Software & AppsOperating SystemLinux

How To Set Up SFTP File Access Logging for OpenSSH

Ubuntu 16

In this article, we will walk you through the process of setting up SFTP file access logging for OpenSSH. OpenSSH is a widely used software suite that provides secure remote access using the SSH protocol. SFTP (SSH File Transfer Protocol) is a secure file transfer protocol that provides file access, file transfer, and file management functionalities over SSH.

Quick Answer

To set up SFTP file access logging for OpenSSH, you need to modify the SSHD configuration file by adding the -f and -l options to the Subsystem sftp line. This enables logging to a specified syslog facility with a specified log level. After making the changes, you need to restart the SSH service for the changes to take effect. Finally, you can verify the logging by checking the log file for SFTP-related entries.

Why is SFTP Logging Important?

SFTP logging is crucial for monitoring and auditing your server’s SFTP activities. It helps you track user activities, troubleshoot issues, and detect anomalies or suspicious activities. Without logging, it would be difficult to understand what’s happening on your server.

Pre-requisites

Before we begin, make sure you have:

  • Root or sudo access to your server
  • OpenSSH installed and running on your server

Step 1: Modify the SSHD Configuration File

OpenSSH’s configuration is stored in the /etc/ssh/sshd_config file. You need to modify this file to enable SFTP logging.

Open the file using a text editor like nano or vi. For example:

sudo nano /etc/ssh/sshd_config

Locate the line that starts with Subsystem sftp. This line defines the command that is executed when an SFTP session is initiated. The default command is internal-sftp, which means OpenSSH uses its built-in SFTP server.

To enable logging, you need to add the -f and -l options to this command. The -f option specifies the syslog facility that will be used for logging, and the -l option specifies the log level.

For example, to log SFTP activities to the auth.log file with the INFO log level, modify the line as follows:

Subsystem sftp internal-sftp -f AUTH -l INFO

If you want to use the default system log and log level, you can omit the -f and -l options:

Subsystem sftp internal-sftp

Step 2: Restart the SSH Service

After modifying the sshd_config file, you need to restart the SSH service for the changes to take effect. The command to restart the service may vary depending on your operating system.

On Ubuntu, you can use the following command:

sudo service ssh restart

Or:

sudo systemctl restart ssh

Step 3: Verify the Logging

To verify that SFTP logging is working, you can check the log file for SFTP-related entries. The location of the log file depends on the syslog facility you specified in the sshd_config file. If you used the AUTH facility, the log file is typically /var/log/auth.log.

For example, to view the last 10 lines of the auth.log file, you can use the tail command:

sudo tail -n 10 /var/log/auth.log

You should see entries for SFTP sessions, including the username, IP address, and the files that were accessed.

Conclusion

Setting up SFTP file access logging for OpenSSH is a straightforward process that can provide valuable insights into your server’s SFTP activities. By following the steps outlined in this article, you can easily enable SFTP logging and start monitoring your server more effectively.

Remember, it’s important to regularly review your log files and consider using log management tools to analyze the logs and detect anomalies.

For more information on OpenSSH and SFTP, you can refer to the official OpenSSH documentation at https://www.openssh.com/.

What is SFTP?

SFTP stands for SSH File Transfer Protocol. It is a secure file transfer protocol that provides file access, file transfer, and file management functionalities over SSH.

Why is SFTP logging important?

SFTP logging is important for monitoring and auditing server’s SFTP activities. It helps track user activities, troubleshoot issues, and detect anomalies or suspicious activities.

What do I need to set up SFTP file access logging?

To set up SFTP file access logging, you need root or sudo access to your server and OpenSSH installed and running on your server.

How do I modify the SSHD configuration file?

You can modify the SSHD configuration file by opening the /etc/ssh/sshd_config file in a text editor like nano or vi.

How do I enable SFTP logging?

To enable SFTP logging, you need to add the -f and -l options to the Subsystem sftp line in the SSHD configuration file. The -f option specifies the syslog facility for logging, and the -l option specifies the log level.

How do I restart the SSH service?

After modifying the SSHD configuration file, you need to restart the SSH service for the changes to take effect. The command to restart the service may vary depending on your operating system. On Ubuntu, you can use the sudo service ssh restart or sudo systemctl restart ssh command.

How do I verify SFTP logging?

To verify SFTP logging, you can check the log file for SFTP-related entries. The location of the log file depends on the syslog facility specified in the SSHD configuration file. If the AUTH facility was used, the log file is typically /var/log/auth.log.

What information will be logged in the SFTP log file?

The SFTP log file will contain entries for SFTP sessions, including the username, IP address, and the files that were accessed.

Are there any additional steps I should take after enabling SFTP logging?

It is important to regularly review your log files and consider using log management tools to analyze the logs and detect anomalies.

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