Integer Overflow - Security Ramifications

Security Ramifications

In some situations, a program may make the assumption that a variable always contains a positive value. If the variable has a signed integer type, an overflow can cause its value to wrap and become negative. This overflow violates the program's assumption and may lead to unintended behavior. Similarly, subtracting from a small unsigned value may cause it to wrap to a large positive value which may also be an unexpected behavior. Multiplying or adding two integers may result in a value that is non-negative, but unexpectedly small. If this number is used as the number of bytes to allocate for a buffer, the buffer will be allocated unexpectedly small, leading to a potential buffer overflow.

Some languages, such as Ada (and certain variants of functional languages), provide mechanisms to make accidental overflows trigger an exception condition. In contrast, Python seamlessly converts a number that becomes too large for an integer to a long. (This occurred in Python 2.4.)