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- #!/usr/bin/perl -w
- #
- # extract-mod-sig <part> <module-file>
- #
- # Reads the module file and writes out some or all of the signature
- # section to stdout. Part is the bit to be written and is one of:
- #
- # -0: The unsigned module, no signature data at all
- # -a: All of the signature data, including magic number
- # -d: Just the descriptor values as a sequence of numbers
- # -n: Just the signer's name
- # -k: Just the key ID
- # -s: Just the crypto signature or PKCS#7 message
- #
- use strict;
- die "Format: $0 -[0adnks] module-file >out\n"
- if ($#ARGV != 1);
- my $part = $ARGV[0];
- my $modfile = $ARGV[1];
- my $magic_number = "~Module signature appended~\n";
- #
- # Read the module contents
- #
- open FD, "<$modfile" || die $modfile;
- binmode(FD);
- my @st = stat(FD);
- die "$modfile" unless (@st);
- my $buf = "";
- my $len = sysread(FD, $buf, $st[7]);
- die "$modfile" unless (defined($len));
- die "Short read on $modfile\n" unless ($len == $st[7]);
- close(FD) || die $modfile;
- print STDERR "Read ", $len, " bytes from module file\n";
- die "The file is too short to have a sig magic number and descriptor\n"
- if ($len < 12 + length($magic_number));
- #
- # Check for the magic number and extract the information block
- #
- my $p = $len - length($magic_number);
- my $raw_magic = substr($buf, $p);
- die "Magic number not found at $len\n"
- if ($raw_magic ne $magic_number);
- print STDERR "Found magic number at $len\n";
- $p -= 12;
- my $raw_info = substr($buf, $p, 12);
- my @info = unpack("CCCCCxxxN", $raw_info);
- my ($algo, $hash, $id_type, $name_len, $kid_len, $sig_len) = @info;
- if ($id_type == 0) {
- print STDERR "Found PGP key identifier\n";
- } elsif ($id_type == 1) {
- print STDERR "Found X.509 cert identifier\n";
- } elsif ($id_type == 2) {
- print STDERR "Found PKCS#7/CMS encapsulation\n";
- } else {
- print STDERR "Found unsupported identifier type $id_type\n";
- }
- #
- # Extract the three pieces of info data
- #
- die "Insufficient name+kid+sig data in file\n"
- unless ($p >= $name_len + $kid_len + $sig_len);
- $p -= $sig_len;
- my $raw_sig = substr($buf, $p, $sig_len);
- $p -= $kid_len;
- my $raw_kid = substr($buf, $p, $kid_len);
- $p -= $name_len;
- my $raw_name = substr($buf, $p, $name_len);
- my $module_len = $p;
- if ($sig_len > 0) {
- print STDERR "Found $sig_len bytes of signature [";
- my $n = $sig_len > 16 ? 16 : $sig_len;
- foreach my $i (unpack("C" x $n, substr($raw_sig, 0, $n))) {
- printf STDERR "%02x", $i;
- }
- print STDERR "]\n";
- }
- if ($kid_len > 0) {
- print STDERR "Found $kid_len bytes of key identifier [";
- my $n = $kid_len > 16 ? 16 : $kid_len;
- foreach my $i (unpack("C" x $n, substr($raw_kid, 0, $n))) {
- printf STDERR "%02x", $i;
- }
- print STDERR "]\n";
- }
- if ($name_len > 0) {
- print STDERR "Found $name_len bytes of signer's name [$raw_name]\n";
- }
- #
- # Produce the requested output
- #
- if ($part eq "-0") {
- # The unsigned module, no signature data at all
- binmode(STDOUT);
- print substr($buf, 0, $module_len);
- } elsif ($part eq "-a") {
- # All of the signature data, including magic number
- binmode(STDOUT);
- print substr($buf, $module_len);
- } elsif ($part eq "-d") {
- # Just the descriptor values as a sequence of numbers
- print join(" ", @info), "\n";
- } elsif ($part eq "-n") {
- # Just the signer's name
- print STDERR "No signer's name for PKCS#7 message type sig\n"
- if ($id_type == 2);
- binmode(STDOUT);
- print $raw_name;
- } elsif ($part eq "-k") {
- # Just the key identifier
- print STDERR "No key ID for PKCS#7 message type sig\n"
- if ($id_type == 2);
- binmode(STDOUT);
- print $raw_kid;
- } elsif ($part eq "-s") {
- # Just the crypto signature or PKCS#7 message
- binmode(STDOUT);
- print $raw_sig;
- }
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