Refactor PKEK2 related functions

PKEK2 is used to derive both DB DEK and APP DEK. Currently, variable names and
comments are a bit misleading.

This commit refactors the variable names and comments to better describe the
actual purpose of this key.

Change-Id: If8ee266ec2da63c929f498f1ed009df5d79c134f

2 files changed, 12 insertions, 11 deletions

diff --git a/src/manager/service/key-provider.cpp b/src/manager/service/key-provider.cpp
index 18911537..e89af167 100644
--- a/src/manager/service/key-provider.cpp
+++ b/src/manager/service/key-provider.cpp
@@ -146,12 +146,12 @@ KeyData makePKEK1(const KeyComponentsInfo& keyInfo, const Password &password)
 	return key;
 }
 
-// derives a key used for DB DEK encryption (aka PKEK2) from DomainKEK and user id
-KeyData makePKEK2(const uint8_t *domainKEK, const std::string &user)
+// derives a key (PKEK2) from DomainKEK and custom client string (may be a client id or uid)
+KeyData makePKEK2(const uint8_t *domainKEK, const std::string &client)
 {
 	KeyData key;
-	if (!PKCS5_PBKDF2_HMAC_SHA1(user.c_str(),
-	                            user.size(),
+	if (!PKCS5_PBKDF2_HMAC_SHA1(client.c_str(),
+	                            client.size(),
 	                            domainKEK,
 	                            MAX_SALT_SIZE,
 	                            PBKDF2_ITERATIONS,
@@ -413,7 +413,7 @@ RawBuffer KeyProvider::getPureDEK(const RawBuffer &DEKInWrapForm)
 			   (kmcDEK.getKeyAndInfo().key) + kmcDEK.getKeyAndInfo().keyInfo.keyLength);
 }
 
-RawBuffer KeyProvider::generateDEK(const ClientId &client)
+RawBuffer KeyProvider::generateDEK(const std::string &client)
 {
 	if (!m_isInitialized)
 		ThrowErr(Exc::InternalError, "Object not initialized!");
diff --git a/src/manager/service/key-provider.h b/src/manager/service/key-provider.h
index 23523fae..668786ee 100644
--- a/src/manager/service/key-provider.h
+++ b/src/manager/service/key-provider.h
@@ -136,14 +136,15 @@ public:
 	// This api should be used only on Tizen 2.2.1
 	RawBuffer getWrappedDomainKEK(const Password &password);
 
-	// EncryptedKey key extracted from database. Used to encrypt application data.
-	// This key will be used to decrypt/encrypt data in ROW
+	// Unwraps (decrypts) a DEK using a key derived from DomainKEK and data stored in wrapped key
+	// info. It returns the DEK in unencrypted form.
 	RawBuffer getPureDEK(const RawBuffer &DEKInWrapForm);
 
-	// Returns WRAPPED DEK. This will be written to database.
-	// This key will be used to encrypt all application information.
-	// All application are identified by client id.
-	RawBuffer generateDEK(const ClientId &client);
+	// Generates a random DEK and encrypts it using a key derived from DomainKEK and custom client
+	// string (not to be confused with ClientId). The function returns  the DEK in wrapped
+	// (encrypted) form. The function is used to produce a key for database encryption as well as
+	// application keys.
+	RawBuffer generateDEK(const std::string &client);
 
 	// used by change user password. On error -> exception
 	static RawBuffer reencrypt(