src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c

   1 /*
   2  * Copyright (C) 2005-2009 Martin Willi
   3  * Copyright (C) 2005 Jan Hutter
   4  * Hochschule fuer Technik Rapperswil
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2 of the License, or (at your
   9  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * for more details.
  15  */
  16
  17 #include <gmp.h>
  18 #include <sys/stat.h>
  19 #include <unistd.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22
  23 #include "gmp_rsa_public_key.h"
  24
  25 #include <debug.h>
  26 #include <asn1/oid.h>
  27 #include <asn1/asn1.h>
  28 #include <asn1/asn1_parser.h>
  29 #include <crypto/hashers/hasher.h>
  30
  31 #ifdef HAVE_MPZ_POWM_SEC
  32 # undef mpz_powm
  33 # define mpz_powm mpz_powm_sec
  34 #endif
  35
  36 typedef struct private_gmp_rsa_public_key_t private_gmp_rsa_public_key_t;
  37
  38 /**
  39  * Private data structure with signing context.
  40  */
  41 struct private_gmp_rsa_public_key_t {
  42         /**
  43          * Public interface for this signer.
  44          */
  45         gmp_rsa_public_key_t public;
  46
  47         /**
  48          * Public modulus.
  49          */
  50         mpz_t n;
  51
  52         /**
  53          * Public exponent.
  54          */
  55         mpz_t e;
  56
  57         /**
  58          * Keysize in bytes.
  59          */
  60         size_t k;
  61
  62         /**
  63          * reference counter
  64          */
  65         refcount_t ref;
  66 };
  67
  68 /**
  69  * Shared functions defined in gmp_rsa_private_key.c
  70  */
  71 extern chunk_t gmp_mpz_to_chunk(const mpz_t value);
  72
  73 /**
  74  * RSAEP algorithm specified in PKCS#1.
  75  */
  76 static chunk_t rsaep(private_gmp_rsa_public_key_t *this, chunk_t data)
  77 {
  78         mpz_t m, c;
  79         chunk_t encrypted;
  80
  81         mpz_init(c);
  82         mpz_init(m);
  83
  84         mpz_import(m, data.len, 1, 1, 1, 0, data.ptr);
  85
  86         mpz_powm(c, m, this->e, this->n);
  87
  88         encrypted.len = this->k;
  89         encrypted.ptr = mpz_export(NULL, NULL, 1, encrypted.len, 1, 0, c);
  90         if (encrypted.ptr == NULL)
  91         {
  92                 encrypted.len = 0;
  93         }
  94
  95         mpz_clear(c);
  96         mpz_clear(m);
  97
  98         return encrypted;
  99 }
 100
 101 /**
 102  * RSAVP1 algorithm specified in PKCS#1.
 103  */
 104 static chunk_t rsavp1(private_gmp_rsa_public_key_t *this, chunk_t data)
 105 {
 106         return rsaep(this, data);
 107 }
 108
 109 /**
 110  * ASN.1 definition of digestInfo
 111  */
 112 static const asn1Object_t digestInfoObjects[] = {
 113         { 0, "digestInfo",                      ASN1_SEQUENCE,          ASN1_OBJ  }, /*  0 */
 114         { 1,   "digestAlgorithm",       ASN1_EOC,                       ASN1_RAW  }, /*  1 */
 115         { 1,   "digest",                        ASN1_OCTET_STRING,      ASN1_BODY }, /*  2 */
 116         { 0, "exit",                            ASN1_EOC,                       ASN1_EXIT }
 117 };
 118 #define DIGEST_INFO                                     0
 119 #define DIGEST_INFO_ALGORITHM           1
 120 #define DIGEST_INFO_DIGEST                      2
 121
 122 /**
 123  * Verification of an EMPSA PKCS1 signature described in PKCS#1
 124  */
 125 static bool verify_emsa_pkcs1_signature(private_gmp_rsa_public_key_t *this,
 126                                                                                 hash_algorithm_t algorithm,
 127                                                                                 chunk_t data, chunk_t signature)
 128 {
 129         chunk_t em_ori, em;
 130         bool success = FALSE;
 131
 132         /* remove any preceding 0-bytes from signature */
 133         while (signature.len && *(signature.ptr) == 0x00)
 134         {
 135                 signature = chunk_skip(signature, 1);
 136         }
 137
 138         if (signature.len == 0 || signature.len > this->k)
 139         {
 140                 return INVALID_ARG;
 141         }
 142
 143         /* unpack signature */
 144         em_ori = em = rsavp1(this, signature);
 145
 146         /* result should look like this:
 147          * EM = 0x00 || 0x01 || PS || 0x00 || T.
 148          * PS = 0xFF padding, with length to fill em
 149          * T = oid || hash
 150          */
 151
 152         /* check magic bytes */
 153         if (*(em.ptr) != 0x00 || *(em.ptr+1) != 0x01)
 154         {
 155                 goto end;
 156         }
 157         em = chunk_skip(em, 2);
 158
 159         /* find magic 0x00 */
 160         while (em.len > 0)
 161         {
 162                 if (*em.ptr == 0x00)
 163                 {
 164                         /* found magic byte, stop */
 165                         em = chunk_skip(em, 1);
 166                         break;
 167                 }
 168                 else if (*em.ptr != 0xFF)
 169                 {
 170                         /* bad padding, decryption failed ?!*/
 171                         goto end;
 172                 }
 173                 em = chunk_skip(em, 1);
 174         }
 175
 176         if (em.len == 0)
 177         {
 178                 /* no digestInfo found */
 179                 goto end;
 180         }
 181
 182         if (algorithm == HASH_UNKNOWN)
 183         {   /* IKEv1 signatures without digestInfo */
 184                 if (em.len != data.len)
 185                 {
 186                         DBG1("hash size in signature is %u bytes instead of %u bytes",
 187                                  em.len, data.len);
 188                         goto end;
 189                 }
 190                 success = memeq(em.ptr, data.ptr, data.len);
 191         }
 192         else
 193         {   /* IKEv2 and X.509 certificate signatures */
 194                 asn1_parser_t *parser;
 195                 chunk_t object;
 196                 int objectID;
 197                 hash_algorithm_t hash_algorithm = HASH_UNKNOWN;
 198
 199                 DBG2("signature verification:");
 200                 parser = asn1_parser_create(digestInfoObjects, em);
 201
 202                 while (parser->iterate(parser, &objectID, &object))
 203                 {
 204                         switch (objectID)
 205                         {
 206                                 case DIGEST_INFO:
 207                                 {
 208                                         if (em.len > object.len)
 209                                         {
 210                                                 DBG1("digestInfo field in signature is followed by %u surplus bytes",
 211                                                          em.len - object.len);
 212                                                 goto end_parser;
 213                                         }
 214                                         break;
 215                                 }
 216                                 case DIGEST_INFO_ALGORITHM:
 217                                 {
 218                                         int hash_oid = asn1_parse_algorithmIdentifier(object,
 219                                                                                  parser->get_level(parser)+1, NULL);
 220
 221                                         hash_algorithm = hasher_algorithm_from_oid(hash_oid);
 222                                         if (hash_algorithm == HASH_UNKNOWN || hash_algorithm != algorithm)
 223                                         {
 224                                                 DBG1("expected hash algorithm %N, but found %N (OID: %#B)",
 225                                                          hash_algorithm_names, algorithm,
 226                                                          hash_algorithm_names, hash_algorithm,  &object);
 227                                                 goto end_parser;
 228                                         }
 229                                         break;
 230                                 }
 231                                 case DIGEST_INFO_DIGEST:
 232                                 {
 233                                         chunk_t hash;
 234                                         hasher_t *hasher;
 235
 236                                         hasher = lib->crypto->create_hasher(lib->crypto, hash_algorithm);
 237                                         if (hasher == NULL)
 238                                         {
 239                                                 DBG1("hash algorithm %N not supported",
 240                                                          hash_algorithm_names, hash_algorithm);
 241                                                 goto end_parser;
 242                                         }
 243
 244                                         if (object.len != hasher->get_hash_size(hasher))
 245                                         {
 246                                                 DBG1("hash size in signature is %u bytes instead of %u "
 247                                                          "bytes", object.len, hasher->get_hash_size(hasher));
 248                                                 hasher->destroy(hasher);
 249                                                 goto end_parser;
 250                                         }
 251
 252                                         /* build our own hash and compare */
 253                                         hasher->allocate_hash(hasher, data, &hash);
 254                                         hasher->destroy(hasher);
 255                                         success = memeq(object.ptr, hash.ptr, hash.len);
 256                                         free(hash.ptr);
 257                                         break;
 258                                 }
 259                                 default:
 260                                         break;
 261                         }
 262                 }
 263
 264 end_parser:
 265                 success &= parser->success(parser);
 266                 parser->destroy(parser);
 267         }
 268
 269 end:
 270         free(em_ori.ptr);
 271         return success;
 272 }
 273
 274 /**
 275  * Implementation of public_key_t.get_type.
 276  */
 277 static key_type_t get_type(private_gmp_rsa_public_key_t *this)
 278 {
 279         return KEY_RSA;
 280 }
 281
 282 /**
 283  * Implementation of public_key_t.verify.
 284  */
 285 static bool verify(private_gmp_rsa_public_key_t *this, signature_scheme_t scheme,
 286                                    chunk_t data, chunk_t signature)
 287 {
 288         switch (scheme)
 289         {
 290                 case SIGN_RSA_EMSA_PKCS1_NULL:
 291                         return verify_emsa_pkcs1_signature(this, HASH_UNKNOWN, data, signature);
 292                 case SIGN_RSA_EMSA_PKCS1_MD5:
 293                         return verify_emsa_pkcs1_signature(this, HASH_MD5, data, signature);
 294                 case SIGN_RSA_EMSA_PKCS1_SHA1:
 295                         return verify_emsa_pkcs1_signature(this, HASH_SHA1, data, signature);
 296                 case SIGN_RSA_EMSA_PKCS1_SHA224:
 297                         return verify_emsa_pkcs1_signature(this, HASH_SHA224, data, signature);
 298                 case SIGN_RSA_EMSA_PKCS1_SHA256:
 299                         return verify_emsa_pkcs1_signature(this, HASH_SHA256, data, signature);
 300                 case SIGN_RSA_EMSA_PKCS1_SHA384:
 301                         return verify_emsa_pkcs1_signature(this, HASH_SHA384, data, signature);
 302                 case SIGN_RSA_EMSA_PKCS1_SHA512:
 303                         return verify_emsa_pkcs1_signature(this, HASH_SHA512, data, signature);
 304                 default:
 305                         DBG1("signature scheme %N not supported in RSA",
 306                                  signature_scheme_names, scheme);
 307                         return FALSE;
 308         }
 309 }
 310
 311 #define MIN_PS_PADDING 8
 312
 313 /**
 314  * Implementation of public_key_t.encrypt.
 315  */
 316 static bool encrypt_(private_gmp_rsa_public_key_t *this, chunk_t plain,
 317                                          chunk_t *crypto)
 318 {
 319         chunk_t em;
 320         u_char *pos;
 321         int padding, i;
 322         rng_t *rng;
 323
 324         rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
 325         if (rng == NULL)
 326         {
 327                 DBG1("no random generator available");
 328                 return FALSE;
 329         }
 330
 331         /* number of pseudo-random padding octets */
 332         padding = this->k - plain.len - 3;
 333         if (padding < MIN_PS_PADDING)
 334         {
 335                 DBG1("pseudo-random padding must be at least %d octets", MIN_PS_PADDING);
 336                 return FALSE;
 337         }
 338
 339         /* padding according to PKCS#1 7.2.1 (RSAES-PKCS1-v1.5-ENCRYPT) */
 340         DBG2("padding %u bytes of data to the rsa modulus size of %u bytes",
 341                  plain.len, this->k);
 342         em.len = this->k;
 343         em.ptr = malloc(em.len);
 344         pos = em.ptr;
 345         *pos++ = 0x00;
 346         *pos++ = 0x02;
 347
 348         /* fill with pseudo random octets */
 349         rng->get_bytes(rng, padding, pos);
 350
 351         /* replace zero-valued random octets */
 352         for (i = 0; i < padding; i++)
 353         {
 354                 while (*pos == 0)
 355                 {
 356                         rng->get_bytes(rng, 1, pos);
 357                 }
 358                 pos++;
 359         }
 360         rng->destroy(rng);
 361
 362         /* append the padding terminator */
 363         *pos++ = 0x00;
 364
 365         /* now add the data */
 366         memcpy(pos, plain.ptr, plain.len);
 367         DBG3("padded data before rsa encryption: %B", &em);
 368
 369         /* rsa encryption using PKCS#1 RSAEP */
 370         *crypto = rsaep(this, em);
 371         DBG3("rsa encrypted data: %B", crypto);
 372         chunk_clear(&em);
 373         return TRUE;
 374 }
 375
 376 /**
 377  * Implementation of gmp_rsa_public_key.equals.
 378  */
 379 static bool equals(private_gmp_rsa_public_key_t *this, public_key_t *other)
 380 {
 381         return public_key_equals(&this->public.interface, other);
 382 }
 383
 384 /**
 385  * Implementation of public_key_t.get_keysize.
 386  */
 387 static size_t get_keysize(private_gmp_rsa_public_key_t *this)
 388 {
 389         return this->k;
 390 }
 391
 392 /**
 393  * Implementation of public_key_t.get_encoding
 394  */
 395 static bool get_encoding(private_gmp_rsa_public_key_t *this,
 396                                                  key_encoding_type_t type, chunk_t *encoding)
 397 {
 398         chunk_t n, e;
 399         bool success;
 400
 401         n = gmp_mpz_to_chunk(this->n);
 402         e = gmp_mpz_to_chunk(this->e);
 403
 404         success = lib->encoding->encode(lib->encoding, type, NULL, encoding,
 405                                 KEY_PART_RSA_MODULUS, n, KEY_PART_RSA_PUB_EXP, e, KEY_PART_END);
 406         chunk_free(&n);
 407         chunk_free(&e);
 408
 409         return success;
 410 }
 411
 412 /**
 413  * Implementation of public_key_t.get_fingerprint
 414  */
 415 static bool get_fingerprint(private_gmp_rsa_public_key_t *this,
 416                                                         key_encoding_type_t type, chunk_t *fp)
 417 {
 418         chunk_t n, e;
 419         bool success;
 420
 421         if (lib->encoding->get_cache(lib->encoding, type, this, fp))
 422         {
 423                 return TRUE;
 424         }
 425         n = gmp_mpz_to_chunk(this->n);
 426         e = gmp_mpz_to_chunk(this->e);
 427
 428         success = lib->encoding->encode(lib->encoding, type, this, fp,
 429                                 KEY_PART_RSA_MODULUS, n, KEY_PART_RSA_PUB_EXP, e, KEY_PART_END);
 430         chunk_free(&n);
 431         chunk_free(&e);
 432
 433         return success;
 434 }
 435
 436 /**
 437  * Implementation of public_key_t.get_ref.
 438  */
 439 static private_gmp_rsa_public_key_t* get_ref(private_gmp_rsa_public_key_t *this)
 440 {
 441         ref_get(&this->ref);
 442         return this;
 443 }
 444
 445 /**
 446  * Implementation of gmp_rsa_public_key.destroy.
 447  */
 448 static void destroy(private_gmp_rsa_public_key_t *this)
 449 {
 450         if (ref_put(&this->ref))
 451         {
 452                 mpz_clear(this->n);
 453                 mpz_clear(this->e);
 454                 lib->encoding->clear_cache(lib->encoding, this);
 455                 free(this);
 456         }
 457 }
 458
 459 /**
 460  * See header.
 461  */
 462 gmp_rsa_public_key_t *gmp_rsa_public_key_load(key_type_t type, va_list args)
 463 {
 464         private_gmp_rsa_public_key_t *this;
 465         chunk_t n, e;
 466
 467         n = e = chunk_empty;
 468         while (TRUE)
 469         {
 470                 switch (va_arg(args, builder_part_t))
 471                 {
 472                         case BUILD_RSA_MODULUS:
 473                                 n = va_arg(args, chunk_t);
 474                                 continue;
 475                         case BUILD_RSA_PUB_EXP:
 476                                 e = va_arg(args, chunk_t);
 477                                 continue;
 478                         case BUILD_END:
 479                                 break;
 480                         default:
 481                                 return NULL;
 482                 }
 483                 break;
 484         }
 485         if (!e.ptr || !n.ptr)
 486         {
 487                 return NULL;
 488         }
 489
 490         this = malloc_thing(private_gmp_rsa_public_key_t);
 491
 492         this->public.interface.get_type = (key_type_t (*) (public_key_t*))get_type;
 493         this->public.interface.verify = (bool (*) (public_key_t*, signature_scheme_t, chunk_t, chunk_t))verify;
 494         this->public.interface.encrypt = (bool (*) (public_key_t*, chunk_t, chunk_t*))encrypt_;
 495         this->public.interface.equals = (bool (*) (public_key_t*, public_key_t*))equals;
 496         this->public.interface.get_keysize = (size_t (*) (public_key_t*))get_keysize;
 497         this->public.interface.get_fingerprint = (bool(*)(public_key_t*, key_encoding_type_t type, chunk_t *fp))get_fingerprint;
 498         this->public.interface.has_fingerprint = (bool(*)(public_key_t*, chunk_t fp))public_key_has_fingerprint;
 499         this->public.interface.get_encoding = (bool(*)(public_key_t*, key_encoding_type_t type, chunk_t *encoding))get_encoding;
 500         this->public.interface.get_ref = (public_key_t* (*) (public_key_t *this))get_ref;
 501         this->public.interface.destroy = (void (*) (public_key_t *this))destroy;
 502
 503         this->ref = 1;
 504
 505         mpz_init(this->n);
 506         mpz_init(this->e);
 507
 508         mpz_import(this->n, n.len, 1, 1, 1, 0, n.ptr);
 509         mpz_import(this->e, e.len, 1, 1, 1, 0, e.ptr);
 510
 511         this->k = (mpz_sizeinbase(this->n, 2) + 7) / BITS_PER_BYTE;
 512
 513         return &this->public;
 514 }
 515