shadow/libmisc/find_new_gid.c

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/*
* Copyright (c) 1991 - 1994, Julianne Frances Haugh
* Copyright (c) 2008 , Nicolas François
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the copyright holders or contributors may not be used to
* endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <config.h>
#include <assert.h>
#include <stdio.h>
#include "prototypes.h"
#include "groupio.h"
#include "getdef.h"
/*
* find_new_gid - Find a new unused GID.
*
* If successful, find_new_gid provides an unused group ID in the
* [GID_MIN:GID_MAX] range.
* This ID should be higher than all the used GID, but if not possible,
* the lowest unused ID in the range will be returned.
*
* Return 0 on success, -1 if no unused GIDs are available.
*/
int find_new_gid (bool sys_group, gid_t *gid, gid_t const *preferred_gid)
{
const struct group *grp;
gid_t gid_min, gid_max, group_id;
char *used_gids;
assert (gid != NULL);
if (!sys_group) {
gid_min = getdef_ulong ("GID_MIN", 1000L);
gid_max = getdef_ulong ("GID_MAX", 60000L);
} else {
gid_min = getdef_ulong ("SYS_GID_MIN", 1L);
gid_max = getdef_ulong ("GID_MIN", 1000L) - 1;
gid_max = getdef_ulong ("SYS_GID_MAX", (unsigned long) gid_max);
}
used_gids = alloca (sizeof (char) * gid_max +1);
memset (used_gids, 0, sizeof (char) * gid_max + 1);
if ( (NULL != preferred_gid)
&& (*preferred_gid >= gid_min)
&& (*preferred_gid <= gid_max)
/* Check if the user exists according to NSS */
&& (getgrgid (*preferred_gid) == NULL)
/* Check also the local database in case of uncommitted
* changes */
&& (gr_locate_gid (*preferred_gid) == NULL)) {
*gid = *preferred_gid;
return 0;
}
group_id = gid_min;
/*
* Search the entire group file,
* looking for the largest unused value.
*
* We check the list of groups according to NSS (setgrent/getgrent),
* but we also check the local database (gr_rewind/gr_next) in case
* some groups were created but the changes were not committed yet.
*/
setgrent ();
while ((grp = getgrent ()) != NULL) {
if ((grp->gr_gid >= group_id) && (grp->gr_gid <= gid_max)) {
group_id = grp->gr_gid + 1;
}
/* create index of used GIDs */
if (grp->gr_gid <= gid_max) {
used_gids[grp->gr_gid] = 1;
}
}
endgrent ();
gr_rewind ();
while ((grp = gr_next ()) != NULL) {
if ((grp->gr_gid >= group_id) && (grp->gr_gid <= gid_max)) {
group_id = grp->gr_gid + 1;
}
/* create index of used GIDs */
if (grp->gr_gid <= gid_max) {
used_gids[grp->gr_gid] = 1;
}
}
/* find free system account in reverse order */
if (sys_group) {
for (group_id = gid_max; group_id >= gid_min; group_id--) {
if (0 == used_gids[group_id]) {
break;
}
}
if ( group_id < gid_min ) {
fprintf (stderr,
_("%s: Can't get unique GID (no more available GIDs)\n"),
Prog);
SYSLOG ((LOG_WARN,
"no more available GID on the system"));
return -1;
}
}
/*
* If a group with GID equal to GID_MAX exists, the above algorithm
* will give us GID_MAX+1 even if not unique. Search for the first
* free GID starting with GID_MIN.
*/
if (group_id == gid_max + 1) {
for (group_id = gid_min; group_id < gid_max; group_id++) {
if (0 == used_gids[group_id]) {
break;
}
}
if (group_id == gid_max) {
fprintf (stderr, _("%s: Can't get unique GID (no more available GIDs)\n"), Prog);
SYSLOG ((LOG_WARN, "no more available GID on the system"));
return -1;
}
}
*gid = group_id;
return 0;
}