Resolving paramiko.ssh_exception.ProxyCommandFailure

Pythoneo

Learn how to troubleshoot and resolve the paramiko.ssh_exception.ProxyCommandFailure error when using Paramiko for SSH connections through a proxy.

Understanding the Error

The paramiko.ssh_exception.ProxyCommandFailure error occurs when a ProxyCommand specified in your SSH configuration fails to execute or returns an error. ProxyCommand is commonly used to connect to a target server through an intermediate proxy server. Common reasons for this failure include:

  • Invalid ProxyCommand configuration.
  • Connectivity issues with the proxy server.
  • Incorrect paths or permissions for the ProxyCommand binary.
  • Unsupported or incorrectly configured proxy settings in your Paramiko client.
See also  How to Diagnose SSHException: Channel closed: Server-Side Issues and Network Interruptions in Paramiko

Steps to Resolve ProxyCommandFailure

Follow these steps to identify and fix the issue:

1. Verify Your ProxyCommand

Check the ProxyCommand syntax in your SSH configuration file (~/.ssh/config) or the command string passed to Paramiko. Ensure it uses the correct syntax:


ProxyCommand ssh -W %h:%p user@proxy-server

Replace user@proxy-server with the actual username and proxy server address.

See also  How to Handle SSHException in Multithreaded Applications: Thread Safety and Error Propagation in Paramiko

2. Test the ProxyCommand Manually

Run the ProxyCommand manually in your terminal to ensure it works:


ssh -W target-server:22 user@proxy-server

If this command fails, resolve the issues with your proxy server or credentials before proceeding.

3. Use Paramiko’s ProxyCommand Class

In Paramiko, you can set up the ProxyCommand explicitly using the paramiko.proxy.ProxyCommand class:


import paramiko
from paramiko.proxy import ProxyCommand

proxy_command = ProxyCommand("ssh -W %h:%p user@proxy-server")
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect("target-server", username="username", sock=proxy_command)

Replace user@proxy-server, target-server, and username with the appropriate values for your setup.

See also  How to transfer files and directories using paramiko

4. Debugging with Verbose Output

Enable verbose logging to capture detailed information about the connection process:


import logging

logging.basicConfig(level=logging.DEBUG)

Review the logs to identify any specific issues causing the ProxyCommandFailure.

5. Check File Paths and Permissions

Ensure the binary specified in the ProxyCommand (e.g., ssh) is in your system’s PATH and has the necessary execution permissions.