1 /* $OpenBSD: file.c,v 1.69 2019/11/30 14:01:45 mestre 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 if (pledge("stdio rpath sendfd", NULL) == -1) 211 err(1, "pledge"); 212 213 fclose(magicfp); 214 magicfp = NULL; 215 216 if (cflag) 217 goto wait_for_child; 218 219 imsg_init(&ibuf, pair[0]); 220 for (idx = 0; idx < argc; idx++) { 221 fd = prepare_message(&msg, idx, argv[idx]); 222 send_message(&ibuf, &msg, sizeof msg, fd); 223 224 if (read_message(&ibuf, &imsg, pid) == 0) 225 break; 226 if (imsg.hdr.len != IMSG_HEADER_SIZE + sizeof *ack) 227 errx(1, "message too small"); 228 ack = imsg.data; 229 if (ack->idx != idx) 230 errx(1, "index not expected"); 231 imsg_free(&imsg); 232 } 233 234 wait_for_child: 235 close(pair[0]); 236 while (wait(NULL) == -1 && errno != ECHILD) { 237 if (errno != EINTR) 238 err(1, "wait"); 239 } 240 _exit(0); /* let the child flush */ 241 } 242 243 static int 244 prepare_message(struct input_msg *msg, int idx, const char *path) 245 { 246 int fd, mode, error; 247 248 memset(msg, 0, sizeof *msg); 249 msg->idx = idx; 250 251 if (strcmp(path, "-") == 0) { 252 if (fstat(STDIN_FILENO, &msg->sb) == -1) { 253 msg->error = errno; 254 return (-1); 255 } 256 return (STDIN_FILENO); 257 } 258 259 if (Lflag) 260 error = stat(path, &msg->sb); 261 else 262 error = lstat(path, &msg->sb); 263 if (error == -1) { 264 msg->error = errno; 265 return (-1); 266 } 267 268 /* 269 * pledge(2) doesn't let us pass directory file descriptors around - 270 * but in fact we don't need them, so just don't open directories or 271 * symlinks (which could be to directories). 272 */ 273 mode = msg->sb.st_mode; 274 if (!S_ISDIR(mode) && !S_ISLNK(mode)) { 275 fd = open(path, O_RDONLY|O_NONBLOCK); 276 if (fd == -1 && (errno == ENFILE || errno == EMFILE)) 277 err(1, "open"); 278 } else 279 fd = -1; 280 if (S_ISLNK(mode)) 281 read_link(msg, path); 282 return (fd); 283 284 } 285 286 static void 287 send_message(struct imsgbuf *ibuf, void *msg, size_t msglen, int fd) 288 { 289 if (imsg_compose(ibuf, -1, -1, 0, fd, msg, msglen) != 1) 290 err(1, "imsg_compose"); 291 if (imsg_flush(ibuf) != 0) 292 err(1, "imsg_flush"); 293 } 294 295 static int 296 read_message(struct imsgbuf *ibuf, struct imsg *imsg, pid_t from) 297 { 298 int n; 299 300 while ((n = imsg_read(ibuf)) == -1 && errno == EAGAIN) 301 /* nothing */ ; 302 if (n == -1) 303 err(1, "imsg_read"); 304 if (n == 0) 305 return (0); 306 307 if ((n = imsg_get(ibuf, imsg)) == -1) 308 err(1, "imsg_get"); 309 if (n == 0) 310 return (0); 311 312 if ((pid_t)imsg->hdr.pid != from) 313 errx(1, "PIDs don't match"); 314 315 return (n); 316 317 } 318 319 static void 320 read_link(struct input_msg *msg, const char *path) 321 { 322 struct stat sb; 323 char lpath[PATH_MAX]; 324 char *copy, *root; 325 int used; 326 ssize_t size; 327 328 size = readlink(path, lpath, sizeof lpath - 1); 329 if (size == -1) { 330 msg->link_error = errno; 331 return; 332 } 333 lpath[size] = '\0'; 334 335 if (*lpath == '/') 336 strlcpy(msg->link_path, lpath, sizeof msg->link_path); 337 else { 338 copy = xstrdup(path); 339 340 root = dirname(copy); 341 if (*root == '\0' || strcmp(root, ".") == 0 || 342 strcmp (root, "/") == 0) 343 strlcpy(msg->link_path, lpath, sizeof msg->link_path); 344 else { 345 used = snprintf(msg->link_path, sizeof msg->link_path, 346 "%s/%s", root, lpath); 347 if (used < 0 || (size_t)used >= sizeof msg->link_path) { 348 msg->link_error = ENAMETOOLONG; 349 free(copy); 350 return; 351 } 352 } 353 354 free(copy); 355 } 356 357 if (!Lflag && stat(path, &sb) == -1) 358 msg->link_target = errno; 359 } 360 361 static __dead void 362 child(int fd, pid_t parent, int argc, char **argv) 363 { 364 struct passwd *pw; 365 struct magic *m; 366 struct imsgbuf ibuf; 367 struct imsg imsg; 368 struct input_msg *msg; 369 struct input_ack ack; 370 struct input_file inf; 371 int i, idx; 372 size_t len, width = 0; 373 374 if (pledge("stdio getpw recvfd id", NULL) == -1) 375 err(1, "pledge"); 376 377 if (geteuid() == 0) { 378 pw = getpwnam(FILE_USER); 379 if (pw == NULL) 380 errx(1, "unknown user %s", FILE_USER); 381 if (setgroups(1, &pw->pw_gid) != 0) 382 err(1, "setgroups"); 383 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) 384 err(1, "setresgid"); 385 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) 386 err(1, "setresuid"); 387 } 388 389 if (pledge("stdio recvfd", NULL) == -1) 390 err(1, "pledge"); 391 392 m = magic_load(magicfp, magicpath, cflag || Wflag); 393 if (cflag) { 394 magic_dump(m); 395 exit(0); 396 } 397 398 for (i = 0; i < argc; i++) { 399 len = strlen(argv[i]) + 1; 400 if (len > width) 401 width = len; 402 } 403 404 imsg_init(&ibuf, fd); 405 for (;;) { 406 if (read_message(&ibuf, &imsg, parent) == 0) 407 break; 408 if (imsg.hdr.len != IMSG_HEADER_SIZE + sizeof *msg) 409 errx(1, "message too small"); 410 msg = imsg.data; 411 412 idx = msg->idx; 413 if (idx < 0 || idx >= argc) 414 errx(1, "index out of range"); 415 416 memset(&inf, 0, sizeof inf); 417 inf.m = m; 418 inf.msg = msg; 419 420 inf.path = argv[idx]; 421 inf.fd = imsg.fd; 422 423 test_file(&inf, width); 424 425 if (imsg.fd != -1) 426 close(imsg.fd); 427 imsg_free(&imsg); 428 429 ack.idx = idx; 430 send_message(&ibuf, &ack, sizeof ack, -1); 431 } 432 exit(0); 433 } 434 435 static void * 436 fill_buffer(int fd, size_t size, size_t *used) 437 { 438 static void *buffer; 439 ssize_t got; 440 size_t left; 441 void *next; 442 443 if (buffer == NULL) 444 buffer = xmalloc(FILE_READ_SIZE); 445 446 next = buffer; 447 left = size; 448 while (left != 0) { 449 got = read(fd, next, left); 450 if (got == -1) { 451 if (errno == EINTR) 452 continue; 453 return (NULL); 454 } 455 if (got == 0) 456 break; 457 next = (char *)next + got; 458 left -= got; 459 } 460 *used = size - left; 461 return (buffer); 462 } 463 464 static int 465 load_file(struct input_file *inf) 466 { 467 size_t used; 468 469 if (inf->msg->sb.st_size == 0 && S_ISREG(inf->msg->sb.st_mode)) 470 return (0); /* empty file */ 471 if (inf->msg->sb.st_size == 0 || inf->msg->sb.st_size > FILE_READ_SIZE) 472 inf->size = FILE_READ_SIZE; 473 else 474 inf->size = inf->msg->sb.st_size; 475 476 if (!S_ISREG(inf->msg->sb.st_mode)) 477 goto try_read; 478 479 inf->base = mmap(NULL, inf->size, PROT_READ, MAP_PRIVATE, inf->fd, 0); 480 if (inf->base == MAP_FAILED) 481 goto try_read; 482 inf->mapped = 1; 483 return (0); 484 485 try_read: 486 inf->base = fill_buffer(inf->fd, inf->size, &used); 487 if (inf->base == NULL) { 488 xasprintf(&inf->result, "cannot read '%s' (%s)", inf->path, 489 strerror(errno)); 490 return (1); 491 } 492 inf->size = used; 493 return (0); 494 } 495 496 static int 497 try_stat(struct input_file *inf) 498 { 499 if (inf->msg->error != 0) { 500 xasprintf(&inf->result, "cannot stat '%s' (%s)", inf->path, 501 strerror(inf->msg->error)); 502 return (1); 503 } 504 if (sflag || strcmp(inf->path, "-") == 0) { 505 switch (inf->msg->sb.st_mode & S_IFMT) { 506 case S_IFIFO: 507 if (strcmp(inf->path, "-") != 0) 508 break; 509 case S_IFBLK: 510 case S_IFCHR: 511 case S_IFREG: 512 return (0); 513 } 514 } 515 516 if (iflag && (inf->msg->sb.st_mode & S_IFMT) != S_IFREG) { 517 xasprintf(&inf->result, "application/x-not-regular-file"); 518 return (1); 519 } 520 521 switch (inf->msg->sb.st_mode & S_IFMT) { 522 case S_IFDIR: 523 xasprintf(&inf->result, "directory"); 524 return (1); 525 case S_IFLNK: 526 if (inf->msg->link_error != 0) { 527 xasprintf(&inf->result, "unreadable symlink '%s' (%s)", 528 inf->path, strerror(inf->msg->link_error)); 529 return (1); 530 } 531 if (inf->msg->link_target == ELOOP) 532 xasprintf(&inf->result, "symbolic link in a loop"); 533 else if (inf->msg->link_target != 0) { 534 xasprintf(&inf->result, "broken symbolic link to '%s'", 535 inf->msg->link_path); 536 } else { 537 xasprintf(&inf->result, "symbolic link to '%s'", 538 inf->msg->link_path); 539 } 540 return (1); 541 case S_IFSOCK: 542 xasprintf(&inf->result, "socket"); 543 return (1); 544 case S_IFBLK: 545 xasprintf(&inf->result, "block special (%lu/%lu)", 546 (long)major(inf->msg->sb.st_rdev), 547 (long)minor(inf->msg->sb.st_rdev)); 548 return (1); 549 case S_IFCHR: 550 xasprintf(&inf->result, "character special (%lu/%lu)", 551 (long)major(inf->msg->sb.st_rdev), 552 (long)minor(inf->msg->sb.st_rdev)); 553 return (1); 554 case S_IFIFO: 555 xasprintf(&inf->result, "fifo (named pipe)"); 556 return (1); 557 } 558 return (0); 559 } 560 561 static int 562 try_empty(struct input_file *inf) 563 { 564 if (inf->size != 0) 565 return (0); 566 567 if (iflag) 568 xasprintf(&inf->result, "application/x-empty"); 569 else 570 xasprintf(&inf->result, "empty"); 571 return (1); 572 } 573 574 static int 575 try_access(struct input_file *inf) 576 { 577 char tmp[256] = ""; 578 579 if (inf->msg->sb.st_size == 0 && S_ISREG(inf->msg->sb.st_mode)) 580 return (0); /* empty file */ 581 if (inf->fd != -1) 582 return (0); 583 584 if (inf->msg->sb.st_mode & (S_IWUSR|S_IWGRP|S_IWOTH)) 585 strlcat(tmp, "writable, ", sizeof tmp); 586 if (inf->msg->sb.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) 587 strlcat(tmp, "executable, ", sizeof tmp); 588 if (S_ISREG(inf->msg->sb.st_mode)) 589 strlcat(tmp, "regular file, ", sizeof tmp); 590 strlcat(tmp, "no read permission", sizeof tmp); 591 592 inf->result = xstrdup(tmp); 593 return (1); 594 } 595 596 static int 597 try_text(struct input_file *inf) 598 { 599 const char *type, *s; 600 int flags; 601 602 flags = MAGIC_TEST_TEXT; 603 if (iflag) 604 flags |= MAGIC_TEST_MIME; 605 606 type = text_get_type(inf->base, inf->size); 607 if (type == NULL) 608 return (0); 609 610 s = magic_test(inf->m, inf->base, inf->size, flags); 611 if (s != NULL) { 612 inf->result = xstrdup(s); 613 return (1); 614 } 615 616 s = text_try_words(inf->base, inf->size, flags); 617 if (s != NULL) { 618 if (iflag) 619 inf->result = xstrdup(s); 620 else 621 xasprintf(&inf->result, "%s %s text", type, s); 622 return (1); 623 } 624 625 if (iflag) 626 inf->result = xstrdup("text/plain"); 627 else 628 xasprintf(&inf->result, "%s text", type); 629 return (1); 630 } 631 632 static int 633 try_magic(struct input_file *inf) 634 { 635 const char *s; 636 int flags; 637 638 flags = 0; 639 if (iflag) 640 flags |= MAGIC_TEST_MIME; 641 642 s = magic_test(inf->m, inf->base, inf->size, flags); 643 if (s != NULL) { 644 inf->result = xstrdup(s); 645 return (1); 646 } 647 return (0); 648 } 649 650 static int 651 try_unknown(struct input_file *inf) 652 { 653 if (iflag) 654 xasprintf(&inf->result, "application/octet-stream"); 655 else 656 xasprintf(&inf->result, "data"); 657 return (1); 658 } 659 660 static void 661 test_file(struct input_file *inf, size_t width) 662 { 663 char *label; 664 int stop; 665 666 stop = 0; 667 if (!stop) 668 stop = try_stat(inf); 669 if (!stop) 670 stop = try_access(inf); 671 if (!stop) 672 stop = load_file(inf); 673 if (!stop) 674 stop = try_empty(inf); 675 if (!stop) 676 stop = try_magic(inf); 677 if (!stop) 678 stop = try_text(inf); 679 if (!stop) 680 stop = try_unknown(inf); 681 682 if (bflag) 683 printf("%s\n", inf->result); 684 else { 685 if (strcmp(inf->path, "-") == 0) 686 xasprintf(&label, "/dev/stdin:"); 687 else 688 xasprintf(&label, "%s:", inf->path); 689 printf("%-*s %s\n", (int)width, label, inf->result); 690 free(label); 691 } 692 free(inf->result); 693 694 if (inf->mapped && inf->base != NULL) 695 munmap(inf->base, inf->size); 696 } 697