X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/b10e4ec2bc7b74e062939d573cf9e93a9a939890..6e62c454f618d77c69bea88c01e71765a1320dce:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 2598bc89e..1ba0a10dd 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2012 +2013 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -539,7 +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 @@ -553,7 +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 @@ -1376,8 +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 @@ -1387,7 +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). @@ -2709,14 +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%&" @@ -2977,7 +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%&" @@ -3003,7 +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%&" @@ -3118,11 +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" @@ -3727,7 +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 @@ -3738,7 +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%&" @@ -3756,7 +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" @@ -3767,7 +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%&" @@ -4631,12 +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 @@ -7051,6 +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" @@ -9180,6 +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 @@ -9836,7 +9875,7 @@ be useful for processing the output of the MD5 and SHA-1 hashing functions. 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 -byt value 127 is converted to &`\x7f`&. +byte value 127 is converted to &`\x7f`&. .vitem &*${lc:*&<&'string'&>&*}*& @@ -9872,12 +9911,12 @@ when &%length%& is used as an operator. The string is interpreted as a list and the number of items is returned. -.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${list_*&<&'type'&>&*name*&>&*}*& +.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*& .cindex "expansion" "named list" .cindex "&%listnamed%& expansion item" The name is interpreted as a named list and the content of the list is returned, expanding any referenced lists, re-quoting as needed for colon-separation. -If the optional type if given it must be one of "a", "d", "h" or "l" +If the optional type is given it must be one of "a", "d", "h" or "l" and selects address-, domain-, host- or localpart- lists to search among respectively. Otherwise all types are searched in an undefined order and the first matching list is returned. @@ -10946,7 +10985,6 @@ authentication, which means this variable could also be visible in all of the ACL's as well. - .vitem &$authenticated_sender$& .cindex "sender" "authenticated" .cindex "authentication" "sender" @@ -11930,7 +11968,6 @@ driver that successfully authenticated the client from which the message was received. It is empty if there was no successful authentication. See also &$authenticated_id$&. -.new .vitem &$sender_host_dnssec$& .vindex "&$sender_host_dnssec$&" If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or @@ -11952,7 +11989,6 @@ with DNSSEC, only the reverse DNS. If you have changed &%host_lookup_order%& so that &`bydns`& is not the first mechanism in the list, then this variable will be false. -.wen .vitem &$sender_host_name$& @@ -13007,7 +13043,7 @@ listed in more than one group. .section "TLS" "SECID108" .table2 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode" -.row &%gnutls_enable_pkcs11%& "allow GnuTLS to autoload PKCS11 modules" +.row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules" .row &%openssl_options%& "adjust OpenSSL compatibility options" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .row &%tls_certificate%& "location of server certificate" @@ -13654,6 +13690,9 @@ a very large time at the end of the list. For example: .code delay_warning = 2h:12h:99d .endd +Note that the option is only evaluated at the time a delivery attempt fails, +which depends on retry and queue-runner configuration. +Typically retries will be configured more frequently than warning messages. .option delay_warning_condition main string&!! "see below" .vindex "&$domain$&" @@ -13805,7 +13844,6 @@ to set in them. See &%dns_retrans%& above. -.new .option dns_use_dnssec main integer -1 .cindex "DNS" "resolver options" .cindex "DNS" "DNSSEC" @@ -13814,7 +13852,6 @@ 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 @@ -14042,15 +14079,13 @@ 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.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs) for documentation. -.wen @@ -14821,14 +14856,12 @@ 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 @@ -18769,7 +18802,6 @@ 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 @@ -18779,7 +18811,6 @@ 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" @@ -19724,7 +19755,6 @@ one. The variables &$transport_name$& and &$router_name$& contain the name of the transport and the router that called it. - .option delivery_date_add transports boolean false .cindex "&'Delivery-date:'& header line" If this option is true, a &'Delivery-date:'& header is added to the message. @@ -19772,7 +19802,6 @@ Unlike most options, &%headers_add%& can be specified multiple times for a transport; all listed headers are added. - .option headers_only transports boolean false .cindex "transport" "header lines only" .cindex "message" "transporting headers only" @@ -22502,7 +22531,6 @@ See the &%search_parents%& option in chapter &<>& for more details. -.new .option dscp smtp string&!! unset .cindex "DCSP" "outbound" This option causes the DSCP value associated with a socket to be set to one @@ -22516,7 +22544,6 @@ The outbound packets from Exim will be marked with this value in the header that these values will have any effect, not be stripped by networking equipment, or do much of anything without cooperation with your Network Engineer and those of all network operators between the source and destination. -.wen .option fallback_hosts smtp "string list" unset @@ -22922,7 +22949,6 @@ This option specifies a certificate revocation list. The expanded value must be the name of a file that contains a CRL in PEM format. -.new .option tls_dh_min_bits smtp integer 1024 .cindex "TLS" "Diffie-Hellman minimum acceptable size" When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman @@ -22932,7 +22958,6 @@ If the parameter offered by the server is too small, then the TLS handshake will fail. Only supported when using GnuTLS. -.wen .option tls_privatekey smtp string&!! unset @@ -24616,8 +24641,7 @@ to be returned. If the result of a successful expansion is an empty string, expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&. For any other result, a temporary error code is returned, with the expanded -string as the error text, and the failed id saved in -&$authenticated_fail_id$&. +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. @@ -25493,12 +25517,10 @@ 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 @@ -26088,6 +26110,12 @@ 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" @@ -26324,7 +26352,6 @@ your resources. The &%acl_smtp_data%& ACL is run after both 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 enabled (which is the default). @@ -27201,7 +27228,6 @@ udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ - .section "Use of the control modifier" "SECTcontrols" .cindex "&%control%& ACL modifier" The &%control%& modifier supports the following settings: @@ -27258,7 +27284,6 @@ 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" @@ -27266,7 +27291,13 @@ 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. Note also that headers cannot be +modified by any of the post-data ACLs (DATA, MIME and DKIM). +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. @@ -27277,10 +27308,8 @@ 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" @@ -27297,19 +27326,15 @@ 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" @@ -27325,7 +27350,6 @@ 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*& &&& @@ -27527,12 +27551,15 @@ 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 @@ -27626,12 +27653,15 @@ 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 @@ -27686,7 +27716,6 @@ 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 @@ -29611,7 +29640,9 @@ 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%& @@ -29655,10 +29686,11 @@ 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: +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) +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 @@ -35767,6 +35799,8 @@ 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 @@ -35810,6 +35844,39 @@ 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" @@ -36282,7 +36349,9 @@ 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 @@ -36373,6 +36442,10 @@ 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