/usr/share/perl5/JpegTester.pm is in amavisd-new 1:2.7.1-2ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 | package JpegTester;
# Author: Mark Martinec <mark.martinec@ijs.si>, 2004-10;
# The (new)BSD license applies to this package JpegTester;
use strict;
use re 'taint';
use vars qw($buf $buf_l $buf_ofs);
sub makeTwo($) { # ensure at least two characters in $buf, except near eof
my($fh) = @_;
$buf_l>=0 or die "jpeg: Panic, program error1, pos=$buf_ofs";
if ($buf_l<2) {
my($len) = sysread($fh,$buf,2048,$buf_l); # 2k is about the optimum size
defined $len or die "jpeg: Can't read: $!\n";
$buf_l += $len;
}
}
sub takeN($$) { # swallow n characters
my($fh,$n) = @_; my($err) = undef;
for ($buf_l>=2||makeTwo($fh); $n>0; ) {
if ($buf_l<=0) { $err = "Truncated by $n bytes or more"; last }
if ($n >= $buf_l) { $n -= $buf_l; $buf_ofs += $buf_l; $buf = '' }
else { $buf = substr($buf,$n); $buf_ofs += $n; $n = 0 }
$buf_l = length($buf); $buf_l>=2 || makeTwo($fh);
}
$err;
}
sub takeECS($) { # quickly swallow entropy-coded data segment
my($fh) = @_;
for ($buf_l>=2||makeTwo($fh); $buf_l>0; ) {
if ($buf =~ s/^([^\xff]+)//) { $buf_ofs += length($1) }
elsif ($buf =~ s/^(\xff\x00)+//) { $buf_ofs += length($1) }
else { last }
# last unless $buf =~ s/^(?: [^\xff] | \xff \x00 )+//x; # Perl Bus error
$buf_l = length($buf); $buf_l>=2 || makeTwo($fh);
}
}
sub takeFill($) { # swallow fill bytes before marker
my($fh) = @_;
for (makeTwo($fh); $buf_l>0; $buf_l=length($buf),makeTwo($fh)) {
if ($buf =~ s/^ \xff+ (?= \xff )//x) { $buf_ofs += length($1) }
else { last }
}
}
sub takeTail($) { # swallow common junk after EOI
my($fh) = @_;
for (makeTwo($fh); $buf_l>0; $buf_l=length($buf),makeTwo($fh)) {
if ($buf =~ s/^[\x00\xff]+//) { $buf_ofs += length($1) }
else { last }
}
}
# exit status: 0:clean; 1:exploit; 2:corrupted
sub test_jpeg($;@) {
my($fn) = @_; # file name to be checked
local(*F); my($fh) = \*F;
open($fh,"<$fn") or die "jpeg: Can't open file $fn for reading: $!";
binmode($fh) or die "jpeg: Can't set binmode on $fn: $!";
$buf = ''; $buf_l = 0; $buf_ofs = 0; makeTwo($fh); my(@r) = (0,"jpeg ok");
if ($buf !~ /^\xff\xd8/) { @r = (0,"not jpeg") }
else { takeN($fh,2); if ($buf !~ /^\xff/) { @r = (0,"not jpeg") } }
if ($r[1] eq "jpeg ok") {
my($ecs_ok) = 0; local($1);
for (;;) { # keep at least 2 chars in buff except near eof
if ($buf_l<=0 || $buf eq "\xff") {
@r = (2,"Truncated, no EOI, pos=$buf_ofs") if !$r[0];
last;
} elsif ($buf =~ /^( [^\xff] | \xff \x00 )/x) { # ecs
@r = (2,"Unexpected entropy-coded data segment, pos=$buf_ofs")
if !$ecs_ok && !$r[0];
takeECS($fh); $ecs_ok = 0;
} elsif ($buf =~ /^ \xff+ (?= \xff ) /x) { # fill bytes before marker
takeFill($fh); $ecs_ok = 0;
} elsif ($buf =~ /^ \xff ([^\x00\xff]) /x) { # marker
my($m) = $1; takeN($fh,2);
if ($m =~ /[\xd0-\xd7]/) { # RSTi
# printf("marker segm, pos=%d, marker=0x%02X\n", $buf_ofs,ord($m));
$ecs_ok = 1;
} elsif ($m =~ /[\x01\xd8]/) { # TEM, SOI
# printf("marker segm, pos=%d, marker=0x%02X\n", $buf_ofs,ord($m));
$ecs_ok = 0;
}
elsif ($m eq "\xd9") { # EOI
# printf("marker segm, pos=%d, marker=0x%02X\n", $buf_ofs,ord($m));
takeFill($fh); $ecs_ok = 0;
@r = (2,"Trailing garbage, pos=$buf_ofs") if $buf_l>0 && !$r[0];
last;
} else { # marker segment
$ecs_ok = $m eq "\xda"; # SOS
my($len) = unpack("n",substr($buf,0,2));
# printf("marker segm len %d, pos=%d, marker=0x%02X\n", $len,$buf_ofs,ord($m));
@r = (1,sprintf("Invalid marker segm len %d, pos=%d, marker=0x%02X",
$len,$buf_ofs,ord($m)) ) if $len<2;
my($err) = takeN($fh,$len);
@r = (2,"$err, pos=$buf_ofs") if defined $err && !$r[0];
}
} else { die "jpeg: Panic, program error2, pos=$buf_ofs" }
$buf_l>=2 || makeTwo($fh);
}
}
close($fh) or die "jpeg: Can't close $fn: $!";
$r[1] = "bad jpeg: ".$r[1] if $r[0];
@r;
}
1; # insure a defined return
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