+# FIXME: switch to passing the whole packet as the arg, instead of the
+# input stream.
+
+# given an input stream and data, store the found key in data and
+# consume the rest of the stream corresponding to the packet.
+# data contains: (fpr: fingerprint to find, key: current best guess at key)
+sub findkey {
+ my $data = shift;
+ my $instr = shift;
+ my $tag = shift;
+ my $packetlen = shift;
+
+ my $dummy;
+ my $ver;
+ my $readbytes = 0;
+
+ read($instr, $ver, 1) or die "could not read key version\n";
+ $readbytes += 1;
+ $ver = ord($ver);
+
+ if ($ver != 4) {
+ printf(STDERR "We only work with version 4 keys. This key appears to be version %s.\n", $ver);
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ return;
+ }
+
+ my $key_timestamp;
+ read($instr, $key_timestamp, 4) or die "could not read key timestamp.\n";
+ $readbytes += 4;
+ $key_timestamp = unpack('N', $key_timestamp);
+
+ my $algo;
+ read($instr, $algo, 1) or die "could not read key algorithm.\n";
+ $readbytes += 1;
+ $algo = ord($algo);
+ if ($algo != $asym_algos->{rsa}) {
+ printf(STDERR "We only support RSA keys (this key used algorithm %d).\n", $algo);
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ return;
+ }
+
+ ## we have an RSA key.
+ my $modulus = read_mpi($instr, \$readbytes);
+ my $exponent = read_mpi($instr, \$readbytes);
+
+ my $pubkey = Crypt::OpenSSL::RSA->new_key_from_parameters($modulus, $exponent);
+ my $foundfpr = fingerprint($pubkey, $key_timestamp);
+
+ my $foundfprstr = Crypt::OpenSSL::Bignum->new_from_bin($foundfpr)->to_hex();
+ # left-pad with 0's to bring up to full 40-char (160-bit) fingerprint:
+ $foundfprstr = sprintf("%040s", $foundfprstr);
+
+ # is this a match?
+ if ((!defined($data->{fpr})) ||
+ (substr($foundfprstr, -1 * length($data->{fpr})) eq $data->{fpr})) {
+ if (defined($data->{key})) {
+ die "Found two matching keys.\n";
+ }
+ $data->{key} = $pubkey;
+ }
+
+ if ($tag != $packet_types->{seckey} &&
+ $tag != $packet_types->{sec_subkey}) {
+ if ($readbytes < $packetlen) {
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ }
+ return;
+ }
+ if (!defined($data->{key})) {
+ # we don't think the public part of this key matches
+ if ($readbytes < $packetlen) {
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ }
+ return;
+ }
+
+ my $s2k;
+ read($instr, $s2k, 1) or die "Could not read S2K octet.\n";
+ $readbytes += 1;
+ $s2k = ord($s2k);
+ if ($s2k != 0) {
+ printf(STDERR "We cannot handle encrypted secret keys. Skipping!\n") ;
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ return;
+ }
+
+ # secret material is unencrypted
+ # see http://tools.ietf.org/html/rfc4880#section-5.5.3
+ my $d = read_mpi($instr, \$readbytes);
+ my $p = read_mpi($instr, \$readbytes);
+ my $q = read_mpi($instr, \$readbytes);
+ my $u = read_mpi($instr, \$readbytes);
+
+ my $checksum;
+ read($instr, $checksum, 2) or die "Could not read checksum of secret key material.\n";
+ $readbytes += 2;
+ $checksum = unpack('n', $checksum);
+
+ # FIXME: compare with the checksum! how? the data is
+ # gone into the Crypt::OpenSSL::Bignum
+
+ $data->{key} = Crypt::OpenSSL::RSA->new_key_from_parameters($modulus,
+ $exponent,
+ $d,
+ $p,
+ $q);
+
+ $data->{key}->check_key() or die "Secret key is not a valid RSA key.\n";
+
+ if ($readbytes < $packetlen) {
+ read($instr, $dummy, $packetlen - $readbytes) or die "Could not skip past this packet.\n";
+ }
+}