3 #include <openssl/crypto.h>
4 #include <openssl/sha.h>
5 #include <openssl/err.h>
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.
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} */
26 BIGNUM *secret; /* The shared secret */
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 */
33 static void JPAKE_ZKP_init(JPAKE_ZKP *zkp)
39 static void JPAKE_ZKP_release(JPAKE_ZKP *zkp)
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
49 void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p)
52 JPAKE_ZKP_init(&p->zkpx);
55 void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p)
57 JPAKE_ZKP_release(&p->zkpx);
61 void JPAKE_STEP1_init(JPAKE_STEP1 *s1)
63 JPAKE_STEP_PART_init(&s1->p1);
64 JPAKE_STEP_PART_init(&s1->p2);
67 void JPAKE_STEP1_release(JPAKE_STEP1 *s1)
69 JPAKE_STEP_PART_release(&s1->p2);
70 JPAKE_STEP_PART_release(&s1->p1);
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,
78 ctx->p.name = OPENSSL_strdup(name);
79 ctx->p.peer_name = OPENSSL_strdup(peer_name);
83 ctx->secret = BN_dup(secret);
85 ctx->p.gxc = BN_new();
86 ctx->p.gxd = BN_new();
91 ctx->ctx = BN_CTX_new();
94 static void JPAKE_CTX_release(JPAKE_CTX *ctx)
96 BN_CTX_free(ctx->ctx);
97 BN_clear_free(ctx->key);
98 BN_clear_free(ctx->xb);
99 BN_clear_free(ctx->xa);
104 BN_clear_free(ctx->secret);
108 OPENSSL_free(ctx->p.peer_name);
109 OPENSSL_free(ctx->p.name);
111 memset(ctx, '\0', sizeof *ctx);
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)
118 JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx);
120 JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
125 void JPAKE_CTX_free(JPAKE_CTX *ctx)
127 JPAKE_CTX_release(ctx);
131 static void hashlength(SHA_CTX *sha, size_t l)
135 OPENSSL_assert(l <= 0xffff);
138 SHA1_Update(sha, b, 2);
141 static void hashstring(SHA_CTX *sha, const char *string)
143 size_t l = strlen(string);
146 SHA1_Update(sha, string, l);
149 static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
151 size_t l = BN_num_bytes(bn);
152 unsigned char *bin = OPENSSL_malloc(l);
156 SHA1_Update(sha, bin, l);
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)
164 unsigned char md[SHA_DIGEST_LENGTH];
168 * XXX: hash should not allow moving of the boundaries - Java code
169 * is flawed in this respect. Length encoding seems simplest.
173 OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
174 hashbn(&sha, p->zkpx.gr);
176 hashstring(&sha, proof_name);
177 SHA1_Final(md, &sha);
178 BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
182 * Prove knowledge of x
183 * Note that p->gx has already been calculated
185 static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
186 const BIGNUM *zkpg, JPAKE_CTX *ctx)
188 BIGNUM *r = BN_new();
189 BIGNUM *h = BN_new();
190 BIGNUM *t = BN_new();
194 * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
196 BN_rand_range(r, ctx->p.q);
198 BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
201 zkp_hash(h, zkpg, p, ctx->p.name);
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);
213 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
216 BIGNUM *h = BN_new();
217 BIGNUM *t1 = BN_new();
218 BIGNUM *t2 = BN_new();
219 BIGNUM *t3 = BN_new();
222 if (h == NULL || t1 == NULL || t2 == NULL || t3 == NULL)
225 zkp_hash(h, zkpg, p, ctx->p.peer_name);
228 BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
229 /* t2 = (g^x)^h = g^{hx} */
230 BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
231 /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
232 BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
234 /* verify t3 == g^r */
235 if (BN_cmp(t3, p->zkpx.gr) == 0)
238 JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
250 static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
251 const BIGNUM *g, JPAKE_CTX *ctx)
253 BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
254 generate_zkp(p, x, g, ctx);
257 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
258 static void genrand(JPAKE_CTX *ctx)
263 BN_rand_range(ctx->xa, ctx->p.q);
267 BN_copy(qm1, ctx->p.q);
270 /* ... and xb in [0, q-1) */
271 BN_rand_range(ctx->xb, qm1);
273 BN_add_word(ctx->xb, 1);
279 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
282 generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
283 generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
288 /* g^x is a legal value */
289 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
294 if (BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
298 BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
305 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
307 if (!is_legal(received->p1.gx, ctx)) {
308 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
309 JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
313 if (!is_legal(received->p2.gx, ctx)) {
314 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
315 JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
319 /* verify their ZKP(xc) */
320 if (!verify_zkp(&received->p1, ctx->p.g, ctx)) {
321 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
325 /* verify their ZKP(xd) */
326 if (!verify_zkp(&received->p2, ctx->p.g, ctx)) {
327 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
332 if (BN_is_one(received->p2.gx)) {
333 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
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);
344 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
346 BIGNUM *t1 = BN_new();
347 BIGNUM *t2 = BN_new();
350 * X = g^{(xa + xc + xd) * xb * s}
353 BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
354 /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
355 BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
356 /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
357 BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
359 BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
363 * XXX: this is kinda funky, because we're using
365 * g' = g^{xa + xc + xd}
367 * as the generator, which means X is g'^{xb * s}
368 * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
370 generate_step_part(send, t2, t1, ctx);
379 /* gx = g^{xc + xa + xb} * xd * s */
380 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
382 BIGNUM *t1 = BN_new();
383 BIGNUM *t2 = BN_new();
384 BIGNUM *t3 = BN_new();
387 * K = (gx/g^{xb * xd * s})^{xb}
388 * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
389 * = (g^{(xa + xc) * xd * s})^{xb}
390 * = g^{(xa + xc) * xb * xd * s}
391 * [which is the same regardless of who calculates it]
394 /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
395 BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
397 BN_sub(t2, ctx->p.q, ctx->secret);
398 /* t3 = t1^t2 = g^{-xb * xd * s} */
399 BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
400 /* t1 = gx * t3 = X/g^{xb * xd * s} */
401 BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
403 BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
413 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
415 BIGNUM *t1 = BN_new();
416 BIGNUM *t2 = BN_new();
420 * g' = g^{xc + xa + xb} [from our POV]
423 BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
424 /* t2 = g^{t1} = g^{xa+xb} */
425 BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
426 /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
427 BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
429 if (verify_zkp(received, t1, ctx))
432 JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
434 compute_key(ctx, received->gx);
443 static void quickhashbn(unsigned char *md, const BIGNUM *bn)
449 SHA1_Final(md, &sha);
452 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
456 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
458 quickhashbn(send->hhk, ctx->key);
459 SHA1(send->hhk, sizeof send->hhk, send->hhk);
464 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
466 unsigned char hhk[SHA_DIGEST_LENGTH];
468 quickhashbn(hhk, ctx->key);
469 SHA1(hhk, sizeof hhk, hhk);
470 if (memcmp(hhk, received->hhk, sizeof hhk)) {
471 JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS,
472 JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
478 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
482 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
486 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
488 quickhashbn(send->hk, ctx->key);
493 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
495 unsigned char hk[SHA_DIGEST_LENGTH];
497 quickhashbn(hk, ctx->key);
498 if (memcmp(hk, received->hk, sizeof hk)) {
499 JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
505 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
509 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)