[crypto/rsa] Set the constant-time flag in multi-prime RSA too

Reviewed-by: NBernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9779)

crypto/rsa/rsa_lib.c

@@ -409,12 +409,15 @@ int RSA_set0_multi_prime_params(RSA *r, BIGNUM *primes[], BIGNUM *exps[],
         if (pinfo == NULL)
             goto err;
         if (primes[i] != NULL && exps[i] != NULL && coeffs[i] != NULL) {
-            BN_free(pinfo->r);
-            BN_free(pinfo->d);
-            BN_free(pinfo->t);
+            BN_clear_free(pinfo->r);
+            BN_clear_free(pinfo->d);
+            BN_clear_free(pinfo->t);
             pinfo->r = primes[i];
             pinfo->d = exps[i];
             pinfo->t = coeffs[i];
+            BN_set_flags(pinfo->r, BN_FLG_CONSTTIME);
+            BN_set_flags(pinfo->d, BN_FLG_CONSTTIME);
+            BN_set_flags(pinfo->t, BN_FLG_CONSTTIME);
         } else {
             rsa_multip_info_free(pinfo);
             goto err;