public SshClient(SshClientSettings settings, ILogger?logger = null)
{
ValidateSettings(settings);
_settings = settings ?? throw new ArgumentNullException(nameof(settings));
_logger = logger ?? NullLogger.Instance;
_abortCts = new CancellationTokenSource();
}
private static void ValidateSettings(SshClientSettings settings)
{
// TODO: extend this...
if (settings.Host == null)
{
throw new ArgumentNullException(nameof(settings.Host));
}
}
private static async Task PerformDefaultExchange(SshConnection connection, SshConnectionInfo connectionInfo, ILogger logger, SshClientSettings settings, CancellationToken ct)
{
// Protocol Version Exchange: https://tools.ietf.org/html/rfc4253#section-4.2.
// The maximum length of the string is 255 characters, including the Carriage Return and Line Feed.
const int MaxLineLength = 255 - 2;
// The server MAY send other lines of data before sending the version string.
const int MaxLineReads = 20;
AssemblyInformationalVersionAttribute?versionAttribute = typeof(SshClient).Assembly.GetCustomAttribute <AssemblyInformationalVersionAttribute>();
string version = versionAttribute?.InformationalVersion ?? "0.0";
version = version.Replace('-', '_');
string identificationString = $"SSH-2.0-TmdsSsh_{version}";
connectionInfo.ClientIdentificationString = identificationString;
// Send our identification string.
logger.LogInformation("Local version string {identificationString}", identificationString);
await connection.WriteLineAsync(identificationString, ct);
// Receive peer identification string.
for (int i = 0; i < MaxLineReads; i++)
{
string line = await connection.ReceiveLineAsync(MaxLineLength, ct);
if (line.StartsWith("SSH-", StringComparison.Ordinal))
{
connectionInfo.ServerIdentificationString = line;
if (line.StartsWith("SSH-2.0-", StringComparison.Ordinal))
{
logger.LogInformation("Remote version string {identificationString}", connectionInfo.ServerIdentificationString);
return;
}
ThrowHelper.ThrowProtocolUnsupportedVersion(line);
}
}
ThrowHelper.ThrowProtocolNoVersionIdentificationString();
}
private async static Task PerformDefaultAuthentication(SshConnection connection, ILogger logger, SshClientSettings settings, SshConnectionInfo connectionInfo, CancellationToken ct)
{
// TODO: handle SSH_MSG_USERAUTH_BANNER.
// Request ssh-userauth service
{
using var serviceRequestMsg = CreateServiceRequestMessage(connection.SequencePool);
await connection.SendPacketAsync(serviceRequestMsg, ct);
}
{
using Packet serviceAcceptMsg = await connection.ReceivePacketAsync(ct);
ParseServiceAccept(serviceAcceptMsg);
}
// Try credentials.
foreach (var credential in settings.Credentials)
{
if (credential is PasswordCredential passwordCredential)
{
logger.AuthenticationMethod("password");
using var userAuthMsg = CreatePasswordRequestMessage(connection.SequencePool,
settings.UserName !, passwordCredential.Password);
await connection.SendPacketAsync(userAuthMsg, ct);
}
else if (credential is IdentityFileCredential ifCredential)
{
if (IdentityFileCredential.TryParseFile(ifCredential.Filename, out PrivateKey? pk))
{
using (pk)
{
logger.AuthenticationMethodPublicKey(ifCredential.Filename);
using var userAuthMsg = CreatePublicKeyRequestMessage(connection.SequencePool,
settings.UserName !, connectionInfo.SessionId !, pk !);
await connection.SendPacketAsync(userAuthMsg, ct);
}
}
else
{
continue;
}
}
else
{
throw new NotImplementedException("Unsupported credential type: " + credential.GetType().FullName);
}
// TODO...
using Packet response = await connection.ReceivePacketAsync(ct);
if (IsAuthSuccesfull(response))
{
logger.AuthenticationSucceeded();
return;
}
}
throw new AuthenticationFailedException();
}
private async static Task PerformDefaultExchange(SshConnection connection, Packet clientKexInitMsg, Packet serverKexInitMsg, ILogger logger, SshClientSettings settings, SshConnectionInfo connectionInfo, CancellationToken ct)
{
// Key Exchange: https://tools.ietf.org/html/rfc4253#section-7.
SequencePool sequencePool = connection.SequencePool;
var remoteInit = ParseKeyExchangeInitMessage(serverKexInitMsg);
// The chosen algorithm MUST be the first algorithm on the client's name-list
// that is also on the server's name-list.
Name encC2S = ChooseAlgorithm(settings.EncryptionAlgorithmsClientToServer, remoteInit.encryption_algorithms_client_to_server);
Name encS2C = ChooseAlgorithm(settings.EncryptionAlgorithmsServerToClient, remoteInit.encryption_algorithms_server_to_client);
Name macC2S = ChooseAlgorithm(settings.MacAlgorithmsClientToServer, remoteInit.mac_algorithms_client_to_server);
Name macS2C = ChooseAlgorithm(settings.MacAlgorithmsServerToClient, remoteInit.mac_algorithms_server_to_client);
Name comC2S = ChooseAlgorithm(settings.CompressionAlgorithmsClientToServer, remoteInit.compression_algorithms_client_to_server);
Name comS2C = ChooseAlgorithm(settings.CompressionAlgorithmsServerToClient, remoteInit.compression_algorithms_server_to_client);
if (encC2S.IsEmpty || encS2C.IsEmpty || macC2S.IsEmpty || macS2C.IsEmpty || comC2S.IsEmpty || comS2C.IsEmpty)
{
ThrowHelper.ThrowKeyExchangeFailed("No common encryption/integrity/compression algorithm.");
}
// Make an ordered list of host key algorithms. The key exchange algorithm will pick a compatible one.
List <Name> hostKeyAlgorithms = new List <Name>(capacity: settings.ServerHostKeyAlgorithms.Count);
foreach (var hostKeyAlgorithm in settings.ServerHostKeyAlgorithms)
{
if (remoteInit.server_host_key_algorithms.Contains(hostKeyAlgorithm))
{
hostKeyAlgorithms.Add(hostKeyAlgorithm);
}
}
// The first algorithm MUST be the preferred (and guessed) algorithm. If
// both sides make the same guess, that algorithm MUST be used.
Name matchingKex = settings.KeyExchangeAlgorithms.Count == 0 ||
remoteInit.kex_algorithms.Length == 0 ||
settings.KeyExchangeAlgorithms[0] != remoteInit.kex_algorithms[0] ? default(Name) : settings.KeyExchangeAlgorithms[0];
KeyExchangeOutput?keyExchangeOutput = null;
Packet exchangeInitMsg = default;
try
{
if (remoteInit.first_kex_packet_follows)
{
exchangeInitMsg = await connection.ReceivePacketAsync(ct);
if (matchingKex.IsEmpty ||
settings.ServerHostKeyAlgorithms.Count == 0 ||
remoteInit.server_host_key_algorithms.Length == 0 ||
settings.ServerHostKeyAlgorithms[0] != remoteInit.server_host_key_algorithms[0])
{
// Silently ignore if guessed wrong.
exchangeInitMsg.Dispose();
exchangeInitMsg = default;
}
else
{
// Only accept the first hostKeyAlgorithm.
if (hostKeyAlgorithms.Count > 1)
{
hostKeyAlgorithms.RemoveRange(1, hostKeyAlgorithms.Count - 1);
}
}
}
EncryptionFactory.Default.GetKeyAndIVLength(encC2S, out int encryptionKeyC2SLength, out int initialIVC2SLength);
EncryptionFactory.Default.GetKeyAndIVLength(encS2C, out int encryptionKeyS2CLength, out int initialIVS2CLength);
int integrityKeyC2SLength = HMacFactory.Default.GetKeyLength(macC2S);
int integrityKeyS2CLength = HMacFactory.Default.GetKeyLength(macS2C);
var keyExchangeInput = new KeyExchangeInput(hostKeyAlgorithms, exchangeInitMsg, clientKexInitMsg, serverKexInitMsg, connectionInfo,
initialIVC2SLength, initialIVS2CLength, encryptionKeyC2SLength, encryptionKeyS2CLength, integrityKeyC2SLength, integrityKeyS2CLength);
foreach (var keyAlgorithm in settings.KeyExchangeAlgorithms)
{
if (remoteInit.kex_algorithms.Contains(keyAlgorithm))
{
logger.KeyExchangeAlgorithm(keyAlgorithm);
using (var algorithm = KeyExchangeAlgorithmFactory.Default.Create(keyAlgorithm))
{
keyExchangeOutput = await algorithm.TryExchangeAsync(connection, keyExchangeInput, logger, ct);
}
if (keyExchangeOutput != null)
{
connectionInfo.SessionId ??= keyExchangeOutput.ExchangeHash;
break;
}
// Preferred algorithm must be used.
if (!matchingKex.IsEmpty)
{
ThrowHelper.ThrowKeyExchangeFailed("Preferred key exchange algorithm failed.");
}
}
}
// If no algorithm satisfying all these conditions can be found, the
// connection fails, and both sides MUST disconnect.
if (keyExchangeOutput == null)
{
ThrowHelper.ThrowKeyExchangeFailed("Key exchange failed");
}
}
finally
{
exchangeInitMsg.Dispose();
}
logger.AlgorithmsServerToClient(encS2C, macS2C, comS2C);
logger.AlgorithmsClientToServer(encC2S, macC2S, comC2S);
// Send SSH_MSG_NEWKEYS.
{
using Packet newKeysMsg = CreateNewKeysMessage(sequencePool);
await connection.SendPacketAsync(newKeysMsg, ct);
}
// Receive SSH_MSG_NEWKEYS.
using Packet newKeysReceivedMsg = await connection.ReceivePacketAsync(ct);
ParseNewKeysMessage(newKeysReceivedMsg);
var encrypt = EncryptionFactory.Default.CreateEncryptor(encC2S, keyExchangeOutput.EncryptionKeyC2S, keyExchangeOutput.InitialIVC2S);
var macForEncoder = HMacFactory.Default.Create(macC2S, keyExchangeOutput.IntegrityKeyC2S);
var decrypt = EncryptionFactory.Default.CreateDecryptor(encS2C, keyExchangeOutput.EncryptionKeyS2C, keyExchangeOutput.InitialIVS2C);
var macForDecoder = HMacFactory.Default.Create(macS2C, keyExchangeOutput.IntegrityKeyS2C);
connection.SetEncoderDecoder(new PacketEncoder(encrypt, macForEncoder), new PacketDecoder(sequencePool, decrypt, macForDecoder));
internal static async Task <SshConnection> EstablishConnectionAsync(ILogger logger, SequencePool sequencePool, SshClientSettings settings, CancellationToken ct)
{
Socket?socket = null;
try
{
socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
// Connect to the remote host
logger.Connecting(settings.Host !, settings.Port);
await socket.ConnectAsync(settings.Host !, settings.Port, ct);
logger.ConnectionEstablished();
socket.NoDelay = true;
return(new SocketSshConnection(logger, sequencePool, socket));
}
catch
{
socket?.Dispose();
throw;
}
}
