X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/6372d4c990f39ba6ad84a91af0a3a61a63bd50a3..6aac3239b4ce9638c2c5647684dc4ff2a6afbb42:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index e5873f349..e48208899 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -392,7 +392,7 @@ very wide interest. An &"easier"& discussion of Exim which provides more in-depth explanatory, introductory, and tutorial material can be found in a book entitled &'The Exim SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge -(&url(http://www.uit.co.uk/exim-book/)). +(&url(https://www.uit.co.uk/exim-book/)). This book also contains a chapter that gives a general introduction to SMTP and Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date @@ -456,7 +456,7 @@ website, are hosted at the University of Cambridge. .cindex "FAQ" As well as Exim distribution tar files, the Exim web site contains a number of differently formatted versions of the documentation. A recent addition to the -online information is the Exim wiki (&url(http://wiki.exim.org)), +online information is the Exim wiki (&url(https://wiki.exim.org)), which contains what used to be a separate FAQ, as well as various other examples, tips, and know-how that have been contributed by Exim users. The wiki site should always redirect to the correct place, which is currently @@ -487,7 +487,7 @@ If you are using a Debian distribution of Exim, you may wish to subscribe to the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'& via this web page: .display -&url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users) +&url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users) .endd Please ask Debian-specific questions on this list and not on the general Exim lists. @@ -509,14 +509,14 @@ message to the &'exim-dev'& mailing list and have it discussed. .cindex "distribution" "https site" The master distribution site for the Exim distribution is .display -&*https://downloads.exim.org/*& +&url(https://downloads.exim.org/) .endd The service is available over HTTPS, HTTP and FTP. We encourage people to migrate to HTTPS. -The content served at &'https://downloads.exim.org/'& is identical to the -content served at &'https://ftp.exim.org/pub/exim'& and -&'ftp://ftp.exim.org/pub/exim'&. +The content served at &url(https://downloads.exim.org/) is identical to the +content served at &url(https://ftp.exim.org/pub/exim) and +&url(ftp://ftp.exim.org/pub/exim). If accessing via a hostname containing &'ftp'&, then the file references that follow are relative to the &_exim_& directories at these sites. @@ -771,7 +771,7 @@ Foundation; either version 2 of the License, or (at your option) any later version. This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information, the spec and sample code for cdb can be obtained from -&url(http://www.pobox.com/~djb/cdb.html). This implementation borrows +&url(https://cr.yp.to/cdb.html). This implementation borrows some code from Dan Bernstein's implementation (which has no license restrictions applied to it). .endblockquote @@ -825,7 +825,7 @@ Redistributions of any form whatsoever must retain the following acknowledgment: &"This product includes software developed by Computing Services -at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."& +at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."& CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY @@ -1364,6 +1364,7 @@ order in which they are tested. The individual configuration options are described in more detail in chapter &<>&. .ilist +.cindex affix "router precondition" The &%local_part_prefix%& and &%local_part_suffix%& options can specify that the local parts handled by the router may or must have certain prefixes and/or suffixes. If a mandatory affix (prefix or suffix) is not present, the router is @@ -1400,6 +1401,7 @@ of domains that it defines. .vindex "&$local_part_prefix$&" .vindex "&$local_part$&" .vindex "&$local_part_suffix$&" +.cindex affix "router precondition" If the &%local_parts%& option is set, the local part of the address must be in the set of local parts that it defines. If &%local_part_prefix%& or &%local_part_suffix%& is in use, the prefix or suffix is removed from the local @@ -1696,7 +1698,7 @@ or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command. If your operating system has no PCRE support then you will need to obtain and build the current PCRE from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/). -More information on PCRE is available at &url(http://www.pcre.org/). +More information on PCRE is available at &url(https://www.pcre.org/). .section "DBM libraries" "SECTdb" .cindex "DBM libraries" "discussion of" @@ -1749,14 +1751,18 @@ the traditional &'ndbm'& interface. .next To complicate things further, there are several very different versions of the Berkeley DB package. Version 1.85 was stable for a very long time, releases -2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now -numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All -versions of Berkeley DB can be obtained from -&url(http://www.sleepycat.com/). +2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&. +Maintenance of some of the earlier releases has ceased. All versions of +Berkeley DB could be obtained from +&url(http://www.sleepycat.com/), which is now a redirect to their new owner's +page with far newer versions listed. +It is probably wise to plan to move your storage configurations away from +Berkeley DB format, as today there are smaller and simpler alternatives more +suited to Exim's usage model. .next .cindex "&'tdb'& DBM library" Yet another DBM library, called &'tdb'&, is available from -&url(http://download.sourceforge.net/tdb). It has its own interface, and also +&url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also operates on a single file. .endlist @@ -1869,7 +1875,7 @@ supports the &[iconv()]& function. However, some of the operating systems that supply &[iconv()]& do not support very many conversions. The GNU &%libiconv%& library (available from -&url(http://www.gnu.org/software/libiconv/)) can be installed on such +&url(https://www.gnu.org/software/libiconv/)) can be installed on such systems to remedy this deficiency, as well as on systems that do not supply &[iconv()]& at all. After installing &%libiconv%&, you should add .code @@ -2896,12 +2902,14 @@ actually being delivered. .vitem &%-bfp%&&~<&'prefix'&> .oindex "&%-bfp%&" +.cindex affix "filter testing" This sets the prefix of the local part of the recipient address when a filter file is being tested by means of the &%-bf%& option. The default is an empty prefix. .vitem &%-bfs%&&~<&'suffix'&> .oindex "&%-bfs%&" +.cindex affix "filter testing" This sets the suffix of the local part of the recipient address when a filter file is being tested by means of the &%-bf%& option. The default is an empty suffix. @@ -2957,7 +2965,7 @@ acceptable or not. See section &<>&. Features such as authentication and encryption, where the client input is not plain text, cannot easily be tested with &%-bh%&. Instead, you should use a specialized SMTP test program such as -&url(http://jetmore.org/john/code/#swaks,swaks). +&url(https://www.jetmore.org/john/code/swaks/,swaks). .vitem &%-bhc%&&~<&'IP&~address'&> .oindex "&%-bhc%&" @@ -3612,7 +3620,8 @@ are: &<>&) &`lookup `& general lookup code and all lookups &`memory `& memory handling -&`pid `& add pid to debug output lines +&`noutf8 `& modifier: avoid UTF-8 line-drawing +&`pid `& modifier: add pid to debug output lines &`process_info `& setting info for the process log &`queue_run `& queue runs &`receive `& general message reception logic @@ -3620,7 +3629,7 @@ are: &`retry `& retry handling &`rewrite `& address rewriting &`route `& address routing -&`timestamp `& add timestamp to debug output lines +&`timestamp `& modifier: add timestamp to debug output lines &`tls `& TLS logic &`transport `& transports &`uid `& changes of uid/gid and looking up uid/gid @@ -3652,6 +3661,15 @@ The &`timestamp`& selector causes the current time to be inserted at the start of all debug output lines. This can be useful when trying to track down delays in processing. +.new +.cindex debugging "UTF-8 in" +.cindex UTF-8 "in debug output" +The &`noutf8`& selector disables the use of +UTF-8 line-drawing characters to group related information. +When disabled. ascii-art is used instead. +Using the &`+all`& option does not set this modifier, +.wen + If the &%debug_print%& option is set in any driver, it produces output whenever any debugging is selected, or if &%-v%& is used. @@ -3966,8 +3984,17 @@ the messages are active, their status is not altered. This option can be used only by an admin user or by the user who originally caused the message to be placed on the queue. +. .new +. .vitem &%-MS%& +. .oindex "&%-MS%&" +. .cindex REQUIRETLS +. This option is used to request REQUIRETLS processing on the message. +. It is used internally by Exim in conjunction with -E when generating +. a bounce message. +. .wen + .vitem &%-Mset%&&~<&'message&~id'&> -.oindex "&%-Mset%& +.oindex "&%-Mset%&" .cindex "testing" "string expansion" .cindex "expansion" "testing" This option is useful only in conjunction with &%-be%& (that is, when testing @@ -5067,6 +5094,7 @@ The following classes of macros are defined: &` _DRIVER_ROUTER_* `& router drivers &` _DRIVER_TRANSPORT_* `& transport drivers &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers +&` _LOG_* `& log_selector values &` _OPT_MAIN_* `& main config options &` _OPT_ROUTERS_* `& generic router options &` _OPT_TRANSPORTS_* `& generic transport options @@ -6325,6 +6353,9 @@ online Perl manpages, in many Perl reference books, and also in Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)). +. --- the http: URL here redirects to another page with the ISBN in the URL +. --- where trying to use https: just redirects back to http:, so sticking +. --- to the old URL for now. 2018-09-07. The documentation for the syntax and semantics of the regular expressions that are supported by PCRE is included in the PCRE distribution, and no further @@ -6491,13 +6522,15 @@ The following single-key lookup types are implemented: string without a terminating binary zero. The cdb format is designed for indexed files that are read frequently and never updated, except by total re-creation. As such, it is particularly suitable for large files containing -aliases or other indexed data referenced by an MTA. Information about cdb can -be found in several places: +aliases or other indexed data referenced by an MTA. Information about cdb and +tools for building the files can be found in several places: .display -&url(http://www.pobox.com/~djb/cdb.html) -&url(ftp://ftp.corpit.ru/pub/tinycdb/) -&url(http://packages.debian.org/stable/utils/freecdb.html) +&url(https://cr.yp.to/cdb.html) +&url(http://www.corpit.ru/mjt/tinycdb.html) +&url(https://packages.debian.org/stable/utils/freecdb) +&url(https://github.com/philpennock/cdbtools) (in Go) .endd +. --- 2018-09-07: corpit.ru http:-only A cdb distribution is not needed in order to build Exim with cdb support, because the code for reading cdb files is included directly in Exim itself. However, no means of building or testing cdb files is provided with Exim, so @@ -6778,6 +6811,7 @@ not likely to be useful in normal operation. .next .cindex "whoson lookup type" .cindex "lookup" "whoson" +. --- still http:-only, 2018-09-07 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that allows a server to check whether a particular (dynamically allocated) IP address is currently allocated to a known (trusted) user and, optionally, to @@ -9350,6 +9384,27 @@ ${extract{Z}{A=... B=...}{$value} fail } This forces an expansion failure (see section &<>&); {<&'string2'&>} must be present for &"fail"& to be recognized. +.new +.vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&& + {*&<&'string3'&>&*}}*&" +.cindex "expansion" "extracting from JSON object" +.cindex JSON expansions +The key and <&'string1'&> are first expanded separately. Leading and trailing +white space is removed from the key (but not from any of the strings). The key +must not be empty and must not consist entirely of digits. +The expanded <&'string1'&> must be of the form: +.display +{ <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... } +.endd +.vindex "&$value$&" +The braces, commas and colons, and the quoting of the member name are required; +the spaces are optional. +Matching of the key against the member names is done case-sensitively. +. XXX should be a UTF-8 compare + +The results of matching are handled as above. +.wen + .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&& {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" @@ -9382,6 +9437,19 @@ yields &"99"&. Two successive separators mean that the field between them is empty (for example, the fifth field above). +.new +.vitem "&*${extract json{*&<&'number'&>&*}}&&& + {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" +.cindex "expansion" "extracting from JSON array" +.cindex JSON expansions +The <&'number'&> argument must consist entirely of decimal digits, +apart from leading and trailing white space, which is ignored. + +Field selection and result handling is as above; +there is no choice of field separator. +.wen + + .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*& .cindex "list" "selecting by condition" .cindex "expansion" "selecting from list by condition" @@ -9434,11 +9502,14 @@ letters appear. For example: &*$h_*&<&'header&~name'&>&*:*&" &&& "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&& &*$bh_*&<&'header&~name'&>&*:*&" &&& + "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&& + &*$lh_*&<&'header&~name'&>&*:*&" "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&& &*$rh_*&<&'header&~name'&>&*:*&" .cindex "expansion" "header insertion" .vindex "&$header_$&" .vindex "&$bheader_$&" +.vindex "&$lheader_$&" .vindex "&$rheader_$&" .cindex "header lines" "in expansion strings" .cindex "header lines" "character sets" @@ -9451,7 +9522,7 @@ The newline that terminates a header line is not included in the expansion, but internal newlines (caused by splitting the header line over several physical lines) may be present. -The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way +The difference between the four pairs of expansions is in the way the data in the header line is interpreted. .ilist @@ -9459,6 +9530,15 @@ the data in the header line is interpreted. &%rheader%& gives the original &"raw"& content of the header line, with no processing at all, and without the removal of leading and trailing white space. +.next +.cindex "list" "of header lines" +&%lheader%& gives a colon-separated list, one element per header when there +are multiple headers with a given name. +Any embedded colon characters within an element are doubled, so normal Exim +list-processing facilities can be used. +The terminating newline of each element is removed; in other respects +the content is &"raw"&. + .next .cindex "base64 encoding" "in header lines" &%bheader%& removes leading and trailing white space, and then decodes base64 @@ -9616,9 +9696,10 @@ some of the braces: .code ${length_:} .endd -The result of this item is either the first <&'n'&> characters or the whole +The result of this item is either the first <&'n'&> bytes or the whole of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with &%strlen%&, which gives the length of a string. +All measurement is done in bytes and is not UTF-8 aware. .vitem "&*${listextract{*&<&'number'&>&*}&&& @@ -9866,15 +9947,26 @@ extend what can be done. Firstly, you can vary the timeout. For example: .code ${readsocket{/socket/name}{request string}{3s}} .endd + The third argument is a list of options, of which the first element is the timeout and must be present if the argument is given. Further elements are options of form &'name=value'&. -One option type is currently recognised, defining whether (the default) +Two option types is currently recognised: shutdown and tls. +The first defines whether (the default) or not a shutdown is done on the connection after sending the request. Example, to not do so (preferred, eg. by some webservers): .code ${readsocket{/socket/name}{request string}{3s:shutdown=no}} .endd +.new +The second, tls, controls the use of TLS on the connection. Example: +.code +${readsocket{/socket/name}{request string}{3s:tls=yes}} +.endd +The default is to not use TLS. +If it is enabled, a shutdown as descripbed above is never done. +.wen + A fourth argument allows you to change any newlines that are in the data that is read, in the same way as for &%readfile%& (see above). This example turns them into spaces: @@ -9940,7 +10032,7 @@ expansion items. .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*& This item inserts &"raw"& header lines. It is described with the &%header%& -expansion item above. +expansion item in section &<>& above. .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&& {*&<&'string2'&>&*}}*&" @@ -10039,6 +10131,8 @@ ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}} yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of the regular expression from string expansion. +The regular expression is compiled in 8-bit mode, working against bytes +rather than any Unicode-aware character handling. .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*& @@ -10095,11 +10189,11 @@ ${substr{3}{2}{$local_part}} If the starting offset is greater than the string length the result is the null string; if the length plus starting offset is greater than the string length, the result is the right-hand part of the string, starting from the -given offset. The first character in the string has offset zero. +given offset. The first byte (character) in the string has offset zero. The &%substr%& expansion item can take negative offset values to count -from the right-hand end of its operand. The last character is offset -1, the -second-last is offset -2, and so on. Thus, for example, +from the right-hand end of its operand. The last byte (character) is offset -1, +the second-last is offset -2, and so on. Thus, for example, .code ${substr{-5}{2}{1234567}} .endd @@ -10116,7 +10210,7 @@ ${substr{-3}{2}{12}} yields &"1"&. When the second number is omitted from &%substr%&, the remainder of the string -is taken if the offset is positive. If it is negative, all characters in the +is taken if the offset is positive. If it is negative, all bytes (characters) in the string preceding the offset point are taken. For example, an offset of -1 and no length, as in these semantically identical examples: .code @@ -10125,13 +10219,15 @@ ${substr{-1}{abcde}} .endd yields all but the last character of the string, that is, &"abcd"&. +All measurement is done in bytes and is not UTF-8 aware. + .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&& {*&<&'replacements'&>&*}}*&" .cindex "expansion" "character translation" .cindex "&%tr%& expansion item" -This item does single-character translation on its subject string. The second +This item does single-character (in bytes) translation on its subject string. The second argument is a list of characters to be translated in the subject string. Each matching character is replaced by the corresponding character from the replacement list. For example @@ -10142,6 +10238,9 @@ yields &`1b3de1`&. If there are duplicates in the second character string, the last occurrence is used. If the third string is shorter than the second, its last character is replicated. However, if it is empty, no translation takes place. + +All character handling is done in bytes and is not UTF-8 aware. + .endlist @@ -10161,6 +10260,8 @@ The string is interpreted as an RFC 2822 address, as it might appear in a header line, and the effective address is extracted from it. If the string does not parse successfully, the result is empty. +The parsing correctly handles SMTPUTF8 Unicode in the string. + .vitem &*${addresses:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2822 address handling" @@ -10204,7 +10305,7 @@ It does not see the comma because it's still encoded as "=2C". The second example below is passed the contents of &`$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. +quoted. The fourth example shows SMTPUTF8 handling. .code # exim -be '${addresses:From: \ =?iso-8859-2?Q?Last=2C_First?= }' @@ -10213,6 +10314,8 @@ user@example.com Last:user@example.com # exim -be '${addresses:From: "Last, First" }' user@example.com +# exim -be '${addresses:フィル <フィリップ@example.jp>}' +フィリップ@example.jp .endd .vitem &*${base32:*&<&'digits'&>&*}*& @@ -10402,7 +10505,7 @@ abbreviation &%h%& can be used when &%hash%& is used as an operator. .cindex "expansion" "hex to base64" .cindex "&%hex2b64%& expansion item" 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. +be useful for processing the output of the various hashing functions. @@ -10444,6 +10547,7 @@ This forces the letters in the string into lower-case, for example: .code ${lc:$local_part} .endd +Case is defined per the system C locale. .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*& .cindex "expansion" "string truncation" @@ -10457,6 +10561,7 @@ ${length{}{}} See the description of the general &%length%& item above for details. Note that &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used when &%length%& is used as an operator. +All measurement is done in bytes and is not UTF-8 aware. .vitem &*${listcount:*&<&'string'&>&*}*& @@ -10484,6 +10589,7 @@ matching list is returned. The string is interpreted as an RFC 2822 address and the local part is extracted from it. If the string does not parse successfully, the result is empty. +The parsing correctly handles SMTPUTF8 Unicode in the string. .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& @@ -10566,6 +10672,10 @@ example, a plus sign would not cause quoting (but it would for &%quote%&). If you are creating a new email address from the contents of &$local_part$& (or any other unknown data), you should always use this operator. +This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data +will likely use the quoting form. +Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&. + .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& .cindex "quoting" "lookup-specific" @@ -10729,6 +10839,7 @@ Now deprecated, a synonym for the &%base64%& expansion operator. .cindex "&%strlen%& expansion item" The item is replace by the length of the expanded string, expressed as a decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&. +All measurement is done in bytes and is not UTF-8 aware. .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*& @@ -10743,6 +10854,7 @@ ${substr{}{}{}} .endd See the description of the general &%substr%& item above for details. The abbreviation &%s%& can be used when &%substr%& is used as an operator. +All measurement is done in bytes and is not UTF-8 aware. .vitem &*${time_eval:*&<&'string'&>&*}*& .cindex "&%time_eval%& expansion item" @@ -10765,6 +10877,7 @@ 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. +Case is defined per the system C locale. .vitem &*${utf8clean:*&<&'string'&>&*}*& .cindex "correction of invalid utf-8 sequences in strings" @@ -10773,6 +10886,20 @@ This forces the letters in the string into upper-case. .cindex "expansion" "utf-8 forcing" .cindex "&%utf8clean%& expansion item" This replaces any invalid utf-8 sequence in the string by the character &`?`&. +.new +In versions of Exim before 4.92, this did not correctly do so for a truncated +final codepoint's encoding, and the character would be silently dropped. +If you must handle detection of this scenario across both sets of Exim behavior, +the complexity will depend upon the task. +For instance, to detect if the first character is multibyte and a 1-byte +extraction can be successfully used as a path component (as is common for +dividing up delivery folders), you might use: +.code +condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}} +.endd +(which will false-positive if the first character of the local part is a +literal question mark). +.wen .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&& "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&& @@ -10995,7 +11122,8 @@ the header name must be terminated by a colon if white space does not follow. .cindex "&%eqi%& expansion condition" The two substrings are first expanded. The condition is true if the two resulting strings are identical. For &%eq%& the comparison includes the case of -letters, whereas for &%eqi%& the comparison is case-independent. +letters, whereas for &%eqi%& the comparison is case-independent, where +case is defined per the system C locale. .vitem &*exists&~{*&<&'file&~name'&>&*}*& .cindex "expansion" "file existence test" @@ -11058,6 +11186,7 @@ The two substrings are first expanded. The condition is true if the first string is lexically greater than or equal to the second string. For &%ge%& the comparison includes the case of letters, whereas for &%gei%& the comparison is case-independent. +Case and collation order are defined per the system C locale. .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -11069,6 +11198,7 @@ The two substrings are first expanded. The condition is true if the first string is lexically greater than the second string. For &%gt%& the comparison includes the case of letters, whereas for &%gti%& the comparison is case-independent. +Case and collation order are defined per the system C locale. .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -11077,6 +11207,7 @@ case-independent. Both strings are expanded; the second string is treated as a list of simple strings; if the first string is a member of the second, then the condition is true. +For the case-independent &%inlisti%& condition, case is defined per the system C locale. These are simpler to use versions of the more powerful &*forany*& condition. Examples, and the &*forany*& equivalents: @@ -11143,6 +11274,7 @@ The two substrings are first expanded. The condition is true if the first string is lexically less than or equal to the second string. For &%le%& the comparison includes the case of letters, whereas for &%lei%& the comparison is case-independent. +Case and collation order are defined per the system C locale. .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -11154,6 +11286,7 @@ The two substrings are first expanded. The condition is true if the first string is lexically less than the second string. For &%lt%& the comparison includes the case of letters, whereas for &%lti%& the comparison is case-independent. +Case and collation order are defined per the system C locale. .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -11180,6 +11313,8 @@ metacharacter, but if there is no circumflex, the expression is not anchored, and it may match anywhere in the subject, not just at the start. If you want the pattern to match at the end of the subject, you must include the &`$`& metacharacter at an appropriate point. +All character handling is done in bytes and is not UTF-8 aware, +but we might change this in a future Exim release. .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion" At the start of an &%if%& expansion the values of the numeric variable @@ -11294,7 +11429,7 @@ matched using &%match_ip%&. .cindex "expansion" "PAM authentication test" .cindex "&%pam%& expansion condition" &'Pluggable Authentication Modules'& -(&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is +(&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is available in the latest releases of Solaris and in some GNU/Linux distributions. The Exim support, which is intended for use in conjunction with the SMTP AUTH command, is available only if Exim is compiled with @@ -11327,11 +11462,7 @@ server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}} In some operating systems, PAM authentication can be done only from a process running as root. Since Exim is running as the Exim user when receiving messages, this means that PAM cannot be used directly in those systems. -A patched version of the &'pam_unix'& module that comes with the -Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/). -The patched module allows one special uid/gid combination, in addition to root, -to authenticate. If you build the patched module to allow the Exim user and -group, PAM can then be used from an Exim authenticator. +. --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*& @@ -11603,7 +11734,7 @@ When a message is submitted locally (that is, not over a TCP connection) 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. -This second case also sets up inforamtion used by the +This second case also sets up information used by the &$authresults$& expansion item. .vitem &$authenticated_fail_id$& @@ -11860,6 +11991,7 @@ This is not strictly an expansion variable. It is expansion syntax for inserting the message header line with the given name. Note that the name must be terminated by colon or white space, because it may contain a wide variety of characters. Note also that braces must &'not'& be used. +See the full description in section &<>& above. .vitem &$headers_added$& .vindex "&$headers_added$&" @@ -12014,6 +12146,7 @@ once. .vindex "&$local_part_prefix$&" .vindex "&$local_part_suffix$&" +.cindex affix variables If a local part prefix or suffix has been recognized, it is not included in the value of &$local_part$& during routing and subsequent delivery. The values of any prefix or suffix are in &$local_part_prefix$& and @@ -12066,6 +12199,7 @@ variable expands to nothing. .vitem &$local_part_prefix$& .vindex "&$local_part_prefix$&" +.cindex affix variables When an address is being routed or delivered, and a specific prefix for the local part was recognized, it is available in this variable, having been removed from &$local_part$&. @@ -13861,6 +13995,7 @@ listed in more than one group. .row &%av_scanner%& "specify virus scanner" .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&& words""&" +.row &%dns_cname_loops%& "follow CNAMEs returned by resolver" .row &%dns_csa_search_limit%& "control CSA parent search depth" .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search" .row &%header_maxsize%& "total size of message header" @@ -14119,7 +14254,7 @@ feel that in today's Internet, this causes more problems than it solves. It now defaults to true. A more detailed analysis of the issues is provided by Dan Bernstein: .display -&url(http://cr.yp.to/smtp/8bitmime.html) +&url(https://cr.yp.to/smtp/8bitmime.html) .endd To log received 8BITMIME status use @@ -14763,6 +14898,19 @@ 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 &<>&. +.new +.option dns_cname_loops main integer 1 +.cindex DNS "CNAME following" +This option controls the following of CNAME chains, needed if the resolver does +not do it internally. +As of 2018 most should, and the default can be left. +If you have an ancient one, a value of 10 is likely needed. + +The default value of one CNAME-follow is needed +thanks to the observed return for an MX request, +given no MX presence but a CNAME to an A, of the CNAME. +.wen + .option dns_dnssec_ok main integer -1 .cindex "DNS" "resolver options" @@ -15082,12 +15230,12 @@ server. This reduces security slightly, but improves interworking with older implementations of TLS. -option gnutls_allow_auto_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) +&url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs) for documentation. @@ -17369,7 +17517,7 @@ The ordering of the two lists must match. .cindex SSMTP .cindex SMTPS This option specifies a list of incoming SSMTP (aka SMTPS) ports that should -operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately +operate the SSMTP (SMTPS) protocol, where a TLS session is immediately set up without waiting for the client to issue a STARTTLS command. For further details, see section &<>&. @@ -18167,6 +18315,7 @@ and &%user%& and the discussion in chapter &<>&. .option local_part_prefix routers&!? "string list" unset +.cindex affix "router precondition" .cindex "router" "prefix for local part" .cindex "prefix" "for local part, used in router" If this option is set, the router is skipped unless the local part starts with @@ -19461,7 +19610,9 @@ be enclosed in quotes if it contains white space. A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is always separately expanded before use. If the expansion fails, the router declines. The result of the expansion must be a colon-separated list of names -and/or IP addresses, optionally also including ports. The format of each item +and/or IP addresses, optionally also including ports. +If the list is written with spaces, it must be protected with quotes. +The format of each item in the list is described in the next section. The list separator can be changed as described in section &<>&. @@ -23950,18 +24101,21 @@ the message. As a result, the overall timeout for a message depends on the size of the message. Its value must not be zero. See also &%final_timeout%&. +.option dkim_canon smtp string&!! unset .option dkim_domain smtp string list&!! unset -.option dkim_selector smtp string&!! unset +.option dkim_hash smtp string&!! sha256 +.option dkim_identity smtp string&!! unset .option dkim_private_key smtp string&!! unset -.option dkim_canon smtp string&!! unset +.option dkim_selector smtp string&!! unset .option dkim_strict smtp string&!! unset .option dkim_sign_headers smtp string&!! "per RFC" -.option dkim_hash smtp string&!! sha256 -.option dkim_identity smtp string&!! unset +.option dkim_timestamps smtp string&!! unset DKIM signing options. For details see section &<>&. .option delay_after_cutoff smtp boolean true +.cindex "final cutoff" "retries, controlling" +.cindex retry "final cutoff" This option controls what happens when all remote IP addresses for a given domain have been inaccessible for so long that they have passed their retry cutoff times. @@ -24420,10 +24574,17 @@ variable that contains an outgoing port. If the value of this option begins with a digit it is taken as a port number; otherwise it is looked up using &[getservbyname()]&. The default value is -normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is -&"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery +normally &"smtp"&, +but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"& +and if &%protocol%& is set to &"smtps"& the default is &"smtps"&. +If the expansion fails, or if a port number cannot be found, delivery is deferred. +.new +Note that at least one Linux distribution has been seen failing +to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals. +.wen + .option protocol smtp string smtp @@ -24440,7 +24601,11 @@ over a pipe to a local process &-- see chapter &<>&. If this option is set to &"smtps"&, the default value for the &%port%& option changes to &"smtps"&, and the transport initiates TLS immediately after connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. -The Internet standards bodies strongly discourage use of this mode. +.new +The Internet standards bodies used to strongly discourage use of this mode, +but as of RFC 8314 it is perferred over STARTTLS for message submission +(as distinct from MTA-MTA communication). +.wen .option retry_include_ip_address smtp boolean&!! true @@ -24669,6 +24834,16 @@ 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. +.new +.option utf8_downconvert smtp integer!! unset +.cindex utf8 "address downconversion" +.cindex i18n "utf8 address downconversion" +If built with internationalization support, +this option controls conversion of UTF-8 in message addresses +to a-label form. +For details see section &<>&. +.wen + @@ -25696,10 +25871,13 @@ For local deliveries, one delivery attempt is always made for any subsequent messages. If this delivery fails, the address fails immediately. The post-cutoff retry time is not used. +.cindex "final cutoff" "retries, controlling" +.cindex retry "final cutoff" If the delivery is remote, there are two possibilities, controlled by the .oindex "&%delay_after_cutoff%&" &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by -default. Until the post-cutoff retry time for one of the IP addresses is +default. Until the post-cutoff retry time for one of the IP addresses, +as set by the &%retry_data_expire%& option, is reached, the failing email address is bounced immediately, without a delivery attempt taking place. After that time, one new delivery attempt is made to those IP addresses that are past their retry times, and if that still fails, @@ -25974,12 +26152,15 @@ output, and Exim carries on processing. .option server_set_id authenticators string&!! unset .vindex "&$authenticated_id$&" +.vindex "&$authenticated_fail_id$&" When an Exim server successfully authenticates a client, this string is expanded using data from the authentication, and preserved for any incoming messages in the variable &$authenticated_id$&. It is also included in the log lines for incoming messages. For example, a user/password authenticator configuration might preserve the user name that was used to authenticate, and refer to it subsequently during delivery of the message. +On a failing authentication the expansion result is instead saved in +the &$authenticated_fail_id$& variable. If expansion fails, the option is ignored. @@ -26631,8 +26812,8 @@ fixed_cram: .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&" .cindex "Cyrus" "SASL library" .cindex "Kerberos" -The code for this authenticator was provided by Matthew Byng-Maddick of A L -Digital Ltd (&url(http://www.aldigital.co.uk)). +The code for this authenticator was provided by Matthew Byng-Maddick while +at A L Digital Ltd. The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL library implementation of the RFC 2222 (&"Simple Authentication and Security @@ -26742,7 +26923,7 @@ authenticator only. There is only one option: .option server_socket dovecot string unset -This option must specify the socket that is the interface to Dovecot +This option must specify the UNIX socket that is the interface to Dovecot authentication. The &%public_name%& option must specify an authentication mechanism that Dovecot is configured to support. You can have several authenticators for different mechanisms. For example: @@ -26792,15 +26973,17 @@ without code changes in Exim. .option server_channelbinding gsasl boolean false +Do not set this true without consulting a cryptographic engineer. + Some authentication mechanisms are able to use external context at both ends of the session to bind the authentication to that context, and fail the authentication process if that context differs. Specifically, some TLS ciphersuites can provide identifying information about the cryptographic context. -This means that certificate identity and verification becomes a non-issue, -as a man-in-the-middle attack will cause the correct client and server to -see different identifiers and authentication will fail. +This should have meant that certificate identity and verification becomes a +non-issue, as a man-in-the-middle attack will cause the correct client and +server to see different identifiers and authentication will fail. This is currently only supported when using the GnuTLS library. This is only usable by mechanisms which support "channel binding"; at time of @@ -26808,7 +26991,11 @@ writing, that's the SCRAM family. This defaults off to ensure smooth upgrade across Exim releases, in case this option causes some clients to start failing. Some future release -of Exim may switch the default to be true. +of Exim might have switched the default to be true. + +However, Channel Binding in TLS has proven to be broken in current versions. +Do not plan to rely upon this feature for security, ever, without consulting +with a subject matter expert (a cryptographic engineer). .option server_hostname gsasl string&!! "see below" @@ -26990,7 +27177,7 @@ The &(spa)& authenticator provides client support for Microsoft's &'Secure Password Authentication'& mechanism, which is also sometimes known as NTLM (NT LanMan). The code for client side of this authenticator was contributed by Marc Prud'hommeaux, and much of it is -taken from the Samba project (&url(http://www.samba.org)). The code for the +taken from the Samba project (&url(https://www.samba.org/)). The code for the server side was subsequently contributed by Tom Kistner. The mechanism works as follows: @@ -27390,7 +27577,10 @@ the size of the generated prime, so it might still be too large. .oindex "&%tls_require_ciphers%&" "OpenSSL" There is a function in the OpenSSL library that can be passed a list of cipher suites before the cipher negotiation takes place. This specifies which ciphers -are acceptable. The list is colon separated and may contain names like +.new +are acceptable for TLS versions prior to 1.3. +.wen +The list is colon separated and may contain names like DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%& directly to this function call. Many systems will install the OpenSSL manual-pages, so you may have @@ -27455,6 +27645,18 @@ This example will prefer ECDSA-authenticated ciphers over RSA ones: tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT .endd +.new +For TLS version 1.3 the control available is less fine-grained +and Exim does not provide access to it at present. +The value of the &%tls_require_ciphers%& option is ignored when +TLS version 1.3 is negotiated. + +As of writing the library default cipher suite list for TLSv1.3 is +.code +TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256 +.endd +.wen + .section "Requiring specific ciphers or other parameters in GnuTLS" &&& "SECTreqciphgnu" @@ -27481,11 +27683,11 @@ 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.gnutls.org/manual/html_node/Priority-Strings.html), +&url(https://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, then the example code -&url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string) +&url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string) on that site can be used to test a given string. For example: @@ -27637,7 +27839,7 @@ session with a client, you must set either &%tls_verify_hosts%& or apply to all TLS connections. For any host that matches one of these options, Exim requests a certificate as part of the setup of the TLS session. The contents of the certificate are verified by comparing it with a list of -expected certificates. +expected trust-anchors or certificates. These may be the system default set (depending on library version), an explicit file or, depending on library version, a directory, identified by @@ -27654,6 +27856,9 @@ openssl x509 -hash -noout -in /cert/file .endd where &_/cert/file_& contains a single certificate. +There is no checking of names of the client against the certificate +Subject Name or Subject Alternate Names. + The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is what happens if the client does not supply a certificate, or if the certificate does not match any of the certificates in the collection named by @@ -27815,6 +28020,11 @@ 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 &%tls_verify_cert_hostnames%& option lists hosts for which additional +checks are made: that the host name (the one in the DNS A record) +is valid for the certificate. +The option defaults to always checking. + 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 @@ -27981,22 +28191,29 @@ connections to new processes if TLS has been used. .section "Certificates and all that" "SECTcerandall" .cindex "certificate" "references to discussion" In order to understand fully how TLS works, you need to know about -certificates, certificate signing, and certificate authorities. This is not the -place to give a tutorial, especially as I do not know very much about it -myself. Some helpful introduction can be found in the FAQ for the SSL addition -to Apache, currently at +certificates, certificate signing, and certificate authorities. +This is a large topic and an introductory guide is unsuitable for the Exim +reference manual, so instead we provide pointers to existing documentation. + +The Apache web-server was for a long time the canonical guide, so their +documentation is a good place to start; their SSL module's Introduction +document is currently at .display -&url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24) +&url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html) .endd -Other parts of the &'modssl'& documentation are also helpful, and have -links to further files. -Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN -0-201-61598-3), contains both introductory and more in-depth descriptions. -Some sample programs taken from the book are available from +and their FAQ is at .display -&url(http://www.rtfm.com/openssl-examples/) +&url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html) .endd +Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN +0-201-61598-3) in 2001, contains both introductory and more in-depth +descriptions. +More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&, +published by Feisty Duck (ISBN 978-1907117046) in 2013 is good. +Ivan is the author of the popular TLS testing tools at +&url(https://www.ssllabs.com/). + .section "Certificate chains" "SECID186" The file named by &%tls_certificate%& may contain more than one @@ -28067,7 +28284,7 @@ signed with that self-signed certificate. For information on creating self-signed CA certificates and using them to sign user certificates, see the &'General implementation overview'& chapter of the Open-source PKI book, available online at -&url(http://ospkibook.sourceforge.net/). +&url(https://sourceforge.net/projects/ospkibook/). .ecindex IIDencsmtp1 .ecindex IIDencsmtp2 @@ -28105,20 +28322,48 @@ Support for client-side operation of DANE can be included at compile time by def in &_Local/Makefile_&. If it has been included, the macro "_HAVE_DANE" will be defined. -The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3). The latter specifies -the End Entity directly, i.e. the certificate involved is that of the server (and should be the sole one transmitted -during the TLS handshake); this is appropriate for a single system, using a self-signed certificate. +The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3). +These are the "Trust Anchor" and "End Entity" variants. +The latter specifies the End Entity directly, i.e. the certificate involved is that of the server +(and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake); +this is appropriate for a single system, using a self-signed certificate. DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public, -well-known one. A private CA at simplest is just a self-signed certificate which is used to sign -cerver certificates, but running one securely does require careful arrangement. If a private CA is used -then either all clients must be primed with it, or (probably simpler) the server TLS handshake must transmit -the entire certificate chain from CA to server-certificate. If a public CA is used then all clients must be primed with it -(losing one advantage of DANE) - but the attack surface is reduced from all public CAs to that single CA. +well-known one. +A private CA at simplest is just a self-signed certificate (with certain +attributes) which is used to sign server certificates, but running one securely +does require careful arrangement. +With DANE-TA, as implemented in Exim and commonly in other MTAs, +the server TLS handshake must transmit the entire certificate chain from CA to server-certificate. DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record, all of which point to a single TLSA record. +DANE-TA and DANE-EE can both be used together. -Another approach which should be seriously considered is to use DANE with a certificate -from a public CA, because of another technology, "MTA-STS", described below. +.new +Our recommendation is to use DANE with a certificate from a public CA, +because this enables a variety of strategies for remote clients to verify +your certificate. +You can then publish information both via DANE and another technology, +"MTA-STS", described below. + +When you use DANE-TA to publish trust anchor information, you ask entities +outside your administrative control to trust the Certificate Authority for +connections to you. +If using a private CA then you should expect others to still apply the +technical criteria they'd use for a public CA to your certificates. +In particular, you should probably try to follow current best practices for CA +operation around hash algorithms and key sizes. +Do not expect other organizations to lower their security expectations just +because a particular profile might be reasonable for your own internal use. + +When this text was last updated, this in practice means to avoid use of SHA-1 +and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger +than 4096, for interoperability); to use keyUsage fields correctly; to use +random serial numbers. +The list of requirements is subject to change as best practices evolve. +If you're not already using a private CA, or it doesn't meet these +requirements, then we encourage you to avoid all these issues and use a public +CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead. +.wen The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2). @@ -28136,6 +28381,16 @@ are workable for 4th-field hashes. For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName). +.new +The Certificate issued by the CA published in the DANE-TA model should be +issued using a strong hash algorithm. +Exim, and importantly various other MTAs sending to you, will not +re-enable hash algorithms which have been disabled by default in TLS +libraries. +This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable +interoperability (and probably the maximum too, in 2018). +.wen + The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the default of requesting OCSP for all hosts is modified iff DANE is in use, to: @@ -28218,8 +28473,8 @@ MTA-STS to let those clients who do use that protocol derive trust information. The MTA-STS design requires a certificate from a public Certificate Authority -which is recognized by clients sending to you. That selection is outside your -control. +which is recognized by clients sending to you. +That selection of which CAs are trusted by others is outside your control. The most interoperable course of action is probably to use &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate @@ -29850,9 +30105,10 @@ warn hosts = +internal_hosts warn message = Remove internal headers remove_header = $acl_c_ihdrs .endd -Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs. -They are removed from the message before processing the DATA and MIME ACLs. -There is no harm in attempting to remove the same header twice nor is removing +Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs. +Matching header lines are removed from the message before processing the DATA and MIME ACLs. +If multiple header lines match, all are removed. +There is no harm in attempting to remove the same header twice nor in removing a non-existent header. Further header lines to be removed may be accumulated during the DATA and MIME ACLs, after which they are removed from the message, if present. In the case of non-SMTP messages, headers to be removed are @@ -30384,6 +30640,10 @@ connection (assuming long-enough TTL). Exim does not share information between multiple incoming connections (but your local name server cache should be active). +There are a number of DNS lists to choose from, some commercial, some free, +or free for small deployments. An overview can be found at +&url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists). + .section "Specifying the IP address for a DNS list lookup" "SECID201" @@ -30405,8 +30665,7 @@ MX hosts or nameservers of an email sender address. For an example, see section .section "DNS lists keyed on domain names" "SECID202" .cindex "DNS list" "keyed by domain name" There are some lists that are keyed on domain names rather than inverted IP -addresses (see for example the &'domain based zones'& link at -&url(http://www.rfc-ignorant.org/)). No reversing of components is used +addresses. No reversing of components is used with these lists. You can change the name that is looked up in a DNS list by listing it after the domain name, introduced by a slash. For example, .code @@ -30740,7 +30999,7 @@ restrictions, to get the TXT record. As a byproduct of this, there is also a check that the IP being tested is indeed on the first list. The first domain is the one that is put in &$dnslist_domain$&. For example: .code -reject message = \ +deny message = \ rejected because $sender_host_address is blacklisted \ at $dnslist_domain\n$dnslist_text dnslists = \ @@ -30758,7 +31017,7 @@ If you are interested in more than one merged list, the same list must be given several times, but because the results of the DNS lookups are cached, the DNS calls themselves are not repeated. For example: .code -reject dnslists = \ +deny dnslists = \ http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \ socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \ misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \ @@ -30969,13 +31228,15 @@ rest of the ACL. The &%leaky%& (default) option means that the client's recorded rate is not updated if it is above the limit. The effect of this is that Exim measures the -client's average rate of successfully sent email, which cannot be greater than -the maximum allowed. If the client is over the limit it may suffer some -counter-measures (as specified in the ACL), but it will still be able to send -email at the configured maximum rate, whatever the rate of its attempts. This +client's average rate of successfully sent email, +.new +up to the given limit. +This is appropriate if the countermeasure when the condition is true +consists of refusing the message, and is generally the better choice if you have clients that retry automatically. -For example, it does not prevent a sender with an over-aggressive retry rate -from getting any email through. +If the action when true is anything more complex then this option is +likely not what is wanted. +.wen The &%strict%& option means that the client's recorded rate is always updated. The effect of this is that Exim measures the client's average rate @@ -31146,6 +31407,15 @@ connection, HELO, or MAIL). The main use of these variables is expected to be to distinguish between rejections of MAIL and rejections of RCPT in callouts. +.new +The above variables may also be set after a &*successful*& +address verification to: + +.ilist +&%random%&: A random local-part callout succeeded +.endlist +.wen + @@ -31911,7 +32181,7 @@ written. The usual &`defer_ok`& option is available. .vitem &%aveserver%& .cindex "virus scanners" "Kaspersky" This is the scanner daemon of Kaspersky Version 5. You can get a trial version -at &url(http://www.kaspersky.com). This scanner type takes one option, +at &url(https://www.kaspersky.com/). This scanner type takes one option, which is the path to the daemon's UNIX socket. The default is shown in this example: .code @@ -31922,7 +32192,7 @@ av_scanner = aveserver:/var/run/aveserver .vitem &%clamd%& .cindex "virus scanners" "clamd" This daemon-type scanner is GPL and free. You can get it at -&url(http://www.clamav.net/). Some older versions of clamd do not seem to +&url(https://www.clamav.net/). Some older versions of clamd do not seem to unpack MIME containers, so it used to be recommended to unpack MIME attachments in the MIME ACL. This is no longer believed to be necessary. @@ -32016,7 +32286,7 @@ av_scanner = cmdline:\ .endd .vitem &%drweb%& .cindex "virus scanners" "DrWeb" -The DrWeb daemon scanner (&url(http://www.sald.com/)) interface +The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface takes one option, either a full path to a UNIX socket, or host and port specifiers separated by white space. @@ -32053,7 +32323,7 @@ If you omit the argument, the default values show above are used. .vitem &%fsecure%& .cindex "virus scanners" "F-Secure" -The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one +The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one argument which is the path to a UNIX socket. For example: .code av_scanner = fsecure:/path/to/.fsav @@ -32074,9 +32344,13 @@ The default path is &_/var/run/AvpCtl_&. .vitem &%mksd%& .cindex "virus scanners" "mksd" -This is a daemon type scanner that is aimed mainly at Polish users, though some -parts of documentation are now available in English. You can get it at -&url(http://linux.mks.com.pl/). The only option for this scanner type is +This was a daemon type scanner that is aimed mainly at Polish users, +though some documentation was available in English. +The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir) +and this appears to be a candidate for removal from Exim, unless +we are informed of other virus scanners which use the same protocol +to integrate. +The only option for this scanner type is the maximum number of processes used simultaneously to scan the attachments, provided that mksd has been run with at least the same number of child processes. For example: @@ -32108,7 +32382,7 @@ specify an empty element to get this. .vitem &%sophie%& .cindex "virus scanners" "Sophos and Sophie" Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses. -You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option +You can get Sophie at &url(http://sophie.sourceforge.net/). The only option for this scanner type is the path to the UNIX socket that Sophie uses for client communication. For example: .code @@ -32212,7 +32486,7 @@ Support is also provided for Rspamd. For more information about installation and configuration of SpamAssassin or Rspamd refer to their respective websites at -&url(http://spamassassin.apache.org) and &url(http://www.rspamd.com) +&url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/) SpamAssassin can be installed with CPAN by running: .code @@ -35401,7 +35675,7 @@ the address, giving a suitable error message. .cindex "VERP" .cindex "Variable Envelope Return Paths" .cindex "envelope sender" -Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &-- +Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &-- are a way of helping mailing list administrators discover which subscription address is the cause of a particular delivery failure. The idea is to encode the original recipient address in the outgoing envelope sender address, so that @@ -36391,8 +36665,9 @@ the following table: &`F `& sender address (on delivery lines) &`H `& host name and IP address &`I `& local interface used -&`K `& CHUNKING extension used &`id `& message id for incoming message +&`K `& CHUNKING extension used +&`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used &`M8S `& 8BITMIME status for incoming message &`P `& on &`<=`& lines: protocol used &` `& on &`=>`& and &`**`& lines: return path @@ -36503,6 +36778,7 @@ selection marked by asterisks: &` queue_time `& time on queue for one recipient &` queue_time_overall `& time on queue for whole message &` pid `& Exim process id +&` pipelining `& PIPELINING use, on <= and => lines &` proxy `& proxy address on <= and => lines &` receive_time `& time taken to receive message &` received_recipients `& recipients on <= lines @@ -36705,6 +36981,16 @@ local port is a random ephemeral port. &%pid%&: The current process id is added to every log line, in square brackets, immediately after the time and date. .next +.new +.cindex log pipelining +.cindex pipelining "logging outgoing" +&%pipelining%&: A field is added to delivery and accept +log lines when the ESMTP PIPELINING extension was used. +The field is a single "L". + +On accept lines, where PIPELINING was offered but not used by the client, +the field has a minus appended. +.next .cindex "log" "queue run" .cindex "queue runner" "logging" &%queue_run%&: The start and end of every queue run are logged. @@ -36968,7 +37254,7 @@ the next chapter. The utilities described here are: Another utility that might be of use to sites with many MTAs is Tom Kistner's &'exilog'&. It provides log visualizations across multiple Exim servers. See -&url(http://duncanthrax.net/exilog/) for details. +&url(https://duncanthrax.net/exilog/) for details. @@ -37236,8 +37522,8 @@ assuming you have used the name &"exim"& for the Exim user. You can run .cindex "&'eximstats'&" A Perl script called &'eximstats'& is provided for extracting statistical information from log files. The output is either plain text, or HTML. -Exim log files are also supported by the &'Lire'& system produced by the -LogReport Foundation &url(http://www.logreport.org). +. --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan +. --- 404 error and everything else points to that. The &'eximstats'& script has been hacked about quite a bit over time. The latest version is the result of some extensive revision by Steve Campbell. A @@ -38524,6 +38810,12 @@ two files contains the final component of its own name as its first line. This is insurance against disk crashes where the directory is lost but the files themselves are recoverable. +.new +The file formats may be changed, or new formats added, at any release. +Spool files are not intended as an interface to other programs +and should not be used as such. +.wen + Some people are tempted into editing -D files in order to modify messages. You need to be extremely careful if you do this; it is not recommended and you are on your own if you do it. Here are some of the pitfalls: @@ -39035,7 +39327,7 @@ tag value. Note that Exim does not check the value. This option sets the canonicalization method used when signing a message. The DKIM RFC currently supports two methods: "simple" and "relaxed". The option defaults to "relaxed" when unset. Note: the current implementation -only supports using the same canonicalization method for both headers and body. +only supports signing with the same canonicalization method for both headers and body. .option dkim_strict smtp string&!! unset This option defines how Exim behaves when signing a message that @@ -39065,26 +39357,44 @@ If a '+' prefix if used, all headers that are present with this name will be signed, and one signature added for a missing header with the name will be appended. +.new +.option dkim_timestamps smtp integer&!! unset +This option controls the inclusion of timestamp information in the signature. +If not set, no such information will be included. +Otherwise, must be an unsigned number giving an offset in seconds from the current time +for the expiry tag +(eg. 1209600 for two weeks); +both creation (t=) and expiry (x=) tags will be included. + +RFC 6376 lists these tags as RECOMMENDED. +.wen + .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY" .cindex "DKIM" "verification" -Verification of DKIM signatures in SMTP incoming email is implemented via the -&%acl_smtp_dkim%& ACL. By default, this ACL is called once for each +.new +Verification of DKIM signatures in SMTP incoming email is done for all +messages for which an ACL control &%dkim_disable_verify%& has not been set. +.cindex authentication "expansion item" +Performing verification sets up information used by the +&$authresults$& expansion item. +.wen + +.new The results of that verification are then made available to the +&%acl_smtp_dkim%& ACL, &new(which can examine and modify them). +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 accept, the message is not accepted. If a cutthrough delivery was in progress for the message, that is summarily dropped (having wasted the transmission effort). -To evaluate the signature in the ACL a large number of expansion variables +To evaluate the &new(verification result) in the ACL +a large number of expansion variables containing the signature status and its details are set up during the runtime of the ACL. -.cindex authentication "expansion item" -Performing verification sets up information used by the -&$authresults$& expansion item. - Calling the ACL only for existing signatures is not sufficient to build more advanced policies. For that reason, the global option &%dkim_verify_signers%&, and a global expansion variable @@ -39159,8 +39469,10 @@ hash-method or key-size: set dkim_verify_reason = hash too weak or key too short .endd -After all the DKIM ACL runs have completed, the value becomes a +So long as a DKIM ACL is defined (it need do no more than accept), +after all the DKIM ACL runs have completed, the value becomes a colon-separated list of the values after each run. +This is maintained for the mime, prdr and data ACLs. .vitem &%$dkim_verify_reason%& A string giving a little bit more detail when &%$dkim_verify_status%& is either @@ -39232,6 +39544,12 @@ strict enforcement should code the check explicitly. The number of signed body bytes. If zero ("0"), the body is unsigned. If no limit was set by the signer, "9999999999999" is returned. This makes sure that this variable always expands to an integer value. +.new +&*Note:*& The presence of the signature tag specifying a signing body length +is one possible route to spoofing of valid DKIM signatures. +A paranoid implementation might wish to regard signature where this variable +shows less than the "no limit" return as being invalid. +.wen .vitem &%$dkim_created%& UNIX timestamp reflecting the date and time when the signature was created. @@ -39325,13 +39643,14 @@ for more information of what they mean. SPF is a mechanism whereby a domain may assert which IP addresses may transmit messages with its domain in the envelope from, documented by RFC 7208. For more information on SPF see &url(http://www.openspf.org). +. --- 2018-09-07: still not https Messages sent by a system not authorised will fail checking of such assertions. This includes retransmissions done by traditional forwarders. SPF verification support is built into Exim if SUPPORT_SPF=yes is set in &_Local/Makefile_&. The support uses the &_libspf2_& library -&url(http://www.libspf2.org/). +&url(https://www.libspf2.org/). There is no Exim involvement in the transmission of messages; publishing certain DNS records is all that is required. @@ -39442,6 +39761,7 @@ SPF, but it is supported by the same framework that enables SPF capability. Refer to &url(http://www.openspf.org/FAQ/Best_guess_record) for a description of what it means. +. --- 2018-09-07: still not https: To access this feature, simply use the spf_guess condition in place of the spf one. For example: @@ -39510,10 +39830,8 @@ that uses &"Proxy Protocol"& to speak to it. To include this support, include &"SUPPORT_PROXY=yes"& in Local/Makefile. -It was built on specifications from: -(&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)). -That URL was revised in May 2014 to version 2 spec: -(&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)). +It was built on the HAProxy specification, found at +&url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt). The purpose of this facility is so that an application load balancer, such as HAProxy, can sit in front of several Exim servers @@ -39719,6 +40037,12 @@ If a value is appended it may be: If mua_wrapper is set, the utf8_downconvert control is initially set to -1. +.new +The smtp transport has an option &%utf8_downconvert%&. +If set it must expand to one of the three values described above, +and it overrides any previously set value. +.wen + There is no explicit support for VRFY and EXPN. Configurations supporting these should inspect @@ -39840,6 +40164,8 @@ with the event type: .display &`dane:fail `& failure reason &`msg:delivery `& smtp confirmation message +&`msg:fail:internal `& failure reason +&`msg:fail:delivery `& smtp error message &`msg:rcpt:host:defer `& error string &`msg:rcpt:defer `& error string &`msg:host:defer `& error string