Test for ECDSA support explicitly.

The previous implementation could possibly fail for reasons unrelated to
ECDSA support.

1 files changed, 11 insertions, 15 deletions

diff --git a/Duplicati/Library/Backend/SSHv2/SSHv2Backend.cs b/Duplicati/Library/Backend/SSHv2/SSHv2Backend.cs
index 2d0d1fa02..b19ac7fc4 100644
--- a/Duplicati/Library/Backend/SSHv2/SSHv2Backend.cs
+++ b/Duplicati/Library/Backend/SSHv2/SSHv2Backend.cs
@@ -28,6 +28,7 @@ using System;
 using System.Collections.Generic;

 using System.Globalization;

 using System.Linq;

+using System.Security.Cryptography;

 using System.Threading;

 using System.Threading.Tasks;

 

@@ -335,35 +336,30 @@ namespace Duplicati.Library.Backend
 

         private void TryConnect(SftpClient client)

         {

-            try

-            {

-                client.Connect();

-            }

-            catch (NotImplementedException)

+            if (Utility.Utility.IsMono)

             {

                 // SSH.NET relies on the System.Security.Cryptography.ECDsaCng class for

                 // ECDSA algorithms, which is not implemented in Mono (as of 6.12.0.144).

                 // This prevents clients from connecting if one of the ECDSA algorithms is

-                // chosen as the host key algorithm.  In the event that this causes a

-                // connection failure, we will prevent the client from advertising support

-                // for ECDSA algorithms and make another connection attempt.

+                // chosen as the host key algorithm.  In this case, we will prevent the

+                // client from advertising support for ECDSA algorithms.

                 //

                 // See https://github.com/mono/mono/blob/mono-6.12.0.144/mcs/class/referencesource/System.Core/System/Security/Cryptography/ECDsaCng.cs

-                if (Utility.Utility.IsMono)

+                try

+                {

+                    ECDsa.Create(default(ECCurve));

+                }

+                catch (NotImplementedException)

                 {

                     List<string> ecdsaKeys = client.ConnectionInfo.HostKeyAlgorithms.Keys.Where(x => x.StartsWith("ecdsa")).ToList();

                     foreach (string key in ecdsaKeys)

                     {

                         client.ConnectionInfo.HostKeyAlgorithms.Remove(key);

                     }

-

-                    client.Connect();

-                }

-                else

-                {

-                    throw;

                 }

             }

+

+            client.Connect();

         }

 

         private void ChangeDirectory(string path)