release/src/router/openssl/crypto/jpake/jpake.c

   1 #include "jpake.h"
   2
   3 #include <openssl/crypto.h>
   4 #include <openssl/sha.h>
   5 #include <openssl/err.h>
   6 #include <memory.h>
   7 #include <string.h>
   8
   9 /*
  10  * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or
  11  * Bob's (x3, x4, x1, x2). If you see what I mean.
  12  */
  13
  14 typedef struct {
  15     char *name;                 /* Must be unique */
  16     char *peer_name;
  17     BIGNUM *p;
  18     BIGNUM *g;
  19     BIGNUM *q;
  20     BIGNUM *gxc;                /* Alice's g^{x3} or Bob's g^{x1} */
  21     BIGNUM *gxd;                /* Alice's g^{x4} or Bob's g^{x2} */
  22 } JPAKE_CTX_PUBLIC;
  23
  24 struct JPAKE_CTX {
  25     JPAKE_CTX_PUBLIC p;
  26     BIGNUM *secret;             /* The shared secret */
  27     BN_CTX *ctx;
  28     BIGNUM *xa;                 /* Alice's x1 or Bob's x3 */
  29     BIGNUM *xb;                 /* Alice's x2 or Bob's x4 */
  30     BIGNUM *key;                /* The calculated (shared) key */
  31 };
  32
  33 static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
  34 {
  35     zkp->gr = BN_new();
  36     zkp->b = BN_new();
  37 }
  38
  39 static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
  40 {
  41     BN_free(zkp->b);
  42     BN_free(zkp->gr);
  43 }
  44
  45 /* Two birds with one stone - make the global name as expected */
  46 #define JPAKE_STEP_PART_init    JPAKE_STEP2_init
  47 #define JPAKE_STEP_PART_release JPAKE_STEP2_release
  48
  49 void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
  50 {
  51     p->gx = BN_new();
  52     JPAKE_ZKP_init(&p->zkpx);
  53 }
  54
  55 void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
  56 {
  57     JPAKE_ZKP_release(&p->zkpx);
  58     BN_free(p->gx);
  59 }
  60
  61 void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
  62 {
  63     JPAKE_STEP_PART_init(&s1->p1);
  64     JPAKE_STEP_PART_init(&s1->p2);
  65 }
  66
  67 void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
  68 {
  69     JPAKE_STEP_PART_release(&s1->p2);
  70     JPAKE_STEP_PART_release(&s1->p1);
  71 }
  72
  73 static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name,
  74                            const char *peer_name, const BIGNUM *p,
  75                            const BIGNUM *g, const BIGNUM *q,
  76                            const BIGNUM *secret)
  77 {
  78     ctx->p.name = OPENSSL_strdup(name);
  79     ctx->p.peer_name = OPENSSL_strdup(peer_name);
  80     ctx->p.p = BN_dup(p);
  81     ctx->p.g = BN_dup(g);
  82     ctx->p.q = BN_dup(q);
  83     ctx->secret = BN_dup(secret);
  84
  85     ctx->p.gxc = BN_new();
  86     ctx->p.gxd = BN_new();
  87
  88     ctx->xa = BN_new();
  89     ctx->xb = BN_new();
  90     ctx->key = BN_new();
  91     ctx->ctx = BN_CTX_new();
  92 }
  93
  94 static void JPAKE_CTX_release(JPAKE_CTX *ctx)
  95 {
  96     BN_CTX_free(ctx->ctx);
  97     BN_clear_free(ctx->key);
  98     BN_clear_free(ctx->xb);
  99     BN_clear_free(ctx->xa);
 100
 101     BN_free(ctx->p.gxd);
 102     BN_free(ctx->p.gxc);
 103
 104     BN_clear_free(ctx->secret);
 105     BN_free(ctx->p.q);
 106     BN_free(ctx->p.g);
 107     BN_free(ctx->p.p);
 108     OPENSSL_free(ctx->p.peer_name);
 109     OPENSSL_free(ctx->p.name);
 110
 111     memset(ctx, '\0', sizeof *ctx);
 112 }
 113
 114 JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name,
 115                          const BIGNUM *p, const BIGNUM *g, const BIGNUM *q,
 116                          const BIGNUM *secret)
 117 {
 118     JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
 119
 120     JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
 121
 122     return ctx;
 123 }
 124
 125 void JPAKE_CTX_free(JPAKE_CTX *ctx)
 126 {
 127     JPAKE_CTX_release(ctx);
 128     OPENSSL_free(ctx);
 129 }
 130
 131 static void hashlength(SHA_CTX *sha, size_t l)
 132 {
 133     unsigned char b[2];
 134
 135     OPENSSL_assert(l <= 0xffff);
 136     b[0] = l >> 8;
 137     b[1] = l & 0xff;
 138     SHA1_Update(sha, b, 2);
 139 }
 140
 141 static void hashstring(SHA_CTX *sha, const char *string)
 142 {
 143     size_t l = strlen(string);
 144
 145     hashlength(sha, l);
 146     SHA1_Update(sha, string, l);
 147 }
 148
 149 static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
 150 {
 151     size_t l = BN_num_bytes(bn);
 152     unsigned char *bin = OPENSSL_malloc(l);
 153
 154     hashlength(sha, l);
 155     BN_bn2bin(bn, bin);
 156     SHA1_Update(sha, bin, l);
 157     OPENSSL_free(bin);
 158 }
 159
 160 /* h=hash(g, g^r, g^x, name) */
 161 static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
 162                      const char *proof_name)
 163 {
 164     unsigned char md[SHA_DIGEST_LENGTH];
 165     SHA_CTX sha;
 166
 167     /*
 168      * XXX: hash should not allow moving of the boundaries - Java code
 169      * is flawed in this respect. Length encoding seems simplest.
 170      */
 171     SHA1_Init(&sha);
 172     hashbn(&sha, zkpg);
 173     OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
 174     hashbn(&sha, p->zkpx.gr);
 175     hashbn(&sha, p->gx);
 176     hashstring(&sha, proof_name);
 177     SHA1_Final(md, &sha);
 178     BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
 179 }
 180
 181 /*
 182  * Prove knowledge of x
 183  * Note that p->gx has already been calculated
 184  */
 185 static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
 186                          const BIGNUM *zkpg, JPAKE_CTX *ctx)
 187 {
 188     BIGNUM *r = BN_new();
 189     BIGNUM *h = BN_new();
 190     BIGNUM *t = BN_new();
 191
 192    /*-
 193     * r in [0,q)
 194     * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
 195     */
 196     BN_rand_range(r, ctx->p.q);
 197     /* g^r */
 198     BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
 199
 200     /* h=hash... */
 201     zkp_hash(h, zkpg, p, ctx->p.name);
 202
 203     /* b = r - x*h */
 204     BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
 205     BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
 206
 207     /* cleanup */
 208     BN_free(t);
 209     BN_free(h);
 210     BN_free(r);
 211 }
 212
 213 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
 214                       JPAKE_CTX *ctx)
 215 {
 216     BIGNUM *h = BN_new();
 217     BIGNUM *t1 = BN_new();
 218     BIGNUM *t2 = BN_new();
 219     BIGNUM *t3 = BN_new();
 220     int ret = 0;
 221
 222     zkp_hash(h, zkpg, p, ctx->p.peer_name);
 223
 224     /* t1 = g^b */
 225     BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
 226     /* t2 = (g^x)^h = g^{hx} */
 227     BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
 228     /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
 229     BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
 230
 231     /* verify t3 == g^r */
 232     if (BN_cmp(t3, p->zkpx.gr) == 0)
 233         ret = 1;
 234     else
 235         JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
 236
 237     /* cleanup */
 238     BN_free(t3);
 239     BN_free(t2);
 240     BN_free(t1);
 241     BN_free(h);
 242
 243     return ret;
 244 }
 245
 246 static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
 247                                const BIGNUM *g, JPAKE_CTX *ctx)
 248 {
 249     BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
 250     generate_zkp(p, x, g, ctx);
 251 }
 252
 253 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
 254 static void genrand(JPAKE_CTX *ctx)
 255 {
 256     BIGNUM *qm1;
 257
 258     /* xa in [0, q) */
 259     BN_rand_range(ctx->xa, ctx->p.q);
 260
 261     /* q-1 */
 262     qm1 = BN_new();
 263     BN_copy(qm1, ctx->p.q);
 264     BN_sub_word(qm1, 1);
 265
 266     /* ... and xb in [0, q-1) */
 267     BN_rand_range(ctx->xb, qm1);
 268     /* [1, q) */
 269     BN_add_word(ctx->xb, 1);
 270
 271     /* cleanup */
 272     BN_free(qm1);
 273 }
 274
 275 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
 276 {
 277     genrand(ctx);
 278     generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
 279     generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
 280
 281     return 1;
 282 }
 283
 284 /* g^x is a legal value */
 285 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
 286 {
 287     BIGNUM *t;
 288     int res;
 289
 290     if (BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
 291         return 0;
 292
 293     t = BN_new();
 294     BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
 295     res = BN_is_one(t);
 296     BN_free(t);
 297
 298     return res;
 299 }
 300
 301 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
 302 {
 303     if (!is_legal(received->p1.gx, ctx)) {
 304         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
 305                  JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
 306         return 0;
 307     }
 308
 309     if (!is_legal(received->p2.gx, ctx)) {
 310         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
 311                  JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
 312         return 0;
 313     }
 314
 315     /* verify their ZKP(xc) */
 316     if (!verify_zkp(&received->p1, ctx->p.g, ctx)) {
 317         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
 318         return 0;
 319     }
 320
 321     /* verify their ZKP(xd) */
 322     if (!verify_zkp(&received->p2, ctx->p.g, ctx)) {
 323         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
 324         return 0;
 325     }
 326
 327     /* g^xd != 1 */
 328     if (BN_is_one(received->p2.gx)) {
 329         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
 330         return 0;
 331     }
 332
 333     /* Save the bits we need for later */
 334     BN_copy(ctx->p.gxc, received->p1.gx);
 335     BN_copy(ctx->p.gxd, received->p2.gx);
 336
 337     return 1;
 338 }
 339
 340 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
 341 {
 342     BIGNUM *t1 = BN_new();
 343     BIGNUM *t2 = BN_new();
 344
 345    /*-
 346     * X = g^{(xa + xc + xd) * xb * s}
 347     * t1 = g^xa
 348     */
 349     BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
 350     /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
 351     BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
 352     /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
 353     BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
 354     /* t2 = xb * s */
 355     BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
 356
 357    /*-
 358     * ZKP(xb * s)
 359     * XXX: this is kinda funky, because we're using
 360     *
 361     * g' = g^{xa + xc + xd}
 362     *
 363     * as the generator, which means X is g'^{xb * s}
 364     * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
 365     */
 366     generate_step_part(send, t2, t1, ctx);
 367
 368     /* cleanup */
 369     BN_free(t1);
 370     BN_free(t2);
 371
 372     return 1;
 373 }
 374
 375 /* gx = g^{xc + xa + xb} * xd * s */
 376 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
 377 {
 378     BIGNUM *t1 = BN_new();
 379     BIGNUM *t2 = BN_new();
 380     BIGNUM *t3 = BN_new();
 381
 382    /*-
 383     * K = (gx/g^{xb * xd * s})^{xb}
 384     *   = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
 385     *   = (g^{(xa + xc) * xd * s})^{xb}
 386     *   = g^{(xa + xc) * xb * xd * s}
 387     * [which is the same regardless of who calculates it]
 388     */
 389
 390     /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
 391     BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
 392     /* t2 = -s = q-s */
 393     BN_sub(t2, ctx->p.q, ctx->secret);
 394     /* t3 = t1^t2 = g^{-xb * xd * s} */
 395     BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
 396     /* t1 = gx * t3 = X/g^{xb * xd * s} */
 397     BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
 398     /* K = t1^{xb} */
 399     BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
 400
 401     /* cleanup */
 402     BN_free(t3);
 403     BN_free(t2);
 404     BN_free(t1);
 405
 406     return 1;
 407 }
 408
 409 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
 410 {
 411     BIGNUM *t1 = BN_new();
 412     BIGNUM *t2 = BN_new();
 413     int ret = 0;
 414
 415    /*-
 416     * g' = g^{xc + xa + xb} [from our POV]
 417     * t1 = xa + xb
 418     */
 419     BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
 420     /* t2 = g^{t1} = g^{xa+xb} */
 421     BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
 422     /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
 423     BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
 424
 425     if (verify_zkp(received, t1, ctx))
 426         ret = 1;
 427     else
 428         JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
 429
 430     compute_key(ctx, received->gx);
 431
 432     /* cleanup */
 433     BN_free(t2);
 434     BN_free(t1);
 435
 436     return ret;
 437 }
 438
 439 static void quickhashbn(unsigned char *md, const BIGNUM *bn)
 440 {
 441     SHA_CTX sha;
 442
 443     SHA1_Init(&sha);
 444     hashbn(&sha, bn);
 445     SHA1_Final(md, &sha);
 446 }
 447
 448 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
 449 {
 450 }
 451
 452 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
 453 {
 454     quickhashbn(send->hhk, ctx->key);
 455     SHA1(send->hhk, sizeof send->hhk, send->hhk);
 456
 457     return 1;
 458 }
 459
 460 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
 461 {
 462     unsigned char hhk[SHA_DIGEST_LENGTH];
 463
 464     quickhashbn(hhk, ctx->key);
 465     SHA1(hhk, sizeof hhk, hhk);
 466     if (memcmp(hhk, received->hhk, sizeof hhk)) {
 467         JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS,
 468                  JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
 469         return 0;
 470     }
 471     return 1;
 472 }
 473
 474 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
 475 {
 476 }
 477
 478 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
 479 {
 480 }
 481
 482 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
 483 {
 484     quickhashbn(send->hk, ctx->key);
 485
 486     return 1;
 487 }
 488
 489 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
 490 {
 491     unsigned char hk[SHA_DIGEST_LENGTH];
 492
 493     quickhashbn(hk, ctx->key);
 494     if (memcmp(hk, received->hk, sizeof hk)) {
 495         JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
 496         return 0;
 497     }
 498     return 1;
 499 }
 500
 501 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
 502 {
 503 }
 504
 505 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)
 506 {
 507     return ctx->key;
 508 }