[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
#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 "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;
};

/*
 * 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)
{
	struct run_as_mkdir_data *data = _data;
	return mkdir(data->path, data->mode);
}

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

static
int child_run_as(void *_data)
{
	int ret;
	struct run_as_data *data = _data;
	ssize_t writelen;
	size_t writeleft, index;
	union {
		int i;
		char c[sizeof(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.i = -1;
			goto write_return;
		}
	}
	if (data->uid != geteuid()) {
		ret = seteuid(data->uid);
		if (ret < 0) {
			PERROR("seteuid");
			sendret.i = -1;
			goto write_return;
		}
	}
	/*
	 * Also set umask to 0 for mkdir executable bit.
	 */
	umask(0);
	sendret.i = (*data->cmd)(data->data);

write_return:
	/* send back return value */
	writeleft = sizeof(sendret);
	index = 0;
	do {
		do {
			writelen = write(data->retval_pipe, &sendret.c[index],
					writeleft);
		} while (writelen < 0 && errno == EINTR);
		if (writelen < 0) {
			PERROR("write");
			return EXIT_FAILURE;
		}
		writeleft -= writelen;
		index += writelen;
	} while (writeleft > 0);
	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;
	int status;
	pid_t pid;
	int retval_pipe[2];
	ssize_t readlen, readleft, index;
	void *child_stack;
	union {
		int i;
		char c[sizeof(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.i = 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.i = -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.i = pid;
		goto unmap_stack;
	}
	/* receive return value */
	readleft = sizeof(retval);
	index = 0;
	do {
		readlen = read(retval_pipe[0], &retval.c[index], readleft);
		if (readlen < 0) {
			PERROR("read");
			ret = -1;
			break;
		}
		readleft -= readlen;
		index += readlen;
	} while (readleft > 0);

	/*
	 * 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.i = -1;
	}
unmap_stack:
	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
	if (ret < 0) {
		PERROR("munmap");
		retval.i = ret;
	}
close_pipe:
	ret = close(retval_pipe[0]);
	if (ret) {
		PERROR("close");
	}
	ret = close(retval_pipe[1]);
	if (ret) {
		PERROR("close");
	}
end:
	return retval.i;
}

/*
 * 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 (!getenv("LTTNG_DEBUG_NOCLONE")) {
		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);
}
Commit	Line	Data
60b6c79c MD	1	/*
	2	* Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
	3	* Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*
d14d33bf AM	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.
60b6c79c MD	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
d14d33bf	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
60b6c79c MD	12	* more details.
60b6c79c MD	13	*
d14d33bf AM	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.
60b6c79c MD	17	*/
	18
	19	#define _GNU_SOURCE
	20	#include <errno.h>
	21	#include <limits.h>
	22	#include <stdio.h>
	23	#include <stdlib.h>
	24	#include <string.h>
	25	#include <sys/wait.h>
	26	#include <sys/types.h>
	27	#include <sys/stat.h>
	28	#include <unistd.h>
	29	#include <fcntl.h>
c2b75c49	30	#include <sched.h>
730389d9	31	#include <sys/signal.h>
60b6c79c	32
90e535ef	33	#include <common/common.h>
3fd15a74	34	#include <common/utils.h>
730389d9 DG	35	#include <common/compat/mman.h>
730389d9 DG	36	#include <common/compat/clone.h>
60b6c79c	37
0857097f DG	38	#include "runas.h"
0857097f DG	39
e11d277b	40	#define RUNAS_CHILD_STACK_SIZE 10485760
c2b75c49	41
1e4035fc AS	42	#ifndef MAP_STACK
	43	#define MAP_STACK 0
	44	#endif
	45
0756d557 MD	46	#ifdef __FreeBSD__
	47	/* FreeBSD MAP_STACK always return -ENOMEM */
	48	#define LTTNG_MAP_STACK 0
	49	#else
	50	#define LTTNG_MAP_STACK MAP_STACK
059e1d3d MD	51	#endif
059e1d3d MD	52
a5ae566a	53	#ifndef MAP_GROWSDOWN
edb025e8	54	#define MAP_GROWSDOWN 0
a5ae566a MD	55	#endif
	56
	57	#ifndef MAP_ANONYMOUS
	58	#define MAP_ANONYMOUS MAP_ANON
	59	#endif
	60
c2b75c49 MD	61	struct run_as_data {
	62	int (cmd)(void data);
	63	void *data;
	64	uid_t uid;
	65	gid_t gid;
	66	int retval_pipe;
	67	};
	68
e11d277b	69	struct run_as_mkdir_data {
60b6c79c MD	70	const char *path;
	71	mode_t mode;
	72	};
	73
e11d277b	74	struct run_as_open_data {
60b6c79c MD	75	const char *path;
	76	int flags;
	77	mode_t mode;
	78	};
	79
	80	/*
	81	* Create recursively directory using the FULL path.
	82	*/
	83	static
	84	int _mkdir_recursive(void *_data)
	85	{
e11d277b	86	struct run_as_mkdir_data *data = _data;
60b6c79c	87	const char *path;
60b6c79c	88	mode_t mode;
60b6c79c MD	89
	90	path = data->path;
	91	mode = data->mode;
	92
3fd15a74	93	return utils_mkdir_recursive(path, mode);
60b6c79c MD	94	}
	95
	96	static
	97	int _mkdir(void *_data)
	98	{
e11d277b	99	struct run_as_mkdir_data *data = _data;
60b6c79c MD	100	return mkdir(data->path, data->mode);
	101	}
	102
	103	static
	104	int _open(void *_data)
	105	{
e11d277b	106	struct run_as_open_data *data = _data;
60b6c79c MD	107	return open(data->path, data->flags, data->mode);
	108	}
	109
c2b75c49 MD	110	static
	111	int child_run_as(void *_data)
	112	{
6775595e	113	int ret;
c2b75c49	114	struct run_as_data *data = _data;
6775595e DG	115	ssize_t writelen;
6775595e DG	116	size_t writeleft, index;
c2b75c49 MD	117	union {
	118	int i;
	119	char c[sizeof(int)];
	120	} sendret;
c2b75c49 MD	121
	122	/*
	123	* Child: it is safe to drop egid and euid while sharing the
	124	* file descriptors with the parent process, since we do not
	125	* drop "uid": therefore, the user we are dropping egid/euid to
	126	* cannot attach to this process with, e.g. ptrace, nor map this
	127	* process memory.
	128	*/
1576d582 MD	129	if (data->gid != getegid()) {
	130	ret = setegid(data->gid);
	131	if (ret < 0) {
4c462e79	132	PERROR("setegid");
6d73c4ef MD	133	sendret.i = -1;
6d73c4ef MD	134	goto write_return;
1576d582	135	}
c2b75c49	136	}
1576d582 MD	137	if (data->uid != geteuid()) {
	138	ret = seteuid(data->uid);
	139	if (ret < 0) {
4c462e79	140	PERROR("seteuid");
6d73c4ef MD	141	sendret.i = -1;
6d73c4ef MD	142	goto write_return;
1576d582	143	}
c2b75c49 MD	144	}
	145	/*
	146	* Also set umask to 0 for mkdir executable bit.
	147	*/
	148	umask(0);
	149	sendret.i = (*data->cmd)(data->data);
6d73c4ef MD	150
6d73c4ef MD	151	write_return:
c2b75c49 MD	152	/* send back return value */
	153	writeleft = sizeof(sendret);
	154	index = 0;
	155	do {
6f94560a MD	156	do {
	157	writelen = write(data->retval_pipe, &sendret.c[index],
	158	writeleft);
	159	} while (writelen < 0 && errno == EINTR);
c2b75c49	160	if (writelen < 0) {
4c462e79	161	PERROR("write");
6da9f915	162	return EXIT_FAILURE;
c2b75c49 MD	163	}
	164	writeleft -= writelen;
	165	index += writelen;
	166	} while (writeleft > 0);
6da9f915	167	return EXIT_SUCCESS;
c2b75c49 MD	168	}
c2b75c49 MD	169
60b6c79c	170	static
2d85a600	171	int run_as_clone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
60b6c79c	172	{
c2b75c49	173	struct run_as_data run_as_data;
60b6c79c	174	int ret = 0;
c2b75c49	175	int status;
60b6c79c	176	pid_t pid;
c2b75c49 MD	177	int retval_pipe[2];
c2b75c49 MD	178	ssize_t readlen, readleft, index;
d5bd7573	179	void *child_stack;
c2b75c49 MD	180	union {
	181	int i;
	182	char c[sizeof(int)];
	183	} retval;
60b6c79c MD	184
	185	/*
	186	* If we are non-root, we can only deal with our own uid.
	187	*/
	188	if (geteuid() != 0) {
	189	if (uid != geteuid()) {
	190	ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
	191	uid, geteuid());
	192	return -EPERM;
	193	}
60b6c79c MD	194	}
60b6c79c MD	195
c2b75c49 MD	196	ret = pipe(retval_pipe);
c2b75c49 MD	197	if (ret < 0) {
4c462e79	198	PERROR("pipe");
def5e0e8	199	retval.i = ret;
60b6c79c	200	goto end;
c2b75c49 MD	201	}
	202	run_as_data.data = data;
	203	run_as_data.cmd = cmd;
	204	run_as_data.uid = uid;
	205	run_as_data.gid = gid;
	206	run_as_data.retval_pipe = retval_pipe[1]; /* write end */
e11d277b	207	child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
d5bd7573	208	PROT_WRITE \| PROT_READ,
0756d557	209	MAP_PRIVATE \| MAP_GROWSDOWN \| MAP_ANONYMOUS \| LTTNG_MAP_STACK,
d5bd7573 MD	210	-1, 0);
d5bd7573 MD	211	if (child_stack == MAP_FAILED) {
4c462e79	212	PERROR("mmap");
def5e0e8	213	retval.i = -ENOMEM;
d5bd7573 MD	214	goto close_pipe;
	215	}
	216	/*
	217	* Pointing to the middle of the stack to support architectures
	218	* where the stack grows up (HPPA).
	219	*/
89831a74 MD	220	pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
89831a74 MD	221	&run_as_data);
c2b75c49	222	if (pid < 0) {
4c462e79	223	PERROR("clone");
def5e0e8	224	retval.i = pid;
d5bd7573	225	goto unmap_stack;
c2b75c49 MD	226	}
	227	/* receive return value */
	228	readleft = sizeof(retval);
	229	index = 0;
	230	do {
	231	readlen = read(retval_pipe[0], &retval.c[index], readleft);
	232	if (readlen < 0) {
4c462e79	233	PERROR("read");
c2b75c49 MD	234	ret = -1;
c2b75c49 MD	235	break;
60b6c79c	236	}
c2b75c49 MD	237	readleft -= readlen;
	238	index += readlen;
	239	} while (readleft > 0);
	240
	241	/*
	242	* Parent: wait for child to return, in which case the
	243	* shared memory map will have been created.
	244	*/
47fb7563	245	pid = waitpid(pid, &status, 0);
c2b75c49	246	if (pid < 0 \|\| !WIFEXITED(status) \|\| WEXITSTATUS(status) != 0) {
4c462e79	247	PERROR("wait");
def5e0e8	248	retval.i = -1;
60b6c79c	249	}
d5bd7573	250	unmap_stack:
e11d277b	251	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
d5bd7573	252	if (ret < 0) {
4c462e79	253	PERROR("munmap");
def5e0e8	254	retval.i = ret;
d5bd7573	255	}
c2b75c49	256	close_pipe:
4c462e79 MD	257	ret = close(retval_pipe[0]);
	258	if (ret) {
	259	PERROR("close");
	260	}
	261	ret = close(retval_pipe[1]);
	262	if (ret) {
	263	PERROR("close");
	264	}
60b6c79c	265	end:
c2b75c49	266	return retval.i;
60b6c79c MD	267	}
60b6c79c MD	268
2d85a600 MD	269	/*
	270	* To be used on setups where gdb has issues debugging programs using
	271	* clone/rfork. Note that this is for debuging ONLY, and should not be
	272	* considered secure.
	273	*/
	274	static
	275	int run_as_noclone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	276	{
5b73926f DG	277	int ret;
	278	mode_t old_mask;
	279
	280	old_mask = umask(0);
	281	ret = cmd(data);
	282	umask(old_mask);
	283
	284	return ret;
2d85a600 MD	285	}
	286
	287	static
	288	int run_as(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	289	{
	290	if (!getenv("LTTNG_DEBUG_NOCLONE")) {
9ef70f87 MD	291	int ret;
9ef70f87 MD	292
2d85a600	293	DBG("Using run_as_clone");
9ef70f87 MD	294	pthread_mutex_lock(&lttng_libc_state_lock);
	295	ret = run_as_clone(cmd, data, uid, gid);
	296	pthread_mutex_unlock(&lttng_libc_state_lock);
	297	return ret;
2d85a600 MD	298	} else {
	299	DBG("Using run_as_noclone");
	300	return run_as_noclone(cmd, data, uid, gid);
	301	}
	302	}
	303
90e535ef	304	LTTNG_HIDDEN
e11d277b	305	int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	306	{
e11d277b	307	struct run_as_mkdir_data data;
60b6c79c MD	308
	309	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
	310	path, mode, uid, gid);
	311	data.path = path;
	312	data.mode = mode;
	313	return run_as(_mkdir_recursive, &data, uid, gid);
	314	}
	315
90e535ef	316	LTTNG_HIDDEN
e11d277b	317	int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	318	{
e11d277b	319	struct run_as_mkdir_data data;
60b6c79c MD	320
	321	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
	322	path, mode, uid, gid);
	323	data.path = path;
	324	data.mode = mode;
	325	return run_as(_mkdir, &data, uid, gid);
	326	}
	327
	328	/*
	329	* Note: open_run_as is currently not working. We'd need to pass the fd
	330	* opened in the child to the parent.
	331	*/
90e535ef	332	LTTNG_HIDDEN
e11d277b	333	int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	334	{
e11d277b	335	struct run_as_open_data data;
c2b75c49	336
47fb7563 MD	337	DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
47fb7563 MD	338	path, flags, mode, uid, gid);
60b6c79c MD	339	data.path = path;
	340	data.flags = flags;
	341	data.mode = mode;
	342	return run_as(_open, &data, uid, gid);
60b6c79c	343	}