From e3b9927faad1801baf8782855d6008ad58eab086 Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Tue, 7 Dec 2021 10:01:45 +0400
Subject: [PATCH] Reset session on receiving a really old msgId.

---
 .../details/mtproto_received_ids_manager.cpp  | 19 ++++++++++---------
 .../details/mtproto_received_ids_manager.h    |  7 ++++++-
 .../SourceFiles/mtproto/session_private.cpp   | 14 ++++++++++++--
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.cpp b/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.cpp
index 28e6ad518..20bade0c4 100644
--- a/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.cpp
+++ b/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.cpp
@@ -9,18 +9,19 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 
 namespace MTP::details {
 
-bool ReceivedIdsManager::registerMsgId(mtpMsgId msgId, bool needAck) {
+ReceivedIdsManager::Result ReceivedIdsManager::registerMsgId(
+		mtpMsgId msgId,
+		bool needAck) {
 	const auto i = _idsNeedAck.find(msgId);
-	if (i == _idsNeedAck.end()) {
-		if (_idsNeedAck.size() < kIdsBufferSize || msgId > min()) {
-			_idsNeedAck.emplace(msgId, needAck);
-			return true;
-		}
-		MTP_LOG(-1, ("No need to handle - %1 < min = %2").arg(msgId).arg(min()));
-	} else {
+	if (i != _idsNeedAck.end()) {
 		MTP_LOG(-1, ("No need to handle - %1 already is in map").arg(msgId));
+		return Result::Duplicate;
+	} else if (_idsNeedAck.size() < kIdsBufferSize || msgId > min()) {
+		_idsNeedAck.emplace(msgId, needAck);
+		return Result::Success;
 	}
-	return false;
+	MTP_LOG(-1, ("Reset on too old - %1 < min = %2").arg(msgId).arg(min()));
+	return Result::TooOld;
 }
 
 mtpMsgId ReceivedIdsManager::min() const {
diff --git a/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.h b/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.h
index 2a8d6a57a..8f7dfbb9d 100644
--- a/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.h
+++ b/Telegram/SourceFiles/mtproto/details/mtproto_received_ids_manager.h
@@ -21,8 +21,13 @@ public:
 		NeedsAck,
 		NoAckNeeded,
 	};
+	enum class Result {
+		Success,
+		Duplicate,
+		TooOld,
+	};
 
-	bool registerMsgId(mtpMsgId msgId, bool needAck);
+	[[nodiscard]] Result registerMsgId(mtpMsgId msgId, bool needAck);
 	[[nodiscard]] mtpMsgId min() const;
 	[[nodiscard]] mtpMsgId max() const;
 	[[nodiscard]] State lookup(mtpMsgId msgId) const;
diff --git a/Telegram/SourceFiles/mtproto/session_private.cpp b/Telegram/SourceFiles/mtproto/session_private.cpp
index 0bd74787a..ca46f113e 100644
--- a/Telegram/SourceFiles/mtproto/session_private.cpp
+++ b/Telegram/SourceFiles/mtproto/session_private.cpp
@@ -1364,13 +1364,18 @@ void SessionPrivate::handleReceived() {
 			).arg(getProtocolDcId()
 			).arg(_encryptionKey->keyId()));
 
-		if (_receivedMessageIds.registerMsgId(msgId, needAck)) {
+		const auto registered = _receivedMessageIds.registerMsgId(
+			msgId,
+			needAck);
+		if (registered == ReceivedIdsManager::Result::Success) {
 			res = handleOneReceived(from, end, msgId, {
 				.outerMsgId = msgId,
 				.serverSalt = serverSalt,
 				.serverTime = serverTime,
 				.badTime = badTime,
 			});
+		} else if (registered == ReceivedIdsManager::Result::TooOld) {
+			res = HandleResult::ResetSession;
 		}
 		_receivedMessageIds.shrink();
 
@@ -1478,9 +1483,14 @@ SessionPrivate::HandleResult SessionPrivate::handleOneReceived(
 			}
 
 			auto res = HandleResult::Success; // if no need to handle, then succeed
-			if (_receivedMessageIds.registerMsgId(inMsgId.v, needAck)) {
+			const auto registered = _receivedMessageIds.registerMsgId(
+				inMsgId.v,
+				needAck);
+			if (registered == ReceivedIdsManager::Result::Success) {
 				res = handleOneReceived(from, otherEnd, inMsgId.v, info);
 				info.badTime = false;
+			} else if (registered == ReceivedIdsManager::Result::TooOld) {
+				res = HandleResult::ResetSession;
 			}
 			if (res != HandleResult::Success) {
 				return res;