/// <summary>
/// Initializes a new instance of the <see cref="Protocol"/> class.
/// </summary>
/// <param name="handshakePattern">The handshake pattern (e.q. NX or IK).</param>
/// <param name="cipher">The cipher function (AESGCM or ChaChaPoly).</param>
/// <param name="hash">The hash function (SHA256, SHA512, BLAKE2s, or BLAKE2b).</param>
/// <param name="modifiers">The combination of pattern modifiers (e.q. empty, psk0, or psk1+psk2).</param>
/// <exception cref="ArgumentNullException">
/// Thrown if the either <paramref name="handshakePattern"/>,
/// <paramref name="cipher"/>, or <paramref name="hash"/> is null.
/// </exception>
/// <exception cref="ArgumentException">
/// Thrown if <paramref name="modifiers"/> does not represent a valid combination of pattern modifiers.
/// </exception>
public Protocol(
HandshakePattern handshakePattern,
CipherFunction cipher,
HashFunction hash,
PatternModifiers modifiers = PatternModifiers.None)
{
Exceptions.ThrowIfNull(handshakePattern, nameof(handshakePattern));
Exceptions.ThrowIfNull(cipher, nameof(cipher));
Exceptions.ThrowIfNull(hash, nameof(hash));
HandshakePattern = handshakePattern;
Cipher = cipher;
Dh = DhFunction.Curve25519;
Hash = hash;
Modifiers = modifiers;
Name = GetName();
}
/// <summary>
/// Converts the Noise protocol name to its <see cref="Protocol"/> equivalent.
/// </summary>
/// <param name="s">The Noise protocol name (e.q. Noise_KNpsk2_25519_ChaChaPoly_SHA512).</param>
/// <returns>
/// An object that is equivalent to the Noise
/// protocol name contained in <paramref name="s"/>.
/// </returns>
/// <exception cref="ArgumentException">
/// Thrown if <paramref name="s"/> is not a valid Noise protocol name.
/// </exception>
public static Protocol Parse(ReadOnlySpan <char> s)
{
if (s.Length < MinProtocolNameLength || s.Length > MaxProtocolNameLength)
{
throw new ArgumentException("Invalid Noise protocol name.", nameof(s));
}
var splitter = new StringSplitter(s, '_');
var noise = splitter.Next();
if (!noise.SequenceEqual("Noise".AsSpan()))
{
throw new ArgumentException("Invalid Noise protocol name.", nameof(s));
}
var next = splitter.Next();
var pattern = next.Length > 1 && Char.IsUpper(next[1]) ? next.Slice(0, 2) : next.Slice(0, 1);
var handshakePattern = ParseHandshakePattern(pattern);
var modifiers = ParseModifiers(next.Slice(pattern.Length));
var dh = DhFunction.Parse(splitter.Next());
Debug.Assert(dh == DhFunction.Curve25519);
var cipher = CipherFunction.Parse(splitter.Next());
var hash = HashFunction.Parse(splitter.Next());
if (!splitter.Next().IsEmpty)
{
throw new ArgumentException("Invalid Noise protocol name.", nameof(s));
}
var protocol = new Protocol(handshakePattern, cipher, hash, modifiers);
ValidateProtocolName(s, protocol);
return(protocol);
}