| #include "jpake.h" |
| |
| #include <openssl/crypto.h> |
| #include <openssl/sha.h> |
| #include <openssl/err.h> |
| #include <memory.h> |
| |
| /* |
| * In the definition, (xa, xb, xc, xd) are Alice's (x1, x2, x3, x4) or |
| * Bob's (x3, x4, x1, x2). If you see what I mean. |
| */ |
| |
| typedef struct |
| { |
| char *name; /* Must be unique */ |
| char *peer_name; |
| BIGNUM *p; |
| BIGNUM *g; |
| BIGNUM *q; |
| BIGNUM *gxc; /* Alice's g^{x3} or Bob's g^{x1} */ |
| BIGNUM *gxd; /* Alice's g^{x4} or Bob's g^{x2} */ |
| } JPAKE_CTX_PUBLIC; |
| |
| struct JPAKE_CTX |
| { |
| JPAKE_CTX_PUBLIC p; |
| BIGNUM *secret; /* The shared secret */ |
| BN_CTX *ctx; |
| BIGNUM *xa; /* Alice's x1 or Bob's x3 */ |
| BIGNUM *xb; /* Alice's x2 or Bob's x4 */ |
| BIGNUM *key; /* The calculated (shared) key */ |
| }; |
| |
| static void JPAKE_ZKP_init(JPAKE_ZKP *zkp) |
| { |
| zkp->gr = BN_new(); |
| zkp->b = BN_new(); |
| } |
| |
| static void JPAKE_ZKP_release(JPAKE_ZKP *zkp) |
| { |
| BN_free(zkp->b); |
| BN_free(zkp->gr); |
| } |
| |
| /* Two birds with one stone - make the global name as expected */ |
| #define JPAKE_STEP_PART_init JPAKE_STEP2_init |
| #define JPAKE_STEP_PART_release JPAKE_STEP2_release |
| |
| void JPAKE_STEP_PART_init(JPAKE_STEP_PART *p) |
| { |
| p->gx = BN_new(); |
| JPAKE_ZKP_init(&p->zkpx); |
| } |
| |
| void JPAKE_STEP_PART_release(JPAKE_STEP_PART *p) |
| { |
| JPAKE_ZKP_release(&p->zkpx); |
| BN_free(p->gx); |
| } |
| |
| void JPAKE_STEP1_init(JPAKE_STEP1 *s1) |
| { |
| JPAKE_STEP_PART_init(&s1->p1); |
| JPAKE_STEP_PART_init(&s1->p2); |
| } |
| |
| void JPAKE_STEP1_release(JPAKE_STEP1 *s1) |
| { |
| JPAKE_STEP_PART_release(&s1->p2); |
| JPAKE_STEP_PART_release(&s1->p1); |
| } |
| |
| static void JPAKE_CTX_init(JPAKE_CTX *ctx, const char *name, |
| const char *peer_name, const BIGNUM *p, |
| const BIGNUM *g, const BIGNUM *q, |
| const BIGNUM *secret) |
| { |
| ctx->p.name = OPENSSL_strdup(name); |
| ctx->p.peer_name = OPENSSL_strdup(peer_name); |
| ctx->p.p = BN_dup(p); |
| ctx->p.g = BN_dup(g); |
| ctx->p.q = BN_dup(q); |
| ctx->secret = BN_dup(secret); |
| |
| ctx->p.gxc = BN_new(); |
| ctx->p.gxd = BN_new(); |
| |
| ctx->xa = BN_new(); |
| ctx->xb = BN_new(); |
| ctx->key = BN_new(); |
| ctx->ctx = BN_CTX_new(); |
| } |
| |
| static void JPAKE_CTX_release(JPAKE_CTX *ctx) |
| { |
| BN_CTX_free(ctx->ctx); |
| BN_clear_free(ctx->key); |
| BN_clear_free(ctx->xb); |
| BN_clear_free(ctx->xa); |
| |
| BN_free(ctx->p.gxd); |
| BN_free(ctx->p.gxc); |
| |
| BN_clear_free(ctx->secret); |
| BN_free(ctx->p.q); |
| BN_free(ctx->p.g); |
| BN_free(ctx->p.p); |
| OPENSSL_free(ctx->p.peer_name); |
| OPENSSL_free(ctx->p.name); |
| |
| memset(ctx, '\0', sizeof *ctx); |
| } |
| |
| JPAKE_CTX *JPAKE_CTX_new(const char *name, const char *peer_name, |
| const BIGNUM *p, const BIGNUM *g, const BIGNUM *q, |
| const BIGNUM *secret) |
| { |
| JPAKE_CTX *ctx = OPENSSL_malloc(sizeof *ctx); |
| |
| JPAKE_CTX_init(ctx, name, peer_name, p, g, q, secret); |
| |
| return ctx; |
| } |
| |
| void JPAKE_CTX_free(JPAKE_CTX *ctx) |
| { |
| JPAKE_CTX_release(ctx); |
| OPENSSL_free(ctx); |
| } |
| |
| static void hashlength(SHA_CTX *sha, size_t l) |
| { |
| unsigned char b[2]; |
| |
| OPENSSL_assert(l <= 0xffff); |
| b[0] = l >> 8; |
| b[1] = l&0xff; |
| SHA1_Update(sha, b, 2); |
| } |
| |
| static void hashstring(SHA_CTX *sha, const char *string) |
| { |
| size_t l = strlen(string); |
| |
| hashlength(sha, l); |
| SHA1_Update(sha, string, l); |
| } |
| |
| static void hashbn(SHA_CTX *sha, const BIGNUM *bn) |
| { |
| size_t l = BN_num_bytes(bn); |
| unsigned char *bin = OPENSSL_malloc(l); |
| |
| hashlength(sha, l); |
| BN_bn2bin(bn, bin); |
| SHA1_Update(sha, bin, l); |
| OPENSSL_free(bin); |
| } |
| |
| /* h=hash(g, g^r, g^x, name) */ |
| static void zkp_hash(BIGNUM *h, const BIGNUM *zkpg, const JPAKE_STEP_PART *p, |
| const char *proof_name) |
| { |
| unsigned char md[SHA_DIGEST_LENGTH]; |
| SHA_CTX sha; |
| |
| /* |
| * XXX: hash should not allow moving of the boundaries - Java code |
| * is flawed in this respect. Length encoding seems simplest. |
| */ |
| SHA1_Init(&sha); |
| hashbn(&sha, zkpg); |
| OPENSSL_assert(!BN_is_zero(p->zkpx.gr)); |
| hashbn(&sha, p->zkpx.gr); |
| hashbn(&sha, p->gx); |
| hashstring(&sha, proof_name); |
| SHA1_Final(md, &sha); |
| BN_bin2bn(md, SHA_DIGEST_LENGTH, h); |
| } |
| |
| /* |
| * Prove knowledge of x |
| * Note that p->gx has already been calculated |
| */ |
| static void generate_zkp(JPAKE_STEP_PART *p, const BIGNUM *x, |
| const BIGNUM *zkpg, JPAKE_CTX *ctx) |
| { |
| BIGNUM *r = BN_new(); |
| BIGNUM *h = BN_new(); |
| BIGNUM *t = BN_new(); |
| |
| /* |
| * r in [0,q) |
| * XXX: Java chooses r in [0, 2^160) - i.e. distribution not uniform |
| */ |
| BN_rand_range(r, ctx->p.q); |
| /* g^r */ |
| BN_mod_exp(p->zkpx.gr, zkpg, r, ctx->p.p, ctx->ctx); |
| |
| /* h=hash... */ |
| zkp_hash(h, zkpg, p, ctx->p.name); |
| |
| /* b = r - x*h */ |
| BN_mod_mul(t, x, h, ctx->p.q, ctx->ctx); |
| BN_mod_sub(p->zkpx.b, r, t, ctx->p.q, ctx->ctx); |
| |
| /* cleanup */ |
| BN_free(t); |
| BN_free(h); |
| BN_free(r); |
| } |
| |
| static int verify_zkp(const JPAKE_STEP_PART *p, const BIGNUM *zkpg, |
| JPAKE_CTX *ctx) |
| { |
| BIGNUM *h = BN_new(); |
| BIGNUM *t1 = BN_new(); |
| BIGNUM *t2 = BN_new(); |
| BIGNUM *t3 = BN_new(); |
| int ret = 0; |
| |
| zkp_hash(h, zkpg, p, ctx->p.peer_name); |
| |
| /* t1 = g^b */ |
| BN_mod_exp(t1, zkpg, p->zkpx.b, ctx->p.p, ctx->ctx); |
| /* t2 = (g^x)^h = g^{hx} */ |
| BN_mod_exp(t2, p->gx, h, ctx->p.p, ctx->ctx); |
| /* t3 = t1 * t2 = g^{hx} * g^b = g^{hx+b} = g^r (allegedly) */ |
| BN_mod_mul(t3, t1, t2, ctx->p.p, ctx->ctx); |
| |
| /* verify t3 == g^r */ |
| if(BN_cmp(t3, p->zkpx.gr) == 0) |
| ret = 1; |
| else |
| JPAKEerr(JPAKE_F_VERIFY_ZKP, JPAKE_R_ZKP_VERIFY_FAILED); |
| |
| /* cleanup */ |
| BN_free(t3); |
| BN_free(t2); |
| BN_free(t1); |
| BN_free(h); |
| |
| return ret; |
| } |
| |
| static void generate_step_part(JPAKE_STEP_PART *p, const BIGNUM *x, |
| const BIGNUM *g, JPAKE_CTX *ctx) |
| { |
| BN_mod_exp(p->gx, g, x, ctx->p.p, ctx->ctx); |
| generate_zkp(p, x, g, ctx); |
| } |
| |
| /* Generate each party's random numbers. xa is in [0, q), xb is in [1, q). */ |
| static void genrand(JPAKE_CTX *ctx) |
| { |
| BIGNUM *qm1; |
| |
| /* xa in [0, q) */ |
| BN_rand_range(ctx->xa, ctx->p.q); |
| |
| /* q-1 */ |
| qm1 = BN_new(); |
| BN_copy(qm1, ctx->p.q); |
| BN_sub_word(qm1, 1); |
| |
| /* ... and xb in [0, q-1) */ |
| BN_rand_range(ctx->xb, qm1); |
| /* [1, q) */ |
| BN_add_word(ctx->xb, 1); |
| |
| /* cleanup */ |
| BN_free(qm1); |
| } |
| |
| int JPAKE_STEP1_generate(JPAKE_STEP1 *send, JPAKE_CTX *ctx) |
| { |
| genrand(ctx); |
| generate_step_part(&send->p1, ctx->xa, ctx->p.g, ctx); |
| generate_step_part(&send->p2, ctx->xb, ctx->p.g, ctx); |
| |
| return 1; |
| } |
| |
| int JPAKE_STEP1_process(JPAKE_CTX *ctx, const JPAKE_STEP1 *received) |
| { |
| /* verify their ZKP(xc) */ |
| if(!verify_zkp(&received->p1, ctx->p.g, ctx)) |
| { |
| JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X3_FAILED); |
| return 0; |
| } |
| |
| /* verify their ZKP(xd) */ |
| if(!verify_zkp(&received->p2, ctx->p.g, ctx)) |
| { |
| JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_VERIFY_X4_FAILED); |
| return 0; |
| } |
| |
| /* g^xd != 1 */ |
| if(BN_is_one(received->p2.gx)) |
| { |
| JPAKEerr(JPAKE_F_JPAKE_STEP1_PROCESS, JPAKE_R_G_TO_THE_X4_IS_ONE); |
| return 0; |
| } |
| |
| /* Save the bits we need for later */ |
| BN_copy(ctx->p.gxc, received->p1.gx); |
| BN_copy(ctx->p.gxd, received->p2.gx); |
| |
| return 1; |
| } |
| |
| |
| int JPAKE_STEP2_generate(JPAKE_STEP2 *send, JPAKE_CTX *ctx) |
| { |
| BIGNUM *t1 = BN_new(); |
| BIGNUM *t2 = BN_new(); |
| |
| /* |
| * X = g^{(xa + xc + xd) * xb * s} |
| * t1 = g^xa |
| */ |
| BN_mod_exp(t1, ctx->p.g, ctx->xa, ctx->p.p, ctx->ctx); |
| /* t2 = t1 * g^{xc} = g^{xa} * g^{xc} = g^{xa + xc} */ |
| BN_mod_mul(t2, t1, ctx->p.gxc, ctx->p.p, ctx->ctx); |
| /* t1 = t2 * g^{xd} = g^{xa + xc + xd} */ |
| BN_mod_mul(t1, t2, ctx->p.gxd, ctx->p.p, ctx->ctx); |
| /* t2 = xb * s */ |
| BN_mod_mul(t2, ctx->xb, ctx->secret, ctx->p.q, ctx->ctx); |
| |
| /* |
| * ZKP(xb * s) |
| * XXX: this is kinda funky, because we're using |
| * |
| * g' = g^{xa + xc + xd} |
| * |
| * as the generator, which means X is g'^{xb * s} |
| * X = t1^{t2} = t1^{xb * s} = g^{(xa + xc + xd) * xb * s} |
| */ |
| generate_step_part(send, t2, t1, ctx); |
| |
| /* cleanup */ |
| BN_free(t1); |
| BN_free(t2); |
| |
| return 1; |
| } |
| |
| /* gx = g^{xc + xa + xb} * xd * s */ |
| static int compute_key(JPAKE_CTX *ctx, const BIGNUM *gx) |
| { |
| BIGNUM *t1 = BN_new(); |
| BIGNUM *t2 = BN_new(); |
| BIGNUM *t3 = BN_new(); |
| |
| /* |
| * K = (gx/g^{xb * xd * s})^{xb} |
| * = (g^{(xc + xa + xb) * xd * s - xb * xd *s})^{xb} |
| * = (g^{(xa + xc) * xd * s})^{xb} |
| * = g^{(xa + xc) * xb * xd * s} |
| * [which is the same regardless of who calculates it] |
| */ |
| |
| /* t1 = (g^{xd})^{xb} = g^{xb * xd} */ |
| BN_mod_exp(t1, ctx->p.gxd, ctx->xb, ctx->p.p, ctx->ctx); |
| /* t2 = -s = q-s */ |
| BN_sub(t2, ctx->p.q, ctx->secret); |
| /* t3 = t1^t2 = g^{-xb * xd * s} */ |
| BN_mod_exp(t3, t1, t2, ctx->p.p, ctx->ctx); |
| /* t1 = gx * t3 = X/g^{xb * xd * s} */ |
| BN_mod_mul(t1, gx, t3, ctx->p.p, ctx->ctx); |
| /* K = t1^{xb} */ |
| BN_mod_exp(ctx->key, t1, ctx->xb, ctx->p.p, ctx->ctx); |
| |
| /* cleanup */ |
| BN_free(t3); |
| BN_free(t2); |
| BN_free(t1); |
| |
| return 1; |
| } |
| |
| int JPAKE_STEP2_process(JPAKE_CTX *ctx, const JPAKE_STEP2 *received) |
| { |
| BIGNUM *t1 = BN_new(); |
| BIGNUM *t2 = BN_new(); |
| int ret = 0; |
| |
| /* |
| * g' = g^{xc + xa + xb} [from our POV] |
| * t1 = xa + xb |
| */ |
| BN_mod_add(t1, ctx->xa, ctx->xb, ctx->p.q, ctx->ctx); |
| /* t2 = g^{t1} = g^{xa+xb} */ |
| BN_mod_exp(t2, ctx->p.g, t1, ctx->p.p, ctx->ctx); |
| /* t1 = g^{xc} * t2 = g^{xc + xa + xb} */ |
| BN_mod_mul(t1, ctx->p.gxc, t2, ctx->p.p, ctx->ctx); |
| |
| if(verify_zkp(received, t1, ctx)) |
| ret = 1; |
| else |
| JPAKEerr(JPAKE_F_JPAKE_STEP2_PROCESS, JPAKE_R_VERIFY_B_FAILED); |
| |
| compute_key(ctx, received->gx); |
| |
| /* cleanup */ |
| BN_free(t2); |
| BN_free(t1); |
| |
| return ret; |
| } |
| |
| static void quickhashbn(unsigned char *md, const BIGNUM *bn) |
| { |
| SHA_CTX sha; |
| |
| SHA1_Init(&sha); |
| hashbn(&sha, bn); |
| SHA1_Final(md, &sha); |
| } |
| |
| void JPAKE_STEP3A_init(JPAKE_STEP3A *s3a) |
| {} |
| |
| int JPAKE_STEP3A_generate(JPAKE_STEP3A *send, JPAKE_CTX *ctx) |
| { |
| quickhashbn(send->hhk, ctx->key); |
| SHA1(send->hhk, sizeof send->hhk, send->hhk); |
| |
| return 1; |
| } |
| |
| int JPAKE_STEP3A_process(JPAKE_CTX *ctx, const JPAKE_STEP3A *received) |
| { |
| unsigned char hhk[SHA_DIGEST_LENGTH]; |
| |
| quickhashbn(hhk, ctx->key); |
| SHA1(hhk, sizeof hhk, hhk); |
| if(memcmp(hhk, received->hhk, sizeof hhk)) |
| { |
| JPAKEerr(JPAKE_F_JPAKE_STEP3A_PROCESS, JPAKE_R_HASH_OF_HASH_OF_KEY_MISMATCH); |
| return 0; |
| } |
| return 1; |
| } |
| |
| void JPAKE_STEP3A_release(JPAKE_STEP3A *s3a) |
| {} |
| |
| void JPAKE_STEP3B_init(JPAKE_STEP3B *s3b) |
| {} |
| |
| int JPAKE_STEP3B_generate(JPAKE_STEP3B *send, JPAKE_CTX *ctx) |
| { |
| quickhashbn(send->hk, ctx->key); |
| |
| return 1; |
| } |
| |
| int JPAKE_STEP3B_process(JPAKE_CTX *ctx, const JPAKE_STEP3B *received) |
| { |
| unsigned char hk[SHA_DIGEST_LENGTH]; |
| |
| quickhashbn(hk, ctx->key); |
| if(memcmp(hk, received->hk, sizeof hk)) |
| { |
| JPAKEerr(JPAKE_F_JPAKE_STEP3B_PROCESS, JPAKE_R_HASH_OF_KEY_MISMATCH); |
| return 0; |
| } |
| return 1; |
| } |
| |
| void JPAKE_STEP3B_release(JPAKE_STEP3B *s3b) |
| {} |
| |
| const BIGNUM *JPAKE_get_shared_key(JPAKE_CTX *ctx) |
| { |
| return ctx->key; |
| } |
| |