[lttng-tools.git] / librunas / 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/mman.h>

#include <lttngerr.h>

#define CHILD_STACK_SIZE	10485760

struct run_as_data {
	int (*cmd)(void *data);
	void *data;
	uid_t uid;
	gid_t gid;
	int retval_pipe;
};

struct mkdir_data {
	const char *path;
	mode_t mode;
};

struct open_data {
	const char *path;
	int flags;
	mode_t mode;
};

/*
 * Create recursively directory using the FULL path.
 */
static
int _mkdir_recursive(void *_data)
{
	struct 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 mkdir_data *data = _data;
	return mkdir(data->path, data->mode);
}

static
int _open(void *_data)
{
	struct 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");
			exit(EXIT_FAILURE);
		}
	}
	if (data->uid != geteuid()) {
		ret = seteuid(data->uid);
		if (ret < 0) {
			perror("seteuid");
			exit(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");
			exit(EXIT_FAILURE);
		}
		writeleft -= writelen;
		index += writelen;
	} while (writeleft > 0);

	exit(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");
		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, CHILD_STACK_SIZE,
		PROT_WRITE | PROT_READ,
		MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | MAP_STACK,
		-1, 0);
	if (child_stack == MAP_FAILED) {
		perror("mmap");
		ret = -ENOMEM;
		goto close_pipe;
	}
	/*
	 * Pointing to the middle of the stack to support architectures
	 * where the stack grows up (HPPA).
	 */
	pid = clone(child_run_as, child_stack + (CHILD_STACK_SIZE / 2),
		CLONE_FILES | SIGCHLD,
		&run_as_data, NULL);
	if (pid < 0) {
		perror("clone");
		ret = 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 = wait(&status);
	if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		perror("wait");
		ret = -1;
	}
unmap_stack:
	ret = munmap(child_stack, CHILD_STACK_SIZE);
	if (ret < 0) {
		perror("munmap");
	}
close_pipe:
	close(retval_pipe[0]);
	close(retval_pipe[1]);
end:
	return retval.i;
}

int mkdir_recursive_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
{
	struct 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 mkdir_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
{
	struct 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 open_run_as(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
{
	struct open_data data;

	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>
d5bd7573	31	#include <sys/mman.h>
60b6c79c MD	32
	33	#include <lttngerr.h>
	34
d5bd7573	35	#define CHILD_STACK_SIZE 10485760
c2b75c49 MD	36
	37	struct run_as_data {
	38	int (cmd)(void data);
	39	void *data;
	40	uid_t uid;
	41	gid_t gid;
	42	int retval_pipe;
	43	};
	44
60b6c79c MD	45	struct mkdir_data {
	46	const char *path;
	47	mode_t mode;
	48	};
	49
	50	struct open_data {
	51	const char *path;
	52	int flags;
	53	mode_t mode;
	54	};
	55
	56	/*
	57	* Create recursively directory using the FULL path.
	58	*/
	59	static
	60	int _mkdir_recursive(void *_data)
	61	{
	62	struct mkdir_data *data = _data;
	63	const char *path;
	64	char *p, tmp[PATH_MAX];
	65	struct stat statbuf;
	66	mode_t mode;
	67	size_t len;
	68	int ret;
	69
	70	path = data->path;
	71	mode = data->mode;
	72
	73	ret = snprintf(tmp, sizeof(tmp), "%s", path);
	74	if (ret < 0) {
	75	PERROR("snprintf mkdir");
	76	goto error;
	77	}
	78
	79	len = ret;
	80	if (tmp[len - 1] == '/') {
	81	tmp[len - 1] = 0;
	82	}
	83
	84	for (p = tmp + 1; *p; p++) {
	85	if (*p == '/') {
	86	*p = 0;
	87	ret = stat(tmp, &statbuf);
	88	if (ret < 0) {
	89	ret = mkdir(tmp, mode);
	90	if (ret < 0) {
	91	if (!(errno == EEXIST)) {
	92	PERROR("mkdir recursive");
	93	ret = -errno;
	94	goto error;
	95	}
	96	}
	97	}
	98	*p = '/';
	99	}
	100	}
	101
	102	ret = mkdir(tmp, mode);
	103	if (ret < 0) {
	104	if (!(errno == EEXIST)) {
	105	PERROR("mkdir recursive last piece");
	106	ret = -errno;
	107	} else {
	108	ret = 0;
109	}
110	}
111
112	error:
113	return ret;
114	}
115
116	static
117	int _mkdir(void *_data)
118	{
119	struct mkdir_data *data = _data;
120	return mkdir(data->path, data->mode);
121	}
122
123	static
124	int _open(void *_data)
125	{
126	struct open_data *data = _data;
127	return open(data->path, data->flags, data->mode);
128	}
129
c2b75c49 MD	130	static
	131	int child_run_as(void *_data)
	132	{
	133	struct run_as_data *data = _data;
	134	size_t writelen, writeleft, index;
	135	union {
	136	int i;
	137	char c[sizeof(int)];
	138	} sendret;
	139	int ret;
	140
	141	/*
	142	* Child: it is safe to drop egid and euid while sharing the
	143	* file descriptors with the parent process, since we do not
	144	* drop "uid": therefore, the user we are dropping egid/euid to
	145	* cannot attach to this process with, e.g. ptrace, nor map this
	146	* process memory.
	147	*/
1576d582 MD	148	if (data->gid != getegid()) {
	149	ret = setegid(data->gid);
	150	if (ret < 0) {
	151	perror("setegid");
	152	exit(EXIT_FAILURE);
	153	}
c2b75c49	154	}
1576d582 MD	155	if (data->uid != geteuid()) {
	156	ret = seteuid(data->uid);
	157	if (ret < 0) {
	158	perror("seteuid");
	159	exit(EXIT_FAILURE);
	160	}
c2b75c49 MD	161	}
	162	/*
	163	* Also set umask to 0 for mkdir executable bit.
	164	*/
	165	umask(0);
	166	sendret.i = (*data->cmd)(data->data);
	167	/* send back return value */
	168	writeleft = sizeof(sendret);
	169	index = 0;
	170	do {
	171	writelen = write(data->retval_pipe, &sendret.c[index],
	172	writeleft);
	173	if (writelen < 0) {
	174	perror("write");
	175	exit(EXIT_FAILURE);
	176	}
	177	writeleft -= writelen;
	178	index += writelen;
	179	} while (writeleft > 0);
	180
	181	exit(EXIT_SUCCESS);
	182	}
	183
60b6c79c MD	184	static
	185	int run_as(int (cmd)(void data), void *data, uid_t uid, gid_t gid)
	186	{
c2b75c49	187	struct run_as_data run_as_data;
60b6c79c	188	int ret = 0;
c2b75c49	189	int status;
60b6c79c	190	pid_t pid;
c2b75c49 MD	191	int retval_pipe[2];
c2b75c49 MD	192	ssize_t readlen, readleft, index;
d5bd7573	193	void *child_stack;
c2b75c49 MD	194	union {
	195	int i;
	196	char c[sizeof(int)];
	197	} retval;
60b6c79c MD	198
	199	/*
	200	* If we are non-root, we can only deal with our own uid.
	201	*/
	202	if (geteuid() != 0) {
	203	if (uid != geteuid()) {
	204	ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
	205	uid, geteuid());
	206	return -EPERM;
	207	}
60b6c79c MD	208	}
60b6c79c MD	209
c2b75c49 MD	210	ret = pipe(retval_pipe);
	211	if (ret < 0) {
	212	perror("pipe");
60b6c79c	213	goto end;
c2b75c49 MD	214	}
	215	run_as_data.data = data;
	216	run_as_data.cmd = cmd;
	217	run_as_data.uid = uid;
	218	run_as_data.gid = gid;
	219	run_as_data.retval_pipe = retval_pipe[1]; /* write end */
d5bd7573 MD	220	child_stack = mmap(NULL, CHILD_STACK_SIZE,
	221	PROT_WRITE \| PROT_READ,
	222	MAP_PRIVATE \| MAP_GROWSDOWN \| MAP_ANONYMOUS \| MAP_STACK,
	223	-1, 0);
	224	if (child_stack == MAP_FAILED) {
	225	perror("mmap");
	226	ret = -ENOMEM;
	227	goto close_pipe;
	228	}
	229	/*
	230	* Pointing to the middle of the stack to support architectures
	231	* where the stack grows up (HPPA).
	232	*/
	233	pid = clone(child_run_as, child_stack + (CHILD_STACK_SIZE / 2),
	234	CLONE_FILES \| SIGCHLD,
	235	&run_as_data, NULL);
c2b75c49 MD	236	if (pid < 0) {
	237	perror("clone");
	238	ret = pid;
d5bd7573	239	goto unmap_stack;
c2b75c49 MD	240	}
	241	/* receive return value */
	242	readleft = sizeof(retval);
	243	index = 0;
	244	do {
	245	readlen = read(retval_pipe[0], &retval.c[index], readleft);
	246	if (readlen < 0) {
	247	perror("read");
	248	ret = -1;
	249	break;
60b6c79c	250	}
c2b75c49 MD	251	readleft -= readlen;
	252	index += readlen;
	253	} while (readleft > 0);
	254
	255	/*
	256	* Parent: wait for child to return, in which case the
	257	* shared memory map will have been created.
	258	*/
	259	pid = wait(&status);
	260	if (pid < 0 \|\| !WIFEXITED(status) \|\| WEXITSTATUS(status) != 0) {
	261	perror("wait");
	262	ret = -1;
60b6c79c	263	}
d5bd7573 MD	264	unmap_stack:
	265	ret = munmap(child_stack, CHILD_STACK_SIZE);
	266	if (ret < 0) {
	267	perror("munmap");
	268	}
c2b75c49 MD	269	close_pipe:
	270	close(retval_pipe[0]);
	271	close(retval_pipe[1]);
60b6c79c	272	end:
c2b75c49	273	return retval.i;
60b6c79c MD	274	}
	275
	276	int mkdir_recursive_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
	277	{
	278	struct mkdir_data data;
	279
	280	DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
	281	path, mode, uid, gid);
	282	data.path = path;
	283	data.mode = mode;
	284	return run_as(_mkdir_recursive, &data, uid, gid);
	285	}
	286
	287	int mkdir_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
	288	{
	289	struct mkdir_data data;
	290
	291	DBG3("mkdir() %s with mode %d for uid %d and gid %d",
	292	path, mode, uid, gid);
	293	data.path = path;
	294	data.mode = mode;
	295	return run_as(_mkdir, &data, uid, gid);
	296	}
	297
	298	/*
	299	* Note: open_run_as is currently not working. We'd need to pass the fd
	300	* opened in the child to the parent.
	301	*/
	302	int open_run_as(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
	303	{
c2b75c49 MD	304	struct open_data data;
c2b75c49 MD	305
60b6c79c MD	306	data.path = path;
	307	data.flags = flags;
	308	data.mode = mode;
	309	return run_as(_open, &data, uid, gid);
60b6c79c	310	}