${hexquote: expansion operator

[users/heiko/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index c3994a79cb194f6dbaaac270875440f4dc1e646c..800ef5ec16f038dd6b90b03ec69de5106710f50f 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -746,6 +746,7 @@ the Exim documentation, &"spool"& is always used in the first sense.
 .cindex "incorporated code"
 .cindex "regular expressions" "library"
 .cindex "PCRE"
 .cindex "incorporated code"
 .cindex "regular expressions" "library"
 .cindex "PCRE"

+.cindex "OpenDMARC"

 A number of pieces of external code are included in the Exim distribution.
 
 .ilist
 A number of pieces of external code are included in the Exim distribution.
 
 .ilist


@@ -870,6 +871,14 @@ ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 SOFTWARE.
 .endblockquote
 
 SOFTWARE.
 .endblockquote
 

+.next
+.cindex "opendmarc" "acknowledgment"
+The DMARC implementation uses the OpenDMARC library which is Copyrighted by
+The Trusted Domain Project. Portions of Exim source which use OpenDMARC
+derived code are indicated in the respective source files. The full OpenDMARC
+license is provided in the LICENSE.opendmarc file contained in the distributed
+source code.
+

 .next
 Many people have contributed code fragments, some large, some small, that were
 not covered by any specific licence requirements. It is assumed that the
 .next
 Many people have contributed code fragments, some large, some small, that were
 not covered by any specific licence requirements. It is assumed that the


@@ -4335,7 +4344,7 @@ For compatibility with Sendmail, this option is equivalent to
 It sets the incoming protocol and host name (for trusted callers). The
 host name and its colon can be omitted when only the protocol is to be set.
 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
 It sets the incoming protocol and host name (for trusted callers). The
 host name and its colon can be omitted when only the protocol is to be set.
 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer

-to embedded Perl. It is therefore impossible to set a protocol value of &`p`&
+to embedded Perl. It is therefore impossible to set a protocol value of &`d`&

 or &`s`& using this option (but that does not seem a real limitation).
 
 .vitem &%-q%&
 or &`s`& using this option (but that does not seem a real limitation).
 
 .vitem &%-q%&


@@ -21712,11 +21721,14 @@ inserted in the argument list at that point &'as a separate argument'&. This
 avoids any problems with spaces or shell metacharacters, and is of use when a
 &(pipe)& transport is handling groups of addresses in a batch.
 
 avoids any problems with spaces or shell metacharacters, and is of use when a
 &(pipe)& transport is handling groups of addresses in a batch.
 

-If &(force_command)& is enabled on the transport, Special handling takes place
+If &%force_command%& is enabled on the transport, Special handling takes place

 for an argument that consists of precisely the text &`$address_pipe`&.  It
 for an argument that consists of precisely the text &`$address_pipe`&.  It

-is handled much like &`$pipe_addresses`& above.  It is expanded and each
+is handled similarly to &$pipe_addresses$& above.  It is expanded and each

 argument is inserted in the argument list at that point
 argument is inserted in the argument list at that point

-&'as a separate argument'&.
+&'as a separate argument'&.  The &`$address_pipe`& item does not need to be
+the only item in the argument; in fact, if it were then &%force_command%&
+should behave as a no-op.  Rather, it should be used to adjust the command
+run while preserving the argument vector separation.

 
 After splitting up into arguments and expansion, the resulting command is run
 in a subprocess directly from the transport, &'not'& under a shell. The
 
 After splitting up into arguments and expansion, the resulting command is run
 in a subprocess directly from the transport, &'not'& under a shell. The


@@ -21883,6 +21895,10 @@ command = /usr/bin/remote_exec myhost -- $address_pipe
 force_command
 .endd
 
 force_command
 .endd
 

+Note that &$address_pipe$& is handled specially in &%command%& when
+&%force_command%& is set, expanding out to the original argument vector as
+separate items, similarly to a Unix shell &`"$@"`& construct.
+

 .option ignore_status pipe boolean false
 If this option is true, the status returned by the subprocess that is set up to
 run the command is ignored, and Exim behaves as if zero had been returned.
 .option ignore_status pipe boolean false
 If this option is true, the status returned by the subprocess that is set up to
 run the command is ignored, and Exim behaves as if zero had been returned.


@@ -28828,6 +28844,9 @@ following SMTP commands are sent:
 LHLO is used instead of HELO if the transport's &%protocol%& option is
 set to &"lmtp"&.
 
 LHLO is used instead of HELO if the transport's &%protocol%& option is
 set to &"lmtp"&.
 

+The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
+settings.
+

 A recipient callout check is similar. By default, it also uses an empty address
 for the sender. This default is chosen because most hosts do not make use of
 the sender address when verifying a recipient. Using the same address means
 A recipient callout check is similar. By default, it also uses an empty address
 for the sender. This default is chosen because most hosts do not make use of
 the sender address when verifying a recipient. Using the same address means


@@ -35609,6 +35628,50 @@ are given in chapter &<<CHAPappendfile>>&.
 
 
 
 
 
 

+.section "Running local commands" "SECTsecconslocalcmds"
+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
+run commands. Configuration to check includes, but is not limited to:
+
+.ilist
+Use of &%use_shell%& in the pipe transport: various forms of shell command
+injection may be possible with this option present. It is dangerous and should
+be used only with considerable caution. Consider constraints which whitelist
+allowed characters in a variable which is to be used in a pipe transport that
+has &%use_shell%& enabled.
+.next
+A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
+&%forbid_filter_dlfunc%& and so forth which restrict facilities available to
+&_.forward_& files in a redirect router. If Exim is running on a central mail
+hub to which ordinary users do not have shell access, but home directories are
+NFS mounted (for instance) then administrators should review the list of these
+forbid options available, and should bear in mind that the options that may
+need forbidding can change as new features are added between releases.
+.next
+The &%${run...}%& expansion item does not use a shell by default, but
+administrators can configure use of &_/bin/sh_& as part of the command.
+Such invocations should be viewed with prejudicial suspicion.
+.next
+Administrators who use embedded Perl are advised to explore how Perl's
+taint checking might apply to their usage.
+.next
+Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and
+administrators are well advised to view its use with suspicion, in case (for
+instance) it allows a local-part to contain embedded Exim directives.
+.next
+Use of &%${match_local_part...}%& and friends becomes more dangerous if
+Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
+each can reference arbitrary lists and files, rather than just being a list
+of opaque strings.
+The EXPAND_LISTMATCH_RHS option was added and set false by default because of
+real-world security vulnerabilities caused by its use with untrustworthy data
+injected in, for SQL injection attacks.
+Consider the use of the &%inlisti%& expansion condition instead.
+.endlist
+
+
+

 .section "IPv4 source routing" "SECID272"
 .cindex "source routing" "in IP packets"
 .cindex "IP source routing"
 .section "IPv4 source routing" "SECID272"
 .cindex "source routing" "in IP packets"
 .cindex "IP source routing"