| 1 | /* |
| 2 | * Copyright (C) 2019 - Jérémie Galarneau <jeremie.galarneau@efficios.com> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License, version 2 only, |
| 6 | * as published by the Free Software Foundation. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, but WITHOUT |
| 9 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 10 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
| 11 | * more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| 16 | */ |
| 17 | |
| 18 | #include <common/compat/directory-handle.h> |
| 19 | #include <common/error.h> |
| 20 | #include <common/macros.h> |
| 21 | #include <common/runas.h> |
| 22 | #include <common/credentials.h> |
| 23 | #include <lttng/constant.h> |
| 24 | |
| 25 | #include <assert.h> |
| 26 | #include <sys/types.h> |
| 27 | #include <sys/stat.h> |
| 28 | #include <fcntl.h> |
| 29 | #include <unistd.h> |
| 30 | |
| 31 | static |
| 32 | int lttng_directory_handle_stat(const struct lttng_directory_handle *handle, |
| 33 | const char *path, struct stat *st); |
| 34 | static |
| 35 | int lttng_directory_handle_mkdir( |
| 36 | const struct lttng_directory_handle *handle, |
| 37 | const char *path, mode_t mode); |
| 38 | static |
| 39 | int _run_as_mkdir(const struct lttng_directory_handle *handle, const char *path, |
| 40 | mode_t mode, uid_t uid, gid_t gid); |
| 41 | static |
| 42 | int _run_as_mkdir_recursive(const struct lttng_directory_handle *handle, |
| 43 | const char *path, mode_t mode, uid_t uid, gid_t gid); |
| 44 | |
| 45 | #ifdef COMPAT_DIRFD |
| 46 | |
| 47 | LTTNG_HIDDEN |
| 48 | int lttng_directory_handle_init(struct lttng_directory_handle *handle, |
| 49 | const char *path) |
| 50 | { |
| 51 | int ret; |
| 52 | |
| 53 | if (!path) { |
| 54 | handle->dirfd = AT_FDCWD; |
| 55 | ret = 0; |
| 56 | goto end; |
| 57 | } |
| 58 | ret = open(path, O_RDONLY | O_DIRECTORY | O_CLOEXEC); |
| 59 | if (ret == -1) { |
| 60 | PERROR("Failed to initialize directory handle to \"%s\"", path); |
| 61 | goto end; |
| 62 | } |
| 63 | handle->dirfd = ret; |
| 64 | ret = 0; |
| 65 | end: |
| 66 | return ret; |
| 67 | } |
| 68 | |
| 69 | LTTNG_HIDDEN |
| 70 | int lttng_directory_handle_init_from_dirfd( |
| 71 | struct lttng_directory_handle *handle, int dirfd) |
| 72 | { |
| 73 | handle->dirfd = dirfd; |
| 74 | return 0; |
| 75 | } |
| 76 | |
| 77 | LTTNG_HIDDEN |
| 78 | void lttng_directory_handle_fini(struct lttng_directory_handle *handle) |
| 79 | { |
| 80 | int ret; |
| 81 | |
| 82 | if (handle->dirfd == AT_FDCWD) { |
| 83 | return; |
| 84 | } |
| 85 | ret = close(handle->dirfd); |
| 86 | if (ret == -1) { |
| 87 | PERROR("Failed to close directory file descriptor of directory handle"); |
| 88 | } |
| 89 | } |
| 90 | |
| 91 | static |
| 92 | int lttng_directory_handle_stat(const struct lttng_directory_handle *handle, |
| 93 | const char *path, struct stat *st) |
| 94 | { |
| 95 | return fstatat(handle->dirfd, path, st, 0); |
| 96 | } |
| 97 | |
| 98 | static |
| 99 | int lttng_directory_handle_mkdir( |
| 100 | const struct lttng_directory_handle *handle, |
| 101 | const char *path, mode_t mode) |
| 102 | { |
| 103 | return mkdirat(handle->dirfd, path, mode); |
| 104 | } |
| 105 | |
| 106 | static |
| 107 | int _run_as_mkdir(const struct lttng_directory_handle *handle, const char *path, |
| 108 | mode_t mode, uid_t uid, gid_t gid) |
| 109 | { |
| 110 | return run_as_mkdirat(handle->dirfd, path, mode, uid, gid); |
| 111 | } |
| 112 | |
| 113 | static |
| 114 | int _run_as_mkdir_recursive(const struct lttng_directory_handle *handle, |
| 115 | const char *path, mode_t mode, uid_t uid, gid_t gid) |
| 116 | { |
| 117 | return run_as_mkdirat_recursive(handle->dirfd, path, mode, uid, gid); |
| 118 | } |
| 119 | |
| 120 | #else /* COMPAT_DIRFD */ |
| 121 | |
| 122 | LTTNG_HIDDEN |
| 123 | int lttng_directory_handle_init(struct lttng_directory_handle *handle, |
| 124 | const char *path) |
| 125 | { |
| 126 | int ret; |
| 127 | size_t cwd_len, path_len, handle_path_len; |
| 128 | char cwd_buf[LTTNG_PATH_MAX]; |
| 129 | const char *cwd; |
| 130 | bool add_slash = false; |
| 131 | struct stat stat_buf; |
| 132 | |
| 133 | cwd = getcwd(cwd_buf, sizeof(cwd_buf)); |
| 134 | if (!cwd) { |
| 135 | PERROR("Failed to initialize directory handle, can't get current working directory"); |
| 136 | ret = -1; |
| 137 | goto end; |
| 138 | } |
| 139 | cwd_len = strlen(cwd); |
| 140 | if (cwd_len == 0) { |
| 141 | ERR("Failed to initialize directory handle to \"%s\": getcwd() returned an empty string", |
| 142 | path); |
| 143 | ret = -1; |
| 144 | goto end; |
| 145 | } |
| 146 | if (cwd[cwd_len - 1] != '/') { |
| 147 | add_slash = true; |
| 148 | } |
| 149 | |
| 150 | if (path) { |
| 151 | path_len = strlen(path); |
| 152 | if (path_len == 0) { |
| 153 | ERR("Failed to initialize directory handle: provided path is an empty string"); |
| 154 | ret = -1; |
| 155 | goto end; |
| 156 | } |
| 157 | |
| 158 | /* |
| 159 | * Ensure that 'path' is a directory. There is a race |
| 160 | * (TOCTOU) since the directory could be removed/replaced/renamed, |
| 161 | * but this is inevitable on platforms that don't provide dirfd support. |
| 162 | */ |
| 163 | ret = stat(path, &stat_buf); |
| 164 | if (ret == -1) { |
| 165 | PERROR("Failed to initialize directory handle to \"%s\", stat() failed", |
| 166 | path); |
| 167 | goto end; |
| 168 | } |
| 169 | if (!S_ISDIR(stat_buf.st_mode)) { |
| 170 | ERR("Failed to initialize directory handle to \"%s\": not a directory", |
| 171 | path); |
| 172 | ret = -1; |
| 173 | goto end; |
| 174 | } |
| 175 | if (*path == '/') { |
| 176 | handle->base_path = strdup(path); |
| 177 | if (!handle->base_path) { |
| 178 | ret = -1; |
| 179 | } |
| 180 | /* Not an error. */ |
| 181 | goto end; |
| 182 | } |
| 183 | } else { |
| 184 | path = ""; |
| 185 | path_len = 0; |
| 186 | add_slash = false; |
| 187 | } |
| 188 | |
| 189 | handle_path_len = cwd_len + path_len + !!add_slash + 2; |
| 190 | if (handle_path_len >= LTTNG_PATH_MAX) { |
| 191 | ERR("Failed to initialize directory handle as the resulting path's length (%zu bytes) exceeds the maximal allowed length (%d bytes)", |
| 192 | handle_path_len, LTTNG_PATH_MAX); |
| 193 | ret = -1; |
| 194 | goto end; |
| 195 | } |
| 196 | handle->base_path = zmalloc(handle_path_len); |
| 197 | if (!handle->base_path) { |
| 198 | PERROR("Failed to initialize directory handle"); |
| 199 | ret = -1; |
| 200 | goto end; |
| 201 | } |
| 202 | |
| 203 | ret = sprintf(handle->base_path, "%s%s%s/", cwd, |
| 204 | add_slash ? "/" : "", path); |
| 205 | if (ret == -1 || ret >= handle_path_len) { |
| 206 | ERR("Failed to initialize directory handle: path formatting failed"); |
| 207 | ret = -1; |
| 208 | goto end; |
| 209 | } |
| 210 | end: |
| 211 | return ret; |
| 212 | } |
| 213 | |
| 214 | LTTNG_HIDDEN |
| 215 | int lttng_directory_handle_init_from_dirfd( |
| 216 | struct lttng_directory_handle *handle, int dirfd) |
| 217 | { |
| 218 | assert(dirfd == AT_FDCWD); |
| 219 | return lttng_directory_handle_init(handle, NULL); |
| 220 | } |
| 221 | |
| 222 | LTTNG_HIDDEN |
| 223 | void lttng_directory_handle_fini(struct lttng_directory_handle *handle) |
| 224 | { |
| 225 | free(handle->base_path); |
| 226 | } |
| 227 | |
| 228 | static |
| 229 | int get_full_path(const struct lttng_directory_handle *handle, |
| 230 | const char *subdirectory, char *fullpath, size_t size) |
| 231 | { |
| 232 | int ret; |
| 233 | |
| 234 | /* |
| 235 | * Don't include the base path if subdirectory is absolute. |
| 236 | * This is the same behaviour than mkdirat. |
| 237 | */ |
| 238 | ret = snprintf(fullpath, size, "%s%s", |
| 239 | *subdirectory != '/' ? handle->base_path : "", |
| 240 | subdirectory); |
| 241 | if (ret == -1 || ret >= size) { |
| 242 | ERR("Failed to format subdirectory from directory handle"); |
| 243 | ret = -1; |
| 244 | } |
| 245 | ret = 0; |
| 246 | return ret; |
| 247 | } |
| 248 | |
| 249 | static |
| 250 | int lttng_directory_handle_stat(const struct lttng_directory_handle *handle, |
| 251 | const char *subdirectory, struct stat *st) |
| 252 | { |
| 253 | int ret; |
| 254 | char fullpath[LTTNG_PATH_MAX]; |
| 255 | |
| 256 | ret = get_full_path(handle, subdirectory, fullpath, sizeof(fullpath)); |
| 257 | if (ret) { |
| 258 | errno = ENOMEM; |
| 259 | goto end; |
| 260 | } |
| 261 | |
| 262 | ret = stat(fullpath, st); |
| 263 | end: |
| 264 | return ret; |
| 265 | } |
| 266 | |
| 267 | static |
| 268 | int lttng_directory_handle_mkdir(const struct lttng_directory_handle *handle, |
| 269 | const char *subdirectory, mode_t mode) |
| 270 | { |
| 271 | int ret; |
| 272 | char fullpath[LTTNG_PATH_MAX]; |
| 273 | |
| 274 | ret = get_full_path(handle, subdirectory, fullpath, sizeof(fullpath)); |
| 275 | if (ret) { |
| 276 | errno = ENOMEM; |
| 277 | goto end; |
| 278 | } |
| 279 | |
| 280 | ret = mkdir(fullpath, mode); |
| 281 | end: |
| 282 | return ret; |
| 283 | } |
| 284 | |
| 285 | static |
| 286 | int _run_as_mkdir(const struct lttng_directory_handle *handle, const char *path, |
| 287 | mode_t mode, uid_t uid, gid_t gid) |
| 288 | { |
| 289 | int ret; |
| 290 | char fullpath[LTTNG_PATH_MAX]; |
| 291 | |
| 292 | ret = get_full_path(handle, path, fullpath, sizeof(fullpath)); |
| 293 | if (ret) { |
| 294 | errno = ENOMEM; |
| 295 | goto end; |
| 296 | } |
| 297 | |
| 298 | ret = run_as_mkdir(fullpath, mode, uid, gid); |
| 299 | end: |
| 300 | return ret; |
| 301 | } |
| 302 | |
| 303 | static |
| 304 | int _run_as_mkdir_recursive(const struct lttng_directory_handle *handle, |
| 305 | const char *path, mode_t mode, uid_t uid, gid_t gid) |
| 306 | { |
| 307 | int ret; |
| 308 | char fullpath[LTTNG_PATH_MAX]; |
| 309 | |
| 310 | ret = get_full_path(handle, path, fullpath, sizeof(fullpath)); |
| 311 | if (ret) { |
| 312 | errno = ENOMEM; |
| 313 | goto end; |
| 314 | } |
| 315 | |
| 316 | ret = run_as_mkdir_recursive(fullpath, mode, uid, gid); |
| 317 | end: |
| 318 | return ret; |
| 319 | } |
| 320 | |
| 321 | #endif /* COMPAT_DIRFD */ |
| 322 | |
| 323 | /* |
| 324 | * On some filesystems (e.g. nfs), mkdir will validate access rights before |
| 325 | * checking for the existence of the path element. This means that on a setup |
| 326 | * where "/home/" is a mounted NFS share, and running as an unpriviledged user, |
| 327 | * recursively creating a path of the form "/home/my_user/trace/" will fail with |
| 328 | * EACCES on mkdir("/home", ...). |
| 329 | * |
| 330 | * Checking the path for existence allows us to work around this behaviour. |
| 331 | */ |
| 332 | static |
| 333 | int create_directory_check_exists(const struct lttng_directory_handle *handle, |
| 334 | const char *path, mode_t mode) |
| 335 | { |
| 336 | int ret = 0; |
| 337 | struct stat st; |
| 338 | |
| 339 | ret = lttng_directory_handle_stat(handle, path, &st); |
| 340 | if (ret == 0) { |
| 341 | if (S_ISDIR(st.st_mode)) { |
| 342 | /* Directory exists, skip. */ |
| 343 | goto end; |
| 344 | } else { |
| 345 | /* Exists, but is not a directory. */ |
| 346 | errno = ENOTDIR; |
| 347 | ret = -1; |
| 348 | goto end; |
| 349 | } |
| 350 | } |
| 351 | |
| 352 | /* |
| 353 | * Let mkdir handle other errors as the caller expects mkdir |
| 354 | * semantics. |
| 355 | */ |
| 356 | ret = lttng_directory_handle_mkdir(handle, path, mode); |
| 357 | end: |
| 358 | return ret; |
| 359 | } |
| 360 | |
| 361 | /* Common implementation. */ |
| 362 | static |
| 363 | int create_directory_recursive(const struct lttng_directory_handle *handle, |
| 364 | const char *path, mode_t mode) |
| 365 | { |
| 366 | char *p, tmp[LTTNG_PATH_MAX]; |
| 367 | size_t len; |
| 368 | int ret; |
| 369 | |
| 370 | assert(path); |
| 371 | |
| 372 | ret = lttng_strncpy(tmp, path, sizeof(tmp)); |
| 373 | if (ret) { |
| 374 | ERR("Failed to create directory: provided path's length (%zu bytes) exceeds the maximal allowed length (%zu bytes)", |
| 375 | strlen(path) + 1, sizeof(tmp)); |
| 376 | goto error; |
| 377 | } |
| 378 | |
| 379 | len = strlen(path); |
| 380 | if (tmp[len - 1] == '/') { |
| 381 | tmp[len - 1] = 0; |
| 382 | } |
| 383 | |
| 384 | for (p = tmp + 1; *p; p++) { |
| 385 | if (*p == '/') { |
| 386 | *p = 0; |
| 387 | if (tmp[strlen(tmp) - 1] == '.' && |
| 388 | tmp[strlen(tmp) - 2] == '.' && |
| 389 | tmp[strlen(tmp) - 3] == '/') { |
| 390 | ERR("Using '/../' is not permitted in the trace path (%s)", |
| 391 | tmp); |
| 392 | ret = -1; |
| 393 | goto error; |
| 394 | } |
| 395 | ret = create_directory_check_exists(handle, tmp, mode); |
| 396 | if (ret < 0) { |
| 397 | if (errno != EACCES) { |
| 398 | PERROR("Failed to create directory \"%s\"", |
| 399 | path); |
| 400 | ret = -errno; |
| 401 | goto error; |
| 402 | } |
| 403 | } |
| 404 | *p = '/'; |
| 405 | } |
| 406 | } |
| 407 | |
| 408 | ret = create_directory_check_exists(handle, tmp, mode); |
| 409 | if (ret < 0) { |
| 410 | PERROR("mkdirat recursive last element"); |
| 411 | ret = -errno; |
| 412 | } |
| 413 | error: |
| 414 | return ret; |
| 415 | } |
| 416 | |
| 417 | LTTNG_HIDDEN |
| 418 | int lttng_directory_handle_create_subdirectory_as_user( |
| 419 | const struct lttng_directory_handle *handle, |
| 420 | const char *subdirectory, |
| 421 | mode_t mode, struct lttng_credentials *creds) |
| 422 | { |
| 423 | int ret; |
| 424 | |
| 425 | if (!creds) { |
| 426 | /* Run as current user. */ |
| 427 | ret = create_directory_check_exists(handle, |
| 428 | subdirectory, mode); |
| 429 | } else { |
| 430 | ret = _run_as_mkdir(handle, subdirectory, |
| 431 | mode, creds->uid, creds->gid); |
| 432 | } |
| 433 | |
| 434 | return ret; |
| 435 | } |
| 436 | |
| 437 | LTTNG_HIDDEN |
| 438 | int lttng_directory_handle_create_subdirectory_recursive_as_user( |
| 439 | const struct lttng_directory_handle *handle, |
| 440 | const char *subdirectory_path, |
| 441 | mode_t mode, struct lttng_credentials *creds) |
| 442 | { |
| 443 | int ret; |
| 444 | |
| 445 | if (!creds) { |
| 446 | /* Run as current user. */ |
| 447 | ret = create_directory_recursive(handle, |
| 448 | subdirectory_path, mode); |
| 449 | } else { |
| 450 | ret = _run_as_mkdir_recursive(handle, subdirectory_path, |
| 451 | mode, creds->uid, creds->gid); |
| 452 | } |
| 453 | |
| 454 | return ret; |
| 455 | } |
| 456 | |
| 457 | LTTNG_HIDDEN |
| 458 | int lttng_directory_handle_create_subdirectory( |
| 459 | const struct lttng_directory_handle *handle, |
| 460 | const char *subdirectory, |
| 461 | mode_t mode) |
| 462 | { |
| 463 | return lttng_directory_handle_create_subdirectory_as_user( |
| 464 | handle, subdirectory, mode, NULL); |
| 465 | } |
| 466 | |
| 467 | LTTNG_HIDDEN |
| 468 | int lttng_directory_handle_create_subdirectory_recursive( |
| 469 | const struct lttng_directory_handle *handle, |
| 470 | const char *subdirectory_path, |
| 471 | mode_t mode) |
| 472 | { |
| 473 | return lttng_directory_handle_create_subdirectory_recursive_as_user( |
| 474 | handle, subdirectory_path, mode, NULL); |
| 475 | } |