/// <summary>
/// Do the authentication part of Tor's SOCKS5 protocol.
/// </summary>
/// <param name="isolateStream">Whether random username/password should be used for authentication and thus effectively create a new Tor circuit.</param>
/// <remarks>Tor process must be started with enabled <c>IsolateSOCKSAuth</c> option. It's ON by default.</remarks>
/// <seealso href="https://www.torproject.org/docs/tor-manual.html.en"/>
/// <seealso href="https://linux.die.net/man/1/tor">For <c>IsolateSOCKSAuth</c> option explanation.</seealso>
/// <seealso href="https://gitweb.torproject.org/torspec.git/tree/socks-extensions.txt#n35"/>
public async Task HandshakeAsync(bool isolateStream = false, CancellationToken cancellationToken = default)
{
Logger.LogDebug($"> {nameof(isolateStream)}={isolateStream}");
// https://github.com/torproject/torspec/blob/master/socks-extensions.txt
// The "NO AUTHENTICATION REQUIRED" (SOCKS5) authentication method [00] is
// supported; and as of Tor 0.2.3.2 - alpha, the "USERNAME/PASSWORD"(SOCKS5)
// authentication method[02] is supported too, and used as a method to
// implement stream isolation.As an extension to support some broken clients,
// we allow clients to pass "USERNAME/PASSWORD" authentication message to us
// even if no authentication was selected.Furthermore, we allow
// username / password fields of this message to be empty. This technically
// violates RFC1929[4], but ensures interoperability with somewhat broken
// SOCKS5 client implementations.
var methods = new MethodsField(isolateStream ? MethodField.UsernamePassword : MethodField.NoAuthenticationRequired);
byte[] receiveBuffer = await SendRequestAsync(new VersionMethodRequest(methods), cancellationToken).ConfigureAwait(false);
var methodSelection = new MethodSelectionResponse(receiveBuffer);
if (methodSelection.Ver != VerField.Socks5)
{
throw new NotSupportedException($"SOCKS{methodSelection.Ver.Value} not supported. Only SOCKS5 is supported.");
}
else if (methodSelection.Method == MethodField.NoAcceptableMethods)
{
// https://www.ietf.org/rfc/rfc1928.txt
// If the selected METHOD is X'FF', none of the methods listed by the
// client are acceptable, and the client MUST close the connection.
DisposeTcpClient();
throw new NotSupportedException("Tor's SOCKS5 proxy does not support any of the client's authentication methods.");
}
else if (methodSelection.Method == MethodField.UsernamePassword)
{
// https://tools.ietf.org/html/rfc1929#section-2
// Once the SOCKS V5 server has started, and the client has selected the
// Username / Password Authentication protocol, the Username / Password
// sub-negotiation begins. This begins with the client producing a
// Username / Password request:
var identity = RandomString.CapitalAlphaNumeric(21);
var uName = new UNameField(uName: identity);
var passwd = new PasswdField(password: identity);
var usernamePasswordRequest = new UsernamePasswordRequest(uName, passwd);
receiveBuffer = await SendRequestAsync(usernamePasswordRequest, cancellationToken).ConfigureAwait(false);
var userNamePasswordResponse = new UsernamePasswordResponse(receiveBuffer);
if (userNamePasswordResponse.Ver != usernamePasswordRequest.Ver)
{
throw new NotSupportedException($"Authentication version {userNamePasswordResponse.Ver.Value} not supported. Only version {usernamePasswordRequest.Ver} is supported.");
}
if (!userNamePasswordResponse.Status.IsSuccess()) // Tor authentication is different, this will never happen;
{
// https://tools.ietf.org/html/rfc1929#section-2
// A STATUS field of X'00' indicates success. If the server returns a
// `failure' (STATUS value other than X'00') status, it MUST close the
// connection.
DisposeTcpClient();
throw new InvalidOperationException("Wrong username and/or password.");
}
}
Logger.LogDebug("<");
}
/// <summary>
/// IsolateSOCKSAuth must be on (on by default)
/// https://www.torproject.org/docs/tor-manual.html.en
/// https://gitweb.torproject.org/torspec.git/tree/socks-extensions.txt#n35
/// </summary>
/// <param name="identity">Isolates streams by identity. If identity is empty string, it won't isolate stream.</param>
internal async Task HandshakeAsync(string identity)
{
if (TorSocks5EndPoint is null)
{
return;
}
Guard.NotNull(nameof(identity), identity);
MethodsField methods = string.IsNullOrWhiteSpace(identity)
? new MethodsField(MethodField.NoAuthenticationRequired)
: new MethodsField(MethodField.UsernamePassword);
var sendBuffer = new VersionMethodRequest(methods).ToBytes();
var receiveBuffer = await SendAsync(sendBuffer, 2).ConfigureAwait(false);
var methodSelection = new MethodSelectionResponse();
methodSelection.FromBytes(receiveBuffer);
if (methodSelection.Ver != VerField.Socks5)
{
throw new NotSupportedException($"SOCKS{methodSelection.Ver.Value} not supported. Only SOCKS5 is supported.");
}
if (methodSelection.Method == MethodField.NoAcceptableMethods)
{
// https://www.ietf.org/rfc/rfc1928.txt
// If the selected METHOD is X'FF', none of the methods listed by the
// client are acceptable, and the client MUST close the connection.
DisposeTcpClient();
throw new NotSupportedException("Tor's SOCKS5 proxy does not support any of the client's authentication methods.");
}
if (methodSelection.Method == MethodField.UsernamePassword)
{
// https://tools.ietf.org/html/rfc1929#section-2
// Once the SOCKS V5 server has started, and the client has selected the
// Username / Password Authentication protocol, the Username / Password
// subnegotiation begins. This begins with the client producing a
// Username / Password request:
var username = identity;
var password = identity;
var uName = new UNameField(username);
var passwd = new PasswdField(password);
var usernamePasswordRequest = new UsernamePasswordRequest(uName, passwd);
sendBuffer = usernamePasswordRequest.ToBytes();
Array.Clear(receiveBuffer, 0, receiveBuffer.Length);
receiveBuffer = await SendAsync(sendBuffer, 2).ConfigureAwait(false);
var userNamePasswordResponse = new UsernamePasswordResponse();
userNamePasswordResponse.FromBytes(receiveBuffer);
if (userNamePasswordResponse.Ver != usernamePasswordRequest.Ver)
{
throw new NotSupportedException($"Authentication version {userNamePasswordResponse.Ver.Value} not supported. Only version {usernamePasswordRequest.Ver} is supported.");
}
if (!userNamePasswordResponse.Status.IsSuccess()) // Tor authentication is different, this will never happen;
{
// https://tools.ietf.org/html/rfc1929#section-2
// A STATUS field of X'00' indicates success. If the server returns a
// `failure' (STATUS value other than X'00') status, it MUST close the
// connection.
DisposeTcpClient();
throw new InvalidOperationException("Wrong username and/or password.");
}
}
}
