shadow/libmisc/find_new_ids.c

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#include <config.h>
#include <assert.h>
#include <stdio.h>
#include "prototypes.h"
#include "pwio.h"
#include "groupio.h"
#include "getdef.h"
/*
* find_new_uid - Find a new unused UID.
*
* If successful, find_new_uid provides an unused user ID in the
* [UID_MIN:UID_MAX] range.
* This ID should be higher than all the used UID, but if not possible,
* the lowest unused ID in the range will be returned.
*
* Return 0 on success, -1 if no unused UIDs are available.
*/
int find_new_uid (int sys_user, uid_t *uid, uid_t const *preferred_uid)
{
const struct passwd *pwd;
uid_t uid_min, uid_max, user_id;
assert (uid != NULL);
if (sys_user == 0) {
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uid_min = getdef_unum ("UID_MIN", 1000);
uid_max = getdef_unum ("UID_MAX", 60000);
} else {
uid_min = getdef_unum ("SYS_UID_MIN", 1);
uid_max = getdef_unum ("UID_MIN", 1000) - 1;
uid_max = getdef_unum ("SYS_UID_MAX", uid_max);
}
if ( (NULL != preferred_uid)
&& (*preferred_uid >= uid_min)
&& (*preferred_uid <= uid_max)
/* Check if the user exists according to NSS */
&& (getpwuid (*preferred_uid) == NULL)
/* Check also the local database in case of uncommitted
* changes */
&& (pw_locate_uid (*preferred_uid) == NULL)) {
*uid = *preferred_uid;
return 0;
}
user_id = uid_min;
/*
* Search the entire password file,
* looking for the largest unused value.
*
* We check the list of users according to NSS (setpwent/getpwent),
* but we also check the local database (pw_rewind/pw_next) in case
* some users were created but the changes were not committed yet.
*/
setpwent ();
pw_rewind ();
while ( ((pwd = getpwent ()) != NULL)
|| ((pwd = pw_next ()) != NULL)) {
if ((pwd->pw_uid >= user_id) && (pwd->pw_uid <= uid_max)) {
user_id = pwd->pw_uid + 1;
}
}
endpwent ();
/*
* If a user with UID equal to UID_MAX exists, the above algorithm
* will give us UID_MAX+1 even if not unique. Search for the first
* free UID starting with UID_MIN (it's O(n*n) but can be avoided
* by not having users with UID equal to UID_MAX). --marekm
*/
if (user_id == uid_max + 1) {
for (user_id = uid_min; user_id < uid_max; user_id++) {
/* local, no need for xgetpwuid */
if ( (getpwuid (user_id) == NULL)
&& (pw_locate_uid (user_id) == NULL)) {
break;
}
}
if (user_id == uid_max) {
fputs (_("Can't get unique UID (no more available UIDs)\n"), stderr);
return -1;
}
}
*uid = user_id;
return 0;
}
/*
* 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 (int sys_group, gid_t *gid, gid_t const *preferred_gid)
{
const struct group *grp;
gid_t gid_min, gid_max, group_id;
assert (gid != NULL);
if (sys_group == 0) {
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gid_min = getdef_unum ("GID_MIN", 1000);
gid_max = getdef_unum ("GID_MAX", 60000);
} else {
gid_min = getdef_unum ("SYS_GID_MIN", 1);
gid_max = getdef_unum ("GID_MIN", 1000) - 1;
gid_max = getdef_unum ("SYS_GID_MAX", gid_max);
}
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 users according to NSS (setpwent/getpwent),
* but we also check the local database (pw_rewind/pw_next) in case
* some groups were created but the changes were not committed yet.
*/
setgrent ();
gr_rewind ();
while ( ((grp = getgrent ()) != NULL)
|| ((grp = gr_next ()) != NULL)) {
if ((grp->gr_gid >= group_id) && (grp->gr_gid <= gid_max)) {
group_id = grp->gr_gid + 1;
}
}
endgrent ();
/*
* 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 (it's O(n*n) but can be avoided
* by not having users with GID equal to GID_MAX). --marekm
*/
if (group_id == gid_max + 1) {
for (group_id = gid_min; group_id < gid_max; group_id++) {
/* local, no need for xgetgrgid */
if ( (getgrgid (group_id) == NULL)
&& (gr_locate_gid (group_id) == NULL)) {
break;
}
}
if (group_id == gid_max) {
fputs (_("Can't get unique GID (no more available GIDs)\n"), stderr);
return -1;
}
}
*gid = group_id;
return 0;
}