[lttng-tools.git] / src / common / runas.c

/*
 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
 *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2 only,
 * as published by the Free Software Foundation.
 *
 * 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.
 */

#define _GNU_SOURCE
#define _LGPL_SOURCE
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sched.h>
#include <sys/signal.h>

#include <common/common.h>
#include <common/utils.h>
#include <common/compat/mman.h>
#include <common/compat/clone.h>
#include <common/compat/getenv.h>

#include "runas.h"

#define RUNAS_CHILD_STACK_SIZE	10485760

#ifndef MAP_STACK
#define MAP_STACK		0
#endif

#ifdef __FreeBSD__
/* FreeBSD MAP_STACK always return -ENOMEM */
#define LTTNG_MAP_STACK		0
#else
#define LTTNG_MAP_STACK		MAP_STACK
#endif

#ifndef MAP_GROWSDOWN
#define MAP_GROWSDOWN		0
#endif

#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS		MAP_ANON
#endif

struct run_as_data {
	int (*cmd)(void *data);
	void *data;
	uid_t uid;
	gid_t gid;
	int retval_pipe;
};

struct run_as_mkdir_data {
	const char *path;
	mode_t mode;
};

struct run_as_open_data {
	const char *path;
	int flags;
	mode_t mode;
};

struct run_as_unlink_data {
	const char *path;
};

struct run_as_recursive_rmdir_data {
	const char *path;
};

#ifdef VALGRIND
static
int use_clone(void)
{
	return 0;
}
#else
static
int use_clone(void)
{
	return !lttng_secure_getenv("LTTNG_DEBUG_NOCLONE");
}
#endif

/*
 * Create recursively directory using the FULL path.
 */
static
int _mkdir_recursive(void *_data)
{
	struct run_as_mkdir_data *data = _data;
	const char *path;
	mode_t mode;

	path = data->path;
	mode = data->mode;

	return utils_mkdir_recursive(path, mode);
}

static
int _mkdir(void *_data)
{
	int ret;
	struct run_as_mkdir_data *data = _data;

	ret = mkdir(data->path, data->mode);
	if (ret < 0) {
		ret = -errno;
	}

	return ret;
}

static
int _open(void *_data)
{
	struct run_as_open_data *data = _data;
	return open(data->path, data->flags, data->mode);
}

static
int _unlink(void *_data)
{
	int ret;
	struct run_as_unlink_data *data = _data;

	ret = unlink(data->path);
	if (ret < 0) {
		ret = -errno;
	}

	return ret;
}

static
int _recursive_rmdir(void *_data)
{
	int ret;
	struct run_as_recursive_rmdir_data *data = _data;

	ret = utils_recursive_rmdir(data->path);
	if (ret < 0) {
		ret = -errno;
	}

	return ret;
}

static
int child_run_as(void *_data)
{
	int ret;
	struct run_as_data *data = _data;
	ssize_t writelen;
	int sendret;

	/*
	 * Child: it is safe to drop egid and euid while sharing the
	 * file descriptors with the parent process, since we do not
	 * drop "uid": therefore, the user we are dropping egid/euid to
	 * cannot attach to this process with, e.g. ptrace, nor map this
	 * process memory.
	 */
	if (data->gid != getegid()) {
		ret = setegid(data->gid);
		if (ret < 0) {
			PERROR("setegid");
			sendret = -1;
			goto write_return;
		}
	}
	if (data->uid != geteuid()) {
		ret = seteuid(data->uid);
		if (ret < 0) {
			PERROR("seteuid");
			sendret = -1;
			goto write_return;
		}
	}
	/*
	 * Also set umask to 0 for mkdir executable bit.
	 */
	umask(0);
	sendret = (*data->cmd)(data->data);

write_return:
	/* send back return value */
	writelen = lttng_write(data->retval_pipe, &sendret, sizeof(sendret));
	if (writelen < sizeof(sendret)) {
		PERROR("lttng_write error");
		return EXIT_FAILURE;
	} else {
		return EXIT_SUCCESS;
	}
}

static
int run_as_clone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
{
	struct run_as_data run_as_data;
	int ret = 0;
	ssize_t readlen;
	int status;
	pid_t pid;
	int retval_pipe[2];
	void *child_stack;
	int retval;

	/*
	 * If we are non-root, we can only deal with our own uid.
	 */
	if (geteuid() != 0) {
		if (uid != geteuid()) {
			ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
				uid, geteuid());
			return -EPERM;
		}
	}

	ret = pipe(retval_pipe);
	if (ret < 0) {
		PERROR("pipe");
		retval = ret;
		goto end;
	}
	run_as_data.data = data;
	run_as_data.cmd = cmd;
	run_as_data.uid = uid;
	run_as_data.gid = gid;
	run_as_data.retval_pipe = retval_pipe[1];	/* write end */
	child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
		PROT_WRITE | PROT_READ,
		MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK,
		-1, 0);
	if (child_stack == MAP_FAILED) {
		PERROR("mmap");
		retval = -ENOMEM;
		goto close_pipe;
	}
	/*
	 * Pointing to the middle of the stack to support architectures
	 * where the stack grows up (HPPA).
	 */
	pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
		&run_as_data);
	if (pid < 0) {
		PERROR("clone");
		retval = pid;
		goto unmap_stack;
	}
	/* receive return value */
	readlen = lttng_read(retval_pipe[0], &retval, sizeof(retval));
	if (readlen < sizeof(retval)) {
		ret = -1;
	}

	/*
	 * Parent: wait for child to return, in which case the
	 * shared memory map will have been created.
	 */
	pid = waitpid(pid, &status, 0);
	if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		PERROR("wait");
		retval = -1;
	}
unmap_stack:
	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
	if (ret < 0) {
		PERROR("munmap");
		retval = ret;
	}
close_pipe:
	ret = close(retval_pipe[0]);
	if (ret) {
		PERROR("close");
	}
	ret = close(retval_pipe[1]);
	if (ret) {
		PERROR("close");
	}
end:
	return retval;
}

/*
 * To be used on setups where gdb has issues debugging programs using
 * clone/rfork. Note that this is for debuging ONLY, and should not be
 * considered secure.
 */
static
int run_as_noclone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
{
	int ret;
	mode_t old_mask;

	old_mask = umask(0);
	ret = cmd(data);
	umask(old_mask);

	return ret;
}

static
int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
{
	if (use_clone()) {
		int ret;

		DBG("Using run_as_clone");
		pthread_mutex_lock(&lttng_libc_state_lock);
		ret = run_as_clone(cmd, data, uid, gid);
		pthread_mutex_unlock(&lttng_libc_state_lock);
		return ret;
	} else {
		DBG("Using run_as_noclone");
		return run_as_noclone(cmd, data, uid, gid);
	}
}

LTTNG_HIDDEN
int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
{
	struct run_as_mkdir_data data;

	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
			path, mode, uid, gid);
	data.path = path;
	data.mode = mode;
	return run_as(_mkdir_recursive, &data, uid, gid);
}

LTTNG_HIDDEN
int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
{
	struct run_as_mkdir_data data;

	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
			path, mode, uid, gid);
	data.path = path;
	data.mode = mode;
	return run_as(_mkdir, &data, uid, gid);
}

/*
 * Note: open_run_as is currently not working. We'd need to pass the fd
 * opened in the child to the parent.
 */
LTTNG_HIDDEN
int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
{
	struct run_as_open_data data;

	DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
			path, flags, mode, uid, gid);
	data.path = path;
	data.flags = flags;
	data.mode = mode;
	return run_as(_open, &data, uid, gid);
}

LTTNG_HIDDEN
int run_as_unlink(const char *path, uid_t uid, gid_t gid)
{
	struct run_as_unlink_data data;

	DBG3("unlink() %s with for uid %d and gid %d",
			path, uid, gid);
	data.path = path;
	return run_as(_unlink, &data, uid, gid);
}

LTTNG_HIDDEN
int run_as_recursive_rmdir(const char *path, uid_t uid, gid_t gid)
{
	struct run_as_recursive_rmdir_data data;

	DBG3("recursive_rmdir() %s with for uid %d and gid %d",
			path, uid, gid);
	data.path = path;
	return run_as(_recursive_rmdir, &data, uid, gid);
}
Commit	Line	Data
	1	/*
	2	* Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
	3	* Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*
	5	* This program is free software; you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License, version 2 only,
	7	* as published by the Free Software Foundation.
	8	*
	9	* This program is distributed in the hope that it will be useful, but WITHOUT
	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
	12	* more details.
	13	*
	14	* You should have received a copy of the GNU General Public License along
	15	* with this program; if not, write to the Free Software Foundation, Inc.,
	16	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	17	*/
	18
	19	#define _GNU_SOURCE
	20	#define _LGPL_SOURCE
	21	#include <errno.h>
	22	#include <limits.h>
	23	#include <stdio.h>
	24	#include <stdlib.h>
	25	#include <string.h>
	26	#include <sys/wait.h>
	27	#include <sys/types.h>
	28	#include <sys/stat.h>
	29	#include <unistd.h>
	30	#include <fcntl.h>
	31	#include <sched.h>
	32	#include <sys/signal.h>
	33
	34	#include <common/common.h>
	35	#include <common/utils.h>
	36	#include <common/compat/mman.h>
	37	#include <common/compat/clone.h>
	38	#include <common/compat/getenv.h>
	39
	40	#include "runas.h"
	41
	42	#define RUNAS_CHILD_STACK_SIZE 10485760
	43
	44	#ifndef MAP_STACK
	45	#define MAP_STACK 0
	46	#endif
	47
	48	#ifdef __FreeBSD__
	49	/* FreeBSD MAP_STACK always return -ENOMEM */
	50	#define LTTNG_MAP_STACK 0
	51	#else
	52	#define LTTNG_MAP_STACK MAP_STACK
	53	#endif
	54
	55	#ifndef MAP_GROWSDOWN
	56	#define MAP_GROWSDOWN 0
	57	#endif
	58
	59	#ifndef MAP_ANONYMOUS
	60	#define MAP_ANONYMOUS MAP_ANON
	61	#endif
	62
	63	struct run_as_data {
	64	int (cmd)(void data);
	65	void *data;
	66	uid_t uid;
	67	gid_t gid;
	68	int retval_pipe;
	69	};
	70
	71	struct run_as_mkdir_data {
	72	const char *path;
	73	mode_t mode;
	74	};
	75
	76	struct run_as_open_data {
	77	const char *path;
	78	int flags;
	79	mode_t mode;
	80	};
	81
	82	struct run_as_unlink_data {
	83	const char *path;
	84	};
	85
	86	struct run_as_recursive_rmdir_data {
	87	const char *path;
	88	};
	89
	90	#ifdef VALGRIND
	91	static
	92	int use_clone(void)
	93	{
	94	return 0;
	95	}
	96	#else
	97	static
	98	int use_clone(void)
	99	{
	100	return !lttng_secure_getenv("LTTNG_DEBUG_NOCLONE");
	101	}
	102	#endif
	103
	104	/*
	105	* Create recursively directory using the FULL path.
	106	*/
	107	static
	108	int _mkdir_recursive(void *_data)
	109	{
	110	struct run_as_mkdir_data *data = _data;
	111	const char *path;
	112	mode_t mode;
	113
	114	path = data->path;
	115	mode = data->mode;
	116
	117	return utils_mkdir_recursive(path, mode);
	118	}
	119
	120	static
	121	int _mkdir(void *_data)
	122	{
	123	int ret;
	124	struct run_as_mkdir_data *data = _data;
	125
	126	ret = mkdir(data->path, data->mode);
	127	if (ret < 0) {
	128	ret = -errno;
	129	}
	130
	131	return ret;
	132	}
	133
	134	static
	135	int _open(void *_data)
	136	{
	137	struct run_as_open_data *data = _data;
	138	return open(data->path, data->flags, data->mode);
	139	}
	140
	141	static
	142	int _unlink(void *_data)
	143	{
	144	int ret;
	145	struct run_as_unlink_data *data = _data;
	146
	147	ret = unlink(data->path);
	148	if (ret < 0) {
	149	ret = -errno;
	150	}
	151
	152	return ret;
	153	}
	154
	155	static
	156	int _recursive_rmdir(void *_data)
	157	{
	158	int ret;
	159	struct run_as_recursive_rmdir_data *data = _data;
	160
	161	ret = utils_recursive_rmdir(data->path);
	162	if (ret < 0) {
	163	ret = -errno;
	164	}
	165
	166	return ret;
	167	}
	168
	169	static
	170	int child_run_as(void *_data)
	171	{
	172	int ret;
	173	struct run_as_data *data = _data;
	174	ssize_t writelen;
	175	int sendret;
	176
	177	/*
	178	* Child: it is safe to drop egid and euid while sharing the
	179	* file descriptors with the parent process, since we do not
	180	* drop "uid": therefore, the user we are dropping egid/euid to
	181	* cannot attach to this process with, e.g. ptrace, nor map this
	182	* process memory.
	183	*/
	184	if (data->gid != getegid()) {
	185	ret = setegid(data->gid);
	186	if (ret < 0) {
	187	PERROR("setegid");
	188	sendret = -1;
	189	goto write_return;
	190	}
	191	}
	192	if (data->uid != geteuid()) {
	193	ret = seteuid(data->uid);
	194	if (ret < 0) {
	195	PERROR("seteuid");
	196	sendret = -1;
	197	goto write_return;
	198	}
	199	}
	200	/*
	201	* Also set umask to 0 for mkdir executable bit.
	202	*/
	203	umask(0);
	204	sendret = (*data->cmd)(data->data);
	205
	206	write_return:
	207	/* send back return value */
	208	writelen = lttng_write(data->retval_pipe, &sendret, sizeof(sendret));
	209	if (writelen < sizeof(sendret)) {
	210	PERROR("lttng_write error");
	211	return EXIT_FAILURE;
	212	} else {
	213	return EXIT_SUCCESS;
	214	}
	215	}
	216
	217	static
	218	int run_as_clone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	219	{
	220	struct run_as_data run_as_data;
	221	int ret = 0;
	222	ssize_t readlen;
	223	int status;
	224	pid_t pid;
	225	int retval_pipe[2];
	226	void *child_stack;
	227	int retval;
	228
	229	/*
	230	* If we are non-root, we can only deal with our own uid.
	231	*/
	232	if (geteuid() != 0) {
	233	if (uid != geteuid()) {
	234	ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
	235	uid, geteuid());
	236	return -EPERM;
	237	}
	238	}
	239
	240	ret = pipe(retval_pipe);
	241	if (ret < 0) {
	242	PERROR("pipe");
	243	retval = ret;
	244	goto end;
	245	}
	246	run_as_data.data = data;
	247	run_as_data.cmd = cmd;
	248	run_as_data.uid = uid;
	249	run_as_data.gid = gid;
	250	run_as_data.retval_pipe = retval_pipe[1]; /* write end */
	251	child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
	252	PROT_WRITE \| PROT_READ,
	253	MAP_PRIVATE \| MAP_GROWSDOWN \| MAP_ANONYMOUS \| LTTNG_MAP_STACK,
	254	-1, 0);
	255	if (child_stack == MAP_FAILED) {
	256	PERROR("mmap");
	257	retval = -ENOMEM;
	258	goto close_pipe;
	259	}
	260	/*
	261	* Pointing to the middle of the stack to support architectures
	262	* where the stack grows up (HPPA).
	263	*/
	264	pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
	265	&run_as_data);
	266	if (pid < 0) {
	267	PERROR("clone");
	268	retval = pid;
	269	goto unmap_stack;
	270	}
	271	/* receive return value */
	272	readlen = lttng_read(retval_pipe[0], &retval, sizeof(retval));
	273	if (readlen < sizeof(retval)) {
	274	ret = -1;
	275	}
	276
	277	/*
	278	* Parent: wait for child to return, in which case the
	279	* shared memory map will have been created.
	280	*/
	281	pid = waitpid(pid, &status, 0);
	282	if (pid < 0 \|\| !WIFEXITED(status) \|\| WEXITSTATUS(status) != 0) {
	283	PERROR("wait");
	284	retval = -1;
	285	}
	286	unmap_stack:
	287	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
	288	if (ret < 0) {
	289	PERROR("munmap");
	290	retval = ret;
	291	}
	292	close_pipe:
	293	ret = close(retval_pipe[0]);
	294	if (ret) {
	295	PERROR("close");
	296	}
	297	ret = close(retval_pipe[1]);
	298	if (ret) {
	299	PERROR("close");
	300	}
	301	end:
	302	return retval;
	303	}
	304
	305	/*
	306	* To be used on setups where gdb has issues debugging programs using
	307	* clone/rfork. Note that this is for debuging ONLY, and should not be
	308	* considered secure.
	309	*/
	310	static
	311	int run_as_noclone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	312	{
	313	int ret;
	314	mode_t old_mask;
	315
	316	old_mask = umask(0);
	317	ret = cmd(data);
	318	umask(old_mask);
	319
	320	return ret;
	321	}
	322
	323	static
	324	int run_as(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	325	{
	326	if (use_clone()) {
	327	int ret;
	328
	329	DBG("Using run_as_clone");
	330	pthread_mutex_lock(&lttng_libc_state_lock);
	331	ret = run_as_clone(cmd, data, uid, gid);
	332	pthread_mutex_unlock(&lttng_libc_state_lock);
	333	return ret;
	334	} else {
	335	DBG("Using run_as_noclone");
	336	return run_as_noclone(cmd, data, uid, gid);
	337	}
	338	}
	339
	340	LTTNG_HIDDEN
	341	int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
	342	{
	343	struct run_as_mkdir_data data;
	344
	345	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
	346	path, mode, uid, gid);
	347	data.path = path;
	348	data.mode = mode;
	349	return run_as(_mkdir_recursive, &data, uid, gid);
	350	}
	351
	352	LTTNG_HIDDEN
	353	int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
	354	{
	355	struct run_as_mkdir_data data;
	356
	357	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
	358	path, mode, uid, gid);
	359	data.path = path;
	360	data.mode = mode;
	361	return run_as(_mkdir, &data, uid, gid);
	362	}
	363
	364	/*
	365	* Note: open_run_as is currently not working. We'd need to pass the fd
	366	* opened in the child to the parent.
	367	*/
	368	LTTNG_HIDDEN
	369	int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
	370	{
	371	struct run_as_open_data data;
	372
	373	DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
	374	path, flags, mode, uid, gid);
	375	data.path = path;
	376	data.flags = flags;
	377	data.mode = mode;
	378	return run_as(_open, &data, uid, gid);
	379	}
	380
	381	LTTNG_HIDDEN
	382	int run_as_unlink(const char *path, uid_t uid, gid_t gid)
	383	{
	384	struct run_as_unlink_data data;
	385
	386	DBG3("unlink() %s with for uid %d and gid %d",
	387	path, uid, gid);
	388	data.path = path;
	389	return run_as(_unlink, &data, uid, gid);
	390	}
	391
	392	LTTNG_HIDDEN
	393	int run_as_recursive_rmdir(const char *path, uid_t uid, gid_t gid)
	394	{
	395	struct run_as_recursive_rmdir_data data;
	396
	397	DBG3("recursive_rmdir() %s with for uid %d and gid %d",
	398	path, uid, gid);
	399	data.path = path;
	400	return run_as(_recursive_rmdir, &data, uid, gid);
	401	}