3 #include <openssl/crypto.h>
4 #include <openssl/sha.h>
5 #include <openssl/err.h>
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.
15 char *name; /* Must be unique */
20 BIGNUM *gxc; /* Alice's g^{x3} or Bob's g^{x1} */
21 BIGNUM *gxd; /* Alice's g^{x4} or Bob's g^{x2} */
27 BIGNUM *secret; /* The shared secret */
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 */
34 static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
40 static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
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
50 void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
53 JPAKE_ZKP_init(&p->zkpx);
56 void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
58 JPAKE_ZKP_release(&p->zkpx);
62 void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
64 JPAKE_STEP_PART_init(&s1->p1);
65 JPAKE_STEP_PART_init(&s1->p2);
68 void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
70 JPAKE_STEP_PART_release(&s1->p2);
71 JPAKE_STEP_PART_release(&s1->p1);
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,
79 ctx->p.name = OPENSSL_strdup(name);
80 ctx->p.peer_name = OPENSSL_strdup(peer_name);
84 ctx->secret = BN_dup(secret);
86 ctx->p.gxc = BN_new();
87 ctx->p.gxd = BN_new();
92 ctx->ctx = BN_CTX_new();
95 static void JPAKE_CTX_release(JPAKE_CTX *ctx)
97 BN_CTX_free(ctx->ctx);
98 BN_clear_free(ctx->key);
99 BN_clear_free(ctx->xb);
100 BN_clear_free(ctx->xa);
105 BN_clear_free(ctx->secret);
109 OPENSSL_free(ctx->p.peer_name);
110 OPENSSL_free(ctx->p.name);
112 memset(ctx, '\0', sizeof *ctx);
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)
119 JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
123 JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
128 void JPAKE_CTX_free(JPAKE_CTX *ctx)
130 JPAKE_CTX_release(ctx);
134 static void hashlength(SHA_CTX *sha, size_t l)
138 OPENSSL_assert(l <= 0xffff);
141 SHA1_Update(sha, b, 2);
144 static void hashstring(SHA_CTX *sha, const char *string)
146 size_t l = strlen(string);
149 SHA1_Update(sha, string, l);
152 static int hashbn(SHA_CTX *sha, const BIGNUM *bn)
154 size_t l = BN_num_bytes(bn);
155 unsigned char *bin = OPENSSL_malloc(l);
162 SHA1_Update(sha, bin, l);
167 /* h=hash(g, g^r, g^x, name) */
168 static int zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
169 const char *proof_name)
171 unsigned char md[SHA_DIGEST_LENGTH];
175 * XXX: hash should not allow moving of the boundaries - Java code
176 * is flawed in this respect. Length encoding seems simplest.
179 if (!hashbn(&sha, zkpg))
181 OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
182 if (!hashbn(&sha, p->zkpx.gr))
184 if (!hashbn(&sha, p->gx))
186 hashstring(&sha, proof_name);
187 SHA1_Final(md, &sha);
188 BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
193 * Prove knowledge of x
194 * Note that p->gx has already been calculated
196 static int generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
197 const BIGNUM *zkpg, JPAKE_CTX *ctx)
200 BIGNUM *r = BN_new();
201 BIGNUM *h = BN_new();
202 BIGNUM *t = BN_new();
206 * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
208 BN_rand_range(r, ctx->p.q);
210 BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
213 if (!zkp_hash(h, zkpg, p, ctx->p.name))
217 BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
218 BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
229 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
232 BIGNUM *h = BN_new();
233 BIGNUM *t1 = BN_new();
234 BIGNUM *t2 = BN_new();
235 BIGNUM *t3 = BN_new();
238 if (!zkp_hash(h, zkpg, p, ctx->p.peer_name))
242 BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
243 /* t2 = (g^x)^h = g^{hx} */
244 BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
245 /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
246 BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
248 /* verify t3 == g^r */
249 if(BN_cmp(t3, p->zkpx.gr) == 0)
252 JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
264 static int generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
265 const BIGNUM *g, JPAKE_CTX *ctx)
267 BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
268 if (!generate_zkp(p, x, g, ctx))
273 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
274 static void genrand(JPAKE_CTX *ctx)
279 BN_rand_range(ctx->xa, ctx->p.q);
283 BN_copy(qm1, ctx->p.q);
286 /* ... and xb in [0, q-1) */
287 BN_rand_range(ctx->xb, qm1);
289 BN_add_word(ctx->xb, 1);
295 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
298 if (!generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx))
300 if (!generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx))
306 /* g^x is a legal value */
307 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
312 if(BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
316 BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
323 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
325 if(!is_legal(received->p1.gx, ctx))
327 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
331 if(!is_legal(received->p2.gx, ctx))
333 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
337 /* verify their ZKP(xc) */
338 if(!verify_zkp(&received->p1, ctx->p.g, ctx))
340 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
344 /* verify their ZKP(xd) */
345 if(!verify_zkp(&received->p2, ctx->p.g, ctx))
347 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
352 if(BN_is_one(received->p2.gx))
354 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
358 /* Save the bits we need for later */
359 BN_copy(ctx->p.gxc, received->p1.gx);
360 BN_copy(ctx->p.gxd, received->p2.gx);
366 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
370 BIGNUM *t1 = BN_new();
371 BIGNUM *t2 = BN_new();
374 * X = g^{(xa + xc + xd) * xb * s}
377 BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
378 /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
379 BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
380 /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
381 BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
383 BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
387 * XXX: this is kinda funky, because we're using
389 * g' = g^{xa + xc + xd}
391 * as the generator, which means X is g'^{xb * s}
392 * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
394 ret = generate_step_part(send, t2, t1, ctx);
403 /* gx = g^{xc + xa + xb} * xd * s */
404 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
406 BIGNUM *t1 = BN_new();
407 BIGNUM *t2 = BN_new();
408 BIGNUM *t3 = BN_new();
411 * K = (gx/g^{xb * xd * s})^{xb}
412 * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
413 * = (g^{(xa + xc) * xd * s})^{xb}
414 * = g^{(xa + xc) * xb * xd * s}
415 * [which is the same regardless of who calculates it]
418 /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
419 BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
421 BN_sub(t2, ctx->p.q, ctx->secret);
422 /* t3 = t1^t2 = g^{-xb * xd * s} */
423 BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
424 /* t1 = gx * t3 = X/g^{xb * xd * s} */
425 BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
427 BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
437 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
439 BIGNUM *t1 = BN_new();
440 BIGNUM *t2 = BN_new();
444 * g' = g^{xc + xa + xb} [from our POV]
447 BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
448 /* t2 = g^{t1} = g^{xa+xb} */
449 BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
450 /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
451 BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
453 if(verify_zkp(received, t1, ctx))
456 JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
458 compute_key(ctx, received->gx);
467 static int quickhashbn(unsigned char *md, const BIGNUM *bn)
472 if (!hashbn(&sha, bn))
474 SHA1_Final(md, &sha);
478 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
481 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
483 if (!quickhashbn(send->hhk, ctx->key))
485 SHA1(send->hhk, sizeof send->hhk, send->hhk);
490 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
492 unsigned char hhk[SHA_DIGEST_LENGTH];
494 if (!quickhashbn(hhk, ctx->key))
496 SHA1(hhk, sizeof hhk, hhk);
497 if(memcmp(hhk, received->hhk, sizeof hhk))
499 JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
505 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
508 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
511 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
513 if (!quickhashbn(send->hk, ctx->key))
518 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
520 unsigned char hk[SHA_DIGEST_LENGTH];
522 if (!quickhashbn(hk, ctx->key))
524 if(memcmp(hk, received->hk, sizeof hk))
526 JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
532 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
535 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)