85ecac7945
Provide a script to parse an X.509 certificate and certain pieces of
information from it in order to generate a key identifier to be included within
a module signature.
The script takes the Subject Name and extracts (if present) the
organizationName (O), the commonName (CN) and the emailAddress and fabricates
the signer's name from them:
(1) If both O and CN exist, then the name will be "O: CN", unless:
(a) CN is prefixed by O, in which case only CN is used.
(b) CN and O share at least the first 7 characters, in which case only CN
is used.
(2) Otherwise, CN is used if present.
(3) Otherwise, O is used if present.
(4) Otherwise the emailAddress is used, if present.
(5) Otherwise a blank name is used.
The script emits a binary encoded identifier in the following form:
- 2 BE bytes indicating the length of the signer's name.
- 2 BE bytes indicating the length of the subject key identifier.
- The characters of the signer's name.
- The bytes of the subject key identifier.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
268 lines
8 KiB
Perl
Executable file
268 lines
8 KiB
Perl
Executable file
#!/usr/bin/perl -w
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#
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# Generate an identifier from an X.509 certificate that can be placed in a
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# module signature to indentify the key to use.
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#
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# Format:
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#
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# ./scripts/x509keyid <x509-cert> <signer's-name> <key-id>
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#
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# We read the DER-encoded X509 certificate and parse it to extract the Subject
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# name and Subject Key Identifier. The provide the data we need to build the
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# certificate identifier.
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#
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# The signer's name part of the identifier is fabricated from the commonName,
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# the organizationName or the emailAddress components of the X.509 subject
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# name and written to the second named file.
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#
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# The subject key ID to select which of that signer's certificates we're
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# intending to use to sign the module is written to the third named file.
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#
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use strict;
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my $raw_data;
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die "Need three filenames\n" if ($#ARGV != 2);
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my $src = $ARGV[0];
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open(FD, "<$src") || die $src;
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binmode FD;
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my @st = stat(FD);
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die $src if (!@st);
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read(FD, $raw_data, $st[7]) || die $src;
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close(FD);
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my $UNIV = 0 << 6;
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my $APPL = 1 << 6;
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my $CONT = 2 << 6;
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my $PRIV = 3 << 6;
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my $CONS = 0x20;
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my $BOOLEAN = 0x01;
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my $INTEGER = 0x02;
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my $BIT_STRING = 0x03;
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my $OCTET_STRING = 0x04;
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my $NULL = 0x05;
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my $OBJ_ID = 0x06;
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my $UTF8String = 0x0c;
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my $SEQUENCE = 0x10;
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my $SET = 0x11;
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my $UTCTime = 0x17;
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my $GeneralizedTime = 0x18;
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my %OIDs = (
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pack("CCC", 85, 4, 3) => "commonName",
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pack("CCC", 85, 4, 6) => "countryName",
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pack("CCC", 85, 4, 10) => "organizationName",
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pack("CCC", 85, 4, 11) => "organizationUnitName",
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pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 1) => "rsaEncryption",
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pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 5) => "sha1WithRSAEncryption",
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pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 9, 1) => "emailAddress",
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pack("CCC", 85, 29, 35) => "authorityKeyIdentifier",
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pack("CCC", 85, 29, 14) => "subjectKeyIdentifier",
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pack("CCC", 85, 29, 19) => "basicConstraints"
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);
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###############################################################################
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#
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# Extract an ASN.1 element from a string and return information about it.
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#
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###############################################################################
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sub asn1_extract($$@)
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{
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my ($cursor, $expected_tag, $optional) = @_;
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return [ -1 ]
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if ($cursor->[1] == 0 && $optional);
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die $src, ": ", $cursor->[0], ": ASN.1 data underrun (elem ", $cursor->[1], ")\n"
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if ($cursor->[1] < 2);
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my ($tag, $len) = unpack("CC", substr(${$cursor->[2]}, $cursor->[0], 2));
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if ($expected_tag != -1 && $tag != $expected_tag) {
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return [ -1 ]
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if ($optional);
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die $src, ": ", $cursor->[0], ": ASN.1 unexpected tag (", $tag,
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" not ", $expected_tag, ")\n";
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}
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$cursor->[0] += 2;
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$cursor->[1] -= 2;
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die $src, ": ", $cursor->[0], ": ASN.1 long tag\n"
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if (($tag & 0x1f) == 0x1f);
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die $src, ": ", $cursor->[0], ": ASN.1 indefinite length\n"
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if ($len == 0x80);
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if ($len > 0x80) {
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my $l = $len - 0x80;
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die $src, ": ", $cursor->[0], ": ASN.1 data underrun (len len $l)\n"
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if ($cursor->[1] < $l);
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if ($l == 0x1) {
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$len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1));
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} elsif ($l = 0x2) {
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$len = unpack("n", substr(${$cursor->[2]}, $cursor->[0], 2));
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} elsif ($l = 0x3) {
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$len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1)) << 16;
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$len = unpack("n", substr(${$cursor->[2]}, $cursor->[0] + 1, 2));
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} elsif ($l = 0x4) {
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$len = unpack("N", substr(${$cursor->[2]}, $cursor->[0], 4));
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} else {
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die $src, ": ", $cursor->[0], ": ASN.1 element too long (", $l, ")\n";
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}
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$cursor->[0] += $l;
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$cursor->[1] -= $l;
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}
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die $src, ": ", $cursor->[0], ": ASN.1 data underrun (", $len, ")\n"
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if ($cursor->[1] < $len);
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my $ret = [ $tag, [ $cursor->[0], $len, $cursor->[2] ] ];
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$cursor->[0] += $len;
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$cursor->[1] -= $len;
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return $ret;
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}
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###############################################################################
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#
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# Retrieve the data referred to by a cursor
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#
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###############################################################################
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sub asn1_retrieve($)
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{
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my ($cursor) = @_;
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my ($offset, $len, $data) = @$cursor;
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return substr($$data, $offset, $len);
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}
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###############################################################################
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#
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# Roughly parse the X.509 certificate
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#
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###############################################################################
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my $cursor = [ 0, length($raw_data), \$raw_data ];
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my $cert = asn1_extract($cursor, $UNIV | $CONS | $SEQUENCE);
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my $tbs = asn1_extract($cert->[1], $UNIV | $CONS | $SEQUENCE);
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my $version = asn1_extract($tbs->[1], $CONT | $CONS | 0, 1);
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my $serial_number = asn1_extract($tbs->[1], $UNIV | $INTEGER);
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my $sig_type = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
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my $issuer = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
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my $validity = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
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my $subject = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
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my $key = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
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my $issuer_uid = asn1_extract($tbs->[1], $CONT | $CONS | 1, 1);
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my $subject_uid = asn1_extract($tbs->[1], $CONT | $CONS | 2, 1);
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my $extension_list = asn1_extract($tbs->[1], $CONT | $CONS | 3, 1);
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my $subject_key_id = ();
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my $authority_key_id = ();
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#
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# Parse the extension list
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#
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if ($extension_list->[0] != -1) {
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my $extensions = asn1_extract($extension_list->[1], $UNIV | $CONS | $SEQUENCE);
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while ($extensions->[1]->[1] > 0) {
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my $ext = asn1_extract($extensions->[1], $UNIV | $CONS | $SEQUENCE);
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my $x_oid = asn1_extract($ext->[1], $UNIV | $OBJ_ID);
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my $x_crit = asn1_extract($ext->[1], $UNIV | $BOOLEAN, 1);
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my $x_val = asn1_extract($ext->[1], $UNIV | $OCTET_STRING);
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my $raw_oid = asn1_retrieve($x_oid->[1]);
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next if (!exists($OIDs{$raw_oid}));
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my $x_type = $OIDs{$raw_oid};
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my $raw_value = asn1_retrieve($x_val->[1]);
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if ($x_type eq "subjectKeyIdentifier") {
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my $vcursor = [ 0, length($raw_value), \$raw_value ];
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$subject_key_id = asn1_extract($vcursor, $UNIV | $OCTET_STRING);
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}
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}
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}
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###############################################################################
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#
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# Determine what we're going to use as the signer's name. In order of
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# preference, take one of: commonName, organizationName or emailAddress.
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#
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###############################################################################
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my $org = "";
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my $cn = "";
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my $email = "";
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while ($subject->[1]->[1] > 0) {
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my $rdn = asn1_extract($subject->[1], $UNIV | $CONS | $SET);
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my $attr = asn1_extract($rdn->[1], $UNIV | $CONS | $SEQUENCE);
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my $n_oid = asn1_extract($attr->[1], $UNIV | $OBJ_ID);
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my $n_val = asn1_extract($attr->[1], -1);
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my $raw_oid = asn1_retrieve($n_oid->[1]);
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next if (!exists($OIDs{$raw_oid}));
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my $n_type = $OIDs{$raw_oid};
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my $raw_value = asn1_retrieve($n_val->[1]);
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if ($n_type eq "organizationName") {
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$org = $raw_value;
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} elsif ($n_type eq "commonName") {
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$cn = $raw_value;
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} elsif ($n_type eq "emailAddress") {
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$email = $raw_value;
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}
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}
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my $id_name = $email;
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if ($org && $cn) {
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# Don't use the organizationName if the commonName repeats it
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if (length($org) <= length($cn) &&
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substr($cn, 0, length($org)) eq $org) {
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$id_name = $cn;
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goto got_id_name;
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}
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# Or a signifcant chunk of it
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if (length($org) >= 7 &&
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length($cn) >= 7 &&
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substr($cn, 0, 7) eq substr($org, 0, 7)) {
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$id_name = $cn;
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goto got_id_name;
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}
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$id_name = $org . ": " . $cn;
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} elsif ($org) {
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$id_name = $org;
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} elsif ($cn) {
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$id_name = $cn;
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}
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got_id_name:
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###############################################################################
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#
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# Output the signer's name and the key identifier that we're going to include
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# in module signatures.
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#
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###############################################################################
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die $src, ": ", "X.509: Couldn't find the Subject Key Identifier extension\n"
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if (!$subject_key_id);
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my $id_key_id = asn1_retrieve($subject_key_id->[1]);
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open(OUTFD, ">$ARGV[1]") || die $ARGV[1];
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print OUTFD $id_name;
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close OUTFD || die $ARGV[1];
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open(OUTFD, ">$ARGV[2]") || die $ARGV[2];
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print OUTFD $id_key_id;
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close OUTFD || die $ARGV[2];
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