X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/fcc8e04755fd6f211fd636e6c077ac41963ab0b9..exim-4_83_RC1:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 842dd8ffd..990df6241 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2012 +2014 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -179,12 +179,7 @@ EximMaintainers EM - -.version - - -.fulldate - +.versiondatexml EM @@ -544,7 +539,6 @@ The &_.bz2_& file is usually a lot smaller than the &_.gz_& file. .cindex "distribution" "signing details" .cindex "distribution" "public key" .cindex "public key for signed distribution" -.new The distributions will be PGP signed by an individual key of the Release Coordinator. This key will have a uid containing an email address in the &'exim.org'& domain and will have signatures from other people, including @@ -558,7 +552,10 @@ At time of last update, releases were being made by Phil Pennock and signed with 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). -.wen + +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. The signatures for the tar bundles are in: .display @@ -1381,8 +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. -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. -Again, cutthrough delibery 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%&" @@ -4235,6 +4221,20 @@ option sets the IP interface address value. A port number may be included, using the same syntax as for &%-oMa%&. The interface address is placed in &$received_ip_address$& and the port number, if present, in &$received_port$&. +.vitem &%-oMm%&&~<&'message&~reference'&> +.oindex "&%-oMm%&" +.cindex "message reference" "message reference, specifying for local message" +See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%& +option sets the message reference, e.g. message-id, and is logged during +delivery. This is useful when some kind of audit trail is required to tie +messages together. The format of the message reference is checked and will +abort if the format is invalid. The option will only be accepted if exim is +running in trusted mode, not as any regular user. + +The best example of a message reference is when Exim sends a bounce message. +The message reference is the message-id of the original message for which Exim +is sending the bounce. + .vitem &%-oMr%&&~<&'protocol&~name'&> .oindex "&%-oMr%&" .cindex "protocol, specifying for local message" @@ -4636,12 +4636,10 @@ 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 @@ -5559,16 +5557,21 @@ unreachable. The next two lines are concerned with &'ident'& callbacks, as defined by RFC 1413 (hence their names): .code -rfc1413_hosts = * -rfc1413_query_timeout = 5s +rfc1413_query_hosts = * +rfc1413_query_timeout = 0s +.endd +These settings cause Exim to avoid ident callbacks for all incoming SMTP calls. +Few hosts offer RFC1413 service these days; calls have to be +terminated by a timeout and this needlessly delays the startup +of an incoming SMTP connection. +If you have hosts for which you trust RFC1413 and need this +information, you can change this. + +This line enables an efficiency SMTP option. It is negociated by clients +and not expected to cause problems but can be disabled if needed. +.code +prdr_enable = true .endd -These settings cause Exim to make ident callbacks for all incoming SMTP calls. -You can limit the hosts to which these calls are made, or change the timeout -that is used. If you set the timeout to zero, all ident calls are disabled. -Although they are cheap and can provide useful information for tracing problem -messages, some hosts and firewalls have problems with ident calls. This can -result in a timeout instead of an immediate refused connection, leading to -delays on starting up an incoming SMTP session. When Exim receives messages over SMTP connections, it expects all addresses to be fully qualified with a domain, as required by the SMTP definition. However, @@ -6004,9 +6007,14 @@ One remote transport and four local transports are defined. .code remote_smtp: driver = smtp + hosts_try_prdr = * .endd -This transport is used for delivering messages over SMTP connections. All its -options are defaulted. The list of remote hosts comes from the router. +This transport is used for delivering messages over SMTP connections. +The list of remote hosts comes from the router. +The &%hosts_try_prdr%& option enables an efficiency SMTP option. +It is negotiated between client and server +and not expected to cause problems but can be disabled if needed. +All other options are defaulted. .code local_delivery: driver = appendfile @@ -6856,7 +6864,7 @@ is used on its own as the result. If the lookup does not succeed, the &`fail`& keyword causes a &'forced expansion failure'& &-- see section &<>& for an explanation of what this means. -The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT, +The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT, and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also configured). If no type is given, TXT is assumed. When the type is PTR, the data can be an IP address, written as normal; inversion and the addition of @@ -6975,11 +6983,16 @@ The data from each lookup is concatenated, with newline separators by default, in the same way that multiple DNS records for a single item are handled. A different separator can be specified, as described above. +Modifiers for &(dnsdb)& lookups are givien by optional keywords, +each followed by a comma, +that may appear before the record type. + The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a temporary DNS error for any of them, the behaviour is controlled by -an optional keyword followed by a comma that may appear before the record -type. The possible keywords are &"defer_strict"&, &"defer_never"&, and -&"defer_lax"&. With &"strict"& behaviour, any temporary DNS error causes the +a defer-option modifier. +The possible keywords are +&"defer_strict"&, &"defer_never"&, and &"defer_lax"&. +With &"strict"& behaviour, any temporary DNS error causes the whole lookup to defer. With &"never"& behaviour, a temporary DNS error is ignored, and the behaviour is as if the DNS lookup failed to find anything. With &"lax"& behaviour, all the queries are attempted, but a temporary DNS @@ -6992,6 +7005,21 @@ ${lookup dnsdb{a=one.host.com:two.host.com}} Thus, in the default case, as long as at least one of the DNS lookups yields some data, the lookup succeeds. +.new +.cindex "DNSSEC" "dns lookup" +Use of &(DNSSEC)& is controlled by a dnssec modifier. +The possible keywords are +&"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&. +With &"strict"& or &"lax"& DNSSEC information is requested +with the lookup. +With &"strict"& a response from the DNS resolver that +is not labelled as authenticated data +is treated as equivalent to a temporary DNS error. +The default is &"never"&. + +See also the &$lookup_dnssec_authenticated$& variable. +.wen + @@ -7056,6 +7084,18 @@ 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" @@ -7202,6 +7242,9 @@ them. The following names are recognized: &`USER `& set the DN, for authenticating the LDAP bind &`PASS `& set the password, likewise &`REFERRALS `& set the referrals parameter +.new +&`SERVERS `& set alternate server list for this query only +.wen &`SIZE `& set the limit for the number of entries returned &`TIME `& set the maximum waiting time for a query .endd @@ -7223,6 +7266,15 @@ Netscape SDK; for OpenLDAP no action is taken. The TIME parameter (also a number of seconds) is passed to the server to set a server-side limit on the time taken to complete a search. +.new +The SERVERS parameter allows you to specify an alternate list of ldap servers +to use for an individual lookup. The global ldap_servers option provides a +default list of ldap servers, and a single lookup can specify a single ldap +server to use. But when you need to do a lookup with a list of servers that is +different than the default list (maybe different order, maybe a completely +different set of servers), the SERVERS parameter allows you to specify this +alternate list. +.wen Here is an example of an LDAP query in an Exim lookup that uses some of these values. This is a single line, folded to fit on the page: @@ -8268,10 +8320,13 @@ apply to temporary DNS errors, whose handling is described in the next section. .cindex "&`+include_unknown`&" .cindex "&`+ignore_unknown`&" -By default, Exim behaves as if the host does not match the list. This may not -always be what you want to happen. To change Exim's behaviour, the special -items &`+include_unknown`& or &`+ignore_unknown`& may appear in the list (at -top level &-- they are not recognized in an indirected file). +Exim parses a host list from left to right. If it encounters a permanent +lookup failure in any item in the host list before it has found a match, +Exim treats it as a failure and the default behavior is as if the host +does not match the list. This may not always be what you want to happen. +To change Exim's behaviour, the special items &`+include_unknown`& or +&`+ignore_unknown`& may appear in the list (at top level &-- they are +not recognized in an indirected file). .ilist If any item that follows &`+include_unknown`& requires information that @@ -8299,6 +8354,44 @@ 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 +.section "Mixing wildcarded host names and addresses in host lists" &&& + "SECTmixwilhos" +.cindex "host list" "mixing names and addresses in" + +This section explains the host/ip processing logic with the same concepts +as the previous section, but specifically addresses what happens when a +wildcarded hostname is one of the items in the hostlist. + +.ilist +If you have name lookups or wildcarded host names and +IP addresses in the same host list, you should normally put the IP +addresses first. For example, in an ACL you could have: +.code +accept hosts = 10.9.8.7 : *.friend.example +.endd +The reason you normally would order it this way lies in the +left-to-right way that Exim processes lists. It can test IP addresses +without doing any DNS lookups, but when it reaches an item that requires +a host name, it fails if it cannot find a host name to compare with the +pattern. If the above list is given in the opposite order, the +&%accept%& statement fails for a host whose name cannot be found, even +if its IP address is 10.9.8.7. + +.next +If you really do want to do the name check first, and still recognize the IP +address, you can rewrite the ACL like this: +.code +accept hosts = *.friend.example +accept hosts = 10.9.8.7 +.endd +If the first &%accept%& fails, Exim goes on to try the second one. See chapter +&<>& for details of ACLs. Alternatively, you can use +&`+ignore_unknown`&, which was discussed in depth in the first example in +this section. +.endlist +.wen + .section "Temporary DNS errors when looking up host information" &&& "SECTtemdnserr" @@ -8369,33 +8462,6 @@ See section &<>&.) -.section "Mixing wildcarded host names and addresses in host lists" &&& - "SECTmixwilhos" -.cindex "host list" "mixing names and addresses in" -If you have name lookups or wildcarded host names and IP addresses in the same -host list, you should normally put the IP addresses first. For example, in an -ACL you could have: -.code -accept hosts = 10.9.8.7 : *.friend.example -.endd -The reason for this lies in the left-to-right way that Exim processes lists. -It can test IP addresses without doing any DNS lookups, but when it reaches an -item that requires a host name, it fails if it cannot find a host name to -compare with the pattern. If the above list is given in the opposite order, the -&%accept%& statement fails for a host whose name cannot be found, even if its -IP address is 10.9.8.7. - -If you really do want to do the name check first, and still recognize the IP -address, you can rewrite the ACL like this: -.code -accept hosts = *.friend.example -accept hosts = 10.9.8.7 -.endd -If the first &%accept%& fails, Exim goes on to try the second one. See chapter -&<>& for details of ACLs. - - - .section "Address lists" "SECTaddresslist" @@ -8819,6 +8885,71 @@ the expansion result is an empty string. If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails. +.new +.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&& + {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" +.cindex "expansion" "extracting cerificate fields" +.cindex "&%certextract%&" "certificate fields" +.cindex "certificate" "extracting fields" +The <&'certificate'&> must be a variable of type certificate. +The field name is expanded and used to retrive the relevant field from +the certificate. Supported fields are: +.display +&`version `& +&`serial_number `& +&`subject `& RFC4514 DN +&`issuer `& RFC4514 DN +&`notbefore `& time +&`notafter `& time +&`sig_algorithm `& +&`signature `& +&`subj_altname `& tagged list +&`ocsp_uri `& list +&`crl_uri `& list +.endd +If the field is found, +<&'string2'&> is expanded, and replaces the whole item; +otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the +variable &$value$& contains the value that has been extracted. Afterwards, it +is restored to any previous value it might have had. + +If {<&'string3'&>} is omitted, the item is replaced by an empty string if the +key is not found. If {<&'string2'&>} is also omitted, the value that was +extracted is used. + +Some field names take optional modifiers, appended and separated by commas. + +The field selectors marked as "RFC4514" above +output a Distinguished Name string which is +not quite +parseable by Exim as a comma-separated tagged list +(the exceptions being elements containin commas). +RDN elements of a single type may be selected by +a modifier of the type label; if so the expansion +result is a list (newline-separated by default). +The separator may be changed by another modifer of +a right angle-bracket followed immediately by the new separator. +Recognised RDN type labels include "CN", "O", "OU" and "DC". + +The field selectors marked as "time" above +may output a number of seconds since epoch +if the modifier "int" is used. + +The field selectors marked as "list" above return a list, +newline-separated by default, +(embedded separator characters in elements are doubled). +The separator may be changed by a modifier of +a right angle-bracket followed immediately by the new separator. + +The field selectors marked as "tagged" above +prefix each list element with a type string and an equals sign. +Elements of only one type may be selected by a modifier +which is one of "dns", "uri" or "mail"; +if so the elenment tags are omitted. + +If not otherwise noted field values are presented in human-readable form. +.wen + .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&& {*&<&'arg'&>&*}...}*&" .cindex &%dlfunc%& @@ -9151,6 +9282,44 @@ of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with &%strlen%&, which gives the length of a string. +.vitem "&*${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 @@ -9623,6 +9792,29 @@ expansion item, which extracts the working address from a single RFC2822 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of processing lists. +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 +email address seperator. For the example header line: +.code +From: =?iso-8859-2?Q?Last=2C_First?= +.endd +The first example below demonstrates that Q-encoded email addresses are parsed +properly if it is given the raw header (in this example, &`$rheader_from:`&). +It does not see the comma because it's still encoded as "=2C". The second +example below is passed the contents of &`$header_from:`&, meaning it gets +de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses. +The third example shows that the presence of a comma is skipped when it is +quoted. +.code +# exim -be '${addresses:From: \ +=?iso-8859-2?Q?Last=2C_First?= }' +user@example.com +# exim -be '${addresses:From: Last, First }' +Last:user@example.com +# exim -be '${addresses:From: "Last, First" }' +user@example.com +.endd .vitem &*${base62:*&<&'digits'&>&*}*& .cindex "&%base62%& expansion item" @@ -9777,6 +9969,16 @@ This operator converts a hex string into one that is base64 encoded. This can be useful for processing the output of the MD5 and SHA-1 hashing functions. + +.vitem &*${hexquote:*&<&'string'&>&*}*& +.cindex "quoting" "hex-encoded unprintable characters" +.cindex "&%hexquote%& expansion item" +This operator converts non-printable characters in a string into a hex +escape form. Byte values between 33 (!) and 126 (~) inclusive are left +as is, and other byte values are converted to &`\xNN`&, for example a +byte value 127 is converted to &`\x7f`&. + + .vitem &*${lc:*&<&'string'&>&*}*& .cindex "case forcing in strings" .cindex "string" "case forcing" @@ -9810,12 +10012,12 @@ when &%length%& is used as an operator. The string is interpreted as a list and the number of items is returned. -.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${list_*&<&'type'&>&*name*&>&*}*& +.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*& .cindex "expansion" "named list" .cindex "&%listnamed%& expansion item" The name is interpreted as a named list and the content of the list is returned, expanding any referenced lists, re-quoting as needed for colon-separation. -If the optional type if given it must be one of "a", "d", "h" or "l" +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. @@ -9860,6 +10062,7 @@ Letters in IPv6 addresses are always output in lower case. .vitem &*${md5:*&<&'string'&>&*}*& .cindex "MD5 hash" .cindex "expansion" "MD5 hash" +.cindex "certificate fingerprint" .cindex "&%md5%& expansion item" The &%md5%& operator computes the MD5 hash value of the string, and returns it as a 32-digit hexadecimal number, in which any letters are in lower case. @@ -9997,11 +10200,24 @@ variables or headers inside regular expressions. .vitem &*${sha1:*&<&'string'&>&*}*& .cindex "SHA-1 hash" .cindex "expansion" "SHA-1 hashing" +.cindex "certificate fingerprint" .cindex "&%sha2%& expansion item" The &%sha1%& operator computes the SHA-1 hash value of the string, and returns it as a 40-digit hexadecimal number, in which any letters are in upper case. +.vitem &*${sha256:*&<&'certificate'&>&*}*& +.cindex "SHA-256 hash" +.cindex "certificate fingerprint" +.cindex "expansion" "SHA-256 hashing" +.cindex "&%sha256%& expansion item" +The &%sha256%& operator computes the SHA-256 hash fingerprint of the +certificate, +and returns +it as a 64-digit hexadecimal number, in which any letters are in upper case. +Only arguments which are a single variable of certificate type are supported. + + .vitem &*${stat:*&<&'string'&>&*}*& .cindex "expansion" "statting a file" .cindex "file" "extracting characteristics" @@ -10070,6 +10286,14 @@ 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 @@ -10138,7 +10362,7 @@ If the ACL returns defer the result is a forced-fail. .cindex "&%bool%& expansion condition" This condition turns a string holding a true or false representation into a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"& -(case-insensitively); also positive integer numbers map to true if non-zero, +(case-insensitively); also integer numbers map to true if non-zero, false if zero. An empty string is treated as false. Leading and trailing whitespace is ignored; @@ -10327,6 +10551,8 @@ ${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. +To scan a named list, expand it with the &*listnamed*& operator. + .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -10870,7 +11096,16 @@ 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. - +.vitem &$authenticated_fail_id$& +.cindex "authentication" "fail" "id" +.vindex "&$authenticated_fail_id$&" +When an authentication attempt fails, the variable &$authenticated_fail_id$& +will contain the failed authentication id. If more than one authentication +id is attempted, it will contain only the last one. The variable is +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. .vitem &$authenticated_sender$& @@ -11321,6 +11556,16 @@ ability to find the amount of free space (only true for experimental systems), the space value is -1. See also the &%check_log_space%& option. +.new +.vitem &$lookup_dnssec_authenticated$& +.vindex "&$lookup_dnssec_authenticated$&" +This variable is set after a DNS lookup done by +a dnsdb lookup expansion, dnslookup router or smtp transport. +It will be empty if &(DNSSEC)& was not requested, +&"no"& if the result was not labelled as authenticated data +and &"yes"& if it was. +.wen + .vitem &$mailstore_basename$& .vindex "&$mailstore_basename$&" This variable is set only when doing deliveries in &"mailstore"& format in the @@ -11856,7 +12101,6 @@ 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 @@ -11867,7 +12111,7 @@ 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 @@ -11878,7 +12122,6 @@ 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 &$sender_host_name$& @@ -12099,6 +12342,44 @@ on an outbound SMTP connection; the meaning of this depends upon the TLS implementation used. If TLS has not been negotiated, the value will be 0. +.new +.vitem &$tls_in_ourcert$& +.vindex "&$tls_in_ourcert$&" +This variable refers to the certificate presented to the peer of an +inbound connection when the message was received. +It is only useful as the argument of a +&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +or a &%def%& condition. +.wen + +.new +.vitem &$tls_in_peercert$& +.vindex "&$tls_in_peercert$&" +This variable refers to the certificate presented by the peer of an +inbound connection when the message was received. +It is only useful as the argument of a +&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +or a &%def%& condition. +.wen + +.new +.vitem &$tls_out_ourcert$& +.vindex "&$tls_out_ourcert$&" +This variable refers to the certificate presented to the peer of an +outbound connection. It is only useful as the argument of a +&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +or a &%def%& condition. +.wen + +.new +.vitem &$tls_out_peercert$& +.vindex "&$tls_out_peercert$&" +This variable refers to the certificate presented by the peer of an +outbound connection. It is only useful as the argument of a +&%certextract%& expansion item, &%md5%& or &%sha1%& operator, +or a &%def%& condition. +.wen + .vitem &$tls_in_certificate_verified$& .vindex "&$tls_in_certificate_verified$&" This variable is set to &"1"& if a TLS certificate was verified when the @@ -12880,6 +13161,7 @@ listed in more than one group. .row &%acl_smtp_auth%& "ACL for AUTH" .row &%acl_smtp_connect%& "ACL for connection" .row &%acl_smtp_data%& "ACL for DATA" +.row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient" .row &%acl_smtp_dkim%& "ACL for DKIM verification" .row &%acl_smtp_etrn%& "ACL for ETRN" .row &%acl_smtp_expn%& "ACL for EXPN" @@ -12933,13 +13215,14 @@ listed in more than one group. .section "TLS" "SECID108" .table2 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode" -.row &%gnutls_enable_pkcs11%& "allow GnuTLS to autoload PKCS11 modules" +.row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules" .row &%openssl_options%& "adjust OpenSSL compatibility options" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .row &%tls_certificate%& "location of server certificate" .row &%tls_crl%& "certificate revocation list" .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion" .row &%tls_dhparam%& "DH parameters for server" +.row &%tls_ocsp_file%& "location of server certificate status proof" .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports" .row &%tls_privatekey%& "location of server private key" .row &%tls_remember_esmtp%& "don't reset after starting TLS" @@ -13035,6 +13318,7 @@ See also the &'Policy controls'& section above. .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts" .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP" .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts" +.row &%prdr_enable%& "advertise PRDR to all hosts" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .endtable @@ -13080,10 +13364,10 @@ 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" @@ -13186,6 +13470,16 @@ This option defines the ACL that is run after an SMTP DATA command has been processed and the message itself has been received, but before the final acknowledgment is sent. See chapter &<>& for further details. +.option acl_smtp_data_prdr main string&!! unset +.cindex "DATA" "ACL for" +.cindex "&ACL;" "PRDR-related" +.cindex "&ACL;" "per-user data processing" +This option defines the ACL that, +if the PRDR feature has been negotiated, +is run for each recipient after an SMTP DATA command has been +processed and the message itself has been received, but before the +acknowledgment is sent. See chapter &<>& for further details. + .option acl_smtp_etrn main string&!! unset .cindex "ETRN" "ACL for" This option defines the ACL that is run when an SMTP ETRN command is @@ -13580,6 +13874,9 @@ 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 "&$domain$&" @@ -13701,6 +13998,17 @@ 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" @@ -13731,18 +14039,6 @@ 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" @@ -13968,15 +14264,13 @@ server. This reduces security slightly, but improves interworking with older implementations of TLS. -.new -option gnutls_enable_pkcs11 main boolean unset +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/_&. See -&url(http://www.gnu.org/software/gnutls/manual/gnutls.html#Smart-cards-and-HSMs) +&url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs) for documentation. -.wen @@ -14730,6 +15024,8 @@ Possible options may include: .next &`no_tlsv1_2`& .next +&`safari_ecdhe_ecdsa_bug`& +.next &`single_dh_use`& .next &`single_ecdh_use`& @@ -14745,6 +15041,13 @@ Possible options may include: &`tls_rollback_bug`& .endlist +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. + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" @@ -14819,6 +15122,15 @@ that clients will use it; &"out of order"& commands that are &"expected"& do not count as protocol errors (see &%smtp_max_synprot_errors%&). +.option prdr_enable main boolean false +.cindex "PRDR" "enabling on server" +This option can be used to enable the Per-Recipient Data Response extension +to SMTP, defined by Eric Hall. +If the option is set, PRDR is advertised by Exim when operating as a server. +If the client requests PRDR, and more than one recipient, for a message +an additional ACL is called for each recipient after the message content +is recieved. See section &<>&. + .option preserve_message_logs main boolean false .cindex "message logs" "preserving" If this option is set, message log files are not deleted when messages are @@ -15314,6 +15626,13 @@ live with. . Allow this long option name to split; give it unsplit as a fifth argument . for the automatic .oindex that is generated by .option. +. We insert " &~&~" which is both pretty nasty visually and results in +. non-searchable text. HowItWorks.txt mentions an option for inserting +. zero-width-space, which would be nicer visually and results in (at least) +. html that Firefox will split on when it's forced to reflow (rather than +. inserting a horizontal scrollbar). However, the text is still not +. searchable. NM changed this occurrence for bug 1197 to no longer allow +. the option name to split. .option "smtp_accept_max_per_connection" main integer 1000 &&& smtp_accept_max_per_connection @@ -15365,10 +15684,9 @@ also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the various &%-od%&&'x'& command line options. -. Allow this long option name to split; give it unsplit as a fifth argument -. for the automatic .oindex that is generated by .option. +. See the comment on smtp_accept_max_per_connection -.option "smtp_accept_queue_per_ &~&~connection" main integer 10 &&& +.option "smtp_accept_queue_per_connection" main integer 10 &&& smtp_accept_queue_per_connection .cindex "queueing incoming messages" .cindex "message" "queueing by message count" @@ -16008,6 +16326,28 @@ 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. +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 +tell the server what these constraints are. Thus, as a server operator, you +need to make an educated guess as to what is most likely to work for your +userbase. + +Some known size constraints suggest that a bit-size in the range 2048 to 2236 +is most likely to maximise interoperability. The upper bound comes from +applications using the Mozilla Network Security Services (NSS) library, which +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. + + +.option tls_ocsp_file main string&!! unset +This option +must if set expand to the absolute path to a file which contains a current +status proof for the server's certificate, as obtained from the +Certificate Authority. + .option tls_on_connect_ports main "string list" unset This option specifies a list of incoming SSMTP (aka SMTPS) ports that should @@ -16599,11 +16939,12 @@ and the discussion in chapter &<>&. -.option headers_add routers string&!! unset +.option headers_add routers list&!! unset .cindex "header lines" "adding" .cindex "router" "adding header lines" -This option specifies a string of text that is expanded at routing time, and -associated with any addresses that are accepted by the router. However, this +This option specifies a list of text headers, newline-separated, +that is associated with any addresses that are accepted by the router. +Each item is separately expanded, at routing time. However, this option has no effect when an address is just being verified. The way in which the text is used to add header lines at transport time is described in section &<>&. New header lines are not actually added until the @@ -16612,8 +16953,8 @@ header lines in string expansions in the transport's configuration do not &"see"& the added header lines. The &%headers_add%& option is expanded after &%errors_to%&, but before -&%headers_remove%& and &%transport%&. If the expanded string is empty, or if -the expansion is forced to fail, the option has no effect. Other expansion +&%headers_remove%& and &%transport%&. If an item is empty, or if +an item expansion is forced to fail, the item has no effect. Other expansion failures are treated as configuration errors. Unlike most options, &%headers_add%& can be specified multiple times @@ -16635,11 +16976,12 @@ avoided. The &%repeat_use%& option of the &%redirect%& router may be of help. -.option headers_remove routers string&!! unset +.option headers_remove routers list&!! unset .cindex "header lines" "removing" .cindex "router" "removing header lines" -This option specifies a string of text that is expanded at routing time, and -associated with any addresses that are accepted by the router. However, this +This option specifies a list of text headers, colon-separated, +that is associated with any addresses that are accepted by the router. +Each item is separately expanded, at routing time. However, this option has no effect when an address is just being verified. The way in which the text is used to remove header lines at transport time is described in section &<>&. Header lines are not actually removed until @@ -16648,8 +16990,8 @@ to header lines in string expansions in the transport's configuration still &"see"& the original header lines. The &%headers_remove%& option is expanded after &%errors_to%& and -&%headers_add%&, but before &%transport%&. If the expansion is forced to fail, -the option has no effect. Other expansion failures are treated as configuration +&%headers_add%&, but before &%transport%&. If an item expansion is forced to fail, +the item has no effect. Other expansion failures are treated as configuration errors. Unlike most options, &%headers_remove%& can be specified multiple times @@ -17492,6 +17834,33 @@ when there is a DNS lookup error. +.new +.option dnssec_request_domains dnslookup "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. +This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +.wen + + + +.new +.option dnssec_require_domains dnslookup "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. Any returns not having the Authenticated Data bit +(AD bit) set wil be ignored and logged as a host-lookup failure. +This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +.wen + + + .option mx_domains dnslookup "domain list&!!" unset .cindex "MX record" "required to exist" .cindex "SRV record" "required to exist" @@ -18663,7 +19032,6 @@ 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 @@ -18673,7 +19041,6 @@ 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" @@ -19618,7 +19985,6 @@ one. The variables &$transport_name$& and &$router_name$& contain the name of the transport and the router that called it. - .option delivery_date_add transports boolean false .cindex "&'Delivery-date:'& header line" If this option is true, a &'Delivery-date:'& header is added to the message. @@ -19652,10 +20018,11 @@ value that the router supplies, and also overriding any value associated with &%user%& (see below). -.option headers_add transports string&!! unset +.option headers_add transports list&!! unset .cindex "header lines" "adding in transport" .cindex "transport" "header lines; adding" -This option specifies a string of text that is expanded and added to the header +This option specifies a list of text headers, newline-separated, +which are (separately) expanded and added to the header portion of a message as it is transported, as described in section &<>&. Additional header lines can also be specified by routers. If the result of the expansion is an empty string, or if the expansion @@ -19666,7 +20033,6 @@ Unlike most options, &%headers_add%& can be specified multiple times for a transport; all listed headers are added. - .option headers_only transports boolean false .cindex "transport" "header lines only" .cindex "message" "transporting headers only" @@ -19677,18 +20043,20 @@ transports, the settings of &%message_prefix%& and &%message_suffix%& should be checked, since this option does not automatically suppress them. -.option headers_remove transports string&!! unset +.option headers_remove transports list&!! unset .cindex "header lines" "removing" .cindex "transport" "header lines; removing" -This option specifies a string that is expanded into a list of header names; +This option specifies a list of header names, colon-separated; these headers are omitted from the message as it is transported, as described in section &<>&. Header removal can also be specified by -routers. If the result of the expansion is an empty string, or if the expansion +routers. +Each list item is separately expanded. +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. Unlike most options, &%headers_remove%& can be specified multiple times -for a router; all listed headers are added. +for a router; all listed headers are removed. @@ -22397,6 +22765,32 @@ details. .new +.option dnssec_request_domains smtp "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. +This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +.wen + + + +.new +.option dnssec_require_domains smtp "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. Any returns not having the Authenticated Data bit +(AD bit) set wil be ignored and logged as a host-lookup failure. +This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +.wen + + + .option dscp smtp string&!! unset .cindex "DCSP" "outbound" This option causes the DSCP value associated with a socket to be set to one @@ -22410,7 +22804,6 @@ 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 @@ -22620,6 +23013,18 @@ hard failure if required. See also &%hosts_try_auth%&, and chapter &<>& for details of authentication. +.option hosts_request_ocsp smtp "host list&!!" * +.cindex "TLS" "requiring for certain servers" +Exim will request a Certificate Status on a +TLS session for any host that matches this list. +&%tls_verify_certificates%& should also be set for the transport. + +.option hosts_require_ocsp smtp "host list&!!" unset +.cindex "TLS" "requiring for certain servers" +Exim will request, and check for a valid Certificate Status being given, on a +TLS session for any host that matches this list. +&%tls_verify_certificates%& should also be set for the transport. + .option hosts_require_tls smtp "host list&!!" unset .cindex "TLS" "requiring for certain servers" Exim will insist on using a TLS session when delivering to any host that @@ -22635,6 +23040,12 @@ connects. If authentication fails, Exim will try to transfer the message unauthenticated. See also &%hosts_require_auth%&, and chapter &<>& for details of authentication. +.option hosts_try_prdr smtp "host list&!!" unset +.cindex "PRDR" "enabling, optional in client" +This option provides a list of servers to which, provided they announce +PRDR support, Exim will attempt to negotiate PRDR +for multi-recipient messages. + .option interface smtp "string list&!!" unset .cindex "bind IP address" .cindex "IP address" "binding" @@ -22816,7 +23227,6 @@ 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 @@ -22826,7 +23236,6 @@ 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 @@ -22887,6 +23296,19 @@ 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" +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. +Note that unless the host is in this list +TLS connections will be denied to hosts using self-signed certificates +when &%tls_verify_certificates%& is set. +The &$tls_out_certificate_verified$& variable is set when +certificate verification succeeds. + + .option tls_verify_certificates smtp string&!! unset .cindex "TLS" "server certificate verification" .cindex "certificate" "verification of server" @@ -22901,6 +23323,20 @@ 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, +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" +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. + @@ -23527,7 +23963,7 @@ In practice, almost all rules start with a domain name pattern without a local part. .cindex "regular expressions" "in retry rules" -&*Warning*&: If you use a regular expression in a routing rule pattern, it +&*Warning*&: If you use a regular expression in a retry rule pattern, it must match a complete address, not just a domain, because that is how regular expressions work in address lists. .display @@ -24510,7 +24946,7 @@ to be returned. If the result of a successful expansion is an empty string, 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. +string as the error text &*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. @@ -24957,7 +25393,7 @@ dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-client - server_set_id = $auth2 + server_set_id = $auth1 dovecot_ntlm: driver = dovecot @@ -25386,12 +25822,10 @@ option). The &%tls_require_ciphers%& options operate differently, as described in the sections &<>& and &<>&. .next -.new The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS. When using OpenSSL, this option is ignored. (If an API is found to let OpenSSL be configured in this way, let the Exim Maintainers know and we'll likely use it). -.wen .next Some other recently added features may only be available in one or the other. This should be documented with the feature. If the documentation does not @@ -25574,10 +26008,10 @@ aware of future feature enhancements of GnuTLS. Documentation of the strings accepted may be found in the GnuTLS manual, under "Priority strings". This is online as -&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html), +&url(http://www.gnutls.org/manual/html_node/Priority-Strings.html), but beware that this relates to GnuTLS 3, which may be newer than the version installed on your system. If you are using GnuTLS 3, -&url(http://www.gnu.org/software/gnutls/manual/html_node/Listing-the-ciphersuites-in-a-priority-string.html, then the example code) +&url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, then the example code) on that site can be used to test a given string. Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three @@ -25663,7 +26097,7 @@ tls_dhparam = none This may also be set to a string identifying a standard prime to be used for DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime used is &`ike23`&. There are a few standard primes available, see the -documetnation for &%tls_dhparam%& for the complete list. +documentation for &%tls_dhparam%& for the complete list. See the command .code @@ -25750,12 +26184,79 @@ certificate is supplied, &$tls_in_peerdn$& is empty. .cindex "TLS" "revoked certificates" .cindex "revocation list" .cindex "certificate" "revocation list" +.cindex "OCSP" "stapling" Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when certificates are revoked. If you have such a list, you can pass it to an Exim server using the global option called &%tls_crl%& and to an Exim client using an identically named option for the &(smtp)& transport. In each case, the value of the option is expanded and must then be the name of a file that contains a CRL in PEM format. +The downside is that clients have to periodically re-download a potentially huge +file from every certificate authority the know of. + +The way with most moving parts at query time is Online Certificate +Status Protocol (OCSP), where the client verifies the certificate +against an OCSP server run by the CA. This lets the CA track all +usage of the certs. It requires running software with access to the +private key of the CA, to sign the responses to the OCSP queries. OCSP +is based on HTTP and can be proxied accordingly. + +The only widespread OCSP server implementation (known to this writer) +comes as part of OpenSSL and aborts on an invalid request, such as +connecting to the port and then disconnecting. This requires +re-entering the passphrase each time some random client does this. + +The third way is OCSP Stapling; in this, the server using a certificate +issued by the CA periodically requests an OCSP proof of validity from +the OCSP server, then serves it up inline as part of the TLS +negotiation. This approach adds no extra round trips, does not let the +CA track users, scales well with number of certs issued by the CA and is +resilient to temporary OCSP server failures, as long as the server +starts retrying to fetch an OCSP proof some time before its current +proof expires. The downside is that it requires server support. + +Unless Exim is built with the support disabled, +or with GnuTLS earlier than version 3.1.3, +support for OCSP stapling is included. + +There is a global option called &%tls_ocsp_file%&. +The file specified therein is expected to be in DER format, and contain +an OCSP proof. Exim will serve it as part of the TLS handshake. This +option will be re-expanded for SNI, if the &%tls_certificate%& option +contains &`tls_in_sni`&, as per other TLS options. + +Exim does not at this time implement any support for fetching a new OCSP +proof. The burden is on the administrator to handle this, outside of +Exim. The file specified should be replaced atomically, so that the +contents are always valid. Exim will expand the &%tls_ocsp_file%& option +on each connection, so a new file will be handled transparently on the +next connection. + +When built with OpenSSL Exim will check for a valid next update timestamp +in the OCSP proof; if not present, or if the proof has expired, it will be +ignored. + +For the client to be able to verify the stapled OCSP the server must +also supply, in its stapled information, any intermediate +certificates for the chain leading to the OCSP proof from the signer +of the server certificate. There may be zero or one such. These +intermediate certificates should be added to the server OCSP stapling +file named by &%tls_ocsp_file%&. + +Note that the proof only covers the terminal server certificate, +not any of the chain from CA to it. + +.code + A helper script "ocsp_fetch.pl" for fetching a proof from a CA + OCSP server is supplied. The server URL may be included in the + server certificate, if the CA is helpful. + + One failure mode seen was the OCSP Signer cert expiring before the end + of validity of the OCSP proof. The checking done by Exim/OpenSSL + noted this as invalid overall, but the re-fetch script did not. +.endd + + .section "Configuring an Exim client to use TLS" "SECID185" @@ -25804,6 +26305,25 @@ 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. + +The &(smtp)& transport has two OCSP-related options: +&%hosts_require_ocsp%&; a host-list for which a Certificate Status +is requested and required for the connection to proceed. The default +value is empty. +&%hosts_request_ocsp%&; a host-list for which (additionally) +a Certificate Status is requested (but not necessarily verified). The default +value is "*" meaning that requests are made unless configured +otherwise. + +The host(s) should also be in &%hosts_require_tls%&, and +&%tls_verify_certificates%& configured for the transport, +for OCSP to be relevant. If &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a @@ -25890,6 +26410,9 @@ during TLS session handshake, to permit alternative values to be chosen: .next .vindex "&%tls_verify_certificates%&" &%tls_verify_certificates%& +.next +.vindex "&%tls_ocsp_file%&" +&%tls_verify_certificates%& .endlist Great care should be taken to deal with matters of case, various injection @@ -25981,6 +26504,12 @@ 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" @@ -26092,6 +26621,7 @@ options in the main part of the configuration. These options are: .cindex "SMTP" "connection, ACL for" .cindex "non-SMTP messages" "ACLs for" .cindex "MIME content scanning" "ACL for" +.cindex "PRDR" "ACL for" .table2 140pt .irow &%acl_not_smtp%& "ACL for non-SMTP messages" @@ -26100,6 +26630,7 @@ options in the main part of the configuration. These options are: .irow &%acl_smtp_auth%& "ACL for AUTH" .irow &%acl_smtp_connect%& "ACL for start of SMTP connection" .irow &%acl_smtp_data%& "ACL after DATA is complete" +.irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete" .irow &%acl_smtp_etrn%& "ACL for ETRN" .irow &%acl_smtp_expn%& "ACL for EXPN" .irow &%acl_smtp_helo%& "ACL for HELO or EHLO" @@ -26214,9 +26745,10 @@ 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. -The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and -the &%acl_smtp_mime%& ACLs. - +The &%acl_smtp_data%& ACL is run after +the &%acl_smtp_data_prdr%&, +the &%acl_smtp_dkim%& +and the &%acl_smtp_mime%& ACLs. .section "The SMTP DKIM ACL" "SECTDKIMACL" The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support @@ -26238,6 +26770,36 @@ content-scanning extension. For details, see chapter &<>&. This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&. +.section "The SMTP PRDR ACL" "SECTPRDRACL" +.oindex "&%prdr_enable%&" +The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled +with PRDR support enabled (which is the default). +It becomes active only when the PRDR feature is negotiated between +client and server for a message, and more than one recipient +has been accepted. + +The ACL test specfied by &%acl_smtp_data_prdr%& happens after a message +has been recieved, and is executed for each recipient of the message. +The test may accept or deny for inividual recipients. +The &%acl_smtp_data%& will still be called after this ACL and +can reject the message overall, even if this ACL has accepted it +for some or all recipients. + +PRDR may be used to support per-user content filtering. Without it +one must defer any recipient after the first that has a different +content-filter configuration. With PRDR, the RCPT-time check +for this can be disabled when the MAIL-time $smtp_command included +"PRDR". Any required difference in behaviour of the main DATA-time +ACL should however depend on the PRDR-time ACL having run, as Exim +will avoid doing so in some situations (eg. single-recipient mails). + +See also the &%prdr_enable%& global option +and the &%hosts_try_prdr%& smtp transport option. + +This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&. +If the ACL is not defined, processing completes as if +the feature was not requested by the client. + .section "The QUIT ACL" "SECTQUITACL" .cindex "QUIT, ACL for" The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL @@ -27074,9 +27636,23 @@ the message is ultimately accepted. For details, see section &<>&). -.endlist +.vitem &*udpsend*&&~=&~<&'parameters'&> +This modifier sends a UDP packet, for purposes such as statistics +collection or behaviour monitoring. The parameters are expanded, and +the result of the expansion must be a colon-separated list consisting +of a destination server, port number, and the packet contents. The +server can be specified as a host name or IPv4 or IPv6 address. The +separator can be changed with the usual angle bracket syntax. For +example, you might want to collect information on which hosts connect +when: +.code +udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ + $tod_zulu $sender_host_address +.endd +.endlist + @@ -27136,7 +27712,6 @@ Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. -.new .vitem &*control&~=&~cutthrough_delivery*& .cindex "&ACL;" "cutthrough routing" .cindex "cutthrough" "requesting" @@ -27144,7 +27719,17 @@ This option requests delivery be attempted while the item is being received. It is usable in the RCPT ACL and valid only for single-recipient mails forwarded from one SMTP connection to another. If a recipient-verify callout connection is requested in the same ACL it is held open and used for the data, otherwise one is made -after the ACL completes. Note that routers are used in verify mode. +after the ACL completes. + +Note that routers are used in verify mode, +and cannot depend on content of received headers. +Note also that headers cannot be +modified by any of the post-data ACLs (DATA, MIME and DKIM). +Headers may be modified by routers (subject to the above) and transports. + +Cutthrough delivery is not supported via transport-filters or when DKIM signing +of outgoing messages is done, because it sends data to the ultimate destination +before the entire message has been received from the source. Should the ultimate destination system positively accept or reject the mail, a corresponding indication is given to the source system and nothing is queued. @@ -27155,10 +27740,8 @@ line. Delivery in this mode avoids the generation of a bounce mail to a (possibly faked) sender when the destination system is doing content-scan based rejection. -.wen -.new .vitem &*control&~=&~debug/*&<&'options'&> .cindex "&ACL;" "enabling debug logging" .cindex "debugging" "enabling from an ACL" @@ -27175,19 +27758,15 @@ contexts): control = debug/opts=+expand+acl control = debug/tag=.$message_exim_id/opts=+expand .endd -.wen -.new .vitem &*control&~=&~dkim_disable_verify*& .cindex "disable DKIM verify" .cindex "DKIM" "disable verify" This control turns off DKIM verification processing entirely. For details on the operation and configuration of DKIM, see chapter &<>&. -.wen -.new .vitem &*control&~=&~dscp/*&<&'value'&> .cindex "&ACL;" "setting DSCP value" .cindex "DSCP" "inbound" @@ -27203,7 +27782,6 @@ 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*& &&& @@ -27405,12 +27983,15 @@ 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 @@ -27504,12 +28085,15 @@ 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 @@ -27564,7 +28148,6 @@ in a system filter or in a router or transport. - .section "ACL conditions" "SECTaclconditions" .cindex "&ACL;" "conditions; list of" Some of the conditions listed in this section are available only when Exim is @@ -27831,6 +28414,23 @@ 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" @@ -28442,6 +29042,13 @@ 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" @@ -28823,6 +29430,7 @@ 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 @@ -29489,7 +30097,9 @@ If you do not set &%av_scanner%&, it defaults to av_scanner = sophie:/var/run/sophie .endd If the value of &%av_scanner%& starts with a dollar character, it is expanded -before use. The following scanner types are supported in this release: +before use. +The usual list-parsing of the content (see &<>&) applies. +The following scanner types are supported in this release: .vlist .vitem &%aveserver%& @@ -29515,6 +30125,7 @@ number, and a port, separated by space, as in the second of these examples: av_scanner = clamd:/opt/clamd/socket av_scanner = clamd:192.0.2.3 1234 av_scanner = clamd:192.0.2.3 1234:local +av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234 .endd If the value of av_scanner points to a UNIX socket file or contains the local keyword, then the ClamAV interface will pass a filename containing the data @@ -29523,6 +30134,22 @@ more efficient. Normally in the TCP case, the data is streamed to ClamAV as 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. + +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 +socket cannot be mixed in with TCP targets. If one of the servers becomes +unavailable, Exim will try the remaining one(s) until it finds one that works. +When a clamd server becomes unreachable, Exim will log a message. Exim does +not keep track of scanner state between multiple messages, and the scanner +selection is random, so the message will get logged in the mainlog for each +email that the down scanner gets chosen first (message wrapped to be readable): +.code +2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition: + clamd: connection to localhost, port 3310 failed + (Connection refused) +.endd + If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for contributing the code for this scanner. @@ -29607,6 +30234,24 @@ 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. @@ -31729,7 +32374,7 @@ they do not affect the values of the variables that refer to header lines. the transport cannot refer to the modified header lines, because such expansions all occur before the message is actually transported. -For both routers and transports, the result of expanding a &%headers_add%& +For both routers and transports, the argument of a &%headers_add%& option must be in the form of one or more RFC 2822 header lines, separated by newlines (coded as &"\n"&). For example: .code @@ -31739,10 +32384,10 @@ headers_add = X-added-header: added by $primary_hostname\n\ Exim does not check the syntax of these added header lines. 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. +specified; the values will append to a single list of header lines. +Each header-line is separately expanded. -The result of expanding &%headers_remove%& must consist of a colon-separated +The argument of a &%headers_remove%& option must consist of a colon-separated list of header names. This is confusing, because header names themselves are often terminated by colons. In this case, the colons are the list separators, not part of the names. For example: @@ -31751,11 +32396,12 @@ headers_remove = return-receipt-to:acknowledge-to .endd Multiple &%headers_remove%& options for a single router or transport can be -specified; the values will be concatenated (with a separating colon -added) before expansion. +specified; the arguments will append to a single header-names list. +Each item is separately expanded. -When &%headers_add%& or &%headers_remove%& is specified on a router, its value -is expanded at routing time, and then associated with all addresses that are +When &%headers_add%& or &%headers_remove%& is specified on a router, +items are expanded at routing time, +and then associated with all addresses that are accepted by that router, and also with any new addresses that it generates. If an address passes through several routers as a result of aliasing or forwarding, the changes are cumulative. @@ -33853,6 +34499,7 @@ 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 @@ -34162,7 +34809,8 @@ 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. @@ -34391,20 +35039,28 @@ This utility is a Perl script contributed by Matt Hubbard. It runs .code exim -bpu .endd -to obtain a queue listing with undelivered recipients only, and then greps the -output to select messages that match given criteria. The following selection -options are available: +or (in case &*-a*& switch is specified) +.code +exim -bp +.endd +.new +The &*-C*& option is used to specify an alternate &_exim.conf_& which might +contain alternate exim configuration the queue management might be using. +.wen + +to obtain a queue listing, and then greps the output to select messages +that match given criteria. The following selection options are available: .vlist .vitem &*-f*&&~<&'regex'&> -Match the sender address. The field that is tested is enclosed in angle -brackets, so you can test for bounce messages with +Match the sender address using a case-insensitive search. The field that is +tested is enclosed in angle brackets, so you can test for bounce messages with .code exiqgrep -f '^<>$' .endd .vitem &*-r*&&~<&'regex'&> -Match a recipient address. The field that is tested is not enclosed in angle -brackets. +Match a recipient address using a case-insensitve search. The field that is +tested is not enclosed in angle brackets. .vitem &*-s*&&~<&'regex'&> Match against the size field. @@ -34440,6 +35096,9 @@ Brief format &-- one line per message. .vitem &*-R*& Display messages in reverse order. + +.vitem &*-a*& +Include delivered recipients in queue listing. .endlist There is one more option, &%-h%&, which outputs a list of options. @@ -35629,6 +36288,8 @@ are given in chapter &<>&. .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 @@ -35643,7 +36304,7 @@ has &%use_shell%& enabled. .next A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&, &%forbid_filter_dlfunc%& and so forth which restrict facilities available to -&_.forward_ files in a redirect router. If Exim is running on a central mail +&_.forward_& files in a redirect router. If Exim is running on a central mail hub to which ordinary users do not have shell access, but home directories are NFS mounted (for instance) then administrators should review the list of these forbid options available, and should bear in mind that the options that may @@ -35672,6 +36333,39 @@ Consider the use of the &%inlisti%& expansion condition instead. + +.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 &%${quote_%&<&'lookup-type'&>&%:...}%& expansion +items to ensure that data is correctly constructed. +.next +Some lookups might return multiple results, even though normal usage is only +expected to yield one result. +.endlist + + + + .section "IPv4 source routing" "SECID272" .cindex "source routing" "in IP packets" .cindex "IP source routing" @@ -36144,7 +36838,9 @@ disabled by setting DISABLE_DKIM=yes in Local/Makefile. Exim's DKIM implementation allows to .olist Sign outgoing messages: This function is implemented in the SMTP transport. -It can co-exist with all other Exim features, including transport filters. +It can co-exist with all other Exim features +(including transport filters) +except cutthrough delivery. .next Verify signatures in incoming messages: This is implemented by an additional ACL (acl_smtp_dkim), which can be called several times per message, with @@ -36235,6 +36931,10 @@ used. Verification of DKIM signatures in incoming email is implemented via the &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each syntactically(!) correct signature in the incoming message. +A missing ACL definition defaults to accept. +If any ACL call does not acccept, the message is not accepted. +If a cutthrough delivery was in progress for the message it is +summarily dropped (having wasted the transmission effort). To evaluate the signature in the ACL a large number of expansion variables containing the signature status and its details are set up during the @@ -36349,7 +37049,7 @@ integer size comparisons against this value. A colon-separated list of names of headers included in the signature. .vitem &%$dkim_key_testing%& "1" if the key record has the "testing" flag set, "0" if not. -.vitem &%$nosubdomains%& +.vitem &%$dkim_key_nosubdomains%& "1" if the key record forbids subdomaining, "0" otherwise. .vitem &%$dkim_key_srvtype%& Service type (tag s=) from the key record. Defaults to "*" if not specified