diff --git a/README.md b/README.md index d5f545e..65f2860 100644 --- a/README.md +++ b/README.md @@ -19,6 +19,24 @@ ## client todo: [ ] Check for key when turned on - [ ] generate key and register if no key is preset, and save it after registration is done - [ ] if key is present, start by getting messages (which makes sure we are signed in) + [x] generate key and register if no key is preset, and save it after registration is done + [ ] if key is present, start by establishing connection (which makes sure we are signed in) +[ ] use AES to get basic packets from the server +[ ] use RSA private key to read normal messages + +## Server todo: + +[ ] Laucnh task for each new connection +[ ] use RSA key to get first message and extract AES key +[ ] verify the user using its public RSA key + [ ] if it was a register session save the key into the BIG DATA STRUCTURE +[ ] Keep lists of incoming messages + (doesnt need to know from who, they are just big blobs of shlomp) +[ ] When user asks for incoming messages, make basic packet and append the incoming messages + - last byte is the "how many messages are left" byte + - each byte in the extra data will be the length of the next message, so + if there are 3 messages of length 128, 200, 300 bytes it will be + [128, 200, 300, 0 ...] and the actual position in the payload is easy + to calculate ([128, 200+128=328, 300+328=628, ...]) + diff --git a/client/Program.cs b/client/Program.cs index a198e26..7d4387e 100644 --- a/client/Program.cs +++ b/client/Program.cs @@ -4,58 +4,161 @@ using System.Text; using System.Threading.Tasks; using System.Security.Cryptography; using System.Linq; +using System.IO; +using lib; namespace Client; public class Program { - static void Main(string[] args) + static async Task Main(string[] args) { - - RSA key = RSA.Create(512); - Console.WriteLine($"key: {key.ExportRSAPrivateKey().Length}"); - Console.WriteLine(key.ExportRSAPublicKeyPem()); + string user = args + .SkipWhile(a => !new[] { "-p", "--phone" }.Contains(a)) // search for the option + .Skip(1) // skip the `-u/--user` itself to get the value + .FirstOrDefault() ?? "0000"; // get the value or deafult if it doesnt exist + + // On boot, check if a key is available + RSA serverKey = LoadRSAFromFile("key_server.pem")!; + RSA pubKey = LoadRSAFromFile($"pubkey_{user}.pem") ?? RSA.Create(2048); + RSA privKey = LoadRSAFromFile($"privkey_{user}.pem") ?? pubKey; + + SaveRSAKeys(user, pubKey, privKey); using TcpClient client = new("127.0.0.1", 12345); - byte[] toSend = Encoding.ASCII.GetBytes("hello server"); - var stream = client.GetStream(); + // First contact init + bool needsRegister = pubKey == privKey || args.Any(a => new[] { "-fr", "--force-register" }.Contains(a)); + Aes sk = Aes.Create(); // creates an AES-256 key + if (needsRegister) + { + while(true) { + try { + await RegisterClient(user, pubKey, privKey, serverKey, sk, stream); + } + catch (Exception ex) { + Console.WriteLine("Failed registration process"); + Console.WriteLine("Exception: " + ex.Message); + Console.WriteLine("Stack: " + ex.StackTrace); + } + } + } + else + { + + } + + var inputTask = Task.Run(async () => await HandleUserInput(client, stream)); var serverInput = Task.Run(async () => await HandleServerInput(client, stream)); _ = Task.WaitAny(inputTask, serverInput); - + } - - static async Task HandleUserInput(TcpClient client, NetworkStream stream) { - while(client.Connected) { + + async static Task RegisterClient(string user, RSA pub, RSA priv, RSA server, Aes sk, NetworkStream stream) + { + byte counter = 0; + // first send the `Register` message + byte[] pubBytes = pub.ExportRSAPublicKey(); + byte[] data = new byte[16]; + Array.Copy(Utils.NumberToBytes(user), data, 8); + Array.Copy(BitConverter.GetBytes(pubBytes.Length), 0, data, 8, 4); + Array.Copy(BitConverter.GetBytes(sk.Key.Length), 0, data, 12, 4); + byte[] msg = Request.CreateRequest(RequestType.Register, ref counter, data); + byte[] finalPayload = [.. msg, .. pubBytes, .. sk.Key]; + // signing a hash here is pretty useless tbh + // if oscar is changing this message somehow it will just fail the registration process and will restart eventually + // so kinda pointless, esp when its signed with the server's key + byte[] enc = server.Encrypt(finalPayload, RSAEncryptionPadding.OaepSHA256); + await stream.WriteAsync(enc); + // get the 6 digit code + byte[] digits = new byte[6]; + await stream.ReadExactlyAsync(digits, 0, 6); + // print the 6 digit code + Console.WriteLine($"[{DateTime.Now}] 6 digit code: {string.Join(' ',digits.Select(d => d.ToString()))}"); + // get the 6 digit code from the user + while(true) { + string? code = Console.ReadLine()?.Trim(); + if(code == null || code.Take(6).Any(c => !char.IsDigit(c))) { + Console.WriteLine("Invalid code!"); + continue; + } + byte[] codeBytes = code + .Take(6) // take the first 6 characters + .Select(d => byte.Parse(d.ToString())) // parse into bytes + .ToArray(); + msg = Request.CreateRequest(RequestType.ConfirmRegister, ref counter, codeBytes); + byte[] signed = priv.SignData(msg, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1); + enc = sk.EncryptCfb(msg, Array.Empty(), PaddingMode.None); // no reason to encrpy the signature + finalPayload = [.. enc, .. signed]; // should be 128 (enc) + 256 (signed) + await stream.WriteAsync(finalPayload); + int incoming = await stream.ReadAsync(enc); + msg = sk.DecryptCfb(enc[..incoming], Array.Empty(), PaddingMode.Zeros); + string r = Encoding.UTF8.GetString(msg); + if(r == "OK") { + Console.WriteLine("Registration process complete"); + break; + } + } + } + + static RSA? LoadRSAFromFile(string file) + { + if (File.Exists(file)) + { + string content = File.ReadAllText(file); + RSA k = RSA.Create(); + k.ImportFromPem(content); + return k; + } + return null; + } + + static void SaveRSAKeys(string user, RSA pub, RSA priv) + { + File.WriteAllText($"pubkey_{user}.pem", pub.ExportRSAPublicKeyPem()); + File.WriteAllText($"privkey_{user}.pem", priv.ExportRSAPrivateKeyPem()); + } + + static async Task HandleUserInput(TcpClient client, NetworkStream stream) + { + while (client.Connected) + { string? input = Console.ReadLine(); - if(input == null) { + if (input == null) + { await Task.Delay(100); continue; } - else if(input.StartsWith('/')) { + else if (input.StartsWith('/')) + { // Commands :D, i like commands - switch(input.ToLower()) { + switch (input.ToLower()) + { case "/quit": case "/exit": case "/q!": return; } } - else { + else + { stream.Write(Encoding.ASCII.GetBytes(input)); Console.WriteLine($"[{DateTime.Now}]Sent to server: {input}"); } } } - static async Task HandleServerInput(TcpClient client, NetworkStream stream) { + static async Task HandleServerInput(TcpClient client, NetworkStream stream) + { byte[] buffer = new byte[1024]; - while(client.Connected) { + while (client.Connected) + { int readLen = await stream.ReadAsync(buffer); - if(readLen != 0) { + if (readLen != 0) + { string fromServer = Encoding.ASCII.GetString(buffer[..readLen]); Console.WriteLine($"[{DateTime.Now}] From server: {fromServer}"); diff --git a/lib/Crypto.cs b/lib/Crypto.cs deleted file mode 100644 index 30d4c2b..0000000 --- a/lib/Crypto.cs +++ /dev/null @@ -1,11 +0,0 @@ -using System.Security.Cryptography; - -namespace lib; - -public static class Crypto { - public static RSA GenerateKey() { - return RSA.Create(512); - } - - -} \ No newline at end of file diff --git a/lib/Request.cs b/lib/Request.cs index e954151..56e8695 100644 --- a/lib/Request.cs +++ b/lib/Request.cs @@ -3,8 +3,31 @@ public enum RequestType { Register = 1, ConfirmRegister = 2, - GetMessages = 3, - GetUserKey = 4, - SendMessage = 5, - SendAck = 6 + Login = 3, + GetMessages = 4, + GetUserKey = 5, + SendMessage = 6, +} + +public static class Request { + public static byte[] CreateRequest(RequestType Type, ref byte counter, byte[] data) { + if(data.Length > 13) { + throw new Exception("extra data is too long"); + } + + byte[] msg = new byte[128]; + msg[0] = 0; // version + msg[1] = (byte)Type; + msg[2] = counter; + if(counter == byte.MaxValue) { + counter = 0; + } + else { + counter += 1; + } + + // insert data 3..16 + Array.Copy(data, 0, msg, 3, data.Length); + return msg; + } } \ No newline at end of file diff --git a/protocol.md b/protocol.md index a691e53..657333b 100644 --- a/protocol.md +++ b/protocol.md @@ -48,32 +48,30 @@ to the server. ## "Control" requests -- Register `(phone, pub RSA key)` - extra data: RSA key size (payload length) +- Register: + data: Phone - 8 bytes, RSA key size (payload length) - 2 bytes, AES key length - 2 bytes - ConfirmRegister (signed & encrypted 6 digit code) - extra data: 6 bytes for the 6 digit code (can use less but it will be padding otherwise) -- GetMessages (signed & encrypted to not allow someone to "flush" someone else's msgs) - extra data: EMPTY + data: 6 bytes for the 6 digit code (can use less but it will be padding otherwise) +- Login (signed hash): + data: 8 bytes of user's phone, AES key length - 2 bytes, signed SHA length - 2 bytes +- GetMessages: + data: EMPTY - GetUserKey (dont think it needs any signing or encryption technically, as it is very simple registering and "stealing" a key outside the system, keys are assumed to be unbreakable) extra data: 8 bytes (4 bits per digit) of whoever we want to get the key of - SendMessage `(to_user, msg_id, EM from d above)` - extra data: 8 bytes (4 bits per digit) of who to send the data, 4 bytes (32bit) for length -- SendAck `(to_user, msg_id - signed and encrypted)` - - server doesnt know if the msg itself is indeed valid and not tempered with - extra data: 8 bytes (4 bits per digit) of who to send the data, 4 bytes (32bit) for length - + extra data: 8 bytes (4 bits per digit) of who to send the data, 4 bytes (32bit) for length in bytes I think it all can go into a: ``` { Version byte (0) - 1 byte RequestType - 1 byte, - Phone number - 8 bytes (every 4 bits is a number, so we have 16 numbers), - UTC timestamp - 8 bytes (long), - extra data (based on the request given) - up to 18 bytes -} = 32 bytes = 256 bits + looping counter - 1 bytes (long), could be replaced by a counter, that can be 1 looping byte, thus + data - up to 13, +} = 16 bytes = 128 bits ``` + and we can just append encrypted payloads to it (in SendMessage and SendAck) To each message we also append a sha3-256 signed hash, this shit really feels like overkill and im not sure about it, @@ -83,5 +81,26 @@ amusingly long for the amount of data the server needs to encrypt enc_server( request - 256 bits, signed sha3-256 ) which means: - Keys: RSA-512 - Hashes: SHA3-256 \ No newline at end of file + public keys: RSA-2048/1024 (not sure what i need here honestly) + Hashes: SHA3-256 + symmetric keys: AES-256 + +scrape that... seems it wouldnt work as expected since it doesnt work that way +with RSA i think maybe not im not sure... + +thinking right now about an RSA-2048 key (for sEcUrItY), +then starting a connection will be whatever the user wants, and optionally +an AES-128 (because its only for 1 session) key to use for subsequent messages, +this allows the user to NOT encrypt everything with RSA keys, it still means the +server has to decrypt and verify a signature for the first message (and either return +an error or force close the connection if the sig is invalid and all) + +this somewhat applies for the register messages, you send a payload with an AES key +and a public RSA key, then in `ConfirmRegister` the key is still being signed with +the user's RSA, but then encrypted using the AES session key. + +Messages between users will still be done using public RSA keys, +which honestly can be both 1024, or 2048 as far as im aware, prob should also be +2048, that means the server needs to do 2 RSA encryptions per session +(or 2 for the registration itself, which is then auto-validating the session) + diff --git a/server/Program.cs b/server/Program.cs index e361765..fcc4cc0 100644 --- a/server/Program.cs +++ b/server/Program.cs @@ -1,6 +1,8 @@ using System; +using System.IO; using System.Net; using System.Net.Sockets; +using System.Security.Cryptography; namespace Server; @@ -8,6 +10,11 @@ public class Program { static void Main(string[] args) { + // Generally this key would be static but since its not production yet we can generate it every time to make sure + // the users has the key and could load it from file + RSA key = RSA.Create(2048); + File.WriteAllText("server_key.pem", key.ExportRSAPublicKeyPem()); + int port = 12345; TcpListener server = new(IPAddress.Parse("0.0.0.0"), port); try {