| 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 |
| 11 | #include <common/macros.h> |
| 12 | #include <common/common.h> |
| 13 | #include <common/path.h> |
| 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 | */ |
| 24 | static |
| 25 | char *utils_partial_realpath(const char *path) |
| 26 | { |
| 27 | char *cut_path = NULL, *try_path = NULL, *try_path_prev = NULL; |
| 28 | const char *next, *prev, *end; |
| 29 | char *resolved_path = NULL; |
| 30 | |
| 31 | /* Safety net */ |
| 32 | if (path == NULL) { |
| 33 | goto error; |
| 34 | } |
| 35 | |
| 36 | /* |
| 37 | * Identify the end of the path, we don't want to treat the |
| 38 | * last char if it is a '/', we will just keep it on the side |
| 39 | * to be added at the end, and return a value coherent with |
| 40 | * the path given as argument |
| 41 | */ |
| 42 | end = path + strlen(path); |
| 43 | if (*(end-1) == '/') { |
| 44 | end--; |
| 45 | } |
| 46 | |
| 47 | /* Initiate the values of the pointers before looping */ |
| 48 | next = path; |
| 49 | prev = next; |
| 50 | /* Only to ensure try_path is not NULL to enter the while */ |
| 51 | try_path = (char *)next; |
| 52 | |
| 53 | /* Resolve the canonical path of the first part of the path */ |
| 54 | while (try_path != NULL && next != end) { |
| 55 | char *try_path_buf = NULL; |
| 56 | |
| 57 | /* |
| 58 | * If there is not any '/' left, we want to try with |
| 59 | * the full path |
| 60 | */ |
| 61 | next = strpbrk(next + 1, "/"); |
| 62 | if (next == NULL) { |
| 63 | next = end; |
| 64 | } |
| 65 | |
| 66 | /* Cut the part we will be trying to resolve */ |
| 67 | cut_path = lttng_strndup(path, next - path); |
| 68 | if (cut_path == NULL) { |
| 69 | PERROR("lttng_strndup"); |
| 70 | goto error; |
| 71 | } |
| 72 | |
| 73 | try_path_buf = (char *) zmalloc(LTTNG_PATH_MAX); |
| 74 | if (!try_path_buf) { |
| 75 | PERROR("zmalloc"); |
| 76 | goto error; |
| 77 | } |
| 78 | |
| 79 | /* Try to resolve this part */ |
| 80 | try_path = realpath((char *) cut_path, try_path_buf); |
| 81 | if (try_path == NULL) { |
| 82 | free(try_path_buf); |
| 83 | /* |
| 84 | * There was an error, we just want to be assured it |
| 85 | * is linked to an unexistent directory, if it's another |
| 86 | * reason, we spawn an error |
| 87 | */ |
| 88 | switch (errno) { |
| 89 | case ENOENT: |
| 90 | /* Ignore the error */ |
| 91 | break; |
| 92 | default: |
| 93 | PERROR("realpath (partial_realpath)"); |
| 94 | goto error; |
| 95 | break; |
| 96 | } |
| 97 | } else { |
| 98 | /* Save the place we are before trying the next step */ |
| 99 | try_path_buf = NULL; |
| 100 | free(try_path_prev); |
| 101 | try_path_prev = try_path; |
| 102 | prev = next; |
| 103 | } |
| 104 | |
| 105 | /* Free the allocated memory */ |
| 106 | free(cut_path); |
| 107 | cut_path = NULL; |
| 108 | } |
| 109 | |
| 110 | /* Allocate memory for the resolved path. */ |
| 111 | resolved_path = (char *) zmalloc(LTTNG_PATH_MAX); |
| 112 | if (resolved_path == NULL) { |
| 113 | PERROR("zmalloc resolved path"); |
| 114 | goto error; |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * If we were able to solve at least partially the path, we can concatenate |
| 119 | * what worked and what didn't work |
| 120 | */ |
| 121 | if (try_path_prev != NULL) { |
| 122 | /* If we risk to concatenate two '/', we remove one of them */ |
| 123 | if (try_path_prev[strlen(try_path_prev) - 1] == '/' && prev[0] == '/') { |
| 124 | try_path_prev[strlen(try_path_prev) - 1] = '\0'; |
| 125 | } |
| 126 | |
| 127 | /* |
| 128 | * Duplicate the memory used by prev in case resolved_path and |
| 129 | * path are pointers for the same memory space |
| 130 | */ |
| 131 | cut_path = strdup(prev); |
| 132 | if (cut_path == NULL) { |
| 133 | PERROR("strdup"); |
| 134 | goto error; |
| 135 | } |
| 136 | |
| 137 | /* Concatenate the strings */ |
| 138 | snprintf(resolved_path, LTTNG_PATH_MAX, "%s%s", |
| 139 | try_path_prev, cut_path); |
| 140 | |
| 141 | /* Free the allocated memory */ |
| 142 | free(cut_path); |
| 143 | free(try_path_prev); |
| 144 | cut_path = NULL; |
| 145 | try_path_prev = NULL; |
| 146 | /* |
| 147 | * Else, we just copy the path in our resolved_path to |
| 148 | * return it as is |
| 149 | */ |
| 150 | } else { |
| 151 | strncpy(resolved_path, path, LTTNG_PATH_MAX); |
| 152 | } |
| 153 | |
| 154 | /* Then we return the 'partially' resolved path */ |
| 155 | return resolved_path; |
| 156 | |
| 157 | error: |
| 158 | free(resolved_path); |
| 159 | free(cut_path); |
| 160 | free(try_path); |
| 161 | if (try_path_prev != try_path) { |
| 162 | free(try_path_prev); |
| 163 | } |
| 164 | return NULL; |
| 165 | } |
| 166 | |
| 167 | static |
| 168 | int expand_double_slashes_dot_and_dotdot(char *path) |
| 169 | { |
| 170 | size_t expanded_path_len, path_len; |
| 171 | const char *curr_char, *path_last_char, *next_slash, *prev_slash; |
| 172 | |
| 173 | path_len = strlen(path); |
| 174 | path_last_char = &path[path_len]; |
| 175 | |
| 176 | if (path_len == 0) { |
| 177 | goto error; |
| 178 | } |
| 179 | |
| 180 | expanded_path_len = 0; |
| 181 | |
| 182 | /* We iterate over the provided path to expand the "//", "../" and "./" */ |
| 183 | for (curr_char = path; curr_char <= path_last_char; curr_char = next_slash + 1) { |
| 184 | /* Find the next forward slash. */ |
| 185 | size_t curr_token_len; |
| 186 | |
| 187 | if (curr_char == path_last_char) { |
| 188 | expanded_path_len++; |
| 189 | break; |
| 190 | } |
| 191 | |
| 192 | next_slash = (const char *) memchr(curr_char, '/', path_last_char - curr_char); |
| 193 | if (next_slash == NULL) { |
| 194 | /* Reached the end of the provided path. */ |
| 195 | next_slash = path_last_char; |
| 196 | } |
| 197 | |
| 198 | /* Compute how long is the previous token. */ |
| 199 | curr_token_len = next_slash - curr_char; |
| 200 | switch(curr_token_len) { |
| 201 | case 0: |
| 202 | /* |
| 203 | * The pointer has not move meaning that curr_char is |
| 204 | * pointing to a slash. It that case there is no token |
| 205 | * to copy, so continue the iteration to find the next |
| 206 | * token |
| 207 | */ |
| 208 | continue; |
| 209 | case 1: |
| 210 | /* |
| 211 | * The pointer moved 1 character. Check if that |
| 212 | * character is a dot ('.'), if it is: omit it, else |
| 213 | * copy the token to the normalized path. |
| 214 | */ |
| 215 | if (curr_char[0] == '.') { |
| 216 | continue; |
| 217 | } |
| 218 | break; |
| 219 | case 2: |
| 220 | /* |
| 221 | * The pointer moved 2 characters. Check if these |
| 222 | * characters are double dots ('..'). If that is the |
| 223 | * case, we need to remove the last token of the |
| 224 | * normalized path. |
| 225 | */ |
| 226 | if (curr_char[0] == '.' && curr_char[1] == '.') { |
| 227 | /* |
| 228 | * Find the previous path component by |
| 229 | * using the memrchr function to find the |
| 230 | * previous forward slash and substract that |
| 231 | * len to the resulting path. |
| 232 | */ |
| 233 | prev_slash = (const char *) lttng_memrchr(path, '/', expanded_path_len); |
| 234 | /* |
| 235 | * If prev_slash is NULL, we reached the |
| 236 | * beginning of the path. We can't go back any |
| 237 | * further. |
| 238 | */ |
| 239 | if (prev_slash != NULL) { |
| 240 | expanded_path_len = prev_slash - path; |
| 241 | } |
| 242 | continue; |
| 243 | } |
| 244 | break; |
| 245 | default: |
| 246 | break; |
| 247 | } |
| 248 | |
| 249 | /* |
| 250 | * Copy the current token which is neither a '.' nor a '..'. |
| 251 | */ |
| 252 | path[expanded_path_len++] = '/'; |
| 253 | memmove(&path[expanded_path_len], curr_char, curr_token_len); |
| 254 | expanded_path_len += curr_token_len; |
| 255 | } |
| 256 | |
| 257 | if (expanded_path_len == 0) { |
| 258 | path[expanded_path_len++] = '/'; |
| 259 | } |
| 260 | |
| 261 | path[expanded_path_len] = '\0'; |
| 262 | return 0; |
| 263 | error: |
| 264 | return -1; |
| 265 | } |
| 266 | |
| 267 | /* |
| 268 | * Make a full resolution of the given path even if it doesn't exist. |
| 269 | * This function uses the utils_partial_realpath function to resolve |
| 270 | * symlinks and relatives paths at the start of the string, and |
| 271 | * implements functionnalities to resolve the './' and '../' strings |
| 272 | * in the middle of a path. This function is only necessary because |
| 273 | * realpath(3) does not accept to resolve unexistent paths. |
| 274 | * The returned string was allocated in the function, it is thus of |
| 275 | * the responsibility of the caller to free this memory. |
| 276 | */ |
| 277 | static |
| 278 | char *_utils_expand_path(const char *path, bool keep_symlink) |
| 279 | { |
| 280 | int ret; |
| 281 | char *absolute_path = NULL; |
| 282 | char *last_token; |
| 283 | bool is_dot, is_dotdot; |
| 284 | |
| 285 | /* Safety net */ |
| 286 | if (path == NULL) { |
| 287 | goto error; |
| 288 | } |
| 289 | |
| 290 | /* Allocate memory for the absolute_path */ |
| 291 | absolute_path = (char *) zmalloc(LTTNG_PATH_MAX); |
| 292 | if (absolute_path == NULL) { |
| 293 | PERROR("zmalloc expand path"); |
| 294 | goto error; |
| 295 | } |
| 296 | |
| 297 | if (path[0] == '/') { |
| 298 | ret = lttng_strncpy(absolute_path, path, LTTNG_PATH_MAX); |
| 299 | if (ret) { |
| 300 | ERR("Path exceeds maximal size of %i bytes", LTTNG_PATH_MAX); |
| 301 | goto error; |
| 302 | } |
| 303 | } else { |
| 304 | /* |
| 305 | * This is a relative path. We need to get the present working |
| 306 | * directory and start the path walk from there. |
| 307 | */ |
| 308 | char current_working_dir[LTTNG_PATH_MAX]; |
| 309 | char *cwd_ret; |
| 310 | |
| 311 | cwd_ret = getcwd(current_working_dir, sizeof(current_working_dir)); |
| 312 | if (!cwd_ret) { |
| 313 | goto error; |
| 314 | } |
| 315 | /* |
| 316 | * Get the number of character in the CWD and allocate an array |
| 317 | * to can hold it and the path provided by the caller. |
| 318 | */ |
| 319 | ret = snprintf(absolute_path, LTTNG_PATH_MAX, "%s/%s", |
| 320 | current_working_dir, path); |
| 321 | if (ret >= LTTNG_PATH_MAX) { |
| 322 | ERR("Concatenating current working directory %s and path %s exceeds maximal size of %i bytes", |
| 323 | current_working_dir, path, LTTNG_PATH_MAX); |
| 324 | goto error; |
| 325 | } |
| 326 | } |
| 327 | |
| 328 | if (keep_symlink) { |
| 329 | /* Resolve partially our path */ |
| 330 | char *new_absolute_path = utils_partial_realpath(absolute_path); |
| 331 | if (!new_absolute_path) { |
| 332 | goto error; |
| 333 | } |
| 334 | |
| 335 | free(absolute_path); |
| 336 | absolute_path = new_absolute_path; |
| 337 | } |
| 338 | |
| 339 | ret = expand_double_slashes_dot_and_dotdot(absolute_path); |
| 340 | if (ret) { |
| 341 | goto error; |
| 342 | } |
| 343 | |
| 344 | /* Identify the last token */ |
| 345 | last_token = strrchr(absolute_path, '/'); |
| 346 | |
| 347 | /* Verify that this token is not a relative path */ |
| 348 | is_dotdot = (strcmp(last_token, "/..") == 0); |
| 349 | is_dot = (strcmp(last_token, "/.") == 0); |
| 350 | |
| 351 | /* If it is, take action */ |
| 352 | if (is_dot || is_dotdot) { |
| 353 | /* For both, remove this token */ |
| 354 | *last_token = '\0'; |
| 355 | |
| 356 | /* If it was a reference to parent directory, go back one more time */ |
| 357 | if (is_dotdot) { |
| 358 | last_token = strrchr(absolute_path, '/'); |
| 359 | |
| 360 | /* If there was only one level left, we keep the first '/' */ |
| 361 | if (last_token == absolute_path) { |
| 362 | last_token++; |
| 363 | } |
| 364 | |
| 365 | *last_token = '\0'; |
| 366 | } |
| 367 | } |
| 368 | |
| 369 | return absolute_path; |
| 370 | |
| 371 | error: |
| 372 | free(absolute_path); |
| 373 | return NULL; |
| 374 | } |
| 375 | char *utils_expand_path(const char *path) |
| 376 | { |
| 377 | return _utils_expand_path(path, true); |
| 378 | } |
| 379 | |
| 380 | char *utils_expand_path_keep_symlink(const char *path) |
| 381 | { |
| 382 | return _utils_expand_path(path, false); |
| 383 | } |