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The gets() function was deprecated by Technical Corrigendum 3 to C99 and eliminated from C11. The Annex K gets_s() function is a recommended alternative to gets().
Obsolescent Functions
Functions in the first column of the following table are hereby defined to be obsolescent functions. To remediate invocations of obsolescent functions, an application might use inline coding that, in all respects, conforms to this guideline, or an alternative library that, in all respects, conforms to this guideline, or alternative non-obsolescent functions.
Obsolescent | Recommended | Rationale |
|---|---|---|
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| Non-reentrant |
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| No error detection |
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| No error detection |
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| No error detection |
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| No error detection |
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| Non-reentrant |
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| No exclusive access to file |
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| No exclusive access to file |
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| No error detection |
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| No error detection |
The atof, and (), atoi(), atol()atoll functions are obsolescent because the ()strodstrtod(), strtof(), strtol(), strtold(), strtoll(), strotulstrtoul(), and strtoull functions can emulate their usage and have more robust error handling capabilities. See guideline INT05-C. Do not use input functions to convert character data if they cannot handle all possible inputs.()
The fopen and ()freopen functions are obsolescent because the ()fopen_s and ()freopen_s functions can emulate their usage and improve security by protecting the file from unauthorized access by setting its file protection and opening the file with exclusive access [ISO/IEC WG14 N1173].()
The setbuf function is obsolescent because ()setbuf does not return a value and can be emulated using ()setvbuf. See guideline void FIO12ERR07-C. Prefer setvbuf() to setbuf()functions that support error checking over equivalent functions that don't.()
The rewind function is obsolescent because ()rewind does not return a value and can be emulated using ()fseek. See guideline void FIO07ERR07-C. Prefer fseek() to rewind()functions that support error checking over equivalent functions that don't.()
The asctime and ()ctime functions are obsolescent because they use non-reentrant static buffers and can be emulated using ()asctime_s and ()ctime_s.()
Unchecked Obsolescent Functions
The following If you are using platforms that support Annex K, then functions in the first column of the following table are hereby defined to be unchecked obsolescent functions:
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To remediate invocations of unchecked obsolescent functions, an application might use inline coding that, in all respects, conforms to this guideline, or an alternative library that, in all respects, conforms to this guideline, or alternative nonobsolescent functions from C11, Annex K:
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obsolescent functions, with functions in the second column being the recommended alternatives from Annex K.
Obsolescent | Recommended |
|---|---|
| bsearch() | bsearch_s() |
| fprintf() | fprintf_s() |
| fscanf() | fscanf_s() |
| fwprintf() | fwprintf_s() |
| fwscanf() | fwscanf_s() |
| getenv() | getenv_s() |
| gmtime() | gmtime_s() |
| localtime() | localtime_s() |
| mbsrtowcs() | mbsrtowcs_s() |
| mbstowcs() | mbstowcs_s() |
| memcpy() | memcpy_s() |
| memmove() | memmove_s() |
| printf() | printf_s() |
| qsort() | qsort_s() |
| scanf() | scanf_s() |
| snprintf() | snprintf_s() |
| sprintf() | sprintf_s() |
| sscanf() | sscanf_s() |
| strcat() | strcat_s() |
| strcpy() | strcpy_s() |
| strerror() | strerror_s() |
| strlen() | strnlen_s() |
| strncat() | strncat_s() |
| strncpy() | strncpy_s() |
| strtok() | strtok_s() |
| swprintf() | swprintf_s() |
| swscanf() | swscanf_s() |
| vfprintf() | vfprintf_s() |
| vfscanf() | vfscanf_s() |
| vfwprintf() | vfwprintf_s() |
| vfwscanf() | vfwscanf_s() |
| vprintf() | vprintf_s() |
| vscanf() | vscanf_s() |
| vsnprintf() | vsnprintf_s() |
| vsprintf() | vsprintf_s() |
| vsscanf() | vsscanf_s() |
| vswprintf() | vswprintf_s() |
| vswscanf() | vswscanf_s() |
| vwprintf() | vwprintf_s() |
| vwscanf() | vwscanf_s() |
| wcrtomb() | wcrtomb_s() |
| wcscat() | wcscat_s() |
| wcscpy() | wcscpy_s() |
| wcslen() | wcsnlen_s() |
| wcsncat() | wcsncat_s() |
| wcsncpy() | wcsncpy_s() |
| wcsrtombs() | wcsrtombs_s() |
| wcstok() | wcstok_s() |
| wcstombs() | wcstombs_s() |
| wctomb() | wctomb_s() |
| wmemcpy() | wmemcpy_s() |
| wmemmove() | wmemmove_s() |
| wprintf() | wprintf_s() |
| wscanf() | wscanf_s() |
For information on the tmpfile() and tmpfile_s() functions, see FIO21-C. Do not create temporary files in shared directories.
For information on the memset() and memset_s() functions, see MSC06-C. Beware of compiler optimizations.
To remediate invocations of obsolescent functions, an application might use any of the following recommended functions from ISOor alternative nonobsolescent functions from ISO/IEC TR 24731-2, Extensions to the C Library—Part II: Dynamic Allocation Functions [ISO/IEC TR 24731-2]:
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Noncompliant Code Example
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The deprecated and obsolescent functions enumerated in this guideline are commonly associated with software vulnerabilities.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|
MSC24-C | High | Probable | Medium | P12 | L1 |
Automated Detection
| Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Astrée |
| stdlib-use-ato stdlib-macro-ato stdlib-use-atoll stdlib-macro-atoll | Partially checked | ||||||
| Axivion Bauhaus Suite |
| CertC-MSC24 | Fully implemented | ||||||
| CodeSonar |
| BADFUNC.* | A number of CodeSonar's "Use of *" checks are for deprecated/obsolescent functions | ||||||
| CC2.MSC34 | Fully implemented | |||||||
| LDRA tool suite |
| 44 S | Fully implemented | ||||||
| Parasoft C/C++test |
| CERT_C-MSC24-a | The library functions atof, atoi and atol from library stdlib.h shall not be used | ||||||
| PC-lint Plus |
| 586 | Fully supported | ||||||
| Polyspace Bug Finder |
| CERT C: Rec. MSC24-C | Checks for use of obsolete standard function (rec. fully covered) | ||||||
| PVS-Studio |
| V513, V2001, V2002 | |||||||
| RuleChecker |
| stdlib-use-ato stdlib-macro-ato stdlib-use-atoll stdlib-macro-atoll | Partially checked |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
INT06
Use strtol() or a related function to convert a string token to an integer
remediation of existing
code
Detect errors when converting a string to a number |
| ISO/IEC TR 24772 | Use of Libraries [TRJ] |
| MISRA C:2012 | Rule 21.3 (required) |
| MITRE CWE | CWE-20, Insufficient input validation |
Bibliography
| [Apple 2006] | Apple Secure Coding Guide, "Avoiding Race Conditions and Insecure File Operations" |
| [Burch 2006] | Specifications for Managed Strings, Second Edition |
| [Drepper 2006] | Section 2.2.1 "Identification When Opening" |
| [IEEE Std 1003.1:2013] | XSH, System Interfaces, open |
| ISO/IEC 23360-1:2006 |
| [ISO/IEC WG14 N1173] | Rationale for TR 24731 Extensions to the C Library Part I: Bounds-checking interfaces |
| [Klein 2002] | "Bullet Proof Integer Input Using strtol()" |
| [Linux 2008] | strtok(3) |
| [Seacord 2013] | Chapter 2, "Strings" Chapter 8, "File I/O" |
| [Seacord 2005b] | "Managed String Library for C, C/C++" |
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