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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 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 | ||||
|---|---|---|---|---|
| ||||
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.
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| Code Block | ||||
|---|---|---|---|---|
| ||||
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 */ } } |
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| Code Block | ||||
|---|---|---|---|---|
| ||||
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 */ } } } |
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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 | Detectable |
|---|
Repairable | Priority | Level |
|---|---|---|
INT05-C |
Medium | Probable |
Yes |
No |
P8 |
L2 |
Automated Detection
Tool | Version | Checker | Description |
|---|
Fortify SCA
V. 5.0
| Axivion Bauhaus Suite |
| CertC-INT05 | |||||||
| CodeSonar |
| MISC.NEGCHAR | Negative Character Value |
| Compass/ROSE |
Can detect violations of this recommendation. In particular, it notes uses of the |
| Helix QAC |
| C5005 | |||||||
| LDRA tool suite |
| 44 S | Enhanced Enforcement | ||||||
| Parasoft C/C++test |
| CERT_C-INT05-a | Avoid using unsafe string functions that do not check bounds | ||||||
| PC-lint Plus |
| 586 | Fully supported |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
| SEI CERT C++ |
| Coding Standard | VOID INT05-CPP. Do not use input functions to convert character data if they cannot handle all possible inputs |
| MITRE CWE | CWE-192, Integer coercion error CWE-197, Numeric truncation error |
Bibliography
| [ |
strtol, strtoll, strtoul, and strtoull Functions," and section 7.21.6, "Formatted Input/Output Functions"| Klein 2002] |
| [Linux 2008] | scanf(3) |
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