373 lines
8.5 KiB
C
373 lines
8.5 KiB
C
/*
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nsjail - CLONE_NEWUSER routines
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-----------------------------------------
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Copyright 2014 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#include "user.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <grp.h>
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#include <linux/securebits.h>
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#include <pwd.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/prctl.h>
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#include <sys/syscall.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "log.h"
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#include "subproc.h"
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#include "util.h"
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static bool userSetGroups(pid_t pid)
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{
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/*
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* No need to write 'deny' to /proc/pid/setgroups if our euid==0, as writing to uid_map/gid_map
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* will succeed anyway
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*/
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if (geteuid() == 0) {
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return true;
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}
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char fname[PATH_MAX];
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snprintf(fname, sizeof(fname), "/proc/%d/setgroups", pid);
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const char *denystr = "deny";
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if (utilWriteBufToFile(fname, denystr, strlen(denystr), O_WRONLY) == false) {
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LOG_E("utilWriteBufToFile('%s', '%s') failed", fname, denystr);
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return false;
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}
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return true;
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}
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static bool userUidMapSelf(struct nsjconf_t *nsjconf, pid_t pid)
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{
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char fname[PATH_MAX];
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snprintf(fname, sizeof(fname), "/proc/%d/uid_map", pid);
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char map[4096] = {[0] = '\0' };
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struct idmap_t *p;
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TAILQ_FOREACH(p, &nsjconf->uids, pointers) {
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if (p->is_newidmap) {
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continue;
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}
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utilSSnPrintf(map, sizeof(map), "%lu %lu %zu\n", (unsigned long)p->inside_id,
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(unsigned long)p->outside_id, p->count);
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}
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if (strlen(map) == 0) {
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return true;
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}
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LOG_D("Writing '%s' to '%s'", map, fname);
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if (utilWriteBufToFile(fname, map, strlen(map), O_WRONLY) == false) {
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LOG_E("utilWriteBufToFile('%s', '%s') failed", fname, map);
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return false;
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}
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return true;
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}
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static bool userGidMapSelf(struct nsjconf_t *nsjconf, pid_t pid)
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{
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char fname[PATH_MAX];
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snprintf(fname, sizeof(fname), "/proc/%d/gid_map", pid);
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char map[4096] = {[0] = '\0' };
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struct idmap_t *p;
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TAILQ_FOREACH(p, &nsjconf->gids, pointers) {
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if (p->is_newidmap) {
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continue;
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}
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utilSSnPrintf(map, sizeof(map), "%lu %lu %zu\n", (unsigned long)p->inside_id,
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(unsigned long)p->outside_id, p->count);
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}
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if (strlen(map) == 0) {
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return true;
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}
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LOG_D("Writing '%s' to '%s'", map, fname);
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if (utilWriteBufToFile(fname, map, strlen(map), O_WRONLY) == false) {
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LOG_E("utilWriteBufToFile('%s', '%s') failed", fname, map);
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return false;
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}
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return true;
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}
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/* Use /usr/bin/newgidmap for writing the gid map */
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static bool userGidMapExternal(struct nsjconf_t *nsjconf, pid_t pid UNUSED)
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{
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static size_t idx = 0;
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const char *argv[1024];
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char parms[1024][256];
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argv[idx++] = "/usr/bin/newgidmap";
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)pid);
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argv[idx] = parms[idx];
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idx++;
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struct idmap_t *p;
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bool use = false;
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TAILQ_FOREACH(p, &nsjconf->gids, pointers) {
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if (p->is_newidmap == false) {
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continue;
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}
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if ((idx + 4) >= ARRAYSIZE(argv)) {
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LOG_W("Too many arguments for '/usr/bin/newgidmap'");
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return false;
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}
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use = true;
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)p->inside_id);
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argv[idx] = parms[idx];
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idx++;
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)p->outside_id);
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argv[idx] = parms[idx];
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idx++;
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snprintf(parms[idx], sizeof(parms[idx]), "%zu", p->count);
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argv[idx] = parms[idx];
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idx++;
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}
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argv[idx] = NULL;
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if (!use) {
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return true;
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}
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if (subprocSystem(argv, environ) != 0) {
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LOG_E("'/usr/bin/newgidmap' failed");
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return false;
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}
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return true;
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}
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/* Use /usr/bin/newuidmap for writing the uid map */
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static bool userUidMapExternal(struct nsjconf_t *nsjconf, pid_t pid UNUSED)
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{
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static size_t idx = 0;
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const char *argv[1024];
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char parms[1024][256];
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argv[idx++] = "/usr/bin/newuidmap";
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)pid);
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argv[idx] = parms[idx];
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idx++;
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bool use = false;
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struct idmap_t *p;
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TAILQ_FOREACH(p, &nsjconf->uids, pointers) {
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if (p->is_newidmap == false) {
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continue;
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}
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if ((idx + 4) >= ARRAYSIZE(argv)) {
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LOG_W("Too many arguments for '/usr/bin/newuidmap'");
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return false;
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}
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use = true;
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)p->inside_id);
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argv[idx] = parms[idx];
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idx++;
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snprintf(parms[idx], sizeof(parms[idx]), "%u", (unsigned)p->outside_id);
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argv[idx] = parms[idx];
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idx++;
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snprintf(parms[idx], sizeof(parms[idx]), "%zu", p->count);
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argv[idx] = parms[idx];
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idx++;
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}
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argv[idx] = NULL;
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if (!use) {
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return true;
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}
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if (subprocSystem(argv, environ) != 0) {
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LOG_E("'/usr/bin/newuidmap' failed");
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return false;
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}
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return true;
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}
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static bool userUidGidMap(struct nsjconf_t *nsjconf, pid_t pid)
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{
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if (!userGidMapSelf(nsjconf, pid)) {
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return false;
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}
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if (!userGidMapExternal(nsjconf, pid)) {
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return false;
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}
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if (!userUidMapSelf(nsjconf, pid)) {
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return false;
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}
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if (!userUidMapExternal(nsjconf, pid)) {
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return false;
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}
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return true;
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}
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bool userInitNsFromParent(struct nsjconf_t * nsjconf, pid_t pid)
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{
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if (userSetGroups(pid) == false) {
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return false;
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}
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if (nsjconf->clone_newuser == false) {
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return true;
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}
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if (userUidGidMap(nsjconf, pid) == false) {
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return false;
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}
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return true;
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}
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bool userInitNsFromChild(struct nsjconf_t * nsjconf)
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{
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/*
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* Best effort because of /proc/self/setgroups
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*/
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LOG_D("setgroups(0, NULL)");
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gid_t *group_list = NULL;
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if (setgroups(0, group_list) == -1) {
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PLOG_D("setgroups(NULL) failed");
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}
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/*
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* Make sure all capabilities are retained after the subsequent setuid/setgid, as they will be
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* needed for privileged operations: mounts, uts change etc.
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*/
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if (prctl(PR_SET_SECUREBITS, SECBIT_KEEP_CAPS | SECBIT_NO_SETUID_FIXUP, 0UL, 0UL, 0UL) ==
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-1) {
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PLOG_E("prctl(PR_SET_SECUREBITS, SECBIT_KEEP_CAPS | SECBIT_NO_SETUID_FIXUP)");
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return false;
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}
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LOG_D("setresgid(%d, %d, %d)", TAILQ_FIRST(&nsjconf->gids)->inside_id,
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TAILQ_FIRST(&nsjconf->gids)->inside_id, TAILQ_FIRST(&nsjconf->gids)->inside_id);
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if (syscall(__NR_setresgid, TAILQ_FIRST(&nsjconf->gids)->inside_id,
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TAILQ_FIRST(&nsjconf->gids)->inside_id, TAILQ_FIRST(&nsjconf->gids)->inside_id)
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== -1) {
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PLOG_E("setresgid(%u)", TAILQ_FIRST(&nsjconf->gids)->inside_id);
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return false;
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}
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LOG_D("setresuid(%d, %d, %d)", TAILQ_FIRST(&nsjconf->uids)->inside_id,
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TAILQ_FIRST(&nsjconf->uids)->inside_id, TAILQ_FIRST(&nsjconf->uids)->inside_id);
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if (syscall(__NR_setresuid, TAILQ_FIRST(&nsjconf->uids)->inside_id,
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TAILQ_FIRST(&nsjconf->uids)->inside_id, TAILQ_FIRST(&nsjconf->uids)->inside_id)
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== -1) {
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PLOG_E("setresuid(%u)", TAILQ_FIRST(&nsjconf->uids)->inside_id);
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return false;
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}
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return true;
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}
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static uid_t cmdParseUid(const char *id)
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{
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if (id == NULL || strlen(id) == 0) {
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return getuid();
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}
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struct passwd *pw = getpwnam(id);
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if (pw != NULL) {
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return pw->pw_uid;
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}
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if (utilIsANumber(id)) {
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return (uid_t) strtoull(id, NULL, 0);
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}
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return -1;
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}
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static gid_t cmdParseGid(const char *id)
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{
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if (id == NULL || strlen(id) == 0) {
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return getgid();
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}
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struct group *gr = getgrnam(id);
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if (gr != NULL) {
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return gr->gr_gid;
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}
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if (utilIsANumber(id)) {
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return (gid_t) strtoull(id, NULL, 0);
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}
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return -1;
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}
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bool userParseId(struct nsjconf_t * nsjconf, const char *i_id, const char *o_id, size_t cnt,
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bool is_gid, bool is_newidmap)
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{
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uid_t inside_id;
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uid_t outside_id;
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if (is_gid) {
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inside_id = cmdParseGid(i_id);
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if (inside_id == (uid_t) - 1) {
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LOG_W("Cannot parse '%s' as GID", i_id);
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return false;
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}
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outside_id = cmdParseGid(o_id);
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if (inside_id == (uid_t) - 1) {
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LOG_W("Cannot parse '%s' as GID", o_id);
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return false;
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}
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} else {
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inside_id = cmdParseUid(i_id);
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if (inside_id == (uid_t) - 1) {
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LOG_W("Cannot parse '%s' as UID", i_id);
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return false;
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}
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outside_id = cmdParseUid(o_id);
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if (inside_id == (uid_t) - 1) {
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LOG_W("Cannot parse '%s' as UID", o_id);
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return false;
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}
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}
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struct idmap_t *p = utilMalloc(sizeof(struct idmap_t));
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p->inside_id = inside_id;
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p->outside_id = outside_id;
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p->count = cnt;
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p->is_newidmap = is_newidmap;
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if (is_gid) {
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TAILQ_INSERT_TAIL(&nsjconf->gids, p, pointers);
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} else {
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TAILQ_INSERT_TAIL(&nsjconf->uids, p, pointers);
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}
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return true;
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}
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