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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 16:18:56 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 16:18:56 +0000
commitb7c15c31519dc44c1f691e0466badd556ffe9423 (patch)
treef944572f288bab482a615e09af627d9a2b6727d8 /conf/header_checks
parentInitial commit. (diff)
downloadpostfix-b7c15c31519dc44c1f691e0466badd556ffe9423.tar.xz
postfix-b7c15c31519dc44c1f691e0466badd556ffe9423.zip
Adding upstream version 3.7.10.upstream/3.7.10upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+# HEADER_CHECKS(5) HEADER_CHECKS(5)
+#
+# NAME
+# header_checks - Postfix built-in content inspection
+#
+# SYNOPSIS
+# header_checks = pcre:/etc/postfix/header_checks
+# mime_header_checks = pcre:/etc/postfix/mime_header_checks
+# nested_header_checks = pcre:/etc/postfix/nested_header_checks
+# body_checks = pcre:/etc/postfix/body_checks
+#
+# milter_header_checks = pcre:/etc/postfix/milter_header_checks
+#
+# smtp_header_checks = pcre:/etc/postfix/smtp_header_checks
+# smtp_mime_header_checks = pcre:/etc/postfix/smtp_mime_header_checks
+# smtp_nested_header_checks = pcre:/etc/postfix/smtp_nested_header_checks
+# smtp_body_checks = pcre:/etc/postfix/smtp_body_checks
+#
+# postmap -q "string" pcre:/etc/postfix/filename
+# postmap -q - pcre:/etc/postfix/filename <inputfile
+#
+# DESCRIPTION
+# This document describes access control on the content of
+# message headers and message body lines; it is implemented
+# by the Postfix cleanup(8) server before mail is queued.
+# See access(5) for access control on remote SMTP client
+# information.
+#
+# Each message header or message body line is compared
+# against a list of patterns. When a match is found the
+# corresponding action is executed, and the matching process
+# is repeated for the next message header or message body
+# line.
+#
+# Note: message headers are examined one logical header at a
+# time, even when a message header spans multiple lines.
+# Body lines are always examined one line at a time.
+#
+# For examples, see the EXAMPLES section at the end of this
+# manual page.
+#
+# Postfix header or body_checks are designed to stop a flood
+# of mail from worms or viruses; they do not decode attach-
+# ments, and they do not unzip archives. See the documents
+# referenced below in the README FILES section if you need
+# more sophisticated content analysis.
+#
+# FILTERS WHILE RECEIVING MAIL
+# Postfix implements the following four built-in content
+# inspection classes while receiving mail:
+#
+# header_checks (default: empty)
+# These are applied to initial message headers
+# (except for the headers that are processed with
+# mime_header_checks).
+#
+# mime_header_checks (default: $header_checks)
+# These are applied to MIME related message headers
+# only.
+#
+# This feature is available in Postfix 2.0 and later.
+#
+# nested_header_checks (default: $header_checks)
+# These are applied to message headers of attached
+# email messages (except for the headers that are
+# processed with mime_header_checks).
+#
+# This feature is available in Postfix 2.0 and later.
+#
+# body_checks
+# These are applied to all other content, including
+# multi-part message boundaries.
+#
+# With Postfix versions before 2.0, all content after
+# the initial message headers is treated as body con-
+# tent.
+#
+# FILTERS AFTER RECEIVING MAIL
+# Postfix supports a subset of the built-in content inspec-
+# tion classes after the message is received:
+#
+# milter_header_checks (default: empty)
+# These are applied to headers that are added with
+# Milter applications.
+#
+# This feature is available in Postfix 2.7 and later.
+#
+# FILTERS WHILE DELIVERING MAIL
+# Postfix supports all four content inspection classes while
+# delivering mail via SMTP.
+#
+# smtp_header_checks (default: empty)
+#
+# smtp_mime_header_checks (default: empty)
+#
+# smtp_nested_header_checks (default: empty)
+#
+# smtp_body_checks (default: empty)
+# These features are available in Postfix 2.5 and
+# later.
+#
+# COMPATIBILITY
+# With Postfix version 2.2 and earlier specify "postmap -fq"
+# to query a table that contains case sensitive patterns. By
+# default, regexp: and pcre: patterns are case insensitive.
+#
+# TABLE FORMAT
+# This document assumes that header and body_checks rules
+# are specified in the form of Postfix regular expression
+# lookup tables. Usually the best performance is obtained
+# with pcre (Perl Compatible Regular Expression) tables. The
+# regexp (POSIX regular expressions) tables are usually
+# slower, but more widely available. Use the command "post-
+# conf -m" to find out what lookup table types your Postfix
+# system supports.
+#
+# The general format of Postfix regular expression tables is
+# given below. For a discussion of specific pattern or
+# flags syntax, see pcre_table(5) or regexp_table(5),
+# respectively.
+#
+# /pattern/flags action
+# When /pattern/ matches the input string, execute
+# the corresponding action. See below for a list of
+# possible actions.
+#
+# !/pattern/flags action
+# When /pattern/ does not match the input string,
+# execute the corresponding action.
+#
+# 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.
+#
+# if !/pattern/flags
+#
+# endif If the input string does not match /pattern/, then
+# match that input string against the patterns
+# between if and endif. The if..endif can nest.
+#
+# 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 pattern/action line starts with non-whitespace
+# text. A line that starts with whitespace continues
+# a logical line.
+#
+# TABLE SEARCH ORDER
+# For each line of message input, the patterns are applied
+# in the order as specified in the table. When a pattern is
+# found that matches the input line, the corresponding
+# action is executed and then the next input line is
+# inspected.
+#
+# TEXT SUBSTITUTION
+# Substitution of substrings from the matched expression
+# into the action string is possible using the conventional
+# Perl syntax ($1, $2, etc.). The macros in the result
+# string may need to be written as ${n} or $(n) if they
+# aren't followed by whitespace.
+#
+# Note: since negated patterns (those preceded by !) return
+# a result when the expression does not match, substitutions
+# are not available for negated patterns.
+#
+# ACTIONS
+# Action names are case insensitive. They are shown in upper
+# case for consistency with other Postfix documentation.
+#
+# BCC user@domain
+# Add the specified address as a BCC recipient, and
+# inspect the next input line. The address must have
+# a local part and domain part. The number of BCC
+# addresses that can be added is limited only by the
+# amount of available storage space.
+#
+# Note 1: the BCC address is added as if it was spec-
+# ified with NOTIFY=NONE. The sender will not be
+# notified when the BCC address is undeliverable, as
+# long as all down-stream software implements RFC
+# 3461.
+#
+# Note 2: this ignores duplicate addresses (with the
+# same delivery status notification options).
+#
+# This feature is available in Postfix 3.0 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# DISCARD optional text...
+# Claim successful delivery and silently discard the
+# message. Do not inspect the remainder of the input
+# message. Log the optional text if specified, oth-
+# erwise log a generic message.
+#
+# Note: this action disables further header or
+# body_checks inspection of the current message and
+# affects all recipients. To discard only one recip-
+# ient without discarding the entire message, use the
+# transport(5) table to direct mail to the discard(8)
+# service.
+#
+# This feature is available in Postfix 2.0 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# DUNNO Pretend that the input line did not match any pat-
+# tern, and inspect the next input line. This action
+# can be used to shorten the table search.
+#
+# For backwards compatibility reasons, Postfix also
+# accepts OK but it is (and always has been) treated
+# as DUNNO.
+#
+# This feature is available in Postfix 2.1 and later.
+#
+# FILTER transport:destination
+# Override the content_filter parameter setting, and
+# inspect the next input line. After the message is
+# queued, send the entire message through the speci-
+# fied external content filter. The transport name
+# specifies the first field of a mail delivery agent
+# definition in master.cf; the syntax of the next-hop
+# destination is described in the manual page of the
+# corresponding delivery agent. More information
+# about external content filters is in the Postfix
+# FILTER_README file.
+#
+# Note 1: do not use $number regular expression sub-
+# stitutions for transport or destination unless you
+# know that the information has a trusted origin.
+#
+# Note 2: this action overrides the main.cf con-
+# tent_filter setting, and affects all recipients of
+# the message. In the case that multiple FILTER
+# actions fire, only the last one is executed.
+#
+# Note 3: the purpose of the FILTER command is to
+# override message routing. To override the recipi-
+# ent's transport but not the next-hop destination,
+# specify an empty filter destination (Postfix 2.7
+# and later), or specify a transport:destination that
+# delivers through a different Postfix instance
+# (Postfix 2.6 and earlier). Other options are using
+# the recipient-dependent transport_maps or the sen-
+# der-dependent sender_dependent_default_transport-
+# _maps features.
+#
+# This feature is available in Postfix 2.0 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# HOLD optional text...
+# Arrange for the message to be placed on the hold
+# queue, and inspect the next input line. The mes-
+# sage remains on hold until someone either deletes
+# it or releases it for delivery. Log the optional
+# text if specified, otherwise log a generic message.
+#
+# Mail that is placed on hold can be examined with
+# the postcat(1) command, and can be destroyed or
+# released with the postsuper(1) command.
+#
+# Note: use "postsuper -r" to release mail that was
+# kept on hold for a significant fraction of $maxi-
+# mal_queue_lifetime or $bounce_queue_lifetime, or
+# longer. Use "postsuper -H" only for mail that will
+# not expire within a few delivery attempts.
+#
+# Note: this action affects all recipients of the
+# message.
+#
+# This feature is available in Postfix 2.0 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# IGNORE Delete the current line from the input, and inspect
+# the next input line. See STRIP for an alternative
+# that logs the action.
+#
+# INFO optional text...
+# Log an "info:" record with the optional text... (or
+# log a generic text), and inspect the next input
+# line. This action is useful for routine logging or
+# for debugging.
+#
+# This feature is available in Postfix 2.8 and later.
+#
+# PASS optional text...
+# Log a "pass:" record with the optional text... (or
+# log a generic text), and turn off header, body, and
+# Milter inspection for the remainder of this mes-
+# sage.
+#
+# Note: this feature relies on trust in information
+# that is easy to forge.
+#
+# This feature is available in Postfix 3.2 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# PREPEND text...
+# Prepend one line with the specified text, and
+# inspect the next input line.
+#
+# Notes:
+#
+# o The prepended text is output on a separate
+# line, immediately before the input that
+# triggered the PREPEND action.
+#
+# o The prepended text is not considered part of
+# the input stream: it is not subject to
+# header/body checks or address rewriting, and
+# it does not affect the way that Postfix adds
+# missing message headers.
+#
+# o When prepending text before a message header
+# line, the prepended text must begin with a
+# valid message header label.
+#
+# o This action cannot be used to prepend
+# multi-line text.
+#
+# This feature is available in Postfix 2.1 and later.
+#
+# This feature is not supported with mil-
+# ter_header_checks.
+#
+# REDIRECT user@domain
+# Write a message redirection request to the queue
+# file, and inspect the next input line. After the
+# message is queued, it will be sent to the specified
+# address instead of the intended recipient(s).
+#
+# Note: this action overrides the FILTER action, and
+# affects all recipients of the message. If multiple
+# REDIRECT actions fire, only the last one is exe-
+# cuted.
+#
+# This feature is available in Postfix 2.1 and later.
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# REPLACE text...
+# Replace the current line with the specified text,
+# and inspect the next input line.
+#
+# This feature is available in Postfix 2.2 and later.
+# The description below applies to Postfix 2.2.2 and
+# later.
+#
+# Notes:
+#
+# o When replacing a message header line, the
+# replacement text must begin with a valid
+# header label.
+#
+# o The replaced text remains part of the input
+# stream. Unlike the result from the PREPEND
+# action, a replaced message header may be
+# subject to address rewriting and may affect
+# the way that Postfix adds missing message
+# headers.
+#
+# REJECT optional text...
+# Reject the entire message. Do not inspect the
+# remainder of the input message. Reply with
+# optional text... when the optional text is speci-
+# fied, otherwise reply with a generic error message.
+#
+# Note: this action disables further header or
+# body_checks inspection of the current message and
+# affects all recipients.
+#
+# Postfix version 2.3 and later support enhanced sta-
+# tus codes. When no code is specified at the begin-
+# ning of optional text..., Postfix inserts a default
+# enhanced status code of "5.7.1".
+#
+# This feature is not supported with smtp header/body
+# checks.
+#
+# STRIP optional text...
+# Log a "strip:" record with the optional text... (or
+# log a generic text), delete the input line from the
+# input, and inspect the next input line. See IGNORE
+# for a silent alternative.
+#
+# This feature is available in Postfix 3.2 and later.
+#
+# WARN optional text...
+# Log a "warning:" record with the optional text...
+# (or log a generic text), and inspect the next input
+# line. This action is useful for debugging and for
+# testing a pattern before applying more drastic
+# actions.
+#
+# BUGS
+# Empty lines never match, because some map types mis-behave
+# when given a zero-length search string. This limitation
+# may be removed for regular expression tables in a future
+# release.
+#
+# Many people overlook the main limitations of header and
+# body_checks rules.
+#
+# o These rules operate on one logical message header
+# or one body line at a time. A decision made for one
+# line is not carried over to the next line.
+#
+# o If text in the message body is encoded (RFC 2045)
+# then the rules need to be specified for the encoded
+# form.
+#
+# o Likewise, when message headers are encoded (RFC
+# 2047) then the rules need to be specified for the
+# encoded form.
+#
+# Message headers added by the cleanup(8) daemon itself are
+# excluded from inspection. Examples of such message headers
+# are From:, To:, Message-ID:, Date:.
+#
+# Message headers deleted by the cleanup(8) daemon will be
+# examined before they are deleted. Examples are: Bcc:, Con-
+# tent-Length:, Return-Path:.
+#
+# CONFIGURATION PARAMETERS
+# body_checks
+# Lookup tables with content filter rules for message
+# body lines. These filters see one physical line at
+# a time, in chunks of at most $line_length_limit
+# bytes.
+#
+# body_checks_size_limit
+# The amount of content per message body segment
+# (attachment) that is subjected to $body_checks fil-
+# tering.
+#
+# header_checks
+#
+# mime_header_checks (default: $header_checks)
+#
+# nested_header_checks (default: $header_checks)
+# Lookup tables with content filter rules for message
+# header lines: respectively, these are applied to
+# the initial message headers (not including MIME
+# headers), to the MIME headers anywhere in the mes-
+# sage, and to the initial headers of attached mes-
+# sages.
+#
+# Note: these filters see one logical message header
+# at a time, even when a message header spans multi-
+# ple lines. Message headers that are longer than
+# $header_size_limit characters are truncated.
+#
+# disable_mime_input_processing
+# While receiving mail, give no special treatment to
+# MIME related message headers; all text after the
+# initial message headers is considered to be part of
+# the message body. This means that header_checks is
+# applied to all the initial message headers, and
+# that body_checks is applied to the remainder of the
+# message.
+#
+# Note: when used in this manner, body_checks will
+# process a multi-line message header one line at a
+# time.
+#
+# EXAMPLES
+# Header pattern to block attachments with bad file name
+# extensions. For convenience, the PCRE /x flag is speci-
+# fied, so that there is no need to collapse the pattern
+# into a single line of text. The purpose of the
+# [[:xdigit:]] sub-expressions is to recognize Windows CLSID
+# strings.
+#
+# /etc/postfix/main.cf:
+# header_checks = pcre:/etc/postfix/header_checks.pcre
+#
+# /etc/postfix/header_checks.pcre:
+# /^Content-(Disposition|Type).*name\s*=\s*"?([^;]*(\.|=2E)(
+# ade|adp|asp|bas|bat|chm|cmd|com|cpl|crt|dll|exe|
+# hlp|ht[at]|
+# inf|ins|isp|jse?|lnk|md[betw]|ms[cipt]|nws|
+# \{[[:xdigit:]]{8}(?:-[[:xdigit:]]{4}){3}-[[:xdigit:]]{12}\}|
+# ops|pcd|pif|prf|reg|sc[frt]|sh[bsm]|swf|
+# vb[esx]?|vxd|ws[cfh]))(\?=)?"?\s*(;|$)/x
+# REJECT Attachment name "$2" may not end with ".$4"
+#
+# Body pattern to stop a specific HTML browser vulnerability
+# exploit.
+#
+# /etc/postfix/main.cf:
+# body_checks = regexp:/etc/postfix/body_checks
+#
+# /etc/postfix/body_checks:
+# /^<iframe src=(3D)?cid:.* height=(3D)?0 width=(3D)?0>$/
+# REJECT IFRAME vulnerability exploit
+#
+# SEE ALSO
+# cleanup(8), canonicalize and enqueue Postfix message
+# pcre_table(5), format of PCRE lookup tables
+# regexp_table(5), format of POSIX regular expression tables
+# postconf(1), Postfix configuration utility
+# postmap(1), Postfix lookup table management
+# postsuper(1), Postfix janitor
+# postcat(1), show Postfix queue file contents
+# RFC 2045, base64 and quoted-printable encoding rules
+# RFC 2047, message header encoding for non-ASCII text
+#
+# README FILES
+# Use "postconf readme_directory" or "postconf html_direc-
+# tory" to locate this information.
+# DATABASE_README, Postfix lookup table overview
+# CONTENT_INSPECTION_README, Postfix content inspection overview
+# BUILTIN_FILTER_README, Postfix built-in content inspection
+# BACKSCATTER_README, blocking returned forged mail
+#
+# LICENSE
+# The Secure Mailer license must be distributed with this
+# software.
+#
+# AUTHOR(S)
+# 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
+#
+# HEADER_CHECKS(5)