From 8c80877d2995ef13d99f2af9d24a66e0d68f692f Mon Sep 17 00:00:00 2001
From: Petr Baudis <pasky@ucw.cz>
Date: Mon, 24 Nov 2003 16:12:20 +0000
Subject: [PATCH] Optimized the brute-force decryption. Now it still first
 tries the correct hash and if doesn't succed it goes for bruteforce.

---
 server.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/server.c b/server.c
index 00d07a2..dd73482 100644
--- a/server.c
+++ b/server.c
@@ -904,15 +904,15 @@ static void check_sockets()
 	if (!FD_ISSET(fd, &fds))
 	    continue;
 	sgets(buf, sizeof(buf), fd);
+
 	if (player_socks[i] < 0) {
 	    /* Our extension: the client can give up on the meaningless
 	     * encryption completely. */
 	    if (strncmp(buf,"tetrisstart ",12) != 0) {
 		/* Messy decoding stuff */
 		char iphashbuf[16], newbuf[1024];
-#ifdef NO_BRUTE_FORCE_DECRYPTION
 		unsigned char *ip;
-#else
+#ifndef NO_BRUTE_FORCE_DECRYPTION
 		int hashval;
 #endif
 
@@ -921,35 +921,41 @@ static void check_sockets()
 		    player_socks[i] = -1;
 		    continue;
 		}
-#ifdef NO_BRUTE_FORCE_DECRYPTION
+
 		ip = player_ips[i];
 		sprintf(iphashbuf, "%d",
 			ip[0]*54 + ip[1]*41 + ip[2]*29 + ip[3]*17);
-#else
+		decrypt_message(buf, newbuf, iphashbuf);
+		if(strncmp(newbuf,"tetrisstart ",12) == 0)
+		    cryptok;
+
+#ifndef NO_BRUTE_FORCE_DECRYPTION
 		/* The IP-based crypt does not work for clients behind NAT. So
 		 * help them by brute-forcing the crypt. This should not be
 		 * even noticeable unless you are running this under ucLinux on
 		 * some XT machine. */
 		for (hashval = 0; hashval < 35956; hashval++) {
 		    sprintf(iphashbuf, "%d", hashval);
-#endif
 		    decrypt_message(buf, newbuf, iphashbuf);
-#ifndef NO_BRUTE_FORCE_DECRYPTION
 		    if(strncmp(newbuf,"tetrisstart ",12) == 0)
-			break;
+			goto cryptok;
 		} /* for (hashval) */
 #endif
+
 		if (strncmp(newbuf, "tetrisstart ", 12) != 0) {
 		    close(fd);
 		    player_socks[i] = -1;
 		    continue;
 		}
+
+cryptok:
 		/* Buffers should be the same size, but let's be paranoid */
 		strncpy(buf, newbuf, sizeof(buf));
 		buf[sizeof(buf)-1] = 0;
 	    } /* if encrypted */
 	    player_socks[i] = fd;  /* Has now registered */
 	} /* if client not registered */
+
 	if (!server_parse(i+1, buf)) {
 	    close(fd);
 	    player_socks[i] = -1;
-- 
2.11.4.GIT