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/* some musl versions incorrectly mark fgetgrent() as a GNU extension */
#define _GNU_SOURCE
#include <assert.h> /* assert */
#include <errno.h> /* ENOENT, ERANGE */
#include <grp.h> /* fgetgrent, getgrent, struct group */
#include <pthread.h> /* pthread_mutex_* */
#include <stddef.h> /* NULL, size_t */
#include <stdint.h> /* ptrdiff_t, uintptr_t */
#include <stdio.h> /* FILE */
#include <string.h> /* memcpy, stpcpy, strlcpy, strlen */
#define ALIGN_PTR_TO_SIZE_OF(ptr, type) \
((type *) ((((uintptr_t)(ptr)) + sizeof(type) - 1) \
& ~(sizeof(type) - 1)))
static pthread_mutex_t grent_mutex = PTHREAD_MUTEX_INITIALIZER;
static int __fgetgrent_r(FILE *stream, struct group *grp, char *buf, size_t len,
struct group **result)
{
struct group *grtmp;
char *cursor = buf, *end = buf + len;
*result = NULL;
pthread_mutex_lock(&grent_mutex);
grtmp = stream != NULL ? fgetgrent(stream) : getgrent();
if (grtmp == NULL) {
pthread_mutex_unlock(&grent_mutex);
return ENOENT;
}
memcpy(grp, grtmp, sizeof(*grp));
if (grtmp->gr_name != NULL) {
grp->gr_name = cursor;
cursor += strlcpy(cursor, grtmp->gr_name, end - cursor) + 1;
if (cursor > end) {
goto err_unlock;
}
}
if (grtmp->gr_passwd != NULL) {
grp->gr_passwd = cursor;
cursor += strlcpy(cursor, grtmp->gr_passwd, end - cursor) + 1;
if (cursor > end) {
goto err_unlock;
}
}
if (grtmp->gr_mem != NULL) {
char **members = ALIGN_PTR_TO_SIZE_OF(cursor, char *);
ptrdiff_t nameslen = 0;
size_t nmem = 0;
/* Calculate total size of strings plus their pointers. */
while (grtmp->gr_mem[nmem++] != NULL) {
nameslen += strlen(grtmp->gr_mem[nmem - 1]) + 1;
}
nameslen += nmem * sizeof(*members);
if (nameslen > end - ((char *) members)) {
goto err_unlock;
}
/* Copy the pointers, including the NULL sentinel. */
for (size_t i = 0; i < nmem; ++i) {
members[i] = grtmp->gr_mem[i];
}
/* Copy the strings (the NULL sentinel doesn't point to one). */
cursor = (char *) &members[nmem];
for (size_t i = 0; i < nmem - 1; ++i) {
cursor = stpcpy(cursor, members[i]) + 1;
}
}
pthread_mutex_unlock(&grent_mutex);
*result = grp;
return 0;
err_unlock:
pthread_mutex_unlock(&grent_mutex);
return ERANGE;
}
/**
* Get group file entry.
*/
int fgetgrent_r(FILE *stream, struct group *grp, char *buf, size_t len,
struct group **result)
{
assert(stream != NULL);
return __fgetgrent_r(stream, grp, buf, len, result);
}
/**
* Get group database entry.
*
* LSB 5.0: LSB-Core-generic/baselib-getgrent-r-1.html
*/
int getgrent_r(struct group *grp, char *buf, size_t len, struct group **result)
{
return __fgetgrent_r(NULL, grp, buf, len, result);
}
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