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Commit b37d1bfb authored by David Howells's avatar David Howells Committed by Linus Torvalds
Browse files

MODSIGN: perlify sign-file and merge in x509keyid 



Turn sign-file into perl and merge in x509keyid.  The latter doesn't
need to be a separate script as it doesn't actually need to work out the
SHA1 sum of the X.509 certificate itself, since it can get that from the
X.509 certificate.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9e781440

Makefile

+1 −1
Original line number Diff line number Diff line
@@ -723,7 +723,7 @@ ifeq ($(CONFIG_MODULE_SIG),y) 
MODSECKEY = ./signing_key.priv

MODPUBKEY = ./signing_key.x509

export MODPUBKEY

mod_sign_cmd = sh $(srctree)/scripts/sign-file $(MODSECKEY) $(MODPUBKEY) $(srctree)/scripts/x509keyid

mod_sign_cmd = perl $(srctree)/scripts/sign-file $(MODSECKEY) $(MODPUBKEY)

else

mod_sign_cmd = true

endif

scripts/sign-file

100644 → 100755
+399 −78
Original line number Diff line number Diff line 
#!/bin/bash

#!/usr/bin/perl -w

#

# Sign a module file using the given key.

#

# Format: sign-file <key> <x509> <keyid-script> <module>

# 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);

}



scripts=`dirname $0`

#

# 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);



CONFIG_MODULE_SIG_SHA512=y

if [ -r .config ]

then

    . ./.config

fi

my $UNIV = 0 << 6;

my $APPL = 1 << 6;

my $CONT = 2 << 6;

my $PRIV = 3 << 6;



key="$1"

x509="$2"

keyid_script="$3"

mod="$4"

my $CONS = 0x20;



if [ ! -r "$key" ]

then

    echo "Can't read private key" >&2

    exit 2

fi

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;



if [ ! -r "$x509" ]

then

    echo "Can't read X.509 certificate" >&2

    exit 2

fi

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

#

algo=1		# Public-key crypto algorithm: RSA

hash=		# Digest algorithm

id_type=1	# Identifier type: X.509

my $algo = 1;		# Public-key crypto algorithm: RSA

my $hash = 0;		# Digest algorithm

my $id_type = 1;	# Identifier type: X.509



#

# Digest the data

#

dgst=

if [ "$CONFIG_MODULE_SIG_SHA1" = "y" ]

then

    prologue="0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14"

    dgst=-sha1

    hash=2

elif [ "$CONFIG_MODULE_SIG_SHA224" = "y" ]

then

    prologue="0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04, 0x05, 0x00, 0x04, 0x1C"

    dgst=-sha224

    hash=7

elif [ "$CONFIG_MODULE_SIG_SHA256" = "y" ]

then

    prologue="0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20"

    dgst=-sha256

    hash=4

elif [ "$CONFIG_MODULE_SIG_SHA384" = "y" ]

then

    prologue="0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02, 0x05, 0x00, 0x04, 0x30"

    dgst=-sha384

    hash=5

elif [ "$CONFIG_MODULE_SIG_SHA512" = "y" ]

then

    prologue="0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05, 0x00, 0x04, 0x40"

    dgst=-sha512

    hash=6

else

    echo "$0: Can't determine hash algorithm" >&2

    exit 2

fi



(

perl -e "binmode STDOUT; print pack(\"C*\", $prologue)" || exit $?

openssl dgst $dgst -binary $mod || exit $?

) >$mod.dig || exit $?

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.

#

openssl rsautl -sign -inkey $key -keyform PEM -in $mod.dig -out $mod.sig || exit $?

siglen=`stat -c %s $mod.sig`

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,



SIGNER="`perl $keyid_script $x509 signer-name`"

KEYID="`perl $keyid_script $x509 keyid`"

keyidlen=$(echo -n "$KEYID" | wc -c)

signerlen=$(echo -n "$SIGNER" | wc -c)

waitpid($pid, 0) || die;

die "openssl rsautl died: $?" if ($? >> 8);



#

# Build the signed binary

#

(

    cat $mod || exit $?

    echo '~Module signature appended~' || exit $?

    echo -n "$SIGNER" || exit $?

    echo -n "$KEYID" || exit $?

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));



    # Preface each signature integer with a 2-byte BE length

    perl -e "binmode STDOUT; print pack(\"n\", $siglen)" || exit $?

    cat $mod.sig || exit $?

if ($verbose) {

    print "Size of unsigned module: ", length($unsigned_module), "\n";

    print "Size of magic number   : ", length($magic_number), "\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 "Signer's name          : '", $signers_name, "'\n";

    print "Digest                 : $dgst\n";

}



    # Generate the information block

    perl -e "binmode STDOUT; print pack(\"CCCCCxxxN\", $algo, $hash, $id_type, $signerlen, $keyidlen, $siglen + 2)" || exit $?

) >$mod~ || exit $?

open(FD, ">$dest") || die $dest;

binmode FD;

print FD

    $unsigned_module,

    $magic_number,

    $signers_name,

    $key_identifier,

    $signature,

    $info

    ;

close FD || die $dest;



mv $mod~ $mod || exit $?
 
if ($#ARGV != 3) {

    rename($dest, $module) || die $module;

}

scripts/x509keyid

deleted100755 → 0
+0 −268
Original line number Diff line number Diff line 
#!/usr/bin/perl -w

#

# Generate an identifier from an X.509 certificate that can be placed in a

# module signature to indentify the key to use.

#

# Format:

#

#	./scripts/x509keyid <x509-cert> <signer's-name> <key-id>

#

# We read the DER-encoded X509 certificate and parse it to extract the Subject

# name and Subject Key Identifier.  The provide 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 and written to the second named file.

#

# The subject key ID to select which of that signer's certificates we're

# intending to use to sign the module is written to the third named file.

#

use strict;



my $raw_data;



die "Need a filename [keyid|signer-name]\n" if ($#ARGV != 1);



my $src = $ARGV[0];



open(FD, "<$src") || die $src;

binmode FD;

my @st = stat(FD);

die $src if (!@st);

read(FD, $raw_data, $st[7]) || die $src;

close(FD);



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 $src, ": ", $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 $src, ": ", $cursor->[0], ": ASN.1 unexpected tag (", $tag,

	" not ", $expected_tag, ")\n";

    }



    $cursor->[0] += 2;

    $cursor->[1] -= 2;



    die $src, ": ", $cursor->[0], ": ASN.1 long tag\n"

	if (($tag & 0x1f) == 0x1f);

    die $src, ": ", $cursor->[0], ": ASN.1 indefinite length\n"

	if ($len == 0x80);



    if ($len > 0x80) {

	my $l = $len - 0x80;

	die $src, ": ", $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 $src, ": ", $cursor->[0], ": ASN.1 element too long (", $l, ")\n";

	}



	$cursor->[0] += $l;

	$cursor->[1] -= $l;

    }



    die $src, ": ", $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 $cursor = [ 0, length($raw_data), \$raw_data ];



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 $id_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) {

	$id_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)) {

	$id_name = $cn;

	goto got_id_name;

    }



    $id_name = $org . ": " . $cn;

} elsif ($org) {

    $id_name = $org;

} elsif ($cn) {

    $id_name = $cn;

}



got_id_name:



###############################################################################

#

# Output the signer's name and the key identifier that we're going to include

# in module signatures.

#

###############################################################################

die $src, ": ", "X.509: Couldn't find the Subject Key Identifier extension\n"

    if (!$subject_key_id);



my $id_key_id = asn1_retrieve($subject_key_id->[1]);



if ($ARGV[1] eq "signer-name") {

    print $id_name;

} elsif ($ARGV[1] eq "keyid") {

    print $id_key_id;

} else {

    die "Unknown arg";

}