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);
122 JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret);
127 void JPAKE_CTX_free(JPAKE_CTX *ctx)
129 JPAKE_CTX_release(ctx);
133 static void hashlength(SHA_CTX *sha, size_t l)
137 OPENSSL_assert(l <= 0xffff);
140 SHA1_Update(sha, b, 2);
143 static void hashstring(SHA_CTX *sha, const char *string)
145 size_t l = strlen(string);
148 SHA1_Update(sha, string, l);
151 static void hashbn(SHA_CTX *sha, const BIGNUM *bn)
153 size_t l = BN_num_bytes(bn);
154 unsigned char *bin = OPENSSL_malloc(l);
160 SHA1_Update(sha, bin, l);
164 /* h=hash(g, g^r, g^x, name) */
165 static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p,
166 const char *proof_name)
168 unsigned char md[SHA_DIGEST_LENGTH];
172 * XXX: hash should not allow moving of the boundaries - Java code
173 * is flawed in this respect. Length encoding seems simplest.
177 OPENSSL_assert(!BN_is_zero(p->zkpx.gr));
178 hashbn(&sha, p->zkpx.gr);
180 hashstring(&sha, proof_name);
181 SHA1_Final(md, &sha);
182 BN_bin2bn(md, SHA_DIGEST_LENGTH, h);
186 * Prove knowledge of x
187 * Note that p->gx has already been calculated
189 static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x,
190 const BIGNUM *zkpg, JPAKE_CTX *ctx)
192 BIGNUM *r = BN_new();
193 BIGNUM *h = BN_new();
194 BIGNUM *t = BN_new();
198 * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
200 BN_rand_range(r, ctx->p.q);
202 BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx);
205 zkp_hash(h, zkpg, p, ctx->p.name);
208 BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx);
209 BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx);
217 static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg,
220 BIGNUM *h = BN_new();
221 BIGNUM *t1 = BN_new();
222 BIGNUM *t2 = BN_new();
223 BIGNUM *t3 = BN_new();
226 if (h == NULL || t1 == NULL || t2 == NULL || t3 == NULL)
229 zkp_hash(h, zkpg, p, ctx->p.peer_name);
232 BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx);
233 /* t2 = (g^x)^h = g^{hx} */
234 BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx);
235 /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
236 BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx);
238 /* verify t3 == g^r */
239 if (BN_cmp(t3, p->zkpx.gr) == 0)
242 JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED);
254 static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x,
255 const BIGNUM *g, JPAKE_CTX *ctx)
257 BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx);
258 generate_zkp(p, x, g, ctx);
261 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
262 static void genrand(JPAKE_CTX *ctx)
267 BN_rand_range(ctx->xa, ctx->p.q);
271 BN_copy(qm1, ctx->p.q);
274 /* ... and xb in [0, q-1) */
275 BN_rand_range(ctx->xb, qm1);
277 BN_add_word(ctx->xb, 1);
283 int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx)
286 generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx);
287 generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx);
292 /* g^x is a legal value */
293 static int is_legal(const BIGNUM *gx, const JPAKE_CTX *ctx)
298 if (BN_is_negative(gx) || BN_is_zero(gx) || BN_cmp(gx, ctx->p.p) >= 0)
302 BN_mod_exp(t, gx, ctx->p.q, ctx->p.p, ctx->ctx);
309 int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received)
311 if (!is_legal(received->p1.gx, ctx)) {
312 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
313 JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL);
317 if (!is_legal(received->p2.gx, ctx)) {
318 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS,
319 JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL);
323 /* verify their ZKP(xc) */
324 if (!verify_zkp(&received->p1, ctx->p.g, ctx)) {
325 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED);
329 /* verify their ZKP(xd) */
330 if (!verify_zkp(&received->p2, ctx->p.g, ctx)) {
331 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED);
336 if (BN_is_one(received->p2.gx)) {
337 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE);
341 /* Save the bits we need for later */
342 BN_copy(ctx->p.gxc, received->p1.gx);
343 BN_copy(ctx->p.gxd, received->p2.gx);
348 int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx)
350 BIGNUM *t1 = BN_new();
351 BIGNUM *t2 = BN_new();
354 * X = g^{(xa + xc + xd) * xb * s}
357 BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx);
358 /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
359 BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx);
360 /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
361 BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx);
363 BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx);
367 * XXX: this is kinda funky, because we're using
369 * g' = g^{xa + xc + xd}
371 * as the generator, which means X is g'^{xb * s}
372 * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
374 generate_step_part(send, t2, t1, ctx);
383 /* gx = g^{xc + xa + xb} * xd * s */
384 static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx)
386 BIGNUM *t1 = BN_new();
387 BIGNUM *t2 = BN_new();
388 BIGNUM *t3 = BN_new();
391 * K = (gx/g^{xb * xd * s})^{xb}
392 * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
393 * = (g^{(xa + xc) * xd * s})^{xb}
394 * = g^{(xa + xc) * xb * xd * s}
395 * [which is the same regardless of who calculates it]
398 /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
399 BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx);
401 BN_sub(t2, ctx->p.q, ctx->secret);
402 /* t3 = t1^t2 = g^{-xb * xd * s} */
403 BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx);
404 /* t1 = gx * t3 = X/g^{xb * xd * s} */
405 BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx);
407 BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx);
417 int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received)
419 BIGNUM *t1 = BN_new();
420 BIGNUM *t2 = BN_new();
424 * g' = g^{xc + xa + xb} [from our POV]
427 BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx);
428 /* t2 = g^{t1} = g^{xa+xb} */
429 BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx);
430 /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
431 BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx);
433 if (verify_zkp(received, t1, ctx))
436 JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED);
438 compute_key(ctx, received->gx);
447 static void quickhashbn(unsigned char *md, const BIGNUM *bn)
453 SHA1_Final(md, &sha);
456 void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a)
460 int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx)
462 quickhashbn(send->hhk, ctx->key);
463 SHA1(send->hhk, sizeof send->hhk, send->hhk);
468 int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received)
470 unsigned char hhk[SHA_DIGEST_LENGTH];
472 quickhashbn(hhk, ctx->key);
473 SHA1(hhk, sizeof hhk, hhk);
474 if (memcmp(hhk, received->hhk, sizeof hhk)) {
475 JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS,
476 JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH);
482 void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a)
486 void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b)
490 int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx)
492 quickhashbn(send->hk, ctx->key);
497 int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received)
499 unsigned char hk[SHA_DIGEST_LENGTH];
501 quickhashbn(hk, ctx->key);
502 if (memcmp(hk, received->hk, sizeof hk)) {
503 JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH);
509 void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b)
513 const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx)