src/util/srp.cpp

   1 /*
   2  * Secure Remote Password 6a implementation
   3  * https://github.com/est31/csrp-gmp
   4  *
   5  * The MIT License (MIT)
   6  *
   7  * Copyright (c) 2010, 2013 Tom Cocagne, 2015 est31 <MTest31@outlook.com>
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a copy of
  10  * this software and associated documentation files (the "Software"), to deal in
  11  * the Software without restriction, including without limitation the rights to
  12  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  13  * of the Software, and to permit persons to whom the Software is furnished to do
  14  * so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included in all
  17  * copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  25  * SOFTWARE.
  26  *
  27  */
  28
  29 // clang-format off
  30
  31 #include <cstddef>
  32
  33 #ifdef WIN32
  34         #include <windows.h>
  35         #include <wincrypt.h>
  36 #else
  37         #include <ctime>
  38
  39 #endif
  40 // clang-format on
  41
  42 #include <cstdlib>
  43 #include <cstring>
  44 #include <cstdio>
  45 #include <cstdint>
  46
  47 #include <config.h>
  48
  49 #if USE_SYSTEM_GMP
  50         #include <gmp.h>
  51 #else
  52         #include <mini-gmp.h>
  53 #endif
  54
  55 #include <util/sha2.h>
  56
  57 #include "srp.h"
  58 //#define CSRP_USE_SHA1
  59 #define CSRP_USE_SHA256
  60
  61 #define srp_dbg_data(data, datalen, prevtext) ;
  62 /*void srp_dbg_data(unsigned char * data, size_t datalen, char * prevtext)
  63 {
  64         printf(prevtext);
  65         size_t i;
  66         for (i = 0; i < datalen; i++)
  67         {
  68                 printf("%02X", data[i]);
  69         }
  70         printf("\n");
  71 }*/
  72
  73 static int g_initialized = 0;
  74
  75 #define RAND_BUFF_MAX 128
  76 static unsigned int g_rand_idx;
  77 static unsigned char g_rand_buff[RAND_BUFF_MAX];
  78
  79 void *(*srp_alloc)(size_t) = &malloc;
  80 void *(*srp_realloc)(void *, size_t) = &realloc;
  81 void (*srp_free)(void *) = &free;
  82
  83 // clang-format off
  84 void srp_set_memory_functions(
  85                 void *(*new_srp_alloc)(size_t),
  86                 void *(*new_srp_realloc)(void *, size_t),
  87                 void (*new_srp_free)(void *))
  88 {
  89         srp_alloc = new_srp_alloc;
  90         srp_realloc = new_srp_realloc;
  91         srp_free = new_srp_free;
  92 }
  93 // clang-format on
  94
  95 typedef struct {
  96         mpz_t N;
  97         mpz_t g;
  98 } NGConstant;
  99
 100 struct NGHex {
 101         const char *n_hex;
 102         const char *g_hex;
 103 };
 104
 105 /* All constants here were pulled from Appendix A of RFC 5054 */
 106 static struct NGHex global_Ng_constants[] = {
 107         {/* 1024 */
 108                 "EEAF0AB9ADB38DD69C33F80AFA8FC5E86072618775FF3C0B9EA2314C"
 109                 "9C256576D674DF7496EA81D3383B4813D692C6E0E0D5D8E250B98BE4"
 110                 "8E495C1D6089DAD15DC7D7B46154D6B6CE8EF4AD69B15D4982559B29"
 111                 "7BCF1885C529F566660E57EC68EDBC3C05726CC02FD4CBF4976EAA9A"
 112                 "FD5138FE8376435B9FC61D2FC0EB06E3",
 113                 "2"},
 114         {/* 2048 */
 115                 "AC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC319294"
 116                 "3DB56050A37329CBB4A099ED8193E0757767A13DD52312AB4B03310D"
 117                 "CD7F48A9DA04FD50E8083969EDB767B0CF6095179A163AB3661A05FB"
 118                 "D5FAAAE82918A9962F0B93B855F97993EC975EEAA80D740ADBF4FF74"
 119                 "7359D041D5C33EA71D281E446B14773BCA97B43A23FB801676BD207A"
 120                 "436C6481F1D2B9078717461A5B9D32E688F87748544523B524B0D57D"
 121                 "5EA77A2775D2ECFA032CFBDBF52FB3786160279004E57AE6AF874E73"
 122                 "03CE53299CCC041C7BC308D82A5698F3A8D0C38271AE35F8E9DBFBB6"
 123                 "94B5C803D89F7AE435DE236D525F54759B65E372FCD68EF20FA7111F"
 124                 "9E4AFF73",
 125                 "2"},
 126         {/* 4096 */
 127                 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
 128                 "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
 129                 "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
 130                 "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
 131                 "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8"
 132                 "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D"
 133                 "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C"
 134                 "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718"
 135                 "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D"
 136                 "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D"
 137                 "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226"
 138                 "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C"
 139                 "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC"
 140                 "E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26"
 141                 "99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB"
 142                 "04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2"
 143                 "233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127"
 144                 "D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934063199"
 145                 "FFFFFFFFFFFFFFFF",
 146                 "5"},
 147         {/* 8192 */
 148                 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
 149                 "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
 150                 "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
 151                 "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
 152                 "49286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8"
 153                 "FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D"
 154                 "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C"
 155                 "180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF695581718"
 156                 "3995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D"
 157                 "04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7D"
 158                 "B3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D226"
 159                 "1AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200C"
 160                 "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFC"
 161                 "E0FD108E4B82D120A92108011A723C12A787E6D788719A10BDBA5B26"
 162                 "99C327186AF4E23C1A946834B6150BDA2583E9CA2AD44CE8DBBBC2DB"
 163                 "04DE8EF92E8EFC141FBECAA6287C59474E6BC05D99B2964FA090C3A2"
 164                 "233BA186515BE7ED1F612970CEE2D7AFB81BDD762170481CD0069127"
 165                 "D5B05AA993B4EA988D8FDDC186FFB7DC90A6C08F4DF435C934028492"
 166                 "36C3FAB4D27C7026C1D4DCB2602646DEC9751E763DBA37BDF8FF9406"
 167                 "AD9E530EE5DB382F413001AEB06A53ED9027D831179727B0865A8918"
 168                 "DA3EDBEBCF9B14ED44CE6CBACED4BB1BDB7F1447E6CC254B33205151"
 169                 "2BD7AF426FB8F401378CD2BF5983CA01C64B92ECF032EA15D1721D03"
 170                 "F482D7CE6E74FEF6D55E702F46980C82B5A84031900B1C9E59E7C97F"
 171                 "BEC7E8F323A97A7E36CC88BE0F1D45B7FF585AC54BD407B22B4154AA"
 172                 "CC8F6D7EBF48E1D814CC5ED20F8037E0A79715EEF29BE32806A1D58B"
 173                 "B7C5DA76F550AA3D8A1FBFF0EB19CCB1A313D55CDA56C9EC2EF29632"
 174                 "387FE8D76E3C0468043E8F663F4860EE12BF2D5B0B7474D6E694F91E"
 175                 "6DBE115974A3926F12FEE5E438777CB6A932DF8CD8BEC4D073B931BA"
 176                 "3BC832B68D9DD300741FA7BF8AFC47ED2576F6936BA424663AAB639C"
 177                 "5AE4F5683423B4742BF1C978238F16CBE39D652DE3FDB8BEFC848AD9"
 178                 "22222E04A4037C0713EB57A81A23F0C73473FC646CEA306B4BCBC886"
 179                 "2F8385DDFA9D4B7FA2C087E879683303ED5BDD3A062B3CF5B3A278A6"
 180                 "6D2A13F83F44F82DDF310EE074AB6A364597E899A0255DC164F31CC5"
 181                 "0846851DF9AB48195DED7EA1B1D510BD7EE74D73FAF36BC31ECFA268"
 182                 "359046F4EB879F924009438B481C6CD7889A002ED5EE382BC9190DA6"
 183                 "FC026E479558E4475677E9AA9E3050E2765694DFC81F56E880B96E71"
 184                 "60C980DD98EDD3DFFFFFFFFFFFFFFFFF",
 185                 "13"},
 186         {0, 0} /* null sentinel */
 187 };
 188
 189 static void delete_ng(NGConstant *ng)
 190 {
 191         if (ng) {
 192                 mpz_clear(ng->N);
 193                 mpz_clear(ng->g);
 194                 srp_free(ng);
 195         }
 196 }
 197
 198 static NGConstant *new_ng(SRP_NGType ng_type, const char *n_hex, const char *g_hex)
 199 {
 200         NGConstant *ng = (NGConstant *)srp_alloc(sizeof(NGConstant));
 201
 202         if (!ng) return 0;
 203
 204         mpz_init(ng->N);
 205         mpz_init(ng->g);
 206
 207         if (ng_type != SRP_NG_CUSTOM) {
 208                 n_hex = global_Ng_constants[ng_type].n_hex;
 209                 g_hex = global_Ng_constants[ng_type].g_hex;
 210         }
 211
 212         int rv = 0;
 213         rv = mpz_set_str(ng->N, n_hex, 16);
 214         rv = rv | mpz_set_str(ng->g, g_hex, 16);
 215
 216         if (rv) {
 217                 delete_ng(ng);
 218                 return 0;
 219         }
 220
 221         return ng;
 222 }
 223
 224 typedef union {
 225         SHA_CTX sha;
 226         SHA256_CTX sha256;
 227         // SHA512_CTX sha512;
 228 } HashCTX;
 229
 230 struct SRPVerifier {
 231         SRP_HashAlgorithm hash_alg;
 232         NGConstant *ng;
 233
 234         char *username;
 235         unsigned char *bytes_B;
 236         int authenticated;
 237
 238         unsigned char M[SHA512_DIGEST_LENGTH];
 239         unsigned char H_AMK[SHA512_DIGEST_LENGTH];
 240         unsigned char session_key[SHA512_DIGEST_LENGTH];
 241 };
 242
 243 struct SRPUser {
 244         SRP_HashAlgorithm hash_alg;
 245         NGConstant *ng;
 246
 247         mpz_t a;
 248         mpz_t A;
 249         mpz_t S;
 250
 251         unsigned char *bytes_A;
 252         int authenticated;
 253
 254         char *username;
 255         char *username_verifier;
 256         unsigned char *password;
 257         size_t password_len;
 258
 259         unsigned char M[SHA512_DIGEST_LENGTH];
 260         unsigned char H_AMK[SHA512_DIGEST_LENGTH];
 261         unsigned char session_key[SHA512_DIGEST_LENGTH];
 262 };
 263
 264 // clang-format off
 265 static int hash_init(SRP_HashAlgorithm alg, HashCTX *c)
 266 {
 267         switch (alg) {
 268 #ifdef CSRP_USE_SHA1
 269                 case SRP_SHA1: return SHA1_Init(&c->sha);
 270 #endif
 271                 /*
 272                 case SRP_SHA224: return SHA224_Init(&c->sha256);
 273                 */
 274 #ifdef CSRP_USE_SHA256
 275                 case SRP_SHA256: return SHA256_Init(&c->sha256);
 276 #endif
 277                 /*
 278                 case SRP_SHA384: return SHA384_Init(&c->sha512);
 279                 case SRP_SHA512: return SHA512_Init(&c->sha512);
 280                 */
 281                 default: return -1;
 282         };
 283 }
 284 static int hash_update( SRP_HashAlgorithm alg, HashCTX *c, const void *data, size_t len )
 285 {
 286         switch (alg) {
 287 #ifdef CSRP_USE_SHA1
 288                 case SRP_SHA1: return SHA1_Update(&c->sha, data, len);
 289 #endif
 290                 /*
 291                 case SRP_SHA224: return SHA224_Update(&c->sha256, data, len);
 292                 */
 293 #ifdef CSRP_USE_SHA256
 294                 case SRP_SHA256: return SHA256_Update(&c->sha256, data, len);
 295 #endif
 296                 /*
 297                 case SRP_SHA384: return SHA384_Update(&c->sha512, data, len);
 298                 case SRP_SHA512: return SHA512_Update(&c->sha512, data, len);
 299                 */
 300                 default: return -1;
 301         };
 302 }
 303 static int hash_final( SRP_HashAlgorithm alg, HashCTX *c, unsigned char *md )
 304 {
 305         switch (alg) {
 306 #ifdef CSRP_USE_SHA1
 307                 case SRP_SHA1: return SHA1_Final(md, &c->sha);
 308 #endif
 309                 /*
 310                 case SRP_SHA224: return SHA224_Final(md, &c->sha256);
 311                 */
 312 #ifdef CSRP_USE_SHA256
 313                 case SRP_SHA256: return SHA256_Final(md, &c->sha256);
 314 #endif
 315                 /*
 316                 case SRP_SHA384: return SHA384_Final(md, &c->sha512);
 317                 case SRP_SHA512: return SHA512_Final(md, &c->sha512);
 318                 */
 319                 default: return -1;
 320         };
 321 }
 322 static unsigned char *hash(SRP_HashAlgorithm alg, const unsigned char *d, size_t n, unsigned char *md)
 323 {
 324         switch (alg) {
 325 #ifdef CSRP_USE_SHA1
 326                 case SRP_SHA1: return SHA1(d, n, md);
 327 #endif
 328                 /*
 329                 case SRP_SHA224: return SHA224( d, n, md );
 330                 */
 331 #ifdef CSRP_USE_SHA256
 332                 case SRP_SHA256: return SHA256(d, n, md);
 333 #endif
 334                 /*
 335                 case SRP_SHA384: return SHA384( d, n, md );
 336                 case SRP_SHA512: return SHA512( d, n, md );
 337                 */
 338                 default: return 0;
 339         };
 340 }
 341 static size_t hash_length(SRP_HashAlgorithm alg)
 342 {
 343         switch (alg) {
 344 #ifdef CSRP_USE_SHA1
 345                 case SRP_SHA1: return SHA_DIGEST_LENGTH;
 346 #endif
 347                 /*
 348                 case SRP_SHA224: return SHA224_DIGEST_LENGTH;
 349                 */
 350 #ifdef CSRP_USE_SHA256
 351                 case SRP_SHA256: return SHA256_DIGEST_LENGTH;
 352 #endif
 353                 /*
 354                 case SRP_SHA384: return SHA384_DIGEST_LENGTH;
 355                 case SRP_SHA512: return SHA512_DIGEST_LENGTH;
 356                 */
 357                 default: return -1;
 358         };
 359 }
 360 // clang-format on
 361
 362 inline static int mpz_num_bytes(const mpz_t op)
 363 {
 364         return (mpz_sizeinbase(op, 2) + 7) / 8;
 365 }
 366
 367 inline static void mpz_to_bin(const mpz_t op, unsigned char *to)
 368 {
 369         mpz_export(to, NULL, 1, 1, 1, 0, op);
 370 }
 371
 372 inline static void mpz_from_bin(const unsigned char *s, size_t len, mpz_t ret)
 373 {
 374         mpz_import(ret, len, 1, 1, 1, 0, s);
 375 }
 376
 377 // set op to (op1 * op2) mod d, using tmp for the calculation
 378 inline static void mpz_mulm(
 379         mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
 380 {
 381         mpz_mul(tmp, op1, op2);
 382         mpz_mod(op, tmp, d);
 383 }
 384
 385 // set op to (op1 + op2) mod d, using tmp for the calculation
 386 inline static void mpz_addm(
 387         mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
 388 {
 389         mpz_add(tmp, op1, op2);
 390         mpz_mod(op, tmp, d);
 391 }
 392
 393 // set op to (op1 - op2) mod d, using tmp for the calculation
 394 inline static void mpz_subm(
 395         mpz_t op, const mpz_t op1, const mpz_t op2, const mpz_t d, mpz_t tmp)
 396 {
 397         mpz_sub(tmp, op1, op2);
 398         mpz_mod(op, tmp, d);
 399 }
 400
 401 static SRP_Result H_nn(
 402         mpz_t result, SRP_HashAlgorithm alg, const mpz_t N, const mpz_t n1, const mpz_t n2)
 403 {
 404         unsigned char buff[SHA512_DIGEST_LENGTH];
 405         size_t len_N = mpz_num_bytes(N);
 406         size_t len_n1 = mpz_num_bytes(n1);
 407         size_t len_n2 = mpz_num_bytes(n2);
 408         size_t nbytes = len_N + len_N;
 409         unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
 410         if (!bin) return SRP_ERR;
 411         if (len_n1 > len_N || len_n2 > len_N) {
 412                 srp_free(bin);
 413                 return SRP_ERR;
 414         }
 415         memset(bin, 0, nbytes);
 416         mpz_to_bin(n1, bin + (len_N - len_n1));
 417         mpz_to_bin(n2, bin + (len_N + len_N - len_n2));
 418         hash(alg, bin, nbytes, buff);
 419         srp_free(bin);
 420         mpz_from_bin(buff, hash_length(alg), result);
 421         return SRP_OK;
 422 }
 423
 424 static SRP_Result H_ns(mpz_t result, SRP_HashAlgorithm alg, const unsigned char *n,
 425         size_t len_n, const unsigned char *bytes, uint32_t len_bytes)
 426 {
 427         unsigned char buff[SHA512_DIGEST_LENGTH];
 428         size_t nbytes = len_n + len_bytes;
 429         unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
 430         if (!bin) return SRP_ERR;
 431         memcpy(bin, n, len_n);
 432         memcpy(bin + len_n, bytes, len_bytes);
 433         hash(alg, bin, nbytes, buff);
 434         srp_free(bin);
 435         mpz_from_bin(buff, hash_length(alg), result);
 436         return SRP_OK;
 437 }
 438
 439 static int calculate_x(mpz_t result, SRP_HashAlgorithm alg, const unsigned char *salt,
 440         size_t salt_len, const char *username, const unsigned char *password,
 441         size_t password_len)
 442 {
 443         unsigned char ucp_hash[SHA512_DIGEST_LENGTH];
 444         HashCTX ctx;
 445         hash_init(alg, &ctx);
 446
 447         srp_dbg_data((char *)username, strlen(username), "Username for x: ");
 448         srp_dbg_data((char *)password, password_len, "Password for x: ");
 449         hash_update(alg, &ctx, username, strlen(username));
 450         hash_update(alg, &ctx, ":", 1);
 451         hash_update(alg, &ctx, password, password_len);
 452
 453         hash_final(alg, &ctx, ucp_hash);
 454
 455         return H_ns(result, alg, salt, salt_len, ucp_hash, hash_length(alg));
 456 }
 457
 458 static SRP_Result update_hash_n(SRP_HashAlgorithm alg, HashCTX *ctx, const mpz_t n)
 459 {
 460         size_t len = mpz_num_bytes(n);
 461         unsigned char *n_bytes = (unsigned char *)srp_alloc(len);
 462         if (!n_bytes) return SRP_ERR;
 463         mpz_to_bin(n, n_bytes);
 464         hash_update(alg, ctx, n_bytes, len);
 465         srp_free(n_bytes);
 466         return SRP_OK;
 467 }
 468
 469 static SRP_Result hash_num(SRP_HashAlgorithm alg, const mpz_t n, unsigned char *dest)
 470 {
 471         int nbytes = mpz_num_bytes(n);
 472         unsigned char *bin = (unsigned char *)srp_alloc(nbytes);
 473         if (!bin) return SRP_ERR;
 474         mpz_to_bin(n, bin);
 475         hash(alg, bin, nbytes, dest);
 476         srp_free(bin);
 477         return SRP_OK;
 478 }
 479
 480 static SRP_Result calculate_M(SRP_HashAlgorithm alg, NGConstant *ng, unsigned char *dest,
 481         const char *I, const unsigned char *s_bytes, size_t s_len, const mpz_t A,
 482         const mpz_t B, const unsigned char *K)
 483 {
 484         unsigned char H_N[SHA512_DIGEST_LENGTH];
 485         unsigned char H_g[SHA512_DIGEST_LENGTH];
 486         unsigned char H_I[SHA512_DIGEST_LENGTH];
 487         unsigned char H_xor[SHA512_DIGEST_LENGTH];
 488         HashCTX ctx;
 489         size_t i = 0;
 490         size_t hash_len = hash_length(alg);
 491
 492         if (!hash_num(alg, ng->N, H_N)) return SRP_ERR;
 493         if (!hash_num(alg, ng->g, H_g)) return SRP_ERR;
 494
 495         hash(alg, (const unsigned char *)I, strlen(I), H_I);
 496
 497         for (i = 0; i < hash_len; i++)
 498                 H_xor[i] = H_N[i] ^ H_g[i];
 499
 500         hash_init(alg, &ctx);
 501
 502         hash_update(alg, &ctx, H_xor, hash_len);
 503         hash_update(alg, &ctx, H_I, hash_len);
 504         hash_update(alg, &ctx, s_bytes, s_len);
 505         if (!update_hash_n(alg, &ctx, A)) return SRP_ERR;
 506         if (!update_hash_n(alg, &ctx, B)) return SRP_ERR;
 507         hash_update(alg, &ctx, K, hash_len);
 508
 509         hash_final(alg, &ctx, dest);
 510         return SRP_OK;
 511 }
 512
 513 static SRP_Result calculate_H_AMK(SRP_HashAlgorithm alg, unsigned char *dest,
 514         const mpz_t A, const unsigned char *M, const unsigned char *K)
 515 {
 516         HashCTX ctx;
 517
 518         hash_init(alg, &ctx);
 519
 520         if (!update_hash_n(alg, &ctx, A)) return SRP_ERR;
 521         hash_update(alg, &ctx, M, hash_length(alg));
 522         hash_update(alg, &ctx, K, hash_length(alg));
 523
 524         hash_final(alg, &ctx, dest);
 525         return SRP_OK;
 526 }
 527
 528 static SRP_Result fill_buff()
 529 {
 530         g_rand_idx = 0;
 531
 532 #ifdef WIN32
 533         HCRYPTPROV wctx;
 534 #else
 535         FILE *fp = 0;
 536 #endif
 537
 538 #ifdef WIN32
 539
 540         if (!CryptAcquireContext(&wctx, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
 541                 return SRP_ERR;
 542         if (!CryptGenRandom(wctx, sizeof(g_rand_buff), (BYTE *)g_rand_buff)) return SRP_ERR;
 543         if (!CryptReleaseContext(wctx, 0)) return SRP_ERR;
 544
 545 #else
 546         fp = fopen("/dev/urandom", "r");
 547
 548         if (!fp) return SRP_ERR;
 549
 550         if (fread(g_rand_buff, sizeof(g_rand_buff), 1, fp) != 1) { fclose(fp); return SRP_ERR; }
 551         if (fclose(fp)) return SRP_ERR;
 552 #endif
 553         return SRP_OK;
 554 }
 555
 556 static SRP_Result mpz_fill_random(mpz_t num)
 557 {
 558         // was call: BN_rand(num, 256, -1, 0);
 559         if (RAND_BUFF_MAX - g_rand_idx < 32)
 560                 if (fill_buff() != SRP_OK) return SRP_ERR;
 561         mpz_from_bin((const unsigned char *)(&g_rand_buff[g_rand_idx]), 32, num);
 562         g_rand_idx += 32;
 563         return SRP_OK;
 564 }
 565
 566 static SRP_Result init_random()
 567 {
 568         if (g_initialized) return SRP_OK;
 569         SRP_Result ret = fill_buff();
 570         g_initialized = (ret == SRP_OK);
 571         return ret;
 572 }
 573
 574 #define srp_dbg_num(num, text) ;
 575 /*void srp_dbg_num(mpz_t num, char * prevtext)
 576 {
 577         int len_num = mpz_num_bytes(num);
 578         char *bytes_num = (char*) srp_alloc(len_num);
 579         mpz_to_bin(num, (unsigned char *) bytes_num);
 580         srp_dbg_data(bytes_num, len_num, prevtext);
 581         srp_free(bytes_num);
 582
 583 }*/
 584
 585 /***********************************************************************************************************
 586  *
 587  *  Exported Functions
 588  *
 589  ***********************************************************************************************************/
 590
 591 // clang-format off
 592 SRP_Result srp_create_salted_verification_key( SRP_HashAlgorithm alg,
 593         SRP_NGType ng_type, const char *username_for_verifier,
 594         const unsigned char *password, size_t len_password,
 595         unsigned char **bytes_s,  size_t *len_s,
 596         unsigned char **bytes_v, size_t *len_v,
 597         const char *n_hex, const char *g_hex )
 598 {
 599         SRP_Result ret = SRP_OK;
 600
 601         mpz_t v; mpz_init(v);
 602         mpz_t x; mpz_init(x);
 603         // clang-format on
 604
 605         NGConstant *ng = new_ng(ng_type, n_hex, g_hex);
 606
 607         if (!ng) goto error_and_exit;
 608
 609         if (init_random() != SRP_OK) /* Only happens once */
 610                 goto error_and_exit;
 611
 612         if (*bytes_s == NULL) {
 613                 size_t size_to_fill = 16;
 614                 *len_s = size_to_fill;
 615                 if (RAND_BUFF_MAX - g_rand_idx < size_to_fill)
 616                         if (fill_buff() != SRP_OK) goto error_and_exit;
 617                 *bytes_s = (unsigned char *)srp_alloc(size_to_fill);
 618                 if (!*bytes_s) goto error_and_exit;
 619                 memcpy(*bytes_s, &g_rand_buff[g_rand_idx], size_to_fill);
 620                 g_rand_idx += size_to_fill;
 621         }
 622
 623         if (!calculate_x(
 624                         x, alg, *bytes_s, *len_s, username_for_verifier, password, len_password))
 625                 goto error_and_exit;
 626
 627         srp_dbg_num(x, "Server calculated x: ");
 628
 629         mpz_powm(v, ng->g, x, ng->N);
 630
 631         *len_v = mpz_num_bytes(v);
 632
 633         *bytes_v = (unsigned char *)srp_alloc(*len_v);
 634
 635         if (!*bytes_v) goto error_and_exit;
 636
 637         mpz_to_bin(v, *bytes_v);
 638
 639 cleanup_and_exit:
 640         delete_ng(ng);
 641         mpz_clear(v);
 642         mpz_clear(x);
 643         return ret;
 644 error_and_exit:
 645         ret = SRP_ERR;
 646         goto cleanup_and_exit;
 647 }
 648
 649 // clang-format off
 650
 651 /* Out: bytes_B, len_B.
 652  *
 653  * On failure, bytes_B will be set to NULL and len_B will be set to 0
 654  */
 655 struct SRPVerifier *srp_verifier_new(SRP_HashAlgorithm alg,
 656         SRP_NGType ng_type, const char *username,
 657         const unsigned char *bytes_s, size_t len_s,
 658         const unsigned char *bytes_v, size_t len_v,
 659         const unsigned char *bytes_A, size_t len_A,
 660         const unsigned char *bytes_b, size_t len_b,
 661         unsigned char **bytes_B, size_t *len_B,
 662         const char *n_hex, const char *g_hex )
 663 {
 664         mpz_t v; mpz_init(v); mpz_from_bin(bytes_v, len_v, v);
 665         mpz_t A; mpz_init(A); mpz_from_bin(bytes_A, len_A, A);
 666         mpz_t u; mpz_init(u);
 667         mpz_t B; mpz_init(B);
 668         mpz_t S; mpz_init(S);
 669         mpz_t b; mpz_init(b);
 670         mpz_t k; mpz_init(k);
 671         mpz_t tmp1; mpz_init(tmp1);
 672         mpz_t tmp2; mpz_init(tmp2);
 673         mpz_t tmp3; mpz_init(tmp3);
 674         // clang-format on
 675         size_t ulen = strlen(username) + 1;
 676         NGConstant *ng = new_ng(ng_type, n_hex, g_hex);
 677         struct SRPVerifier *ver = 0;
 678
 679         *len_B = 0;
 680         *bytes_B = 0;
 681
 682         if (!ng) goto cleanup_and_exit;
 683
 684         ver = (struct SRPVerifier *)srp_alloc(sizeof(struct SRPVerifier));
 685
 686         if (!ver) goto cleanup_and_exit;
 687
 688         if (init_random() != SRP_OK) { /* Only happens once */
 689                 srp_free(ver);
 690                 ver = 0;
 691                 goto cleanup_and_exit;
 692         }
 693
 694         ver->username = (char *)srp_alloc(ulen);
 695         ver->hash_alg = alg;
 696         ver->ng = ng;
 697
 698         if (!ver->username) {
 699                 srp_free(ver);
 700                 ver = 0;
 701                 goto cleanup_and_exit;
 702         }
 703
 704         memcpy(ver->username, username, ulen);
 705
 706         ver->authenticated = 0;
 707
 708         /* SRP-6a safety check */
 709         mpz_mod(tmp1, A, ng->N);
 710         if (mpz_sgn(tmp1) != 0) {
 711                 if (bytes_b) {
 712                         mpz_from_bin(bytes_b, len_b, b);
 713                 } else {
 714                         if (!mpz_fill_random(b)) goto ver_cleanup_and_exit;
 715                 }
 716
 717                 if (!H_nn(k, alg, ng->N, ng->N, ng->g)) goto ver_cleanup_and_exit;
 718
 719                 /* B = kv + g^b */
 720                 mpz_mulm(tmp1, k, v, ng->N, tmp3);
 721                 mpz_powm(tmp2, ng->g, b, ng->N);
 722                 mpz_addm(B, tmp1, tmp2, ng->N, tmp3);
 723
 724                 if (!H_nn(u, alg, ng->N, A, B)) goto ver_cleanup_and_exit;
 725
 726                 srp_dbg_num(u, "Server calculated u: ");
 727
 728                 /* S = (A *(v^u)) ^ b */
 729                 mpz_powm(tmp1, v, u, ng->N);
 730                 mpz_mulm(tmp2, A, tmp1, ng->N, tmp3);
 731                 mpz_powm(S, tmp2, b, ng->N);
 732
 733                 if (!hash_num(alg, S, ver->session_key)) goto ver_cleanup_and_exit;
 734
 735                 if (!calculate_M(
 736                                 alg, ng, ver->M, username, bytes_s, len_s, A, B, ver->session_key)) {
 737                         goto ver_cleanup_and_exit;
 738                 }
 739                 if (!calculate_H_AMK(alg, ver->H_AMK, A, ver->M, ver->session_key)) {
 740                         goto ver_cleanup_and_exit;
 741                 }
 742
 743                 *len_B = mpz_num_bytes(B);
 744                 *bytes_B = (unsigned char *)srp_alloc(*len_B);
 745
 746                 if (!*bytes_B) {
 747                         *len_B = 0;
 748                         goto ver_cleanup_and_exit;
 749                 }
 750
 751                 mpz_to_bin(B, *bytes_B);
 752
 753                 ver->bytes_B = *bytes_B;
 754         } else {
 755                 srp_free(ver);
 756                 ver = 0;
 757         }
 758
 759 cleanup_and_exit:
 760         mpz_clear(v);
 761         mpz_clear(A);
 762         mpz_clear(u);
 763         mpz_clear(k);
 764         mpz_clear(B);
 765         mpz_clear(S);
 766         mpz_clear(b);
 767         mpz_clear(tmp1);
 768         mpz_clear(tmp2);
 769         mpz_clear(tmp3);
 770         return ver;
 771 ver_cleanup_and_exit:
 772         srp_free(ver->username);
 773         srp_free(ver);
 774         ver = 0;
 775         goto cleanup_and_exit;
 776 }
 777
 778 void srp_verifier_delete(struct SRPVerifier *ver)
 779 {
 780         if (ver) {
 781                 delete_ng(ver->ng);
 782                 srp_free(ver->username);
 783                 srp_free(ver->bytes_B);
 784                 memset(ver, 0, sizeof(*ver));
 785                 srp_free(ver);
 786         }
 787 }
 788
 789 int srp_verifier_is_authenticated(struct SRPVerifier *ver)
 790 {
 791         return ver->authenticated;
 792 }
 793
 794 const char *srp_verifier_get_username(struct SRPVerifier *ver)
 795 {
 796         return ver->username;
 797 }
 798
 799 const unsigned char *srp_verifier_get_session_key(
 800         struct SRPVerifier *ver, size_t *key_length)
 801 {
 802         if (key_length) *key_length = hash_length(ver->hash_alg);
 803         return ver->session_key;
 804 }
 805
 806 size_t srp_verifier_get_session_key_length(struct SRPVerifier *ver)
 807 {
 808         return hash_length(ver->hash_alg);
 809 }
 810
 811 /* user_M must be exactly SHA512_DIGEST_LENGTH bytes in size */
 812 void srp_verifier_verify_session(
 813         struct SRPVerifier *ver, const unsigned char *user_M, unsigned char **bytes_HAMK)
 814 {
 815         if (memcmp(ver->M, user_M, hash_length(ver->hash_alg)) == 0) {
 816                 ver->authenticated = 1;
 817                 *bytes_HAMK = ver->H_AMK;
 818         } else
 819                 *bytes_HAMK = NULL;
 820 }
 821
 822 /*******************************************************************************/
 823
 824 struct SRPUser *srp_user_new(SRP_HashAlgorithm alg, SRP_NGType ng_type,
 825         const char *username, const char *username_for_verifier,
 826         const unsigned char *bytes_password, size_t len_password, const char *n_hex,
 827         const char *g_hex)
 828 {
 829         struct SRPUser *usr = (struct SRPUser *)srp_alloc(sizeof(struct SRPUser));
 830         size_t ulen = strlen(username) + 1;
 831         size_t uvlen = strlen(username_for_verifier) + 1;
 832
 833         if (!usr) goto err_exit;
 834
 835         if (init_random() != SRP_OK) /* Only happens once */
 836                 goto err_exit;
 837
 838         usr->hash_alg = alg;
 839         usr->ng = new_ng(ng_type, n_hex, g_hex);
 840
 841         mpz_init(usr->a);
 842         mpz_init(usr->A);
 843         mpz_init(usr->S);
 844
 845         if (!usr->ng) goto err_exit;
 846
 847         usr->username = (char *)srp_alloc(ulen);
 848         usr->username_verifier = (char *)srp_alloc(uvlen);
 849         usr->password = (unsigned char *)srp_alloc(len_password);
 850         usr->password_len = len_password;
 851
 852         if (!usr->username || !usr->password || !usr->username_verifier) goto err_exit;
 853
 854         memcpy(usr->username, username, ulen);
 855         memcpy(usr->username_verifier, username_for_verifier, uvlen);
 856         memcpy(usr->password, bytes_password, len_password);
 857
 858         usr->authenticated = 0;
 859
 860         usr->bytes_A = 0;
 861
 862         return usr;
 863
 864 err_exit:
 865         if (usr) {
 866                 mpz_clear(usr->a);
 867                 mpz_clear(usr->A);
 868                 mpz_clear(usr->S);
 869                 delete_ng(usr->ng);
 870                 srp_free(usr->username);
 871                 srp_free(usr->username_verifier);
 872                 if (usr->password) {
 873                         memset(usr->password, 0, usr->password_len);
 874                         srp_free(usr->password);
 875                 }
 876                 srp_free(usr);
 877         }
 878
 879         return 0;
 880 }
 881
 882 void srp_user_delete(struct SRPUser *usr)
 883 {
 884         if (usr) {
 885                 mpz_clear(usr->a);
 886                 mpz_clear(usr->A);
 887                 mpz_clear(usr->S);
 888
 889                 delete_ng(usr->ng);
 890
 891                 memset(usr->password, 0, usr->password_len);
 892
 893                 srp_free(usr->username);
 894                 srp_free(usr->username_verifier);
 895                 srp_free(usr->password);
 896
 897                 if (usr->bytes_A) srp_free(usr->bytes_A);
 898
 899                 memset(usr, 0, sizeof(*usr));
 900                 srp_free(usr);
 901         }
 902 }
 903
 904 int srp_user_is_authenticated(struct SRPUser *usr)
 905 {
 906         return usr->authenticated;
 907 }
 908
 909 const char *srp_user_get_username(struct SRPUser *usr)
 910 {
 911         return usr->username;
 912 }
 913
 914 const unsigned char *srp_user_get_session_key(struct SRPUser *usr, size_t *key_length)
 915 {
 916         if (key_length) *key_length = hash_length(usr->hash_alg);
 917         return usr->session_key;
 918 }
 919
 920 size_t srp_user_get_session_key_length(struct SRPUser *usr)
 921 {
 922         return hash_length(usr->hash_alg);
 923 }
 924
 925 // clang-format off
 926 /* Output: username, bytes_A, len_A */
 927 SRP_Result srp_user_start_authentication(struct SRPUser *usr, char **username,
 928         const unsigned char *bytes_a, size_t len_a,
 929         unsigned char **bytes_A, size_t *len_A)
 930 {
 931         // clang-format on
 932         if (bytes_a) {
 933                 mpz_from_bin(bytes_a, len_a, usr->a);
 934         } else {
 935                 if (!mpz_fill_random(usr->a)) goto error_and_exit;
 936         }
 937
 938         mpz_powm(usr->A, usr->ng->g, usr->a, usr->ng->N);
 939
 940         *len_A = mpz_num_bytes(usr->A);
 941         *bytes_A = (unsigned char *)srp_alloc(*len_A);
 942
 943         if (!*bytes_A) goto error_and_exit;
 944
 945         mpz_to_bin(usr->A, *bytes_A);
 946
 947         usr->bytes_A = *bytes_A;
 948         if (username) *username = usr->username;
 949
 950         return SRP_OK;
 951
 952 error_and_exit:
 953         *len_A = 0;
 954         *bytes_A = 0;
 955         *username = 0;
 956         return SRP_ERR;
 957 }
 958
 959 // clang-format off
 960 /* Output: bytes_M. Buffer length is SHA512_DIGEST_LENGTH */
 961 void  srp_user_process_challenge(struct SRPUser *usr,
 962         const unsigned char *bytes_s, size_t len_s,
 963         const unsigned char *bytes_B, size_t len_B,
 964         unsigned char **bytes_M, size_t *len_M)
 965 {
 966         mpz_t B; mpz_init(B); mpz_from_bin(bytes_B, len_B, B);
 967         mpz_t u; mpz_init(u);
 968         mpz_t x; mpz_init(x);
 969         mpz_t k; mpz_init(k);
 970         mpz_t v; mpz_init(v);
 971         mpz_t tmp1; mpz_init(tmp1);
 972         mpz_t tmp2; mpz_init(tmp2);
 973         mpz_t tmp3; mpz_init(tmp3);
 974         mpz_t tmp4; mpz_init(tmp4);
 975         // clang-format on
 976
 977         *len_M = 0;
 978         *bytes_M = 0;
 979
 980         if (!H_nn(u, usr->hash_alg, usr->ng->N, usr->A, B)) goto cleanup_and_exit;
 981
 982         srp_dbg_num(u, "Client calculated u: ");
 983
 984         if (!calculate_x(x, usr->hash_alg, bytes_s, len_s, usr->username_verifier,
 985                         usr->password, usr->password_len))
 986                 goto cleanup_and_exit;
 987
 988         srp_dbg_num(x, "Client calculated x: ");
 989
 990         if (!H_nn(k, usr->hash_alg, usr->ng->N, usr->ng->N, usr->ng->g))
 991                 goto cleanup_and_exit;
 992
 993         /* SRP-6a safety check */
 994         if (mpz_sgn(B) != 0 && mpz_sgn(u) != 0) {
 995                 mpz_powm(v, usr->ng->g, x, usr->ng->N);
 996
 997                 srp_dbg_num(v, "Client calculated v: ");
 998
 999                 // clang-format off
1000                 /* S = (B - k*(g^x)) ^ (a + ux) */
1001                 mpz_mul(tmp1, u, x);
1002                 mpz_add(tmp2, usr->a, tmp1);               /* tmp2 = (a + ux)      */
1003                 mpz_powm(tmp1, usr->ng->g, x, usr->ng->N); /* tmp1 = g^x           */
1004                 mpz_mulm(tmp3, k, tmp1, usr->ng->N, tmp4); /* tmp3 = k*(g^x)       */
1005                 mpz_subm(tmp1, B, tmp3, usr->ng->N, tmp4); /* tmp1 = (B - K*(g^x)) */
1006                 mpz_powm(usr->S, tmp1, tmp2, usr->ng->N);
1007                 // clang-format on
1008
1009                 if (!hash_num(usr->hash_alg, usr->S, usr->session_key)) goto cleanup_and_exit;
1010
1011                 if (!calculate_M(usr->hash_alg, usr->ng, usr->M, usr->username, bytes_s, len_s,
1012                                 usr->A, B, usr->session_key))
1013                         goto cleanup_and_exit;
1014                 if (!calculate_H_AMK(usr->hash_alg, usr->H_AMK, usr->A, usr->M, usr->session_key))
1015                         goto cleanup_and_exit;
1016
1017                 *bytes_M = usr->M;
1018                 if (len_M) *len_M = hash_length(usr->hash_alg);
1019         } else {
1020                 *bytes_M = NULL;
1021                 if (len_M) *len_M = 0;
1022         }
1023
1024 cleanup_and_exit:
1025         mpz_clear(B);
1026         mpz_clear(u);
1027         mpz_clear(x);
1028         mpz_clear(k);
1029         mpz_clear(v);
1030         mpz_clear(tmp1);
1031         mpz_clear(tmp2);
1032         mpz_clear(tmp3);
1033         mpz_clear(tmp4);
1034 }
1035
1036 void srp_user_verify_session(struct SRPUser *usr, const unsigned char *bytes_HAMK)
1037 {
1038         if (memcmp(usr->H_AMK, bytes_HAMK, hash_length(usr->hash_alg)) == 0)
1039                 usr->authenticated = 1;
1040 }