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
   8 /*
   9  * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or
  10  * Bob's (x3, x4, x1, x2). If you see what I mean.
  11  */
  12
  13 typedef struct
  14     {
  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     {
  26     JPAKE_CTX_PUBLIC p;
  27     BIGNUM *secret;   /* The shared secret */
  28     BN_CTX *ctx;
  29     BIGNUM *xa;       /* Alice's x1 or Bob's x3 */
  30     BIGNUM *xb;       /* Alice's x2 or Bob's x4 */
  31     BIGNUM *key;      /* The calculated (shared) key */
  32     };
  33
  34 static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
  35     {
  36     zkp->gr = BN_new();
  37     zkp->b = BN_new();
  38     }
  39
  40 static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
  41     {
  42     BN_free(zkp->b);
  43     BN_free(zkp->gr);
  44     }
  45
  46 /* Two birds with one stone - make the global name as expected */
  47 #define JPAKE_STEP_PART_init    JPAKE_STEP2_init
  48 #define JPAKE_STEP_PART_release JPAKE_STEP2_release
  49
  50 void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
  51     {
  52     p->gx = BN_new();
  53     JPAKE_ZKP_init(&p->zkpx);
  54     }
  55
  56 void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
  57     {
  58     JPAKE_ZKP_release(&p->zkpx);
  59     BN_free(p->gx);
  60     }
  61
  62 void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
  63     {
  64     JPAKE_STEP_PART_init(&s1->p1);
  65     JPAKE_STEP_PART_init(&s1->p2);
  66     }
  67
  68 void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
  69     {
  70     JPAKE_STEP_PART_release(&s1->p2);
  71     JPAKE_STEP_PART_release(&s1->p1);
  72     }
  73
  74 static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name,
  75                            const char *peer_name, const BIGNUM *p,
  76                            const BIGNUM *g, const BIGNUM *q,
  77                            const BIGNUM *secret)
  78     {
  79     ctx->p.name = OPENSSL_strdup(name);
  80     ctx->p.peer_name = OPENSSL_strdup(peer_name);
  81     ctx->p.p = BN_dup(p);
  82     ctx->p.g = BN_dup(g);
  83     ctx->p.q = BN_dup(q);
  84     ctx->secret = BN_dup(secret);
  85
  86     ctx->p.gxc = BN_new();
  87     ctx->p.gxd = BN_new();
  88
  89     ctx->xa = BN_new();
  90     ctx->xb = BN_new();
  91     ctx->key = BN_new();
  92     ctx->ctx = BN_CTX_new();
  93     }
  94
  95 static void JPAKE_CTX_release(JPAKE_CTX *ctx)
  96     {
  97     BN_CTX_free(ctx->ctx);
  98     BN_clear_free(ctx->key);
  99     BN_clear_free(ctx->xb);
 100     BN_clear_free(ctx->xa);
 101
 102     BN_free(ctx->p.gxd);
 103     BN_free(ctx->p.gxc);
 104
 105     BN_clear_free(ctx->secret);
 106     BN_free(ctx->p.q);
 107     BN_free(ctx->p.g);
 108     BN_free(ctx->p.p);
 109     OPENSSL_free(ctx->p.peer_name);
 110     OPENSSL_free(ctx->p.name);
 111
 112     memset(ctx, '\0', sizeof *ctx);
 113     }
 114
 115 JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name,
 116                          const BIGNUM *p, const BIGNUM *g, const BIGNUM *q,
 117                          const BIGNUM *secret)
 118     {
 119     JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
 120
 121     JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
 122
 123     return ctx;
 124     }
 125
 126 void JPAKE_CTX_free(JPAKE_CTX *ctx)
 127     {
 128     JPAKE_CTX_release(ctx);
 129     OPENSSL_free(ctx);
 130     }
 131
 132 static void hashlength(SHA_CTX *sha, size_t l)
 133     {
 134     unsigned char b[2];
 135
 136     OPENSSL_assert(l <= 0xffff);
 137     b[0] = l >> 8;
 138     b[1] = l&0xff;
 139     SHA1_Update(sha, b, 2);
 140     }
 141
 142 static void hashstring(SHA_CTX *sha, const char *string)
 143     {
 144     size_t l = strlen(string);
 145
 146     hashlength(sha, l);
 147     SHA1_Update(sha, string, l);
 148     }
 149
 150 static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
 151     {
 152     size_t l = BN_num_bytes(bn);
 153     unsigned char *bin = OPENSSL_malloc(l);
 154
 155     hashlength(sha, l);
 156     BN_bn2bin(bn, bin);
 157     SHA1_Update(sha, bin, l);
 158     OPENSSL_free(bin);
 159     }
 160
 161 /* h=hash(g, g^r, g^x, name) */
 162 static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
 163                      const char *proof_name)
 164     {
 165     unsigned char md[SHA_DIGEST_LENGTH];
 166     SHA_CTX sha;
 167
 168    /*
 169     * XXX: hash should not allow moving of the boundaries - Java code
 170     * is flawed in this respect. Length encoding seems simplest.
 171     */
 172     SHA1_Init(&sha);
 173     hashbn(&sha, zkpg);
 174     OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
 175     hashbn(&sha, p->zkpx.gr);
 176     hashbn(&sha, p->gx);
 177     hashstring(&sha, proof_name);
 178     SHA1_Final(md, &sha);
 179     BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
 180     }
 181
 182 /*
 183  * Prove knowledge of x
 184  * Note that p->gx has already been calculated
 185  */
 186 static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
 187                          const BIGNUM *zkpg, JPAKE_CTX *ctx)
 188     {
 189     BIGNUM *r = BN_new();
 190     BIGNUM *h = BN_new();
 191     BIGNUM *t = BN_new();
 192
 193    /*
 194     * r in [0,q)
 195     * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
 196     */
 197     BN_rand_range(r, ctx->p.q);
 198    /* g^r */
 199     BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
 200
 201    /* h=hash... */
 202     zkp_hash(h, zkpg, p, ctx->p.name);
 203
 204    /* b = r - x*h */
 205     BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
 206     BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
 207
 208    /* cleanup */
 209     BN_free(t);
 210     BN_free(h);
 211     BN_free(r);
 212     }
 213
 214 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
 215                       JPAKE_CTX *ctx)
 216     {
 217     BIGNUM *h = BN_new();
 218     BIGNUM *t1 = BN_new();
 219     BIGNUM *t2 = BN_new();
 220     BIGNUM *t3 = BN_new();
 221     int ret = 0;
 222
 223     zkp_hash(h, zkpg, p, ctx->p.peer_name);
 224
 225    /* t1 = g^b */
 226     BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
 227    /* t2 = (g^x)^h = g^{hx} */
 228     BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
 229    /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
 230     BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
 231
 232    /* verify t3 == g^r */
 233     if(BN_cmp(t3, p->zkpx.gr) == 0)
 234         ret = 1;
 235     else
 236         JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
 237
 238    /* cleanup */
 239     BN_free(t3);
 240     BN_free(t2);
 241     BN_free(t1);
 242     BN_free(h);
 243
 244     return ret;
 245     }
 246
 247 static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
 248                                const BIGNUM *g, JPAKE_CTX *ctx)
 249     {
 250     BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
 251     generate_zkp(p, x, g, ctx);
 252     }
 253
 254 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
 255 static void genrand(JPAKE_CTX *ctx)
 256     {
 257     BIGNUM *qm1;
 258
 259    /* xa in [0, q) */
 260     BN_rand_range(ctx->xa, ctx->p.q);
 261
 262    /* q-1 */
 263     qm1 = BN_new();
 264     BN_copy(qm1, ctx->p.q);
 265     BN_sub_word(qm1, 1);
 266
 267    /* ... and xb in [0, q-1) */
 268     BN_rand_range(ctx->xb, qm1);
 269    /* [1, q) */
 270     BN_add_word(ctx->xb, 1);
 271
 272    /* cleanup */
 273     BN_free(qm1);
 274     }
 275
 276 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
 277     {
 278     genrand(ctx);
 279     generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
 280     generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
 281
 282     return 1;
 283     }
 284
 285 /* g^x is a legal value */
 286 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
 287     {
 288     BIGNUM *t;
 289     int res;
 290
 291     if(BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
 292         return 0;
 293
 294     t = BN_new();
 295     BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
 296     res = BN_is_one(t);
 297     BN_free(t);
 298
 299     return res;
 300     }
 301
 302 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
 303     {
 304     if(!is_legal(received->p1.gx, ctx))
 305         {
 306         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
 307         return 0;
 308         }
 309
 310     if(!is_legal(received->p2.gx, ctx))
 311         {
 312         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
 313         return 0;
 314         }
 315
 316    /* verify their ZKP(xc) */
 317     if(!verify_zkp(&received->p1, ctx->p.g, ctx))
 318         {
 319         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
 320         return 0;
 321         }
 322
 323    /* verify their ZKP(xd) */
 324     if(!verify_zkp(&received->p2, ctx->p.g, ctx))
 325         {
 326         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
 327         return 0;
 328         }
 329
 330    /* g^xd != 1 */
 331     if(BN_is_one(received->p2.gx))
 332         {
 333         JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
 334         return 0;
 335         }
 336
 337    /* Save the bits we need for later */
 338     BN_copy(ctx->p.gxc, received->p1.gx);
 339     BN_copy(ctx->p.gxd, received->p2.gx);
 340
 341     return 1;
 342     }
 343
 344
 345 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
 346     {
 347     BIGNUM *t1 = BN_new();
 348     BIGNUM *t2 = BN_new();
 349
 350    /*
 351     * X = g^{(xa + xc + xd) * xb * s}
 352     * t1 = g^xa
 353     */
 354     BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
 355    /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
 356     BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
 357    /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
 358     BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
 359    /* t2 = xb * s */
 360     BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
 361
 362    /*
 363     * ZKP(xb * s)
 364     * XXX: this is kinda funky, because we're using
 365     *
 366     * g' = g^{xa + xc + xd}
 367     *
 368     * as the generator, which means X is g'^{xb * s}
 369     * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
 370     */
 371     generate_step_part(send, t2, t1, ctx);
 372
 373    /* cleanup */
 374     BN_free(t1);
 375     BN_free(t2);
 376
 377     return 1;
 378     }
 379
 380 /* gx = g^{xc + xa + xb} * xd * s */
 381 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
 382     {
 383     BIGNUM *t1 = BN_new();
 384     BIGNUM *t2 = BN_new();
 385     BIGNUM *t3 = BN_new();
 386
 387    /*
 388     * K = (gx/g^{xb * xd * s})^{xb}
 389     *   = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
 390     *   = (g^{(xa + xc) * xd * s})^{xb}
 391     *   = g^{(xa + xc) * xb * xd * s}
 392     * [which is the same regardless of who calculates it]
 393     */
 394
 395    /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
 396     BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
 397    /* t2 = -s = q-s */
 398     BN_sub(t2, ctx->p.q, ctx->secret);
 399    /* t3 = t1^t2 = g^{-xb * xd * s} */
 400     BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
 401    /* t1 = gx * t3 = X/g^{xb * xd * s} */
 402     BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
 403    /* K = t1^{xb} */
 404     BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
 405
 406    /* cleanup */
 407     BN_free(t3);
 408     BN_free(t2);
 409     BN_free(t1);
 410
 411     return 1;
 412     }
 413
 414 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
 415     {
 416     BIGNUM *t1 = BN_new();
 417     BIGNUM *t2 = BN_new();
 418     int ret = 0;
 419
 420    /*
 421     * g' = g^{xc + xa + xb} [from our POV]
 422     * t1 = xa + xb
 423     */
 424     BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
 425    /* t2 = g^{t1} = g^{xa+xb} */
 426     BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
 427    /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
 428     BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
 429
 430     if(verify_zkp(received, t1, ctx))
 431         ret = 1;
 432     else
 433         JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
 434
 435     compute_key(ctx, received->gx);
 436
 437    /* cleanup */
 438     BN_free(t2);
 439     BN_free(t1);
 440
 441     return ret;
 442     }
 443
 444 static void quickhashbn(unsigned char *md, const BIGNUM *bn)
 445     {
 446     SHA_CTX sha;
 447
 448     SHA1_Init(&sha);
 449     hashbn(&sha, bn);
 450     SHA1_Final(md, &sha);
 451     }
 452
 453 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
 454     {}
 455
 456 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
 457     {
 458     quickhashbn(send->hhk, ctx->key);
 459     SHA1(send->hhk, sizeof send->hhk, send->hhk);
 460
 461     return 1;
 462     }
 463
 464 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
 465     {
 466     unsigned char hhk[SHA_DIGEST_LENGTH];
 467
 468     quickhashbn(hhk, ctx->key);
 469     SHA1(hhk, sizeof hhk, hhk);
 470     if(memcmp(hhk, received->hhk, sizeof hhk))
 471         {
 472         JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
 473         return 0;
 474         }
 475     return 1;
 476     }
 477
 478 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
 479     {}
 480
 481 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
 482     {}
 483
 484 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
 485     {
 486     quickhashbn(send->hk, ctx->key);
 487
 488     return 1;
 489     }
 490
 491 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
 492     {
 493     unsigned char hk[SHA_DIGEST_LENGTH];
 494
 495     quickhashbn(hk, ctx->key);
 496     if(memcmp(hk, received->hk, sizeof hk))
 497         {
 498         JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
 499         return 0;
 500         }
 501     return 1;
 502     }
 503
 504 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
 505     {}
 506
 507 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)
 508     {
 509     return ctx->key;
 510     }
 511