less technical . ==== debt I create, in terms of storing up trouble for my later years, the . ==== happier I will be then. We really have reached the point where we @@ -26181,7 +26187,6 @@ of the certificate or reconsider your platform deployment. (At time of writing, reducing the duration is the most likely choice, but the inexorable progression of time takes us steadily towards an era where this will not be a sensible resolution). -.wen A self-signed certificate made in this way is sufficient for testing, and may be adequate for all your requirements if you are mainly interested in @@ -26381,10 +26386,8 @@ before or after the data) correctly &-- they keep the message on their queues and try again later, but that is their problem, though it does waste some of your resources. -.new The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and the &%acl_smtp_mime%& ACLs. -.wen .section "The SMTP DKIM ACL" "SECTDKIMACL" The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support @@ -26394,11 +26397,9 @@ The ACL test specified by &%acl_smtp_dkim%& happens after a message has been received, and is executed for each DKIM signature found in a message. If not otherwise specified, the default action is to accept. -.new This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&. For details on the operation of DKIM, see chapter &<>&. -.wen .section "The SMTP MIME ACL" "SECID194" @@ -27234,12 +27235,10 @@ all the conditions are true, wherever it appears in an ACL command, whereas effect. -.new .vitem &*remove_header*&&~=&~<&'text'&> This modifier specifies one or more header names in a colon-separated list that are to be removed from an incoming message, assuming, of course, that the message is ultimately accepted. For details, see section &<>&. -.wen .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&> @@ -27248,7 +27247,6 @@ This modifier puts a value into one of the ACL variables (see section &<>&). -.new .vitem &*udpsend*&&~=&~<&'parameters'&> This modifier sends a UDP packet, for purposes such as statistics collection or behaviour monitoring. The parameters are expanded, and @@ -27262,7 +27260,6 @@ when: udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ $tod_zulu $sender_host_address .endd -.wen .endlist @@ -27324,7 +27321,6 @@ Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. -.new .vitem &*control&~=&~cutthrough_delivery*& .cindex "&ACL;" "cutthrough routing" .cindex "cutthrough" "requesting" @@ -27333,7 +27329,16 @@ It is usable in the RCPT ACL and valid only for single-recipient mails forwarded from one SMTP connection to another. If a recipient-verify callout connection is requested in the same ACL it is held open and used for the data, otherwise one is made after the ACL completes. -.new "Note that routers are used in verify mode." + +Note that routers are used in verify mode, +and cannot depend on content of received headers. +Note also that headers cannot be +modified by any of the post-data ACLs (DATA, MIME and DKIM). +Headers may be modified by routers (subject to the above) and transports. + +Cutthrough delivery is not supported via transport-filters or when DKIM signing +of outgoing messages is done, because it sends data to the ultimate destination +before the entire message has been received from the source. Should the ultimate destination system positively accept or reject the mail, a corresponding indication is given to the source system and nothing is queued. @@ -27344,10 +27349,8 @@ line. Delivery in this mode avoids the generation of a bounce mail to a (possibly faked) sender when the destination system is doing content-scan based rejection. -.wen -.new .vitem &*control&~=&~debug/*&<&'options'&> .cindex "&ACL;" "enabling debug logging" .cindex "debugging" "enabling from an ACL" @@ -27364,7 +27367,6 @@ contexts): control = debug/opts=+expand+acl control = debug/tag=.$message_exim_id/opts=+expand .endd -.wen .vitem &*control&~=&~dkim_disable_verify*& @@ -27374,7 +27376,6 @@ This control turns off DKIM verification processing entirely. For details on the operation and configuration of DKIM, see chapter &<>&. -.new .vitem &*control&~=&~dscp/*&<&'value'&> .cindex "&ACL;" "setting DSCP value" .cindex "DSCP" "inbound" @@ -27390,7 +27391,6 @@ The outbound packets from Exim will be marked with this value in the header that these values will have any effect, not be stripped by networking equipment, or do much of anything without cooperation with your Network Engineer and those of all network operators between the source and destination. -.wen .vitem &*control&~=&~enforce_sync*& &&& @@ -27592,12 +27592,15 @@ warn dnslists = sbl.spamhaus.org : \ add_header = X-blacklisted-at: $dnslist_domain .endd The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA, -MIME, and non-SMTP ACLs (in other words, those that are concerned with +MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with receiving a message). The message must ultimately be accepted for &%add_header%& to have any significant effect. You can use &%add_header%& with any ACL verb, including &%deny%& (though this is potentially useful only in a RCPT ACL). +Headers will not be added to the message if the modifier is used in +DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing. + Leading and trailing newlines are removed from the data for the &%add_header%& modifier; if it then contains one or more newlines that @@ -27629,9 +27632,7 @@ passing data between (for example) the MAIL and RCPT ACLs. If you want to do this, you can use ACL variables, as described in section &<>&. -.new The list of headers yet to be added is given by the &%$headers_added%& variable. -.wen The &%add_header%& modifier acts immediately as it is encountered during the processing of an ACL. Notice the difference between these two cases: @@ -27682,7 +27683,6 @@ system filter or in a router or transport. -.new .section "Removing header lines in ACLs" "SECTremoveheadacl" .cindex "header lines" "removing in an ACL" .cindex "header lines" "position of removed lines" @@ -27694,12 +27694,15 @@ warn message = Remove internal headers remove_header = x-route-mail1 : x-route-mail2 .endd The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA, -MIME, and non-SMTP ACLs (in other words, those that are concerned with +MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with receiving a message). The message must ultimately be accepted for &%remove_header%& to have any significant effect. You can use &%remove_header%& with any ACL verb, including &%deny%&, though this is really not useful for any verb that doesn't result in a delivered message. +Headers will not be removed to the message if the modifier is used in +DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing. + More than one header can be removed at the same time by using a colon separated list of header names. The header matching is case insensitive. Wildcards are not permitted, nor is list expansion performed, so you cannot use hostlists to @@ -27750,7 +27753,6 @@ are honoured. &*Warning*&: This facility currently applies only to header lines that are present during ACL processing. It does NOT remove header lines that are added in a system filter or in a router or transport. -.wen @@ -27785,13 +27787,11 @@ condition is on a &%warn%& verb. In that case, a &"defer"& return makes the condition false. This means that further processing of the &%warn%& verb ceases, but processing of the ACL continues. -.new If the argument is a named ACL, up to nine space-separated optional values can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9, and $acl_narg is set to the count of values. Previous values of these variables are restored after the call returns. The name and values are expanded separately. -.wen If the nested &%acl%& returns &"drop"& and the outer condition denies access, the connection is dropped. If it returns &"discard"&, the verb must be @@ -28023,6 +28023,23 @@ This condition checks whether the sending host (the client) is authorized to send email. Details of how this works are given in section &<>&. +.new +.vitem &*verify&~=&~header_names_ascii*& +.cindex "&%verify%& ACL condition" +.cindex "&ACL;" "verifying header names only ASCII" +.cindex "header lines" "verifying header names only ASCII" +.cindex "verifying" "header names only ASCII" +This condition is relevant only in an ACL that is run after a message has been +received, that is, in an ACL specified by &%acl_smtp_data%& or +&%acl_not_smtp%&. It checks all header names (not the content) to make sure +there are no non-ASCII characters, also excluding control characters. The +allowable characters are decimal ASCII values 33 through 126. + +Exim itself will handle headers with non-ASCII characters, but it can cause +problems for downstream applications, so this option will allow their +detection and rejection in the DATA ACL's. +.wen + .vitem &*verify&~=&~header_sender/*&<&'options'&> .cindex "&%verify%& ACL condition" .cindex "&ACL;" "verifying sender in the header" @@ -28634,6 +28651,13 @@ deny condition = ${if isip4{$sender_host_address}} dnslists = some.list.example .endd +If an explicit key is being used for a DNS lookup and it may be an IPv6 +address you should specify alternate list separators for both the outer +(DNS list name) list and inner (lookup keys) list: +.code + dnslists = <; dnsbl.example.com/<|$acl_m_addrslist +.endd + .section "Rate limiting incoming messages" "SECTratelimiting" .cindex "rate limiting" "client sending" .cindex "limiting client sending rates" @@ -29015,6 +29039,7 @@ router that does not set up hosts routes to an &(smtp)& transport with a &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has &%hosts_override%& set, its hosts are always used, whether or not the router supplies a host list. +Callouts are only supported on &(smtp)& transports. The port that is used is taken from the transport, if it is specified and is a remote transport. (For routers that do verification only, no transport need be @@ -29036,10 +29061,8 @@ following SMTP commands are sent: LHLO is used instead of HELO if the transport's &%protocol%& option is set to &"lmtp"&. -.new The callout may use EHLO, AUTH and/or STARTTLS given appropriate option settings. -.wen A recipient callout check is similar. By default, it also uses an empty address for the sender. This default is chosen because most hosts do not make use of @@ -29721,7 +29744,6 @@ Exim does not assume that there is a common filesystem with the remote host. There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should you be running a version of ClamAV prior to 0.95. -.new The final example shows that multiple TCP targets can be specified. Exim will randomly use one for each incoming email (i.e. it load balances them). Note that only TCP targets may be used if specifying a list of scanners; a UNIX @@ -29736,7 +29758,6 @@ email that the down scanner gets chosen first (message wrapped to be readable): clamd: connection to localhost, port 3310 failed (Connection refused) .endd -.wen If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for contributing the code for this scanner. @@ -29822,6 +29843,24 @@ av_scanner = mksd:2 .endd You can safely omit this option (the default value is 1). +.vitem &%sock%& +.cindex "virus scanners" "simple socket-connected" +This is a general-purpose way of talking to simple scanner daemons +running on the local machine. +There are four options: +an address (which may be an IP addres and port, or the path of a Unix socket), +a commandline to send (may include a single %s which will be replaced with +the path to the mail file to be scanned), +an RE to trigger on from the returned data, +an RE to extract malware_name from the returned data. +For example: +.code +av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$ +.endd +Default for the socket specifier is &_/tmp/malware.sock_&. +Default for the commandline is &_%s\n_&. +Both regular-expressions are required. + .vitem &%sophie%& .cindex "virus scanners" "Sophos and Sophie" Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses. @@ -31953,11 +31992,9 @@ headers_add = X-added-header: added by $primary_hostname\n\ .endd Exim does not check the syntax of these added header lines. -.new Multiple &%headers_add%& options for a single router or transport can be specified; the values will be concatenated (with a separating newline added) before expansion. -.wen The result of expanding &%headers_remove%& must consist of a colon-separated list of header names. This is confusing, because header names themselves are @@ -33834,9 +33871,7 @@ timestamp. The flags are: &`<=`& message arrival &`=>`& normal message delivery &`->`& additional address in same delivery -.new &`>>`& cutthrough message delivery -.wen &`*>`& delivery suppressed by &%-N%& &`**`& delivery failed; address bounced &`==`& delivery deferred; temporary problem @@ -33936,12 +33971,10 @@ intermediate address(es) exist between the original and the final address, the last of these is given in parentheses after the final address. The R and T fields record the router and transport that were used to process the address. -.new If SMTP AUTH was used for the delivery there is an additional item A= followed by the name of the authenticator that was used. If an authenticated identification was set up by the authenticator's &%client_set_id%& option, this is logged too, separated by a colon from the authenticator name. -.wen If a shadow transport was run after a successful local delivery, the log line for the successful delivery has an item added on the end, of the form @@ -33958,13 +33991,11 @@ flagged with &`->`& instead of &`=>`&. When two or more messages are delivered down a single SMTP connection, an asterisk follows the IP address in the log lines for the second and subsequent messages. -.new .cindex "delivery" "cutthrough; logging" .cindex "cutthrough" "logging" When delivery is done in cutthrough mode it is flagged with &`>>`& and the log line precedes the reception line, since cutthrough waits for a possible rejection from the destination in case it can reject the sourced item. -.wen The generation of a reply message by a filter file gets logged as a &"delivery"& to the addressee, preceded by &">"&. @@ -34076,6 +34107,7 @@ the following table: &`R `& on &`<=`& lines: reference for local bounce &` `& on &`=>`& &`**`& and &`==`& lines: router name &`S `& size of message +&`SNI `& server name indication from TLS client hello &`ST `& shadow transport name &`T `& on &`<=`& lines: message subject (topic) &` `& on &`=>`& &`**`& and &`==`& lines: transport name @@ -34142,9 +34174,7 @@ log_selector = +arguments -retry_defer The list of optional log items is in the following table, with the default selection marked by asterisks: .display -.new &` 8bitmime `& received 8BITMIME status -.wen &`*acl_warn_skipped `& skipped &%warn%& statement in ACL &` address_rewrite `& address rewriting &` all_parents `& all parents in => lines @@ -34174,14 +34204,10 @@ selection marked by asterisks: &`*sender_verify_fail `& sender verification failures &`*size_reject `& rejection because too big &`*skip_delivery `& delivery skipped in a queue run -.new &`*smtp_confirmation `& SMTP confirmation on => lines -.wen &` smtp_connection `& SMTP connections &` smtp_incomplete_transaction`& incomplete SMTP transactions -.new &` smtp_mailauth `& AUTH argument to MAIL commands -.wen &` smtp_no_mail `& session with no MAIL commands &` smtp_protocol_error `& SMTP protocol errors &` smtp_syntax_error `& SMTP syntax errors @@ -34197,7 +34223,6 @@ selection marked by asterisks: More details on each of these items follows: .ilist -.new .cindex "8BITMIME" .cindex "log" "8BITMIME" &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages, @@ -34205,7 +34230,6 @@ which may help in tracking down interoperability issues with ancient MTAs that are not 8bit clean. This is added to the &"<="& line, tagged with &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given", &`7BIT`& and &`8BITMIME`& respectively. -.wen .next .cindex "&%warn%& ACL verb" "log when skipping" &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of @@ -34393,7 +34417,8 @@ The message that is written is &"spool file is locked"&. .next .cindex "log" "smtp confirmation" .cindex "SMTP" "logging confirmation" -&%smtp_confirmation%&: The response to the final &"."& in the SMTP dialogue for +.cindex "LMTP" "logging confirmation" +&%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>. A number of MTAs (including Exim) return an identifying string in this response. @@ -34452,12 +34477,10 @@ the last 20 are listed, preceded by &"..."&. However, with the default setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case have been aborted before 20 non-mail commands are processed. .next -.new &%smtp_mailauth%&: A third subfield with the authenticated sender, colon-separated, is appended to the A= item for a message arrival or delivery log line, if an AUTH argument to the SMTP MAIL command (see &<>&) was accepted or used. -.wen .next .cindex "log" "SMTP protocol error" .cindex "SMTP" "logging protocol error" @@ -35861,8 +35884,9 @@ are given in chapter &<>&. -.new .section "Running local commands" "SECTsecconslocalcmds" +.cindex "security" "local commands" +.cindex "security" "command injection attacks" There are a number of ways in which an administrator can configure Exim to run commands based upon received, untrustworthy, data. Further, in some configurations a user who can control a &_.forward_& file can also arrange to @@ -35903,7 +35927,39 @@ real-world security vulnerabilities caused by its use with untrustworthy data injected in, for SQL injection attacks. Consider the use of the &%inlisti%& expansion condition instead. .endlist -.wen + + + + +.section "Trust in configuration data" "SECTsecconfdata" +.cindex "security" "data sources" +.cindex "security" "regular expressions" +.cindex "regular expressions" "security" +.cindex "PCRE" "security" +If configuration data for Exim can come from untrustworthy sources, there +are some issues to be aware of: + +.ilist +Use of &%${expand...}%& may provide a path for shell injection attacks. +.next +Letting untrusted data provide a regular expression is unwise. +.next +Using &%${match...}%& to apply a fixed regular expression against untrusted +data may result in pathological behaviour within PCRE. Be aware of what +"backtracking" means and consider options for being more strict with a regular +expression. Avenues to explore include limiting what can match (avoiding &`.`& +when &`[a-z0-9]`& or other character class will do), use of atomic grouping and +possessive quantifiers or just not using regular expressions against untrusted +data. +.next +It can be important to correctly use &%${quote:...}%&, +&%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion +items to ensure that data is correctly constructed. +.next +Some lookups might return multiple results, even though normal usage is only +expected to yield one result. +.endlist + @@ -36379,7 +36435,9 @@ disabled by setting DISABLE_DKIM=yes in Local/Makefile. Exim's DKIM implementation allows to .olist Sign outgoing messages: This function is implemented in the SMTP transport. -It can co-exist with all other Exim features, including transport filters. +It can co-exist with all other Exim features +(including transport filters) +except cutthrough delivery. .next Verify signatures in incoming messages: This is implemented by an additional ACL (acl_smtp_dkim), which can be called several times per message, with @@ -36470,6 +36528,10 @@ used. Verification of DKIM signatures in incoming email is implemented via the &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each syntactically(!) correct signature in the incoming message. +A missing ACL definition defaults to accept. +If any ACL call does not acccept, the message is not accepted. +If a cutthrough delivery was in progress for the message it is +summarily dropped (having wasted the transmission effort). To evaluate the signature in the ACL a large number of expansion variables containing the signature status and its details are set up during the @@ -36661,13 +36723,11 @@ Add to &_src/config.h.defaults_& the line: Edit &_src/drtables.c_&, adding conditional code to pull in the private header and create a table entry as is done for all the other drivers and lookup types. .next -.new Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop near the bottom, ranging the &`name_mod`& variable over a list of all lookups. Add your &`NEWDRIVER`& to that list. As long as the dynamic module would be named &_newdriver.so_&, you can use the simple form that most lookups have. -.wen .next Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&, &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new