Network: De-duplicate getting random bytes with fallback

src/network/network.cpp

@@ -1315,15 +1315,9 @@ static void NetworkGenerateServerId()
 std::string NetworkGenerateRandomKeyString(uint bytes)
 {
 	uint8 *key = AllocaM(uint8, bytes);
-	char *hex_output = AllocaM(char, bytes * 2);
+	NetworkRandomBytesWithFallback(key, bytes);
 
-	if (randombytes(key, bytes) < 0) {
-		/* Fallback poor-quality random */
-		DEBUG(misc, 0, "High quality random source unavailable");
-		for (uint i = 0; i < bytes; i++) {
-			key[i] = (uint8)InteractiveRandom();
-		}
-	}
+	char *hex_output = AllocaM(char, bytes * 2);
 
 	char txt[3];
 	for (uint i = 0; i < bytes; ++i) {
@@ -1401,6 +1395,17 @@ void NetworkShutDown()
 	NetworkCoreShutdown();
 }
 
+void NetworkRandomBytesWithFallback(void *buf, size_t bytes)
+{
+	if (randombytes(buf, bytes) < 0) {
+		/* Fallback poor-quality random */
+		DEBUG(net, 0, "High quality random source unavailable");
+		for (uint i = 0; i < bytes; i++) {
+			reinterpret_cast<byte *>(buf)[i] = (byte)InteractiveRandom();
+		}
+	}
+}
+
 #ifdef __EMSCRIPTEN__
 extern "C" {
 

src/network/network_internal.h

@@ -156,4 +156,6 @@ std::string NormalizeConnectionString(const std::string &connection_string, uint
 
 void ClientNetworkEmergencySave();
 
+void NetworkRandomBytesWithFallback(void *buf, size_t n);
+
 #endif /* NETWORK_INTERNAL_H */

src/network/network_server.cpp

@@ -214,12 +214,9 @@ ServerNetworkGameSocketHandler::ServerNetworkGameSocketHandler(SOCKET s) : Netwo
 	this->receive_limit = _settings_client.network.bytes_per_frame_burst;
 
 	uint64 seeds[3];
-	if (randombytes(&seeds, sizeof(uint64) * lengthof(seeds)) < 0) {
-		/* Can't get random data, use InteractiveRandom */
-		for (uint64 &seed : seeds) {
-			seed = (uint64)(InteractiveRandom()) | (((uint64)(InteractiveRandom())) << 32);
-		}
-	}
+	static_assert(sizeof(seeds) == 24);
+	NetworkRandomBytesWithFallback(seeds, sizeof(seeds));
+
 	this->server_hash_bits = seeds[0];
 	this->rcon_hash_bits = seeds[1];
 	this->settings_hash_bits = seeds[2];