release/src/router/busybox/libbb/appletlib.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) tons of folks.  Tracking down who wrote what
   6  * isn't something I'm going to worry about...  If you wrote something
   7  * here, please feel free to acknowledge your work.
   8  *
   9  * Based in part on code from sash, Copyright (c) 1999 by David I. Bell
  10  * Permission has been granted to redistribute this code under GPL.
  11  *
  12  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  13  */
  14
  15 /* We are trying to not use printf, this benefits the case when selected
  16  * applets are really simple. Example:
  17  *
  18  * $ ./busybox
  19  * ...
  20  * Currently defined functions:
  21  *         basename, false, true
  22  *
  23  * $ size busybox
  24  *    text    data     bss     dec     hex filename
  25  *    4473      52      72    4597    11f5 busybox
  26  *
  27  * FEATURE_INSTALLER or FEATURE_SUID will still link printf routines in. :(
  28  */
  29 #include "busybox.h"
  30
  31 #if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) \
  32     || defined(__APPLE__) \
  33     )
  34 # include <malloc.h> /* for mallopt */
  35 #endif
  36
  37
  38 /* Declare <applet>_main() */
  39 #define PROTOTYPES
  40 #include "applets.h"
  41 #undef PROTOTYPES
  42
  43 /* Include generated applet names, pointers to <applet>_main, etc */
  44 #include "applet_tables.h"
  45 /* ...and if applet_tables generator says we have only one applet... */
  46 #ifdef SINGLE_APPLET_MAIN
  47 # undef ENABLE_FEATURE_INDIVIDUAL
  48 # define ENABLE_FEATURE_INDIVIDUAL 1
  49 # undef IF_FEATURE_INDIVIDUAL
  50 # define IF_FEATURE_INDIVIDUAL(...) __VA_ARGS__
  51 #endif
  52
  53 #include "usage_compressed.h"
  54
  55 static void run_applet_and_exit(const char *name, char **argv) NORETURN;
  56
  57 #if ENABLE_SHOW_USAGE && !ENABLE_FEATURE_COMPRESS_USAGE
  58 static const char usage_messages[] ALIGN1 = UNPACKED_USAGE;
  59 #else
  60 # define usage_messages 0
  61 #endif
  62
  63 #if ENABLE_FEATURE_COMPRESS_USAGE
  64
  65 static const char packed_usage[] ALIGN1 = { PACKED_USAGE };
  66 # include "bb_archive.h"
  67 static const char *unpack_usage_messages(void)
  68 {
  69         char *outbuf = NULL;
  70         bunzip_data *bd;
  71         int i;
  72
  73         i = start_bunzip(&bd,
  74                         /* src_fd: */ -1,
  75                         /* inbuf:  */ packed_usage,
  76                         /* len:    */ sizeof(packed_usage));
  77         /* read_bunzip can longjmp to start_bunzip, and ultimately
  78          * end up here with i != 0 on read data errors! Not trivial */
  79         if (!i) {
  80                 /* Cannot use xmalloc: will leak bd in NOFORK case! */
  81                 outbuf = malloc_or_warn(sizeof(UNPACKED_USAGE));
  82                 if (outbuf)
  83                         read_bunzip(bd, outbuf, sizeof(UNPACKED_USAGE));
  84         }
  85         dealloc_bunzip(bd);
  86         return outbuf;
  87 }
  88 # define dealloc_usage_messages(s) free(s)
  89
  90 #else
  91
  92 # define unpack_usage_messages() usage_messages
  93 # define dealloc_usage_messages(s) ((void)(s))
  94
  95 #endif /* FEATURE_COMPRESS_USAGE */
  96
  97
  98 void FAST_FUNC bb_show_usage(void)
  99 {
 100         if (ENABLE_SHOW_USAGE) {
 101 #ifdef SINGLE_APPLET_STR
 102                 /* Imagine that this applet is "true". Dont suck in printf! */
 103                 const char *usage_string = unpack_usage_messages();
 104
 105                 if (*usage_string == '\b') {
 106                         full_write2_str("No help available.\n\n");
 107                 } else {
 108                         full_write2_str("Usage: "SINGLE_APPLET_STR" ");
 109                         full_write2_str(usage_string);
 110                         full_write2_str("\n\n");
 111                 }
 112                 if (ENABLE_FEATURE_CLEAN_UP)
 113                         dealloc_usage_messages((char*)usage_string);
 114 #else
 115                 const char *p;
 116                 const char *usage_string = p = unpack_usage_messages();
 117                 int ap = find_applet_by_name(applet_name);
 118
 119                 if (ap < 0) /* never happens, paranoia */
 120                         xfunc_die();
 121                 while (ap) {
 122                         while (*p++) continue;
 123                         ap--;
 124                 }
 125                 full_write2_str(bb_banner);
 126                 full_write2_str(" multi-call binary.\n");
 127                 if (*p == '\b')
 128                         full_write2_str("\nNo help available.\n\n");
 129                 else {
 130                         full_write2_str("\nUsage: ");
 131                         full_write2_str(applet_name);
 132                         full_write2_str(" ");
 133                         full_write2_str(p);
 134                         full_write2_str("\n");
 135                 }
 136                 if (ENABLE_FEATURE_CLEAN_UP)
 137                         dealloc_usage_messages((char*)usage_string);
 138 #endif
 139         }
 140         xfunc_die();
 141 }
 142
 143 int FAST_FUNC find_applet_by_name(const char *name)
 144 {
 145         unsigned i, max;
 146         int j;
 147         const char *p;
 148
 149 /* The commented-out word-at-a-time code is ~40% faster, but +160 bytes.
 150  * "Faster" here saves ~0.5 microsecond of real time - not worth it.
 151  */
 152 #if 0 /*BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN*/
 153         uint32_t n32;
 154
 155         /* Handle all names < 2 chars long early */
 156         if (name[0] == '\0')
 157                 return -1; /* "" is not a valid applet name */
 158         if (name[1] == '\0') {
 159                 if (!ENABLE_TEST)
 160                         return -1; /* 1-char name is not valid */
 161                 if (name[0] != ']')
 162                         return -1; /* 1-char name which isn't "[" is not valid */
 163                 /* applet "[" is always applet #0: */
 164                 return 0;
 165         }
 166 #endif
 167
 168         p = applet_names;
 169         i = 0;
 170 #if KNOWN_APPNAME_OFFSETS <= 0
 171         max = NUM_APPLETS;
 172 #else
 173         max = NUM_APPLETS * KNOWN_APPNAME_OFFSETS;
 174         for (j = ARRAY_SIZE(applet_nameofs)-1; j >= 0; j--) {
 175                 const char *pp = applet_names + applet_nameofs[j];
 176                 if (strcmp(name, pp) >= 0) {
 177                         //bb_error_msg("name:'%s' >= pp:'%s'", name, pp);
 178                         p = pp;
 179                         i = max - NUM_APPLETS;
 180                         break;
 181                 }
 182                 max -= NUM_APPLETS;
 183         }
 184         max /= (unsigned)KNOWN_APPNAME_OFFSETS;
 185         i /= (unsigned)KNOWN_APPNAME_OFFSETS;
 186         //bb_error_msg("name:'%s' starting from:'%s' i:%u max:%u", name, p, i, max);
 187 #endif
 188
 189         /* Open-coded linear search without strcmp/strlen calls for speed */
 190
 191 #if 0 /*BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN*/
 192         /* skip "[\0" name, it's surely not it */
 193         if (ENABLE_TEST && LONE_CHAR(p, '['))
 194                 i++, p += 2;
 195         /* All remaining applet names in p[] are at least 2 chars long */
 196         /* name[] is also at least 2 chars long */
 197
 198         n32 = (name[0] << 0) | (name[1] << 8) | (name[2] << 16);
 199         while (i < max) {
 200                 uint32_t p32;
 201                 char ch;
 202
 203                 /* Quickly check match of the first 3 bytes */
 204                 move_from_unaligned32(p32, p);
 205                 p += 3;
 206                 if ((p32 & 0x00ffffff) != n32) {
 207                         /* Most likely case: 3 first bytes do not match */
 208                         i++;
 209                         if ((p32 & 0x00ff0000) == '\0')
 210                                 continue; // p[2] was NUL
 211                         p++;
 212                         if ((p32 & 0xff000000) == '\0')
 213                                 continue; // p[3] was NUL
 214                         /* p[0..3] aren't matching and none is NUL, check the rest */
 215                         while (*p++ != '\0')
 216                                 continue;
 217                         continue;
 218                 }
 219
 220                 /* Unlikely branch: first 3 bytes ([0..2]) match */
 221                 if ((p32 & 0x00ff0000) == '\0') {
 222                         /* name is 2-byte long, it is full match */
 223                         //bb_error_msg("found:'%s' i:%u", name, i);
 224                         return i;
 225                 }
 226                 /* Check remaining bytes [3..NUL] */
 227                 ch = (p32 >> 24);
 228                 j = 3;
 229                 while (ch == name[j]) {
 230                         if (ch == '\0') {
 231                                 //bb_error_msg("found:'%s' i:%u", name, i);
 232                                 return i;
 233                         }
 234                         ch = *++p;
 235                         j++;
 236                 }
 237                 /* Not a match. Skip it, including NUL */
 238                 while (ch != '\0')
 239                         ch = *++p;
 240                 p++;
 241                 i++;
 242         }
 243         return -1;
 244 #else
 245         while (i < max) {
 246                 char ch;
 247                 j = 0;
 248                 /* Do we see "name\0" in applet_names[p] position? */
 249                 while ((ch = *p) == name[j]) {
 250                         if (ch == '\0') {
 251                                 //bb_error_msg("found:'%s' i:%u", name, i);
 252                                 return i; /* yes */
 253                         }
 254                         p++;
 255                         j++;
 256                 }
 257                 /* No.
 258                  * p => 1st non-matching char in applet_names[],
 259                  * skip to and including NUL.
 260                  */
 261                 while (ch != '\0')
 262                         ch = *++p;
 263                 p++;
 264                 i++;
 265         }
 266         return -1;
 267 #endif
 268 }
 269
 270
 271 void lbb_prepare(const char *applet
 272                 IF_FEATURE_INDIVIDUAL(, char **argv))
 273                                 MAIN_EXTERNALLY_VISIBLE;
 274 void lbb_prepare(const char *applet
 275                 IF_FEATURE_INDIVIDUAL(, char **argv))
 276 {
 277 #ifdef __GLIBC__
 278         (*(int **)&bb_errno) = __errno_location();
 279         barrier();
 280 #endif
 281         applet_name = applet;
 282
 283         if (ENABLE_LOCALE_SUPPORT)
 284                 setlocale(LC_ALL, "");
 285
 286 #if ENABLE_FEATURE_INDIVIDUAL
 287         /* Redundant for busybox (run_applet_and_exit covers that case)
 288          * but needed for "individual applet" mode */
 289         if (argv[1]
 290          && !argv[2]
 291          && strcmp(argv[1], "--help") == 0
 292          && !is_prefixed_with(applet, "busybox")
 293         ) {
 294                 /* Special case. POSIX says "test --help"
 295                  * should be no different from e.g. "test --foo".  */
 296                 if (!ENABLE_TEST || strcmp(applet_name, "test") != 0)
 297                         bb_show_usage();
 298         }
 299 #endif
 300 }
 301
 302 /* The code below can well be in applets/applets.c, as it is used only
 303  * for busybox binary, not "individual" binaries.
 304  * However, keeping it here and linking it into libbusybox.so
 305  * (together with remaining tiny applets/applets.o)
 306  * makes it possible to avoid --whole-archive at link time.
 307  * This makes (shared busybox) + libbusybox smaller.
 308  * (--gc-sections would be even better....)
 309  */
 310
 311 const char *applet_name;
 312 #if !BB_MMU
 313 bool re_execed;
 314 #endif
 315
 316
 317 /* If not built as a single-applet executable... */
 318 #if !defined(SINGLE_APPLET_MAIN)
 319
 320 IF_FEATURE_SUID(static uid_t ruid;)  /* real uid */
 321
 322 # if ENABLE_FEATURE_SUID_CONFIG
 323
 324 static struct suid_config_t {
 325         /* next ptr must be first: this struct needs to be llist-compatible */
 326         struct suid_config_t *m_next;
 327         struct bb_uidgid_t m_ugid;
 328         int m_applet;
 329         mode_t m_mode;
 330 } *suid_config;
 331
 332 static bool suid_cfg_readable;
 333
 334 /* check if u is member of group g */
 335 static int ingroup(uid_t u, gid_t g)
 336 {
 337         struct group *grp = getgrgid(g);
 338         if (grp) {
 339                 char **mem;
 340                 for (mem = grp->gr_mem; *mem; mem++) {
 341                         struct passwd *pwd = getpwnam(*mem);
 342                         if (pwd && (pwd->pw_uid == u))
 343                                 return 1;
 344                 }
 345         }
 346         return 0;
 347 }
 348
 349 /* libbb candidate */
 350 static char *get_trimmed_slice(char *s, char *e)
 351 {
 352         /* First, consider the value at e to be nul and back up until we
 353          * reach a non-space char.  Set the char after that (possibly at
 354          * the original e) to nul. */
 355         while (e-- > s) {
 356                 if (!isspace(*e)) {
 357                         break;
 358                 }
 359         }
 360         e[1] = '\0';
 361
 362         /* Next, advance past all leading space and return a ptr to the
 363          * first non-space char; possibly the terminating nul. */
 364         return skip_whitespace(s);
 365 }
 366
 367 static void parse_config_file(void)
 368 {
 369         /* Don't depend on the tools to combine strings. */
 370         static const char config_file[] ALIGN1 = "/etc/busybox.conf";
 371
 372         struct suid_config_t *sct_head;
 373         int applet_no;
 374         FILE *f;
 375         const char *errmsg;
 376         unsigned lc;
 377         smallint section;
 378         struct stat st;
 379
 380         ruid = getuid();
 381         if (ruid == 0) /* run by root - don't need to even read config file */
 382                 return;
 383
 384         if ((stat(config_file, &st) != 0)       /* No config file? */
 385          || !S_ISREG(st.st_mode)                /* Not a regular file? */
 386          || (st.st_uid != 0)                    /* Not owned by root? */
 387          || (st.st_mode & (S_IWGRP | S_IWOTH))  /* Writable by non-root? */
 388          || !(f = fopen_for_read(config_file))  /* Cannot open? */
 389         ) {
 390                 return;
 391         }
 392
 393         suid_cfg_readable = 1;
 394         sct_head = NULL;
 395         section = lc = 0;
 396
 397         while (1) {
 398                 char buffer[256];
 399                 char *s;
 400
 401                 if (!fgets(buffer, sizeof(buffer), f)) { /* Are we done? */
 402                         // Looks like bloat
 403                         //if (ferror(f)) {   /* Make sure it wasn't a read error. */
 404                         //      errmsg = "reading";
 405                         //      goto pe_label;
 406                         //}
 407                         fclose(f);
 408                         suid_config = sct_head; /* Success, so set the pointer. */
 409                         return;
 410                 }
 411
 412                 s = buffer;
 413                 lc++;                                   /* Got a (partial) line. */
 414
 415                 /* If a line is too long for our buffer, we consider it an error.
 416                  * The following test does mistreat one corner case though.
 417                  * If the final line of the file does not end with a newline and
 418                  * yet exactly fills the buffer, it will be treated as too long
 419                  * even though there isn't really a problem.  But it isn't really
 420                  * worth adding code to deal with such an unlikely situation, and
 421                  * we do err on the side of caution.  Besides, the line would be
 422                  * too long if it did end with a newline. */
 423                 if (!strchr(s, '\n') && !feof(f)) {
 424                         errmsg = "line too long";
 425                         goto pe_label;
 426                 }
 427
 428                 /* Trim leading and trailing whitespace, ignoring comments, and
 429                  * check if the resulting string is empty. */
 430                 s = get_trimmed_slice(s, strchrnul(s, '#'));
 431                 if (!*s) {
 432                         continue;
 433                 }
 434
 435                 /* Check for a section header. */
 436
 437                 if (*s == '[') {
 438                         /* Unlike the old code, we ignore leading and trailing
 439                          * whitespace for the section name.  We also require that
 440                          * there are no stray characters after the closing bracket. */
 441                         char *e = strchr(s, ']');
 442                         if (!e   /* Missing right bracket? */
 443                          || e[1] /* Trailing characters? */
 444                          || !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */
 445                         ) {
 446                                 errmsg = "section header";
 447                                 goto pe_label;
 448                         }
 449                         /* Right now we only have one section so just check it.
 450                          * If more sections are added in the future, please don't
 451                          * resort to cascading ifs with multiple strcasecmp calls.
 452                          * That kind of bloated code is all too common.  A loop
 453                          * and a string table would be a better choice unless the
 454                          * number of sections is very small. */
 455                         if (strcasecmp(s, "SUID") == 0) {
 456                                 section = 1;
 457                                 continue;
 458                         }
 459                         section = -1;   /* Unknown section so set to skip. */
 460                         continue;
 461                 }
 462
 463                 /* Process sections. */
 464
 465                 if (section == 1) {             /* SUID */
 466                         /* Since we trimmed leading and trailing space above, we're
 467                          * now looking for strings of the form
 468                          *    <key>[::space::]*=[::space::]*<value>
 469                          * where both key and value could contain inner whitespace. */
 470
 471                         /* First get the key (an applet name in our case). */
 472                         char *e = strchr(s, '=');
 473                         if (e) {
 474                                 s = get_trimmed_slice(s, e);
 475                         }
 476                         if (!e || !*s) {        /* Missing '=' or empty key. */
 477                                 errmsg = "keyword";
 478                                 goto pe_label;
 479                         }
 480
 481                         /* Ok, we have an applet name.  Process the rhs if this
 482                          * applet is currently built in and ignore it otherwise.
 483                          * Note: this can hide config file bugs which only pop
 484                          * up when the busybox configuration is changed. */
 485                         applet_no = find_applet_by_name(s);
 486                         if (applet_no >= 0) {
 487                                 unsigned i;
 488                                 struct suid_config_t *sct;
 489
 490                                 /* Note: We currently don't check for duplicates!
 491                                  * The last config line for each applet will be the
 492                                  * one used since we insert at the head of the list.
 493                                  * I suppose this could be considered a feature. */
 494                                 sct = xzalloc(sizeof(*sct));
 495                                 sct->m_applet = applet_no;
 496                                 /*sct->m_mode = 0;*/
 497                                 sct->m_next = sct_head;
 498                                 sct_head = sct;
 499
 500                                 /* Get the specified mode. */
 501
 502                                 e = skip_whitespace(e+1);
 503
 504                                 for (i = 0; i < 3; i++) {
 505                                         /* There are 4 chars for each of user/group/other.
 506                                          * "x-xx" instead of "x-" are to make
 507                                          * "idx > 3" check catch invalid chars.
 508                                          */
 509                                         static const char mode_chars[] ALIGN1 = "Ssx-" "Ssx-" "x-xx";
 510                                         static const unsigned short mode_mask[] ALIGN2 = {
 511                                                 S_ISUID, S_ISUID|S_IXUSR, S_IXUSR, 0, /* Ssx- */
 512                                                 S_ISGID, S_ISGID|S_IXGRP, S_IXGRP, 0, /* Ssx- */
 513                                                                           S_IXOTH, 0  /*   x- */
 514                                         };
 515                                         const char *q = strchrnul(mode_chars + 4*i, *e);
 516                                         unsigned idx = q - (mode_chars + 4*i);
 517                                         if (idx > 3) {
 518                                                 errmsg = "mode";
 519                                                 goto pe_label;
 520                                         }
 521                                         sct->m_mode |= mode_mask[q - mode_chars];
 522                                         e++;
 523                                 }
 524
 525                                 /* Now get the user/group info. */
 526
 527                                 s = skip_whitespace(e);
 528                                 /* Default is 0.0, else parse USER.GROUP: */
 529                                 if (*s) {
 530                                         /* We require whitespace between mode and USER.GROUP */
 531                                         if ((s == e) || !(e = strchr(s, '.'))) {
 532                                                 errmsg = "uid.gid";
 533                                                 goto pe_label;
 534                                         }
 535                                         *e = ':'; /* get_uidgid needs USER:GROUP syntax */
 536                                         if (get_uidgid(&sct->m_ugid, s) == 0) {
 537                                                 errmsg = "unknown user/group";
 538                                                 goto pe_label;
 539                                         }
 540                                 }
 541                         }
 542                         continue;
 543                 }
 544
 545                 /* Unknown sections are ignored. */
 546
 547                 /* Encountering configuration lines prior to seeing a
 548                  * section header is treated as an error.  This is how
 549                  * the old code worked, but it may not be desirable.
 550                  * We may want to simply ignore such lines in case they
 551                  * are used in some future version of busybox. */
 552                 if (!section) {
 553                         errmsg = "keyword outside section";
 554                         goto pe_label;
 555                 }
 556         } /* while (1) */
 557
 558  pe_label:
 559         fclose(f);
 560         bb_error_msg("parse error in %s, line %u: %s", config_file, lc, errmsg);
 561
 562         /* Release any allocated memory before returning. */
 563         llist_free((llist_t*)sct_head, NULL);
 564 }
 565 # else
 566 static inline void parse_config_file(void)
 567 {
 568         IF_FEATURE_SUID(ruid = getuid();)
 569 }
 570 # endif /* FEATURE_SUID_CONFIG */
 571
 572
 573 # if ENABLE_FEATURE_SUID
 574 static void check_suid(int applet_no)
 575 {
 576         gid_t rgid;  /* real gid */
 577
 578         if (ruid == 0) /* set by parse_config_file() */
 579                 return; /* run by root - no need to check more */
 580         rgid = getgid();
 581
 582 #  if ENABLE_FEATURE_SUID_CONFIG
 583         if (suid_cfg_readable) {
 584                 uid_t uid;
 585                 struct suid_config_t *sct;
 586                 mode_t m;
 587
 588                 for (sct = suid_config; sct; sct = sct->m_next) {
 589                         if (sct->m_applet == applet_no)
 590                                 goto found;
 591                 }
 592                 goto check_need_suid;
 593  found:
 594                 /* Is this user allowed to run this applet? */
 595                 m = sct->m_mode;
 596                 if (sct->m_ugid.uid == ruid)
 597                         /* same uid */
 598                         m >>= 6;
 599                 else if ((sct->m_ugid.gid == rgid) || ingroup(ruid, sct->m_ugid.gid))
 600                         /* same group / in group */
 601                         m >>= 3;
 602                 if (!(m & S_IXOTH)) /* is x bit not set? */
 603                         bb_error_msg_and_die("you have no permission to run this applet");
 604
 605                 /* We set effective AND saved ids. If saved-id is not set
 606                  * like we do below, seteuid(0) can still later succeed! */
 607
 608                 /* Are we directed to change gid
 609                  * (APPLET = *s* USER.GROUP or APPLET = *S* USER.GROUP)?
 610                  */
 611                 if (sct->m_mode & S_ISGID)
 612                         rgid = sct->m_ugid.gid;
 613                 /* else: we will set egid = rgid, thus dropping sgid effect */
 614                 if (setresgid(-1, rgid, rgid))
 615                         bb_perror_msg_and_die("setresgid");
 616
 617                 /* Are we directed to change uid
 618                  * (APPLET = s** USER.GROUP or APPLET = S** USER.GROUP)?
 619                  */
 620                 uid = ruid;
 621                 if (sct->m_mode & S_ISUID)
 622                         uid = sct->m_ugid.uid;
 623                 /* else: we will set euid = ruid, thus dropping suid effect */
 624                 if (setresuid(-1, uid, uid))
 625                         bb_perror_msg_and_die("setresuid");
 626
 627                 goto ret;
 628         }
 629 #   if !ENABLE_FEATURE_SUID_CONFIG_QUIET
 630         {
 631                 static bool onetime = 0;
 632
 633                 if (!onetime) {
 634                         onetime = 1;
 635                         bb_error_msg("using fallback suid method");
 636                 }
 637         }
 638 #   endif
 639  check_need_suid:
 640 #  endif
 641         if (APPLET_SUID(applet_no) == BB_SUID_REQUIRE) {
 642                 /* Real uid is not 0. If euid isn't 0 too, suid bit
 643                  * is most probably not set on our executable */
 644                 if (geteuid())
 645                         bb_error_msg_and_die("must be suid to work properly");
 646         } else if (APPLET_SUID(applet_no) == BB_SUID_DROP) {
 647                 xsetgid(rgid);  /* drop all privileges */
 648                 xsetuid(ruid);
 649         }
 650 #  if ENABLE_FEATURE_SUID_CONFIG
 651  ret: ;
 652         llist_free((llist_t*)suid_config, NULL);
 653 #  endif
 654 }
 655 # else
 656 #  define check_suid(x) ((void)0)
 657 # endif /* FEATURE_SUID */
 658
 659
 660 # if ENABLE_FEATURE_INSTALLER
 661 static const char usr_bin [] ALIGN1 = "/usr/bin/";
 662 static const char usr_sbin[] ALIGN1 = "/usr/sbin/";
 663 static const char *const install_dir[] = {
 664         &usr_bin [8], /* "/" */
 665         &usr_bin [4], /* "/bin/" */
 666         &usr_sbin[4]  /* "/sbin/" */
 667 #  if !ENABLE_INSTALL_NO_USR
 668         ,usr_bin
 669         ,usr_sbin
 670 #  endif
 671 };
 672
 673 /* create (sym)links for each applet */
 674 static void install_links(const char *busybox, int use_symbolic_links,
 675                 char *custom_install_dir)
 676 {
 677         /* directory table
 678          * this should be consistent w/ the enum,
 679          * busybox.h::bb_install_loc_t, or else... */
 680         int (*lf)(const char *, const char *);
 681         char *fpc;
 682         const char *appname = applet_names;
 683         unsigned i;
 684         int rc;
 685
 686         lf = link;
 687         if (use_symbolic_links)
 688                 lf = symlink;
 689
 690         for (i = 0; i < ARRAY_SIZE(applet_main); i++) {
 691                 fpc = concat_path_file(
 692                                 custom_install_dir ? custom_install_dir : install_dir[APPLET_INSTALL_LOC(i)],
 693                                 appname);
 694                 // debug: bb_error_msg("%slinking %s to busybox",
 695                 //              use_symbolic_links ? "sym" : "", fpc);
 696                 rc = lf(busybox, fpc);
 697                 if (rc != 0 && errno != EEXIST) {
 698                         bb_simple_perror_msg(fpc);
 699                 }
 700                 free(fpc);
 701                 while (*appname++ != '\0')
 702                         continue;
 703         }
 704 }
 705 # elif ENABLE_BUSYBOX
 706 static void install_links(const char *busybox UNUSED_PARAM,
 707                 int use_symbolic_links UNUSED_PARAM,
 708                 char *custom_install_dir UNUSED_PARAM)
 709 {
 710 }
 711 # endif
 712
 713 # if ENABLE_BUSYBOX
 714 /* If we were called as "busybox..." */
 715 static int busybox_main(char **argv)
 716 {
 717         if (!argv[1]) {
 718                 /* Called without arguments */
 719                 const char *a;
 720                 int col;
 721                 unsigned output_width;
 722  help:
 723                 output_width = 80;
 724                 if (ENABLE_FEATURE_AUTOWIDTH) {
 725                         /* Obtain the terminal width */
 726                         output_width = get_terminal_width(2);
 727                 }
 728
 729                 dup2(1, 2);
 730                 full_write2_str(bb_banner); /* reuse const string */
 731                 full_write2_str(" multi-call binary.\n"); /* reuse */
 732                 full_write2_str(
 733                         "BusyBox is copyrighted by many authors between 1998-2015.\n"
 734                         "Licensed under GPLv2. See source distribution for detailed\n"
 735                         "copyright notices.\n"
 736                         "\n"
 737                         "Usage: busybox [function [arguments]...]\n"
 738                         "   or: busybox --list"IF_FEATURE_INSTALLER("[-full]")"\n"
 739                         IF_FEATURE_INSTALLER(
 740                         "   or: busybox --install [-s] [DIR]\n"
 741                         )
 742                         "   or: function [arguments]...\n"
 743                         "\n"
 744                         IF_NOT_FEATURE_SH_STANDALONE(
 745                         "\tBusyBox is a multi-call binary that combines many common Unix\n"
 746                         "\tutilities into a single executable.  Most people will create a\n"
 747                         "\tlink to busybox for each function they wish to use and BusyBox\n"
 748                         "\twill act like whatever it was invoked as.\n"
 749                         )
 750                         IF_FEATURE_SH_STANDALONE(
 751                         "\tBusyBox is a multi-call binary that combines many common Unix\n"
 752                         "\tutilities into a single executable.  The shell in this build\n"
 753                         "\tis configured to run built-in utilities without $PATH search.\n"
 754                         "\tYou don't need to install a link to busybox for each utility.\n"
 755                         "\tTo run external program, use full path (/sbin/ip instead of ip).\n"
 756                         )
 757                         "\n"
 758                         "Currently defined functions:\n"
 759                 );
 760                 col = 0;
 761                 a = applet_names;
 762                 /* prevent last comma to be in the very last pos */
 763                 output_width--;
 764                 while (*a) {
 765                         int len2 = strlen(a) + 2;
 766                         if (col >= (int)output_width - len2) {
 767                                 full_write2_str(",\n");
 768                                 col = 0;
 769                         }
 770                         if (col == 0) {
 771                                 col = 6;
 772                                 full_write2_str("\t");
 773                         } else {
 774                                 full_write2_str(", ");
 775                         }
 776                         full_write2_str(a);
 777                         col += len2;
 778                         a += len2 - 1;
 779                 }
 780                 full_write2_str("\n\n");
 781                 return 0;
 782         }
 783
 784         if (is_prefixed_with(argv[1], "--list")) {
 785                 unsigned i = 0;
 786                 const char *a = applet_names;
 787                 dup2(1, 2);
 788                 while (*a) {
 789 #  if ENABLE_FEATURE_INSTALLER
 790                         if (argv[1][6]) /* --list-full? */
 791                                 full_write2_str(install_dir[APPLET_INSTALL_LOC(i)] + 1);
 792 #  endif
 793                         full_write2_str(a);
 794                         full_write2_str("\n");
 795                         i++;
 796                         while (*a++ != '\0')
 797                                 continue;
 798                 }
 799                 return 0;
 800         }
 801
 802         if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) {
 803                 int use_symbolic_links;
 804                 const char *busybox;
 805
 806                 busybox = xmalloc_readlink(bb_busybox_exec_path);
 807                 if (!busybox) {
 808                         /* bb_busybox_exec_path is usually "/proc/self/exe".
 809                          * In chroot, readlink("/proc/self/exe") usually fails.
 810                          * In such case, better use argv[0] as symlink target
 811                          * if it is a full path name.
 812                          */
 813                         if (argv[0][0] != '/')
 814                                 bb_error_msg_and_die("'%s' is not an absolute path", argv[0]);
 815                         busybox = argv[0];
 816                 }
 817                 /* busybox --install [-s] [DIR]:
 818                  * -s: make symlinks
 819                  * DIR: directory to install links to
 820                  */
 821                 use_symbolic_links = (argv[2] && strcmp(argv[2], "-s") == 0 && ++argv);
 822                 install_links(busybox, use_symbolic_links, argv[2]);
 823                 return 0;
 824         }
 825
 826         if (strcmp(argv[1], "--help") == 0) {
 827                 /* "busybox --help [<applet>]" */
 828                 if (!argv[2])
 829                         goto help;
 830                 /* convert to "<applet> --help" */
 831                 argv[0] = argv[2];
 832                 argv[2] = NULL;
 833         } else {
 834                 /* "busybox <applet> arg1 arg2 ..." */
 835                 argv++;
 836         }
 837         /* We support "busybox /a/path/to/applet args..." too. Allows for
 838          * "#!/bin/busybox"-style wrappers */
 839         applet_name = bb_get_last_path_component_nostrip(argv[0]);
 840         run_applet_and_exit(applet_name, argv);
 841 }
 842 # endif
 843
 844 void FAST_FUNC run_applet_no_and_exit(int applet_no, char **argv)
 845 {
 846         int argc = 1;
 847
 848         while (argv[argc])
 849                 argc++;
 850
 851         /* Reinit some shared global data */
 852         xfunc_error_retval = EXIT_FAILURE;
 853         applet_name = bb_get_last_path_component_nostrip(argv[0]);
 854
 855         /* Special case. POSIX says "test --help"
 856          * should be no different from e.g. "test --foo".
 857          * Thus for "test", we skip --help check.
 858          * "true" and "false" are also special.
 859          */
 860         if (1
 861 #if defined APPLET_NO_test
 862          && applet_no != APPLET_NO_test
 863 #endif
 864 #if defined APPLET_NO_true
 865          && applet_no != APPLET_NO_true
 866 #endif
 867 #if defined APPLET_NO_false
 868          && applet_no != APPLET_NO_false
 869 #endif
 870         ) {
 871                 if (argc == 2 && strcmp(argv[1], "--help") == 0) {
 872                         /* Make "foo --help" exit with 0: */
 873                         xfunc_error_retval = 0;
 874                         bb_show_usage();
 875                 }
 876         }
 877         if (ENABLE_FEATURE_SUID)
 878                 check_suid(applet_no);
 879         exit(applet_main[applet_no](argc, argv));
 880 }
 881
 882 static NORETURN void run_applet_and_exit(const char *name, char **argv)
 883 {
 884         int applet;
 885
 886 # if ENABLE_BUSYBOX
 887         if (is_prefixed_with(name, "busybox"))
 888                 exit(busybox_main(argv));
 889 # endif
 890         /* find_applet_by_name() search is more expensive, so goes second */
 891         applet = find_applet_by_name(name);
 892         if (applet >= 0)
 893                 run_applet_no_and_exit(applet, argv);
 894
 895         /*bb_error_msg_and_die("applet not found"); - links in printf */
 896         full_write2_str(applet_name);
 897         full_write2_str(": applet not found\n");
 898         /* POSIX: "If a command is not found, the exit status shall be 127" */
 899         exit(127);
 900 }
 901
 902 #endif /* !defined(SINGLE_APPLET_MAIN) */
 903
 904
 905
 906 #if ENABLE_BUILD_LIBBUSYBOX
 907 int lbb_main(char **argv)
 908 #else
 909 int main(int argc UNUSED_PARAM, char **argv)
 910 #endif
 911 {
 912 #if 0
 913         /* TODO: find a use for a block of memory between end of .bss
 914          * and end of page. For example, I'm getting "_end:0x812e698 2408 bytes"
 915          * - more than 2k of wasted memory (in this particular build)
 916          * *per each running process*!
 917          * (If your linker does not generate "_end" name, weak attribute
 918          * makes &_end == NULL, end_len == 0 here.)
 919          */
 920         extern char _end[] __attribute__((weak));
 921         unsigned end_len = (-(int)_end) & 0xfff;
 922         printf("_end:%p %u bytes\n", &_end, end_len);
 923 #endif
 924
 925         /* Tweak malloc for reduced memory consumption */
 926 #ifdef M_TRIM_THRESHOLD
 927         /* M_TRIM_THRESHOLD is the maximum amount of freed top-most memory
 928          * to keep before releasing to the OS
 929          * Default is way too big: 256k
 930          */
 931         mallopt(M_TRIM_THRESHOLD, 8 * 1024);
 932 #endif
 933 #ifdef M_MMAP_THRESHOLD
 934         /* M_MMAP_THRESHOLD is the request size threshold for using mmap()
 935          * Default is too big: 256k
 936          */
 937         mallopt(M_MMAP_THRESHOLD, 32 * 1024 - 256);
 938 #endif
 939
 940 #if !BB_MMU
 941         /* NOMMU re-exec trick sets high-order bit in first byte of name */
 942         if (argv[0][0] & 0x80) {
 943                 re_execed = 1;
 944                 argv[0][0] &= 0x7f;
 945         }
 946 #endif
 947
 948 #if defined(SINGLE_APPLET_MAIN)
 949         /* Only one applet is selected in .config */
 950         if (argv[1] && is_prefixed_with(argv[0], "busybox")) {
 951                 /* "busybox <applet> <params>" should still work as expected */
 952                 argv++;
 953         }
 954         /* applet_names in this case is just "applet\0\0" */
 955         lbb_prepare(applet_names IF_FEATURE_INDIVIDUAL(, argv));
 956         return SINGLE_APPLET_MAIN(argc, argv);
 957 #else
 958         lbb_prepare("busybox" IF_FEATURE_INDIVIDUAL(, argv));
 959
 960 #if !ENABLE_BUSYBOX
 961         if (argv[1] && is_prefixed_with(bb_basename(argv[0]), "busybox"))
 962                 argv++;
 963 #endif
 964         applet_name = argv[0];
 965         if (applet_name[0] == '-')
 966                 applet_name++;
 967         applet_name = bb_basename(applet_name);
 968
 969         parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */
 970
 971         run_applet_and_exit(applet_name, argv);
 972 #endif
 973 }