1#!/usr/bin/perl -w 2# 3# extract-mod-sig <part> <module-file> 4# 5# Reads the module file and writes out some or all of the signature 6# section to stdout. Part is the bit to be written and is one of: 7# 8# -0: The unsigned module, no signature data at all 9# -a: All of the signature data, including magic number 10# -d: Just the descriptor values as a sequence of numbers 11# -n: Just the signer's name 12# -k: Just the key ID 13# -s: Just the crypto signature or PKCS#7 message 14# 15use strict; 16 17die "Format: $0 -[0adnks] module-file >out\n" 18 if ($#ARGV != 1); 19 20my $part = $ARGV[0]; 21my $modfile = $ARGV[1]; 22 23my $magic_number = "~Module signature appended~\n"; 24 25# 26# Read the module contents 27# 28open FD, "<$modfile" || die $modfile; 29binmode(FD); 30my @st = stat(FD); 31die "$modfile" unless (@st); 32my $buf = ""; 33my $len = sysread(FD, $buf, $st[7]); 34die "$modfile" unless (defined($len)); 35die "Short read on $modfile\n" unless ($len == $st[7]); 36close(FD) || die $modfile; 37 38print STDERR "Read ", $len, " bytes from module file\n"; 39 40die "The file is too short to have a sig magic number and descriptor\n" 41 if ($len < 12 + length($magic_number)); 42 43# 44# Check for the magic number and extract the information block 45# 46my $p = $len - length($magic_number); 47my $raw_magic = substr($buf, $p); 48 49die "Magic number not found at $len\n" 50 if ($raw_magic ne $magic_number); 51print STDERR "Found magic number at $len\n"; 52 53$p -= 12; 54my $raw_info = substr($buf, $p, 12); 55 56my @info = unpack("CCCCCxxxN", $raw_info); 57my ($algo, $hash, $id_type, $name_len, $kid_len, $sig_len) = @info; 58 59if ($id_type == 0) { 60 print STDERR "Found PGP key identifier\n"; 61} elsif ($id_type == 1) { 62 print STDERR "Found X.509 cert identifier\n"; 63} elsif ($id_type == 2) { 64 print STDERR "Found PKCS#7/CMS encapsulation\n"; 65} else { 66 print STDERR "Found unsupported identifier type $id_type\n"; 67} 68 69# 70# Extract the three pieces of info data 71# 72die "Insufficient name+kid+sig data in file\n" 73 unless ($p >= $name_len + $kid_len + $sig_len); 74 75$p -= $sig_len; 76my $raw_sig = substr($buf, $p, $sig_len); 77$p -= $kid_len; 78my $raw_kid = substr($buf, $p, $kid_len); 79$p -= $name_len; 80my $raw_name = substr($buf, $p, $name_len); 81 82my $module_len = $p; 83 84if ($sig_len > 0) { 85 print STDERR "Found $sig_len bytes of signature ["; 86 my $n = $sig_len > 16 ? 16 : $sig_len; 87 foreach my $i (unpack("C" x $n, substr($raw_sig, 0, $n))) { 88 printf STDERR "%02x", $i; 89 } 90 print STDERR "]\n"; 91} 92 93if ($kid_len > 0) { 94 print STDERR "Found $kid_len bytes of key identifier ["; 95 my $n = $kid_len > 16 ? 16 : $kid_len; 96 foreach my $i (unpack("C" x $n, substr($raw_kid, 0, $n))) { 97 printf STDERR "%02x", $i; 98 } 99 print STDERR "]\n"; 100} 101 102if ($name_len > 0) { 103 print STDERR "Found $name_len bytes of signer's name [$raw_name]\n"; 104} 105 106# 107# Produce the requested output 108# 109if ($part eq "-0") { 110 # The unsigned module, no signature data at all 111 binmode(STDOUT); 112 print substr($buf, 0, $module_len); 113} elsif ($part eq "-a") { 114 # All of the signature data, including magic number 115 binmode(STDOUT); 116 print substr($buf, $module_len); 117} elsif ($part eq "-d") { 118 # Just the descriptor values as a sequence of numbers 119 print join(" ", @info), "\n"; 120} elsif ($part eq "-n") { 121 # Just the signer's name 122 print STDERR "No signer's name for PKCS#7 message type sig\n" 123 if ($id_type == 2); 124 binmode(STDOUT); 125 print $raw_name; 126} elsif ($part eq "-k") { 127 # Just the key identifier 128 print STDERR "No key ID for PKCS#7 message type sig\n" 129 if ($id_type == 2); 130 binmode(STDOUT); 131 print $raw_kid; 132} elsif ($part eq "-s") { 133 # Just the crypto signature or PKCS#7 message 134 binmode(STDOUT); 135 print $raw_sig; 136} 137