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Alternatively, input character data as a null-terminated byte string and convert to an integer value using strtol() or a related function. (See recommendation INT06ERR34-C. Use strtol() or a related function to convert a string token to an integerDetect errors when converting a string to a number.)

Noncompliant Code Example

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Code Block

bgColor	#FFcccc
lang	c

long slnum_long;

if (scanf("%ld", &slnum_long) != 1) {
  /* handleHandle error */
}

In general, do not use scanf() to parse integers or floating-point numbers from input strings because the input could contain numbers not representable by the argument type.

Compliant Solution (Linux)

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This compliant example uses the Linux {{scanf()}} implementation's built -in error handling to validate input. On Linux platforms, {{scanf()}} sets {{errno}} to {{ERANGE}} if the result of integer conversion cannot be represented within the size specified by the format string \[ [Linux 2008|AA. Bibliography#Linux 08]\]. Note that this solution is a platform dependent solution. Therefore, this should only be used where portability is not a , so it should be used only where portability is not a concern.

Code Block

bgColor	#ccccff
lang	c

long slnum_long;
errno = 0;

if (scanf("%ld", &slnum_long) != 1) {
  /* handleHandle error */
}
else if (ERANGE == errno) {
  if (puts("number out of range\n") == EOF) {
      /* Handle error */
  }
}

...

This compliant example uses fgets() to input a string and strtol() to convert the string to an integer. Error checking is provided to make sure that the value is a valid integer in the range of long.

Code Block

bgColor	#ccccff
lang	c

char buff[25];
char *end_ptr;
long slnum_long;

if (fgets(buff, sizeof(buff), stdin) == NULL) {
  if (puts("EOF or read error\n") == EOF) {
    /* Handle error */
  }
} else {
  errno = 0;

  slnum_long = strtol(buff, &end_ptr, 10);

  if (ERANGE == errno) {
    if (puts("number out of range\n") == EOF) {
      /* Handle error */
    }
  }
  else if (end_ptr == buff) {
    if (puts("not valid numeric input\n") == EOF) {
      /* Handle error */
    }
  }
  else if ('\n' != *end_ptr && '\0' != *end_ptr) {
    if (puts("extra characters on input line\n") == EOF) {
      /* Handle error */
    }
  }
}

Note that this solution treats any trailing characters, including white-space whitespace characters, as an error condition.

Risk Assessment

While it Although it is relatively rare for a violation of this recommendation to result in a security vulnerability, it can easily result in lost or misinterpreted data.

Recommendation	Severity	Likelihood	Remediation Cost	Priority	Level
INT05-C

medium

Medium

probable

Probable

high

High

P4

L3

Automated Detection

Tool	Version	Checker	Description

Section
Fortify SCA

Section
V. 5.0

Section
can detect violations of this recommendation with the CERT C Rule Pack

section Sectioncan

Axivion Bauhaus Suite

Include Page

	Axivion Bauhaus Suite_V
	Axivion Bauhaus Suite_V

CertC-INT05

CodeSonar

Include Page

	CodeSonar_V
	CodeSonar_V

MISC.NEGCHAR

Negative Character Value

Compass/ROSE

Can detect violations of this recommendation. In particular, it notes uses of the scanf() family of functions where on the type specifier is a floating-point or integer type

Helix QAC

Include Page