PR #971 with conflicts resolved and building

src/Renci.SshNet.Tests/Classes/BaseClientTest_Connect_OnConnectedThrowsException.cs

@@ -140,7 +140,7 @@ private static KeyHostAlgorithm GetKeyHostAlgorithm()
             using (var s = executingAssembly.GetManifestResourceStream(string.Format("Renci.SshNet.Tests.Data.{0}", "Key.RSA.txt")))
             {
                 var privateKey = new PrivateKeyFile(s);
-                return (KeyHostAlgorithm) privateKey.HostKey;
+                return privateKey.HostKeys[0];
             }
         }
 

src/Renci.SshNet.Tests/Classes/NetConfClientTest_Connect_NetConfSessionConnectFailure.cs

@@ -113,7 +113,7 @@ private static KeyHostAlgorithm GetKeyHostAlgorithm()
             using (var s = executingAssembly.GetManifestResourceStream(string.Format("Renci.SshNet.Tests.Data.{0}", "Key.RSA.txt")))
             {
                 var privateKey = new PrivateKeyFile(s);
-                return (KeyHostAlgorithm)privateKey.HostKey;
+                return privateKey.HostKeys[0];
             }
         }
     }

src/Renci.SshNet.Tests/Classes/PrivateKeyFileTest.cs

@@ -409,7 +409,7 @@ public void ConstructorWithStreamAndPassphrase()
             using (var stream = GetData("Key.RSA.Encrypted.Aes.128.CBC.12345.txt"))
             {
                 var privateKeyFile = new PrivateKeyFile(stream, "12345");
-                Assert.IsNotNull(privateKeyFile.HostKey);
+                Assert.IsNotNull(privateKeyFile.HostKeys[0]);
             }
         }
 
@@ -427,7 +427,7 @@ public void ConstructorWithFileNameAndPassphrase()
             using (var fs = File.Open(_temporaryFile, FileMode.Open, FileAccess.Read, FileShare.Read))
             {
                 var privateKeyFile = new PrivateKeyFile(_temporaryFile, "12345");
-                Assert.IsNotNull(privateKeyFile.HostKey);
+                Assert.IsNotNull(privateKeyFile.HostKeys[0]);
 
                 fs.Close();
             }
@@ -495,7 +495,7 @@ public void ConstructorWithFileName()
             }
 
             var privateKeyFile = new PrivateKeyFile(_temporaryFile, "12345");
-            Assert.IsNotNull(privateKeyFile.HostKey);
+            Assert.IsNotNull(privateKeyFile.HostKeys[0]);
         }
 
         /// <summary>
@@ -507,7 +507,7 @@ public void ConstructorWithStream()
             using (var stream = GetData("Key.RSA.txt"))
             {
                 var privateKeyFile = new PrivateKeyFile(stream);
-                Assert.IsNotNull(privateKeyFile.HostKey);
+                Assert.IsNotNull(privateKeyFile.HostKeys[0]);
             }
         }
 
@@ -523,7 +523,7 @@ public void ConstructorWithFileNameShouldBeAbleToReadFileThatIsSharedForReadAcce
             using (var fs = File.Open(_temporaryFile, FileMode.Open, FileAccess.Read, FileShare.Read))
             {
                 var privateKeyFile = new PrivateKeyFile(_temporaryFile);
-                Assert.IsNotNull(privateKeyFile.HostKey);
+                Assert.IsNotNull(privateKeyFile.HostKeys[0]);
 
                 fs.Close();
             }
@@ -541,7 +541,7 @@ public void ConstructorWithFileNameAndPassPhraseShouldBeAbleToReadFileThatIsShar
             using (var fs = File.Open(_temporaryFile, FileMode.Open, FileAccess.Read, FileShare.Read))
             {
                 var privateKeyFile = new PrivateKeyFile(_temporaryFile, "12345");
-                Assert.IsNotNull(privateKeyFile.HostKey);
+                Assert.IsNotNull(privateKeyFile.HostKeys[0]);
 
                 fs.Close();
             }

src/Renci.SshNet.Tests/Classes/SftpClientTest_Connect_SftpSessionConnectFailure.cs

@@ -122,7 +122,7 @@ private static KeyHostAlgorithm GetKeyHostAlgorithm()
             using (var s = executingAssembly.GetManifestResourceStream(string.Format("Renci.SshNet.Tests.Data.{0}", "Key.RSA.txt")))
             {
                 var privateKey = new PrivateKeyFile(s);
-                return (KeyHostAlgorithm)privateKey.HostKey;
+                return privateKey.HostKeys[0];
             }
         }
     }

src/Renci.SshNet/ConnectionInfo.cs

@@ -398,6 +398,7 @@ public ConnectionInfo(string host, int port, string username, ProxyTypes proxyTy
                     { "ecdsa-sha2-nistp521", data => new KeyHostAlgorithm("ecdsa-sha2-nistp521", new EcdsaKey(), data) },
                     { "ssh-rsa", data => new KeyHostAlgorithm("ssh-rsa", new RsaKey(), data) },
                     { "ssh-dss", data => new KeyHostAlgorithm("ssh-dss", new DsaKey(), data) },
+                    { "rsa-sha2-256", data => new KeyHostAlgorithm("rsa-sha2-256", new RsaWithSha256SignatureKey(), data) },
                 };
 
             CompressionAlgorithms = new Dictionary<string, Type>

src/Renci.SshNet/IPrivateKeySource.cs

@@ -10,6 +10,6 @@ public interface IPrivateKeySource
         /// <summary>
         /// Gets the host key.
         /// </summary>
-        HostAlgorithm HostKey { get; }
+        KeyHostAlgorithm[] HostKeys { get; }
     }
-}
+}

src/Renci.SshNet/PrivateKeyAuthenticationMethod.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using Renci.SshNet.Security;
 using System.Threading;
 
 using Renci.SshNet.Common;
@@ -64,24 +65,38 @@ public override AuthenticationResult Authenticate(Session session)
 
             session.RegisterMessage("SSH_MSG_USERAUTH_PK_OK");
 
+            var hostKeys = new HostAlgorithm[] { };
+
+            foreach (var keyFile in KeyFiles)
+            {
+                var idx = hostKeys.Length;
+
+                Array.Resize(ref hostKeys, idx + keyFile.HostKeys.Length);
+
+                for(var i = 0; i < keyFile.HostKeys.Length; i++)
+                {
+                    hostKeys[idx++] = keyFile.HostKeys[i];
+                }
+            }
+
             try
             {
-                foreach (var keyFile in KeyFiles)
+                foreach (var hostKey in hostKeys)
                 {
                     _ = _authenticationCompleted.Reset();
                     _isSignatureRequired = false;
 
                     var message = new RequestMessagePublicKey(ServiceName.Connection,
                                                               Username,
-                                                              keyFile.HostKey.Name,
-                                                              keyFile.HostKey.Data);
+                                                              hostKey.Name,
+                                                              hostKey.Data);
 
-                    if (KeyFiles.Count < 2)
+                    if (hostKeys.Length < 2)
                     {
                         // If only one key file provided then send signature for very first request
                         var signatureData = new SignatureData(message, session.SessionId).GetBytes();
 
-                        message.Signature = keyFile.HostKey.Sign(signatureData);
+                        message.Signature = hostKey.Sign(signatureData);
                     }
 
                     // Send public key authentication request
@@ -95,12 +110,12 @@ public override AuthenticationResult Authenticate(Session session)
 
                         var signatureMessage = new RequestMessagePublicKey(ServiceName.Connection,
                                                                            Username,
-                                                                           keyFile.HostKey.Name,
-                                                                           keyFile.HostKey.Data);
+                                                                           hostKey.Name,
+                                                                           hostKey.Data);
 
                         var signatureData = new SignatureData(message, session.SessionId).GetBytes();
 
-                        signatureMessage.Signature = keyFile.HostKey.Sign(signatureData);
+                        signatureMessage.Signature = hostKey.Sign(signatureData);
 
                         // Send public key authentication request with signature
                         session.SendMessage(signatureMessage);

src/Renci.SshNet/PrivateKeyFile.cs

@@ -74,15 +74,15 @@ public class PrivateKeyFile : IPrivateKeySource, IDisposable
         /// <summary>
         /// Gets the host key.
         /// </summary>
-        public HostAlgorithm HostKey { get; private set; }
+        public KeyHostAlgorithm[] HostKeys { get; private set; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PrivateKeyFile"/> class.
         /// </summary>
         /// <param name="key">The key.</param>
         public PrivateKeyFile(Key key)
         {
-            HostKey = new KeyHostAlgorithm(key.ToString(), key);
+            HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm(key.ToString(), key) };
         }
 
         /// <summary>
@@ -222,20 +222,22 @@ private void Open(Stream privateKey, string passPhrase)
             switch (keyName)
             {
                 case "RSA":
-                    _key = new RsaKey(decryptedData);
-                    HostKey = new KeyHostAlgorithm("ssh-rsa", _key);
+                    HostKeys = new KeyHostAlgorithm[] {
+                        new KeyHostAlgorithm("rsa-sha2-256", new RsaWithSha256SignatureKey(decryptedData)),
+                        new KeyHostAlgorithm("ssh-rsa", new RsaKey(decryptedData)),
+                    };
                     break;
                 case "DSA":
                     _key = new DsaKey(decryptedData);
-                    HostKey = new KeyHostAlgorithm("ssh-dss", _key);
+                    HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm("ssh-dss", _key) };
                     break;
                 case "EC":
                     _key = new EcdsaKey(decryptedData);
-                    HostKey = new KeyHostAlgorithm(_key.ToString(), _key);
+                    HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm(_key.ToString(), _key) };
                     break;
                 case "OPENSSH":
                     _key = ParseOpenSshV1Key(decryptedData, passPhrase);
-                    HostKey = new KeyHostAlgorithm(_key.ToString(), _key);
+                    HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm(_key.ToString(), _key) };
                     break;
                 case "SSH2 ENCRYPTED":
                     var reader = new SshDataReader(decryptedData);
@@ -291,7 +293,7 @@ private void Open(Stream privateKey, string passPhrase)
                         var q = reader.ReadBigIntWithBits(); // p
                         var p = reader.ReadBigIntWithBits(); // q
                         _key = new RsaKey(modulus, exponent, d, p, q, inverseQ);
-                        HostKey = new KeyHostAlgorithm("ssh-rsa", _key);
+                        HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm("ssh-rsa", _key) };
                     }
                     else if (keyType == "dl-modp{sign{dsa-nist-sha1},dh{plain}}")
                     {
@@ -306,7 +308,7 @@ private void Open(Stream privateKey, string passPhrase)
                         var y = reader.ReadBigIntWithBits();
                         var x = reader.ReadBigIntWithBits();
                         _key = new DsaKey(p, q, g, y, x);
-                        HostKey = new KeyHostAlgorithm("ssh-dss", _key);
+                        HostKeys = new KeyHostAlgorithm[] { new KeyHostAlgorithm("ssh-dss", _key) };
                     }
                     else
                     {

src/Renci.SshNet/Security/Cryptography/RsaSha256DigitalSignature.cs

@@ -0,0 +1,85 @@
+using System;
+using System.Security.Cryptography;
+using Renci.SshNet.Common;
+using Renci.SshNet.Security.Cryptography.Ciphers;
+
+namespace Renci.SshNet.Security.Cryptography
+{
+    /// <summary>
+    /// Implements RSA digital signature algorithm.
+    /// </summary>
+    public class RsaSha256DigitalSignature : CipherDigitalSignature, IDisposable
+    {
+        private HashAlgorithm _hash;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RsaSha256DigitalSignature"/> class.
+        /// </summary>
+        /// <param name="rsaKey">The RSA key.</param>
+        public RsaSha256DigitalSignature(RsaWithSha256SignatureKey rsaKey)
+            : base(new ObjectIdentifier(2, 16, 840, 1, 101, 3, 4, 2, 1), new RsaCipher(rsaKey))
+        {
+            _hash = SHA256.Create();
+        }
+
+        /// <summary>
+        /// Hashes the specified input.
+        /// </summary>
+        /// <param name="input">The input.</param>
+        /// <returns>
+        /// Hashed data.
+        /// </returns>
+        protected override byte[] Hash(byte[] input)
+        {
+            return _hash.ComputeHash(input);
+        }
+
+        #region IDisposable Members
+
+        private bool _isDisposed;
+
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases unmanaged and - optionally - managed resources
+        /// </summary>
+        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (_isDisposed)
+            {
+                return;
+            }    
+
+            if (disposing)
+            {
+                var hash = _hash;
+                if (hash != null)
+                {
+                    hash.Dispose();
+                    _hash = null;
+                }
+
+                _isDisposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Releases unmanaged resources and performs other cleanup operations before the
+        /// <see cref="RsaSha256DigitalSignature"/> is reclaimed by garbage collection.
+        /// </summary>
+        ~RsaSha256DigitalSignature()
+        {
+            Dispose(false);
+        }
+
+        #endregion
+    }
+}

src/Renci.SshNet/Security/Cryptography/RsaWithSha256SignatureKey.cs

@@ -0,0 +1,67 @@
+using System;
+using Renci.SshNet.Common;
+using Renci.SshNet.Security.Cryptography;
+
+namespace Renci.SshNet.Security
+{
+    /// <summary>
+    /// Contains RSA private and public key
+    /// </summary>
+    public class RsaWithSha256SignatureKey : RsaKey
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RsaWithSha256SignatureKey"/> class.
+        /// </summary>
+        public RsaWithSha256SignatureKey()
+        { }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RsaWithSha256SignatureKey"/> class.
+        /// </summary>
+        /// <param name="data">DER encoded private key data.</param>
+        public RsaWithSha256SignatureKey(byte[] data)
+            : base(data)
+        {
+            if (_privateKey.Length != 8)
+            {
+                throw new InvalidOperationException("Invalid private key.");
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RsaWithSha256SignatureKey"/> class.
+        /// </summary>
+        /// <param name="modulus">The modulus.</param>
+        /// <param name="exponent">The exponent.</param>
+        /// <param name="d">The d.</param>
+        /// <param name="p">The p.</param>
+        /// <param name="q">The q.</param>
+        /// <param name="inverseQ">The inverse Q.</param>
+        public RsaWithSha256SignatureKey(BigInteger modulus, BigInteger exponent, BigInteger d, BigInteger p, BigInteger q,
+            BigInteger inverseQ) : base(modulus, exponent, d, p, q, inverseQ)
+        {
+        }
+
+        private RsaSha256DigitalSignature _digitalSignature;
+
+        /// <summary>
+        /// Gets the digital signature.
+        /// </summary>
+        protected override DigitalSignature DigitalSignature
+        {
+            get
+            {
+                _digitalSignature ??= new RsaSha256DigitalSignature(this);
+                return _digitalSignature;
+            }
+        }
+
+        /// <summary>
+        /// Gets the Key String.
+        /// </summary>
+        public override string ToString()
+        {
+            return "rsa-sha2-256";
+        }
+    }
+}