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: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 399 insertions, 346 deletions

diff --git a/scripts/sign-file b/scripts/sign-file
index d014abd11f1c..d37d1309531e 100644..100755
--- a/scripts/sign-file
+++ b/scripts/sign-file
@@ -1,108 +1,429 @@
-#!/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;
+}
diff --git a/scripts/x509keyid b/scripts/x509keyid
deleted file mode 100755
index 4241ec6c64b1..000000000000
--- a/scripts/x509keyid
+++ /dev/null
@@ -1,268 +0,0 @@
-#!/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";
-}