Problem - Kevin Tafuro

not be allocated, the function will call abort( ) to terminate the program
immediately. Otherwise, it will then build the new environment and replace the old
environ pointer with a pointer to the newly allocated one. Note that the memory is
allocated in one chunk rather than in smaller pieces for the individual strings. While
this is not strictly necessary (and it does not provide any specific security benefit), it’s
faster and places less strain on memory allocation. Note, however, that you should
be performing this operation early in your program, so heap fragmentation shouldn’t
be much of an issue.
#include
#include
#include
#include
extern char **environ;
/* These arrays are both NULL-terminated. */
static char *spc_restricted_environ[ ] = {
"IFS= \t\n",
"PATH=" _PATH_STDPATH,
0
};
static char *spc_preserve_environ[ ] = {
"TZ",
0
};
void spc_sanitize_environment(int preservec, char **preservev) {
int i;
char **new_environ, *ptr, *value, *var;
size_t arr_size = 1, arr_ptr = 0, len, new_size = 0;
for (i = 0; (var = spc_restricted_environ[i]) != 0; i++) {
new_size += strlen(var) + 1;
arr_size++;
}
for (i = 0; (var = spc_preserve_environ[i]) != 0; i++) {
if (!(value = getenv(var))) continue;
new_size += strlen(var) + strlen(value) + 2; /* include the '=' */
arr_size++;
}
if (preservec && preservev) {
for (i = 0; i < preservec && (var = preservev[i]) != 0; i++) {
if (!(value = getenv(var))) continue;
new_size += strlen(var) + strlen(value) + 2; /* include the '=' */
arr_size++;
}
}
new_size += (arr_size * sizeof(char *));
if (!(new_environ = (char **)malloc(new_size))) abort( );
new_environ[arr_size - 1] = 0;
6 | Chapter 1: Safe Initialization
This is the Title of the Book, eMatter Edition
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