int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N) { /* Checks if A % N == 0 */ return SRP_Verify_B_mod_N(A, N); }
static int run_srp(const char *username, const char *client_pass, const char *server_pass) { int ret = -1; BIGNUM *s = NULL; BIGNUM *v = NULL; BIGNUM *a = NULL; BIGNUM *b = NULL; BIGNUM *u = NULL; BIGNUM *x = NULL; BIGNUM *Apub = NULL; BIGNUM *Bpub = NULL; BIGNUM *Kclient = NULL; BIGNUM *Kserver = NULL; unsigned char rand_tmp[RANDOM_SIZE]; /* use builtin 1024-bit params */ const SRP_gN *GN = SRP_get_default_gN("1024"); if (GN == NULL) { fprintf(stderr, "Failed to get SRP parameters\n"); return -1; } /* Set up server's password entry */ if (!SRP_create_verifier_BN(username, server_pass, &s, &v, GN->N, GN->g)) { fprintf(stderr, "Failed to create SRP verifier\n"); return -1; } showbn("N", GN->N); showbn("g", GN->g); showbn("Salt", s); showbn("Verifier", v); /* Server random */ RAND_bytes(rand_tmp, sizeof(rand_tmp)); b = BN_bin2bn(rand_tmp, sizeof(rand_tmp), NULL); /* TODO - check b != 0 */ showbn("b", b); /* Server's first message */ Bpub = SRP_Calc_B(b, GN->N, GN->g, v); showbn("B", Bpub); if (!SRP_Verify_B_mod_N(Bpub, GN->N)) { fprintf(stderr, "Invalid B\n"); return -1; } /* Client random */ RAND_bytes(rand_tmp, sizeof(rand_tmp)); a = BN_bin2bn(rand_tmp, sizeof(rand_tmp), NULL); /* TODO - check a != 0 */ showbn("a", a); /* Client's response */ Apub = SRP_Calc_A(a, GN->N, GN->g); showbn("A", Apub); if (!SRP_Verify_A_mod_N(Apub, GN->N)) { fprintf(stderr, "Invalid A\n"); return -1; } /* Both sides calculate u */ u = SRP_Calc_u(Apub, Bpub, GN->N); /* Client's key */ x = SRP_Calc_x(s, username, client_pass); Kclient = SRP_Calc_client_key(GN->N, Bpub, GN->g, x, a, u); showbn("Client's key", Kclient); /* Server's key */ Kserver = SRP_Calc_server_key(Apub, v, u, b, GN->N); showbn("Server's key", Kserver); if (BN_cmp(Kclient, Kserver) == 0) { ret = 0; } else { fprintf(stderr, "Keys mismatch\n"); ret = 1; } BN_clear_free(Kclient); BN_clear_free(Kserver); BN_clear_free(x); BN_free(u); BN_free(Apub); BN_clear_free(a); BN_free(Bpub); BN_clear_free(b); BN_free(s); BN_clear_free(v); return ret; }