[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 as published by the Free
 * Software Foundation; only version 2 of the License.
 *
 * 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., 59 Temple
 * Place - Suite 330, Boston, MA  02111-1307, 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

#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")) {
		DBG("Using run_as_clone");
		return run_as_clone(cmd, data, uid, gid);
	} 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	*
	5	* This program is free software; you can redistribute it and/or modify it
	6	* under the terms of the GNU General Public License as published by the Free
	7	* Software Foundation; only version 2 of the License.
	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 with
	15	* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
	16	* Place - Suite 330, Boston, MA 02111-1307, USA.
	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
0756d557 MD	41	#ifdef __FreeBSD__
	42	/* FreeBSD MAP_STACK always return -ENOMEM */
	43	#define LTTNG_MAP_STACK 0
	44	#else
	45	#define LTTNG_MAP_STACK MAP_STACK
059e1d3d MD	46	#endif
059e1d3d MD	47
a5ae566a	48	#ifndef MAP_GROWSDOWN
edb025e8	49	#define MAP_GROWSDOWN 0
a5ae566a MD	50	#endif
	51
	52	#ifndef MAP_ANONYMOUS
	53	#define MAP_ANONYMOUS MAP_ANON
	54	#endif
	55
c2b75c49 MD	56	struct run_as_data {
	57	int (cmd)(void data);
	58	void *data;
	59	uid_t uid;
	60	gid_t gid;
	61	int retval_pipe;
	62	};
	63
e11d277b	64	struct run_as_mkdir_data {
60b6c79c MD	65	const char *path;
	66	mode_t mode;
	67	};
	68
e11d277b	69	struct run_as_open_data {
60b6c79c MD	70	const char *path;
	71	int flags;
	72	mode_t mode;
	73	};
	74
	75	/*
	76	* Create recursively directory using the FULL path.
	77	*/
	78	static
	79	int _mkdir_recursive(void *_data)
	80	{
e11d277b	81	struct run_as_mkdir_data *data = _data;
60b6c79c MD	82	const char *path;
	83	char *p, tmp[PATH_MAX];
	84	struct stat statbuf;
	85	mode_t mode;
	86	size_t len;
	87	int ret;
	88
	89	path = data->path;
	90	mode = data->mode;
	91
	92	ret = snprintf(tmp, sizeof(tmp), "%s", path);
	93	if (ret < 0) {
	94	PERROR("snprintf mkdir");
	95	goto error;
	96	}
	97
	98	len = ret;
	99	if (tmp[len - 1] == '/') {
	100	tmp[len - 1] = 0;
	101	}
	102
	103	for (p = tmp + 1; *p; p++) {
	104	if (*p == '/') {
	105	*p = 0;
	106	ret = stat(tmp, &statbuf);
	107	if (ret < 0) {
	108	ret = mkdir(tmp, mode);
	109	if (ret < 0) {
	110	if (!(errno == EEXIST)) {
	111	PERROR("mkdir recursive");
	112	ret = -errno;
	113	goto error;
	114	}
	115	}
	116	}
	117	*p = '/';
	118	}
	119	}
	120
	121	ret = mkdir(tmp, mode);
	122	if (ret < 0) {
	123	if (!(errno == EEXIST)) {
	124	PERROR("mkdir recursive last piece");
	125	ret = -errno;
	126	} else {
	127	ret = 0;
	128	}
	129	}
	130
	131	error:
	132	return ret;
	133	}
	134
	135	static
	136	int _mkdir(void *_data)
	137	{
e11d277b	138	struct run_as_mkdir_data *data = _data;
60b6c79c MD	139	return mkdir(data->path, data->mode);
	140	}
	141
	142	static
	143	int _open(void *_data)
	144	{
e11d277b	145	struct run_as_open_data *data = _data;
60b6c79c MD	146	return open(data->path, data->flags, data->mode);
	147	}
	148
c2b75c49 MD	149	static
	150	int child_run_as(void *_data)
	151	{
	152	struct run_as_data *data = _data;
	153	size_t writelen, writeleft, index;
	154	union {
	155	int i;
	156	char c[sizeof(int)];
	157	} sendret;
	158	int ret;
	159
	160	/*
	161	* Child: it is safe to drop egid and euid while sharing the
	162	* file descriptors with the parent process, since we do not
	163	* drop "uid": therefore, the user we are dropping egid/euid to
	164	* cannot attach to this process with, e.g. ptrace, nor map this
	165	* process memory.
	166	*/
1576d582 MD	167	if (data->gid != getegid()) {
	168	ret = setegid(data->gid);
	169	if (ret < 0) {
4c462e79	170	PERROR("setegid");
6da9f915	171	return EXIT_FAILURE;
1576d582	172	}
c2b75c49	173	}
1576d582 MD	174	if (data->uid != geteuid()) {
	175	ret = seteuid(data->uid);
	176	if (ret < 0) {
4c462e79	177	PERROR("seteuid");
6da9f915	178	return EXIT_FAILURE;
1576d582	179	}
c2b75c49 MD	180	}
	181	/*
	182	* Also set umask to 0 for mkdir executable bit.
	183	*/
	184	umask(0);
	185	sendret.i = (*data->cmd)(data->data);
	186	/* send back return value */
	187	writeleft = sizeof(sendret);
	188	index = 0;
	189	do {
	190	writelen = write(data->retval_pipe, &sendret.c[index],
	191	writeleft);
	192	if (writelen < 0) {
4c462e79	193	PERROR("write");
6da9f915	194	return EXIT_FAILURE;
c2b75c49 MD	195	}
	196	writeleft -= writelen;
	197	index += writelen;
	198	} while (writeleft > 0);
6da9f915	199	return EXIT_SUCCESS;
c2b75c49 MD	200	}
c2b75c49 MD	201
60b6c79c	202	static
2d85a600	203	int run_as_clone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
60b6c79c	204	{
c2b75c49	205	struct run_as_data run_as_data;
60b6c79c	206	int ret = 0;
c2b75c49	207	int status;
60b6c79c	208	pid_t pid;
c2b75c49 MD	209	int retval_pipe[2];
c2b75c49 MD	210	ssize_t readlen, readleft, index;
d5bd7573	211	void *child_stack;
c2b75c49 MD	212	union {
	213	int i;
	214	char c[sizeof(int)];
	215	} retval;
60b6c79c MD	216
	217	/*
	218	* If we are non-root, we can only deal with our own uid.
	219	*/
	220	if (geteuid() != 0) {
	221	if (uid != geteuid()) {
	222	ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
	223	uid, geteuid());
	224	return -EPERM;
	225	}
60b6c79c MD	226	}
60b6c79c MD	227
c2b75c49 MD	228	ret = pipe(retval_pipe);
c2b75c49 MD	229	if (ret < 0) {
4c462e79	230	PERROR("pipe");
def5e0e8	231	retval.i = ret;
60b6c79c	232	goto end;
c2b75c49 MD	233	}
	234	run_as_data.data = data;
	235	run_as_data.cmd = cmd;
	236	run_as_data.uid = uid;
	237	run_as_data.gid = gid;
	238	run_as_data.retval_pipe = retval_pipe[1]; /* write end */
e11d277b	239	child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
d5bd7573	240	PROT_WRITE \| PROT_READ,
0756d557	241	MAP_PRIVATE \| MAP_GROWSDOWN \| MAP_ANONYMOUS \| LTTNG_MAP_STACK,
d5bd7573 MD	242	-1, 0);
d5bd7573 MD	243	if (child_stack == MAP_FAILED) {
4c462e79	244	PERROR("mmap");
def5e0e8	245	retval.i = -ENOMEM;
d5bd7573 MD	246	goto close_pipe;
	247	}
	248	/*
	249	* Pointing to the middle of the stack to support architectures
	250	* where the stack grows up (HPPA).
	251	*/
89831a74 MD	252	pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
89831a74 MD	253	&run_as_data);
c2b75c49	254	if (pid < 0) {
4c462e79	255	PERROR("clone");
def5e0e8	256	retval.i = pid;
d5bd7573	257	goto unmap_stack;
c2b75c49 MD	258	}
	259	/* receive return value */
	260	readleft = sizeof(retval);
	261	index = 0;
	262	do {
	263	readlen = read(retval_pipe[0], &retval.c[index], readleft);
	264	if (readlen < 0) {
4c462e79	265	PERROR("read");
c2b75c49 MD	266	ret = -1;
c2b75c49 MD	267	break;
60b6c79c	268	}
c2b75c49 MD	269	readleft -= readlen;
	270	index += readlen;
	271	} while (readleft > 0);
	272
	273	/*
	274	* Parent: wait for child to return, in which case the
	275	* shared memory map will have been created.
	276	*/
47fb7563	277	pid = waitpid(pid, &status, 0);
c2b75c49	278	if (pid < 0 \|\| !WIFEXITED(status) \|\| WEXITSTATUS(status) != 0) {
4c462e79	279	PERROR("wait");
def5e0e8	280	retval.i = -1;
60b6c79c	281	}
d5bd7573	282	unmap_stack:
e11d277b	283	ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
d5bd7573	284	if (ret < 0) {
4c462e79	285	PERROR("munmap");
def5e0e8	286	retval.i = ret;
d5bd7573	287	}
c2b75c49	288	close_pipe:
4c462e79 MD	289	ret = close(retval_pipe[0]);
	290	if (ret) {
	291	PERROR("close");
	292	}
	293	ret = close(retval_pipe[1]);
	294	if (ret) {
	295	PERROR("close");
	296	}
60b6c79c	297	end:
c2b75c49	298	return retval.i;
60b6c79c MD	299	}
60b6c79c MD	300
2d85a600 MD	301	/*
	302	* To be used on setups where gdb has issues debugging programs using
	303	* clone/rfork. Note that this is for debuging ONLY, and should not be
	304	* considered secure.
	305	*/
	306	static
	307	int run_as_noclone(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	308	{
	309	return cmd(data);
	310	}
	311
	312	static
	313	int run_as(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	314	{
	315	if (!getenv("LTTNG_DEBUG_NOCLONE")) {
	316	DBG("Using run_as_clone");
	317	return run_as_clone(cmd, data, uid, gid);
	318	} else {
	319	DBG("Using run_as_noclone");
	320	return run_as_noclone(cmd, data, uid, gid);
	321	}
	322	}
	323
e11d277b	324	int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	325	{
e11d277b	326	struct run_as_mkdir_data data;
60b6c79c MD	327
	328	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
	329	path, mode, uid, gid);
	330	data.path = path;
	331	data.mode = mode;
	332	return run_as(_mkdir_recursive, &data, uid, gid);
	333	}
	334
e11d277b	335	int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	336	{
e11d277b	337	struct run_as_mkdir_data data;
60b6c79c MD	338
	339	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
	340	path, mode, uid, gid);
	341	data.path = path;
	342	data.mode = mode;
	343	return run_as(_mkdir, &data, uid, gid);
	344	}
	345
	346	/*
	347	* Note: open_run_as is currently not working. We'd need to pass the fd
	348	* opened in the child to the parent.
	349	*/
e11d277b	350	int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
60b6c79c	351	{
e11d277b	352	struct run_as_open_data data;
c2b75c49	353
47fb7563 MD	354	DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
47fb7563 MD	355	path, flags, mode, uid, gid);
60b6c79c MD	356	data.path = path;
	357	data.flags = flags;
	358	data.mode = mode;
	359	return run_as(_open, &data, uid, gid);
60b6c79c	360	}