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linux/scripts/sign-file

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Perl
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#!/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;
}
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