345 lines
8.0 KiB
C++
345 lines
8.0 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 <limits.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 <stdint.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 "logs.h"
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#include "macros.h"
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#include "subproc.h"
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#include "util.h"
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namespace user {
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static bool setResGid(gid_t gid) {
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LOG_D("setresgid(%d)", gid);
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#if defined(__NR_setresgid32)
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if (syscall(__NR_setresgid32, (uintptr_t)gid, (uintptr_t)gid, (uintptr_t)gid) == -1) {
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PLOG_W("setresgid32(%d)", (int)gid);
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return false;
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}
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#else /* defined(__NR_setresgid32) */
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if (syscall(__NR_setresgid, (uintptr_t)gid, (uintptr_t)gid, (uintptr_t)gid) == -1) {
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PLOG_W("setresgid(%d)", gid);
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return false;
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}
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#endif /* defined(__NR_setresuid32) */
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return true;
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}
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static bool setResUid(uid_t uid) {
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LOG_D("setresuid(%d)", uid);
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#if defined(__NR_setresuid32)
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if (syscall(__NR_setresuid32, (uintptr_t)uid, (uintptr_t)uid, (uintptr_t)uid) == -1) {
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PLOG_W("setresuid32(%d)", (int)uid);
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return false;
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}
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#else /* defined(__NR_setresuid32) */
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if (syscall(__NR_setresuid, (uintptr_t)uid, (uintptr_t)uid, (uintptr_t)uid) == -1) {
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PLOG_W("setresuid(%d)", uid);
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return false;
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}
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#endif /* defined(__NR_setresuid32) */
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return true;
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}
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static bool setGroups(pid_t pid) {
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/*
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* No need to write 'deny' to /proc/pid/setgroups if our euid==0, as writing to
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* uid_map/gid_map 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 (!util::writeBufToFile(fname, denystr, strlen(denystr), O_WRONLY | O_CLOEXEC)) {
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LOG_E("util::writeBufToFile('%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 uidMapSelf(nsjconf_t* nsjconf, pid_t pid) {
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std::string map;
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for (const auto& uid : nsjconf->uids) {
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if (uid.is_newidmap) {
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continue;
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}
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map.append(std::to_string(uid.inside_id));
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map.append(" ");
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map.append(std::to_string(uid.outside_id));
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map.append(" ");
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map.append(std::to_string(uid.count));
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map.append("\n");
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}
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if (map.empty()) {
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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/uid_map", pid);
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LOG_D("Writing '%s' to '%s'", map.c_str(), fname);
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if (!util::writeBufToFile(fname, map.data(), map.length(), O_WRONLY | O_CLOEXEC)) {
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LOG_E("util::writeBufToFile('%s', '%s') failed", fname, map.c_str());
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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 gidMapSelf(nsjconf_t* nsjconf, pid_t pid) {
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std::string map;
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for (const auto& gid : nsjconf->gids) {
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if (gid.is_newidmap) {
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continue;
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}
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map.append(std::to_string(gid.inside_id));
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map.append(" ");
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map.append(std::to_string(gid.outside_id));
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map.append(" ");
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map.append(std::to_string(gid.count));
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map.append("\n");
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}
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if (map.empty()) {
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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/gid_map", pid);
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LOG_D("Writing '%s' to '%s'", map.c_str(), fname);
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if (!util::writeBufToFile(fname, map.data(), map.length(), O_WRONLY | O_CLOEXEC)) {
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LOG_E("util::writeBufToFile('%s', '%s') failed", fname, map.c_str());
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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 gidMapExternal(nsjconf_t* nsjconf, pid_t pid UNUSED) {
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bool use = false;
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std::vector<std::string> argv = {"/usr/bin/newgidmap", std::to_string(pid)};
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for (const auto& gid : nsjconf->gids) {
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if (!gid.is_newidmap) {
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continue;
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}
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use = true;
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argv.push_back(std::to_string(gid.inside_id));
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argv.push_back(std::to_string(gid.outside_id));
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argv.push_back(std::to_string(gid.count));
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}
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if (!use) {
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return true;
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}
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if (subproc::systemExe(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 uidMapExternal(nsjconf_t* nsjconf, pid_t pid UNUSED) {
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bool use = false;
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std::vector<std::string> argv = {"/usr/bin/newuidmap", std::to_string(pid)};
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for (const auto& uid : nsjconf->uids) {
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if (!uid.is_newidmap) {
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continue;
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}
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use = true;
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argv.push_back(std::to_string(uid.inside_id));
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argv.push_back(std::to_string(uid.outside_id));
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argv.push_back(std::to_string(uid.count));
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}
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if (!use) {
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return true;
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}
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if (subproc::systemExe(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 uidGidMap(nsjconf_t* nsjconf, pid_t pid) {
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if (!gidMapSelf(nsjconf, pid)) {
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return false;
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}
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if (!gidMapExternal(nsjconf, pid)) {
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return false;
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}
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if (!uidMapSelf(nsjconf, pid)) {
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return false;
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}
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if (!uidMapExternal(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 initNsFromParent(nsjconf_t* nsjconf, pid_t pid) {
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if (!setGroups(pid)) {
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return false;
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}
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if (!nsjconf->clone_newuser) {
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return true;
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}
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if (!uidGidMap(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 initNsFromChild(nsjconf_t* nsjconf) {
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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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const 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
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* be 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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if (!setResGid(nsjconf->gids[0].inside_id)) {
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PLOG_E("setresgid(%u)", nsjconf->gids[0].inside_id);
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return false;
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}
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if (!setResUid(nsjconf->uids[0].inside_id)) {
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PLOG_E("setresuid(%u)", nsjconf->uids[0].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 parseUid(const std::string& id) {
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if (id.empty()) {
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return getuid();
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}
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struct passwd* pw = getpwnam(id.c_str());
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if (pw != NULL) {
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return pw->pw_uid;
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}
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if (util::isANumber(id.c_str())) {
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return (uid_t)strtoull(id.c_str(), NULL, 0);
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}
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return (uid_t)-1;
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}
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static gid_t parseGid(const std::string& id) {
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if (id.empty()) {
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return getgid();
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}
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struct group* gr = getgrnam(id.c_str());
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if (gr != NULL) {
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return gr->gr_gid;
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}
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if (util::isANumber(id.c_str())) {
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return (gid_t)strtoull(id.c_str(), NULL, 0);
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}
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return (gid_t)-1;
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}
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bool parseId(nsjconf_t* nsjconf, const std::string& i_id, const std::string& o_id, size_t cnt,
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bool is_gid, bool is_newidmap) {
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if (cnt < 1) {
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cnt = 1;
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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 = parseGid(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.c_str());
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return false;
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}
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outside_id = parseGid(o_id);
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if (outside_id == (uid_t)-1) {
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LOG_W("Cannot parse '%s' as GID", o_id.c_str());
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return false;
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}
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} else {
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inside_id = parseUid(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.c_str());
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return false;
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}
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outside_id = parseUid(o_id);
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if (outside_id == (uid_t)-1) {
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LOG_W("Cannot parse '%s' as UID", o_id.c_str());
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return false;
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}
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}
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idmap_t id;
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id.inside_id = inside_id;
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id.outside_id = outside_id;
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id.count = cnt;
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id.is_newidmap = is_newidmap;
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if (is_gid) {
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nsjconf->gids.push_back(id);
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} else {
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nsjconf->uids.push_back(id);
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}
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return true;
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}
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} // namespace user
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