Incorrect Pointer Scaling
Weakness ID: 468 (Weakness Base)Status: Incomplete
+ Description

Description Summary

In C and C++, one may often accidentally refer to the wrong memory due to the semantics of when math operations are implicitly scaled.
+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

C

C++

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Availability

Incorrect pointer scaling will often result in buffer overflow conditions. Confidentiality can be compromised if the weakness is in the context of a buffer over-read or under-read.

+ Likelihood of Exploit

Medium

+ Demonstrative Examples

Example 1

(Bad Code)
Example Language: C 
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.

+ Potential Mitigations

Phase: Architecture and Design

Use a platform with high-level memory abstractions.

Phase: Implementation

Always use array indexing instead of direct pointer manipulation.

Other: Use technologies for preventing buffer overflows.

+ Other Notes

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.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory465Pointer Issues
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class682Incorrect Calculation
Research Concepts (primary)1000
ChildOfCategoryCategory737CERT C Secure Coding Section 03 - Expressions (EXP)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPUnintentional pointer scaling
CERT C Secure CodingEXP08-CEnsure pointer arithmetic is used correctly
+ White Box Definitions

A weakness where code path has a statement that performs a pointer arithmetic operation on a pointer to datatype1 and casts the result of the operation to a pointer type to datatype2 where datatype2 has different length than the datatype1 and the datatype1 has different length than a character type.

+ Content History
Submissions
Submission DateSubmitterOrganizationSource
CLASPExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
2008-09-08CWE Content TeamMITREInternal
updated Applicable Platforms, Common Consequences, Relationships, Other Notes, Taxonomy Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative Examples
2009-07-17KDM AnalyticsExternal
Improved the White Box Definition
2009-07-27CWE Content TeamMITREInternal
updated White Box Definitions
2009-10-29CWE Content TeamMITREInternal
updated Common Consequences
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Unintentional Pointer Scaling
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