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 <utils/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(m);
  82         mpz_import(m, data.len, 1, 1, 1, 0, data.ptr);
  83
  84         if (mpz_cmp_ui(m, 0) <= 0 || mpz_cmp(m, this->n) >= 0)
  85         {       /* m must be <= n-1, and while 0 is technically a valid value, it
  86                  * doesn't really make sense here, so we filter that too */
  87                 mpz_clear(m);
  88                 return chunk_empty;
  89         }
  90
  91         mpz_init(c);
  92         mpz_powm(c, m, this->e, this->n);
  93
  94         encrypted.len = this->k;
  95         encrypted.ptr = mpz_export(NULL, NULL, 1, encrypted.len, 1, 0, c);
  96         if (encrypted.ptr == NULL)
  97         {
  98                 encrypted.len = 0;
  99         }
 100
 101         mpz_clear(c);
 102         mpz_clear(m);
 103
 104         return encrypted;
 105 }
 106
 107 /**
 108  * RSAVP1 algorithm specified in PKCS#1.
 109  */
 110 static chunk_t rsavp1(private_gmp_rsa_public_key_t *this, chunk_t data)
 111 {
 112         return rsaep(this, data);
 113 }
 114
 115 /**
 116  * ASN.1 definition of digestInfo
 117  */
 118 static const asn1Object_t digestInfoObjects[] = {
 119         { 0, "digestInfo",                      ASN1_SEQUENCE,          ASN1_OBJ  }, /*  0 */
 120         { 1,   "digestAlgorithm",       ASN1_EOC,                       ASN1_RAW  }, /*  1 */
 121         { 1,   "digest",                        ASN1_OCTET_STRING,      ASN1_BODY }, /*  2 */
 122         { 0, "exit",                            ASN1_EOC,                       ASN1_EXIT }
 123 };
 124 #define DIGEST_INFO                                     0
 125 #define DIGEST_INFO_ALGORITHM           1
 126 #define DIGEST_INFO_DIGEST                      2
 127
 128 /**
 129  * Verification of an EMPSA PKCS1 signature described in PKCS#1
 130  */
 131 static bool verify_emsa_pkcs1_signature(private_gmp_rsa_public_key_t *this,
 132                                                                                 hash_algorithm_t algorithm,
 133                                                                                 chunk_t data, chunk_t signature)
 134 {
 135         chunk_t em_ori, em;
 136         bool success = FALSE;
 137
 138         /* remove any preceding 0-bytes from signature */
 139         while (signature.len && *(signature.ptr) == 0x00)
 140         {
 141                 signature = chunk_skip(signature, 1);
 142         }
 143
 144         if (signature.len == 0 || signature.len > this->k)
 145         {
 146                 return FALSE;
 147         }
 148
 149         /* unpack signature */
 150         em_ori = em = rsavp1(this, signature);
 151
 152         /* result should look like this:
 153          * EM = 0x00 || 0x01 || PS || 0x00 || T.
 154          * PS = 0xFF padding, with length to fill em
 155          * T = oid || hash
 156          */
 157
 158         /* check magic bytes */
 159         if (em.len < 2 || *(em.ptr) != 0x00 || *(em.ptr+1) != 0x01)
 160         {
 161                 goto end;
 162         }
 163         em = chunk_skip(em, 2);
 164
 165         /* find magic 0x00 */
 166         while (em.len > 0)
 167         {
 168                 if (*em.ptr == 0x00)
 169                 {
 170                         /* found magic byte, stop */
 171                         em = chunk_skip(em, 1);
 172                         break;
 173                 }
 174                 else if (*em.ptr != 0xFF)
 175                 {
 176                         /* bad padding, decryption failed ?!*/
 177                         goto end;
 178                 }
 179                 em = chunk_skip(em, 1);
 180         }
 181
 182         if (em.len == 0)
 183         {
 184                 /* no digestInfo found */
 185                 goto end;
 186         }
 187
 188         if (algorithm == HASH_UNKNOWN)
 189         {   /* IKEv1 signatures without digestInfo */
 190                 if (em.len != data.len)
 191                 {
 192                         DBG1(DBG_LIB, "hash size in signature is %u bytes instead of"
 193                                  " %u bytes", em.len, data.len);
 194                         goto end;
 195                 }
 196                 success = memeq_const(em.ptr, data.ptr, data.len);
 197         }
 198         else
 199         {   /* IKEv2 and X.509 certificate signatures */
 200                 asn1_parser_t *parser;
 201                 chunk_t object;
 202                 int objectID;
 203                 hash_algorithm_t hash_algorithm = HASH_UNKNOWN;
 204
 205                 DBG2(DBG_LIB, "signature verification:");
 206                 parser = asn1_parser_create(digestInfoObjects, em);
 207
 208                 while (parser->iterate(parser, &objectID, &object))
 209                 {
 210                         switch (objectID)
 211                         {
 212                                 case DIGEST_INFO:
 213                                 {
 214                                         if (em.len > object.len)
 215                                         {
 216                                                 DBG1(DBG_LIB, "digestInfo field in signature is"
 217                                                          " followed by %u surplus bytes",
 218                                                          em.len - object.len);
 219                                                 goto end_parser;
 220                                         }
 221                                         break;
 222                                 }
 223                                 case DIGEST_INFO_ALGORITHM:
 224                                 {
 225                                         int hash_oid = asn1_parse_algorithmIdentifier(object,
 226                                                                                  parser->get_level(parser)+1, NULL);
 227
 228                                         hash_algorithm = hasher_algorithm_from_oid(hash_oid);
 229                                         if (hash_algorithm == HASH_UNKNOWN || hash_algorithm != algorithm)
 230                                         {
 231                                                 DBG1(DBG_LIB, "expected hash algorithm %N, but found"
 232                                                          " %N (OID: %#B)", hash_algorithm_names, algorithm,
 233                                                          hash_algorithm_names, hash_algorithm,  &object);
 234                                                 goto end_parser;
 235                                         }
 236                                         break;
 237                                 }
 238                                 case DIGEST_INFO_DIGEST:
 239                                 {
 240                                         chunk_t hash;
 241                                         hasher_t *hasher;
 242
 243                                         hasher = lib->crypto->create_hasher(lib->crypto, hash_algorithm);
 244                                         if (hasher == NULL)
 245                                         {
 246                                                 DBG1(DBG_LIB, "hash algorithm %N not supported",
 247                                                          hash_algorithm_names, hash_algorithm);
 248                                                 goto end_parser;
 249                                         }
 250
 251                                         if (object.len != hasher->get_hash_size(hasher))
 252                                         {
 253                                                 DBG1(DBG_LIB, "hash size in signature is %u bytes"
 254                                                          " instead of %u bytes", object.len,
 255                                                          hasher->get_hash_size(hasher));
 256                                                 hasher->destroy(hasher);
 257                                                 goto end_parser;
 258                                         }
 259
 260                                         /* build our own hash and compare */
 261                                         if (!hasher->allocate_hash(hasher, data, &hash))
 262                                         {
 263                                                 hasher->destroy(hasher);
 264                                                 goto end_parser;
 265                                         }
 266                                         hasher->destroy(hasher);
 267                                         success = memeq_const(object.ptr, hash.ptr, hash.len);
 268                                         free(hash.ptr);
 269                                         break;
 270                                 }
 271                                 default:
 272                                         break;
 273                         }
 274                 }
 275
 276 end_parser:
 277                 success &= parser->success(parser);
 278                 parser->destroy(parser);
 279         }
 280
 281 end:
 282         free(em_ori.ptr);
 283         return success;
 284 }
 285
 286 METHOD(public_key_t, get_type, key_type_t,
 287         private_gmp_rsa_public_key_t *this)
 288 {
 289         return KEY_RSA;
 290 }
 291
 292 METHOD(public_key_t, verify, bool,
 293         private_gmp_rsa_public_key_t *this, signature_scheme_t scheme,
 294         chunk_t data, chunk_t signature)
 295 {
 296         switch (scheme)
 297         {
 298                 case SIGN_RSA_EMSA_PKCS1_NULL:
 299                         return verify_emsa_pkcs1_signature(this, HASH_UNKNOWN, data, signature);
 300                 case SIGN_RSA_EMSA_PKCS1_SHA2_224:
 301                         return verify_emsa_pkcs1_signature(this, HASH_SHA224, data, signature);
 302                 case SIGN_RSA_EMSA_PKCS1_SHA2_256:
 303                         return verify_emsa_pkcs1_signature(this, HASH_SHA256, data, signature);
 304                 case SIGN_RSA_EMSA_PKCS1_SHA2_384:
 305                         return verify_emsa_pkcs1_signature(this, HASH_SHA384, data, signature);
 306                 case SIGN_RSA_EMSA_PKCS1_SHA2_512:
 307                         return verify_emsa_pkcs1_signature(this, HASH_SHA512, data, signature);
 308                 case SIGN_RSA_EMSA_PKCS1_SHA3_224:
 309                         return verify_emsa_pkcs1_signature(this, HASH_SHA3_224, data, signature);
 310                 case SIGN_RSA_EMSA_PKCS1_SHA3_256:
 311                         return verify_emsa_pkcs1_signature(this, HASH_SHA3_256, data, signature);
 312                 case SIGN_RSA_EMSA_PKCS1_SHA3_384:
 313                         return verify_emsa_pkcs1_signature(this, HASH_SHA3_384, data, signature);
 314                 case SIGN_RSA_EMSA_PKCS1_SHA3_512:
 315                         return verify_emsa_pkcs1_signature(this, HASH_SHA3_512, data, signature);
 316                 case SIGN_RSA_EMSA_PKCS1_SHA1:
 317                         return verify_emsa_pkcs1_signature(this, HASH_SHA1, data, signature);
 318                 case SIGN_RSA_EMSA_PKCS1_MD5:
 319                         return verify_emsa_pkcs1_signature(this, HASH_MD5, data, signature);
 320                 default:
 321                         DBG1(DBG_LIB, "signature scheme %N not supported in RSA",
 322                                  signature_scheme_names, scheme);
 323                         return FALSE;
 324         }
 325 }
 326
 327 #define MIN_PS_PADDING 8
 328
 329 METHOD(public_key_t, encrypt_, bool,
 330         private_gmp_rsa_public_key_t *this, encryption_scheme_t scheme,
 331         chunk_t plain, chunk_t *crypto)
 332 {
 333         chunk_t em;
 334         u_char *pos;
 335         int padding;
 336         rng_t *rng;
 337
 338         if (scheme != ENCRYPT_RSA_PKCS1)
 339         {
 340                 DBG1(DBG_LIB, "encryption scheme %N not supported",
 341                          encryption_scheme_names, scheme);
 342                 return FALSE;
 343         }
 344         /* number of pseudo-random padding octets */
 345         padding = this->k - plain.len - 3;
 346         if (padding < MIN_PS_PADDING)
 347         {
 348                 DBG1(DBG_LIB, "pseudo-random padding must be at least %d octets",
 349                          MIN_PS_PADDING);
 350                 return FALSE;
 351         }
 352         rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
 353         if (rng == NULL)
 354         {
 355                 DBG1(DBG_LIB, "no random generator available");
 356                 return FALSE;
 357         }
 358
 359         /* padding according to PKCS#1 7.2.1 (RSAES-PKCS1-v1.5-ENCRYPT) */
 360         DBG2(DBG_LIB, "padding %u bytes of data to the rsa modulus size of"
 361                  " %u bytes", plain.len, this->k);
 362         em.len = this->k;
 363         em.ptr = malloc(em.len);
 364         pos = em.ptr;
 365         *pos++ = 0x00;
 366         *pos++ = 0x02;
 367
 368         /* fill with pseudo random octets */
 369         if (!rng_get_bytes_not_zero(rng, padding, pos, TRUE))
 370         {
 371                 DBG1(DBG_LIB, "failed to allocate padding");
 372                 chunk_clear(&em);
 373                 rng->destroy(rng);
 374                 return FALSE;
 375         }
 376         rng->destroy(rng);
 377
 378         pos += padding;
 379
 380         /* append the padding terminator */
 381         *pos++ = 0x00;
 382
 383         /* now add the data */
 384         memcpy(pos, plain.ptr, plain.len);
 385         DBG3(DBG_LIB, "padded data before rsa encryption: %B", &em);
 386
 387         /* rsa encryption using PKCS#1 RSAEP */
 388         *crypto = rsaep(this, em);
 389         DBG3(DBG_LIB, "rsa encrypted data: %B", crypto);
 390         chunk_clear(&em);
 391         return TRUE;
 392 }
 393
 394 METHOD(public_key_t, get_keysize, int,
 395         private_gmp_rsa_public_key_t *this)
 396 {
 397         return mpz_sizeinbase(this->n, 2);
 398 }
 399
 400 METHOD(public_key_t, get_encoding, bool,
 401         private_gmp_rsa_public_key_t *this, cred_encoding_type_t type,
 402         chunk_t *encoding)
 403 {
 404         chunk_t n, e;
 405         bool success;
 406
 407         n = gmp_mpz_to_chunk(this->n);
 408         e = gmp_mpz_to_chunk(this->e);
 409
 410         success = lib->encoding->encode(lib->encoding, type, NULL, encoding,
 411                         CRED_PART_RSA_MODULUS, n, CRED_PART_RSA_PUB_EXP, e, CRED_PART_END);
 412         chunk_free(&n);
 413         chunk_free(&e);
 414
 415         return success;
 416 }
 417
 418 METHOD(public_key_t, get_fingerprint, bool,
 419         private_gmp_rsa_public_key_t *this, cred_encoding_type_t type, chunk_t *fp)
 420 {
 421         chunk_t n, e;
 422         bool success;
 423
 424         if (lib->encoding->get_cache(lib->encoding, type, this, fp))
 425         {
 426                 return TRUE;
 427         }
 428         n = gmp_mpz_to_chunk(this->n);
 429         e = gmp_mpz_to_chunk(this->e);
 430
 431         success = lib->encoding->encode(lib->encoding, type, this, fp,
 432                         CRED_PART_RSA_MODULUS, n, CRED_PART_RSA_PUB_EXP, e, CRED_PART_END);
 433         chunk_free(&n);
 434         chunk_free(&e);
 435
 436         return success;
 437 }
 438
 439 METHOD(public_key_t, get_ref, public_key_t*,
 440         private_gmp_rsa_public_key_t *this)
 441 {
 442         ref_get(&this->ref);
 443         return &this->public.key;
 444 }
 445
 446 METHOD(public_key_t, destroy, void,
 447         private_gmp_rsa_public_key_t *this)
 448 {
 449         if (ref_put(&this->ref))
 450         {
 451                 mpz_clear(this->n);
 452                 mpz_clear(this->e);
 453                 lib->encoding->clear_cache(lib->encoding, this);
 454                 free(this);
 455         }
 456 }
 457
 458 /**
 459  * See header.
 460  */
 461 gmp_rsa_public_key_t *gmp_rsa_public_key_load(key_type_t type, va_list args)
 462 {
 463         private_gmp_rsa_public_key_t *this;
 464         chunk_t n, e;
 465
 466         n = e = chunk_empty;
 467         while (TRUE)
 468         {
 469                 switch (va_arg(args, builder_part_t))
 470                 {
 471                         case BUILD_RSA_MODULUS:
 472                                 n = va_arg(args, chunk_t);
 473                                 continue;
 474                         case BUILD_RSA_PUB_EXP:
 475                                 e = va_arg(args, chunk_t);
 476                                 continue;
 477                         case BUILD_END:
 478                                 break;
 479                         default:
 480                                 return NULL;
 481                 }
 482                 break;
 483         }
 484         if (!e.len || !n.len || (n.ptr[n.len-1] & 0x01) == 0)
 485         {
 486                 return NULL;
 487         }
 488
 489         INIT(this,
 490                 .public = {
 491                         .key = {
 492                                 .get_type = _get_type,
 493                                 .verify = _verify,
 494                                 .encrypt = _encrypt_,
 495                                 .equals = public_key_equals,
 496                                 .get_keysize = _get_keysize,
 497                                 .get_fingerprint = _get_fingerprint,
 498                                 .has_fingerprint = public_key_has_fingerprint,
 499                                 .get_encoding = _get_encoding,
 500                                 .get_ref = _get_ref,
 501                                 .destroy = _destroy,
 502                         },
 503                 },
 504                 .ref = 1,
 505         );
 506
 507         mpz_init(this->n);
 508         mpz_init(this->e);
 509
 510         mpz_import(this->n, n.len, 1, 1, 1, 0, n.ptr);
 511         mpz_import(this->e, e.len, 1, 1, 1, 0, e.ptr);
 512
 513         this->k = (mpz_sizeinbase(this->n, 2) + 7) / BITS_PER_BYTE;
 514
 515         if (!mpz_sgn(this->e))
 516         {
 517                 destroy(this);
 518                 return NULL;
 519         }
 520         return &this->public;
 521 }