/* Out: bytes_B, len_B.
*
* On failure, bytes_B will be set to NULL and len_B will be set to 0
*/
struct SRPVerifier * srp_verifier_new( SRP_HashAlgorithm alg, SRP_NGType ng_type, const char * username,
const unsigned char * bytes_s, int len_s,
const unsigned char * bytes_v, int len_v,
const unsigned char * bytes_A, int len_A,
const unsigned char ** bytes_B, int * len_B,
const char * n_hex, const char * g_hex )
{
BIGNUM *s = BN_bin2bn(bytes_s, len_s, NULL);
BIGNUM *v = BN_bin2bn(bytes_v, len_v, NULL);
BIGNUM *A = BN_bin2bn(bytes_A, len_A, NULL);
BIGNUM *u = 0;
BIGNUM *B = BN_new();
BIGNUM *S = BN_new();
BIGNUM *b = BN_new();
BIGNUM *k = 0;
BIGNUM *tmp1 = BN_new();
BIGNUM *tmp2 = BN_new();
BN_CTX *ctx = BN_CTX_new();
int ulen = strlen(username) + 1;
NGConstant *ng = new_ng( ng_type, n_hex, g_hex );
struct SRPVerifier *ver = 0;
*len_B = 0;
*bytes_B = 0;
if( !s || !v || !A || !B || !S || !b || !tmp1 || !tmp2 || !ctx || !ng )
goto cleanup_and_exit;
ver = (struct SRPVerifier *) malloc( sizeof(struct SRPVerifier) );
if (!ver)
goto cleanup_and_exit;
init_random(); /* Only happens once */
ver->username = (char *) malloc( ulen );
ver->hash_alg = alg;
ver->ng = ng;
if (!ver->username)
{
free(ver);
ver = 0;
goto cleanup_and_exit;
}
memcpy( (char*)ver->username, username, ulen );
ver->authenticated = 0;
/* SRP-6a safety check */
BN_mod(tmp1, A, ng->N, ctx);
if ( !BN_is_zero(tmp1) )
{
BN_rand(b, 256, -1, 0);
k = H_nn(alg, ng->N, ng->g);
/* B = kv + g^b */
BN_mul(tmp1, k, v, ctx);
BN_mod_exp(tmp2, ng->g, b, ng->N, ctx);
BN_add(B, tmp1, tmp2);
u = H_nn(alg, A, B);
/* S = (A *(v^u)) ^ b */
BN_mod_exp(tmp1, v, u, ng->N, ctx);
BN_mul(tmp2, A, tmp1, ctx);
BN_mod_exp(S, tmp2, b, ng->N, ctx);
hash_num(alg, S, ver->session_key);
calculate_M( alg, ng, ver->M, username, s, A, B, ver->session_key );
calculate_H_AMK( alg, ver->H_AMK, A, ver->M, ver->session_key );
*len_B = BN_num_bytes(B);
*bytes_B = malloc( *len_B );
if( !*bytes_B )
{
free( (void*) ver->username );
free( ver );
ver = 0;
*len_B = 0;
goto cleanup_and_exit;
}
BN_bn2bin( B, (unsigned char *) *bytes_B );
ver->bytes_B = *bytes_B;
}
cleanup_and_exit:
BN_free(s);
BN_free(v);
BN_free(A);
if (u) BN_free(u);
if (k) BN_free(k);
BN_free(B);
BN_free(S);
BN_free(b);
BN_free(tmp1);
BN_free(tmp2);
BN_CTX_free(ctx);
return ver;
}
/* Output: bytes_M. Buffer length is SHA512_DIGEST_LENGTH */
void srp_user_process_challenge(struct SRPUser *usr,
const unsigned char *bytes_s, size_t len_s,
const unsigned char *bytes_B, size_t len_B,
unsigned char **bytes_M, size_t *len_M)
{
mpz_t B; mpz_init(B); mpz_from_bin(bytes_B, len_B, B);
mpz_t u; mpz_init(u);
mpz_t x; mpz_init(x);
mpz_t k; mpz_init(k);
mpz_t v; mpz_init(v);
mpz_t tmp1; mpz_init(tmp1);
mpz_t tmp2; mpz_init(tmp2);
mpz_t tmp3; mpz_init(tmp3);
mpz_t tmp4; mpz_init(tmp4);
// clang-format on
if(len_M)
*len_M = 0;
*bytes_M = 0;
if (!H_nn(u, usr->hash_alg, usr->ng->N, usr->A, B)) goto cleanup_and_exit;
srp_dbg_num(u, "Client calculated u: ");
if (!calculate_x(x, usr->hash_alg, bytes_s, len_s, usr->username_verifier,
usr->password, usr->password_len))
goto cleanup_and_exit;
srp_dbg_num(x, "Client calculated x: ");
if (!H_nn(k, usr->hash_alg, usr->ng->N, usr->ng->N, usr->ng->g))
goto cleanup_and_exit;
/* SRP-6a safety check */
if (mpz_sgn(B) != 0 && mpz_sgn(u) != 0) {
mpz_powm(v, usr->ng->g, x, usr->ng->N);
srp_dbg_num(v, "Client calculated v: ");
// clang-format off
/* S = (B - k*(g^x)) ^ (a + ux) */
mpz_mul(tmp1, u, x);
mpz_add(tmp2, usr->a, tmp1); /* tmp2 = (a + ux) */
mpz_powm(tmp1, usr->ng->g, x, usr->ng->N); /* tmp1 = g^x */
mpz_mulm(tmp3, k, tmp1, usr->ng->N, tmp4); /* tmp3 = k*(g^x) */
mpz_subm(tmp1, B, tmp3, usr->ng->N, tmp4); /* tmp1 = (B - K*(g^x)) */
mpz_powm(usr->S, tmp1, tmp2, usr->ng->N);
// clang-format on
if (!hash_num(usr->hash_alg, usr->S, usr->session_key)) goto cleanup_and_exit;
if (!calculate_M(usr->hash_alg, usr->ng, usr->M, usr->username, bytes_s, len_s,
usr->A, B, usr->session_key))
goto cleanup_and_exit;
if (!calculate_H_AMK(usr->hash_alg, usr->H_AMK, usr->A, usr->M, usr->session_key))
goto cleanup_and_exit;
*bytes_M = usr->M;
if (len_M) *len_M = hash_length(usr->hash_alg);
} else {
*bytes_M = NULL;
if (len_M) *len_M = 0;
}
cleanup_and_exit:
mpz_clear(B);
mpz_clear(u);
mpz_clear(x);
mpz_clear(k);
mpz_clear(v);
mpz_clear(tmp1);
mpz_clear(tmp2);
mpz_clear(tmp3);
mpz_clear(tmp4);
}
/* Output: bytes_M. Buffer length is SHA512_DIGEST_LENGTH */
void srp_user_process_challenge( struct SRPUser * usr,
const unsigned char * bytes_s, int len_s,
const unsigned char * bytes_B, int len_B,
const unsigned char ** bytes_M, int * len_M )
{
BIGNUM *s = BN_bin2bn(bytes_s, len_s, NULL);
BIGNUM *B = BN_bin2bn(bytes_B, len_B, NULL);
BIGNUM *u = 0;
BIGNUM *x = 0;
BIGNUM *k = 0;
BIGNUM *v = BN_new();
BIGNUM *tmp1 = BN_new();
BIGNUM *tmp2 = BN_new();
BIGNUM *tmp3 = BN_new();
BN_CTX *ctx = BN_CTX_new();
*len_M = 0;
*bytes_M = 0;
if( !s || !B || !v || !tmp1 || !tmp2 || !tmp3 || !ctx )
goto cleanup_and_exit;
u = H_nn(usr->hash_alg, usr->A, B);
if (!u)
goto cleanup_and_exit;
x = calculate_x( usr->hash_alg, s, usr->username, usr->password, usr->password_len );
if (!x)
goto cleanup_and_exit;
k = H_nn(usr->hash_alg, usr->ng->N, usr->ng->g);
if (!k)
goto cleanup_and_exit;
/* SRP-6a safety check */
if ( !BN_is_zero(B) && !BN_is_zero(u) )
{
BN_mod_exp(v, usr->ng->g, x, usr->ng->N, ctx);
/* S = (B - k*(g^x)) ^ (a + ux) */
BN_mul(tmp1, u, x, ctx);
BN_add(tmp2, usr->a, tmp1); /* tmp2 = (a + ux) */
BN_mod_exp(tmp1, usr->ng->g, x, usr->ng->N, ctx);
BN_mul(tmp3, k, tmp1, ctx); /* tmp3 = k*(g^x) */
BN_sub(tmp1, B, tmp3); /* tmp1 = (B - K*(g^x)) */
BN_mod_exp(usr->S, tmp1, tmp2, usr->ng->N, ctx);
hash_num(usr->hash_alg, usr->S, usr->session_key);
calculate_M( usr->hash_alg, usr->ng, usr->M, usr->username, s, usr->A, B, usr->session_key );
calculate_H_AMK( usr->hash_alg, usr->H_AMK, usr->A, usr->M, usr->session_key );
*bytes_M = usr->M;
if (len_M)
*len_M = hash_length( usr->hash_alg );
}
else
{
*bytes_M = NULL;
if (len_M)
*len_M = 0;
}
cleanup_and_exit:
BN_free(s);
BN_free(B);
BN_free(u);
BN_free(x);
BN_free(k);
BN_free(v);
BN_free(tmp1);
BN_free(tmp2);
BN_free(tmp3);
BN_CTX_free(ctx);
}
/* Out: bytes_B, len_B.
*
* On failure, bytes_B will be set to NULL and len_B will be set to 0
*/
struct SRPVerifier *srp_verifier_new(SRP_HashAlgorithm alg,
SRP_NGType ng_type, const char *username,
const unsigned char *bytes_s, size_t len_s,
const unsigned char *bytes_v, size_t len_v,
const unsigned char *bytes_A, size_t len_A,
const unsigned char *bytes_b, size_t len_b,
unsigned char **bytes_B, size_t *len_B,
const char *n_hex, const char *g_hex )
{
mpz_t v; mpz_init(v); mpz_from_bin(bytes_v, len_v, v);
mpz_t A; mpz_init(A); mpz_from_bin(bytes_A, len_A, A);
mpz_t u; mpz_init(u);
mpz_t B; mpz_init(B);
mpz_t S; mpz_init(S);
mpz_t b; mpz_init(b);
mpz_t k; mpz_init(k);
mpz_t tmp1; mpz_init(tmp1);
mpz_t tmp2; mpz_init(tmp2);
mpz_t tmp3; mpz_init(tmp3);
// clang-format on
size_t ulen = strlen(username) + 1;
NGConstant *ng = new_ng(ng_type, n_hex, g_hex);
struct SRPVerifier *ver = 0;
*len_B = 0;
*bytes_B = 0;
if (!ng) goto cleanup_and_exit;
ver = (struct SRPVerifier *)srp_alloc(sizeof(struct SRPVerifier));
if (!ver) goto cleanup_and_exit;
if (init_random() != SRP_OK) { /* Only happens once */
srp_free(ver);
ver = 0;
goto cleanup_and_exit;
}
ver->username = (char *)srp_alloc(ulen);
ver->hash_alg = alg;
ver->ng = ng;
if (!ver->username) {
srp_free(ver);
ver = 0;
goto cleanup_and_exit;
}
memcpy((char *)ver->username, username, ulen);
ver->authenticated = 0;
/* SRP-6a safety check */
mpz_mod(tmp1, A, ng->N);
if (mpz_sgn(tmp1) != 0) {
if (bytes_b) {
mpz_from_bin(bytes_b, len_b, b);
} else {
if (!mpz_fill_random(b)) goto ver_cleanup_and_exit;
}
if (!H_nn(k, alg, ng->N, ng->N, ng->g)) goto ver_cleanup_and_exit;
/* B = kv + g^b */
mpz_mulm(tmp1, k, v, ng->N, tmp3);
mpz_powm(tmp2, ng->g, b, ng->N);
mpz_addm(B, tmp1, tmp2, ng->N, tmp3);
if (!H_nn(u, alg, ng->N, A, B)) goto ver_cleanup_and_exit;
srp_dbg_num(u, "Server calculated u: ");
/* S = (A *(v^u)) ^ b */
mpz_powm(tmp1, v, u, ng->N);
mpz_mulm(tmp2, A, tmp1, ng->N, tmp3);
mpz_powm(S, tmp2, b, ng->N);
if (!hash_num(alg, S, ver->session_key)) goto ver_cleanup_and_exit;
if (!calculate_M(
alg, ng, ver->M, username, bytes_s, len_s, A, B, ver->session_key)) {
goto ver_cleanup_and_exit;
}
if (!calculate_H_AMK(alg, ver->H_AMK, A, ver->M, ver->session_key)) {
goto ver_cleanup_and_exit;
}
*len_B = mpz_num_bytes(B);
*bytes_B = (unsigned char *)srp_alloc(*len_B);
if (!*bytes_B) {
*len_B = 0;
goto ver_cleanup_and_exit;
}
mpz_to_bin(B, *bytes_B);
ver->bytes_B = *bytes_B;
} else {
srp_free(ver);
ver = 0;
}
cleanup_and_exit:
mpz_clear(v);
mpz_clear(A);
mpz_clear(u);
mpz_clear(k);
mpz_clear(B);
mpz_clear(S);
mpz_clear(b);
mpz_clear(tmp1);
mpz_clear(tmp2);
mpz_clear(tmp3);
return ver;
ver_cleanup_and_exit:
srp_free(ver->username);
srp_free(ver);
ver = 0;
goto cleanup_and_exit;
}