1 /* $OpenBSD: file.c,v 1.68 2019/02/05 02:17:32 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 2015 Nicholas Marriott <nicm@openbsd.org> 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER 15 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING 16 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include <sys/types.h> 20 #include <sys/ioctl.h> 21 #include <sys/mman.h> 22 #include <sys/queue.h> 23 #include <sys/socket.h> 24 #include <sys/stat.h> 25 #include <sys/uio.h> 26 #include <sys/wait.h> 27 28 #include <err.h> 29 #include <errno.h> 30 #include <fcntl.h> 31 #include <getopt.h> 32 #include <imsg.h> 33 #include <libgen.h> 34 #include <limits.h> 35 #include <pwd.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <time.h> 39 #include <unistd.h> 40 41 #include "file.h" 42 #include "magic.h" 43 #include "xmalloc.h" 44 45 struct input_msg { 46 int idx; 47 48 struct stat sb; 49 int error; 50 51 char link_path[PATH_MAX]; 52 int link_error; 53 int link_target; 54 }; 55 56 struct input_ack { 57 int idx; 58 }; 59 60 struct input_file { 61 struct magic *m; 62 struct input_msg *msg; 63 64 const char *path; 65 int fd; 66 67 void *base; 68 size_t size; 69 int mapped; 70 char *result; 71 }; 72 73 extern char *__progname; 74 75 __dead void usage(void); 76 77 static int prepare_message(struct input_msg *, int, const char *); 78 static void send_message(struct imsgbuf *, void *, size_t, int); 79 static int read_message(struct imsgbuf *, struct imsg *, pid_t); 80 81 static void read_link(struct input_msg *, const char *); 82 83 static __dead void child(int, pid_t, int, char **); 84 85 static void test_file(struct input_file *, size_t); 86 87 static int try_stat(struct input_file *); 88 static int try_empty(struct input_file *); 89 static int try_access(struct input_file *); 90 static int try_text(struct input_file *); 91 static int try_magic(struct input_file *); 92 static int try_unknown(struct input_file *); 93 94 static int bflag; 95 static int cflag; 96 static int iflag; 97 static int Lflag; 98 static int sflag; 99 static int Wflag; 100 101 static char *magicpath; 102 static FILE *magicfp; 103 104 static struct option longopts[] = { 105 { "brief", no_argument, NULL, 'b' }, 106 { "dereference", no_argument, NULL, 'L' }, 107 { "mime", no_argument, NULL, 'i' }, 108 { "mime-type", no_argument, NULL, 'i' }, 109 { NULL, 0, NULL, 0 } 110 }; 111 112 __dead void 113 usage(void) 114 { 115 fprintf(stderr, "usage: %s [-bchiLsW] file ...\n", __progname); 116 exit(1); 117 } 118 119 int 120 main(int argc, char **argv) 121 { 122 int opt, pair[2], fd, idx; 123 char *home; 124 struct passwd *pw; 125 struct imsgbuf ibuf; 126 struct imsg imsg; 127 struct input_msg msg; 128 struct input_ack *ack; 129 pid_t pid, parent; 130 131 tzset(); 132 133 for (;;) { 134 opt = getopt_long(argc, argv, "bchiLsW", longopts, NULL); 135 if (opt == -1) 136 break; 137 switch (opt) { 138 case 'b': 139 bflag = 1; 140 break; 141 case 'c': 142 cflag = 1; 143 break; 144 case 'h': 145 Lflag = 0; 146 break; 147 case 'i': 148 iflag = 1; 149 break; 150 case 'L': 151 Lflag = 1; 152 break; 153 case 's': 154 sflag = 1; 155 break; 156 case 'W': 157 Wflag = 1; 158 break; 159 default: 160 usage(); 161 } 162 } 163 argc -= optind; 164 argv += optind; 165 if (cflag) { 166 if (argc != 0) 167 usage(); 168 } else if (argc == 0) 169 usage(); 170 171 if (pledge("stdio rpath getpw recvfd sendfd id proc", NULL) == -1) 172 err(1, "pledge"); 173 174 magicfp = NULL; 175 if (geteuid() != 0 && !issetugid()) { 176 home = getenv("HOME"); 177 if (home == NULL || *home == '\0') { 178 pw = getpwuid(getuid()); 179 if (pw != NULL) 180 home = pw->pw_dir; 181 else 182 home = NULL; 183 } 184 if (home != NULL) { 185 xasprintf(&magicpath, "%s/.magic", home); 186 magicfp = fopen(magicpath, "r"); 187 if (magicfp == NULL) 188 free(magicpath); 189 } 190 } 191 if (magicfp == NULL) { 192 magicpath = xstrdup("/etc/magic"); 193 magicfp = fopen(magicpath, "r"); 194 } 195 if (magicfp == NULL) 196 err(1, "%s", magicpath); 197 198 parent = getpid(); 199 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pair) != 0) 200 err(1, "socketpair"); 201 switch (pid = fork()) { 202 case -1: 203 err(1, "fork"); 204 case 0: 205 close(pair[0]); 206 child(pair[1], parent, argc, argv); 207 } 208 close(pair[1]); 209 210 fclose(magicfp); 211 magicfp = NULL; 212 213 if (cflag) 214 goto wait_for_child; 215 216 imsg_init(&ibuf, pair[0]); 217 for (idx = 0; idx < argc; idx++) { 218 fd = prepare_message(&msg, idx, argv[idx]); 219 send_message(&ibuf, &msg, sizeof msg, fd); 220 221 if (read_message(&ibuf, &imsg, pid) == 0) 222 break; 223 if (imsg.hdr.len != IMSG_HEADER_SIZE + sizeof *ack) 224 errx(1, "message too small"); 225 ack = imsg.data; 226 if (ack->idx != idx) 227 errx(1, "index not expected"); 228 imsg_free(&imsg); 229 } 230 231 wait_for_child: 232 close(pair[0]); 233 while (wait(NULL) == -1 && errno != ECHILD) { 234 if (errno != EINTR) 235 err(1, "wait"); 236 } 237 _exit(0); /* let the child flush */ 238 } 239 240 static int 241 prepare_message(struct input_msg *msg, int idx, const char *path) 242 { 243 int fd, mode, error; 244 245 memset(msg, 0, sizeof *msg); 246 msg->idx = idx; 247 248 if (strcmp(path, "-") == 0) { 249 if (fstat(STDIN_FILENO, &msg->sb) == -1) { 250 msg->error = errno; 251 return (-1); 252 } 253 return (STDIN_FILENO); 254 } 255 256 if (Lflag) 257 error = stat(path, &msg->sb); 258 else 259 error = lstat(path, &msg->sb); 260 if (error == -1) { 261 msg->error = errno; 262 return (-1); 263 } 264 265 /* 266 * pledge(2) doesn't let us pass directory file descriptors around - 267 * but in fact we don't need them, so just don't open directories or 268 * symlinks (which could be to directories). 269 */ 270 mode = msg->sb.st_mode; 271 if (!S_ISDIR(mode) && !S_ISLNK(mode)) { 272 fd = open(path, O_RDONLY|O_NONBLOCK); 273 if (fd == -1 && (errno == ENFILE || errno == EMFILE)) 274 err(1, "open"); 275 } else 276 fd = -1; 277 if (S_ISLNK(mode)) 278 read_link(msg, path); 279 return (fd); 280 281 } 282 283 static void 284 send_message(struct imsgbuf *ibuf, void *msg, size_t msglen, int fd) 285 { 286 if (imsg_compose(ibuf, -1, -1, 0, fd, msg, msglen) != 1) 287 err(1, "imsg_compose"); 288 if (imsg_flush(ibuf) != 0) 289 err(1, "imsg_flush"); 290 } 291 292 static int 293 read_message(struct imsgbuf *ibuf, struct imsg *imsg, pid_t from) 294 { 295 int n; 296 297 while ((n = imsg_read(ibuf)) == -1 && errno == EAGAIN) 298 /* nothing */ ; 299 if (n == -1) 300 err(1, "imsg_read"); 301 if (n == 0) 302 return (0); 303 304 if ((n = imsg_get(ibuf, imsg)) == -1) 305 err(1, "imsg_get"); 306 if (n == 0) 307 return (0); 308 309 if ((pid_t)imsg->hdr.pid != from) 310 errx(1, "PIDs don't match"); 311 312 return (n); 313 314 } 315 316 static void 317 read_link(struct input_msg *msg, const char *path) 318 { 319 struct stat sb; 320 char lpath[PATH_MAX]; 321 char *copy, *root; 322 int used; 323 ssize_t size; 324 325 size = readlink(path, lpath, sizeof lpath - 1); 326 if (size == -1) { 327 msg->link_error = errno; 328 return; 329 } 330 lpath[size] = '\0'; 331 332 if (*lpath == '/') 333 strlcpy(msg->link_path, lpath, sizeof msg->link_path); 334 else { 335 copy = xstrdup(path); 336 337 root = dirname(copy); 338 if (*root == '\0' || strcmp(root, ".") == 0 || 339 strcmp (root, "/") == 0) 340 strlcpy(msg->link_path, lpath, sizeof msg->link_path); 341 else { 342 used = snprintf(msg->link_path, sizeof msg->link_path, 343 "%s/%s", root, lpath); 344 if (used < 0 || (size_t)used >= sizeof msg->link_path) { 345 msg->link_error = ENAMETOOLONG; 346 free(copy); 347 return; 348 } 349 } 350 351 free(copy); 352 } 353 354 if (!Lflag && stat(path, &sb) == -1) 355 msg->link_target = errno; 356 } 357 358 static __dead void 359 child(int fd, pid_t parent, int argc, char **argv) 360 { 361 struct passwd *pw; 362 struct magic *m; 363 struct imsgbuf ibuf; 364 struct imsg imsg; 365 struct input_msg *msg; 366 struct input_ack ack; 367 struct input_file inf; 368 int i, idx; 369 size_t len, width = 0; 370 371 if (pledge("stdio getpw recvfd id", NULL) == -1) 372 err(1, "pledge"); 373 374 if (geteuid() == 0) { 375 pw = getpwnam(FILE_USER); 376 if (pw == NULL) 377 errx(1, "unknown user %s", FILE_USER); 378 if (setgroups(1, &pw->pw_gid) != 0) 379 err(1, "setgroups"); 380 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) 381 err(1, "setresgid"); 382 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) 383 err(1, "setresuid"); 384 } 385 386 if (pledge("stdio recvfd", NULL) == -1) 387 err(1, "pledge"); 388 389 m = magic_load(magicfp, magicpath, cflag || Wflag); 390 if (cflag) { 391 magic_dump(m); 392 exit(0); 393 } 394 395 for (i = 0; i < argc; i++) { 396 len = strlen(argv[i]) + 1; 397 if (len > width) 398 width = len; 399 } 400 401 imsg_init(&ibuf, fd); 402 for (;;) { 403 if (read_message(&ibuf, &imsg, parent) == 0) 404 break; 405 if (imsg.hdr.len != IMSG_HEADER_SIZE + sizeof *msg) 406 errx(1, "message too small"); 407 msg = imsg.data; 408 409 idx = msg->idx; 410 if (idx < 0 || idx >= argc) 411 errx(1, "index out of range"); 412 413 memset(&inf, 0, sizeof inf); 414 inf.m = m; 415 inf.msg = msg; 416 417 inf.path = argv[idx]; 418 inf.fd = imsg.fd; 419 420 test_file(&inf, width); 421 422 if (imsg.fd != -1) 423 close(imsg.fd); 424 imsg_free(&imsg); 425 426 ack.idx = idx; 427 send_message(&ibuf, &ack, sizeof ack, -1); 428 } 429 exit(0); 430 } 431 432 static void * 433 fill_buffer(int fd, size_t size, size_t *used) 434 { 435 static void *buffer; 436 ssize_t got; 437 size_t left; 438 void *next; 439 440 if (buffer == NULL) 441 buffer = xmalloc(FILE_READ_SIZE); 442 443 next = buffer; 444 left = size; 445 while (left != 0) { 446 got = read(fd, next, left); 447 if (got == -1) { 448 if (errno == EINTR) 449 continue; 450 return (NULL); 451 } 452 if (got == 0) 453 break; 454 next = (char *)next + got; 455 left -= got; 456 } 457 *used = size - left; 458 return (buffer); 459 } 460 461 static int 462 load_file(struct input_file *inf) 463 { 464 size_t used; 465 466 if (inf->msg->sb.st_size == 0 && S_ISREG(inf->msg->sb.st_mode)) 467 return (0); /* empty file */ 468 if (inf->msg->sb.st_size == 0 || inf->msg->sb.st_size > FILE_READ_SIZE) 469 inf->size = FILE_READ_SIZE; 470 else 471 inf->size = inf->msg->sb.st_size; 472 473 if (!S_ISREG(inf->msg->sb.st_mode)) 474 goto try_read; 475 476 inf->base = mmap(NULL, inf->size, PROT_READ, MAP_PRIVATE, inf->fd, 0); 477 if (inf->base == MAP_FAILED) 478 goto try_read; 479 inf->mapped = 1; 480 return (0); 481 482 try_read: 483 inf->base = fill_buffer(inf->fd, inf->size, &used); 484 if (inf->base == NULL) { 485 xasprintf(&inf->result, "cannot read '%s' (%s)", inf->path, 486 strerror(errno)); 487 return (1); 488 } 489 inf->size = used; 490 return (0); 491 } 492 493 static int 494 try_stat(struct input_file *inf) 495 { 496 if (inf->msg->error != 0) { 497 xasprintf(&inf->result, "cannot stat '%s' (%s)", inf->path, 498 strerror(inf->msg->error)); 499 return (1); 500 } 501 if (sflag || strcmp(inf->path, "-") == 0) { 502 switch (inf->msg->sb.st_mode & S_IFMT) { 503 case S_IFIFO: 504 if (strcmp(inf->path, "-") != 0) 505 break; 506 case S_IFBLK: 507 case S_IFCHR: 508 case S_IFREG: 509 return (0); 510 } 511 } 512 513 if (iflag && (inf->msg->sb.st_mode & S_IFMT) != S_IFREG) { 514 xasprintf(&inf->result, "application/x-not-regular-file"); 515 return (1); 516 } 517 518 switch (inf->msg->sb.st_mode & S_IFMT) { 519 case S_IFDIR: 520 xasprintf(&inf->result, "directory"); 521 return (1); 522 case S_IFLNK: 523 if (inf->msg->link_error != 0) { 524 xasprintf(&inf->result, "unreadable symlink '%s' (%s)", 525 inf->path, strerror(inf->msg->link_error)); 526 return (1); 527 } 528 if (inf->msg->link_target == ELOOP) 529 xasprintf(&inf->result, "symbolic link in a loop"); 530 else if (inf->msg->link_target != 0) { 531 xasprintf(&inf->result, "broken symbolic link to '%s'", 532 inf->msg->link_path); 533 } else { 534 xasprintf(&inf->result, "symbolic link to '%s'", 535 inf->msg->link_path); 536 } 537 return (1); 538 case S_IFSOCK: 539 xasprintf(&inf->result, "socket"); 540 return (1); 541 case S_IFBLK: 542 xasprintf(&inf->result, "block special (%lu/%lu)", 543 (long)major(inf->msg->sb.st_rdev), 544 (long)minor(inf->msg->sb.st_rdev)); 545 return (1); 546 case S_IFCHR: 547 xasprintf(&inf->result, "character special (%lu/%lu)", 548 (long)major(inf->msg->sb.st_rdev), 549 (long)minor(inf->msg->sb.st_rdev)); 550 return (1); 551 case S_IFIFO: 552 xasprintf(&inf->result, "fifo (named pipe)"); 553 return (1); 554 } 555 return (0); 556 } 557 558 static int 559 try_empty(struct input_file *inf) 560 { 561 if (inf->size != 0) 562 return (0); 563 564 if (iflag) 565 xasprintf(&inf->result, "application/x-empty"); 566 else 567 xasprintf(&inf->result, "empty"); 568 return (1); 569 } 570 571 static int 572 try_access(struct input_file *inf) 573 { 574 char tmp[256] = ""; 575 576 if (inf->msg->sb.st_size == 0 && S_ISREG(inf->msg->sb.st_mode)) 577 return (0); /* empty file */ 578 if (inf->fd != -1) 579 return (0); 580 581 if (inf->msg->sb.st_mode & (S_IWUSR|S_IWGRP|S_IWOTH)) 582 strlcat(tmp, "writable, ", sizeof tmp); 583 if (inf->msg->sb.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) 584 strlcat(tmp, "executable, ", sizeof tmp); 585 if (S_ISREG(inf->msg->sb.st_mode)) 586 strlcat(tmp, "regular file, ", sizeof tmp); 587 strlcat(tmp, "no read permission", sizeof tmp); 588 589 inf->result = xstrdup(tmp); 590 return (1); 591 } 592 593 static int 594 try_text(struct input_file *inf) 595 { 596 const char *type, *s; 597 int flags; 598 599 flags = MAGIC_TEST_TEXT; 600 if (iflag) 601 flags |= MAGIC_TEST_MIME; 602 603 type = text_get_type(inf->base, inf->size); 604 if (type == NULL) 605 return (0); 606 607 s = magic_test(inf->m, inf->base, inf->size, flags); 608 if (s != NULL) { 609 inf->result = xstrdup(s); 610 return (1); 611 } 612 613 s = text_try_words(inf->base, inf->size, flags); 614 if (s != NULL) { 615 if (iflag) 616 inf->result = xstrdup(s); 617 else 618 xasprintf(&inf->result, "%s %s text", type, s); 619 return (1); 620 } 621 622 if (iflag) 623 inf->result = xstrdup("text/plain"); 624 else 625 xasprintf(&inf->result, "%s text", type); 626 return (1); 627 } 628 629 static int 630 try_magic(struct input_file *inf) 631 { 632 const char *s; 633 int flags; 634 635 flags = 0; 636 if (iflag) 637 flags |= MAGIC_TEST_MIME; 638 639 s = magic_test(inf->m, inf->base, inf->size, flags); 640 if (s != NULL) { 641 inf->result = xstrdup(s); 642 return (1); 643 } 644 return (0); 645 } 646 647 static int 648 try_unknown(struct input_file *inf) 649 { 650 if (iflag) 651 xasprintf(&inf->result, "application/octet-stream"); 652 else 653 xasprintf(&inf->result, "data"); 654 return (1); 655 } 656 657 static void 658 test_file(struct input_file *inf, size_t width) 659 { 660 char *label; 661 int stop; 662 663 stop = 0; 664 if (!stop) 665 stop = try_stat(inf); 666 if (!stop) 667 stop = try_access(inf); 668 if (!stop) 669 stop = load_file(inf); 670 if (!stop) 671 stop = try_empty(inf); 672 if (!stop) 673 stop = try_magic(inf); 674 if (!stop) 675 stop = try_text(inf); 676 if (!stop) 677 stop = try_unknown(inf); 678 679 if (bflag) 680 printf("%s\n", inf->result); 681 else { 682 if (strcmp(inf->path, "-") == 0) 683 xasprintf(&label, "/dev/stdin:"); 684 else 685 xasprintf(&label, "%s:", inf->path); 686 printf("%-*s %s\n", (int)width, label, inf->result); 687 free(label); 688 } 689 free(inf->result); 690 691 if (inf->mapped && inf->base != NULL) 692 munmap(inf->base, inf->size); 693 } 694