From 75c2d19666087e654733a0c4059912ed6defd2b6 Mon Sep 17 00:00:00 2001
From: Krzysztof Jackiewicz <k.jackiewicz@samsung.com>
Date: Fri, 24 Nov 2017 11:03:45 +0100
Subject: [PATCH] Protect file footer from concurrent access

Add mutex synchronisation.

Can't use runtime::File locks because it's not possible to truncate a file
during writing without closing the descriptor (and unlocking the lock).
Derivation won't help either as the descriptor is private.

Change-Id: I5e22b21dca48b1b3d17ae6b2e4084c1029f84089
---
 server/key-server.cpp | 87 ++++++++++++++++++++++++++-------------------------
 server/key-server.h   |  6 ++++
 2 files changed, 50 insertions(+), 43 deletions(-)

diff --git a/server/key-server.cpp b/server/key-server.cpp
index a0b00dd..4ab6541 100644
--- a/server/key-server.cpp
+++ b/server/key-server.cpp
@@ -88,6 +88,8 @@ int KeyServer::initAndGet(const std::string& dev,
 	masterKey = KeyGenerator::RNG(KEY_SIZE.at(params));
 
 	EncryptedKey ek(masterKey, password);
+
+	std::lock_guard<std::mutex> lock(footerLock);
 	FileFooter::write(dev, ek.serialize());
 
 	return error::None;
@@ -95,12 +97,14 @@ int KeyServer::initAndGet(const std::string& dev,
 
 int KeyServer::remove(const std::string& dev, const std::string& password)
 {
-	int ret = verifyPassword(dev, password);
-	if (ret != error::None) {
-		if (ret == error::WrongPassword)
-			ERROR(SINK, "Wrong password passed.");
+	if (dev.empty() || password.empty())
+		return error::InvalidParameter;
+
+	std::lock_guard<std::mutex> lock(footerLock);
+	BinaryData key;
+	int ret = internalGet(dev, password, key);
+	if (ret != error::None)
 		return ret;
-	}
 
 	FileFooter::clear(dev);
 	return error::None;
@@ -113,8 +117,9 @@ int KeyServer::changePassword(const std::string& dev,
 	if (dev.empty() || curPassword.empty() || newPassword.empty())
 		return error::InvalidParameter;
 
+	std::lock_guard<std::mutex> lock(footerLock);
 	if (!FileFooter::exist(dev)) {
-		ERROR(SINK, "Given device has no master key");
+		ERROR(SINK, "Given device has no master key.");
 		return error::NoSuchFile;
 	}
 
@@ -122,9 +127,10 @@ int KeyServer::changePassword(const std::string& dev,
 
 	auto key = ek.decrypt(curPassword);
 	if (key.empty()) {
-		ERROR(SINK, "Wrong password passed");
+		ERROR(SINK, "Wrong password passed.");
 		return error::WrongPassword;
 	}
+
 	ek.encrypt(key, newPassword);
 
 	FileFooter::write(dev, ek.serialize());
@@ -137,18 +143,9 @@ int KeyServer::verifyPassword(const std::string& dev,
 	if (dev.empty() || password.empty())
 		return error::InvalidParameter;
 
-	if (!FileFooter::exist(dev)) {
-		ERROR(SINK, "Given device has no master key");
-		return error::NoSuchFile;
-	}
-
-	EncryptedKey ek(FileFooter::read(dev));
-
-	auto key = ek.decrypt(password);
-	if (key.empty())
-		return error::WrongPassword;
-
-	return error::None;
+	BinaryData dummy;
+	std::lock_guard<std::mutex> lock(footerLock);
+	return internalGet(dev, password, dummy);
 }
 
 int KeyServer::get(const std::string& dev,
@@ -158,19 +155,8 @@ int KeyServer::get(const std::string& dev,
 	if (dev.empty() || password.empty())
 		return error::InvalidParameter;
 
-	if (!FileFooter::exist(dev)) {
-		ERROR(SINK, "Given device has no master key");
-		return error::NoSuchFile;
-	}
-
-	EncryptedKey ek(FileFooter::read(dev));
-
-	masterKey = ek.decrypt(password);
-	if (masterKey.empty()) {
-		ERROR(SINK, "Wrong password passed");
-		return error::WrongPassword;
-	}
-	return error::None;
+	std::lock_guard<std::mutex> lock(footerLock);
+	return internalGet(dev, password, masterKey);
 }
 
 void KeyServer::removePassword(const std::string& dev)
@@ -178,6 +164,7 @@ void KeyServer::removePassword(const std::string& dev)
 	if (dev.empty())
 		return;
 
+	std::lock_guard<std::mutex> lock(footerLock);
 	FileFooter::clear(dev);
 }
 
@@ -187,18 +174,13 @@ int KeyServer::storeMasterKey(const std::string& dev,
 	if (dev.empty() || password.empty())
 		return error::InvalidParameter;
 
-	if (!FileFooter::exist(dev)) {
-		ERROR(SINK, "Given device has no master key");
-		return error::NoSuchFile;
-	}
-
-	EncryptedKey ek(FileFooter::read(dev));
+	std::unique_lock<std::mutex> lock(footerLock);
+	BinaryData masterKey;
+	int ret = internalGet(dev, password, masterKey);
+	if (ret != error::None)
+		return ret;
 
-	auto masterKey = ek.decrypt(password);
-	if (masterKey.empty()) {
-		ERROR(SINK, "Wrong password passed");
-		return error::WrongPassword;
-	}
+	lock.unlock();
 
 	try {
 		UpgradeSupport::storeMasterKey(dev, masterKey);
@@ -223,4 +205,23 @@ int KeyServer::removeMasterKey(const std::string& dev)
 	return error::None;
 }
 
+int KeyServer::internalGet(const std::string& dev,
+						   const std::string& password,
+						   BinaryData& key) const
+{
+	if (!FileFooter::exist(dev)) {
+		ERROR(SINK, "Given device has no master key.");
+		return error::NoSuchFile;
+	}
+
+	EncryptedKey ek(FileFooter::read(dev));
+
+	key = ek.decrypt(password);
+	if (key.empty()) {
+		ERROR(SINK, "Wrong password passed.");
+		return error::WrongPassword;
+	}
+	return error::None;
+}
+
 } // namespace ode
diff --git a/server/key-server.h b/server/key-server.h
index 244719b..a37f442 100644
--- a/server/key-server.h
+++ b/server/key-server.h
@@ -18,6 +18,7 @@
 #define __KEY_SERVER_H__
 
 #include <string>
+#include <mutex>
 
 #include "rmi/key.h"
 #include "server.h"
@@ -48,7 +49,12 @@ public:
 	int removeMasterKey(const std::string& dev);
 
 private:
+	int internalGet(const std::string& dev,
+					const std::string& password,
+					BinaryData& key) const;
+
 	ServerContext& server;
+	mutable std::mutex footerLock;
 };
 
 } // namespace ode
-- 
2.7.4