Some implementations provide a nonportable environment pointer that is valid when main() is called but may be invalidated by operations that modify the environment.
The C Standard, J.5.1 2 [ISO/IEC 9899:20112024], states
In a hosted environment, the main function receives a third argument, char *envp[], that points to a null-terminated array of pointers to char, each of which points to a string that provides information about the environment for this execution of the program (5.1.2.3.2).
Consequently, under a hosted environment supporting this common extension, it is possible to access the environment through a modified form of main():
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Because envp may no longer point to the current environment, this program has undefined unanticipated behavior.
Compliant Solution (POSIX)
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Because envp no longer points to the current environment, this program has undefined unanticipated behavior.
Compliant Solution (Windows)
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Using the envp environment pointer after the environment has been modified can result in undefined behavior.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
ENV31-C | Low | Probable | Medium | P4 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Astrée |
| Supported | |||||||
| Compass/ROSE |
| Cppcheck Premium | 24.9.0 | premium-cert-env31-c | Fully implemented | |||||
| Helix QAC |
| DF4991, DF4992, DF4993 |
| LDRA tool suite |
| 118 S | Fully Implemented | ||||||
| Parasoft C/C++test |
| CERT_C-ENV31-a | Do not rely on an environment pointer following an operation that may invalidate it | ||||||
| CERT C: Rule ENV31-C | Checks for environment pointer invalidated by previous operation (rule fully covered) |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
Key here (explains table format and definitions)
Taxonomy | Taxonomy item | Relationship |
|---|---|---|
| CERT C |
| VOID ENV31-CPP. Do not rely on an environment pointer following an operation that may invalidate it | Prior to 2018-01-12: CERT: Unspecified Relationship |
Bibliography
| [IEEE Std 1003.1:2013] | XSH, System Interfaces, setenv |
| [ISO/IEC 9899: |
| 2024] | J.5. |
| 2, "Environment Arguments" | |
| [MSDN] | getenv, _wgetenv,_putenv_s, _wputenv_s |
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