From 0edb52169005774051a49a7e515e753c1bd2dd76 Mon Sep 17 00:00:00 2001
From: Matt Johnston <matt@ucc.asn.au>
Date: Wed, 3 Apr 2013 00:43:31 +0800
Subject: Put some #ifdef options around first-follows options in case they
 need to be disabled

---
 cli-session.c | 5 ++++-
 common-algo.c | 2 ++
 common-kex.c  | 4 ++++
 sysoptions.h  | 9 +++++++++
 4 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/cli-session.c b/cli-session.c
index 9e64281..32b7ac7 100644
--- a/cli-session.c
+++ b/cli-session.c
@@ -110,11 +110,12 @@ void cli_session(int sock_in, int sock_out) {
 
 }
 
+#ifdef USE_KEX_FIRST_FOLLOWS
 static void cli_send_kex_first_guess() {
 	send_msg_kexdh_init();
 	dropbear_log(LOG_INFO, "kexdh_init guess sent");
-	//cli_ses.kex_state = KEXDH_INIT_SENT;			
 }
+#endif
 
 static void cli_session_init() {
 
@@ -155,7 +156,9 @@ static void cli_session_init() {
 
 	ses.isserver = 0;
 
+#ifdef USE_KEX_FIRST_FOLLOWS
 	ses.send_kex_first_guess = cli_send_kex_first_guess;
+#endif
 
 }
 
diff --git a/common-algo.c b/common-algo.c
index b698611..c74463c 100644
--- a/common-algo.c
+++ b/common-algo.c
@@ -216,7 +216,9 @@ algo_type sshhostkey[] = {
 algo_type sshkex[] = {
 	{"diffie-hellman-group14-sha1", DROPBEAR_KEX_DH_GROUP14, NULL, 1, NULL},
 	{"diffie-hellman-group1-sha1", DROPBEAR_KEX_DH_GROUP1, NULL, 1, NULL},
+#ifdef USE_KEXGUESS2
 	{KEXGUESS2_ALGO_NAME, KEXGUESS2_ALGO_ID, NULL, 1, NULL},
+#endif
 	{NULL, 0, NULL, 0, NULL}
 };
 
diff --git a/common-kex.c b/common-kex.c
index eb1fd7b..6c22600 100644
--- a/common-kex.c
+++ b/common-kex.c
@@ -692,7 +692,11 @@ static void read_kex_algos() {
 
 	memset(ses.newkeys, 0x0, sizeof(*ses.newkeys));
 
+#ifdef USE_KEXGUESS2
 	enum kexguess2_used kexguess2 = KEXGUESS2_LOOK;
+#else
+	enum kexguess2_used kexguess2 = KEXGUESS2_NO;
+#endif
 
 	/* kex_algorithms */
 	algo = buf_match_algo(ses.payload, sshkex, &kexguess2, &goodguess);
diff --git a/sysoptions.h b/sysoptions.h
index 4d648c1..22c2a4d 100644
--- a/sysoptions.h
+++ b/sysoptions.h
@@ -23,6 +23,15 @@
 #define AUTH_TIMEOUT 300 /* we choose 5 minutes */
 #endif
 
+/* A client should try and send an initial key exchange packet guessing
+ * the algorithm that will match - saves a round trip connecting, has little
+ * overhead if the guess was "wrong". */
+#define USE_KEX_FIRST_FOLLOWS
+/* Use protocol extension to allow "first follows" to succeed more frequently.
+ * This is currently Dropbear-specific but will gracefully fallback when connecting
+ * to other implementations. */
+#define USE_KEXGUESS2
+
 /* Minimum key sizes for DSS and RSA */
 #ifndef MIN_DSS_KEYLEN
 #define MIN_DSS_KEYLEN 512
-- 
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