From 0a42cedf77aae8bbb6769e7477e485aee3ca1340 Mon Sep 17 00:00:00 2001
From: Bram Matthys <syzop@vulnscan.org>
Date: Sun, 24 May 2015 16:16:31 +0200
Subject: [PATCH] Bounce links that have their clock too far out of sync
 (#4214). Currently set at 1 minute. TODO: make configurable. This only works
 with newer servers as it relies on PROTOCTL TS=xyz very early in the synch.

---
 doc/technical/protoctl.txt |  5 +++++
 src/modules/m_protoctl.c   | 31 +++++++++++++++++++++++++++++++
 src/s_serv.c               |  4 ++--
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/doc/technical/protoctl.txt b/doc/technical/protoctl.txt
index fd6d0cc46..3209a2f27 100644
--- a/doc/technical/protoctl.txt
+++ b/doc/technical/protoctl.txt
@@ -126,3 +126,8 @@ SID           This token indicates that the peer server supports UIDs and SIDs i
 ESVID         This token indicates that the traditional services stamp value may take any
               arbitrary value for the SVID field, such as an account name or other unique
               identifier, including a traditional timestamp value.
+
+TS            Upon linking newer servers send TS=<ts> where <ts> is the current unix
+              timestamp. This way a link can be rejected if the difference between the
+              clock of two servers is too large (since such a difference would lead to
+              serious issues).
diff --git a/src/modules/m_protoctl.c b/src/modules/m_protoctl.c
index 486bf3c67..0ebbb6073 100644
--- a/src/modules/m_protoctl.c
+++ b/src/modules/m_protoctl.c
@@ -348,6 +348,37 @@ CMD_FUNC(m_protoctl)
 			if (!IsHandshake(cptr) && aconf && !BadPtr(aconf->connpwd)) /* Send PASS early... */
 				sendto_one(sptr, "PASS :%s", aconf->connpwd);
 		}
+		else if ((strncmp(s, "TS=",3) == 0) && (IsServer(sptr) || IsEAuth(sptr)))
+		{
+			long t = atol(s+3);
+			char msg[512], linkerr[512];
+			
+			if (t < 10000)
+				continue; /* ignore */
+			
+			*msg = *linkerr = '\0';
+#define MAX_SERVER_TIME_OFFSET 60
+			
+			if ((TStime() - t) > MAX_SERVER_TIME_OFFSET)
+			{
+				snprintf(linkerr, sizeof(linkerr), "Your clock is %ld seconds behind my clock. Please verify both your clock and mine, fix it and try linking again.", TStime() - t);
+				snprintf(msg, sizeof(msg), "Rejecting link %s: our clock is %ld seconds ahead. Correct time is very important in IRC. Please verify the clock on both %s (them) and %s (us), fix it and then try linking again",
+					get_client_name(cptr, TRUE), TStime() - t, sptr->name, me.name);
+			} else
+			if ((t - TStime()) > MAX_SERVER_TIME_OFFSET)
+			{
+				snprintf(linkerr, sizeof(linkerr), "Your clock is %ld seconds ahead of my clock. Please verify both your clock and mine, fix it, and try linking again.", t - TStime());
+				snprintf(msg, sizeof(msg), "Rejecting link %s: our clock is %ld seconds behind. Correct time is very important in IRC. Please verify the clock on both %s (them) and %s (us), fix it and then try linking again",
+					get_client_name(cptr, TRUE), t - TStime(), sptr->name, me.name);
+			}
+			
+			if (*msg)
+			{
+				sendto_realops("%s", msg);
+				ircd_log(LOG_ERROR, "%s", msg);
+				return exit_client(sptr, sptr, sptr, linkerr);
+			}
+		}
 		else if ((strcmp(s, "MLOCK")) == 0)
 		{
 #ifdef PROTOCTL_MADNESS
diff --git a/src/s_serv.c b/src/s_serv.c
index 67003782e..d8c0174f6 100644
--- a/src/s_serv.c
+++ b/src/s_serv.c
@@ -222,8 +222,8 @@ char buf[1024];
 	sendto_one(cptr, "PROTOCTL %s", PROTOCTL_SERVER);
 
 	/* Second line */
-	snprintf(buf, sizeof(buf), "CHANMODES=%s%s,%s%s,%s%s,%s%s NICKCHARS=%s SID=%s MLOCK",
-		CHPAR1, EXPAR1, CHPAR2, EXPAR2, CHPAR3, EXPAR3, CHPAR4, EXPAR4, langsinuse, me.id);
+	snprintf(buf, sizeof(buf), "CHANMODES=%s%s,%s%s,%s%s,%s%s NICKCHARS=%s SID=%s MLOCK TS=%ld",
+		CHPAR1, EXPAR1, CHPAR2, EXPAR2, CHPAR3, EXPAR3, CHPAR4, EXPAR4, langsinuse, me.id, (long)TStime());
 
 	sendto_one(cptr, "PROTOCTL %s", buf);
 }