Unintentional pointer scaling
From OWASP
This is a Vulnerability. To view all vulnerabilities, please see the Vulnerability Category page.
Last revision (mm/dd/yy): 3/1/2009
Vulnerabilities Table of Contents
Description
In C and C++, one may accidentally refer to the wrong memory due to the semantics of when math operations are implicitly scaled.
Consequences
Often results in buffer overflow conditions.
Exposure period
- Design: Could choose a language with abstractions for memory access.
- Implementation: This problem generally is due to a programmer error.
Platform
C and C++.
Required resources
Any
Severity
High
Likelihood of exploit
Medium
Programmers will often try to index from a pointer by adding a number of bytes, even though this is wrong, since C and C++ implicitly scale the operand by the size of the data type.
Risk Factors
TBD
Examples
int *p = x; char * second_char = (char *)(p + 1);
In this example, second_char is intended to point to the second byte of p. But, adding 1 to p actually adds sizeof(int) to p, giving a result that is incorrect (3 bytes off on 32-bit platforms).
If the resulting memory address is read, this could potentially be an information leak. If it is a write, it could be a security-critical write to unauthorized memory - whether or not it is a buffer overflow.
Note that the above code may also be wrong in other ways, particularly in a little endian environment.
Related Attacks
Related Vulnerabilities
Related Controls
- Design: Use a platform with high-level memory abstractions.
- Implementation: Always use array indexing instead of direct pointer manipulation.
- Other: Use technologies for preventing buffer overflows.
Related Technical Impacts
References
TBD
