[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/error.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;
	char *p, tmp[PATH_MAX];
	struct stat statbuf;
	mode_t mode;
	size_t len;
	int ret;

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

	ret = snprintf(tmp, sizeof(tmp), "%s", path);
	if (ret < 0) {
		PERROR("snprintf mkdir");
		goto error;
	}

	len = ret;
	if (tmp[len - 1] == '/') {
		tmp[len - 1] = 0;
	}

	for (p = tmp + 1; *p; p++) {
		if (*p == '/') {
			*p = 0;
			ret = stat(tmp, &statbuf);
			if (ret < 0) {
				ret = mkdir(tmp, mode);
				if (ret < 0) {
					if (!(errno == EEXIST)) {
						PERROR("mkdir recursive");
						ret = -errno;
						goto error;
					}
				}
			}
			*p = '/';
		}
	}

	ret = mkdir(tmp, mode);
	if (ret < 0) {
		if (!(errno == EEXIST)) {
			PERROR("mkdir recursive last piece");
			ret = -errno;
		} else {
			ret = 0;
		}
	}

error:
	return ret;
}

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)
{
	struct run_as_data *data = _data;
	size_t writelen, writeleft, index;
	union {
		int i;
		char c[sizeof(int)];
	} sendret;
	int ret;

	/*
	 * 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");
			return EXIT_FAILURE;
		}
	}
	if (data->uid != geteuid()) {
		ret = seteuid(data->uid);
		if (ret < 0) {
			PERROR("seteuid");
			return EXIT_FAILURE;
		}
	}
	/*
	 * Also set umask to 0 for mkdir executable bit.
	 */
	umask(0);
	sendret.i = (*data->cmd)(data->data);
	/* send back return value */
	writeleft = sizeof(sendret);
	index = 0;
	do {
		writelen = write(data->retval_pipe, &sendret.c[index],
				writeleft);
		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)
{
	return cmd(data);
}

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);
	}
}

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);
}

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.
 */
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
db758600	33	#include <common/error.h>
730389d9 DG	34	#include <common/compat/mman.h>
730389d9 DG	35	#include <common/compat/clone.h>
60b6c79c	36
0857097f DG	37	#include "runas.h"
0857097f DG	38
e11d277b	39	#define RUNAS_CHILD_STACK_SIZE 10485760
c2b75c49	40
1e4035fc AS	41	#ifndef MAP_STACK
	42	#define MAP_STACK 0
	43	#endif
	44
0756d557 MD	45	#ifdef __FreeBSD__
	46	/* FreeBSD MAP_STACK always return -ENOMEM */
	47	#define LTTNG_MAP_STACK 0
	48	#else
	49	#define LTTNG_MAP_STACK MAP_STACK
059e1d3d MD	50	#endif
059e1d3d MD	51
a5ae566a	52	#ifndef MAP_GROWSDOWN
edb025e8	53	#define MAP_GROWSDOWN 0
a5ae566a MD	54	#endif
	55
	56	#ifndef MAP_ANONYMOUS
	57	#define MAP_ANONYMOUS MAP_ANON
	58	#endif
	59
c2b75c49 MD	60	struct run_as_data {
	61	int (cmd)(void data);
	62	void *data;
	63	uid_t uid;
	64	gid_t gid;
	65	int retval_pipe;
	66	};
	67
e11d277b	68	struct run_as_mkdir_data {
60b6c79c MD	69	const char *path;
	70	mode_t mode;
	71	};
	72
e11d277b	73	struct run_as_open_data {
60b6c79c MD	74	const char *path;
	75	int flags;
	76	mode_t mode;
	77	};
	78
	79	/*
	80	* Create recursively directory using the FULL path.
	81	*/
	82	static
	83	int _mkdir_recursive(void *_data)
	84	{
e11d277b	85	struct run_as_mkdir_data *data = _data;
60b6c79c MD	86	const char *path;
	87	char *p, tmp[PATH_MAX];
	88	struct stat statbuf;
	89	mode_t mode;
	90	size_t len;
	91	int ret;
	92
	93	path = data->path;
	94	mode = data->mode;
	95
	96	ret = snprintf(tmp, sizeof(tmp), "%s", path);
	97	if (ret < 0) {
	98	PERROR("snprintf mkdir");
	99	goto error;
	100	}
	101
	102	len = ret;
	103	if (tmp[len - 1] == '/') {
	104	tmp[len - 1] = 0;
	105	}
	106
	107	for (p = tmp + 1; *p; p++) {
	108	if (*p == '/') {
	109	*p = 0;
	110	ret = stat(tmp, &statbuf);
	111	if (ret < 0) {
	112	ret = mkdir(tmp, mode);
	113	if (ret < 0) {
	114	if (!(errno == EEXIST)) {
	115	PERROR("mkdir recursive");
	116	ret = -errno;
	117	goto error;
	118	}
	119	}
	120	}
	121	*p = '/';
	122	}
	123	}
	124
	125	ret = mkdir(tmp, mode);
	126	if (ret < 0) {
	127	if (!(errno == EEXIST)) {
	128	PERROR("mkdir recursive last piece");
	129	ret = -errno;
	130	} else {
	131	ret = 0;
	132	}
	133	}
	134
	135	error:
	136	return ret;
	137	}
	138
	139	static
	140	int _mkdir(void *_data)
	141	{
e11d277b	142	struct run_as_mkdir_data *data = _data;
60b6c79c MD	143	return mkdir(data->path, data->mode);
	144	}
	145
	146	static
	147	int _open(void *_data)
	148	{
e11d277b	149	struct run_as_open_data *data = _data;
60b6c79c MD	150	return open(data->path, data->flags, data->mode);
	151	}
	152
c2b75c49 MD	153	static
	154	int child_run_as(void *_data)
	155	{
	156	struct run_as_data *data = _data;
	157	size_t writelen, writeleft, index;
	158	union {
	159	int i;
	160	char c[sizeof(int)];
	161	} sendret;
	162	int ret;
	163
	164	/*
	165	* Child: it is safe to drop egid and euid while sharing the
	166	* file descriptors with the parent process, since we do not
	167	* drop "uid": therefore, the user we are dropping egid/euid to
	168	* cannot attach to this process with, e.g. ptrace, nor map this
	169	* process memory.
	170	*/
1576d582 MD	171	if (data->gid != getegid()) {
	172	ret = setegid(data->gid);
	173	if (ret < 0) {
4c462e79	174	PERROR("setegid");
6da9f915	175	return EXIT_FAILURE;
1576d582	176	}
c2b75c49	177	}
1576d582 MD	178	if (data->uid != geteuid()) {
	179	ret = seteuid(data->uid);
	180	if (ret < 0) {
4c462e79	181	PERROR("seteuid");
6da9f915	182	return EXIT_FAILURE;
1576d582	183	}
c2b75c49 MD	184	}
	185	/*
	186	* Also set umask to 0 for mkdir executable bit.
	187	*/
	188	umask(0);
	189	sendret.i = (*data->cmd)(data->data);
	190	/* send back return value */
	191	writeleft = sizeof(sendret);
	192	index = 0;
	193	do {
	194	writelen = write(data->retval_pipe, &sendret.c[index],
	195	writeleft);
	196	if (writelen < 0) {
4c462e79	197	PERROR("write");
6da9f915	198	return EXIT_FAILURE;
c2b75c49 MD	199	}
	200	writeleft -= writelen;
	201	index += writelen;
	202	} while (writeleft > 0);
6da9f915	203	return EXIT_SUCCESS;
c2b75c49 MD	204	}
c2b75c49 MD	205
60b6c79c	206	static
2d85a600	207	int run_as_clone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
60b6c79c	208	{
c2b75c49	209	struct run_as_data run_as_data;
60b6c79c	210	int ret = 0;
c2b75c49	211	int status;
60b6c79c	212	pid_t pid;
c2b75c49 MD	213	int retval_pipe[2];
c2b75c49 MD	214	ssize_t readlen, readleft, index;
d5bd7573	215	void *child_stack;
c2b75c49 MD	216	union {
	217	int i;
	218	char c[sizeof(int)];
	219	} retval;
60b6c79c MD	220
	221	/*
	222	* If we are non-root, we can only deal with our own uid.
	223	*/
	224	if (geteuid() != 0) {
	225	if (uid != geteuid()) {
	226	ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
	227	uid, geteuid());
	228	return -EPERM;
	229	}
60b6c79c MD	230	}
60b6c79c MD	231
c2b75c49 MD	232	ret = pipe(retval_pipe);
c2b75c49 MD	233	if (ret < 0) {
4c462e79	234	PERROR("pipe");
def5e0e8	235	retval.i = ret;
60b6c79c	236	goto end;
c2b75c49 MD	237	}
	238	run_as_data.data = data;
	239	run_as_data.cmd = cmd;
	240	run_as_data.uid = uid;
	241	run_as_data.gid = gid;
	242	run_as_data.retval_pipe = retval_pipe[1]; /* write end */
e11d277b	243	child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
d5bd7573	244	PROT_WRITE \| PROT_READ,
0756d557	245	MAP_PRIVATE \| MAP_GROWSDOWN \| MAP_ANONYMOUS \| LTTNG_MAP_STACK,
d5bd7573 MD	246	-1, 0);
d5bd7573 MD	247	if (child_stack == MAP_FAILED) {
4c462e79	248	PERROR("mmap");
def5e0e8	249	retval.i = -ENOMEM;
d5bd7573 MD	250	goto close_pipe;
	251	}
	252	/*
	253	* Pointing to the middle of the stack to support architectures
	254	* where the stack grows up (HPPA).
	255	*/
89831a74 MD	256	pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
89831a74 MD	257	&run_as_data);
c2b75c49	258	if (pid < 0) {
4c462e79	259	PERROR("clone");
def5e0e8	260	retval.i = pid;
d5bd7573	261	goto unmap_stack;
c2b75c49 MD	262	}
	263	/* receive return value */
	264	readleft = sizeof(retval);
	265	index = 0;
	266	do {
	267	readlen = read(retval_pipe[0], &retval.c[index], readleft);
	268	if (readlen < 0) {
4c462e79	269	PERROR("read");
c2b75c49 MD	270	ret = -1;
c2b75c49 MD	271	break;
60b6c79c	272	}
c2b75c49 MD	273	readleft -= readlen;
	274	index += readlen;
	275	} while (readleft > 0);
	276
	277	/*
	278	* Parent: wait for child to return, in which case the
	279	* shared memory map will have been created.
	280	*/
47fb7563	281	pid = waitpid(pid, &status, 0);
c2b75c49	282	if (pid < 0 \|\| !WIFEXITED(status) \|\| WEXITSTATUS(status) != 0) {
4c462e79	283	PERROR("wait");
def5e0e8	284	retval.i = -1;
60b6c79c	285	}
d5bd7573	286	unmap_stack:
e11d277b	287	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
d5bd7573	288	if (ret < 0) {
4c462e79	289	PERROR("munmap");
def5e0e8	290	retval.i = ret;
d5bd7573	291	}
c2b75c49	292	close_pipe:
4c462e79 MD	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	}
60b6c79c	301	end:
c2b75c49	302	return retval.i;
60b6c79c MD	303	}
60b6c79c MD	304
2d85a600 MD	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	return cmd(data);
	314	}
	315
	316	static
	317	int run_as(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	318	{
	319	if (!getenv("LTTNG_DEBUG_NOCLONE")) {
9ef70f87 MD	320	int ret;
9ef70f87 MD	321
2d85a600	322	DBG("Using run_as_clone");
9ef70f87 MD	323	pthread_mutex_lock(&lttng_libc_state_lock);
	324	ret = run_as_clone(cmd, data, uid, gid);
	325	pthread_mutex_unlock(&lttng_libc_state_lock);
	326	return ret;
2d85a600 MD	327	} else {
	328	DBG("Using run_as_noclone");
	329	return run_as_noclone(cmd, data, uid, gid);
	330	}
	331	}
	332
e11d277b	333	int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	334	{
e11d277b	335	struct run_as_mkdir_data data;
60b6c79c MD	336
	337	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
	338	path, mode, uid, gid);
	339	data.path = path;
	340	data.mode = mode;
	341	return run_as(_mkdir_recursive, &data, uid, gid);
	342	}
	343
e11d277b	344	int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	345	{
e11d277b	346	struct run_as_mkdir_data data;
60b6c79c MD	347
	348	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
	349	path, mode, uid, gid);
	350	data.path = path;
	351	data.mode = mode;
	352	return run_as(_mkdir, &data, uid, gid);
	353	}
	354
	355	/*
	356	* Note: open_run_as is currently not working. We'd need to pass the fd
	357	* opened in the child to the parent.
	358	*/
e11d277b	359	int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	360	{
e11d277b	361	struct run_as_open_data data;
c2b75c49	362
47fb7563 MD	363	DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
47fb7563 MD	364	path, flags, mode, uid, gid);
60b6c79c MD	365	data.path = path;
	366	data.flags = flags;
	367	data.mode = mode;
	368	return run_as(_open, &data, uid, gid);
60b6c79c	369	}