//reads contact info from database and creates Contact objects
private void loadContacts()
{
contactsList.Clear(); //empty list, if reading from database might as well reload everything
SQLiteDataReader reader = db.retrieve("SELECT * FROM Users"); //gets all user records
//if(reader.HasRows) //if any data was read from the DB
Contact contact; //temporary contact object to add to list
while (reader.Read()) //iterate over each tuple returned from the database
{
int ID = Convert.ToInt32((long)reader["userID"]); //sqlite handles primary key field as int64
byte[] encUsername = (byte[])reader["username"];
byte[] encIPAddress = (byte[])reader["IPAddress"];
byte[] IV = (byte[])reader["IV"]; //initialisation vector encUsername and ecnIPAddress were encrypted with
byte[] masterKey = Globals.getMasterKey(); //decrypts and gets master key
string username = CryptoUtility.AESDecrypt(encUsername, masterKey, IV); //decrypt username
string IPAddress = CryptoUtility.AESDecrypt(encIPAddress, masterKey, IV); //decrypt IPAddress
contact = new Contact(ID, username, IPAddress); //puts contact info into object
contactsList.Add(contact);
}
}
/// <summary>
/// Takes the ID of a key in the database and returns a byte array containing the key.
/// This method uses caching as it will be used frequently, this is to prevent unnecessary database reads.
/// </summary>
/// <param name="keyID">ID of key to fetch from keys table</param>
/// <returns>byte[] containing key</returns>
public byte[] getKey(int keyID)
{
if (isCached(keyID)) //check if the key has been cached already
{
return(retrieveFromCache(keyID)); //return cached key
}
else //otherwise get key from database and store it in cache
{
SQLiteDataReader reader = db.retrieve($"SELECT AESKey, IV FROM Keys WHERE keyID = {keyID}"); //will get only one entry
if (!reader.HasRows) //no entry with <keyID>
{
return(new byte[0]); //return empty byte array
}
reader.Read(); //prepares reader to extract values
byte[] encKey = (byte[])reader["AESKey"]; //extract encrypted key
byte[] IV = (byte[])reader["IV"]; //extract initialisation vector it was encrypted with
byte[] key = decryptKey(encKey, IV); //decrypt key
storeInCache(keyID, key); //store in cache
return(key); //return decrypted key
}
}
/// <summary>
/// Takes a contact and returns a list containg all messages exchanged between local and contact.
/// </summary>
/// <param name="contact">Contace for which to get history of exchanges messages</param>
/// <returns>List of messages associated with the provided contact</returns>
public List <Message> getMessageHistory(Contact contact)
{
List <Message> messages = new List <Message>();
Message message; //temp var to hold messages before being put into list
//for <contactID> select every message, initialisation vector to decrypt the message, the ID of the key it's encrypted with, and bool if it was sent or received
SQLiteDataReader reader = db.retrieve($"SELECT sent, message, IV, keyID FROM Messages WHERE (conversationID = \"{contact.ID}\")");
//API BUG - SELECT with explicit fields fails ONLY when the fields are in brackets, lord knows why
while (reader.Read()) //iterate over all existing records
{
bool sent = (bool)reader["sent"]; //extract if message was sent or received
byte[] encMessageBytes = (byte[])reader["message"]; //extract message
byte[] messageIV = (byte[])reader["IV"]; //extract initialisation vector for message
int keyID = Convert.ToInt32((long)reader["keyID"]); //extract ID of key that encrypted message. sqlite handles forien keys to primary keys as int64.
byte[] messageKey = keyManager.getKey(keyID); //gets plain key from manager (must be discarded once done with)
//passes encrypted message bytes, plain key and IV to CryptoUtility and gets decrypted message in return
string messageString = CryptoUtility.AESDecrypt(encMessageBytes, messageKey, messageIV);
messageKey = null; //garbage collect key bytes
int senderID;
int targetID;
if (sent) //message was sent by local
{
senderID = 0;
targetID = contact.ID;
}
else //message was sent by contact
{
senderID = contact.ID;
targetID = 0;
}
message = new Message(messageString, senderID, targetID); //create the message object
messages.Add(message); //store it in list
}
return(messages);
}
