1 package Exim::Plugin::CheckDisclaimer;

     2 

     3 # For detailed information see the end of this

     4 # file.

     5 # Source: https://ssl.schlittermann.de/hg/exim-check-message-conformance

     6 # (c) 2015 Heiko Schlittermann

     7 

     8 use Fcntl qw/:seek/;

     9 use base 'Exporter';

    10 our @EXPORT  = qw(check_disclaimer);

    11 our $Verbose = 0;

    12 my $pattern;

    13 

    14 # Lets search for the disclaimer.

    15 # Usage: ${perl{check_disclaimer}{<disclaimer>}}

    16 #        ${perl{check_disclaimer}{<disclaimer>}{<file>}}

    17 #

    18 # The content of the <disclaimer> file is used as a regexp to be found

    19 # near the end of the <file>. If <file> is not specified, we use the

    20 # default file location:

    21 # $spool_directory/scan/$message_exim_id/$message_exim_id.eml

    22 

    23 sub check_disclaimer {

    24     my $pattern_file = shift;

    25     my $file = shift // Exim::expand_string(

    26         '$spool_directory/scan/$message_exim_id/$message_exim_id.eml');

    27 

    28     if (not defined $pattern) {

    29         open(my $fh, $pattern_file) or die "Can't open $pattern_file: $!\n";

    30         $_ = join '', <$fh>;

    31         $pattern = qr/$_/;

    32     }

    33 

    34     open(my $fh, $file) or die "Can't open $file: $!\n";

    35     seek($fh, -1024, SEEK_END)

    36       or die "Can't seek to -1024: $!\n"

    37       if -s $fh > 1024;

    38 

    39     $_ = join '', <$fh>;

    40 

    41     if (/$pattern/) {

    42         warn __PACKAGE__

    43           . ": signature pattern from $pattern_file matched in $file\n"

    44           if $Verbose;

    45         return 1;

    46     }

    47 

    48     warn __PACKAGE__

    49       . ": signature pattern from $pattern_file NOT matched in $file\n"

    50       if $Verbose;

    51     return 0;

    52 }

    53 

    54 1;

    55 

    56 __END__

    57 

    58 =head1 NAME

    59 

    60  check_disclaimer - check for an disclaimer pattern

    61 

    62 =head1 SYNOPSIS

    63 

    64  use Exim::Plugin::CheckDisclaimer;

    65  ${perl{check_disclaimer}{/etc/exim4/disclaimer}}

    66  ${perl{check_disclaimer}{/etc/exim4/disclaimer}{$mime_decoded_filename}

    67 

    68 =head1 DESCRIPTION

    69 

    70 This Plugin checks for the existence of a message disclaimer by matching

    71 the ends of the message parts with a pattern from a pattern file. The

    72 B<pattern file> needs to contain a Perl regular expression.

    73 

    74 To use it, add the following line to your Exim configuration:

    75 

    76     perl_startup = 

    77         use lib '/etc/exim4'; \

    78         use Exim::Plugin::CheckDisclaimer; \

    79         $Exim::Plugin::CheckDisclaimer::Verbose = 1

    80 

    81 The disclaimer may be part of the MIME coverletter or 

    82 at the end of the old school message body.

    83 

    84 Now you get a callable `check_disclaimer()` function.

    85 Your MIME ACL needs about the following code:

    86 

    87     acl_check_mime:

    88 

    89       accept condition = $acl_m_sig_found

    90 

    91       warn

    92         condition           = $mime_is_coverletter

    93         !condition          = $mime_is_rfc822

    94         decode              = default

    95         set acl_m_sig_found = ${perl{check_disclaimer}{/etc/exim4/disclaimer}{$mime_decoded_filename}}

    96 

    97     accept

    98 

    99 

   100     acl_check_data:

   101 

   102       warn 

   103         !condition          = $acl_m_sig_found

   104         # temporary workaround to get the mail spooled to the .eml file

   105         # this is NOT necessary if some malware or spam acl condition

   106         # was processed already

   107         regex               = ^

   108         set acl_m_sig_found = \

   109                 ${perl{check_disclaimer}{/etc/exim4/disclaimer}}

   110 

   111       deny !condition = $acl_m_sig_found

   112             message   = no signature/disclaimer found

   113 

   114 =head1 EXAMPLE

   115 

   116 The example signature pattern file might look:

   117 

   118  (?mix)          # multiline, case insensitive, extended

   119  ^--\x20\s+      # dash, dash, space

   120  ^\S+\s\S+\s+    # fist name, last name

   121 

   122 Or simply

   123 

   124   -- 

   125   \S+

   126 

   127 =head1 AUTHOR

   128 

   129 Heiko Schlittermann L<hs@schlittermann.de>

   130 

   131 =cut

   132 

   133 // vim:sts=2 sw=2 aw ai et