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scott-xuscott-xu
authoredJan 2, 2025··
Add support for sntrup761x25519Sha512 key exchange method (#1562)
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‎src/Renci.SshNet/ConnectionInfo.cs

+2
Original file line numberDiff line numberDiff line change
@@ -349,6 +349,8 @@ public ConnectionInfo(string host, int port, string username, ProxyTypes proxyTy
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KeyExchangeAlgorithms = new Dictionary<string, Func<IKeyExchange>>
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{
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{ "sntrup761x25519-sha512", () => new KeyExchangeSNtruP761X25519Sha512() },
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{ "sntrup761x25519-sha512@openssh.com", () => new KeyExchangeSNtruP761X25519Sha512() },
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{ "curve25519-sha256", () => new KeyExchangeECCurve25519() },
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{ "curve25519-sha256@libssh.org", () => new KeyExchangeECCurve25519() },
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{ "ecdh-sha2-nistp256", () => new KeyExchangeECDH256() },

‎src/Renci.SshNet/Security/KeyExchangeSNtruP761X25519Sha512.cs

+135
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,135 @@
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using System;
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using System.Globalization;
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using System.Linq;
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using Org.BouncyCastle.Crypto.Agreement;
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using Org.BouncyCastle.Crypto.Generators;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Pqc.Crypto.NtruPrime;
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using Renci.SshNet.Abstractions;
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using Renci.SshNet.Common;
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using Renci.SshNet.Messages.Transport;
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namespace Renci.SshNet.Security
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{
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internal sealed class KeyExchangeSNtruP761X25519Sha512 : KeyExchangeEC
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{
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private SNtruPrimeKemExtractor _sntrup761Extractor;
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private X25519Agreement _x25519Agreement;
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/// <summary>
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/// Gets algorithm name.
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/// </summary>
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public override string Name
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{
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get { return "sntrup761x25519-sha512"; }
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}
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/// <summary>
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/// Gets the size, in bits, of the computed hash code.
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/// </summary>
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/// <value>
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/// The size, in bits, of the computed hash code.
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/// </value>
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protected override int HashSize
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{
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get { return 512; }
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}
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/// <inheritdoc/>
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public override void Start(Session session, KeyExchangeInitMessage message, bool sendClientInitMessage)
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{
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base.Start(session, message, sendClientInitMessage);
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Session.RegisterMessage("SSH_MSG_KEX_ECDH_REPLY");
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Session.KeyExchangeEcdhReplyMessageReceived += Session_KeyExchangeEcdhReplyMessageReceived;
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var sntrup761KeyPairGenerator = new SNtruPrimeKeyPairGenerator();
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sntrup761KeyPairGenerator.Init(new SNtruPrimeKeyGenerationParameters(CryptoAbstraction.SecureRandom, SNtruPrimeParameters.sntrup761));
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var sntrup761KeyPair = sntrup761KeyPairGenerator.GenerateKeyPair();
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_sntrup761Extractor = new SNtruPrimeKemExtractor((SNtruPrimePrivateKeyParameters)sntrup761KeyPair.Private);
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var x25519KeyPairGenerator = new X25519KeyPairGenerator();
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x25519KeyPairGenerator.Init(new X25519KeyGenerationParameters(CryptoAbstraction.SecureRandom));
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var x25519KeyPair = x25519KeyPairGenerator.GenerateKeyPair();
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_x25519Agreement = new X25519Agreement();
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_x25519Agreement.Init(x25519KeyPair.Private);
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var sntrup761PublicKey = ((SNtruPrimePublicKeyParameters)sntrup761KeyPair.Public).GetEncoded();
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var x25519PublicKey = ((X25519PublicKeyParameters)x25519KeyPair.Public).GetEncoded();
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_clientExchangeValue = sntrup761PublicKey.Concat(x25519PublicKey);
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SendMessage(new KeyExchangeEcdhInitMessage(_clientExchangeValue));
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}
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/// <summary>
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/// Finishes key exchange algorithm.
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/// </summary>
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public override void Finish()
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{
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base.Finish();
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Session.KeyExchangeEcdhReplyMessageReceived -= Session_KeyExchangeEcdhReplyMessageReceived;
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}
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/// <summary>
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/// Hashes the specified data bytes.
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/// </summary>
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/// <param name="hashData">The hash data.</param>
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/// <returns>
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/// The hash of the data.
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/// </returns>
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protected override byte[] Hash(byte[] hashData)
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{
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return CryptoAbstraction.HashSHA512(hashData);
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}
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private void Session_KeyExchangeEcdhReplyMessageReceived(object sender, MessageEventArgs<KeyExchangeEcdhReplyMessage> e)
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{
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var message = e.Message;
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// Unregister message once received
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Session.UnRegisterMessage("SSH_MSG_KEX_ECDH_REPLY");
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HandleServerEcdhReply(message.KS, message.QS, message.Signature);
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// When SSH_MSG_KEX_ECDH_REPLY received key exchange is completed
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Finish();
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}
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/// <summary>
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/// Handles the server DH reply message.
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/// </summary>
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/// <param name="hostKey">The host key.</param>
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/// <param name="serverExchangeValue">The server exchange value.</param>
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/// <param name="signature">The signature.</param>
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private void HandleServerEcdhReply(byte[] hostKey, byte[] serverExchangeValue, byte[] signature)
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{
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_serverExchangeValue = serverExchangeValue;
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_hostKey = hostKey;
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_signature = signature;
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if (serverExchangeValue.Length != _sntrup761Extractor.EncapsulationLength + X25519PublicKeyParameters.KeySize)
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{
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throw new SshConnectionException(
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string.Format(CultureInfo.CurrentCulture, "Bad Q_S length: {0}.", serverExchangeValue.Length),
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DisconnectReason.KeyExchangeFailed);
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}
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var sntrup761CipherText = serverExchangeValue.Take(_sntrup761Extractor.EncapsulationLength);
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var secret = _sntrup761Extractor.ExtractSecret(sntrup761CipherText);
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var sntrup761SecretLength = secret.Length;
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var x25519PublicKey = new X25519PublicKeyParameters(serverExchangeValue, _sntrup761Extractor.EncapsulationLength);
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Array.Resize(ref secret, sntrup761SecretLength + _x25519Agreement.AgreementSize);
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_x25519Agreement.CalculateAgreement(x25519PublicKey, secret, sntrup761SecretLength);
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SharedKey = CryptoAbstraction.HashSHA512(secret);
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}
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}
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}

‎test/Renci.SshNet.IntegrationTests/KeyExchangeAlgorithmTests.cs

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Original file line numberDiff line numberDiff line change
@@ -22,6 +22,37 @@ public void TearDown()
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_remoteSshdConfig?.Reset();
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}
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[TestMethod]
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[Ignore]
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public void SNtruP761X25519Sha512()
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{
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_remoteSshdConfig.ClearKeyExchangeAlgorithms()
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.AddKeyExchangeAlgorithm(KeyExchangeAlgorithm.SNtruP761X25519Sha512)
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.Update()
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.Restart();
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using (var client = new SshClient(_connectionInfoFactory.Create()))
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{
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client.Connect();
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client.Disconnect();
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}
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}
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[TestMethod]
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public void SNtruP761X25519Sha512OpenSsh()
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{
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_remoteSshdConfig.ClearKeyExchangeAlgorithms()
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.AddKeyExchangeAlgorithm(KeyExchangeAlgorithm.SNtruP761X25519Sha512OpenSsh)
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.Update()
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.Restart();
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using (var client = new SshClient(_connectionInfoFactory.Create()))
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{
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client.Connect();
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client.Disconnect();
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}
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}
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[TestMethod]
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public void Curve25519Sha256()
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{

‎test/Renci.SshNet.TestTools.OpenSSH/KeyExchangeAlgorithm.cs

+2-1
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,8 @@ public sealed class KeyExchangeAlgorithm
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public static readonly KeyExchangeAlgorithm EcdhSha2Nistp521 = new KeyExchangeAlgorithm("ecdh-sha2-nistp521");
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public static readonly KeyExchangeAlgorithm Curve25519Sha256 = new KeyExchangeAlgorithm("curve25519-sha256");
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public static readonly KeyExchangeAlgorithm Curve25519Sha256Libssh = new KeyExchangeAlgorithm("curve25519-sha256@libssh.org");
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public static readonly KeyExchangeAlgorithm Sntrup4591761x25519Sha512 = new KeyExchangeAlgorithm("sntrup4591761x25519-sha512@tinyssh.org");
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public static readonly KeyExchangeAlgorithm SNtruP761X25519Sha512 = new KeyExchangeAlgorithm("sntrup761x25519-sha512");
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public static readonly KeyExchangeAlgorithm SNtruP761X25519Sha512OpenSsh = new KeyExchangeAlgorithm("sntrup761x25519-sha512@openssh.com");
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public KeyExchangeAlgorithm(string name)
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{

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