scripts/sign-file

   1 #!/usr/bin/perl -w
   2 #
   3 # Sign a module file using the given key.
   4 #
   5 # Format:
   6 #
   7 #       ./scripts/sign-file [-v] <key> <x509> <module> [<dest>]
   8 #
   9 #
  10 use strict;
  11 use FileHandle;
  12 use IPC::Open2;
  13
  14 my $verbose = 0;
  15 if ($#ARGV >= 0 && $ARGV[0] eq "-v") {
  16     $verbose = 1;
  17     shift;
  18 }
  19
  20 die "Format: ./scripts/sign-file [-v] <key> <x509> <module> [<dest>]\n"
  21     if ($#ARGV != 2 && $#ARGV != 3);
  22
  23 my $private_key = $ARGV[0];
  24 my $x509 = $ARGV[1];
  25 my $module = $ARGV[2];
  26 my $dest = ($#ARGV == 3) ? $ARGV[3] : $ARGV[2] . "~";
  27
  28 die "Can't read private key\n" unless (-r $private_key);
  29 die "Can't read X.509 certificate\n" unless (-r $x509);
  30 die "Can't read module\n" unless (-r $module);
  31
  32 #
  33 # Read the kernel configuration
  34 #
  35 my %config = (
  36     CONFIG_MODULE_SIG_SHA512 => 1
  37     );
  38
  39 if (-r ".config") {
  40     open(FD, "<.config") || die ".config";
  41     while (<FD>) {
  42         if ($_ =~ /^(CONFIG_.*)=[ym]/) {
  43             $config{$1} = 1;
  44         }
  45     }
  46     close(FD);
  47 }
  48
  49 #
  50 # Function to read the contents of a file into a variable.
  51 #
  52 sub read_file($)
  53 {
  54     my ($file) = @_;
  55     my $contents;
  56     my $len;
  57
  58     open(FD, "<$file") || die $file;
  59     binmode FD;
  60     my @st = stat(FD);
  61     die $file if (!@st);
  62     $len = read(FD, $contents, $st[7]) || die $file;
  63     close(FD) || die $file;
  64     die "$file: Wanted length ", $st[7], ", got ", $len, "\n"
  65         if ($len != $st[7]);
  66     return $contents;
  67 }
  68
  69 ###############################################################################
  70 #
  71 # First of all, we have to parse the X.509 certificate to find certain details
  72 # about it.
  73 #
  74 # We read the DER-encoded X509 certificate and parse it to extract the Subject
  75 # name and Subject Key Identifier.  Theis provides the data we need to build
  76 # the certificate identifier.
  77 #
  78 # The signer's name part of the identifier is fabricated from the commonName,
  79 # the organizationName or the emailAddress components of the X.509 subject
  80 # name.
  81 #
  82 # The subject key ID is used to select which of that signer's certificates
  83 # we're intending to use to sign the module.
  84 #
  85 ###############################################################################
  86 my $x509_certificate = read_file($x509);
  87
  88 my $UNIV = 0 << 6;
  89 my $APPL = 1 << 6;
  90 my $CONT = 2 << 6;
  91 my $PRIV = 3 << 6;
  92
  93 my $CONS = 0x20;
  94
  95 my $BOOLEAN     = 0x01;
  96 my $INTEGER     = 0x02;
  97 my $BIT_STRING  = 0x03;
  98 my $OCTET_STRING = 0x04;
  99 my $NULL        = 0x05;
 100 my $OBJ_ID      = 0x06;
 101 my $UTF8String  = 0x0c;
 102 my $SEQUENCE    = 0x10;
 103 my $SET         = 0x11;
 104 my $UTCTime     = 0x17;
 105 my $GeneralizedTime = 0x18;
 106
 107 my %OIDs = (
 108     pack("CCC", 85, 4, 3)       => "commonName",
 109     pack("CCC", 85, 4, 6)       => "countryName",
 110     pack("CCC", 85, 4, 10)      => "organizationName",
 111     pack("CCC", 85, 4, 11)      => "organizationUnitName",
 112     pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 1) => "rsaEncryption",
 113     pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 1, 5) => "sha1WithRSAEncryption",
 114     pack("CCCCCCCCC", 42, 134, 72, 134, 247, 13, 1, 9, 1) => "emailAddress",
 115     pack("CCC", 85, 29, 35)     => "authorityKeyIdentifier",
 116     pack("CCC", 85, 29, 14)     => "subjectKeyIdentifier",
 117     pack("CCC", 85, 29, 19)     => "basicConstraints"
 118 );
 119
 120 ###############################################################################
 121 #
 122 # Extract an ASN.1 element from a string and return information about it.
 123 #
 124 ###############################################################################
 125 sub asn1_extract($$@)
 126 {
 127     my ($cursor, $expected_tag, $optional) = @_;
 128
 129     return [ -1 ]
 130         if ($cursor->[1] == 0 && $optional);
 131
 132     die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (elem ", $cursor->[1], ")\n"
 133         if ($cursor->[1] < 2);
 134
 135     my ($tag, $len) = unpack("CC", substr(${$cursor->[2]}, $cursor->[0], 2));
 136
 137     if ($expected_tag != -1 && $tag != $expected_tag) {
 138         return [ -1 ]
 139             if ($optional);
 140         die $x509, ": ", $cursor->[0], ": ASN.1 unexpected tag (", $tag,
 141         " not ", $expected_tag, ")\n";
 142     }
 143
 144     $cursor->[0] += 2;
 145     $cursor->[1] -= 2;
 146
 147     die $x509, ": ", $cursor->[0], ": ASN.1 long tag\n"
 148         if (($tag & 0x1f) == 0x1f);
 149     die $x509, ": ", $cursor->[0], ": ASN.1 indefinite length\n"
 150         if ($len == 0x80);
 151
 152     if ($len > 0x80) {
 153         my $l = $len - 0x80;
 154         die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (len len $l)\n"
 155             if ($cursor->[1] < $l);
 156
 157         if ($l == 0x1) {
 158             $len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1));
 159         } elsif ($l = 0x2) {
 160             $len = unpack("n", substr(${$cursor->[2]}, $cursor->[0], 2));
 161         } elsif ($l = 0x3) {
 162             $len = unpack("C", substr(${$cursor->[2]}, $cursor->[0], 1)) << 16;
 163             $len = unpack("n", substr(${$cursor->[2]}, $cursor->[0] + 1, 2));
 164         } elsif ($l = 0x4) {
 165             $len = unpack("N", substr(${$cursor->[2]}, $cursor->[0], 4));
 166         } else {
 167             die $x509, ": ", $cursor->[0], ": ASN.1 element too long (", $l, ")\n";
 168         }
 169
 170         $cursor->[0] += $l;
 171         $cursor->[1] -= $l;
 172     }
 173
 174     die $x509, ": ", $cursor->[0], ": ASN.1 data underrun (", $len, ")\n"
 175         if ($cursor->[1] < $len);
 176
 177     my $ret = [ $tag, [ $cursor->[0], $len, $cursor->[2] ] ];
 178     $cursor->[0] += $len;
 179     $cursor->[1] -= $len;
 180
 181     return $ret;
 182 }
 183
 184 ###############################################################################
 185 #
 186 # Retrieve the data referred to by a cursor
 187 #
 188 ###############################################################################
 189 sub asn1_retrieve($)
 190 {
 191     my ($cursor) = @_;
 192     my ($offset, $len, $data) = @$cursor;
 193     return substr($$data, $offset, $len);
 194 }
 195
 196 ###############################################################################
 197 #
 198 # Roughly parse the X.509 certificate
 199 #
 200 ###############################################################################
 201 my $cursor = [ 0, length($x509_certificate), \$x509_certificate ];
 202
 203 my $cert = asn1_extract($cursor, $UNIV | $CONS | $SEQUENCE);
 204 my $tbs = asn1_extract($cert->[1], $UNIV | $CONS | $SEQUENCE);
 205 my $version = asn1_extract($tbs->[1], $CONT | $CONS | 0, 1);
 206 my $serial_number = asn1_extract($tbs->[1], $UNIV | $INTEGER);
 207 my $sig_type = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 208 my $issuer = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 209 my $validity = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 210 my $subject = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 211 my $key = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 212 my $issuer_uid = asn1_extract($tbs->[1], $CONT | $CONS | 1, 1);
 213 my $subject_uid = asn1_extract($tbs->[1], $CONT | $CONS | 2, 1);
 214 my $extension_list = asn1_extract($tbs->[1], $CONT | $CONS | 3, 1);
 215
 216 my $subject_key_id = ();
 217 my $authority_key_id = ();
 218
 219 #
 220 # Parse the extension list
 221 #
 222 if ($extension_list->[0] != -1) {
 223     my $extensions = asn1_extract($extension_list->[1], $UNIV | $CONS | $SEQUENCE);
 224
 225     while ($extensions->[1]->[1] > 0) {
 226         my $ext = asn1_extract($extensions->[1], $UNIV | $CONS | $SEQUENCE);
 227         my $x_oid = asn1_extract($ext->[1], $UNIV | $OBJ_ID);
 228         my $x_crit = asn1_extract($ext->[1], $UNIV | $BOOLEAN, 1);
 229         my $x_val = asn1_extract($ext->[1], $UNIV | $OCTET_STRING);
 230
 231         my $raw_oid = asn1_retrieve($x_oid->[1]);
 232         next if (!exists($OIDs{$raw_oid}));
 233         my $x_type = $OIDs{$raw_oid};
 234
 235         my $raw_value = asn1_retrieve($x_val->[1]);
 236
 237         if ($x_type eq "subjectKeyIdentifier") {
 238             my $vcursor = [ 0, length($raw_value), \$raw_value ];
 239
 240             $subject_key_id = asn1_extract($vcursor, $UNIV | $OCTET_STRING);
 241         }
 242     }
 243 }
 244
 245 ###############################################################################
 246 #
 247 # Determine what we're going to use as the signer's name.  In order of
 248 # preference, take one of: commonName, organizationName or emailAddress.
 249 #
 250 ###############################################################################
 251 my $org = "";
 252 my $cn = "";
 253 my $email = "";
 254
 255 while ($subject->[1]->[1] > 0) {
 256     my $rdn = asn1_extract($subject->[1], $UNIV | $CONS | $SET);
 257     my $attr = asn1_extract($rdn->[1], $UNIV | $CONS | $SEQUENCE);
 258     my $n_oid = asn1_extract($attr->[1], $UNIV | $OBJ_ID);
 259     my $n_val = asn1_extract($attr->[1], -1);
 260
 261     my $raw_oid = asn1_retrieve($n_oid->[1]);
 262     next if (!exists($OIDs{$raw_oid}));
 263     my $n_type = $OIDs{$raw_oid};
 264
 265     my $raw_value = asn1_retrieve($n_val->[1]);
 266
 267     if ($n_type eq "organizationName") {
 268         $org = $raw_value;
 269     } elsif ($n_type eq "commonName") {
 270         $cn = $raw_value;
 271     } elsif ($n_type eq "emailAddress") {
 272         $email = $raw_value;
 273     }
 274 }
 275
 276 my $signers_name = $email;
 277
 278 if ($org && $cn) {
 279     # Don't use the organizationName if the commonName repeats it
 280     if (length($org) <= length($cn) &&
 281         substr($cn, 0, length($org)) eq $org) {
 282         $signers_name = $cn;
 283         goto got_id_name;
 284     }
 285
 286     # Or a signifcant chunk of it
 287     if (length($org) >= 7 &&
 288         length($cn) >= 7 &&
 289         substr($cn, 0, 7) eq substr($org, 0, 7)) {
 290         $signers_name = $cn;
 291         goto got_id_name;
 292     }
 293
 294     $signers_name = $org . ": " . $cn;
 295 } elsif ($org) {
 296     $signers_name = $org;
 297 } elsif ($cn) {
 298     $signers_name = $cn;
 299 }
 300
 301 got_id_name:
 302
 303 die $x509, ": ", "X.509: Couldn't find the Subject Key Identifier extension\n"
 304     if (!$subject_key_id);
 305
 306 my $key_identifier = asn1_retrieve($subject_key_id->[1]);
 307
 308 ###############################################################################
 309 #
 310 # Create and attach the module signature
 311 #
 312 ###############################################################################
 313
 314 #
 315 # Signature parameters
 316 #
 317 my $algo = 1;           # Public-key crypto algorithm: RSA
 318 my $hash = 0;           # Digest algorithm
 319 my $id_type = 1;        # Identifier type: X.509
 320
 321 #
 322 # Digest the data
 323 #
 324 my ($dgst, $prologue) = ();
 325 if (exists $config{"CONFIG_MODULE_SIG_SHA1"}) {
 326     $prologue = pack("C*",
 327                      0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
 328                      0x2B, 0x0E, 0x03, 0x02, 0x1A,
 329                      0x05, 0x00, 0x04, 0x14);
 330     $dgst = "-sha1";
 331     $hash = 2;
 332 } elsif (exists $config{"CONFIG_MODULE_SIG_SHA224"}) {
 333     $prologue = pack("C*",
 334                      0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
 335                      0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
 336                      0x05, 0x00, 0x04, 0x1C);
 337     $dgst = "-sha224";
 338     $hash = 7;
 339 } elsif (exists $config{"CONFIG_MODULE_SIG_SHA256"}) {
 340     $prologue = pack("C*",
 341                      0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
 342                      0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
 343                      0x05, 0x00, 0x04, 0x20);
 344     $dgst = "-sha256";
 345     $hash = 4;
 346 } elsif (exists $config{"CONFIG_MODULE_SIG_SHA384"}) {
 347     $prologue = pack("C*",
 348                      0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
 349                      0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
 350                      0x05, 0x00, 0x04, 0x30);
 351     $dgst = "-sha384";
 352     $hash = 5;
 353 } elsif (exists $config{"CONFIG_MODULE_SIG_SHA512"}) {
 354     $prologue = pack("C*",
 355                      0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
 356                      0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
 357                      0x05, 0x00, 0x04, 0x40);
 358     $dgst = "-sha512";
 359     $hash = 6;
 360 } else {
 361     die "Can't determine hash algorithm";
 362 }
 363
 364 #
 365 # Generate the digest and read from openssl's stdout
 366 #
 367 my $digest;
 368 $digest = readpipe("openssl dgst $dgst -binary $module") || die "openssl dgst";
 369
 370 #
 371 # Generate the binary signature, which will be just the integer that comprises
 372 # the signature with no metadata attached.
 373 #
 374 my $pid;
 375 $pid = open2(*read_from, *write_to,
 376              "openssl rsautl -sign -inkey $private_key -keyform PEM") ||
 377     die "openssl rsautl";
 378 binmode write_to;
 379 print write_to $prologue . $digest || die "pipe to openssl rsautl";
 380 close(write_to) || die "pipe to openssl rsautl";
 381
 382 binmode read_from;
 383 my $signature;
 384 read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
 385 close(read_from) || die "pipe from openssl rsautl";
 386 $signature = pack("n", length($signature)) . $signature,
 387
 388 waitpid($pid, 0) || die;
 389 die "openssl rsautl died: $?" if ($? >> 8);
 390
 391 #
 392 # Build the signed binary
 393 #
 394 my $unsigned_module = read_file($module);
 395
 396 my $magic_number = "~Module signature appended~\n";
 397
 398 my $info = pack("CCCCCxxxN",
 399                 $algo, $hash, $id_type,
 400                 length($signers_name),
 401                 length($key_identifier),
 402                 length($signature));
 403
 404 if ($verbose) {
 405     print "Size of unsigned module: ", length($unsigned_module), "\n";
 406     print "Size of signer's name  : ", length($signers_name), "\n";
 407     print "Size of key identifier : ", length($key_identifier), "\n";
 408     print "Size of signature      : ", length($signature), "\n";
 409     print "Size of informaton     : ", length($info), "\n";
 410     print "Size of magic number   : ", length($magic_number), "\n";
 411     print "Signer's name          : '", $signers_name, "'\n";
 412     print "Digest                 : $dgst\n";
 413 }
 414
 415 open(FD, ">$dest") || die $dest;
 416 binmode FD;
 417 print FD
 418     $unsigned_module,
 419     $signers_name,
 420     $key_identifier,
 421     $signature,
 422     $info,
 423     $magic_number
 424     ;
 425 close FD || die $dest;
 426
 427 if ($#ARGV != 3) {
 428     rename($dest, $module) || die $module;
 429 }