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