[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 MAP_STACK
#define MAP_STACK		0
#endif

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