linux/scripts/sign-file
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   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#
  10use strict;
  11use FileHandle;
  12use IPC::Open2;
  13
  14my $verbose = 0;
  15if ($#ARGV >= 0 && $ARGV[0] eq "-v") {
  16    $verbose = 1;
  17    shift;
  18}
  19
  20die "Format: ./scripts/sign-file [-v] <key> <x509> <module> [<dest>]\n"
  21    if ($#ARGV != 2 && $#ARGV != 3);
  22
  23my $private_key = $ARGV[0];
  24my $x509 = $ARGV[1];
  25my $module = $ARGV[2];
  26my $dest = ($#ARGV == 3) ? $ARGV[3] : $ARGV[2] . "~";
  27
  28die "Can't read private key\n" unless (-r $private_key);
  29die "Can't read X.509 certificate\n" unless (-r $x509);
  30die "Can't read module\n" unless (-r $module);
  31
  32#
  33# Read the kernel configuration
  34#
  35my %config = (
  36    CONFIG_MODULE_SIG_SHA512 => 1
  37    );
  38
  39if (-r ".config") {
  40    open(FD, "<.config") || die ".config";
  41    while (<FD>) {
  42        if ($_ =~ /^(CONFIG_.*)=[ym]/) {
  43            $config{$1} = 1;
  44        }
  45    }
  46    close(FD);
  47}
  48
  49#
  50# Function to read the contents of a file into a variable.
  51#
  52sub read_file($)
  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###############################################################################
  86my $x509_certificate = read_file($x509);
  87
  88my $UNIV = 0 << 6;
  89my $APPL = 1 << 6;
  90my $CONT = 2 << 6;
  91my $PRIV = 3 << 6;
  92
  93my $CONS = 0x20;
  94
  95my $BOOLEAN     = 0x01;
  96my $INTEGER     = 0x02;
  97my $BIT_STRING  = 0x03;
  98my $OCTET_STRING = 0x04;
  99my $NULL        = 0x05;
 100my $OBJ_ID      = 0x06;
 101my $UTF8String  = 0x0c;
 102my $SEQUENCE    = 0x10;
 103my $SET         = 0x11;
 104my $UTCTime     = 0x17;
 105my $GeneralizedTime = 0x18;
 106
 107my %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###############################################################################
 125sub 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###############################################################################
 189sub 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###############################################################################
 201my $cursor = [ 0, length($x509_certificate), \$x509_certificate ];
 202
 203my $cert = asn1_extract($cursor, $UNIV | $CONS | $SEQUENCE);
 204my $tbs = asn1_extract($cert->[1], $UNIV | $CONS | $SEQUENCE);
 205my $version = asn1_extract($tbs->[1], $CONT | $CONS | 0, 1);
 206my $serial_number = asn1_extract($tbs->[1], $UNIV | $INTEGER);
 207my $sig_type = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 208my $issuer = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 209my $validity = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 210my $subject = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 211my $key = asn1_extract($tbs->[1], $UNIV | $CONS | $SEQUENCE);
 212my $issuer_uid = asn1_extract($tbs->[1], $CONT | $CONS | 1, 1);
 213my $subject_uid = asn1_extract($tbs->[1], $CONT | $CONS | 2, 1);
 214my $extension_list = asn1_extract($tbs->[1], $CONT | $CONS | 3, 1);
 215
 216my $subject_key_id = ();
 217my $authority_key_id = ();
 218
 219#
 220# Parse the extension list
 221#
 222if ($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###############################################################################
 251my $org = "";
 252my $cn = "";
 253my $email = "";
 254
 255while ($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
 276my $signers_name = $email;
 277
 278if ($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
 301got_id_name:
 302
 303die $x509, ": ", "X.509: Couldn't find the Subject Key Identifier extension\n"
 304    if (!$subject_key_id);
 305
 306my $key_identifier = asn1_retrieve($subject_key_id->[1]);
 307
 308###############################################################################
 309#
 310# Create and attach the module signature
 311#
 312###############################################################################
 313
 314#
 315# Signature parameters
 316#
 317my $algo = 1;           # Public-key crypto algorithm: RSA
 318my $hash = 0;           # Digest algorithm
 319my $id_type = 1;        # Identifier type: X.509
 320
 321#
 322# Digest the data
 323#
 324my ($dgst, $prologue) = ();
 325if (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#
 367my $digest;
 368$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#
 374my $pid;
 375$pid = open2(*read_from, *write_to,
 376             "openssl rsautl -sign -inkey $private_key -keyform PEM") ||
 377    die "openssl rsautl";
 378binmode write_to;
 379print write_to $prologue . $digest || die "pipe to openssl rsautl";
 380close(write_to) || die "pipe to openssl rsautl";
 381
 382binmode read_from;
 383my $signature;
 384read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
 385close(read_from) || die "pipe from openssl rsautl";
 386$signature = pack("n", length($signature)) . $signature,
 387
 388waitpid($pid, 0) || die;
 389die "openssl rsautl died: $?" if ($? >> 8);
 390
 391#
 392# Build the signed binary
 393#
 394my $unsigned_module = read_file($module);
 395
 396my $magic_number = "~Module signature appended~\n";
 397
 398my $info = pack("CCCCCxxxN",
 399                $algo, $hash, $id_type,
 400                length($signers_name),
 401                length($key_identifier),
 402                length($signature));
 403
 404if ($verbose) {
 405    print "Size of unsigned module: ", length($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                 : $dgst\n";
 413}
 414
 415open(FD, ">$dest") || die $dest;
 416binmode FD;
 417print FD
 418    $unsigned_module,
 419    $signers_name,
 420    $key_identifier,
 421    $signature,
 422    $info,
 423    $magic_number
 424    ;
 425close FD || die $dest;
 426
 427if ($#ARGV != 3) {
 428    rename($dest, $module) || die $module;
 429}
 430
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