An established connection was aborted by the server

[rr-]

I can't connect to my server using WinSSHFS, but I can connect just fine with normal (cygwin) SSH using the same address and credentials.

This isn't firewall's fault - when I disable it temporarily, the error's all the same.

Stack trace:

Renci.SshNet.dll!Renci.SshNet.Session.SocketRead(int length, ref byte[] buffer) Line 140
Renci.SshNet.dll!Renci.SshNet.Session.Read(int length) Line 1560
Renci.SshNet.dll!Renci.SshNet.Session.ReceiveMessage() Line 895
Renci.SshNet.dll!Renci.SshNet.Session.MessageListener() Line 1666
Renci.SshNet.dll!Renci.SshNet.Session.Connect.AnonymousMethod__145_0() Line 561
Renci.SshNet.dll!Renci.SshNet.Session.ExecuteThread.AnonymousMethod__0(object o) Line 21
[External Code] 

Server software is SSH-2.0-OpenSSH_7.2

[rr-]

Seems I got the culprit - OpenSSH reports there's an error in the key exchange parameters:

mm_answer_moduli: bad parameters: 2048 2048 1024

[rr-]

The following change fixes the issue for me:

diff --git a/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha1.cs b/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha1.cs
index 2e91396..cb330b9 100644
--- a/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha1.cs
+++ b/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha1.cs
@@ -34,8 +34,8 @@ namespace Renci.SshNet.Security
                 ServerPayload = this._serverPayload,
                 HostKey = this._hostKey,
                 MinimumGroupSize = 1024,
-                PreferredGroupSize = 1024,
-                MaximumGroupSize = 1024,
+                PreferredGroupSize = 2048,
+                MaximumGroupSize = 2048,
                 Prime = this._prime,
                 SubGroup = this._group,
                 ClientExchangeValue = this._clientExchangeValue,
@@ -61,7 +61,7 @@ namespace Renci.SshNet.Security
             this.Session.MessageReceived += Session_MessageReceived;

             //  1. send SSH_MSG_KEY_DH_GEX_REQUEST
-            this.SendMessage(new KeyExchangeDhGroupExchangeRequest(1024, 1024, 1024));
+            this.SendMessage(new KeyExchangeDhGroupExchangeRequest(1024, 2048, 2048));
         }

         /// <summary>
diff --git a/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha256.cs b/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha256.cs
index 5cc9c23..c48def9 100644
--- a/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha256.cs
+++ b/Renci.SshNet/Security/KeyExchangeDiffieHellmanGroupExchangeSha256.cs
@@ -34,7 +34,7 @@ namespace Renci.SshNet.Security
             this.Session.MessageReceived += Session_MessageReceived;

             //  1. send SSH_MSG_KEY_DH_GEX_REQUEST
-            this.SendMessage(new KeyExchangeDhGroupExchangeRequest(1024,1024,1024));
+            this.SendMessage(new KeyExchangeDhGroupExchangeRequest(1024,2048,2048));

         }

@@ -64,8 +64,8 @@ namespace Renci.SshNet.Security
                 ServerPayload = this._serverPayload,
                 HostKey = this._hostKey,
                 MinimumGroupSize = 1024,
-                PreferredGroupSize = 1024,
-                MaximumGroupSize = 1024,
+                PreferredGroupSize = 2048,
+                MaximumGroupSize = 2048,
                 Prime = this._prime,
                 SubGroup = this._group,
                 ClientExchangeValue = this._clientExchangeValue,

[misuzu]

Same issue with OpenSSH 7.2.

[SzieberthAdam]

https://stribika.github.io/2015/01/04/secure-secure-shell.html

diffie-hellman-group1-sha1: 1024 bit DH with SHA1 diffie-hellman-group14-sha1: 2048 bit DH with SHA1 diffie-hellman-group-exchange-sha1: Custom DH with SHA1 diffie-hellman-group-exchange-sha256: Custom DH with SHA2

For the first glance it seems to me that KeyExchangeDiffieHellmanGroupExchangeSha1.cs and KeyExchangeDiffieHellmanGroupExchangeSha256.cs should support custom DH key size as agruments instead of hardcoded constants.

[KrullBorg]

duplicate of #75

[rr-]

Well on the bright side, we came up with a fix (see linked PR and article above)

[gschnitzler]

Patch works for me with OpenSSH_7.2p2 and dokan 1.0 Attached is a build from the latest devel branch.

sshfs.zip

[tmairegasnighto]

Same issue exists with RC2 (1.6.0.9), although @gerulf-profitsee's version above works without any other adjustment, although it labels itself 1.6.0.7.