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9.6. Prevent Include/Configuration File Access

When developing web based applications, do not allow users to access (read) files such as the program include and configuration files. This data may provide enough information (e.g., passwords) to break into the system. Note that this guideline sometimes also applies to other kinds of applications. There are several actions you can take to do this, including:

These approaches won't protect you from users who have access to the directories your files are in if they are world-readable. You could change the permissions of the files so that only the uid/gid of the webserver can read these files. However, this approach won't work if the user can get the web server to run his own scripts (the user can just write scripts to access your files). Fundamentally, if your site is being hosted on a server shared with untrusted people, it's harder to secure the system. One approach is to run multiple web serving programs, each with different permissions; this provides more security but is painful in practice. Another approach is to set these files to be read only by your uid/gid, and have the server run scripts at ``your'' permission. This latter approach has its own problems: it means that certain parts of the server must have root privileges, and that the script may have more permissions than necessary.