PCRE_TABLE(5) File Formats Manual PCRE_TABLE(5)
NAME
pcre_table - format of Postfix PCRE tables
SYNOPSIS
postmap -q "string" pcre:/etc/postfix/filename
postmap -q - pcre:/etc/postfix/filename <inputfile
postmap -hmq - pcre:/etc/postfix/filename <inputfile
postmap -bmq - pcre:/etc/postfix/filename <inputfile
DESCRIPTION
The Postfix mail system uses optional tables for address rewriting, mail
routing, or access control. These tables are usually in dbm or db for-
mat.
Alternatively, lookup tables can be specified in Perl Compatible Regular
Expression form. In this case, each input is compared against a list of
patterns. When a match is found, the corresponding result is returned
and the search is terminated.
To find out what types of lookup tables your Postfix system supports use
the "postconf -m" command.
To test lookup tables, use the "postmap -q" command as described in the
SYNOPSIS above. Use "postmap -hmq - <file" for header_checks(5) pat-
terns, and "postmap -bmq - <file" for body_checks(5) (Postfix 2.6 and
later).
This driver can be built with the pcre2 library (Postfix 3.7 and later),
or with the legacy pcre library (all Postfix versions).
COMPATIBILITY
With Postfix version 2.2 and earlier specify "postmap -fq" to query a
table that contains case sensitive patterns. Patterns are case insensi-
tive by default.
TABLE FORMAT
The general form of a PCRE table is:
/pattern/flags result
When pattern matches the input string, use the corresponding re-
sult value.
!/pattern/flags result
When pattern does not match the input string, use the correspond-
ing result value.
if /pattern/flags
endif If the input string matches /pattern/, then match that input
string against the patterns between if and endif. The if..endif
can nest.
Note: do not prepend whitespace to patterns inside if..endif.
This feature is available in Postfix 2.1 and later.
if !/pattern/flags
endif If the input string does not match /pattern/, then match that in-
put string against the patterns between if and endif. The if..en-
dif can nest.
Note: do not prepend whitespace to patterns inside if..endif.
This feature is available in Postfix 2.1 and later.
blank lines and comments
Empty lines and whitespace-only lines are ignored, as are lines
whose first non-whitespace character is a `#'.
multi-line text
A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
Each pattern is a perl-like regular expression. The expression delimiter
can be any non-alphanumeric character, except whitespace or characters
that have special meaning (traditionally the forward slash is used).
The regular expression can contain whitespace.
By default, matching is case-insensitive, and newlines are not treated
as special characters. The behavior is controlled by flags, which are
toggled by appending one or more of the following characters after the
pattern:
i (default: on)
Toggles the case sensitivity flag. By default, matching is case
insensitive.
m (default: off)
Toggles the pcre MULTILINE flag. When this flag is on, the ^ and
$ metacharacters match immediately after and immediately before a
newline character, respectively, in addition to matching at the
start and end of the subject string.
s (default: on)
Toggles the pcre DOTALL flag. When this flag is on, the .
metacharacter matches the newline character. With Postfix ver-
sions prior to 2.0, the flag is off by default, which is inconve-
nient for multi-line message header matching.
x (default: off)
Toggles the pcre extended flag. When this flag is on, whitespace
characters in the pattern (other than in a character class) are
ignored. To include a whitespace character as part of the pat-
tern, escape it with backslash.
Note: do not use #comment after patterns.
A (default: off)
Toggles the pcre ANCHORED flag. When this flag is on, the pat-
tern is forced to be "anchored", that is, it is constrained to
match only at the start of the string which is being searched
(the "subject string"). This effect can also be achieved by ap-
propriate constructs in the pattern itself.
E (default: off)
Toggles the pcre DOLLAR_ENDONLY flag. When this flag is on, a $
metacharacter in the pattern matches only at the end of the sub-
ject string. Without this flag, a dollar also matches immediately
before the final character if it is a newline character (but not
before any other newline characters). This flag is ignored if the
pcre MULTILINE flag is set.
U (default: off)
Toggles the pcre UNGREEDY flag. When this flag is on, the pat-
tern matching engine inverts the "greediness" of the quantifiers
so that they are not greedy by default, but become greedy if fol-
lowed by "?". This flag can also set by a (?U) modifier within
the pattern.
X (default: off)
Toggles the pcre EXTRA flag. When this flag is on, any backslash
in a pattern that is followed by a letter that has no special
meaning causes an error, thus reserving these combinations for
future expansion.
This feature is not supported with PCRE2.
SEARCH ORDER
Patterns are applied in the order as specified in the table, until a
pattern is found that matches the input string.
Each pattern is applied to the entire input string. Depending on the
application, that string is an entire client hostname, an entire client
IP address, or an entire mail address. Thus, no parent domain or parent
network search is done, and user@domain mail addresses are not broken up
into their user and domain constituent parts, nor is user+foo broken up
into user and foo.
TEXT SUBSTITUTION
Substitution of substrings (text that matches patterns inside "()") from
the matched expression into the result string is requested with $1, $2,
etc.; specify $$ to produce a $ character as output. The macros in the
result string may need to be written as ${n} or $(n) if they aren't fol-
lowed by whitespace. This feature does not support pcre2 substring
names.
Note: since negated patterns (those preceded by !) return a result when
the expression does not match, substitutions are not available for
negated patterns.
INLINE SPECIFICATION
The contents of a table may be specified in the table name (Postfix 3.7
and later). The basic syntax is:
main.cf:
parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } ..
master.cf:
.. -o { parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } .. } ..
Postfix recursively expands any $parametername instances in the above
parameter value, ignores whitespace after '{' and before '}', and writes
each rule as one text line to an in-memory file:
in-memory file:
rule-1
rule-2
..
Postfix parses the result as if it is a file in /etc/postfix.
INLINE SPECIFICATION CAVEATS
• When using $parametername inside an inlined pattern, use \Q$para-
metername\E to disable metacharacters such as '.' in the $parame-
tername expansion. Otherwise, the pattern may have unexpected
matches.
• When an inlined rule must contain $, specify $$ to keep Postfix
from trying to do $name expansion as it evaluates a parameter
value. To check an inline configuration, use the "postconf -x"
option as shown below:
• When a main.cf "parametername = value" setting contains
an inline pcre: table, use the command "postconf -x para-
metername". Verify that there are no "undefined parameter"
warnings, and that the output has the syntax that one
would use in a non-inlined Postfix pcre: file.
• When a master.cf "-o { parametername = value }" override
contains an inline pcre: table, use the command "postconf
-Px '*/*/parametername' ". Verify that there are no "unde-
fined parameter" warnings, and that the output has the
syntax that one would use in a non-inlined Postfix pcre:
file.
EXAMPLE SMTPD ACCESS MAP
# Protect your outgoing majordomo exploders
/^(?!owner-)(.*)-outgoing@(.*)/ 550 Use ${1}@${2} instead
# Bounce friend@whatever, except when whatever is our domain (you would
# be better just bouncing all friend@ mail - this is just an example).
/^(friend@(?!my\.domain$).*)$/ 550 Stick this in your pipe $1
# A multi-line entry. The text is sent as one line.
#
/^noddy@my\.domain$/
550 This user is a funny one. You really don't want to send mail to
them as it only makes their head spin.
EXAMPLE HEADER FILTER MAP
/^Subject: make money fast/ REJECT
/^To: friend@public\.com/ REJECT
EXAMPLE BODY FILTER MAP
# First skip over base 64 encoded text to save CPU cycles.
# Requires PCRE version 3.
~^[[:alnum:]+/]{60,}$~ OK
# Put your own body patterns here.
SEE ALSO
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
regexp_table(5), format of POSIX regular expression tables
README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate
this information.
DATABASE_README, Postfix lookup table overview
AUTHOR(S)
The PCRE table lookup code was originally written by:
Andrew McNamara
andrewm@connect.com.au
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney, NSW, Australia
Adopted and adapted by:
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
PCRE_TABLE(5)
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