From 3e3d367c98854bd8ce6397a2163d664bf8fa7b38 Mon Sep 17 00:00:00 2001
From: JoelKatz <DavidJoelSchwartz@GMail.com>
Date: Sun, 5 Aug 2012 00:39:06 -0700
Subject: [PATCH] Finalizations, cleanup, and security improvements.

---
 src/SNTPClient.cpp | 42 ++++++++++++++++++++++++++++++++----------
 src/SNTPClient.h   |  1 +
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/src/SNTPClient.cpp b/src/SNTPClient.cpp
index 7f652fa401..e86edca76e 100644
--- a/src/SNTPClient.cpp
+++ b/src/SNTPClient.cpp
@@ -11,6 +11,24 @@ static uint8_t SNTPQueryData[48] = {
 	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 };
 
+// NTP timestamp constant
+#define NTP_UNIX_OFFSET			0x83AA7E80
+
+// SNTP packet offsets
+#define NTP_OFF_INFO			0
+#define NTP_OFF_ROOTDELAY		1
+#define NTP_OFF_ROOTDISP		2
+#define NTP_OFF_REFERENCEID		3
+#define NTP_OFF_REFTS_INT		4
+#define NTP_OFF_REFTS_FRAC		5
+#define NTP_OFF_ORGTS_INT		6
+#define NTP_OFF_ORGTS_FRAC		7
+#define NTP_OFF_RECVTS_INT		8
+#define NTP_OFF_RECVTS_FRAC		9
+#define NTP_OFF_XMITTS_INT		10
+#define NTP_OFF_XMITTS_FRAC		11
+
+
 SNTPClient::SNTPClient(boost::asio::io_service& service) :
 		mIOService(service), mSocket(service), mTimer(service), mResolver(service),
 		mOffset(0), mLastOffsetUpdate((time_t) -1), mReceiveBuffer(256)
@@ -45,7 +63,10 @@ void SNTPClient::resolveComplete(const boost::system::error_code& error, boost::
 			}
 			query.mReceivedReply = false;
 			query.mLocalTimeSent = now;
-			mSocket.async_send_to(boost::asio::buffer(SNTPQueryData, 256), *sel,
+			query.mQueryMagic = rand();
+			reinterpret_cast<uint32*>(SNTPQueryData)[NTP_OFF_XMITTS_INT] = time(NULL) + NTP_UNIX_OFFSET;
+			reinterpret_cast<uint32*>(SNTPQueryData)[NTP_OFF_XMITTS_FRAC] = query.mQueryMagic;
+			mSocket.async_send_to(boost::asio::buffer(SNTPQueryData, 48), *sel,
 				boost::bind(&SNTPClient::sendComplete, this,
 					boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
 		}
@@ -68,11 +89,12 @@ void SNTPClient::receivePacket(const boost::system::error_code& error, std::size
 			query->second.mReceivedReply = true;
 			if (time(NULL) > (query->second.mLocalTimeSent + 1))
 				Log(lsWARNING) << "SNTP: Late response";
+			else if (bytes_xferd < 48)
+				Log(lsWARNING) << "SNTP: Short reply (" << bytes_xferd << ") " << mReceiveBuffer.size();
+			else if (reinterpret_cast<uint32*>(&mReceiveBuffer[0])[NTP_OFF_ORGTS_FRAC] != query->second.mQueryMagic)
+				Log(lsWARNING) << "SNTP: Reply had wrong magic number";
 			else
-				if (bytes_xferd < 48)
-					Log(lsWARNING) << "SNTP: Short reply (" << bytes_xferd << ") " << mReceiveBuffer.size();
-				else
-					processReply();
+				processReply();
 		}
 	}
 
@@ -92,8 +114,8 @@ void SNTPClient::processReply()
 	assert(mReceiveBuffer.size() >= 48);
 	uint32 *recvBuffer = reinterpret_cast<uint32*>(&mReceiveBuffer.front());
 
-	unsigned info = ntohl(recvBuffer[0]);
-	int64_t timev = ntohl(recvBuffer[8]);
+	unsigned info = ntohl(recvBuffer[NTP_OFF_INFO]);
+	int64_t timev = ntohl(recvBuffer[NTP_OFF_RECVTS_INT]);
 	unsigned stratum = (info >> 16) & 0xff;
 
 	if ((info >> 30) == 3)
@@ -109,7 +131,7 @@ void SNTPClient::processReply()
 
 	time_t now = time(NULL);
 	timev -= now;
-	timev -= 0x83AA7E80ULL;
+	timev -= NTP_UNIX_OFFSET;
 	Log(lsTRACE) << "SNTP: Offset is " << timev;
 
 	if ((mLastOffsetUpdate == (time_t) -1) || (mLastOffsetUpdate < (now - 180)))
@@ -181,7 +203,7 @@ bool SNTPClient::doQuery()
 	time_t now = time(NULL);
 	if ((best->second == now) || (best->second == (now - 1)))
 	{
-		Log(lsINFO) << "SNTP: All servers recently queried";
+		Log(lsTRACE) << "SNTP: All servers recently queried";
 		return false;
 	}
 	best->second = now;
@@ -190,6 +212,6 @@ bool SNTPClient::doQuery()
 	mResolver.async_resolve(query,
 		boost::bind(&SNTPClient::resolveComplete, this,
 		boost::asio::placeholders::error, boost::asio::placeholders::iterator));
-	Log(lsINFO) << "SNTP: Resolve pending for " << best->first;
+	Log(lsTRACE) << "SNTP: Resolve pending for " << best->first;
 	return true;
 }
diff --git a/src/SNTPClient.h b/src/SNTPClient.h
index 8e6489a0a9..f8b00c071d 100644
--- a/src/SNTPClient.h
+++ b/src/SNTPClient.h
@@ -13,6 +13,7 @@ class SNTPQuery
 public:
 	bool				mReceivedReply;
 	time_t				mLocalTimeSent;
+	int					mQueryMagic;
 
 	SNTPQuery(time_t j = (time_t) -1)	: mReceivedReply(false), mLocalTimeSent(j) { ; }
 };