#!/usr/bin/perl -w

  #
  # Sign a module file using the given key.
  #

  
  my $USAGE =
  "Usage: scripts/sign-file [-v] <hash algo> <key> <x509> <module> [<dest>]
  " .
  "       scripts/sign-file [-v] -s <raw sig> <hash algo> <x509> <module> [<dest>]
  ";

  use strict;
  use FileHandle;
  use IPC::Open2;

  use Getopt::Std;

  my %opts;
  getopts('vs:', \%opts) or die $USAGE;
  my $verbose = $opts{'v'};
  my $signature_file = $opts{'s'};

  die $USAGE if ($#ARGV > 4);
  die $USAGE if (!$signature_file && $#ARGV < 3 || $signature_file && $#ARGV < 2);

  my $dgst = shift @ARGV;
  my $private_key;
  if (!$signature_file) {
  	$private_key = shift @ARGV;
  }
  my $x509 = shift @ARGV;
  my $module = shift @ARGV;
  my ($dest, $keep_orig);
  if (@ARGV) {
  	$dest = $ARGV[0];
  	$keep_orig = 1;
  } else {
  	$dest = $module . "~";
  }

  die "Can't read private key
  " if (!$signature_file && !-r $private_key);
  die "Can't read signature file
  " if ($signature_file && !-r $signature_file);

  die "Can't read X.509 certificate
  " unless (-r $x509);
  die "Can't read module
  " unless (-r $module);
  
  #

  # 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 ", $len, "
  "
  	if ($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);

  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 $x509, ": ", $cursor->[0], ": ASN.1 data underrun (elem ", $cursor->[1], ")
  "
  	if ($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, ")
  ";
      }
  
      $cursor->[0] += 2;
      $cursor->[1] -= 2;
  
      die $x509, ": ", $cursor->[0], ": ASN.1 long tag
  "
  	if (($tag & 0x1f) == 0x1f);
      die $x509, ": ", $cursor->[0], ": ASN.1 indefinite length
  "
  	if ($len == 0x80);
  
      if ($len > 0x80) {
  	my $l = $len - 0x80;
  	die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (len len $l)
  "
  	    if ($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, ")
  ";
  	}
  
  	$cursor->[0] += $l;
  	$cursor->[1] -= $l;
      }
  
      die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (", $len, ")
  "
  	if ($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 $x509, ": ", "X.509: Couldn't find the Subject Key Identifier extension
  "
      if (!$subject_key_id);
  
  my $key_identifier = asn1_retrieve($subject_key_id->[1]);
  
  ###############################################################################
  #
  # Create and attach the module signature
  #
  ###############################################################################

  
  #
  # Signature parameters
  #

  my $algo = 1;		# Public-key crypto algorithm: RSA
  my $hash = 0;		# Digest algorithm
  my $id_type = 1;	# Identifier type: X.509

  
  #
  # Digest the data
  #

  my $prologue;
  if ($dgst eq "sha1") {

      $prologue = pack("C*",
  		     0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
  		     0x2B, 0x0E, 0x03, 0x02, 0x1A,
  		     0x05, 0x00, 0x04, 0x14);

      $hash = 2;

  } elsif ($dgst eq "sha224") {

      $prologue = pack("C*",
  		     0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
  		     0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
  		     0x05, 0x00, 0x04, 0x1C);

      $hash = 7;

  } elsif ($dgst eq "sha256") {

      $prologue = pack("C*",
  		     0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
  		     0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
  		     0x05, 0x00, 0x04, 0x20);

      $hash = 4;

  } elsif ($dgst eq "sha384") {

      $prologue = pack("C*",
  		     0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
  		     0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
  		     0x05, 0x00, 0x04, 0x30);

      $hash = 5;

  } elsif ($dgst eq "sha512") {

      $prologue = pack("C*",
  		     0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
  		     0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
  		     0x05, 0x00, 0x04, 0x40);

      $hash = 6;
  } else {

      die "Unknown hash algorithm: $dgst
  ";

  }

  my $signature;

  if ($signature_file) {
  	$signature = read_file($signature_file);
  } else {
  	#
  	# 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.
  	#
  	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;
  	read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
  	close(read_from) || die "pipe from openssl rsautl";
  	waitpid($pid, 0) || die;
  	die "openssl rsautl died: $?" if ($? >> 8);
  }

  $signature = pack("n", length($signature)) . $signature,

  #
  # Build the signed binary
  #

  my $unsigned_module = read_file($module);
  
  my $magic_number = "~Module signature appended~
  ";
  
  my $info = pack("CCCCCxxxN",
  		$algo, $hash, $id_type,
  		length($signers_name),
  		length($key_identifier),
  		length($signature));

  if ($verbose) {
      print "Size of unsigned module: ", length($unsigned_module), "
  ";

      print "Size of signer's name  : ", length($signers_name), "
  ";
      print "Size of key identifier : ", length($key_identifier), "
  ";
      print "Size of signature      : ", length($signature), "
  ";

      print "Size of information    : ", length($info), "
  ";

      print "Size of magic number   : ", length($magic_number), "
  ";

      print "Signer's name          : '", $signers_name, "'
  ";
      print "Digest                 : $dgst
  ";
  }

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

      $signers_name,
      $key_identifier,
      $signature,

      $info,
      $magic_number

      ;
  close FD || die $dest;

  if (!$keep_orig) {

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