settings can be obtained by using &%routers%&, &%transports%&, or
&%authenticators%&.
+.cindex "environment"
+If &%environment%& is given as an argument, the set of environment
+variables is output, line by line. Using the &%-n%& flag supresses the value of the
+variables.
+
.cindex "options" "macro &-- extracting"
If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
are available, similarly to the drivers. Because macros are sometimes used
file that exists is used. Failure to open an existing file stops Exim from
proceeding any further along the list, and an error is generated.
+The file names need to be absolute names.
+
When this option is used by a caller other than root, and the list is different
from the compiled-in list, Exim gives up its root privilege immediately, and
runs with the real and effective uid and gid set to those of the caller.
-.section "Expansion of lists" "SECID75"
+.section "Expansion of lists" "SECTlistexpand"
.cindex "expansion" "of lists"
Each list is expanded as a single string before it is used. The result of
expansion must be a list, possibly containing empty items, which is split up
This option defines the ACL that is run when an SMTP VRFY command is
received. See chapter &<<CHAPACL>>& for further details.
+.new
+.option add_environment main "string list" empty
+.cindex "environment" "inherited"
+This option allows to set individual environment variables that the
+currently linked libraries and programs in child processes use. The
+default list is empty,
+.wen
+
.option admin_groups main "string list&!!" unset
.cindex "admin user"
This option is expanded just once, at the start of Exim's processing. If the
.option ignore_fromline_local main boolean false
See &%ignore_fromline_hosts%& above.
+.new
+.option keep_environment main "string list" unset
+.cindex "environment" "inherited"
+This option contains a string list of environment variables to keep.
+You have to trust these variables or you have to be sure that
+these variables do not impose any security risk. Keep in mind that
+during the startup phase Exim is running with an effective UID 0 in most
+installations. As the default value is an empty list, the default
+environment for using libraries, running embedded Perl code, or running
+external binaries is empty, and does not not even contain PATH or HOME.
+
+Actually the list is interpreted as a list of patterns
+(&<<SECTlistexpand>>&), except that it is not expanded first.
+
+WARNING: Macro substitution is still done first, so having a macro
+FOO and having FOO_HOME in your &%keep_environment%& option may have
+unexpected results. You may work around this using a regular expression
+that does not match the macro name: ^[F]OO_HOME$.
+
+Current versions of Exim issue a warning during startupif you do not mention
+&%keep_environment%& or &%add_environment%& in your runtime configuration
+file.
+.wen
+
.option keep_malformed main time 4d
This option specifies the length of time to keep messages whose spool files
&%sender_unqualified_hosts%&, or if the message was submitted locally (not
using TCP/IP), and the &%-bnq%& option was not set.
+.option set_environment main "string list" empty
+.cindex "environment"
+This option allows to set individual environment variables that the
+currently linked libraries and programs in child processes use. The
+default list is empty,
+
.option smtp_accept_keepalive main boolean true
.cindex "keepalive" "on incoming connection"
.new
.section "Running local commands" "SECTsecconslocalcmds"
+.cindex "security" "local commands"
+.cindex "security" "command injection attacks"
There are a number of ways in which an administrator can configure Exim to run
commands based upon received, untrustworthy, data. Further, in some
configurations a user who can control a &_.forward_& file can also arrange to
+
+.new
+.section "Trust in configuration data" "SECTsecconfdata"
+.cindex "security" "data sources"
+.cindex "security" "regular expressions"
+.cindex "regular expressions" "security"
+.cindex "PCRE" "security"
+If configuration data for Exim can come from untrustworthy sources, there
+are some issues to be aware of:
+
+.ilist
+Use of &%${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
+.wen
+
+
+
+
.section "IPv4 source routing" "SECID272"
.cindex "source routing" "in IP packets"
.cindex "IP source routing"
git://git.exim.org / exim.git / blobdiff