Multiple security issues are taken into consideration when you are writing Berkeley DB applications. The following sections detail these security issues further.
Database Environment Permissions
To ensure that files in the environment are not accessible to unauthorized users, set permissions on the directory used as the Berkeley DB database environment. You must carefully check the applications that add to the user's permissions (for example,
setgid applications) to prevent illegal use of those permissions. An example of such a permission is general file access in the environment directory.
DB_USE_ENVIRON_ROOT flags and allowing the use of environment variables during file naming can be dangerous. Setting those flags in Berkeley DB applications with additional permissions (for example,
UNIX setuid or
setgid applications) could potentially allow users to read and write databases to which they would not normally have access.
By default, Berkeley DB always creates files that are readable and writable by the owner and the group (that is,
S_IWGRP; or octal mode 0660 on historic UNIX systems). The group ownership of created files is based on the system and directory defaults, and is not further specified by Berkeley DB.
When opening a database on a UNIX/Linux machine, you can specify the file permissions with the mode flag.
Temporary Backing Files
If an unnamed database is created and the cache is too small to hold the database in memory, Berkeley DB will create a temporary physical file to enable it to page the database to disk as needed. In this case, environment variables such as
TMPDIR may be used to specify the location of that temporary file. Although temporary backing files are created readable and writable by the owner only (
S_IWUSR, or octal mode 0600 on historic UNIX systems), some filesystems may not sufficiently protect temporary files created in random directories from improper access. To be absolutely safe, applications storing sensitive data in unnamed databases should use the
DB_ENV->set_tmp_dir() method to specify a temporary directory with known permissions.
The Berkeley DB Tcl API evaluates user input as Tcl commands. For this reason, it may be dangerous to pass unreviewed user input through the Berkeley DB Tcl API, as the input may subsequently be evaluated as a Tcl command. Additionally, the Berkeley DB Tcl API initialization routine resets effective user and group IDs to the real user and group IDs. This minimizes the effectiveness of a Tcl injection attack.
External files are not encrypted even when encryption has been specified at the environment or database level. The only way to protect the external files is by using the file system permission restrictions to the directory tree in which the external files are stored.
When using the environment flag
DB_PRIVATE, it is possible for old data in the heap to leak onto unused parts of the database page. You can avoid this by not using that flag, or by compiling Berkeley DB with the