+ return SSL_TLSEXT_ERR_OK;
+ }
+
+#ifndef OPENSSL_NO_SRP
+
+/* This is a context that we pass to all callbacks */
+typedef struct srp_arg_st
+ {
+ char *srppassin;
+ char *srplogin;
+ int msg; /* copy from c_msg */
+ int debug; /* copy from c_debug */
+ int amp; /* allow more groups */
+ int strength /* minimal size for N */ ;
+ } SRP_ARG;
+
+#define SRP_NUMBER_ITERATIONS_FOR_PRIME 64
+
+static int SRP_Verify_N_and_g(const BIGNUM *N, const BIGNUM *g)
+ {
+ BN_CTX *bn_ctx = BN_CTX_new();
+ BIGNUM *p = BN_new();
+ BIGNUM *r = BN_new();
+ int ret =
+ g != NULL && N != NULL && bn_ctx != NULL && BN_is_odd(N) &&
+ BN_is_prime_ex(N,SRP_NUMBER_ITERATIONS_FOR_PRIME,bn_ctx,NULL) &&
+ p != NULL && BN_rshift1(p, N) &&
+
+ /* p = (N-1)/2 */
+ BN_is_prime_ex(p,SRP_NUMBER_ITERATIONS_FOR_PRIME,bn_ctx,NULL) &&
+ r != NULL &&
+
+ /* verify g^((N-1)/2) == -1 (mod N) */
+ BN_mod_exp(r, g, p, N, bn_ctx) &&
+ BN_add_word(r, 1) &&
+ BN_cmp(r, N) == 0;
+
+ if(r)
+ BN_free(r);
+ if(p)
+ BN_free(p);
+ if(bn_ctx)
+ BN_CTX_free(bn_ctx);
+ return ret;
+ }
+
+static int MS_CALLBACK ssl_srp_verify_param_cb(SSL *s, void *arg)
+ {
+ SRP_ARG *srp_arg = (SRP_ARG *)arg;
+ BIGNUM *N = NULL, *g = NULL;
+ if (!(N = SSL_get_srp_N(s)) || !(g = SSL_get_srp_g(s)))
+ return 0;
+ if (srp_arg->debug || srp_arg->msg || srp_arg->amp == 1)
+ {
+ BIO_printf(bio_err, "SRP parameters:\n");
+ BIO_printf(bio_err,"\tN="); BN_print(bio_err,N);
+ BIO_printf(bio_err,"\n\tg="); BN_print(bio_err,g);
+ BIO_printf(bio_err,"\n");
+ }
+
+ if (SRP_check_known_gN_param(g,N))
+ return 1;
+
+ if (srp_arg->amp == 1)
+ {
+ if (srp_arg->debug)
+ BIO_printf(bio_err, "SRP param N and g are not known params, going to check deeper.\n");
+
+/* The srp_moregroups must be used with caution, testing primes costs time.
+ Implementors should rather add the value to the known ones.
+ The minimal size has already been tested.
+*/
+ if (BN_num_bits(g) <= BN_BITS && SRP_Verify_N_and_g(N,g))
+ return 1;
+ }
+ BIO_printf(bio_err, "SRP param N and g rejected.\n");
+ return 0;