PushMsgResult ProcessWelcome(ref Msg msg)
{
if (msg.Size != 168)
{
return(PushMsgResult.Error);
}
Span <byte> welcomeNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
Span <byte> welcomePlaintext = stackalloc byte[128];
Span <byte> welcomeBox = msg.Slice(24, 144);
WelcomeNoncePrefix.CopyTo(welcomeNonce);
msg.Slice(8, 16).CopyTo(welcomeNonce.Slice(8));
using var box = new Curve25519XSalsa20Poly1305(m_cnSecretKey, m_serverKey);
bool isDecrypted = box.TryDecrypt(welcomePlaintext, welcomeBox, welcomeNonce);
if (!isDecrypted)
{
return(PushMsgResult.Error);
}
m_cnServerKey = welcomePlaintext.Slice(0, 32).ToArray();
m_cnCookie = welcomePlaintext.Slice(32, 16 + 80).ToArray();
// Create the curve box
m_box = new Curve25519XSalsa20Poly1305(m_cnSecretKey, m_cnServerKey);
m_state = State.SendInitiate;
return(PushMsgResult.Ok);
}
public bool DecodeEndVerify(EncryptedVote vote, out byte[] decoded)
{
Curve25519XSalsa20Poly1305 box = new Curve25519XSalsa20Poly1305(_privateKey, vote.PublicKey.ParseHexEncodedValue());
var encryptedMessage = vote.Message.ParseHexEncodedValue();
var decryptedMessage = new byte[encryptedMessage.Length - XSalsa20Poly1305.TagLength];
var ret = box.TryDecrypt(decryptedMessage, encryptedMessage, vote.Nonce.ParseHexEncodedValue());
decoded = decryptedMessage;
return(ret);
}
PushMsgResult ProcessHello(ref Msg msg)
{
if (!CheckBasicCommandStructure(ref msg))
{
return(PushMsgResult.Error);
}
Span <byte> hello = msg;
if (!IsCommand("HELLO", ref msg))
{
return(PushMsgResult.Error);
}
if (hello.Length != 200)
{
return(PushMsgResult.Error);
}
byte major = hello[6];
byte minor = hello[7];
if (major != 1 || minor != 0)
{
// client HELLO has unknown version number
return(PushMsgResult.Error);
}
// Save client's short-term public key (C')
hello.Slice(80, 32).CopyTo(m_cnClientKey);
Span <byte> helloNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
HelloNoncePrefix.CopyTo(helloNonce);
hello.Slice(112, 8).CopyTo(helloNonce.Slice(16));
m_peerNonce = NetworkOrderBitsConverter.ToUInt64(hello, 112);
using var box = new Curve25519XSalsa20Poly1305(m_secretKey, m_cnClientKey);
Span <byte> helloPlaintext = stackalloc byte[80];
bool isDecrypted = box.TryDecrypt(helloPlaintext, hello.Slice(120, 80), helloNonce);
if (!isDecrypted)
{
return(PushMsgResult.Error);
}
helloPlaintext.Clear();
m_state = State.SendingWelcome;
return(PushMsgResult.Ok);
}
PushMsgResult ProcessInitiate(ref Msg msg)
{
if (!CheckBasicCommandStructure(ref msg))
{
return(PushMsgResult.Error);
}
Span <byte> initiate = msg;
if (!IsCommand("INITIATE", ref msg))
{
return(PushMsgResult.Error);
}
if (initiate.Length < 257)
{
return(PushMsgResult.Error);
}
Span <byte> cookieNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
Span <byte> cookiePlaintext = stackalloc byte[64];
Span <byte> cookieBox = initiate.Slice(25, 80);
CookieNoncePrefix.CopyTo(cookieNonce);
initiate.Slice(9, 16).CopyTo(cookieNonce.Slice(8));
using var secretBox = new XSalsa20Poly1305(m_cookieKey);
bool decrypted = secretBox.TryDecrypt(cookiePlaintext, cookieBox, cookieNonce);
if (!decrypted)
{
return(PushMsgResult.Error);
}
// Check cookie plain text is as expected [C' + s']
if (!SpanUtility.Equals(m_cnClientKey, cookiePlaintext.Slice(0, 32)) ||
!SpanUtility.Equals(m_cnSecretKey, cookiePlaintext.Slice(32, 32)))
{
return(PushMsgResult.Error);
}
Span <byte> initiateNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
byte[] initiatePlaintext = new byte[msg.Size - 113];
var initiateBox = initiate.Slice(113);
InitiatieNoncePrefix.CopyTo(initiateNonce);
initiate.Slice(105, 8).CopyTo(initiateNonce.Slice(16));
m_peerNonce = NetworkOrderBitsConverter.ToUInt64(initiate, 105);
using var box = new Curve25519XSalsa20Poly1305(m_cnSecretKey, m_cnClientKey);
bool decrypt = box.TryDecrypt(initiatePlaintext, initiateBox, initiateNonce);
if (!decrypt)
{
return(PushMsgResult.Error);
}
Span <byte> vouchNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
Span <byte> vouchPlaintext = stackalloc byte[64];
Span <byte> vouchBox = new Span <byte>(initiatePlaintext, 48, 80);
var clientKey = new Span <byte>(initiatePlaintext, 0, 32);
VouchNoncePrefix.CopyTo(vouchNonce);
new Span <byte>(initiatePlaintext, 32, 16).CopyTo(vouchNonce.Slice(8));
using var box2 = new Curve25519XSalsa20Poly1305(m_cnSecretKey, clientKey);
decrypt = box2.TryDecrypt(vouchPlaintext, vouchBox, vouchNonce);
if (!decrypt)
{
return(PushMsgResult.Error);
}
// What we decrypted must be the client's short-term public key
if (!SpanUtility.Equals(vouchPlaintext.Slice(0, 32), m_cnClientKey))
{
return(PushMsgResult.Error);
}
// Create the session box
m_box = new Curve25519XSalsa20Poly1305(m_cnSecretKey, m_cnClientKey);
// This supports the Stonehouse pattern (encryption without authentication).
m_state = State.SendingReady;
if (!ParseMetadata(new Span <byte>(initiatePlaintext, 128, initiatePlaintext.Length - 128 - 16)))
{
return(PushMsgResult.Error);
}
vouchPlaintext.Clear();
Array.Clear(initiatePlaintext, 0, initiatePlaintext.Length);
return(PushMsgResult.Ok);
}
public override PushMsgResult Decode(ref Msg msg)
{
if (!CheckBasicCommandStructure(ref msg))
{
return(PushMsgResult.Error);
}
int size = msg.Size;
if (!IsCommand("MESSAGE", ref msg))
{
return(PushMsgResult.Error);
}
if (size < 33) // Size of 16 bytes of command + 16 bytes of MAC + 1 byte for flag
{
return(PushMsgResult.Error);
}
Span <byte> messageNonce = stackalloc byte[Curve25519XSalsa20Poly1305.NonceLength];
m_decodeNoncePrefix.CopyTo(messageNonce);
msg.Slice(8, 8).CopyTo(messageNonce.Slice(16));
UInt64 nonce = NetworkOrderBitsConverter.ToUInt64(msg, 8);
if (nonce <= m_peerNonce)
{
return(PushMsgResult.Error);
}
m_peerNonce = nonce;
Msg plain = new Msg();
plain.InitPool(msg.Size - 16 - Curve25519XSalsa20Poly1305.TagLength);
var isAuthenticate = m_box.TryDecrypt(plain, msg.Slice(16), messageNonce);
if (!isAuthenticate)
{
plain.Close();
return(PushMsgResult.Error);
}
msg.Move(ref plain);
byte flags = msg[0];
if ((flags & 0x01) != 0)
{
msg.SetFlags(MsgFlags.More);
}
if ((flags & 0x02) != 0)
{
msg.SetFlags(MsgFlags.Command);
}
msg.TrimPrefix(1);
return(PushMsgResult.Ok);
}
