How To Prevent Log Injection

Preventing Log Injection

Preventing Log Injection

If you are not already familiar with the concept of Log Injection, please review the article entitled “What Is Log Injection ?“.

To learn more about how to detect Log Injection vulnerabilities, please see the article entitled “How To Test For Log Injection“.

They key to preventing Log Injection is two-fold:

  • Perform input validation: Limit the character set and format to be what your requirements dictate and reject any input that fails to meet your expectations.  Perform input validation on both the client and the server (as applicable).
  • Neutralize  Problematic characters: The following characters should be “escaped” or replaced when they appear within inputs that are written to log files/records:
\r Carriage Return
\n Newline
0x8 (octal 8) Backspace
< Less than
> Greater than
& Ampersand

Note that log files whose content will be rendered by a browser or presented as XML must also neutralize HTML meta-characters.  Standard HTML Entity encoding will suffice.

Log information that is stored in a database should be written in compliance with the guidelines presented in “How To Prevent SQL Injection“, which will protect against both SQL Injection and Log Forging.

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