Support SHA256 fingerprints for host key validation (#1098)

* Add tests for HostKeyEventArgs

* Add SHA256 fingerprint support

Author: DavisNT

README.md

@@ -143,30 +143,13 @@ using (var client = new SftpClient(connectionInfo))
 Establish a SSH connection using user name and password, and reject the connection if the fingerprint of the server does not match the expected fingerprint:
 
 ```cs
-byte[] expectedFingerPrint = new byte[] {
-                                            0x66, 0x31, 0xaf, 0x00, 0x54, 0xb9, 0x87, 0x31,
-                                            0xff, 0x58, 0x1c, 0x31, 0xb1, 0xa2, 0x4c, 0x6b
-                                        };
+string expectedFingerPrint = "LKOy5LvmtEe17S4lyxVXqvs7uPMy+yF79MQpHeCs/Qo";
 
 using (var client = new SshClient("sftp.foo.com", "guest", "pwd"))
 {
     client.HostKeyReceived += (sender, e) =>
         {
-            if (expectedFingerPrint.Length == e.FingerPrint.Length)
-            {
-                for (var i = 0; i < expectedFingerPrint.Length; i++)
-                {
-                    if (expectedFingerPrint[i] != e.FingerPrint[i])
-                    {
-                        e.CanTrust = false;
-                        break;
-                    }
-                }
-            }
-            else
-            {
-                e.CanTrust = false;
-            }
+            e.CanTrust = expectedFingerPrint.Equals(e.FingerPrintSHA256);
         };
     client.Connect();
 }

src/Renci.SshNet.Tests/Classes/Common/HostKeyEventArgsTest.cs

@@ -2,6 +2,8 @@
 using Renci.SshNet.Common;
 using Renci.SshNet.Security;
 using Renci.SshNet.Tests.Common;
+using System.Linq;
+using System.Reflection;
 
 namespace Renci.SshNet.Tests.Classes.Common
 {
@@ -10,7 +12,6 @@ namespace Renci.SshNet.Tests.Classes.Common
     ///to contain all HostKeyEventArgsTest Unit Tests
     ///</summary>
     [TestClass]
-    [Ignore] // placeholder for actual test
     public class HostKeyEventArgsTest : TestBase
     {
         /// <summary>
@@ -19,9 +20,52 @@ public class HostKeyEventArgsTest : TestBase
         [TestMethod]
         public void HostKeyEventArgsConstructorTest()
         {
-            KeyHostAlgorithm host = null; // TODO: Initialize to an appropriate value
-            HostKeyEventArgs target = new HostKeyEventArgs(host);
-            Assert.Inconclusive("TODO: Implement code to verify target");
+            HostKeyEventArgs target = new HostKeyEventArgs(GetKeyHostAlgorithm());
+            Assert.IsTrue(target.CanTrust);
+            Assert.IsTrue(new byte[] {
+                0x00, 0x00, 0x00, 0x07, 0x73, 0x73, 0x68, 0x2d, 0x72, 0x73, 0x61, 0x00, 0x00, 0x00, 0x01, 0x23,
+                0x00, 0x00, 0x01, 0x01, 0x00, 0xb9, 0x3b, 0x57, 0x9f, 0xe0, 0x5a, 0xb5, 0x7d, 0x68, 0x26, 0xeb,
+                0xe1, 0xa9, 0xf2, 0x59, 0xc3, 0x98, 0xdc, 0xfe, 0x97, 0x08, 0xc4, 0x95, 0x0f, 0x9a, 0xea, 0x05,
+                0x08, 0x7d, 0xfe, 0x6d, 0x77, 0xca, 0x04, 0x9f, 0xfd, 0xe2, 0x2c, 0x4d, 0x11, 0x3c, 0xd9, 0x05,
+                0xab, 0x32, 0xbd, 0x3f, 0xe8, 0xcd, 0xba, 0x00, 0x6c, 0x21, 0xb7, 0xa9, 0xc2, 0x4e, 0x63, 0x17,
+                0xf6, 0x04, 0x47, 0x93, 0x00, 0x85, 0xde, 0xd6, 0x32, 0xc0, 0xa1, 0x37, 0x75, 0x18, 0xa0, 0xb0,
+                0x32, 0xf6, 0x4e, 0xca, 0x39, 0xec, 0x3c, 0xdf, 0x79, 0xfe, 0x50, 0xa1, 0xc1, 0xf7, 0x67, 0x05,
+                0xb3, 0x33, 0xa5, 0x96, 0x13, 0x19, 0xfa, 0x14, 0xca, 0x55, 0xe6, 0x7b, 0xf9, 0xb3, 0x8e, 0x32,
+                0xee, 0xfc, 0x9d, 0x2a, 0x5e, 0x04, 0x79, 0x97, 0x29, 0x3d, 0x1c, 0x54, 0xfe, 0xc7, 0x96, 0x04,
+                0xb5, 0x19, 0x7c, 0x55, 0x21, 0xe2, 0x0e, 0x42, 0xca, 0x4d, 0x9d, 0xfb, 0x77, 0x08, 0x6c, 0xaa,
+                0x07, 0x2c, 0xf8, 0xf9, 0x1f, 0xbd, 0x83, 0x14, 0x2b, 0xe0, 0xbc, 0x7a, 0xf9, 0xdf, 0x13, 0x4b,
+                0x60, 0x5a, 0x02, 0x99, 0x93, 0x41, 0x1a, 0xb6, 0x5f, 0x3b, 0x9c, 0xb5, 0xb2, 0x55, 0x70, 0x78,
+                0x2f, 0x38, 0x52, 0x0e, 0xd1, 0x8a, 0x2c, 0x23, 0xc0, 0x3a, 0x0a, 0xd7, 0xed, 0xf6, 0x1f, 0xa6,
+                0x50, 0xf0, 0x27, 0x65, 0x8a, 0xd4, 0xde, 0xa7, 0x1b, 0x41, 0x67, 0xc5, 0x6d, 0x47, 0x84, 0x37,
+                0x92, 0x2b, 0xb7, 0xb6, 0x4d, 0xb0, 0x1a, 0xda, 0xf6, 0x50, 0x82, 0xf1, 0x57, 0x31, 0x69, 0xce,
+                0xe0, 0xef, 0xcd, 0x64, 0xaa, 0x78, 0x08, 0xea, 0x4e, 0x45, 0xec, 0xa5, 0x89, 0x68, 0x5d, 0xb4,
+                0xa0, 0x23, 0xaf, 0xff, 0x9c, 0x0f, 0x8c, 0x83, 0x7c, 0xf8, 0xe1, 0x8e, 0x32, 0x8e, 0x61, 0xfc,
+                0x5b, 0xbd, 0xd4, 0x46, 0xe1
+            }.SequenceEqual(target.HostKey));
+            Assert.AreEqual("ssh-rsa", target.HostKeyName);
+            Assert.AreEqual(2048, target.KeyLength);
+        }
+
+        /// <summary>
+        ///A test for MD5 calculation in HostKeyEventArgs Constructor
+        ///</summary>
+        [TestMethod]
+        public void HostKeyEventArgsConstructorTest_VerifyMD5()
+        {
+            HostKeyEventArgs target = new HostKeyEventArgs(GetKeyHostAlgorithm());
+            Assert.IsTrue(new byte[] {
+                0x92, 0xea, 0x54, 0xa1, 0x01, 0xf9, 0x95, 0x9c, 0x71, 0xd9, 0xbb, 0x51, 0xb2, 0x55, 0xf8, 0xd9
+            }.SequenceEqual(target.FingerPrint));
+        }
+
+        /// <summary>
+        ///A test for SHA256 calculation in HostKeyEventArgs Constructor
+        ///</summary>
+        [TestMethod]
+        public void HostKeyEventArgsConstructorTest_VerifySHA256()
+        {
+            HostKeyEventArgs target = new HostKeyEventArgs(GetKeyHostAlgorithm());
+            Assert.AreEqual("93LkmoWksp9ytNVZIPXi9KJU1uvlC9clZ/CkUHf6uEE", target.FingerPrintSHA256);
         }
 
         /// <summary>
@@ -30,14 +74,24 @@ public void HostKeyEventArgsConstructorTest()
         [TestMethod]
         public void CanTrustTest()
         {
-            KeyHostAlgorithm host = null; // TODO: Initialize to an appropriate value
-            HostKeyEventArgs target = new HostKeyEventArgs(host); // TODO: Initialize to an appropriate value
-            bool expected = false; // TODO: Initialize to an appropriate value
+            HostKeyEventArgs target = new HostKeyEventArgs(GetKeyHostAlgorithm());
+            bool expected = false;
             bool actual;
             target.CanTrust = expected;
             actual = target.CanTrust;
             Assert.AreEqual(expected, actual);
-            Assert.Inconclusive("Verify the correctness of this test method.");
         }
+
+        private static KeyHostAlgorithm GetKeyHostAlgorithm()
+        {
+            var executingAssembly = Assembly.GetExecutingAssembly();
+
+            using (var s = executingAssembly.GetManifestResourceStream(string.Format("Renci.SshNet.Tests.Data.{0}", "Key.RSA.txt")))
+            {
+                var privateKey = new PrivateKeyFile(s);
+                return (KeyHostAlgorithm)privateKey.HostKey;
+            }
+        }
+
     }
 }

src/Renci.SshNet/Common/HostKeyEventArgs.cs

@@ -28,10 +28,21 @@ public class HostKeyEventArgs : EventArgs
         public string HostKeyName{ get; private set; }
 
         /// <summary>
-        /// Gets the finger print.
+        /// Gets the MD5 fingerprint.
         /// </summary>
+        /// <value>
+        /// MD5 fingerprint as byte array.
+        /// </value>
         public byte[] FingerPrint { get; private set; }
 
+        /// <summary>
+        /// Gets the SHA256 fingerprint.
+        /// </summary>
+        /// <value>
+        /// Base64 encoded SHA256 fingerprint with padding (equals sign) removed.
+        /// </value>
+        public string FingerPrintSHA256 { get; private set; }
+
         /// <summary>
         /// Gets the length of the key in bits.
         /// </summary>
@@ -55,6 +66,11 @@ public HostKeyEventArgs(KeyHostAlgorithm host)
             {
                 FingerPrint = md5.ComputeHash(host.Data);
             }
+
+            using (var sha256 = CryptoAbstraction.CreateSHA256())
+            {
+                FingerPrintSHA256 = Convert.ToBase64String(sha256.ComputeHash(host.Data)).Replace("=", "");
+            }
         }
     }
 }