How to Handle Java SFTP's UnknownHostKeyException?

Error Handling for Java SFTP UnknownHostKeyException

When utilizing Java SFTP with the JSch library, you may encounter the UnknownHostKey exception. This error occurs due to mismatched host key information. The resolution involves either skipping host key checking or setting up an expected host key for verification.

Skipping Host Key Checking (Not Recommended)

Avoid disabling host key checking by setting "StrictHostKeyChecking" to "no" before connecting to the session. This approach compromises security and should only be used for trusted connections.

Setting Up Expected Host Key

To ensure secure connections, it's essential to verify the host key against an expected value. There are two methods to achieve this:

1. Known Hosts File:

   a. Generate a "known_hosts-like" file using the "ssh-keyscan" command (e.g., ssh-keyscan example.com > known_hosts).
   b. Set JSch to use the known hosts file: JSch.setKnownHosts("/path/to/known_hosts-like").

2. Hard-coded Host Key:

   a. Obtain the expected host key in a format compatible with JSch.getHostKeyRepository().add().
   b. Add the host key to the repository: JSch.getHostKeyRepository().add(host, expectedHostKey).

By setting up a known or hard-coded host key, JSch will validate against the expected value and establish a secure connection.

The above is the detailed content of How to Handle Java SFTP's UnknownHostKeyException?. For more information, please follow other related articles on the PHP Chinese website!