Resolving « End of Keyboard-Interactive Prompts from Server » Error in SSH Using PuTTY

Introduction

Encountering the « End of Keyboard-Interactive Prompts from Server » error message can be perplexing, but it’s solvable. This issue typically arises due to a misconfiguration or compatibility problem between the PuTTY client and the server. This guide will walk you through a series of steps to help resolve this problem and successfully establish an SSH connection.

Step 1: Update PuTTY

Start by ensuring you’re using the latest version of PuTTY. Updated versions often come with bug fixes and improved compatibility with different server configurations.

1. Visit the official PuTTY website and download the most recent version.
2. Install the updated version on your system.

Step 2: Review Server Configuration Files

There are specific server configuration files you can adjust to potentially resolve this issue.

1. Set KbdInteractiveAuthentication to True:
   • You can modify the sshd_config file to enable keyboard-interactive authentication.
   • Open the SSH configuration file at /etc/ssh/sshd_config:shCopy code
     sudo nano /etc/ssh/sshd_config
   • Find the line that says KbdInteractiveAuthentication and ensure it’s set to yes.
2. Check ChallengeResponseAuthentication:
   • This setting influences challenge-response based authentication methods, including keyboard-interactive.
   • In the same sshd_config file, verify the value of ChallengeResponseAuthentication. It should be set to yes for keyboard-interactive to work.
   • Save the file and restart the SSH service:shCopy code
     sudo service ssh restart

Step 3: Investigate Network Issues

Network problems can occasionally trigger this error. Here are steps to check and potentially rectify network-related issues:

1. Verify that your network connection is stable and not experiencing any interruptions.
2. Examine if any firewalls or security policies might be obstructing the connection. If so, configure them to allow SSH traffic.

Step 4: Verify SSH Key Pair

For users employing SSH keys for authentication, it is crucial to confirm that they are correctly configured on both the client and server side.

1. Confirm you are using the appropriate private key in PuTTY (the .ppk file).
2. Verify that the corresponding public key is added to the ~/.ssh/authorized_keys file on the server for the user you are attempting to connect as.

Step 5: Debugging with PuTTY

PuTTY provides various logging options that can aid in identifying the root cause of the issue. Follow these steps:

1. Launch PuTTY and navigate to the session configuration window.
2. In the left panel, select « Logging » under the « Session » category.
3. Opt for the desired logging options. For thorough debugging, « All session output » is recommended.

Conclusion

By diligently following these steps and considering the provided comments, you should be able to resolve the « End of Keyboard-Interactive Prompts from Server » error and successfully establish an SSH connection using PuTTY. Remember to review your configuration, update PuTTY, and confirm that password authentication is enabled if necessary. Should the issue persist, consider seeking assistance from your server administrator or hosting provider.