.set I " "
.macro copyyear
-2012
+2013
.endmacro
. /////////////////////////////////////////////////////////////////////////////
.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
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
&%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
.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).
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%&"
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%&"
&`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%&"
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"
.vitem &%-G%&
.oindex "&%-G%&"
.cindex "submission fixups, suppressing (command-line)"
-.new
This option is equivalent to an ACL applying:
.code
control = suppress_local_fixups
As this affects audit information, the caller must be a trusted user to use
this option.
-.wen
.vitem &%-h%&&~<&'number'&>
.oindex "&%-h%&"
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"
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%&"
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
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"
address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
processing lists.
+To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
+a strict interpretation of header line formatting. Exim parses the bare,
+unquoted portion of an email address and if it finds a comma, treats it as an
+email address seperator. For the example header line:
+.code
+From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
+.endd
+The first example below demonstrates that Q-encoded email addresses are parsed
+properly if it is given the raw header (in this example, &`$rheader_from:`&).
+It does not see the comma because it's still encoded as "=2C". The second
+example below is passed the contents of &`$header_from:`&, meaning it gets
+de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
+The third example shows that the presence of a comma is skipped when it is
+quoted.
+.code
+# exim -be '${addresses:From: \
+=?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
+user@example.com
+# exim -be '${addresses:From: Last, First <user@example.com>}'
+Last:user@example.com
+# exim -be '${addresses:From: "Last, First" <user@example.com>}'
+user@example.com
+.endd
.vitem &*${base62:*&<&'digits'&>&*}*&
.cindex "&%base62%& expansion item"
This operator converts non-printable characters in a string into a hex
escape form. Byte values between 33 (!) and 126 (~) inclusive are left
as is, and other byte values are converted to &`\xNN`&, for example a
-byt value 127 is converted to &`\x7f`&.
+byte value 127 is converted to &`\x7f`&.
.vitem &*${lc:*&<&'string'&>&*}*&
The string is interpreted as a list and the number of items is returned.
-.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${list_*&<&'type'&>&*name*&>&*}*&
+.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
.cindex "expansion" "named list"
.cindex "&%listnamed%& expansion item"
The name is interpreted as a named list and the content of the list is returned,
expanding any referenced lists, re-quoting as needed for colon-separation.
-If the optional type if given it must be one of "a", "d", "h" or "l"
+If the optional type is given it must be one of "a", "d", "h" or "l"
and selects address-, domain-, host- or localpart- lists to search among respectively.
Otherwise all types are searched in an undefined order and the first
matching list is returned.
the ACL's as well.
-
.vitem &$authenticated_sender$&
.cindex "sender" "authenticated"
.cindex "authentication" "sender"
received. It is empty if there was no successful authentication. See also
&$authenticated_id$&.
-.new
.vitem &$sender_host_dnssec$&
.vindex "&$sender_host_dnssec$&"
If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or
If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
mechanism in the list, then this variable will be false.
-.wen
.vitem &$sender_host_name$&
.section "TLS" "SECID108"
.table2
.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
-.row &%gnutls_enable_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
+.row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
.row &%openssl_options%& "adjust OpenSSL compatibility options"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
.row &%tls_certificate%& "location of server certificate"
.code
delay_warning = 2h:12h:99d
.endd
+Note that the option is only evaluated at the time a delivery attempt fails,
+which depends on retry and queue-runner configuration.
+Typically retries will be configured more frequently than warning messages.
.option delay_warning_condition main string&!! "see below"
.vindex "&$domain$&"
See &%dns_retrans%& above.
-.new
.option dns_use_dnssec main integer -1
.cindex "DNS" "resolver options"
.cindex "DNS" "DNSSEC"
default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
If the resolver library does not support DNSSEC then this option has no effect.
-.wen
.option dns_use_edns0 main integer -1
implementations of TLS.
-.new
-option gnutls_enable_pkcs11 main boolean unset
+option gnutls_allow_auto_pkcs11 main boolean unset
This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
See
&url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
for documentation.
-.wen
&`tls_rollback_bug`&
.endlist
-.new
As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
all clients connecting using the MacOS SecureTransport TLS facility prior
to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
to negotiate TLS then this option value might help, provided that your OpenSSL
release is new enough to contain this work-around. This may be a situation
where you have to upgrade OpenSSL to get buggy clients working.
-.wen
.option oracle_servers main "string list" unset
.endd
is interpreted as a pipe with a rather strange command name, and no arguments.
-.new
Note that the above example assumes that the text comes from a lookup source
of some sort, so that the quotes are part of the data. If composing a
redirect router with a &%data%& option directly specifying this command, the
data itself, or avoid using this mechanism and instead create a custom
transport with the &%command%& option set and reference that transport from
an &%accept%& router.
-.wen
.next
.cindex "file" "in redirection list"
The variables &$transport_name$& and &$router_name$& contain the name of the
transport and the router that called it.
-
.option delivery_date_add transports boolean false
.cindex "&'Delivery-date:'& header line"
If this option is true, a &'Delivery-date:'& header is added to the message.
for a transport; all listed headers are added.
-
.option headers_only transports boolean false
.cindex "transport" "header lines only"
.cindex "message" "transporting headers only"
details.
-.new
.option dscp smtp string&!! unset
.cindex "DCSP" "outbound"
This option causes the DSCP value associated with a socket to be set to one
that these values will have any effect, not be stripped by networking
equipment, or do much of anything without cooperation with your Network
Engineer and those of all network operators between the source and destination.
-.wen
.option fallback_hosts smtp "string list" unset
be the name of a file that contains a CRL in PEM format.
-.new
.option tls_dh_min_bits smtp integer 1024
.cindex "TLS" "Diffie-Hellman minimum acceptable size"
When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
will fail.
Only supported when using GnuTLS.
-.wen
.option tls_privatekey smtp string&!! unset
expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
generic &%server_set_id%& option is expanded and saved in &$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.
The &%tls_require_ciphers%& options operate differently, as described in the
sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
.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
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"
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).
-
.section "Use of the control modifier" "SECTcontrols"
.cindex "&%control%& ACL modifier"
The &%control%& modifier supports the following settings:
is what is wanted for subsequent tests.
-.new
.vitem &*control&~=&~cutthrough_delivery*&
.cindex "&ACL;" "cutthrough routing"
.cindex "cutthrough" "requesting"
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.
Should the ultimate destination system positively accept or reject the mail,
a corresponding indication is given to the source system and nothing is queued.
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"
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 &<<CHAPdkim>>&.
-.wen
-.new
.vitem &*control&~=&~dscp/*&<&'value'&>
.cindex "&ACL;" "setting DSCP value"
.cindex "DSCP" "inbound"
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*& &&&
-
.section "ACL conditions" "SECTaclconditions"
.cindex "&ACL;" "conditions; list of"
Some of the conditions listed in this section are available only when Exim is
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 &<<SECTlistconstruct>>&) applies.
+The following scanner types are supported in this release:
.vlist
.vitem &%aveserver%&
av_scanner = clamd:/opt/clamd/socket
av_scanner = clamd:192.0.2.3 1234
av_scanner = clamd:192.0.2.3 1234:local
+av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
.endd
If the value of av_scanner points to a UNIX socket file or contains the local
keyword, then the ClamAV interface will pass a filename containing the data
Exim does not assume that there is a common filesystem with the remote host.
There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
you be running a version of ClamAV prior to 0.95.
+
+The final example shows that multiple TCP targets can be specified. Exim will
+randomly use one for each incoming email (i.e. it load balances them). Note
+that only TCP targets may be used if specifying a list of scanners; a UNIX
+socket cannot be mixed in with TCP targets. If one of the servers becomes
+unavailable, Exim will try the remaining one(s) until it finds one that works.
+When a clamd server becomes unreachable, Exim will log a message. Exim does
+not keep track of scanner state between multiple messages, and the scanner
+selection is random, so the message will get logged in the mainlog for each
+email that the down scanner gets chosen first (message wrapped to be readable):
+.code
+2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
+ clamd: connection to localhost, port 3310 failed
+ (Connection refused)
+.endd
+
If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
contributing the code for this scanner.
.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
+
+.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"
projects / exim.git / blobdiff