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

Compliant Solution

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(local copy)

For the case where the intent of the non-compliant code example is to use the modified value of the environment variable locally and not modify the environment, this compliant solution makes This is a compliant code solution. If it is necessary to modify the value of the string returned by the function getenv(), then the programmer should make a local copy of that string value, and then modify modifies the local copy of that string.

const char *env;
char *copy_of_env;

if ((env = getenv("TEST_ENV")) != NULL) {
   copy_of_env = (char *)malloc(strlen(env) + 1);

   if (copy_of_env != NULL) {
      strcpy(copy_of_env, env);
   }
   else {
      /* Error handling */
   }

   copy_of_env[0] = 'a';
}

Compliant Solution (modifying the environment in POSIX)

For the case where the intent of the non-compliant code example is to modify the environment, this compliant solution will perform that action using the POSIX putenv() function.

const char *env;
char *copy_of_env;

if ((env = getenv("TEST_ENV")) != NULL) {
   copy_of_env = (char *)malloc(sizeof("TEST_ENV=") + strlen(env));

   if (copy_of_env != NULL) {
      strcpy(copy_of_env, "TEST_ENV=");
      strcat(copy_of_env, env);
      copy_of_env[sizeof("TEST_ENV=") - 1] = 'a';
      if (putenv(copy_of_env) != 0) {
        /* handle error */
      }
   }
   else {
      /* Error handling */
   }
}

Risk Assessment

The modified string may be overwritten by a subsequent call to the getenv() function.  Depending on the implementation, modifying the string returned by getenv() may or may not modify the environment.

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