| 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/common.hpp> |
| 12 | #include <common/macros.hpp> |
| 13 | #include <common/path.hpp> |
| 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 char *utils_partial_realpath(const char *path) |
| 25 | { |
| 26 | char *cut_path = nullptr, *try_path = nullptr, *try_path_prev = nullptr; |
| 27 | const char *next, *prev, *end; |
| 28 | char *resolved_path = nullptr; |
| 29 | |
| 30 | /* Safety net */ |
| 31 | if (path == nullptr) { |
| 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); |
| 42 | if (*(end - 1) == '/') { |
| 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 */ |
| 50 | try_path = (char *) next; |
| 51 | |
| 52 | /* Resolve the canonical path of the first part of the path */ |
| 53 | while (try_path != nullptr && next != end) { |
| 54 | char *try_path_buf = nullptr; |
| 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 == nullptr) { |
| 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 == nullptr) { |
| 68 | PERROR("lttng_strndup"); |
| 69 | goto error; |
| 70 | } |
| 71 | |
| 72 | try_path_buf = zmalloc<char>(LTTNG_PATH_MAX); |
| 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 == nullptr) { |
| 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 = nullptr; |
| 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 = nullptr; |
| 107 | } |
| 108 | |
| 109 | /* Allocate memory for the resolved path. */ |
| 110 | resolved_path = zmalloc<char>(LTTNG_PATH_MAX); |
| 111 | if (resolved_path == nullptr) { |
| 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 != nullptr) { |
| 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 == nullptr) { |
| 132 | PERROR("strdup"); |
| 133 | goto error; |
| 134 | } |
| 135 | |
| 136 | /* Concatenate the strings */ |
| 137 | snprintf(resolved_path, LTTNG_PATH_MAX, "%s%s", try_path_prev, cut_path); |
| 138 | |
| 139 | /* Free the allocated memory */ |
| 140 | free(cut_path); |
| 141 | free(try_path_prev); |
| 142 | cut_path = nullptr; |
| 143 | try_path_prev = nullptr; |
| 144 | /* |
| 145 | * Else, we just copy the path in our resolved_path to |
| 146 | * return it as is |
| 147 | */ |
| 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 nullptr; |
| 163 | } |
| 164 | |
| 165 | static int expand_double_slashes_dot_and_dotdot(char *path) |
| 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 == nullptr) { |
| 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; |
| 197 | switch (curr_token_len) { |
| 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 | */ |
| 230 | prev_slash = |
| 231 | (const char *) lttng_memrchr(path, '/', expanded_path_len); |
| 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 != nullptr) { |
| 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 | */ |
| 275 | static char *_utils_expand_path(const char *path, bool keep_symlink) |
| 276 | { |
| 277 | int ret; |
| 278 | char *absolute_path = nullptr; |
| 279 | char *last_token; |
| 280 | bool is_dot, is_dotdot; |
| 281 | |
| 282 | /* Safety net */ |
| 283 | if (path == nullptr) { |
| 284 | goto error; |
| 285 | } |
| 286 | |
| 287 | /* Allocate memory for the absolute_path */ |
| 288 | absolute_path = zmalloc<char>(LTTNG_PATH_MAX); |
| 289 | if (absolute_path == nullptr) { |
| 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 | */ |
| 316 | ret = snprintf(absolute_path, LTTNG_PATH_MAX, "%s/%s", current_working_dir, path); |
| 317 | if (ret >= LTTNG_PATH_MAX) { |
| 318 | ERR("Concatenating current working directory %s and path %s exceeds maximal size of %i bytes", |
| 319 | current_working_dir, |
| 320 | path, |
| 321 | LTTNG_PATH_MAX); |
| 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 nullptr; |
| 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 | } |