[lttng-tools.git] / src / common / path.cpp

/*
 * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
 * Copyright (C) 2013 Raphaël Beamonte <raphael.beamonte@gmail.com>
 * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 * Copyright (C) 2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 */

#define _LGPL_SOURCE
#include <common/common.hpp>
#include <common/macros.hpp>
#include <common/path.hpp>

/*
 * Return a partial realpath(3) of the path even if the full path does not
 * exist. For instance, with /tmp/test1/test2/test3, if test2/ does not exist
 * but the /tmp/test1 does, the real path for /tmp/test1 is concatened with
 * /test2/test3 then returned. In normal time, realpath(3) fails if the end
 * point directory does not exist.
 *
 * Return a newly-allocated string.
 */
static char *utils_partial_realpath(const char *path)
{
	char *cut_path = NULL, *try_path = NULL, *try_path_prev = NULL;
	const char *next, *prev, *end;
	char *resolved_path = NULL;

	/* Safety net */
	if (path == NULL) {
		goto error;
	}

	/*
	 * Identify the end of the path, we don't want to treat the
	 * last char if it is a '/', we will just keep it on the side
	 * to be added at the end, and return a value coherent with
	 * the path given as argument
	 */
	end = path + strlen(path);
	if (*(end - 1) == '/') {
		end--;
	}

	/* Initiate the values of the pointers before looping */
	next = path;
	prev = next;
	/* Only to ensure try_path is not NULL to enter the while */
	try_path = (char *) next;

	/* Resolve the canonical path of the first part of the path */
	while (try_path != NULL && next != end) {
		char *try_path_buf = NULL;

		/*
		 * If there is not any '/' left, we want to try with
		 * the full path
		 */
		next = strpbrk(next + 1, "/");
		if (next == NULL) {
			next = end;
		}

		/* Cut the part we will be trying to resolve */
		cut_path = lttng_strndup(path, next - path);
		if (cut_path == NULL) {
			PERROR("lttng_strndup");
			goto error;
		}

		try_path_buf = zmalloc<char>(LTTNG_PATH_MAX);
		if (!try_path_buf) {
			PERROR("zmalloc");
			goto error;
		}

		/* Try to resolve this part */
		try_path = realpath((char *) cut_path, try_path_buf);
		if (try_path == NULL) {
			free(try_path_buf);
			/*
			 * There was an error, we just want to be assured it
			 * is linked to an unexistent directory, if it's another
			 * reason, we spawn an error
			 */
			switch (errno) {
			case ENOENT:
				/* Ignore the error */
				break;
			default:
				PERROR("realpath (partial_realpath)");
				goto error;
				break;
			}
		} else {
			/* Save the place we are before trying the next step */
			try_path_buf = NULL;
			free(try_path_prev);
			try_path_prev = try_path;
			prev = next;
		}

		/* Free the allocated memory */
		free(cut_path);
		cut_path = NULL;
	}

	/* Allocate memory for the resolved path. */
	resolved_path = zmalloc<char>(LTTNG_PATH_MAX);
	if (resolved_path == NULL) {
		PERROR("zmalloc resolved path");
		goto error;
	}

	/*
	 * If we were able to solve at least partially the path, we can concatenate
	 * what worked and what didn't work
	 */
	if (try_path_prev != NULL) {
		/* If we risk to concatenate two '/', we remove one of them */
		if (try_path_prev[strlen(try_path_prev) - 1] == '/' && prev[0] == '/') {
			try_path_prev[strlen(try_path_prev) - 1] = '\0';
		}

		/*
		 * Duplicate the memory used by prev in case resolved_path and
		 * path are pointers for the same memory space
		 */
		cut_path = strdup(prev);
		if (cut_path == NULL) {
			PERROR("strdup");
			goto error;
		}

		/* Concatenate the strings */
		snprintf(resolved_path, LTTNG_PATH_MAX, "%s%s", try_path_prev, cut_path);

		/* Free the allocated memory */
		free(cut_path);
		free(try_path_prev);
		cut_path = NULL;
		try_path_prev = NULL;
		/*
		 * Else, we just copy the path in our resolved_path to
		 * return it as is
		 */
	} else {
		strncpy(resolved_path, path, LTTNG_PATH_MAX);
	}

	/* Then we return the 'partially' resolved path */
	return resolved_path;

error:
	free(resolved_path);
	free(cut_path);
	free(try_path);
	if (try_path_prev != try_path) {
		free(try_path_prev);
	}
	return NULL;
}

static int expand_double_slashes_dot_and_dotdot(char *path)
{
	size_t expanded_path_len, path_len;
	const char *curr_char, *path_last_char, *next_slash, *prev_slash;

	path_len = strlen(path);
	path_last_char = &path[path_len];

	if (path_len == 0) {
		goto error;
	}

	expanded_path_len = 0;

	/* We iterate over the provided path to expand the "//", "../" and "./" */
	for (curr_char = path; curr_char <= path_last_char; curr_char = next_slash + 1) {
		/* Find the next forward slash. */
		size_t curr_token_len;

		if (curr_char == path_last_char) {
			expanded_path_len++;
			break;
		}

		next_slash = (const char *) memchr(curr_char, '/', path_last_char - curr_char);
		if (next_slash == NULL) {
			/* Reached the end of the provided path. */
			next_slash = path_last_char;
		}

		/* Compute how long is the previous token. */
		curr_token_len = next_slash - curr_char;
		switch (curr_token_len) {
		case 0:
			/*
			 * The pointer has not move meaning that curr_char is
			 * pointing to a slash. It that case there is no token
			 * to copy, so continue the iteration to find the next
			 * token
			 */
			continue;
		case 1:
			/*
			 * The pointer moved 1 character. Check if that
			 * character is a dot ('.'), if it is: omit it, else
			 * copy the token to the normalized path.
			 */
			if (curr_char[0] == '.') {
				continue;
			}
			break;
		case 2:
			/*
			 * The pointer moved 2 characters. Check if these
			 * characters are double dots ('..'). If that is the
			 * case, we need to remove the last token of the
			 * normalized path.
			 */
			if (curr_char[0] == '.' && curr_char[1] == '.') {
				/*
				 * Find the previous path component by
				 * using the memrchr function to find the
				 * previous forward slash and substract that
				 * len to the resulting path.
				 */
				prev_slash =
					(const char *) lttng_memrchr(path, '/', expanded_path_len);
				/*
				 * If prev_slash is NULL, we reached the
				 * beginning of the path. We can't go back any
				 * further.
				 */
				if (prev_slash != NULL) {
					expanded_path_len = prev_slash - path;
				}
				continue;
			}
			break;
		default:
			break;
		}

		/*
		 * Copy the current token which is neither a '.' nor a '..'.
		 */
		path[expanded_path_len++] = '/';
		memmove(&path[expanded_path_len], curr_char, curr_token_len);
		expanded_path_len += curr_token_len;
	}

	if (expanded_path_len == 0) {
		path[expanded_path_len++] = '/';
	}

	path[expanded_path_len] = '\0';
	return 0;
error:
	return -1;
}

/*
 * Make a full resolution of the given path even if it doesn't exist.
 * This function uses the utils_partial_realpath function to resolve
 * symlinks and relatives paths at the start of the string, and
 * implements functionnalities to resolve the './' and '../' strings
 * in the middle of a path. This function is only necessary because
 * realpath(3) does not accept to resolve unexistent paths.
 * The returned string was allocated in the function, it is thus of
 * the responsibility of the caller to free this memory.
 */
static char *_utils_expand_path(const char *path, bool keep_symlink)
{
	int ret;
	char *absolute_path = NULL;
	char *last_token;
	bool is_dot, is_dotdot;

	/* Safety net */
	if (path == NULL) {
		goto error;
	}

	/* Allocate memory for the absolute_path */
	absolute_path = zmalloc<char>(LTTNG_PATH_MAX);
	if (absolute_path == NULL) {
		PERROR("zmalloc expand path");
		goto error;
	}

	if (path[0] == '/') {
		ret = lttng_strncpy(absolute_path, path, LTTNG_PATH_MAX);
		if (ret) {
			ERR("Path exceeds maximal size of %i bytes", LTTNG_PATH_MAX);
			goto error;
		}
	} else {
		/*
		 * This is a relative path. We need to get the present working
		 * directory and start the path walk from there.
		 */
		char current_working_dir[LTTNG_PATH_MAX];
		char *cwd_ret;

		cwd_ret = getcwd(current_working_dir, sizeof(current_working_dir));
		if (!cwd_ret) {
			goto error;
		}
		/*
		 * Get the number of character in the CWD and allocate an array
		 * to can hold it and the path provided by the caller.
		 */
		ret = snprintf(absolute_path, LTTNG_PATH_MAX, "%s/%s", current_working_dir, path);
		if (ret >= LTTNG_PATH_MAX) {
			ERR("Concatenating current working directory %s and path %s exceeds maximal size of %i bytes",
			    current_working_dir,
			    path,
			    LTTNG_PATH_MAX);
			goto error;
		}
	}

	if (keep_symlink) {
		/* Resolve partially our path */
		char *new_absolute_path = utils_partial_realpath(absolute_path);
		if (!new_absolute_path) {
			goto error;
		}

		free(absolute_path);
		absolute_path = new_absolute_path;
	}

	ret = expand_double_slashes_dot_and_dotdot(absolute_path);
	if (ret) {
		goto error;
	}

	/* Identify the last token */
	last_token = strrchr(absolute_path, '/');

	/* Verify that this token is not a relative path */
	is_dotdot = (strcmp(last_token, "/..") == 0);
	is_dot = (strcmp(last_token, "/.") == 0);

	/* If it is, take action */
	if (is_dot || is_dotdot) {
		/* For both, remove this token */
		*last_token = '\0';

		/* If it was a reference to parent directory, go back one more time */
		if (is_dotdot) {
			last_token = strrchr(absolute_path, '/');

			/* If there was only one level left, we keep the first '/' */
			if (last_token == absolute_path) {
				last_token++;
			}

			*last_token = '\0';
		}
	}

	return absolute_path;

error:
	free(absolute_path);
	return NULL;
}
char *utils_expand_path(const char *path)
{
	return _utils_expand_path(path, true);
}

char *utils_expand_path_keep_symlink(const char *path)
{
	return _utils_expand_path(path, false);
}
Commit	Line	Data
4971b7f0 MD	1	/*
	2	* Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
	3	* Copyright (C) 2013 Raphaël Beamonte <raphael.beamonte@gmail.com>
	4	* Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
	5	* Copyright (C) 2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	6	*
	7	* SPDX-License-Identifier: GPL-2.0-only
	8	*/
	9
	10	#define _LGPL_SOURCE
c9e313bc	11	#include <common/common.hpp>
28ab034a	12	#include <common/macros.hpp>
c9e313bc	13	#include <common/path.hpp>
4971b7f0 MD	14
	15	/*
	16	* Return a partial realpath(3) of the path even if the full path does not
	17	* exist. For instance, with /tmp/test1/test2/test3, if test2/ does not exist
	18	* but the /tmp/test1 does, the real path for /tmp/test1 is concatened with
	19	* /test2/test3 then returned. In normal time, realpath(3) fails if the end
	20	* point directory does not exist.
	21	*
	22	* Return a newly-allocated string.
	23	*/
28ab034a	24	static char utils_partial_realpath(const char path)
4971b7f0 MD	25	{
	26	char cut_path = NULL, try_path = NULL, *try_path_prev = NULL;
	27	const char next, prev, *end;
	28	char *resolved_path = NULL;
	29
	30	/* Safety net */
	31	if (path == NULL) {
	32	goto error;
	33	}
	34
	35	/*
	36	* Identify the end of the path, we don't want to treat the
	37	* last char if it is a '/', we will just keep it on the side
	38	* to be added at the end, and return a value coherent with
	39	* the path given as argument
	40	*/
	41	end = path + strlen(path);
28ab034a	42	if (*(end - 1) == '/') {
4971b7f0 MD	43	end--;
	44	}
	45
	46	/* Initiate the values of the pointers before looping */
	47	next = path;
	48	prev = next;
	49	/* Only to ensure try_path is not NULL to enter the while */
28ab034a	50	try_path = (char *) next;
4971b7f0 MD	51
	52	/* Resolve the canonical path of the first part of the path */
	53	while (try_path != NULL && next != end) {
	54	char *try_path_buf = NULL;
	55
	56	/*
	57	* If there is not any '/' left, we want to try with
	58	* the full path
	59	*/
	60	next = strpbrk(next + 1, "/");
	61	if (next == NULL) {
	62	next = end;
	63	}
	64
	65	/* Cut the part we will be trying to resolve */
	66	cut_path = lttng_strndup(path, next - path);
	67	if (cut_path == NULL) {
	68	PERROR("lttng_strndup");
	69	goto error;
	70	}
	71
64803277	72	try_path_buf = zmalloc<char>(LTTNG_PATH_MAX);
4971b7f0 MD	73	if (!try_path_buf) {
	74	PERROR("zmalloc");
	75	goto error;
	76	}
	77
	78	/* Try to resolve this part */
	79	try_path = realpath((char *) cut_path, try_path_buf);
	80	if (try_path == NULL) {
	81	free(try_path_buf);
	82	/*
	83	* There was an error, we just want to be assured it
	84	* is linked to an unexistent directory, if it's another
	85	* reason, we spawn an error
	86	*/
	87	switch (errno) {
	88	case ENOENT:
	89	/* Ignore the error */
	90	break;
	91	default:
	92	PERROR("realpath (partial_realpath)");
	93	goto error;
	94	break;
	95	}
	96	} else {
	97	/* Save the place we are before trying the next step */
	98	try_path_buf = NULL;
	99	free(try_path_prev);
	100	try_path_prev = try_path;
	101	prev = next;
	102	}
	103
	104	/* Free the allocated memory */
	105	free(cut_path);
	106	cut_path = NULL;
	107	}
	108
	109	/* Allocate memory for the resolved path. */
64803277	110	resolved_path = zmalloc<char>(LTTNG_PATH_MAX);
4971b7f0 MD	111	if (resolved_path == NULL) {
	112	PERROR("zmalloc resolved path");
	113	goto error;
	114	}
	115
	116	/*
	117	* If we were able to solve at least partially the path, we can concatenate
	118	* what worked and what didn't work
	119	*/
	120	if (try_path_prev != NULL) {
	121	/* If we risk to concatenate two '/', we remove one of them */
	122	if (try_path_prev[strlen(try_path_prev) - 1] == '/' && prev[0] == '/') {
	123	try_path_prev[strlen(try_path_prev) - 1] = '\0';
	124	}
	125
	126	/*
	127	* Duplicate the memory used by prev in case resolved_path and
	128	* path are pointers for the same memory space
	129	*/
	130	cut_path = strdup(prev);
	131	if (cut_path == NULL) {
	132	PERROR("strdup");
	133	goto error;
	134	}
	135
	136	/* Concatenate the strings */
28ab034a	137	snprintf(resolved_path, LTTNG_PATH_MAX, "%s%s", try_path_prev, cut_path);
4971b7f0 MD	138
	139	/* Free the allocated memory */
	140	free(cut_path);
	141	free(try_path_prev);
	142	cut_path = NULL;
	143	try_path_prev = NULL;
28ab034a JG	144	/*
	145	* Else, we just copy the path in our resolved_path to
	146	* return it as is
	147	*/
4971b7f0 MD	148	} else {
	149	strncpy(resolved_path, path, LTTNG_PATH_MAX);
	150	}
	151
	152	/* Then we return the 'partially' resolved path */
	153	return resolved_path;
	154
	155	error:
	156	free(resolved_path);
	157	free(cut_path);
	158	free(try_path);
	159	if (try_path_prev != try_path) {
	160	free(try_path_prev);
	161	}
	162	return NULL;
	163	}
	164
28ab034a	165	static int expand_double_slashes_dot_and_dotdot(char *path)
4971b7f0 MD	166	{
	167	size_t expanded_path_len, path_len;
	168	const char curr_char, path_last_char, next_slash, prev_slash;
	169
	170	path_len = strlen(path);
	171	path_last_char = &path[path_len];
	172
	173	if (path_len == 0) {
	174	goto error;
	175	}
	176
	177	expanded_path_len = 0;
	178
	179	/* We iterate over the provided path to expand the "//", "../" and "./" */
	180	for (curr_char = path; curr_char <= path_last_char; curr_char = next_slash + 1) {
	181	/* Find the next forward slash. */
	182	size_t curr_token_len;
	183
	184	if (curr_char == path_last_char) {
	185	expanded_path_len++;
	186	break;
	187	}
	188
	189	next_slash = (const char *) memchr(curr_char, '/', path_last_char - curr_char);
	190	if (next_slash == NULL) {
	191	/* Reached the end of the provided path. */
	192	next_slash = path_last_char;
	193	}
	194
	195	/* Compute how long is the previous token. */
	196	curr_token_len = next_slash - curr_char;
28ab034a	197	switch (curr_token_len) {
4971b7f0 MD	198	case 0:
	199	/*
	200	* The pointer has not move meaning that curr_char is
	201	* pointing to a slash. It that case there is no token
	202	* to copy, so continue the iteration to find the next
	203	* token
	204	*/
	205	continue;
	206	case 1:
	207	/*
	208	* The pointer moved 1 character. Check if that
	209	* character is a dot ('.'), if it is: omit it, else
	210	* copy the token to the normalized path.
	211	*/
	212	if (curr_char[0] == '.') {
	213	continue;
	214	}
	215	break;
	216	case 2:
	217	/*
	218	* The pointer moved 2 characters. Check if these
	219	* characters are double dots ('..'). If that is the
	220	* case, we need to remove the last token of the
	221	* normalized path.
	222	*/
	223	if (curr_char[0] == '.' && curr_char[1] == '.') {
	224	/*
	225	* Find the previous path component by
	226	* using the memrchr function to find the
	227	* previous forward slash and substract that
	228	* len to the resulting path.
	229	*/
28ab034a JG	230	prev_slash =
28ab034a JG	231	(const char *) lttng_memrchr(path, '/', expanded_path_len);
4971b7f0 MD	232	/*
	233	* If prev_slash is NULL, we reached the
	234	* beginning of the path. We can't go back any
	235	* further.
	236	*/
	237	if (prev_slash != NULL) {
	238	expanded_path_len = prev_slash - path;
	239	}
	240	continue;
	241	}
	242	break;
	243	default:
	244	break;
	245	}
	246
	247	/*
	248	* Copy the current token which is neither a '.' nor a '..'.
	249	*/
	250	path[expanded_path_len++] = '/';
	251	memmove(&path[expanded_path_len], curr_char, curr_token_len);
	252	expanded_path_len += curr_token_len;
	253	}
	254
	255	if (expanded_path_len == 0) {
	256	path[expanded_path_len++] = '/';
	257	}
	258
	259	path[expanded_path_len] = '\0';
	260	return 0;
	261	error:
	262	return -1;
	263	}
	264
	265	/*
	266	* Make a full resolution of the given path even if it doesn't exist.
	267	* This function uses the utils_partial_realpath function to resolve
	268	* symlinks and relatives paths at the start of the string, and
	269	* implements functionnalities to resolve the './' and '../' strings
	270	* in the middle of a path. This function is only necessary because
	271	* realpath(3) does not accept to resolve unexistent paths.
	272	* The returned string was allocated in the function, it is thus of
	273	* the responsibility of the caller to free this memory.
	274	*/
28ab034a	275	static char _utils_expand_path(const char path, bool keep_symlink)
4971b7f0 MD	276	{
	277	int ret;
	278	char *absolute_path = NULL;
	279	char *last_token;
	280	bool is_dot, is_dotdot;
	281
	282	/* Safety net */
	283	if (path == NULL) {
	284	goto error;
	285	}
	286
	287	/* Allocate memory for the absolute_path */
64803277	288	absolute_path = zmalloc<char>(LTTNG_PATH_MAX);
4971b7f0 MD	289	if (absolute_path == NULL) {
	290	PERROR("zmalloc expand path");
	291	goto error;
	292	}
	293
	294	if (path[0] == '/') {
	295	ret = lttng_strncpy(absolute_path, path, LTTNG_PATH_MAX);
	296	if (ret) {
	297	ERR("Path exceeds maximal size of %i bytes", LTTNG_PATH_MAX);
	298	goto error;
	299	}
	300	} else {
	301	/*
	302	* This is a relative path. We need to get the present working
	303	* directory and start the path walk from there.
	304	*/
	305	char current_working_dir[LTTNG_PATH_MAX];
	306	char *cwd_ret;
	307
	308	cwd_ret = getcwd(current_working_dir, sizeof(current_working_dir));
	309	if (!cwd_ret) {
	310	goto error;
	311	}
	312	/*
	313	* Get the number of character in the CWD and allocate an array
	314	* to can hold it and the path provided by the caller.
	315	*/
28ab034a	316	ret = snprintf(absolute_path, LTTNG_PATH_MAX, "%s/%s", current_working_dir, path);
4971b7f0 MD	317	if (ret >= LTTNG_PATH_MAX) {
4971b7f0 MD	318	ERR("Concatenating current working directory %s and path %s exceeds maximal size of %i bytes",
28ab034a JG	319	current_working_dir,
	320	path,
	321	LTTNG_PATH_MAX);
4971b7f0 MD	322	goto error;
	323	}
	324	}
	325
	326	if (keep_symlink) {
	327	/* Resolve partially our path */
	328	char *new_absolute_path = utils_partial_realpath(absolute_path);
	329	if (!new_absolute_path) {
	330	goto error;
	331	}
	332
	333	free(absolute_path);
	334	absolute_path = new_absolute_path;
	335	}
	336
	337	ret = expand_double_slashes_dot_and_dotdot(absolute_path);
	338	if (ret) {
	339	goto error;
	340	}
	341
	342	/* Identify the last token */
	343	last_token = strrchr(absolute_path, '/');
	344
	345	/* Verify that this token is not a relative path */
	346	is_dotdot = (strcmp(last_token, "/..") == 0);
	347	is_dot = (strcmp(last_token, "/.") == 0);
	348
	349	/* If it is, take action */
	350	if (is_dot \|\| is_dotdot) {
	351	/* For both, remove this token */
	352	*last_token = '\0';
	353
	354	/* If it was a reference to parent directory, go back one more time */
	355	if (is_dotdot) {
	356	last_token = strrchr(absolute_path, '/');
	357
	358	/* If there was only one level left, we keep the first '/' */
	359	if (last_token == absolute_path) {
	360	last_token++;
	361	}
	362
	363	*last_token = '\0';
	364	}
	365	}
	366
	367	return absolute_path;
	368
	369	error:
	370	free(absolute_path);
	371	return NULL;
	372	}
	373	char utils_expand_path(const char path)
	374	{
	375	return _utils_expand_path(path, true);
	376	}
	377
	378	char utils_expand_path_keep_symlink(const char path)
	379	{
	380	return _utils_expand_path(path, false);
	381	}