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.
16 char *name
; /* Must be unique */
21 BIGNUM
*gxc
; /* Alice's g^{x3} or Bob's g^{x1} */
22 BIGNUM
*gxd
; /* Alice's g^{x4} or Bob's g^{x2} */
28 BIGNUM
*secret
; /* The shared secret */
30 BIGNUM
*xa
; /* Alice's x1 or Bob's x3 */
31 BIGNUM
*xb
; /* Alice's x2 or Bob's x4 */
32 BIGNUM
*key
; /* The calculated (shared) key */
35 static void JPAKE_ZKP_init(JPAKE_ZKP
*zkp
)
41 static void JPAKE_ZKP_release(JPAKE_ZKP
*zkp
)
47 /* Two birds with one stone - make the global name as expected */
48 #define JPAKE_STEP_PART_init JPAKE_STEP2_init
49 #define JPAKE_STEP_PART_release JPAKE_STEP2_release
51 void JPAKE_STEP_PART_init(JPAKE_STEP_PART
*p
)
54 JPAKE_ZKP_init(&p
->zkpx
);
57 void JPAKE_STEP_PART_release(JPAKE_STEP_PART
*p
)
59 JPAKE_ZKP_release(&p
->zkpx
);
63 void JPAKE_STEP1_init(JPAKE_STEP1
*s1
)
65 JPAKE_STEP_PART_init(&s1
->p1
);
66 JPAKE_STEP_PART_init(&s1
->p2
);
69 void JPAKE_STEP1_release(JPAKE_STEP1
*s1
)
71 JPAKE_STEP_PART_release(&s1
->p2
);
72 JPAKE_STEP_PART_release(&s1
->p1
);
75 static void JPAKE_CTX_init(JPAKE_CTX
*ctx
, const char *name
,
76 const char *peer_name
, const BIGNUM
*p
,
77 const BIGNUM
*g
, const BIGNUM
*q
,
80 ctx
->p
.name
= OPENSSL_strdup(name
);
81 ctx
->p
.peer_name
= OPENSSL_strdup(peer_name
);
85 ctx
->secret
= BN_dup(secret
);
87 ctx
->p
.gxc
= BN_new();
88 ctx
->p
.gxd
= BN_new();
93 ctx
->ctx
= BN_CTX_new();
96 static void JPAKE_CTX_release(JPAKE_CTX
*ctx
)
98 BN_CTX_free(ctx
->ctx
);
99 BN_clear_free(ctx
->key
);
100 BN_clear_free(ctx
->xb
);
101 BN_clear_free(ctx
->xa
);
106 BN_clear_free(ctx
->secret
);
110 OPENSSL_free(ctx
->p
.peer_name
);
111 OPENSSL_free(ctx
->p
.name
);
113 memset(ctx
, '\0', sizeof *ctx
);
116 JPAKE_CTX
*JPAKE_CTX_new(const char *name
, const char *peer_name
,
117 const BIGNUM
*p
, const BIGNUM
*g
, const BIGNUM
*q
,
118 const BIGNUM
*secret
)
120 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
);
158 SHA1_Update(sha
, bin
, l
);
162 /* h=hash(g, g^r, g^x, name) */
163 static void zkp_hash(BIGNUM
*h
, const BIGNUM
*zkpg
, const JPAKE_STEP_PART
*p
,
164 const char *proof_name
)
166 unsigned char md
[SHA_DIGEST_LENGTH
];
170 * XXX: hash should not allow moving of the boundaries - Java code
171 * is flawed in this respect. Length encoding seems simplest.
175 OPENSSL_assert(!BN_is_zero(p
->zkpx
.gr
));
176 hashbn(&sha
, p
->zkpx
.gr
);
178 hashstring(&sha
, proof_name
);
179 SHA1_Final(md
, &sha
);
180 BN_bin2bn(md
, SHA_DIGEST_LENGTH
, h
);
184 * Prove knowledge of x
185 * Note that p->gx has already been calculated
187 static void generate_zkp(JPAKE_STEP_PART
*p
, const BIGNUM
*x
,
188 const BIGNUM
*zkpg
, JPAKE_CTX
*ctx
)
190 BIGNUM
*r
= BN_new();
191 BIGNUM
*h
= BN_new();
192 BIGNUM
*t
= BN_new();
196 * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform
198 BN_rand_range(r
, ctx
->p
.q
);
200 BN_mod_exp(p
->zkpx
.gr
, zkpg
, r
, ctx
->p
.p
, ctx
->ctx
);
203 zkp_hash(h
, zkpg
, p
, ctx
->p
.name
);
206 BN_mod_mul(t
, x
, h
, ctx
->p
.q
, ctx
->ctx
);
207 BN_mod_sub(p
->zkpx
.b
, r
, t
, ctx
->p
.q
, ctx
->ctx
);
215 static int verify_zkp(const JPAKE_STEP_PART
*p
, const BIGNUM
*zkpg
,
218 BIGNUM
*h
= BN_new();
219 BIGNUM
*t1
= BN_new();
220 BIGNUM
*t2
= BN_new();
221 BIGNUM
*t3
= BN_new();
224 zkp_hash(h
, zkpg
, p
, ctx
->p
.peer_name
);
227 BN_mod_exp(t1
, zkpg
, p
->zkpx
.b
, ctx
->p
.p
, ctx
->ctx
);
228 /* t2 = (g^x)^h = g^{hx} */
229 BN_mod_exp(t2
, p
->gx
, h
, ctx
->p
.p
, ctx
->ctx
);
230 /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */
231 BN_mod_mul(t3
, t1
, t2
, ctx
->p
.p
, ctx
->ctx
);
233 /* verify t3 == g^r */
234 if(BN_cmp(t3
, p
->zkpx
.gr
) == 0)
237 JPAKEerr(JPAKE_F_VERIFY_ZKP
, JPAKE_R_ZKP_VERIFY_FAILED
);
248 static void generate_step_part(JPAKE_STEP_PART
*p
, const BIGNUM
*x
,
249 const BIGNUM
*g
, JPAKE_CTX
*ctx
)
251 BN_mod_exp(p
->gx
, g
, x
, ctx
->p
.p
, ctx
->ctx
);
252 generate_zkp(p
, x
, g
, ctx
);
255 /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */
256 static void genrand(JPAKE_CTX
*ctx
)
261 BN_rand_range(ctx
->xa
, ctx
->p
.q
);
265 BN_copy(qm1
, ctx
->p
.q
);
268 /* ... and xb in [0, q-1) */
269 BN_rand_range(ctx
->xb
, qm1
);
271 BN_add_word(ctx
->xb
, 1);
277 int JPAKE_STEP1_generate(JPAKE_STEP1
*send
, JPAKE_CTX
*ctx
)
280 generate_step_part(&send
->p1
, ctx
->xa
, ctx
->p
.g
, ctx
);
281 generate_step_part(&send
->p2
, ctx
->xb
, ctx
->p
.g
, ctx
);
286 /* g^x is a legal value */
287 static int is_legal(const BIGNUM
*gx
, const JPAKE_CTX
*ctx
)
292 if(BN_is_negative(gx
) || BN_is_zero(gx
) || BN_cmp(gx
, ctx
->p
.p
) >= 0)
296 BN_mod_exp(t
, gx
, ctx
->p
.q
, ctx
->p
.p
, ctx
->ctx
);
303 int JPAKE_STEP1_process(JPAKE_CTX
*ctx
, const JPAKE_STEP1
*received
)
305 if(!is_legal(received
->p1
.gx
, ctx
))
307 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS
, JPAKE_R_G_TO_THE_X3_IS_NOT_LEGAL
);
311 if(!is_legal(received
->p2
.gx
, ctx
))
313 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS
, JPAKE_R_G_TO_THE_X4_IS_NOT_LEGAL
);
317 /* verify their ZKP(xc) */
318 if(!verify_zkp(&received
->p1
, ctx
->p
.g
, ctx
))
320 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS
, JPAKE_R_VERIFY_X3_FAILED
);
324 /* verify their ZKP(xd) */
325 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
))
334 JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS
, JPAKE_R_G_TO_THE_X4_IS_ONE
);
338 /* Save the bits we need for later */
339 BN_copy(ctx
->p
.gxc
, received
->p1
.gx
);
340 BN_copy(ctx
->p
.gxd
, received
->p2
.gx
);
346 int JPAKE_STEP2_generate(JPAKE_STEP2
*send
, JPAKE_CTX
*ctx
)
348 BIGNUM
*t1
= BN_new();
349 BIGNUM
*t2
= BN_new();
352 * X = g^{(xa + xc + xd) * xb * s}
355 BN_mod_exp(t1
, ctx
->p
.g
, ctx
->xa
, ctx
->p
.p
, ctx
->ctx
);
356 /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */
357 BN_mod_mul(t2
, t1
, ctx
->p
.gxc
, ctx
->p
.p
, ctx
->ctx
);
358 /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */
359 BN_mod_mul(t1
, t2
, ctx
->p
.gxd
, ctx
->p
.p
, ctx
->ctx
);
361 BN_mod_mul(t2
, ctx
->xb
, ctx
->secret
, ctx
->p
.q
, ctx
->ctx
);
365 * XXX: this is kinda funky, because we're using
367 * g' = g^{xa + xc + xd}
369 * as the generator, which means X is g'^{xb * s}
370 * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s}
372 generate_step_part(send
, t2
, t1
, ctx
);
381 /* gx = g^{xc + xa + xb} * xd * s */
382 static int compute_key(JPAKE_CTX
*ctx
, const BIGNUM
*gx
)
384 BIGNUM
*t1
= BN_new();
385 BIGNUM
*t2
= BN_new();
386 BIGNUM
*t3
= BN_new();
389 * K = (gx/g^{xb * xd * s})^{xb}
390 * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb}
391 * = (g^{(xa + xc) * xd * s})^{xb}
392 * = g^{(xa + xc) * xb * xd * s}
393 * [which is the same regardless of who calculates it]
396 /* t1 = (g^{xd})^{xb} = g^{xb * xd} */
397 BN_mod_exp(t1
, ctx
->p
.gxd
, ctx
->xb
, ctx
->p
.p
, ctx
->ctx
);
399 BN_sub(t2
, ctx
->p
.q
, ctx
->secret
);
400 /* t3 = t1^t2 = g^{-xb * xd * s} */
401 BN_mod_exp(t3
, t1
, t2
, ctx
->p
.p
, ctx
->ctx
);
402 /* t1 = gx * t3 = X/g^{xb * xd * s} */
403 BN_mod_mul(t1
, gx
, t3
, ctx
->p
.p
, ctx
->ctx
);
405 BN_mod_exp(ctx
->key
, t1
, ctx
->xb
, ctx
->p
.p
, ctx
->ctx
);
415 int JPAKE_STEP2_process(JPAKE_CTX
*ctx
, const JPAKE_STEP2
*received
)
417 BIGNUM
*t1
= BN_new();
418 BIGNUM
*t2
= BN_new();
422 * g' = g^{xc + xa + xb} [from our POV]
425 BN_mod_add(t1
, ctx
->xa
, ctx
->xb
, ctx
->p
.q
, ctx
->ctx
);
426 /* t2 = g^{t1} = g^{xa+xb} */
427 BN_mod_exp(t2
, ctx
->p
.g
, t1
, ctx
->p
.p
, ctx
->ctx
);
428 /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */
429 BN_mod_mul(t1
, ctx
->p
.gxc
, t2
, ctx
->p
.p
, ctx
->ctx
);
431 if(verify_zkp(received
, t1
, ctx
))
434 JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS
, JPAKE_R_VERIFY_B_FAILED
);
436 compute_key(ctx
, received
->gx
);
445 static void quickhashbn(unsigned char *md
, const BIGNUM
*bn
)
451 SHA1_Final(md
, &sha
);
454 void JPAKE_STEP3A_init(JPAKE_STEP3A
*s3a
)
457 int JPAKE_STEP3A_generate(JPAKE_STEP3A
*send
, JPAKE_CTX
*ctx
)
459 quickhashbn(send
->hhk
, ctx
->key
);
460 SHA1(send
->hhk
, sizeof send
->hhk
, send
->hhk
);
465 int JPAKE_STEP3A_process(JPAKE_CTX
*ctx
, const JPAKE_STEP3A
*received
)
467 unsigned char hhk
[SHA_DIGEST_LENGTH
];
469 quickhashbn(hhk
, ctx
->key
);
470 SHA1(hhk
, sizeof hhk
, hhk
);
471 if(memcmp(hhk
, received
->hhk
, sizeof hhk
))
473 JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS
, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH
);
479 void JPAKE_STEP3A_release(JPAKE_STEP3A
*s3a
)
482 void JPAKE_STEP3B_init(JPAKE_STEP3B
*s3b
)
485 int JPAKE_STEP3B_generate(JPAKE_STEP3B
*send
, JPAKE_CTX
*ctx
)
487 quickhashbn(send
->hk
, ctx
->key
);
492 int JPAKE_STEP3B_process(JPAKE_CTX
*ctx
, const JPAKE_STEP3B
*received
)
494 unsigned char hk
[SHA_DIGEST_LENGTH
];
496 quickhashbn(hk
, ctx
->key
);
497 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
)
508 const BIGNUM
*JPAKE_get_shared_key(JPAKE_CTX
*ctx
)