linux/scripts/sign-file
David Howells caabe24057 MODSIGN: Move the magic string to the end of a module and eliminate the search
Emit the magic string that indicates a module has a signature after the
signature data instead of before it.  This allows module_sig_check() to
be made simpler and faster by the elimination of the search for the
magic string.  Instead we just need to do a single memcmp().

This works because at the end of the signature data there is the
fixed-length signature information block.  This block then falls
immediately prior to the magic number.

From the contents of the information block, it is trivial to calculate
the size of the signature data and thus the size of the actual module
data.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-19 17:30:40 -07:00

429 lines
12 KiB
Perl
Executable file

#!/usr/bin/perl -w
#
# Sign a module file using the given key.
#
# Format:
#
# ./scripts/sign-file [-v] <key> <x509> <module> [<dest>]
#
#
use strict;
use FileHandle;
use IPC::Open2;
my $verbose = 0;
if ($#ARGV >= 0 && $ARGV[0] eq "-v") {
$verbose = 1;
shift;
}
die "Format: ./scripts/sign-file [-v] <key> <x509> <module> [<dest>]\n"
if ($#ARGV != 2 && $#ARGV != 3);
my $private_key = $ARGV[0];
my $x509 = $ARGV[1];
my $module = $ARGV[2];
my $dest = ($#ARGV == 3) ? $ARGV[3] : $ARGV[2] . "~";
die "Can't read private key\n" unless (-r $private_key);
die "Can't read X.509 certificate\n" unless (-r $x509);
die "Can't read module\n" unless (-r $module);
#
# Read the kernel configuration
#
my %config = (
CONFIG_MODULE_SIG_SHA512 => 1
);
if (-r ".config") {
open(FD, "<.config") || die ".config";
while (<FD>) {
if ($_ =~ /^(CONFIG_.*)=[ym]/) {
$config{$1} = 1;
}
}
close(FD);
}
#
# Function to read the contents of a file into a variable.
#
sub read_file($)
{
my ($file) = @_;
my $contents;
my $len;
open(FD, "<$file") || die $file;
binmode FD;
my @st = stat(FD);
die $file if (!@st);
$len = read(FD, $contents, $st[7]) || die $file;
close(FD) || die $file;
die "$file: Wanted length ", $st[7], ", got ", $len, "\n"
if ($len != $st[7]);
return $contents;
}
###############################################################################
#
# First of all, we have to parse the X.509 certificate to find certain details
# about it.
#
# We read the DER-encoded X509 certificate and parse it to extract the Subject
# name and Subject Key Identifier. Theis provides the data we need to build
# the certificate identifier.
#
# The signer's name part of the identifier is fabricated from the commonName,
# the organizationName or the emailAddress components of the X.509 subject
# name.
#
# The subject key ID is used to select which of that signer's certificates
# we're intending to use to sign the module.
#
###############################################################################
my $x509_certificate = read_file($x509);
my $UNIV = 0 << 6;
my $APPL = 1 << 6;
my $CONT = 2 << 6;
my $PRIV = 3 << 6;
my $CONS = 0x20;
my $BOOLEAN = 0x01;
my $INTEGER = 0x02;
my $BIT_STRING = 0x03;
my $OCTET_STRING = 0x04;
my $NULL = 0x05;
my $OBJ_ID = 0x06;
my $UTF8String = 0x0c;
my $SEQUENCE = 0x10;
my $SET = 0x11;
my $UTCTime = 0x17;
my $GeneralizedTime = 0x18;
my %OIDs = (
pack("CCC", 85, 4, 3) => "commonName",
pack("CCC", 85, 4, 6) => "countryName",
pack("CCC", 85, 4, 10) => "organizationName",
pack("CCC", 85, 4, 11) => "organizationUnitName",
pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 1) => "rsaEncryption",
pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 5) => "sha1WithRSAEncryption",
pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 9, 1) => "emailAddress",
pack("CCC", 85, 29, 35) => "authorityKeyIdentifier",
pack("CCC", 85, 29, 14) => "subjectKeyIdentifier",
pack("CCC", 85, 29, 19) => "basicConstraints"
);
###############################################################################
#
# Extract an ASN.1 element from a string and return information about it.
#
###############################################################################
sub asn1_extract($$@)
{
my ($cursor, $expected_tag, $optional) = @_;
return [ -1 ]
if ($cursor->[1] == 0 && $optional);
die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (elem ", $cursor->[1], ")\n"
if ($cursor->[1] < 2);
my ($tag, $len) = unpack("CC", substr(${$cursor->[2]}, $cursor->[0], 2));
if ($expected_tag != -1 && $tag != $expected_tag) {
return [ -1 ]
if ($optional);
die $x509, ": ", $cursor->[0], ": ASN.1 unexpected tag (", $tag,
" not ", $expected_tag, ")\n";
}
$cursor->[0] += 2;
$cursor->[1] -= 2;
die $x509, ": ", $cursor->[0], ": ASN.1 long tag\n"
if (($tag & 0x1f) == 0x1f);
die $x509, ": ", $cursor->[0], ": ASN.1 indefinite length\n"
if ($len == 0x80);
if ($len > 0x80) {
my $l = $len - 0x80;
die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (len len $l)\n"
if ($cursor->[1] < $l);
if ($l == 0x1) {
$len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1));
} elsif ($l = 0x2) {
$len = unpack("n", substr(${$cursor->[2]}, $cursor->[0], 2));
} elsif ($l = 0x3) {
$len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1)) << 16;
$len = unpack("n", substr(${$cursor->[2]}, $cursor->[0] + 1, 2));
} elsif ($l = 0x4) {
$len = unpack("N", substr(${$cursor->[2]}, $cursor->[0], 4));
} else {
die $x509, ": ", $cursor->[0], ": ASN.1 element too long (", $l, ")\n";
}
$cursor->[0] += $l;
$cursor->[1] -= $l;
}
die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (", $len, ")\n"
if ($cursor->[1] < $len);
my $ret = [ $tag, [ $cursor->[0], $len, $cursor->[2] ] ];
$cursor->[0] += $len;
$cursor->[1] -= $len;
return $ret;
}
###############################################################################
#
# Retrieve the data referred to by a cursor
#
###############################################################################
sub asn1_retrieve($)
{
my ($cursor) = @_;
my ($offset, $len, $data) = @$cursor;
return substr($$data, $offset, $len);
}
###############################################################################
#
# Roughly parse the X.509 certificate
#
###############################################################################
my $cursor = [ 0, length($x509_certificate), \$x509_certificate ];
my $cert = asn1_extract($cursor, $UNIV | $CONS | $SEQUENCE);
my $tbs = asn1_extract($cert->[1], $UNIV | $CONS | $SEQUENCE);
my $version = asn1_extract($tbs->[1], $CONT | $CONS | 0, 1);
my $serial_number = asn1_extract($tbs->[1], $UNIV | $INTEGER);
my $sig_type = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
my $issuer = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
my $validity = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
my $subject = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
my $key = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
my $issuer_uid = asn1_extract($tbs->[1], $CONT | $CONS | 1, 1);
my $subject_uid = asn1_extract($tbs->[1], $CONT | $CONS | 2, 1);
my $extension_list = asn1_extract($tbs->[1], $CONT | $CONS | 3, 1);
my $subject_key_id = ();
my $authority_key_id = ();
#
# Parse the extension list
#
if ($extension_list->[0] != -1) {
my $extensions = asn1_extract($extension_list->[1], $UNIV | $CONS | $SEQUENCE);
while ($extensions->[1]->[1] > 0) {
my $ext = asn1_extract($extensions->[1], $UNIV | $CONS | $SEQUENCE);
my $x_oid = asn1_extract($ext->[1], $UNIV | $OBJ_ID);
my $x_crit = asn1_extract($ext->[1], $UNIV | $BOOLEAN, 1);
my $x_val = asn1_extract($ext->[1], $UNIV | $OCTET_STRING);
my $raw_oid = asn1_retrieve($x_oid->[1]);
next if (!exists($OIDs{$raw_oid}));
my $x_type = $OIDs{$raw_oid};
my $raw_value = asn1_retrieve($x_val->[1]);
if ($x_type eq "subjectKeyIdentifier") {
my $vcursor = [ 0, length($raw_value), \$raw_value ];
$subject_key_id = asn1_extract($vcursor, $UNIV | $OCTET_STRING);
}
}
}
###############################################################################
#
# Determine what we're going to use as the signer's name. In order of
# preference, take one of: commonName, organizationName or emailAddress.
#
###############################################################################
my $org = "";
my $cn = "";
my $email = "";
while ($subject->[1]->[1] > 0) {
my $rdn = asn1_extract($subject->[1], $UNIV | $CONS | $SET);
my $attr = asn1_extract($rdn->[1], $UNIV | $CONS | $SEQUENCE);
my $n_oid = asn1_extract($attr->[1], $UNIV | $OBJ_ID);
my $n_val = asn1_extract($attr->[1], -1);
my $raw_oid = asn1_retrieve($n_oid->[1]);
next if (!exists($OIDs{$raw_oid}));
my $n_type = $OIDs{$raw_oid};
my $raw_value = asn1_retrieve($n_val->[1]);
if ($n_type eq "organizationName") {
$org = $raw_value;
} elsif ($n_type eq "commonName") {
$cn = $raw_value;
} elsif ($n_type eq "emailAddress") {
$email = $raw_value;
}
}
my $signers_name = $email;
if ($org && $cn) {
# Don't use the organizationName if the commonName repeats it
if (length($org) <= length($cn) &&
substr($cn, 0, length($org)) eq $org) {
$signers_name = $cn;
goto got_id_name;
}
# Or a signifcant chunk of it
if (length($org) >= 7 &&
length($cn) >= 7 &&
substr($cn, 0, 7) eq substr($org, 0, 7)) {
$signers_name = $cn;
goto got_id_name;
}
$signers_name = $org . ": " . $cn;
} elsif ($org) {
$signers_name = $org;
} elsif ($cn) {
$signers_name = $cn;
}
got_id_name:
die $x509, ": ", "X.509: Couldn't find the Subject Key Identifier extension\n"
if (!$subject_key_id);
my $key_identifier = asn1_retrieve($subject_key_id->[1]);
###############################################################################
#
# Create and attach the module signature
#
###############################################################################
#
# Signature parameters
#
my $algo = 1; # Public-key crypto algorithm: RSA
my $hash = 0; # Digest algorithm
my $id_type = 1; # Identifier type: X.509
#
# Digest the data
#
my ($dgst, $prologue) = ();
if (exists $config{"CONFIG_MODULE_SIG_SHA1"}) {
$prologue = pack("C*",
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2B, 0x0E, 0x03, 0x02, 0x1A,
0x05, 0x00, 0x04, 0x14);
$dgst = "-sha1";
$hash = 2;
} elsif (exists $config{"CONFIG_MODULE_SIG_SHA224"}) {
$prologue = pack("C*",
0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
0x05, 0x00, 0x04, 0x1C);
$dgst = "-sha224";
$hash = 7;
} elsif (exists $config{"CONFIG_MODULE_SIG_SHA256"}) {
$prologue = pack("C*",
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
0x05, 0x00, 0x04, 0x20);
$dgst = "-sha256";
$hash = 4;
} elsif (exists $config{"CONFIG_MODULE_SIG_SHA384"}) {
$prologue = pack("C*",
0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
0x05, 0x00, 0x04, 0x30);
$dgst = "-sha384";
$hash = 5;
} elsif (exists $config{"CONFIG_MODULE_SIG_SHA512"}) {
$prologue = pack("C*",
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
0x05, 0x00, 0x04, 0x40);
$dgst = "-sha512";
$hash = 6;
} else {
die "Can't determine hash algorithm";
}
#
# Generate the digest and read from openssl's stdout
#
my $digest;
$digest = readpipe("openssl dgst $dgst -binary $module") || die "openssl dgst";
#
# Generate the binary signature, which will be just the integer that comprises
# the signature with no metadata attached.
#
my $pid;
$pid = open2(*read_from, *write_to,
"openssl rsautl -sign -inkey $private_key -keyform PEM") ||
die "openssl rsautl";
binmode write_to;
print write_to $prologue . $digest || die "pipe to openssl rsautl";
close(write_to) || die "pipe to openssl rsautl";
binmode read_from;
my $signature;
read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
close(read_from) || die "pipe from openssl rsautl";
$signature = pack("n", length($signature)) . $signature,
waitpid($pid, 0) || die;
die "openssl rsautl died: $?" if ($? >> 8);
#
# Build the signed binary
#
my $unsigned_module = read_file($module);
my $magic_number = "~Module signature appended~\n";
my $info = pack("CCCCCxxxN",
$algo, $hash, $id_type,
length($signers_name),
length($key_identifier),
length($signature));
if ($verbose) {
print "Size of unsigned module: ", length($unsigned_module), "\n";
print "Size of signer's name : ", length($signers_name), "\n";
print "Size of key identifier : ", length($key_identifier), "\n";
print "Size of signature : ", length($signature), "\n";
print "Size of informaton : ", length($info), "\n";
print "Size of magic number : ", length($magic_number), "\n";
print "Signer's name : '", $signers_name, "'\n";
print "Digest : $dgst\n";
}
open(FD, ">$dest") || die $dest;
binmode FD;
print FD
$unsigned_module,
$signers_name,
$key_identifier,
$signature,
$info,
$magic_number
;
close FD || die $dest;
if ($#ARGV != 3) {
rename($dest, $module) || die $module;
}