LXR linux/scripts/extract-module-sig.pl

   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