Upon successful completion, getenv() function returns a pointer to a null-terminated string containing the value of a specified environmental variable. If the specified variable cannot be found the environment of the calling process, a null pointer is returned.

Do not modify the value returned by the getenv() function. Create a copy and make your changes locally, using setenv() to update the environment when necessary. This allows the implementation to properly allocate and manage memory.

Non-Compliant Code Example

This non-compliant code example showing that modification of the string value returned by the function getenv().

int foo()
{
    char *env;
    env = getenv("TEST_ENV");
    env[0] = 'a';

    /*Do some more things*/

    return 0;
}

Compliant Code Solution

This is a compliant code solution. If it is necessary to modify the value the string returned by the function getenv(), then the programmer should make a local copy of that string value, and then modify the local copy of that string.

int foo()
{
    char *env;
    char *copy_of_env;

    env = getenv("TEST_ENV");
    copy_of_env = malloc( strlen(env) + 1 );
    /* Error handling */
    strcpy(copy_of_env, env);

    copy_of_env[0] = 'a';

    /*Do some more things*/

    return 0;
}

Risk Assessment

References

\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 7.20.4, "Communication with the environment"
\[[Open Group 04|AA. C References#Open Group 04]\] Chapter 8, "Environment Variables", [strdup|http://www.opengroup.org/onlinepubs/009695399/functions/strdup.html]
\[[Viega 03|AA. C References#Viega 03]\] Section 3.6, "Using Environment Variables Securely"