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package JpegTester; # Author: Mark Martinec <Mark.Martinec@ijs.si>, 2004-10; # The 2-clause 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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