projects/linux·blob v4.13 · refs

137 lines · 3.6 KiB

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