SSH (Secure Shell)  aims to provide secure access to a server.

Though it works flawlessly, at times it may end up with an ssh error failed to negotiate authentication method.

A common reason for this error in FTP clients like FlashFXP is incorrect Login type settings.

While letting the customers focus on their business, we fix such server errors as a part of our Service Management Services.

Today, let’s analyze the SSH failed to negotiate authentication error and see how our Support Team fix it for our customers.

The SSH and SFTP Authentication

Let’s begin by checking more details on SSH and SFTP authentication.

Although SSH and SFTP have many similar functionalities, they are not the same. SSH allows a secure connection between a client and a host. It allows operating the host as well. SFTP is rather a file transfer protocol only. To make it work, use the need SSH access on the server.

Again, we need SSH user authentication for both SSH and SFTP communication. SSH supports various authentication method such as :
1. Password-Based – It requires Username and Password.
2. Key Based – It needs Username as well as an SSH key.
3. Two Factor – Username and both Password as well as SSH key required.
4. Host-Based – restricts client access to certain hosts.

How does SSH error failed to negotiate authentication method look?

Unfortunately, when the login method set up on the FTP or ssh client does not match with the one that on the server, it results in errors. As a result, we may see the SSH error failed to negotiate authentication method.

Cause and Fixes for SSH error failed to negotiate authentication

With more than a decade of experience in managing the servers, our Dedicated Engineers see such SFTP errors quite often. We’ll now discuss the cause and fixes for SSH error.

1. Unsupported Login Type

One of the common reasons for SSH failed to negotiate authentication method error is unsupported login type.

In such cases, SSH fails to authenticate. This error occurs if the client misses selecting a method. It may also occur If the host doesn’t support the selected method.

Solution: The exact fix for the error is to use the correct login method.

Let’s say the client is trying to connect with the password-based method, while the server supports the key-based method only. Therefore, to connect successfully, we need to change the setting in SSH client. For instance, in FTP clients like FlashFXP, our Support Engineers correct it using:

1. Open the Site Manager.
2. Select the desired site profile.
3. Change the Login type to “Key Based (Putty Agent)”
4. Click the Apply button to save your changes.

Using the wrong login method often causes a chance for a security breach in the server. Further, this leads to server compromise as well.

2. SFTP Configuration

Recently, one of our customers faced the issue with CuteFTP. Our team found that the Message Authentication Code (MAC) was enabled on the server. And it was not matching the MAC configuration settings of FTP client. Similarly, it may happen if the FTP Client does not support the MAC.

Solution: Our team configured the SSH setting in the FTP client and added the MAC. If the SFTP server is using an unsupported MAC, then we recommend contacting the administrator of the remote FTP server to allow the MAC. Some commonly supported MAC are SHA-1 (128), SHA-1-96, MD-5 and MD-5-96.

3. SSH error failed to negotiate authentication method – Wrong Public Key

If we are providing the wrong public key in Key Based method, then also it can cause ssh error failed to negotiate authentication method. In many cases, the system or FTP client might be using more than one public key.

Solution: Firstly, we look for the selected public key. Then we verify whether the key is correct or not. Finally, replacing the correct key fixes the error.

4. Insufficient Account Privileges

Moreover, insufficient account privileges also can be a reason for the error.

In the case of using FTP clients, we might face the same error message as mentioned above even after following the above three solutions. For instance, users may not have shell access especially for cPanel users in a Shared Hosting.

Solution: Here our Dedicated Engineers verify the type of access for the FTP user. We allow shell access to the account and that fixes the problem.

[Having trouble in fixing ssh errors? – We’ll fix it for you.]

Conclusion

In short, ssh error failed to negotiate authentication method happens due to unsupported login method, bad sftp settings, etc. Today, we saw how our Support Engineers fix errors related to SSH.