Introduce SSH functionality

Added SshAgentCredentials for querying ssh-agent, SshUserKeyCredentials
for authenticating with a given ssh key-pair.

Introduced UsernameQueryCredentials which returns the supported credential
types.

Authentication exceptions are now translated from libgit2.

8 files changed, 226 insertions, 1 deletions

diff --git a/LibGit2Sharp/AuthenticationException.cs b/LibGit2Sharp/AuthenticationException.cs
new file mode 100644
index 00000000..acbf331f
--- /dev/null
+++ b/LibGit2Sharp/AuthenticationException.cs
@@ -0,0 +1,55 @@
+using System;
+using System.Runtime.Serialization;
+using LibGit2Sharp.Core;
+
+namespace LibGit2Sharp
+{
+    /// <summary>
+    /// The exception that is thrown when an operation which requires an
+    /// authentication fails.
+    /// </summary>
+    [Serializable]
+    public class AuthenticationException : LibGit2SharpException
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LibGit2Sharp.AuthenticationException"/> class.
+        /// </summary>
+        public AuthenticationException()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LibGit2Sharp.AuthenticationException"/> class with a specified error message.
+        /// </summary>
+        /// <param name="message">A message that describes the error.</param>
+        public AuthenticationException(string message)
+            : base(message)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LibGit2Sharp.AuthenticationException"/> class with a specified error message and a reference to the inner exception that is the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception. If the <paramref name="innerException"/> parameter is not a null reference, the current exception is raised in a catch block that handles the inner exception.</param>
+        public AuthenticationException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LibGit2Sharp.AuthenticationException"/> class with a serialized data.
+        /// </summary>
+        /// <param name="info">The <see cref="SerializationInfo"/> that holds the serialized object data about the exception being thrown.</param>
+        /// <param name="context">The <see cref="StreamingContext"/> that contains contextual information about the source or destination.</param>
+        protected AuthenticationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+
+        internal AuthenticationException(string message, GitErrorCode code, GitErrorCategory category)
+            : base(message, code, category)
+        {
+        }
+    }
+}
diff --git a/LibGit2Sharp/Core/Ensure.cs b/LibGit2Sharp/Core/Ensure.cs
index 261794b0..c387a5af 100644
--- a/LibGit2Sharp/Core/Ensure.cs
+++ b/LibGit2Sharp/Core/Ensure.cs
@@ -127,7 +127,8 @@ namespace LibGit2Sharp.Core
                     { GitErrorCode.Conflict, (m, r, c) => new CheckoutConflictException(m, r, c) },
                     { GitErrorCode.LockedFile, (m, r, c) => new LockedFileException(m, r, c) },
                     { GitErrorCode.NotFound, (m, r, c) => new NotFoundException(m, r, c) },
-                    { GitErrorCode.Peel, (m, r, c) => new PeelException(m, r, c)  },
+                    { GitErrorCode.Peel, (m, r, c) => new PeelException(m, r, c) },
+                    { GitErrorCode.Auth, (m, r, c) => new AuthenticationException(m, r, c) },
                 };
 
         private static unsafe void HandleError(int result)
diff --git a/LibGit2Sharp/Core/NativeMethods.cs b/LibGit2Sharp/Core/NativeMethods.cs
index 5b62c086..674015b5 100644
--- a/LibGit2Sharp/Core/NativeMethods.cs
+++ b/LibGit2Sharp/Core/NativeMethods.cs
@@ -513,6 +513,24 @@ namespace LibGit2Sharp.Core
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string password);
 
         [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern int git_cred_ssh_key_new(
+            out IntPtr cred,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string username,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string publickey,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string privatekey,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string passphrase);
+
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern int git_cred_ssh_key_from_agent(
+            out IntPtr cred,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string username);
+
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern int git_cred_username_new(
+            out IntPtr cred,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string username);
+
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
         internal static extern void git_cred_free(IntPtr cred);
 
         [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
diff --git a/LibGit2Sharp/RemoteCallbacks.cs b/LibGit2Sharp/RemoteCallbacks.cs
index ce5dccf8..2cd8569d 100644
--- a/LibGit2Sharp/RemoteCallbacks.cs
+++ b/LibGit2Sharp/RemoteCallbacks.cs
@@ -284,6 +284,14 @@ namespace LibGit2Sharp
             {
                 types |= SupportedCredentialTypes.Default;
             }
+            if (credTypes.HasFlag(GitCredentialType.SshKey))
+            {
+                types |= SupportedCredentialTypes.Ssh;
+            }
+            if (credTypes.HasFlag(GitCredentialType.Username))
+            {
+                types |= SupportedCredentialTypes.UsernameQuery;
+            }
 
             ptr = IntPtr.Zero;
             try
diff --git a/LibGit2Sharp/SshAgentCredentials.cs b/LibGit2Sharp/SshAgentCredentials.cs
new file mode 100644
index 00000000..5812df2d
--- /dev/null
+++ b/LibGit2Sharp/SshAgentCredentials.cs
@@ -0,0 +1,36 @@
+using System;
+using LibGit2Sharp.Core;
+
+namespace LibGit2Sharp
+{
+    /// <summary>
+    /// Class that holds SSH agent credentials for remote repository access.
+    /// </summary>
+    public sealed class SshAgentCredentials : Credentials
+    {
+        /// <summary>
+        /// Callback to acquire a credential object.
+        /// </summary>
+        /// <param name="cred">The newly created credential object.</param>
+        /// <returns>0 for success, &lt; 0 to indicate an error, &gt; 0 to indicate no credential was acquired.</returns>
+        protected internal override int GitCredentialHandler(out IntPtr cred)
+        {
+            if (!GlobalSettings.Version.Features.HasFlag(BuiltInFeatures.Ssh))
+            {
+                throw new InvalidOperationException("LibGit2 was not built with SSH support.");
+            }
+
+            if (Username == null)
+            {
+                throw new InvalidOperationException("SshAgentCredentials contains a null Username.");
+            }
+
+            return NativeMethods.git_cred_ssh_key_from_agent(out cred, Username);
+        }
+
+        /// <summary>
+        /// Username for SSH authentication.
+        /// </summary>
+        public string Username { get; set; }
+    }
+}
diff --git a/LibGit2Sharp/SshUserKeyCredentials.cs b/LibGit2Sharp/SshUserKeyCredentials.cs
new file mode 100644
index 00000000..e5c9e470
--- /dev/null
+++ b/LibGit2Sharp/SshUserKeyCredentials.cs
@@ -0,0 +1,66 @@
+using System;
+using LibGit2Sharp.Core;
+
+namespace LibGit2Sharp
+{
+    /// <summary>
+    /// Class that holds SSH username with key credentials for remote repository access.
+    /// </summary>
+    public sealed class SshUserKeyCredentials : Credentials
+    {
+        /// <summary>
+        /// Callback to acquire a credential object.
+        /// </summary>
+        /// <param name="cred">The newly created credential object.</param>
+        /// <returns>0 for success, &lt; 0 to indicate an error, &gt; 0 to indicate no credential was acquired.</returns>
+        protected internal override int GitCredentialHandler(out IntPtr cred)
+        {
+            if (!GlobalSettings.Version.Features.HasFlag(BuiltInFeatures.Ssh))
+            {
+                throw new InvalidOperationException("LibGit2 was not built with SSH support.");
+            }
+
+            if (Username == null)
+            {
+                throw new InvalidOperationException("SshUserKeyCredentials contains a null Username.");
+            }
+
+            if (Passphrase == null)
+            {
+                throw new InvalidOperationException("SshUserKeyCredentials contains a null Passphrase.");
+            }
+
+            if (PublicKey == null)
+            {
+                throw new InvalidOperationException("SshUserKeyCredentials contains a null PublicKey.");
+            }
+
+            if (PrivateKey == null)
+            {
+                throw new InvalidOperationException("SshUserKeyCredentials contains a null PrivateKey.");
+            }
+
+            return NativeMethods.git_cred_ssh_key_new(out cred, Username, PublicKey, PrivateKey, Passphrase);
+        }
+
+        /// <summary>
+        /// Username for SSH authentication.
+        /// </summary>
+        public string Username { get; set; }
+
+        /// <summary>
+        /// Public key file location for SSH authentication.
+        /// </summary>
+        public string PublicKey { get; set; }
+
+        /// <summary>
+        /// Private key file location for SSH authentication.
+        /// </summary>
+        public string PrivateKey { get; set; }
+
+        /// <summary>
+        /// Passphrase for SSH authentication.
+        /// </summary>
+        public string Passphrase { get; set; }
+    }
+}
diff --git a/LibGit2Sharp/SupportedCredentialTypes.cs b/LibGit2Sharp/SupportedCredentialTypes.cs
index bc38a259..07759701 100644
--- a/LibGit2Sharp/SupportedCredentialTypes.cs
+++ b/LibGit2Sharp/SupportedCredentialTypes.cs
@@ -18,5 +18,15 @@ namespace LibGit2Sharp
         /// Ask Windows to provide its default credentials for the current user (e.g. NTLM)
         /// </summary>
         Default = (1 << 1),
+
+        /// <summary>
+        /// SSH with username and public/private keys. (SshUserKeyCredentials, SshAgentCredentials).
+        /// </summary>
+        Ssh = (1 << 2),
+
+        /// <summary>
+        /// Queries the server with the given username, then later returns the supported credential types.
+        /// </summary>
+        UsernameQuery = (1 << 3),
     }
 }
diff --git a/LibGit2Sharp/UsernameQueryCredentials.cs b/LibGit2Sharp/UsernameQueryCredentials.cs
new file mode 100644
index 00000000..14981d74
--- /dev/null
+++ b/LibGit2Sharp/UsernameQueryCredentials.cs
@@ -0,0 +1,31 @@
+using System;
+using LibGit2Sharp.Core;
+
+namespace LibGit2Sharp
+{
+    /// <summary>
+    /// Class that holds username query credentials for remote repository access.
+    /// </summary>
+    public sealed class UsernameQueryCredentials : Credentials
+    {
+        /// <summary>
+        /// Callback to acquire a credential object.
+        /// </summary>
+        /// <param name="cred">The newly created credential object.</param>
+        /// <returns>0 for success, &lt; 0 to indicate an error, &gt; 0 to indicate no credential was acquired.</returns>
+        protected internal override int GitCredentialHandler(out IntPtr cred)
+        {
+            if (Username == null)
+            {
+                throw new InvalidOperationException("UsernameQueryCredentials contains a null Username.");
+            }
+
+            return NativeMethods.git_cred_username_new(out cred, Username);
+        }
+
+        /// <summary>
+        /// Username for querying the server for supported authentication.
+        /// </summary>
+        public string Username { get; set; }
+    }
+}