bcrypt: Return an error when BCryptFinalizeKeyPair() is called twice.

dlls/bcrypt/gnutls.c

@@ -846,6 +846,7 @@ static NTSTATUS key_asymmetric_generate( void *args )
     int ret;
 
     if (!libgnutls_handle) return STATUS_INTERNAL_ERROR;
+    if (key_data(key)->privkey) return STATUS_INVALID_HANDLE;
 
     switch (key->alg_id)
     {

dlls/bcrypt/tests/bcrypt.c

@@ -2157,6 +2157,9 @@ static void test_RSA(void)
     ret = BCryptImportKeyPair(alg, NULL, BCRYPT_RSAPRIVATE_BLOB, &key, rsaPrivateBlob, sizeof(rsaPrivateBlob), 0);
     ok(ret == STATUS_SUCCESS, "got %#lx\n", ret);
 
+    ret = BCryptFinalizeKeyPair(key, 0);
+    ok(ret == STATUS_INVALID_HANDLE, "got %#lx\n", ret);
+
     size = 0;
     buf = HeapAlloc(GetProcessHeap(), 0, sizeof(rsaPrivateBlob));
     ret = BCryptExportKey(key, NULL, BCRYPT_RSAPRIVATE_BLOB, buf, sizeof(rsaPrivateBlob), &size, 0);
@@ -2565,6 +2568,9 @@ static void test_BCryptSignHash(void)
     ret = BCryptFinalizeKeyPair(key, 0);
     ok(ret == STATUS_SUCCESS, "got %#lx\n", ret);
 
+    ret = BCryptFinalizeKeyPair(key, 0);
+    ok(ret == STATUS_INVALID_HANDLE, "got %#lx\n", ret);
+
     len = 0;
     memset(sig, 0, sizeof(sig));