2013-01-11 16:46:38 -06:00
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/*
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* nsenter(1) - command-line interface for setns(2)
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*
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* Copyright (C) 2012-2013 Eric Biederman <ebiederm@xmission.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <dirent.h>
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#include <errno.h>
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#include <getopt.h>
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#include <sched.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include "nls.h"
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#include "c.h"
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#include "closestream.h"
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#ifndef CLONE_NEWSNS
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# define CLONE_NEWNS 0x00020000
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#endif
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#ifndef CLONE_NEWUTS
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# define CLONE_NEWUTS 0x04000000
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#endif
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#ifndef CLONE_NEWIPC
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# define CLONE_NEWIPC 0x08000000
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#endif
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#ifndef CLONE_NEWNET
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# define CLONE_NEWNET 0x40000000
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#endif
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#ifndef CLONE_NEWUSER
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# define CLONE_NEWUSER 0x10000000
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#endif
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#ifndef CLONE_NEWPID
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# define CLONE_NEWPID 0x20000000
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#endif
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#ifndef HAVE_SETNS
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# include <sys/syscall.h>
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static int setns(int fd, int nstype)
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{
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return syscall(SYS_setns, fd, nstype);
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}
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#endif /* HAVE_SETNS */
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static struct namespace_file{
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int nstype;
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char *name;
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int fd;
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} namespace_files[] = {
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2013-01-16 18:34:44 -06:00
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/* Careful the order is significant in this array.
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2013-01-11 16:46:38 -06:00
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*
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* The user namespace comes first, so that it is entered
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* first. This gives an unprivileged user the potential to
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* enter the other namespaces.
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*/
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{ .nstype = CLONE_NEWUSER, .name = "ns/user", .fd = -1 },
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{ .nstype = CLONE_NEWIPC, .name = "ns/ipc", .fd = -1 },
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{ .nstype = CLONE_NEWUTS, .name = "ns/uts", .fd = -1 },
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{ .nstype = CLONE_NEWNET, .name = "ns/net", .fd = -1 },
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{ .nstype = CLONE_NEWPID, .name = "ns/pid", .fd = -1 },
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{ .nstype = CLONE_NEWNS, .name = "ns/mnt", .fd = -1 },
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{}
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};
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static void usage(int status)
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{
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FILE *out = status == EXIT_SUCCESS ? stdout : stderr;
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fputs(USAGE_HEADER, out);
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fprintf(out, _(" %s [options] <program> [args...]\n"),
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program_invocation_short_name);
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fputs(USAGE_OPTIONS, out);
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fputs(_(" -t, --target <pid> target process to get namespaces from\n"
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" -m, --mount [<file>] enter mount namespace\n"
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" -u, --uts [<file>] enter UTS namespace (hostname etc)\n"
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" -i, --ipc [<file>] enter System V IPC namespace\n"
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" -n, --net [<file>] enter network namespace\n"
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" -p, --pid [<file>] enter pid namespace\n"
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" -U, --user [<file>] enter user namespace\n"
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" -e, --exec don't fork before exec'ing <program>\n"
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" -r, --root [<dir>] set the root directory\n"
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" -w, --wd [<dir>] set the working directory\n"), out);
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fputs(USAGE_SEPARATOR, out);
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fputs(USAGE_HELP, out);
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fputs(USAGE_VERSION, out);
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fprintf(out, USAGE_MAN_TAIL("nsenter(1)"));
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exit(status);
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}
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static pid_t namespace_target_pid = 0;
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static int root_fd = -1;
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static int wd_fd = -1;
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static void open_target_fd(int *fd, const char *type, char *path)
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{
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char pathbuf[PATH_MAX];
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if (!path && namespace_target_pid) {
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snprintf(pathbuf, sizeof(pathbuf), "/proc/%u/%s",
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namespace_target_pid, type);
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path = pathbuf;
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}
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if (!path)
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err(EXIT_FAILURE, _("No filename and no target pid supplied for %s"),
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type);
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if (*fd >= 0)
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close(*fd);
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*fd = open(path, O_RDONLY);
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if (*fd < 0)
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err(EXIT_FAILURE, _("open of '%s' failed"), path);
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}
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static void open_namespace_fd(int nstype, char *path)
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{
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struct namespace_file *nsfile;
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for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
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if (nstype != nsfile->nstype)
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continue;
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open_target_fd(&nsfile->fd, nsfile->name, path);
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return;
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}
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/* This should never happen */
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err(EXIT_FAILURE, "Unrecognized namespace type");
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}
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2013-01-16 18:34:17 -06:00
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static void continue_as_child(void)
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{
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pid_t child = fork();
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int status;
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pid_t ret;
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if (child < 0)
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err(EXIT_FAILURE, _("fork failed"));
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/* Only the child returns */
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if (child == 0)
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return;
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for (;;) {
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ret = waitpid(child, &status, WUNTRACED);
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if ((ret == child) && (WIFSTOPPED(status))) {
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/* The child suspended so suspend us as well */
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kill(getpid(), SIGSTOP);
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kill(child, SIGCONT);
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} else {
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break;
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}
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}
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/* Return the child's exit code if possible */
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if (WIFEXITED(status)) {
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exit(WEXITSTATUS(status));
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}
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else if (WIFSIGNALED(status)) {
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kill(getpid(), WTERMSIG(status));
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}
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exit(EXIT_FAILURE);
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}
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2013-01-11 16:46:38 -06:00
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int main(int argc, char *argv[])
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{
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static const struct option longopts[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "version", no_argument, NULL, 'V'},
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{ "target", required_argument, NULL, 't' },
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{ "mount", optional_argument, NULL, 'm' },
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{ "uts", optional_argument, NULL, 'u' },
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{ "ipc", optional_argument, NULL, 'i' },
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{ "net", optional_argument, NULL, 'n' },
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{ "pid", optional_argument, NULL, 'p' },
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{ "user", optional_argument, NULL, 'U' },
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{ "exec", no_argument, NULL, 'e' },
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{ "root", optional_argument, NULL, 'r' },
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{ "wd", optional_argument, NULL, 'w' },
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{ NULL, 0, NULL, 0 }
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};
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struct namespace_file *nsfile;
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int do_fork = 0;
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char *end;
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int c;
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setlocale(LC_MESSAGES, "");
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bindtextdomain(PACKAGE, LOCALEDIR);
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textdomain(PACKAGE);
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atexit(close_stdout);
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while((c = getopt_long(argc, argv, "hVt:m::u::i::n::p::U::er::w::", longopts, NULL)) != -1) {
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switch(c) {
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case 'h':
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usage(EXIT_SUCCESS);
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case 'V':
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printf(UTIL_LINUX_VERSION);
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return EXIT_SUCCESS;
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case 't':
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errno = 0;
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namespace_target_pid = strtoul(optarg, &end, 10);
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if (!*optarg || (*optarg && *end) || errno != 0) {
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err(EXIT_FAILURE,
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_("Pid '%s' is not a valid number"),
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optarg);
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}
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break;
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case 'm':
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open_namespace_fd(CLONE_NEWNS, optarg);
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break;
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case 'u':
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open_namespace_fd(CLONE_NEWUTS, optarg);
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break;
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case 'i':
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open_namespace_fd(CLONE_NEWIPC, optarg);
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break;
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case 'n':
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open_namespace_fd(CLONE_NEWNET, optarg);
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break;
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case 'p':
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do_fork = 1;
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open_namespace_fd(CLONE_NEWPID, optarg);
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break;
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case 'U':
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open_namespace_fd(CLONE_NEWUSER, optarg);
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break;
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case 'e':
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do_fork = 0;
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break;
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case 'r':
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open_target_fd(&root_fd, "root", optarg);
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break;
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case 'w':
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open_target_fd(&wd_fd, "cwd", optarg);
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break;
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default:
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usage(EXIT_FAILURE);
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}
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}
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if(optind >= argc)
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usage(EXIT_FAILURE);
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/*
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* Now that we know which namespaces we want to enter, enter them.
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*/
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for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
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if (nsfile->fd < 0)
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continue;
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if (setns(nsfile->fd, nsfile->nstype))
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err(EXIT_FAILURE, _("setns of '%s' failed"),
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nsfile->name);
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close(nsfile->fd);
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nsfile->fd = -1;
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}
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/* Remember the current working directory if I'm not changing it */
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if (root_fd >= 0 && wd_fd < 0) {
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wd_fd = open(".", O_RDONLY);
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if (wd_fd < 0)
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err(EXIT_FAILURE, _("open of . failed"));
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}
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/* Change the root directory */
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if (root_fd >= 0) {
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if (fchdir(root_fd) < 0)
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err(EXIT_FAILURE, _("fchdir to root_fd failed"));
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if (chroot(".") < 0)
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err(EXIT_FAILURE, _("chroot failed"));
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close(root_fd);
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root_fd = -1;
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}
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/* Change the working directory */
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if (wd_fd >= 0) {
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if (fchdir(wd_fd) < 0)
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err(EXIT_FAILURE, _("fchdir to wd_fd failed"));
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close(wd_fd);
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wd_fd = -1;
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}
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2013-01-16 18:34:17 -06:00
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if (do_fork)
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continue_as_child();
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2013-01-11 16:46:38 -06:00
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execvp(argv[optind], argv + optind);
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err(EXIT_FAILURE, _("exec %s failed"), argv[optind]);
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}
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