The ReplaceTags Plugin
This SpamAssassin plugin module allows you to create various character-classes and use them in your rules. The basic advantage is that you don't have to write huge rules, which are harder to debug, but can use more readable shortcuts. Another one is that it gets pretty easy to extend rules by only modifying the class. It is also pretty customizeable for individual start/end tags and which tests are parsed.
NOTE: this plugin is included with SpamAssassin 3.1.0 by default.
Code
Add the following to your local.cf file:
loadplugin ReplaceTags /path/to/plugin/ReplaceTags.pm
replace_rules VIAGRA_OBFU CIALIS_OBFU # ... and so on
replace_start <
replace_end >
# Example classes
replace_class A [\@\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xe4\xe3\xe2\xe0\xe1\xe2\xe3\xe4\xe5\xe6]
replace_class G [gk]
replace_class I [il\|\!1y\?\xcc\xcd\xce\xcf\xec\xed\xee\xef]
replace_class R [r3]
replace_class V (?:[vu]|\\\/)
replace_class SP [\s\d\_\-\*\$\%\(\)\,\.\:\;\?\!\}\{\[\]\|\/\?\^\#\~\xa1\\`\'\+]
# Small functional example
body VIAGRA_OBFU /(?!viagra)<V>+<SP>*<I>+<SP>*<A>+<SP>*<G>+<SP>*<R>+<SP>*<A>+/i
describe VIAGRA_OBFU obfuscated match "viagra"
score VIAGRA_OBFU 3
body VIAGRA /viagra/i
describe VIAGRA match plain "viagra"
score VIAGRA 1.5
ReplaceTags.pm
=head1 NAME
ReplaceTags - Create character-classes for SpamAssassin-rules
A character-class may contain of any character which is valid in a regular expression.
The grouped characters are easy to maintain and the rules are more readable.
=head1 SYNOPSIS
loadplugin ReplaceTags /path/to/plugin/ReplaceTags.pm
replace_rules VIAGRA_OBFU CIALIS_OBFU
replace_start <
replace_end >
replace_class A [\@\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xe4\xe3\xe2\xe0\xe1\xe2\xe3\xe4\xe5\xe6]
replace_class G [gk]
replace_class I [il\|\!1y\?\xcc\xcd\xce\xcf\xec\xed\xee\xef]
replace_class R [r3]
replace_class V [v\\\/wu]
replace_class SP [\s\d\_\-\*\$\%\(\)\,\.\:\;\?\!\}\{\[\]\|\/\?\^\#\~\xa1\<B4>\`\'\+]
body VIAGRA_OBFU /(?!viagra)<V>+<SP>*<I>+<SP>*<A>+<SP>*<G>+<SP>*<R>+<SP>*<A>+/i
describe VIAGRA_OBFU obfuscated match "viagra"
score VIAGRA_OBFU 3
body VIAGRA /viagra/i
describe VIAGRA match plain "viagra"
score VIAGRA 1.5
This example displays how this plugin can be used to match obfuscated and "normal" phrases, which makes it easier
to increase the scores for rules matching only obfuscated patterns on a real world example.
=head1 CONFIGURATION
=over 4
=item replace_rules list_of_tests
Specify a list of symbolic test names (seperated with whitespaces) of tests which should be parsed. The test will only be parsed if it is a body, heade
r, uri, full or raw test.
=item replace_start sign
=item replace_end sign
Character(s) which indicate the start and end of a class inside a rule. If the class is not enclosed by this
signs it won't be found nor replaced. If you encounter problems run spamassassin from the commandline with
the -D flag and check the output. The default values are < (for replace_start_sign) and > (for replace_end_sign).
=item replace_class classname expression
Define a character class or a valid regular expression. Valid characters are the same as in any usual regular expression. It is not a good idea to put
quantifiers inside the character class, better use them inside your rule is shown above in the example.
=cut
package ReplaceTags;
use strict;
use Mail::SpamAssassin;
use Mail::SpamAssassin::Plugin;
use Switch;
our @ISA = qw|Mail::SpamAssassin::Plugin|;
sub new {
my ($class, $mailsa) = @_;
$class = ref($class) || $class;
my $self = $class->SUPER::new($mailsa);
bless ($self, $class);
return $self;
}
sub check_start {
# This is the point where the rulesets get replaced with our stuff
my ($self,$pms) = @_;
my $start_tag = $self->{replace_start};
my $end_tag = $self->{replace_end};
# Put the names of the rules, which get replaced in a hash, for easier usage
my %Rules;
for my $rule_name (@{$self->{rules_to_replace}}) {
$Rules{$rule_name} = 1;
}
for my $rule_set (qw|body_tests rawbody_tests head_tests full_tests uri_tests|) {
# TODO check what that 0 is for (I guess 0 are the GLOBAL tests and user-tests will
# have a number (uid?)...guess is wrong :( )
while (my ($rule_name, $rule_content) = each %{$pms->{permsgstatus}->{conf}->{$rule_set}->{0}}) {
# If rulename doesn't match, skip
next unless $Rules{$rule_name};
dbg("ReplaceTags: parse rule $rule_name");
my %SkippedTags; # Check-Container to prevent endless loops
# If a tag isn't found for max 4 times the while-loops stops
# this seems to be a _really_ bad idea... This can also occur
# if somebody has content inside his classes which contains the
# start- and end-tag unquoted, but without a valid tag-name. In that
# case this loop, would run for a while...
while ($pms->{permsgstatus}->{conf}->{$rule_set}->{0}->{$rule_name} =~ /$start_tag(.+?)$end_tag/) {
my $tag_name = $1;
dbg("ReplaceTags: Please quote your start and end-signs in rule $rule_name") and last if $SkippedTags{$tag_name} > 5;
dbg("ReplaceTags: TagName = $tag_name");
# If the tag exists, replace it with the corresponding phrase
if ($tag_name) {
dbg("Davor => $pms->{permsgstatus}->{conf}->{$rule_set}->{0}->{$rule_name}");
$pms->{permsgstatus}->{conf}->{$rule_set}->{0}->{$rule_name} = replace_rule($self,$tag_name,$rule_content,$rule_name);
dbg("Danach => $pms->{permsgstatus}->{conf}->{$rule_set}->{0}->{$rule_name}");
}
else {
dbg("ReplaceTags: unknown tag encountered ($start_tag$tag_name$end_tag) in rule $rule_name");
$SkippedTags{$tag_name}++;
}
} # while ($pms->{permsgstatus}->{conf}->{$rule_set}->{0}->{$rule_name} =~ /$start_tag(.+?)$end_tag/)
} while (my ($rule_name, $rule_content) = each %{$pms->{permsgstatus}->{conf}->{$rule_set}->{0}})
} # for my $test (qw|body_tests rawbody_tests head_tests full_tests uri_tests|)
} # sub check_start
sub replace_rule {
my ($self,$tag_name,$rule_content,$rule_name) = @_;
my $start_tag = $self->{replace_start};
my $end_tag = $self->{replace_end};
my $replacement = $self->{replace_classes}->{$tag_name};
if ($replacement) {
# Do the modifications to the rule and return it
dbg("ReplaceTags: modifying rule $rule_name, replacing $start_tag$tag_name$end_tag with $replacement");
$rule_content =~ s/$start_tag$tag_name$end_tag/$replacement/g;
return $rule_content;
}
else {
dbg("ReplaceTags: No replacement found for rule $rule_name, ($start_tag$tag_name$end_tag)");
}
# It should never ever get here
#dbg("ReplaceTags: Please report this to somebody including the full debug-log.");
}
sub parse_config {
# Used configuration pragmas are
# replace_class
# replace_rules
# replace_start_sign
# replace_end_sign
my ($self, $opts) = @_;
switch ($opts->{key}) {
case 'replace_class'
{
if ($opts->{value} =~ /^(\S+)\s+(.*?)\s*$/) {
my $tag_name = $1;
my $tag_replacement = $2;
dbg("ReplaceTags: parse_config got $tag_name -> $tag_replacement");
$self->{replace_classes}->{$tag_name} = $tag_replacement;
}
}
case 'replace_rules'
{
# The replace_rules configuration-pragma contains a comma separated
# list of all rules, which should get parsed by this module
@{$self->{rules_to_replace}} = split(' ', $opts->{'value'});
}
case 'replace_start'
{
# The replace_start_sign indicates the start of a replacement-tag. If this
# setting is omitted a < is used as default.
if ($opts->{value}) {
dbg("ReplaceTags: setting start sign to '$opts->{value}'");
$self->{replace_start} = $opts->{value};
}
else {
dbg("ReplaceTags: no start sign specified. Fall back to default '<'");
$self->{replace_start} = '<';
}
}
case 'replace_end'
{
# The replace_end_sign indicates the end of a replacement-tag. If this
# setting is omitted a > is used as default.
if ($opts->{value}) {
dbg("ReplaceTags: setting end sign to '$opts->{value}'");
$self->{replace_end} = $opts->{value};
}
else {
dbg("ReplaceTags: no end sign specified. Fall back to default '>'");
$self->{replace_end} = '>';
}
}
}
}
sub dbg { Mail::SpamAssassin::dbg (@_); }
1;
How To Use It
See the pod or the example above.
Example Classes
replace_class A [gra\@\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xe4\xe3\xe2\xe0\xe1\xe2\xe3\xe4\xe5\xe60o]
replace_class B [b8]
replace_class C [kc\xc7\xe7@]
replace_class D [d\xd0]
replace_class E [e3\xc8\xc9\xca\xcb\xe8\xe9\xea\xeb\xa4]
replace_class F [f]
replace_class G [gk]
replace_class H [h]
replace_class I [il\|\!1y\?\xcc\xcd\xce\xcf\xec\xed\xee\xef]
replace_class J [j]
replace_class K [k]
replace_class L [il\|\!1\xa3]
replace_class M [m]
replace_class N [n\xd1\xf1]
replace_class O [go0\xd2\xd3\xd4\xd5\xd6\xd8\xf0\xf2\xf3\xf4\xf5\xf6\xf8]
replace_class P [p\xfek]
replace_class Q [q]
replace_class R [r]
replace_class S [s\xa6\xa7]
replace_class T [t]
replace_class U [uv\xb5\xd9\xda\xdb\xdc\xfc\xfb\xfa\xf9\xfd]
replace_class V [v\\\/]
replace_class W [wv]
replace_class X [x\xd7]
replace_class Y [y\xff\xfd\xa5j]
replace_class Z [zs]
replace_class PIC (jpe*g|gif|png)
replace_class SP [\s\d\_\-\*\$\%\(\)\,\.\:\;\?\!\}\{\[\]\|\/\?\^\#\~\xa1\<B4>\`\'\+]
replace_class CUR [\$\xa5\xa3\xa4\xa2]