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 FALSE;
 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(DBG_LIB, "hash size in signature is %u bytes instead of"
 187                                  " %u bytes", 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(DBG_LIB, "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(DBG_LIB, "digestInfo field in signature is"
 211                                                          " followed by %u surplus bytes",
 212                                                          em.len - object.len);
 213                                                 goto end_parser;
 214                                         }
 215                                         break;
 216                                 }
 217                                 case DIGEST_INFO_ALGORITHM:
 218                                 {
 219                                         int hash_oid = asn1_parse_algorithmIdentifier(object,
 220                                                                                  parser->get_level(parser)+1, NULL);
 221
 222                                         hash_algorithm = hasher_algorithm_from_oid(hash_oid);
 223                                         if (hash_algorithm == HASH_UNKNOWN || hash_algorithm != algorithm)
 224                                         {
 225                                                 DBG1(DBG_LIB, "expected hash algorithm %N, but found"
 226                                                          " %N (OID: %#B)", hash_algorithm_names, algorithm,
 227                                                          hash_algorithm_names, hash_algorithm,  &object);
 228                                                 goto end_parser;
 229                                         }
 230                                         break;
 231                                 }
 232                                 case DIGEST_INFO_DIGEST:
 233                                 {
 234                                         chunk_t hash;
 235                                         hasher_t *hasher;
 236
 237                                         hasher = lib->crypto->create_hasher(lib->crypto, hash_algorithm);
 238                                         if (hasher == NULL)
 239                                         {
 240                                                 DBG1(DBG_LIB, "hash algorithm %N not supported",
 241                                                          hash_algorithm_names, hash_algorithm);
 242                                                 goto end_parser;
 243                                         }
 244
 245                                         if (object.len != hasher->get_hash_size(hasher))
 246                                         {
 247                                                 DBG1(DBG_LIB, "hash size in signature is %u bytes"
 248                                                          " instead of %u bytes", object.len,
 249                                                          hasher->get_hash_size(hasher));
 250                                                 hasher->destroy(hasher);
 251                                                 goto end_parser;
 252                                         }
 253
 254                                         /* build our own hash and compare */
 255                                         if (!hasher->allocate_hash(hasher, data, &hash))
 256                                         {
 257                                                 hasher->destroy(hasher);
 258                                                 goto end_parser;
 259                                         }
 260                                         hasher->destroy(hasher);
 261                                         success = memeq(object.ptr, hash.ptr, hash.len);
 262                                         free(hash.ptr);
 263                                         break;
 264                                 }
 265                                 default:
 266                                         break;
 267                         }
 268                 }
 269
 270 end_parser:
 271                 success &= parser->success(parser);
 272                 parser->destroy(parser);
 273         }
 274
 275 end:
 276         free(em_ori.ptr);
 277         return success;
 278 }
 279
 280 METHOD(public_key_t, get_type, key_type_t,
 281         private_gmp_rsa_public_key_t *this)
 282 {
 283         return KEY_RSA;
 284 }
 285
 286 METHOD(public_key_t, verify, bool,
 287         private_gmp_rsa_public_key_t *this, signature_scheme_t scheme,
 288         chunk_t data, chunk_t signature)
 289 {
 290         switch (scheme)
 291         {
 292                 case SIGN_RSA_EMSA_PKCS1_NULL:
 293                         return verify_emsa_pkcs1_signature(this, HASH_UNKNOWN, data, signature);
 294                 case SIGN_RSA_EMSA_PKCS1_MD5:
 295                         return verify_emsa_pkcs1_signature(this, HASH_MD5, data, signature);
 296                 case SIGN_RSA_EMSA_PKCS1_SHA1:
 297                         return verify_emsa_pkcs1_signature(this, HASH_SHA1, data, signature);
 298                 case SIGN_RSA_EMSA_PKCS1_SHA224:
 299                         return verify_emsa_pkcs1_signature(this, HASH_SHA224, data, signature);
 300                 case SIGN_RSA_EMSA_PKCS1_SHA256:
 301                         return verify_emsa_pkcs1_signature(this, HASH_SHA256, data, signature);
 302                 case SIGN_RSA_EMSA_PKCS1_SHA384:
 303                         return verify_emsa_pkcs1_signature(this, HASH_SHA384, data, signature);
 304                 case SIGN_RSA_EMSA_PKCS1_SHA512:
 305                         return verify_emsa_pkcs1_signature(this, HASH_SHA512, data, signature);
 306                 default:
 307                         DBG1(DBG_LIB, "signature scheme %N not supported in RSA",
 308                                  signature_scheme_names, scheme);
 309                         return FALSE;
 310         }
 311 }
 312
 313 #define MIN_PS_PADDING 8
 314
 315 METHOD(public_key_t, encrypt_, bool,
 316         private_gmp_rsa_public_key_t *this, encryption_scheme_t scheme,
 317         chunk_t plain, chunk_t *crypto)
 318 {
 319         chunk_t em;
 320         u_char *pos;
 321         int padding;
 322         rng_t *rng;
 323
 324         if (scheme != ENCRYPT_RSA_PKCS1)
 325         {
 326                 DBG1(DBG_LIB, "encryption scheme %N not supported",
 327                          encryption_scheme_names, scheme);
 328                 return FALSE;
 329         }
 330         /* number of pseudo-random padding octets */
 331         padding = this->k - plain.len - 3;
 332         if (padding < MIN_PS_PADDING)
 333         {
 334                 DBG1(DBG_LIB, "pseudo-random padding must be at least %d octets",
 335                          MIN_PS_PADDING);
 336                 return FALSE;
 337         }
 338         rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
 339         if (rng == NULL)
 340         {
 341                 DBG1(DBG_LIB, "no random generator available");
 342                 return FALSE;
 343         }
 344
 345         /* padding according to PKCS#1 7.2.1 (RSAES-PKCS1-v1.5-ENCRYPT) */
 346         DBG2(DBG_LIB, "padding %u bytes of data to the rsa modulus size of"
 347                  " %u bytes", plain.len, this->k);
 348         em.len = this->k;
 349         em.ptr = malloc(em.len);
 350         pos = em.ptr;
 351         *pos++ = 0x00;
 352         *pos++ = 0x02;
 353
 354         /* fill with pseudo random octets */
 355         if (!rng_get_bytes_not_zero(rng, padding, pos, TRUE))
 356         {
 357                 DBG1(DBG_LIB, "failed to allocate padding");
 358                 chunk_clear(&em);
 359                 rng->destroy(rng);
 360                 return FALSE;
 361         }
 362         rng->destroy(rng);
 363
 364         /* append the padding terminator */
 365         *pos++ = 0x00;
 366
 367         /* now add the data */
 368         memcpy(pos, plain.ptr, plain.len);
 369         DBG3(DBG_LIB, "padded data before rsa encryption: %B", &em);
 370
 371         /* rsa encryption using PKCS#1 RSAEP */
 372         *crypto = rsaep(this, em);
 373         DBG3(DBG_LIB, "rsa encrypted data: %B", crypto);
 374         chunk_clear(&em);
 375         return TRUE;
 376 }
 377
 378 METHOD(public_key_t, get_keysize, int,
 379         private_gmp_rsa_public_key_t *this)
 380 {
 381         return mpz_sizeinbase(this->n, 2);
 382 }
 383
 384 METHOD(public_key_t, get_encoding, bool,
 385         private_gmp_rsa_public_key_t *this, cred_encoding_type_t type,
 386         chunk_t *encoding)
 387 {
 388         chunk_t n, e;
 389         bool success;
 390
 391         n = gmp_mpz_to_chunk(this->n);
 392         e = gmp_mpz_to_chunk(this->e);
 393
 394         success = lib->encoding->encode(lib->encoding, type, NULL, encoding,
 395                         CRED_PART_RSA_MODULUS, n, CRED_PART_RSA_PUB_EXP, e, CRED_PART_END);
 396         chunk_free(&n);
 397         chunk_free(&e);
 398
 399         return success;
 400 }
 401
 402 METHOD(public_key_t, get_fingerprint, bool,
 403         private_gmp_rsa_public_key_t *this, cred_encoding_type_t type, chunk_t *fp)
 404 {
 405         chunk_t n, e;
 406         bool success;
 407
 408         if (lib->encoding->get_cache(lib->encoding, type, this, fp))
 409         {
 410                 return TRUE;
 411         }
 412         n = gmp_mpz_to_chunk(this->n);
 413         e = gmp_mpz_to_chunk(this->e);
 414
 415         success = lib->encoding->encode(lib->encoding, type, this, fp,
 416                         CRED_PART_RSA_MODULUS, n, CRED_PART_RSA_PUB_EXP, e, CRED_PART_END);
 417         chunk_free(&n);
 418         chunk_free(&e);
 419
 420         return success;
 421 }
 422
 423 METHOD(public_key_t, get_ref, public_key_t*,
 424         private_gmp_rsa_public_key_t *this)
 425 {
 426         ref_get(&this->ref);
 427         return &this->public.key;
 428 }
 429
 430 METHOD(public_key_t, destroy, void,
 431         private_gmp_rsa_public_key_t *this)
 432 {
 433         if (ref_put(&this->ref))
 434         {
 435                 mpz_clear(this->n);
 436                 mpz_clear(this->e);
 437                 lib->encoding->clear_cache(lib->encoding, this);
 438                 free(this);
 439         }
 440 }
 441
 442 /**
 443  * See header.
 444  */
 445 gmp_rsa_public_key_t *gmp_rsa_public_key_load(key_type_t type, va_list args)
 446 {
 447         private_gmp_rsa_public_key_t *this;
 448         chunk_t n, e;
 449
 450         n = e = chunk_empty;
 451         while (TRUE)
 452         {
 453                 switch (va_arg(args, builder_part_t))
 454                 {
 455                         case BUILD_RSA_MODULUS:
 456                                 n = va_arg(args, chunk_t);
 457                                 continue;
 458                         case BUILD_RSA_PUB_EXP:
 459                                 e = va_arg(args, chunk_t);
 460                                 continue;
 461                         case BUILD_END:
 462                                 break;
 463                         default:
 464                                 return NULL;
 465                 }
 466                 break;
 467         }
 468         if (!e.ptr || !n.ptr)
 469         {
 470                 return NULL;
 471         }
 472
 473         INIT(this,
 474                 .public = {
 475                         .key = {
 476                                 .get_type = _get_type,
 477                                 .verify = _verify,
 478                                 .encrypt = _encrypt_,
 479                                 .equals = public_key_equals,
 480                                 .get_keysize = _get_keysize,
 481                                 .get_fingerprint = _get_fingerprint,
 482                                 .has_fingerprint = public_key_has_fingerprint,
 483                                 .get_encoding = _get_encoding,
 484                                 .get_ref = _get_ref,
 485                                 .destroy = _destroy,
 486                         },
 487                 },
 488                 .ref = 1,
 489         );
 490
 491         mpz_init(this->n);
 492         mpz_init(this->e);
 493
 494         mpz_import(this->n, n.len, 1, 1, 1, 0, n.ptr);
 495         mpz_import(this->e, e.len, 1, 1, 1, 0, e.ptr);
 496
 497         this->k = (mpz_sizeinbase(this->n, 2) + 7) / BITS_PER_BYTE;
 498
 499         return &this->public;
 500 }
 501