345
do not allow negative values to be used. That is, verify the minimum as well as the maximum of
the range of acceptable values.
Phase: Implementation
Be especially careful to validate all input when invoking code that crosses language boundaries,
such as from an interpreted language to native code. This could create an unexpected interaction
between the language boundaries. Ensure that you are not violating any of the expectations
of the language with which you are interfacing. For example, even though Java may not be
susceptible to buffer overflows, providing a large argument in a call to native code might trigger
an overflow.
Phase: Architecture and Design
Phase: Operation
Strategy = Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks
[REF-76]. If possible, create isolated accounts with limited privileges that are only used for a
single task. That way, a successful attack will not immediately give the attacker access to the
rest of the software or its environment. For example, database applications rarely need to run as
the database administrator, especially in day-to-day operations.
Phase: Architecture and Design
Phase: Operation
Strategy = Sandbox or Jail
Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between
the process and the operating system. This may effectively restrict which files can be accessed
in a particular directory or which commands can be executed by the software. OS-level examples
include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide
some protection. For example, java.io.FilePermission in the Java SecurityManager allows the
software to specify restrictions on file operations. This may not be a feasible solution, and it
only limits the impact to the operating system; the rest of the application may still be subject to
compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
Effectiveness = Limited
The effectiveness of this mitigation depends on the prevention capabilities of the specific
sandbox or jail being used and might only help to reduce the scope of an attack, such as
restricting the attacker to certain system calls or limiting the portion of the file system that can be
accessed.
Demonstrative Examples
Example 1:
In the code snippet below, an untrusted integer value is used to reference an object in an array.
Example Language: Java (Bad)
public String getValue(int index) {
return array[index];
}
If index is outside of the range of the array, this may result in an ArrayIndexOutOfBounds Exception
being raised.
Example 2:
The following example takes a user-supplied value to allocate an array of objects and then
operates on the array.
CWE Version 4.14
CWE-129: Improper Validation of Array Index
CWE-129: Improper Validation of Array Index