SEI CERT C Coding Standard

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Integer values that originate from untrusted sources must be guaranteed correct if they are used in any of the following ways:

  • as an array index
  • in any pointer arithmetic
  • as a length or size of an object
  • as the bound of an array (for example, a loop counter)
  • as an argument to a memory allocation function
  • in security critical code

Integer values can be invalidated due to exceptional conditions such as overflow, truncation, or sign error leading to exploitable vulnerabilities. Failure to provide proper range checking can also lead to exploitable vulnerabilities.

Recommendations

INT00-A. Understand the data model used by your implementation(s)

INT01-A. Use size_t for all integer values representing the size of an object

INT02-A. Understand integer conversion rules

INT03-A. Use a secure integer library

INT04-A. Enforce limits on integer values originating from untrusted sources

INT05-A. Do not use functions that input character data and convert the data if these functions cannot handle all possible inputs

INT06-A. Use strtol() to convert a string token to an integer

INT07-A. Explicitly specify signed or unsigned for character types

INT08-A. Verify that all integer values are in range

INT09-A. Ensure enumeration constants map to unique values

INT10-A. Define integer constants as an enum value

INT11-A. Be careful converting small signed integers to larger unsigned integers

INT12-A. Do not make assumptions about the type of a bit-field when used in an expression

INT13-A. Do not assume that a right shift operation is implemented as a logical or an arithmetic shift

INT14-A. Distinguish bitmaps from numeric types

INT15-A. Avoid pointer to integer and integer to pointer conversions

Rules

INT31-C. Ensure that integer conversions do not result in lost or misinterpreted data

INT32-C. Ensure that integer operations do not result in an overflow

INT33-C. Ensure that division and modulo operations do not result in divide-by-zero errors

INT35-C. Upcast integers before comparing or assigning to a larger integer size

INT36-C. Do not shift a negative number of bits or more bits than exist in the operand

INT37-C. Arguments to character handling functions must be representable as an unsigned char

Risk Assessment Summary

Recommendation

Severity

Likelihood

Remediation Cost

Priority

Level

INT00-A

1 (low)

1 (unlikely)

1 (low)

P1

L3

INT01-A

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT02-A

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT03-A

2 (medium)

2 (probable)

1 (hig)

P4

L3

INT04-A

2 (medium)

2 (probable)

1 (high)

P4

L3

INT05-A

1 (low)

2 (low)

2 (medium)

P2

L3

INT06-A

1 (low)

2 (low)

2 (medium)

P2

L3

INT07-A

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT08-A

2 (medium)

2 (probable)

1 (high)

P4

L3

INT09-A

1 (low)

1 (unlikely)

3 (low)

P3

L3

INT10-A

1 (medium)

1 (probable)

2 (medium)

P2

L3

INT11-A

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT12-A

2 (medium)

1 (low)

2 (medium)

P4

L3

INT13-A

3 (high)

1 (probable)

2 (medium)

P6

L2

INT14-A

2 (medium)

1 (unlikely)

2 (medium)

P4

L3

INT15-A

1 (low)

2 (probable)

1 (high)

P2

L3

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

INT31-C

3 (high)

2 (probable)

1 (high)

P6

L2

INT32-C

3 (high)

2 (probable)

1 (high)

P6

L2

INT33-C

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT35-C

3 (high)

3 (probable)

2 (medium)

P18

L1

INT36-C

2 (medium)

2 (probable)

2 (medium)

P8

L2

INT37-C

1 (low)

1 (unlikely)

3 (low)

P3

L3

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