static int
xgetgroups (const char *username, int *n_groups, GETGROUPS_T **groups)
{
int max_n_groups;
int ng;
GETGROUPS_T *g;
int fail = 0;
if (username == 0)
max_n_groups = getgroups (0, NULL);
else
max_n_groups = getugroups (0, NULL, username);
/* Add 1 just in case max_n_groups is zero. */
g = (GETGROUPS_T *) xmalloc (max_n_groups * sizeof (GETGROUPS_T) + 1);
if (username == 0)
ng = getgroups (max_n_groups, g);
else
ng = getugroups (max_n_groups, g, username);
if (ng < 0)
{
error (0, errno, _("cannot get supplemental group list"));
++fail;
free (groups);
}
if (!fail)
{
*n_groups = ng;
*groups = g;
}
return fail;
}
int
mgetgroups (const char *username, gid_t gid, GETGROUPS_T **groups)
{
int max_n_groups;
int ng;
GETGROUPS_T *g;
max_n_groups = (username
? getugroups (0, NULL, username, gid)
: getgroups (0, NULL));
/* If we failed to count groups with NULL for a buffer,
try again with a non-NULL one, just in case. */
if (max_n_groups < 0)
max_n_groups = 5;
if (xalloc_oversized (max_n_groups, sizeof *g))
{
errno = ENOMEM;
return -1;
}
g = malloc (max_n_groups * sizeof *g);
if (g == NULL)
return -1;
ng = (username
? getugroups (max_n_groups, g, username, gid)
: getgroups (max_n_groups, g));
if (ng < 0)
{
int saved_errno = errno;
free (g);
errno = saved_errno;
return -1;
}
*groups = g;
return ng;
}
int
mgetgroups (char const *username, gid_t gid, gid_t **groups)
{
int max_n_groups;
int ng;
gid_t *g;
#if HAVE_GETGROUPLIST
/* We prefer to use getgrouplist if available, because it has better
performance characteristics.
In glibc 2.3.2, getgrouplist is buggy. If you pass a zero as the
length of the output buffer, getgrouplist will still write to the
buffer. Contrary to what some versions of the getgrouplist
manpage say, this doesn't happen with nonzero buffer sizes.
Therefore our usage here just avoids a zero sized buffer. */
if (username)
{
enum { N_GROUPS_INIT = 10 };
max_n_groups = N_GROUPS_INIT;
g = realloc_groupbuf (NULL, max_n_groups);
if (g == NULL)
return -1;
while (1)
{
gid_t *h;
int last_n_groups = max_n_groups;
/* getgrouplist updates max_n_groups to num required. */
ng = getgrouplist (username, gid, g, &max_n_groups);
/* Some systems (like Darwin) have a bug where they
never increase max_n_groups. */
if (ng < 0 && last_n_groups == max_n_groups)
max_n_groups *= 2;
if ((h = realloc_groupbuf (g, max_n_groups)) == NULL)
{
int saved_errno = errno;
free (g);
errno = saved_errno;
return -1;
}
g = h;
if (0 <= ng)
{
*groups = g;
/* On success some systems just return 0 from getgrouplist,
so return max_n_groups rather than ng. */
return max_n_groups;
}
}
}
/* else no username, so fall through and use getgroups. */
#endif
max_n_groups = (username
? getugroups (0, NULL, username, gid)
: getgroups (0, NULL));
/* If we failed to count groups because there is no supplemental
group support, then return an array containing just GID.
Otherwise, we fail for the same reason. */
if (max_n_groups < 0)
{
if (errno == ENOSYS && (g = realloc_groupbuf (NULL, 1)))
{
*groups = g;
*g = gid;
return gid != (gid_t) -1;
}
return -1;
}
if (max_n_groups == 0 || (!username && gid != (gid_t) -1))
max_n_groups++;
g = realloc_groupbuf (NULL, max_n_groups);
if (g == NULL)
return -1;
ng = (username
? getugroups (max_n_groups, g, username, gid)
: getgroups (max_n_groups - (gid != (gid_t) -1),
g + (gid != (gid_t) -1)));
if (ng < 0)
{
/* Failure is unexpected, but handle it anyway. */
int saved_errno = errno;
free (g);
errno = saved_errno;
return -1;
}
if (!username && gid != (gid_t) -1)
{
*g = gid;
ng++;
}
*groups = g;
/* Reduce the number of duplicates. On some systems, getgroups
returns the effective gid twice: once as the first element, and
once in its position within the supplementary groups. On other
systems, getgroups does not return the effective gid at all,
which is why we provide a GID argument. Meanwhile, the GID
argument, if provided, is typically any member of the
supplementary groups, and not necessarily the effective gid. So,
the most likely duplicates are the first element with an
arbitrary other element, or pair-wise duplication between the
first and second elements returned by getgroups. It is possible
that this O(n) pass will not remove all duplicates, but it is not
worth the effort to slow down to an O(n log n) algorithm that
sorts the array in place, nor the extra memory needed for
duplicate removal via an O(n) hash-table. Hence, this function
is only documented as guaranteeing no pair-wise duplicates,
rather than returning the minimal set. */
if (1 < ng)
{
gid_t first = *g;
gid_t *next;
gid_t *groups_end = g + ng;
for (next = g + 1; next < groups_end; next++)
{
if (*next == first || *next == *g)
ng--;
else
*++g = *next;
}
}
return ng;
}
