Introduction
SSH (Secure Shell) is a popular network protocol used for secure remote access to servers and other network devices. When connecting to an SSH server for the first time, the client will check the host key of the server to verify its identity. This process is known as strict host key checking.
However, there may be situations where you want to disable strict host key checking, such as when connecting to a new server or when the server’s host key has changed. In this article, we will discuss how to disable strict host key checking in SSH.
Safety guidance: Disabling strict host key checking reduces SSH’s protection against connecting to an unexpected or malicious server. Use this setting only when you understand the risk, and preferably limit it to specific trusted hosts rather than applying it globally with
Host *.
Prerequisites
- Server credentials.
- SSH access to the system.
- Permission to modify the SSH client configuration.
Implementation
Step 1: Open the SSH Configuration File
Open your SSH configuration file, which is typically located at ~/.ssh/config. If the file does not exist, you can create it.
vi ~/.ssh/config
Step 2: Add the SSH Configuration
Add the following lines to the file:
Host * StrictHostKeyChecking no
This will apply the setting to all hosts you connect to. If you only want to apply it to specific hosts, replace the * with the hostname(s) you want to apply it.
For example:
Host example.com StrictHostKeyChecking no
Using a specific hostname is generally safer than applying the setting to all SSH connections.
Step 3: Save the File
Save the file and exit the editor.
You can then connect to the SSH server normally and verify that the configuration works as expected.
Conclusion
Disabling strict host key checking in SSH can be useful in certain situations, such as when connecting to a new server or when the server’s host key has changed. However, it also introduces security risks as it allows connections to untrusted hosts without proper authentication.
For better security, avoid disabling strict host key checking globally whenever possible and apply the setting only to the specific hosts that require it.
FAQs
What is SSH strict host key checking?
Strict host key checking is an SSH security feature that checks the server’s host key against known keys to help verify the server’s identity.
Where is the SSH client configuration file located?
The user-specific SSH client configuration file is typically located at:
~/.ssh/config
Does it StrictHostKeyChecking no apply to all servers?
Yes. When used with Host * the setting, it applies to all SSH hosts. To limit the setting, specify a particular hostname instead of *.
Is it safe to disable strict host key checking?
Disabling it can introduce security risks because SSH may connect without properly verifying the server’s identity. It should therefore be used carefully and only when necessary.
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- Use SSH Key Passphrase and SSH Forwarding: Learn about SSH key passphrases and SSH forwarding for secure SSH authentication.
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https://pheonixsolutions.com/blog/nikto-vulnerability-scan-domainsshell-script-scan-cpanel-accounts/
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