diff options
Diffstat (limited to 'scripts/x509keyid')
| -rwxr-xr-x | scripts/x509keyid | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/scripts/x509keyid b/scripts/x509keyid new file mode 100755 index 0000000..c8e91a4 --- /dev/null +++ b/scripts/x509keyid @@ -0,0 +1,268 @@ +#!/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 $raw_data; + +die "Need three filenames\n" if ($#ARGV != 2); + +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]); + +open(OUTFD, ">$ARGV[1]") || die $ARGV[1]; +print OUTFD $id_name; +close OUTFD || die $ARGV[1]; + +open(OUTFD, ">$ARGV[2]") || die $ARGV[2]; +print OUTFD $id_key_id; +close OUTFD || die $ARGV[2]; |
