From 127c31ad87760bfc8d6a83808ebce0cd3f082de6 Mon Sep 17 00:00:00 2001 From: nigel Date: Wed, 15 Aug 2001 10:08:37 +0000 Subject: [PATCH] built filter from source --- system_filter.exim | 180 ++++++++++++++++++++++++++------------------- 1 file changed, 103 insertions(+), 77 deletions(-) diff --git a/system_filter.exim b/system_filter.exim index f920ac8..4aab7eb 100644 --- a/system_filter.exim +++ b/system_filter.exim @@ -1,11 +1,34 @@ # Exim filter -## Version: 0.13 -# $Id: system_filter.exim,v 1.3 2001/05/18 10:28:13 nigel Exp $ +## Version: 0.14 +# $Id: system_filter.exim,v 1.6 2001/08/15 10:02:33 nigel Exp $ +## Exim system filter to refuse potentially harmful payloads in +## mail messages +## (c) 2000-2001 Nigel Metheringham +## +## This program is free software; you can redistribute it and/or modify +## it under the terms of the GNU General Public License as published by +## the Free Software Foundation; either version 2 of the License, or +## (at your option) any later version. +## +## This program is distributed in the hope that it will be useful, +## but WITHOUT ANY WARRANTY; without even the implied warranty of +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +## GNU General Public License for more details. +## +## You should have received a copy of the GNU General Public License +## along with this program; if not, write to the Free Software +## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA +## -A copy of the GNU General Public License is distributed with exim itself + +## -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ## If you haven't worked with exim filters before, read ## the install notes at the end of this file. +## The install notes are not a replacement for the exim documentation +## -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -# + +## ----------------------------------------------------------------------- # Only run any of this stuff on the first pass through the # filter - this is an optomisation for messages that get # queued and have several delivery attempts @@ -18,7 +41,8 @@ then finish endif -# Check for MS buffer overruns as per latest BUGTRAQ. +## ----------------------------------------------------------------------- +# Check for MS buffer overruns as per BUGTRAQ. # http://www.securityfocus.com/frames/?content=/templates/article.html%3Fid%3D61 # This could happen in error messages, hence its placing # here... @@ -29,21 +53,22 @@ endif if ${length_80:$header_date:} is not $header_date: then fail text "This message has been rejected because it has\n\ - \tan overlength date field which can be used\n\ - \tto subvert Microsoft mail programs\n\ - \tThe following URL has further information\n\ - \thttp://www.securityfocus.com/frames/?content=/templates/article.html%3Fid%3D61" + an overlength date field which can be used\n\ + to subvert Microsoft mail programs\n\ + The following URL has further information\n\ + http://www.securityfocus.com/frames/?content=/templates/article.html%3Fid%3D61" seen finish endif -# This is a nasty compromise. -# This crud is now being sent with a <> envelope sender, but +## ----------------------------------------------------------------------- +# These messages are now being sent with a <> envelope sender, but # blocking all error messages that pattern match prevents -# bounces getting back.... so we fudge it somewhat +# bounces getting back.... so we fudge it somewhat and check for known +# header signatures. Other bounces are allowed through. if $header_from: contains "@sexyfun.net" then fail text "This message has been rejected since it has\n\ - \tthe signature of a known virus in the header." + the signature of a known virus in the header." seen finish endif if error_message and $header_from: contains "Mailer-Daemon@" @@ -52,56 +77,60 @@ then finish endif +## ----------------------------------------------------------------------- # Look for single part MIME messages with suspicious name extensions # Check Content-Type header using quoted filename [content_type_quoted_fn_match] -if $header_content-type: matches "(?:file)?name=(\"[^\"]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|pif)\")" +if $header_content-type: matches "(?:file)?name=(\"[^\"]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|lnk|pif)\")" then fail text "This message has been rejected because it has\n\ - \tpotentially executable content $1\n\ - \tThis form of attachment has been used by\n\ - \trecent viruses or other malware.\n\ - \tIf you meant to send this file then please\n\ - \tpackage it up as a zip file and resend it." + potentially executable content $1\n\ + This form of attachment has been used by\n\ + recent viruses or other malware.\n\ + If you meant to send this file then please\n\ + package it up as a zip file and resend it." seen finish endif # same again using unquoted filename [content_type_unquoted_fn_match] -if $header_content-type: matches "(?:file)?name=([\\\\w.-]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|pif))" +if $header_content-type: matches "(?:file)?name=(.+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|lnk|pif))" then fail text "This message has been rejected because it has\n\ - \tpotentially executable content $1\n\ - \tThis form of attachment has been used by\n\ - \trecent viruses or other malware.\n\ - \tIf you meant to send this file then please\n\ - \tpackage it up as a zip file and resend it." + potentially executable content $1\n\ + This form of attachment has been used by\n\ + recent viruses or other malware.\n\ + If you meant to send this file then please\n\ + package it up as a zip file and resend it." seen finish endif +## ----------------------------------------------------------------------- # Attempt to catch embedded VBS attachments # in emails. These were used as the basis for -# the ILOVEYOU virus and its variants +# the ILOVEYOU virus and its variants - many many varients # Quoted filename - [body_quoted_fn_match] -if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))(\"[^\"]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|pif)\")[\\\\s;]" +if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))(\"[^\"]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|lnk|pif)\")[\\\\s;]" then fail text "This message has been rejected because it has\n\ - \ta potentially executable attachment $1\n\ - \tThis form of attachment has been used by\n\ - \trecent viruses or other malware.\n\ - \tIf you meant to send this file then please\n\ - \tpackage it up as a zip file and resend it." + a potentially executable attachment $1\n\ + This form of attachment has been used by\n\ + recent viruses or other malware.\n\ + If you meant to send this file then please\n\ + package it up as a zip file and resend it." seen finish endif # same again using unquoted filename [body_unquoted_fn_match] -if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))([\\\\w.-]+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|pif))[\\\\s;]" +if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))(.+\\\\.(?:vb[se]|ws[fh]|jse?|exe|com|cmd|shs|hta|bat|scr|lnk|pif))[\\\\s;]" then fail text "This message has been rejected because it has\n\ - \ta potentially executable attachment $1\n\ - \tThis form of attachment has been used by\n\ - \trecent viruses or other malware.\n\ - \tIf you meant to send this file then please\n\ - \tpackage it up as a zip file and resend it." + a potentially executable attachment $1\n\ + This form of attachment has been used by\n\ + recent viruses or other malware.\n\ + If you meant to send this file then please\n\ + package it up as a zip file and resend it." seen finish endif +## ----------------------------------------------------------------------- + #### Version history # @@ -137,6 +166,12 @@ endif # shorter than the limits on pre exim 3.20 filters. This will # make them significantly less efficient, but I am getting so # many queries about this that requiring 3.2x appears unsupportable. +# 0.14 15 August,2001 +# Added .lnk extension - most requested item :-) +# Reformatted everything so its now built from a set of short +# library files, cutting down on manual duplication. +# Changed \w in filename detection to . - dodges locale problems +# Explicit application of GPL after queries on license status # #### Install Notes # @@ -150,7 +185,7 @@ endif # To install, copy the filter file (with appropriate permissions) # to /etc/exim/system_filter.exim and add to your exim config file # [location is installation depedant - typicaly /etc/exim/config ] -# at the top the line:- +# in the first section the line:- # message_filter = /etc/exim/system_filter.exim # message_body_visible = 5000 # @@ -176,45 +211,36 @@ endif # #### BASIS # -# The regexp that is used to pickup MIME/uuencoded parts is replicated -# below (in perl format). You need to remember that exim converts -# newlines to spaces in the message_body variable. -# -# (?:Content- # start of content header -# (?:Type: (?>\s*) # rest of c/t header -# [\w-]+/[\w-]+ # content-type (any) -# |Disposition: (?>\s*) # content-disposition hdr -# attachment) # content-disposition -# ;(?>\s*) # ; space or newline -# (?:file)?name= # filename=/name= -# |begin (?>\s+) [0-7]{3,4} (?>\s+)) # begin octal-mode -# (\"[^\"]+\. # quoted filename. -# (?:vb[se] # list of extns -# |ws[fh] -# |jse? -# |exe -# |com -# |cmd -# |shs -# |hta -# |bat -# |scr -# |pif) -# \" # end quote -# |[\w.-]+\. # unquoted filename.ext -# (?:vb[se] # list of extns -# |ws[fh] -# |jse? -# |exe -# |com -# |cmd -# |shs -# |hta -# |bat -# |scr -# |pif) -# ) # end of filename capture -# [\s;] # trailing ;/space/newline +# The regexp that is used to pickup MIME/uuencoded body parts with +# quoted filenames is replicated below (in perl format). +# You need to remember that exim converts newlines to spaces in +# the message_body variable. +# +# (?:Content- # start of content header +# (?:Type: (?>\s*) # rest of c/t header +# [\w-]+/[\w-]+ # content-type (any) +# |Disposition: (?>\s*) # content-disposition hdr +# attachment) # content-disposition +# ;(?>\s*) # ; space or newline +# (?:file)?name= # filename=/name= +# |begin (?>\s+) [0-7]{3,4} (?>\s+)) # begin octal-mode +# (\"[^\"]+\. # quoted filename. +# (?:vb[se] # list of extns +# |ws[fh] +# |jse? +# |exe +# |com +# |cmd +# |shs +# |hta +# |bat +# |scr +# |lnk +# |pif) +# \" # end quote +# ) # end of filename capture +# [\s;] # trailing ;/space/newline + # # ### [End] -- 2.30.2