[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

#ifndef __FreeBSD__
# ifndef MAP_STACK
#  define MAP_STACK		0
# endif
#else	/* FreeBSD MAP_STACK always return -ENOMEM */
# define MAP_STACK		0
#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(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 | 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:
	close(retval_pipe[0]);
	close(retval_pipe[1]);
end:
	return retval.i;
}

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