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This behavior is more informally called unsigned integer wrapping. Unsigned integer operations can wrap if the resulting value cannot be represented by the underlying representation of the integer. The following table indicates which operators can result in wrapping:

Operator

Wrap

Operator

Wrap

Operator

Wrap

Operator

Wrap

+

Yes

-=

Yes

<<

Yes

<

No

-

Yes

*=

Yes

>>

No

>

No

*

Yes

/=

No

&

No

>=

No

/

No

%=

No

|

No

<=

No

%

No

<<=

Yes

^

No

==

No

++

Yes

>>=

No

~

No

!=

No

--

Yes

&=

No

!

No

&&

No

=

No

|=

No

un +

No

||

No

+=

Yes

^=

No

un -

Yes

?:

No

 


The following sections examine specific operations that are susceptible to unsigned integer wrap. When operating on integer types with less precision than int, integer promotions are applied. The usual arithmetic conversions may also be applied to (implicitly) convert operands to equivalent types before arithmetic operations are performed. Programmers should understand integer conversion rules before trying to implement secure arithmetic operations. (See INT02-C. Understand integer conversion rules.)

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Integer wrap can lead to buffer overflows and the execution of arbitrary code by an attacker.

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

INT30-C

High

Likely

High

P9

L2

Automated Detection

Tool

Version

Checker

Description

Astrée
Include Page
Astrée_V
Astrée_V
integer-overflowFully checked
CodeSonar
Include Page
CodeSonar_V
CodeSonar_V

ALLOC.SIZE.ADDOFLOW
ALLOC.SIZE.IOFLOW
ALLOC.SIZE.MULOFLOW
ALLOC.SIZE.SUBUFLOW
MISC.MEM.SIZE.ADDOFLOW
MISC.MEM.SIZE.BAD
MISC.MEM.SIZE.MULOFLOW
MISC.MEM.SIZE.SUBUFLOW

Addition overflow of allocation size
Integer overflow of allocation size
Multiplication overflow of allocation size
Subtraction underflow of allocation size
Addition overflow of size
Unreasonable size argument
Multiplication overflow of size
Subtraction underflow of size

Compass/ROSE

 

 



Can detect violations of this rule by ensuring that operations are checked for overflow before being performed (Be mindful of exception INT30-EX2 because it excuses many operations from requiring validation, including all the operations that would validate a potentially dangerous operation. For instance, adding two unsigned ints together requires validation involving subtracting one of the numbers from UINT_MAX, which itself requires no validation because it cannot wrap.)

Coverity
6.5
Include Page
Coverity_V
Coverity_V
INTEGER_OVERFLOWImplemented
Klocwork
Include Page
Klocwork_V
Klocwork_V
NUM.OVERFLOW
CWARN.NOEFFECT.OUTOFRANGE
 

LDRA tool suite
Include Page
LDRA_V
LDRA_V
493 S, 494 SPartially implemented
Parasoft C/C++test

Include Page
Parasoft_V
Parasoft_V

CERT_C-INT30-a
CERT_C-INT30-b
CERT_C-INT30-c

Avoid integer overflows
Integer overflow or underflow in constant expression in '+', '-', '*' operator
Integer overflow or underflow in constant expression in '<<' operator

Polyspace Bug Finder
R2016a

Include Page
Polyspace Bug Finder_V
Polyspace Bug Finder_V

CERT C: Rule INT30-C

Checks for:

  • Unsigned integer overflow
Overflow from operation between unsigned integers
  • Unsigned integer constant overflow

Rule fully covered.

PRQA QA-C
Include Page
PRQA QA-C_v
PRQA QA-C_v

2910

(

[C

)

], 2911

(

[D

)

], 2912

(

[A

)

],

2913

(S)

[S], 3383, 3384, 3385, 3386

Partially implemented
PRQA QA-C++
Include Page
cplusplus:PRQA QA-C++_V
cplusplus:PRQA QA-C++_V
2910, 2911, 2912, 2913
PVS-Studio

Include Page
PVS-Studio_V
PVS-Studio_V

V658
TrustInSoft Analyzer

Include Page
TrustInSoft Analyzer_V
TrustInSoft Analyzer_V

unsigned overflowExhaustively verified.

Related Vulnerabilities

CVE-2009-1385 results from a violation of this rule. The value performs an unchecked subtraction on the length of a buffer and then adds those many bytes of data to another buffer [xorl 2009]. This can cause a buffer overflow, which allows an attacker to execute arbitrary code.

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Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

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Key here (explains table format and definitions)

Taxonomy

Taxonomy item

Relationship

CERT C
Coding Standard
INT02-C. Understand integer conversion rulesPrior to 2018-01-12: CERT: Unspecified Relationship
CERT CARR30-C. Do not form or use out-of-bounds pointers or array subscriptsPrior to 2018-01-12: CERT: Unspecified Relationship
CERT CARR36-C. Do not subtract or compare two pointers that do not refer to the same arrayPrior to 2018-01-12: CERT: Unspecified Relationship
CERT CARR37-C. Do not add or subtract an integer to a pointer to a non-array objectPrior to 2018-01-12: CERT: Unspecified Relationship
CERT CCON08-C. Do not assume that a group of calls to independently atomic methods is atomicPrior to 2018-01-12: CERT: Unspecified Relationship
ISO/IEC TR 24772:2013Arithmetic Wrap-Around Error [FIF]
MITRE CWE
Prior to 2018-01-12: CERT: Unspecified Relationship
CWE 2.11CWE-190, Integer Overflow or Wraparound2016-12-02: CERT: Rule subset of CWE
CWE 2.11CWE-1312017-05-16: CERT: Partial overlap
CWE 2.11CWE-1912017-05-18: CERT: Partial overlap
CWE 2.11CWE-6802017-05-18: CERT: Partial overlap

CERT-CWE Mapping Notes

Key here for mapping notes

CWE-131 and INT30-C


  • Intersection( INT30-C, MEM35-C) = Ø



  • Intersection( CWE-131, INT30-C) =



  • Calculating a buffer size such that the calculation wraps. This can happen, for example, when using malloc() or operator new[] to allocate an array, multiplying the array item size with the array dimension. An untrusted dimension could cause wrapping, resulting in a too-small buffer being allocated, and subsequently overflowed when the array is initialized.



  • CWE-131 – INT30-C =



  • Incorrect calculation of a buffer size that does not involve wrapping. This includes off-by-one errors, for example.


INT30-C – CWE-131 =


  • Integer wrapping where the result is not used to allocate memory.




CWE-680 and INT30-C

Intersection( CWE-680, INT30-C) =


  • Unsigned integer overflows that lead to buffer overflows


CWE-680 - INT30-C =


  • Signed integer overflows that lead to buffer overflows


INT30-C – CWE-680 =


  • Unsigned integer overflows that do not lead to buffer overflows


CWE-191 and INT30-C

Union( CWE-190, CWE-191) = Union( INT30-C, INT32-C) Intersection( INT30-C, INT32-C) == Ø

Intersection(CWE-191, INT30-C) =


  • Underflow of unsigned integer operation


CWE-191 – INT30-C =


  • Underflow of signed integer operation


INT30-C – CWE-191 =


  • Overflow of unsigned integer operation


Bibliography

[Bailey 2014]Raising Lazarus - The 20 Year Old Bug that Went to Mars
[Dowd 2006]Chapter 6, "C Language Issues" ("Arithmetic Boundary Conditions," pp. 211–223)
[ISO/IEC 9899:2011]Subclause 6.2.5, "Types"
[Seacord 2013b]Chapter 5, "Integer Security"
[Viega 2005]Section 5.2.7, "Integer Overflow"
[VU#551436]
 

[Warren 2002]Chapter 2, "Basics"
[Wojtczuk 2008]
 

[xorl 2009]"CVE-2009-1385: Linux Kernel E1000 Integer Underflow"

 


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