500 lines
14 KiB
C
500 lines
14 KiB
C
/*
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* SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
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* SPDX-FileCopyrightText: 2008 - 2011, Nicolas François
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* SPDX-FileCopyrightText: 2014, Red Hat, Inc.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <config.h>
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#include <assert.h>
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#include <stdio.h>
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#include <errno.h>
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#include "prototypes.h"
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#include "groupio.h"
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#include "getdef.h"
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#include "shadowlog.h"
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/*
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* get_ranges - Get the minimum and maximum ID ranges for the search
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*
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* This function will return the minimum and maximum ranges for IDs
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*
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* 0: The function completed successfully
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* EINVAL: The provided ranges are impossible (such as maximum < minimum)
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*
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* preferred_min: The special-case minimum value for a specifically-
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* requested ID, which may be lower than the standard min_id
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*/
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static int get_ranges (bool sys_group, gid_t *min_id, gid_t *max_id,
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gid_t *preferred_min)
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{
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gid_t gid_def_max = 0;
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if (sys_group) {
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/* System groups */
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/* A requested ID is allowed to be below the autoselect range */
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*preferred_min = (gid_t) 1;
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/* Get the minimum ID range from login.defs or default to 101 */
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*min_id = getdef_ulong ("SYS_GID_MIN", 101UL);
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/*
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* If SYS_GID_MAX is unspecified, we should assume it to be one
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* less than the GID_MIN (which is reserved for non-system accounts)
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*/
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gid_def_max = getdef_ulong ("GID_MIN", 1000UL) - 1;
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*max_id = getdef_ulong ("SYS_GID_MAX", gid_def_max);
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/* Check that the ranges make sense */
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if (*max_id < *min_id) {
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(void) fprintf (log_get_logfd(),
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_("%s: Invalid configuration: SYS_GID_MIN (%lu), "
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"GID_MIN (%lu), SYS_GID_MAX (%lu)\n"),
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log_get_progname(), (unsigned long) *min_id,
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getdef_ulong ("GID_MIN", 1000UL),
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(unsigned long) *max_id);
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return EINVAL;
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}
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/*
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* Zero is reserved for root and the allocation algorithm does not
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* work right with it.
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*/
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if (*min_id == 0) {
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*min_id = (gid_t) 1;
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}
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} else {
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/* Non-system groups */
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/* Get the values from login.defs or use reasonable defaults */
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*min_id = getdef_ulong ("GID_MIN", 1000UL);
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*max_id = getdef_ulong ("GID_MAX", 60000UL);
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/*
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* The preferred minimum should match the standard ID minimum
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* for non-system groups.
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*/
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*preferred_min = *min_id;
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/* Check that the ranges make sense */
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if (*max_id < *min_id) {
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(void) fprintf (log_get_logfd(),
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_("%s: Invalid configuration: GID_MIN (%lu), "
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"GID_MAX (%lu)\n"),
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log_get_progname(), (unsigned long) *min_id,
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(unsigned long) *max_id);
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return EINVAL;
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}
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}
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return 0;
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}
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/*
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* check_gid - See if the requested GID is available
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*
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* On success, return 0
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* If the ID is in use, return EEXIST
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* If the ID might clash with -1, return EINVAL
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* If the ID is outside the range, return ERANGE
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* In other cases, return errno from getgrgid()
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*/
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static int check_gid (const gid_t gid,
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const gid_t gid_min,
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const gid_t gid_max,
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const bool *used_gids)
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{
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/* First test that the preferred ID is in the range */
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if (gid < gid_min || gid > gid_max) {
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return ERANGE;
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}
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/* Check for compatibility with 16b and 32b gid_t error codes */
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if (gid == UINT16_MAX || gid == UINT32_MAX) {
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return EINVAL;
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}
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/*
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* Check whether we already detected this GID
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* using the gr_next() loop
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*/
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if (used_gids != NULL && used_gids[gid]) {
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return EEXIST;
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}
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/* Check if the GID exists according to NSS */
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errno = 0;
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if (prefix_getgrgid (gid) != NULL) {
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return EEXIST;
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} else {
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/* getgrgid() was NULL
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* we have to ignore errors as temporary
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* failures of remote user identity services
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* would completely block user/group creation
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*/
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}
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/* If we've made it here, the GID must be available */
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return 0;
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}
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/*
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* find_new_gid - Find a new unused GID.
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*
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* If successful, find_new_gid provides an unused group ID in the
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* [GID_MIN:GID_MAX] range.
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* This ID should be higher than all the used GID, but if not possible,
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* the lowest unused ID in the range will be returned.
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*
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* Return 0 on success, -1 if no unused GIDs are available.
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*/
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int find_new_gid (bool sys_group,
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gid_t *gid,
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/*@null@*/gid_t const *preferred_gid)
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{
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bool *used_gids;
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const struct group *grp;
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gid_t gid_min, gid_max, preferred_min;
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gid_t id;
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gid_t lowest_found, highest_found;
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int result;
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int nospam = 0;
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assert(gid != NULL);
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/*
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* First, figure out what ID range is appropriate for
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* automatic assignment
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*/
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result = get_ranges (sys_group, &gid_min, &gid_max, &preferred_min);
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if (result == EINVAL) {
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return -1;
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}
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/* Check if the preferred GID is available */
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if (preferred_gid) {
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result = check_gid (*preferred_gid, preferred_min, gid_max, NULL);
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if (result == 0) {
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/*
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* Make sure the GID isn't queued for use already
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*/
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if (gr_locate_gid (*preferred_gid) == NULL) {
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*gid = *preferred_gid;
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return 0;
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}
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/*
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* gr_locate_gid() found the GID in an as-yet uncommitted
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* entry. We'll proceed below and auto-set a GID.
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*/
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} else if (result == EEXIST || result == ERANGE || result == EINVAL) {
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/*
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* Continue on below. At this time, we won't
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* treat these three cases differently.
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*/
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} else {
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/*
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* An unexpected error occurred. We should report
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* this and fail the group creation.
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* This differs from the automatic creation
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* behavior below, since if a specific GID was
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* requested and generated an error, the user is
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* more likely to want to stop and address the
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* issue.
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*/
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fprintf (log_get_logfd(),
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_("%s: Encountered error attempting to use "
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"preferred GID: %s\n"),
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log_get_progname(), strerror (result));
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return -1;
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}
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}
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/*
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* Search the entire group file,
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* looking for the next unused value.
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*
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* We first check the local database with gr_rewind/gr_next to find
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* all local values that are in use.
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*
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* We then compare the next free value to all databases (local and
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* remote) and iterate until we find a free one. If there are free
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* values beyond the lowest (system groups) or highest (non-system
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* groups), we will prefer those and avoid potentially reclaiming a
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* deleted group (which can be a security issue, since it may grant
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* access to files belonging to that former group).
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*
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* If there are no GIDs available at the end of the search, we will
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* have no choice but to iterate through the range looking for gaps.
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*
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*/
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/* Create an array to hold all of the discovered GIDs */
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used_gids = calloc (gid_max + 1, sizeof (bool));
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if (NULL == used_gids) {
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fprintf (log_get_logfd(),
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_("%s: failed to allocate memory: %s\n"),
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log_get_progname(), strerror (errno));
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return -1;
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}
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/* First look for the lowest and highest value in the local database */
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(void) gr_rewind ();
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highest_found = gid_min;
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lowest_found = gid_max;
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while ((grp = gr_next ()) != NULL) {
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/*
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* Does this entry have a lower GID than the lowest we've found
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* so far?
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*/
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if ((grp->gr_gid <= lowest_found) && (grp->gr_gid >= gid_min)) {
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lowest_found = grp->gr_gid - 1;
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}
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/*
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* Does this entry have a higher GID than the highest we've found
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* so far?
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*/
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if ((grp->gr_gid >= highest_found) && (grp->gr_gid <= gid_max)) {
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highest_found = grp->gr_gid + 1;
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}
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/* create index of used GIDs */
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if (grp->gr_gid >= gid_min
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&& grp->gr_gid <= gid_max) {
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used_gids[grp->gr_gid] = true;
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}
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}
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if (sys_group) {
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/*
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* For system groups, we want to start from the
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* top of the range and work downwards.
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*/
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/*
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* At the conclusion of the gr_next() search, we will either
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* have a presumed-free GID or we will be at GID_MIN - 1.
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*/
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if (lowest_found < gid_min) {
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/*
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* In this case, a GID is in use at GID_MIN.
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*
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* We will reset the search to GID_MAX and proceed down
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* through all the GIDs (skipping those we detected with
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* used_gids) for a free one. It is a known issue that
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* this may result in reusing a previously-deleted GID,
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* so administrators should be instructed to use this
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* auto-detection with care (and prefer to assign GIDs
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* explicitly).
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*/
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lowest_found = gid_max;
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}
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/* Search through all of the IDs in the range */
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for (id = lowest_found; id >= gid_min; id--) {
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result = check_gid (id, gid_min, gid_max, used_gids);
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if (result == 0) {
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/* This GID is available. Return it. */
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*gid = id;
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free (used_gids);
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return 0;
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} else if (result == EEXIST || result == EINVAL) {
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/*
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* This GID is in use or unusable, we'll
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* continue to the next.
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*/
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (log_get_logfd(),
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_("%s: Can't get unique system GID (%s). "
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"Suppressing additional messages.\n"),
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log_get_progname(), strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available GIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later GID
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* will work properly.
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*/
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}
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}
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/*
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* If we get all the way through the loop, try again from GID_MAX,
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* unless that was where we previously started. (NOTE: the worst-case
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* scenario here is that we will run through (GID_MAX - GID_MIN - 1)
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* cycles *again* if we fall into this case with lowest_found as
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* GID_MAX - 1, all groups in the range in use and maintained by
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* network services such as LDAP.)
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*/
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if (lowest_found != gid_max) {
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for (id = gid_max; id >= gid_min; id--) {
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result = check_gid (id, gid_min, gid_max, used_gids);
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if (result == 0) {
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/* This GID is available. Return it. */
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*gid = id;
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free (used_gids);
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return 0;
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} else if (result == EEXIST || result == EINVAL) {
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/*
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* This GID is in use or unusable, we'll
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* continue to the next.
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*/
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (log_get_logfd(),
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_("%s: Can't get unique system GID (%s). "
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"Suppressing additional messages.\n"),
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log_get_progname(), strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available GIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later GID
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* will work properly.
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*/
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}
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}
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}
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} else { /* !sys_group */
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/*
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* For non-system groups, we want to start from the
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* bottom of the range and work upwards.
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*/
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/*
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* At the conclusion of the gr_next() search, we will either
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* have a presumed-free GID or we will be at GID_MAX + 1.
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*/
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if (highest_found > gid_max) {
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/*
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* In this case, a GID is in use at GID_MAX.
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*
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* We will reset the search to GID_MIN and proceed up
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* through all the GIDs (skipping those we detected with
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* used_gids) for a free one. It is a known issue that
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* this may result in reusing a previously-deleted GID,
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* so administrators should be instructed to use this
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* auto-detection with care (and prefer to assign GIDs
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* explicitly).
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*/
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highest_found = gid_min;
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}
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/* Search through all of the IDs in the range */
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for (id = highest_found; id <= gid_max; id++) {
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result = check_gid (id, gid_min, gid_max, used_gids);
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if (result == 0) {
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/* This GID is available. Return it. */
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*gid = id;
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free (used_gids);
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return 0;
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} else if (result == EEXIST || result == EINVAL) {
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/*
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* This GID is in use or unusable, we'll
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* continue to the next.
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*/
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (log_get_logfd(),
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_("%s: Can't get unique GID (%s). "
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"Suppressing additional messages.\n"),
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log_get_progname(), strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available GIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later GID
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* will work properly.
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*/
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}
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}
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/*
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* If we get all the way through the loop, try again from GID_MIN,
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* unless that was where we previously started. (NOTE: the worst-case
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* scenario here is that we will run through (GID_MAX - GID_MIN - 1)
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* cycles *again* if we fall into this case with highest_found as
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* GID_MIN + 1, all groups in the range in use and maintained by
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* network services such as LDAP.)
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*/
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if (highest_found != gid_min) {
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for (id = gid_min; id <= gid_max; id++) {
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result = check_gid (id, gid_min, gid_max, used_gids);
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if (result == 0) {
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/* This GID is available. Return it. */
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*gid = id;
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free (used_gids);
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return 0;
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} else if (result == EEXIST || result == EINVAL) {
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/*
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* This GID is in use or unusable, we'll
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* continue to the next.
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*/
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (log_get_logfd(),
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_("%s: Can't get unique GID (%s). "
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"Suppressing additional messages.\n"),
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log_get_progname(), strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available GIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later GID
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* will work properly.
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*/
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}
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}
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}
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}
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/* The code reached here and found no available IDs in the range */
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fprintf (log_get_logfd(),
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_("%s: Can't get unique GID (no more available GIDs)\n"),
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log_get_progname());
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SYSLOG ((LOG_WARN, "no more available GIDs on the system"));
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free (used_gids);
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return -1;
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}
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