1 files changed, 286 insertions, 0 deletions
diff --git a/sys-utils/nsenter.c b/sys-utils/nsenter.c
new file mode 100644
index 000000000..f9c663648
--- /dev/null
+++ b/sys-utils/nsenter.c
@@ -0,0 +1,286 @@
+/*
+ * nsenter(1) - command-line interface for setns(2)
+ *
+ * Copyright (C) 2012-2013 Eric Biederman <ebiederm@xmission.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <dirent.h>
+#include <errno.h>
+#include <getopt.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "nls.h"
+#include "c.h"
+#include "closestream.h"
+
+#ifndef CLONE_NEWSNS
+# define CLONE_NEWNS 0x00020000
+#endif
+#ifndef CLONE_NEWUTS
+# define CLONE_NEWUTS 0x04000000
+#endif
+#ifndef CLONE_NEWIPC
+# define CLONE_NEWIPC 0x08000000
+#endif
+#ifndef CLONE_NEWNET
+# define CLONE_NEWNET 0x40000000
+#endif
+#ifndef CLONE_NEWUSER
+# define CLONE_NEWUSER 0x10000000
+#endif
+#ifndef CLONE_NEWPID
+# define CLONE_NEWPID 0x20000000
+#endif
+
+#ifndef HAVE_SETNS
+# include <sys/syscall.h>
+static int setns(int fd, int nstype)
+{
+	return syscall(SYS_setns, fd, nstype);
+}
+#endif /* HAVE_SETNS */
+
+static struct namespace_file{
+	int nstype;
+	char *name;
+	int fd;
+} namespace_files[] = {
+	/* Careful the order is signifcant in this array.
+	 *
+	 * The user namespace comes first, so that it is entered
+	 * first.  This gives an unprivileged user the potential to
+	 * enter the other namespaces.
+	 */
+	{ .nstype = CLONE_NEWUSER, .name = "ns/user", .fd = -1 },
+	{ .nstype = CLONE_NEWIPC,  .name = "ns/ipc",  .fd = -1 },
+	{ .nstype = CLONE_NEWUTS,  .name = "ns/uts",  .fd = -1 },
+	{ .nstype = CLONE_NEWNET,  .name = "ns/net",  .fd = -1 },
+	{ .nstype = CLONE_NEWPID,  .name = "ns/pid",  .fd = -1 },
+	{ .nstype = CLONE_NEWNS,   .name = "ns/mnt",  .fd = -1 },
+	{}
+};
+
+static void usage(int status)
+{
+	FILE *out = status == EXIT_SUCCESS ? stdout : stderr;
+
+	fputs(USAGE_HEADER, out);
+	fprintf(out, _(" %s [options] <program> [args...]\n"),
+		program_invocation_short_name);
+
+	fputs(USAGE_OPTIONS, out);
+	fputs(_(" -t, --target <pid>   target process to get namespaces from\n"
+		" -m, --mount [<file>] enter mount namespace\n"
+		" -u, --uts   [<file>] enter UTS namespace (hostname etc)\n"
+		" -i, --ipc   [<file>] enter System V IPC namespace\n"
+		" -n, --net   [<file>] enter network namespace\n"
+		" -p, --pid   [<file>] enter pid namespace\n"
+		" -U, --user  [<file>] enter user namespace\n"
+		" -e, --exec           don't fork before exec'ing <program>\n"
+		" -r, --root  [<dir>]  set the root directory\n"
+		" -w, --wd    [<dir>]  set the working directory\n"), out);
+	fputs(USAGE_SEPARATOR, out);
+	fputs(USAGE_HELP, out);
+	fputs(USAGE_VERSION, out);
+	fprintf(out, USAGE_MAN_TAIL("nsenter(1)"));
+
+	exit(status);
+}
+
+static pid_t namespace_target_pid = 0;
+static int root_fd = -1;
+static int wd_fd = -1;
+
+static void open_target_fd(int *fd, const char *type, char *path)
+{
+	char pathbuf[PATH_MAX];
+
+	if (!path && namespace_target_pid) {
+		snprintf(pathbuf, sizeof(pathbuf), "/proc/%u/%s",
+			namespace_target_pid, type);
+		path = pathbuf;
+	}
+	if (!path)
+		err(EXIT_FAILURE, _("No filename and no target pid supplied for %s"),
+		    type);
+
+	if (*fd >= 0)
+		close(*fd);
+
+	*fd = open(path, O_RDONLY);
+	if (*fd < 0)
+		err(EXIT_FAILURE, _("open of '%s' failed"), path);
+}
+
+static void open_namespace_fd(int nstype, char *path)
+{
+	struct namespace_file *nsfile;
+
+	for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
+		if (nstype != nsfile->nstype)
+			continue;
+
+		open_target_fd(&nsfile->fd, nsfile->name, path);
+		return;
+	}
+	/* This should never happen */
+	err(EXIT_FAILURE, "Unrecognized namespace type");
+}
+
+int main(int argc, char *argv[])
+{
+	static const struct option longopts[] = {
+		{ "help", no_argument, NULL, 'h' },
+		{ "version", no_argument, NULL, 'V'},
+		{ "target", required_argument, NULL, 't' },
+		{ "mount", optional_argument, NULL, 'm' },
+		{ "uts", optional_argument, NULL, 'u' },
+		{ "ipc", optional_argument, NULL, 'i' },
+		{ "net", optional_argument, NULL, 'n' },
+		{ "pid", optional_argument, NULL, 'p' },
+		{ "user", optional_argument, NULL, 'U' },
+		{ "exec", no_argument, NULL, 'e' },
+		{ "root", optional_argument, NULL, 'r' },
+		{ "wd", optional_argument, NULL, 'w' },
+		{ NULL, 0, NULL, 0 }
+	};
+
+	struct namespace_file *nsfile;
+	int do_fork = 0;
+	char *end;
+	int c;
+
+	setlocale(LC_MESSAGES, "");
+	bindtextdomain(PACKAGE, LOCALEDIR);
+	textdomain(PACKAGE);
+	atexit(close_stdout);
+
+	while((c = getopt_long(argc, argv, "hVt:m::u::i::n::p::U::er::w::", longopts, NULL)) != -1) {
+		switch(c) {
+		case 'h':
+			usage(EXIT_SUCCESS);
+		case 'V':
+			printf(UTIL_LINUX_VERSION);
+			return EXIT_SUCCESS;
+		case 't':
+			errno = 0;
+			namespace_target_pid = strtoul(optarg, &end, 10);
+			if (!*optarg || (*optarg && *end) || errno != 0) {
+				err(EXIT_FAILURE,
+				    _("Pid '%s' is not a valid number"),
+				    optarg);
+			}
+			break;
+		case 'm':
+			open_namespace_fd(CLONE_NEWNS, optarg);
+			break;
+		case 'u':
+			open_namespace_fd(CLONE_NEWUTS, optarg);
+			break;
+		case 'i':
+			open_namespace_fd(CLONE_NEWIPC, optarg);
+			break;
+		case 'n':
+			open_namespace_fd(CLONE_NEWNET, optarg);
+			break;
+		case 'p':
+			do_fork = 1;
+			open_namespace_fd(CLONE_NEWPID, optarg);
+			break;
+		case 'U':
+			open_namespace_fd(CLONE_NEWUSER, optarg);
+			break;
+		case 'e':
+			do_fork = 0;
+			break;
+		case 'r':
+			open_target_fd(&root_fd, "root", optarg);
+			break;
+		case 'w':
+			open_target_fd(&wd_fd, "cwd", optarg);
+			break;
+		default:
+			usage(EXIT_FAILURE);
+		}
+	}
+
+	if(optind >= argc)
+		usage(EXIT_FAILURE);
+
+	/*
+	 * Now that we know which namespaces we want to enter, enter them.
+	 */
+	for (nsfile = namespace_files; nsfile->nstype; nsfile++) {
+		if (nsfile->fd < 0)
+			continue;
+		if (setns(nsfile->fd, nsfile->nstype))
+			err(EXIT_FAILURE, _("setns of '%s' failed"),
+			    nsfile->name);
+		close(nsfile->fd);
+		nsfile->fd = -1;
+	}
+
+	/* Remember the current working directory if I'm not changing it */
+	if (root_fd >= 0 && wd_fd < 0) {
+		wd_fd = open(".", O_RDONLY);
+		if (wd_fd < 0)
+			err(EXIT_FAILURE, _("open of . failed"));
+	}
+
+	/* Change the root directory */
+	if (root_fd >= 0) {
+		if (fchdir(root_fd) < 0)
+			err(EXIT_FAILURE, _("fchdir to root_fd failed"));
+
+		if (chroot(".") < 0)
+			err(EXIT_FAILURE, _("chroot failed"));
+
+		close(root_fd);
+		root_fd = -1;
+	}
+
+	/* Change the working directory */
+	if (wd_fd >= 0) {
+		if (fchdir(wd_fd) < 0)
+			err(EXIT_FAILURE, _("fchdir to wd_fd failed"));
+
+		close(wd_fd);
+		wd_fd = -1;
+	}
+
+	if (do_fork) {
+		pid_t child = fork();
+		if (child < 0)
+			err(EXIT_FAILURE, _("fork failed"));
+		if (child != 0) {
+			int status;
+			if ((waitpid(child, &status, 0) == child) &&
+			     WIFEXITED(status)) {
+				exit(WEXITSTATUS(status));
+			}
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	execvp(argv[optind], argv + optind);
+
+	err(EXIT_FAILURE, _("exec %s failed"), argv[optind]);
+}