Don't clear global b_prime/b_generator (see 7e7beb95660)

src/crypto/dh_util.cc

@@ -86,7 +86,7 @@ void DH1080_gen(bd::String& privateKey, bd::String& publicKeyB64) {
   dh = DH_new();
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
   if (b_prime == NULL || b_generator == NULL ||
-      !DH_set0_pqg(dh, b_prime, NULL, b_generator))
+      !DH_set0_pqg(dh, BN_dup(b_prime), NULL, BN_dup(b_generator)))
     return;
 #else
   dh->p = BN_dup(b_prime);
@@ -128,7 +128,7 @@ bool DH1080_comp(const bd::String privateKey, const bd::String theirPublicKeyB64
   dh = DH_new();
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L
   if (b_prime == NULL || b_generator == NULL ||
-      !DH_set0_pqg(dh, b_prime, NULL, b_generator))
+      !DH_set0_pqg(dh, BN_dup(b_prime), NULL, BN_dup(b_generator)))
     return false;
 #else
   dh->p = BN_dup(b_prime);