The C Standard says getenv() has the following behavior Standard [ISO/IEC 9899:2011] states that getenv() has the following behavior:
The
getenvfunction returns a pointer to a string associated with the matched list member. The string pointed to shall not be modified by the program but may be overwritten by a subsequent call to thegetenvfunction.
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C11 Annex K provides the getenv_s()function for getting a value from the current environment [ISO/IEC 9899:2011]. However, note that according to the standard, getenv_s() can still have data races with other threads of execution which that modify the environment list.
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Windows also provides the _dupenv_s() and wdupenv_s() functions for getting a value from the current environment [MSDN]. The _dupenv_s() function searches the list of environment variables for a specified name. If the name is found, a buffer is allocated; the variable's value is copied into the buffer, and the buffer's address and number of elements are returned. By allocating the buffer itself, _dupenv_s() and _wdupenv_s() provide a more convenient alternative to getenv_s() and _wgetenv_s().
It is the The calling program 's responsibility to free is responsible for freeing any allocated buffers returned by these functions.
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Recommendation | Severity | Likelihood | Remediation Cost | Priority | Level |
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ENV00-C | lowLow | probableProbable | mediumMedium | P4 | L3 |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
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Related Guidelines
| CERT C++ Secure Coding Standard | ENV00-CPP. Do not store the pointer to the string returned by getenv() |
| ISO/IEC TR 24731-2 | |
| ISO/IEC TS 17961 (Draft) | Using an object overwritten by getenv, localeconv, setlocale, and strerror [libuse] |
Bibliography
| [ISO/IEC 9899:2011] | Section Subclause 7.22.4, "Communication with the Environment" Section Subclause 7.22.4.6, "The getenv Function"Subclause K.3.6.2.1, "The getenv_s Function" | ||
| [MSDN] | _dupenv_s() and _wdupenv_s() | ||
| [Open Group 2004] | Chapter 8, "Environment Variables"strdup | ||
| [Viega 2003] | Section 3.6, "Using Environment Variables Securely" | [ISO/IEC 9899:2011] | Section K.3.6.2.1, "The getenv_s function" |
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