summaryrefslogtreecommitdiff
path: root/applets/applets.c
blob: c2040b9a3d29e3220b9e08c40e1e4c218a117b5c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) tons of folks.  Tracking down who wrote what
 * isn't something I'm going to worry about...  If you wrote something
 * here, please feel free to acknowledge your work.
 *
 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell
 * Permission has been granted to redistribute this code under the GPL.
 *
 * Licensed under GPLv2 or later, see file License in this tarball for details.
 */

#include <assert.h>
#include "busybox.h"

/* Apparently uclibc defines __GLIBC__ (compat trick?). Oh well. */
#if ENABLE_STATIC && defined(__GLIBC__) && !defined(__UCLIBC__)
#warning Static linking against glibc produces buggy executables
#warning (glibc does not cope well with ld --gc-sections).
#warning See sources.redhat.com/bugzilla/show_bug.cgi?id=3400
#warning Note that glibc is unsuitable for static linking anyway.
#warning If you still want to do it, remove -Wl,--gc-sections
#warning from top-level Makefile and remove this warning.
#error Aborting compilation.
#endif


/* Declare <applet>_main() */
#define PROTOTYPES
#include "applets.h"
#undef PROTOTYPES

#if ENABLE_SHOW_USAGE && !ENABLE_FEATURE_COMPRESS_USAGE
/* Define usage_messages[] */
static const char usage_messages[] ALIGN1 = ""
#define MAKE_USAGE
#include "usage.h"
#include "applets.h"
;
#undef MAKE_USAGE
#else
#define usage_messages 0
#endif /* SHOW_USAGE */

/* Define struct bb_applet applets[] */
#include "applets.h"
/* The -1 arises because of the {0,NULL,0,-1} entry. */

#if ENABLE_FEATURE_SH_STANDALONE
const unsigned short NUM_APPLETS = ARRAY_SIZE(applets);
#endif
const struct bb_applet *current_applet;
const char *applet_name ATTRIBUTE_EXTERNALLY_VISIBLE;
#if !BB_MMU
bool re_execed;
#endif

USE_FEATURE_SUID(static uid_t ruid;)  /* real uid */

#if ENABLE_FEATURE_SUID_CONFIG

/* applets[] is const, so we have to define this "override" structure */
static struct BB_suid_config {
	const struct bb_applet *m_applet;
	uid_t m_uid;
	gid_t m_gid;
	mode_t m_mode;
	struct BB_suid_config *m_next;
} *suid_config;

static bool suid_cfg_readable;

/* check if u is member of group g */
static int ingroup(uid_t u, gid_t g)
{
	struct group *grp = getgrgid(g);

	if (grp) {
		char **mem;

		for (mem = grp->gr_mem; *mem; mem++) {
			struct passwd *pwd = getpwnam(*mem);

			if (pwd && (pwd->pw_uid == u))
				return 1;
		}
	}
	return 0;
}

/* This should probably be a libbb routine.  In that case,
 * I'd probably rename it to something like bb_trimmed_slice.
 */
static char *get_trimmed_slice(char *s, char *e)
{
	/* First, consider the value at e to be nul and back up until we
	 * reach a non-space char.  Set the char after that (possibly at
	 * the original e) to nul. */
	while (e-- > s) {
		if (!isspace(*e)) {
			break;
		}
	}
	e[1] = '\0';

	/* Next, advance past all leading space and return a ptr to the
	 * first non-space char; possibly the terminating nul. */
	return skip_whitespace(s);
}

/* Don't depend on the tools to combine strings. */
static const char config_file[] ALIGN1 = "/etc/busybox.conf";

/* We don't supply a value for the nul, so an index adjustment is
 * necessary below.  Also, we use unsigned short here to save some
 * space even though these are really mode_t values. */
static const unsigned short mode_mask[] ALIGN2 = {
	/*  SST     sst                 xxx         --- */
	S_ISUID,    S_ISUID|S_IXUSR,    S_IXUSR,    0,	/* user */
	S_ISGID,    S_ISGID|S_IXGRP,    S_IXGRP,    0,	/* group */
	0,          S_IXOTH,            S_IXOTH,    0	/* other */
};

#define parse_error(x)  do { errmsg = x; goto pe_label; } while (0)

static void parse_config_file(void)
{
	struct BB_suid_config *sct_head;
	struct BB_suid_config *sct;
	const struct bb_applet *applet;
	FILE *f;
	const char *errmsg;
	char *s;
	char *e;
	int i;
	unsigned lc;
	smallint section;
	char buffer[256];
	struct stat st;

	assert(!suid_config); /* Should be set to NULL by bss init. */

	ruid = getuid();
	if (ruid == 0) /* run by root - don't need to even read config file */
		return;

	if ((stat(config_file, &st) != 0)       /* No config file? */
	 || !S_ISREG(st.st_mode)                /* Not a regular file? */
	 || (st.st_uid != 0)                    /* Not owned by root? */
	 || (st.st_mode & (S_IWGRP | S_IWOTH))  /* Writable by non-root? */
	 || !(f = fopen(config_file, "r"))      /* Cannot open? */
	) {
		return;
	}

	suid_cfg_readable = 1;
	sct_head = NULL;
	section = lc = 0;

	while (1) {
		s = buffer;

		if (!fgets(s, sizeof(buffer), f)) { /* Are we done? */
			if (ferror(f)) {   /* Make sure it wasn't a read error. */
				parse_error("reading");
			}
			fclose(f);
			suid_config = sct_head;	/* Success, so set the pointer. */
			return;
		}

		lc++;					/* Got a (partial) line. */

		/* If a line is too long for our buffer, we consider it an error.
		 * The following test does mistreat one corner case though.
		 * If the final line of the file does not end with a newline and
		 * yet exactly fills the buffer, it will be treated as too long
		 * even though there isn't really a problem.  But it isn't really
		 * worth adding code to deal with such an unlikely situation, and
		 * we do err on the side of caution.  Besides, the line would be
		 * too long if it did end with a newline. */
		if (!strchr(s, '\n') && !feof(f)) {
			parse_error("line too long");
		}

		/* Trim leading and trailing whitespace, ignoring comments, and
		 * check if the resulting string is empty. */
		s = get_trimmed_slice(s, strchrnul(s, '#'));
		if (!*s) {
			continue;
		}

		/* Check for a section header. */

		if (*s == '[') {
			/* Unlike the old code, we ignore leading and trailing
			 * whitespace for the section name.  We also require that
			 * there are no stray characters after the closing bracket. */
			e = strchr(s, ']');
			if (!e   /* Missing right bracket? */
			 || e[1] /* Trailing characters? */
			 || !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */
			) {
				parse_error("section header");
			}
			/* Right now we only have one section so just check it.
			 * If more sections are added in the future, please don't
			 * resort to cascading ifs with multiple strcasecmp calls.
			 * That kind of bloated code is all too common.  A loop
			 * and a string table would be a better choice unless the
			 * number of sections is very small. */
			if (strcasecmp(s, "SUID") == 0) {
				section = 1;
				continue;
			}
			section = -1;	/* Unknown section so set to skip. */
			continue;
		}

		/* Process sections. */

		if (section == 1) {		/* SUID */
			/* Since we trimmed leading and trailing space above, we're
			 * now looking for strings of the form
			 *    <key>[::space::]*=[::space::]*<value>
			 * where both key and value could contain inner whitespace. */

			/* First get the key (an applet name in our case). */
			e = strchr(s, '=');
			if (e) {
				s = get_trimmed_slice(s, e);
			}
			if (!e || !*s) {	/* Missing '=' or empty key. */
				parse_error("keyword");
			}

			/* Ok, we have an applet name.  Process the rhs if this
			 * applet is currently built in and ignore it otherwise.
			 * Note: this can hide config file bugs which only pop
			 * up when the busybox configuration is changed. */
			applet = find_applet_by_name(s);
			if (applet) {
				/* Note: We currently don't check for duplicates!
				 * The last config line for each applet will be the
				 * one used since we insert at the head of the list.
				 * I suppose this could be considered a feature. */
				sct = xmalloc(sizeof(struct BB_suid_config));
				sct->m_applet = applet;
				sct->m_mode = 0;
				sct->m_next = sct_head;
				sct_head = sct;

				/* Get the specified mode. */

				e = skip_whitespace(e+1);

				for (i = 0; i < 3; i++) {
					/* There are 4 chars + 1 nul for each of user/group/other. */
					static const char mode_chars[] ALIGN1 = "Ssx-\0" "Ssx-\0" "Ttx-";

					const char *q;
					q = strchrnul(mode_chars + 5*i, *e++);
					if (!*q) {
						parse_error("mode");
					}
					/* Adjust by -i to account for nul. */
					sct->m_mode |= mode_mask[(q - mode_chars) - i];
				}

				/* Now get the the user/group info. */

				s = skip_whitespace(e);

				/* Note: we require whitespace between the mode and the
				 * user/group info. */
				if ((s == e) || !(e = strchr(s, '.'))) {
					parse_error("<uid>.<gid>");
				}
				*e++ = '\0';

				/* We can't use get_ug_id here since it would exit()
				 * if a uid or gid was not found.  Oh well... */
				sct->m_uid = bb_strtoul(s, NULL, 10);
				if (errno) {
					struct passwd *pwd = getpwnam(s);
					if (!pwd) {
						parse_error("user");
					}
					sct->m_uid = pwd->pw_uid;
				}

				sct->m_gid = bb_strtoul(e, NULL, 10);
				if (errno) {
					struct group *grp;
					grp = getgrnam(e);
					if (!grp) {
						parse_error("group");
					}
					sct->m_gid = grp->gr_gid;
				}
			}
			continue;
		}

		/* Unknown sections are ignored. */

		/* Encountering configuration lines prior to seeing a
		 * section header is treated as an error.  This is how
		 * the old code worked, but it may not be desirable.
		 * We may want to simply ignore such lines in case they
		 * are used in some future version of busybox. */
		if (!section) {
			parse_error("keyword outside section");
		}

	} /* while (1) */

 pe_label:
	fprintf(stderr, "Parse error in %s, line %d: %s\n",
			config_file, lc, errmsg);

	fclose(f);
	/* Release any allocated memory before returning. */
	while (sct_head) {
		sct = sct_head->m_next;
		free(sct_head);
		sct_head = sct;
	}
}
#else
static inline void parse_config_file(void)
{
	USE_FEATURE_SUID(ruid = getuid();)
}
#endif /* FEATURE_SUID_CONFIG */


#if ENABLE_FEATURE_SUID
static void check_suid(const struct bb_applet *applet)
{
	gid_t rgid;  /* real gid */

	if (ruid == 0) /* set by parse_config_file() */
		return; /* run by root - no need to check more */
	rgid = getgid();

#if ENABLE_FEATURE_SUID_CONFIG
	if (suid_cfg_readable) {
		uid_t uid;
		struct BB_suid_config *sct;
		mode_t m;

		for (sct = suid_config; sct; sct = sct->m_next) {
			if (sct->m_applet == applet)
				goto found;
		}
		/* default: drop all privileges */
		xsetgid(rgid);
		xsetuid(ruid);
		return;
 found:
		m = sct->m_mode;
		if (sct->m_uid == ruid)
			/* same uid */
			m >>= 6;
		else if ((sct->m_gid == rgid) || ingroup(ruid, sct->m_gid))
			/* same group / in group */
			m >>= 3;

		if (!(m & S_IXOTH))           /* is x bit not set ? */
			bb_error_msg_and_die("you have no permission to run this applet!");

		/* _both_ sgid and group_exec have to be set for setegid */
		if ((sct->m_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
			rgid = sct->m_gid;
		/* else (no setegid) we will set egid = rgid */

		/* We set effective AND saved ids. If saved-id is not set
		 * like we do below, seteiud(0) can still later succeed! */
		if (setresgid(-1, rgid, rgid))
			bb_perror_msg_and_die("setresgid");

		/* do we have to set effective uid? */
		uid = ruid;
		if (sct->m_mode & S_ISUID)
			uid = sct->m_uid;
		/* else (no seteuid) we will set euid = ruid */

		if (setresuid(-1, uid, uid))
			bb_perror_msg_and_die("setresuid");
		return;
	}
#if !ENABLE_FEATURE_SUID_CONFIG_QUIET
	{
		static bool onetime = 0;

		if (!onetime) {
			onetime = 1;
			fprintf(stderr, "Using fallback suid method\n");
		}
	}
#endif
#endif

	if (applet->need_suid == _BB_SUID_ALWAYS) {
		/* Real uid is not 0. If euid isn't 0 too, suid bit
		 * is most probably not set on our executable */
		if (geteuid())
			bb_error_msg_and_die("applet requires root privileges!");
	} else if (applet->need_suid == _BB_SUID_NEVER) {
		xsetgid(rgid);  /* drop all privileges */
		xsetuid(ruid);
	}
}
#else
#define check_suid(x) ((void)0)
#endif /* FEATURE_SUID */


#if ENABLE_FEATURE_COMPRESS_USAGE

#include "usage_compressed.h"
#include "unarchive.h"

static const char *unpack_usage_messages(void)
{
	char *outbuf = NULL;
	bunzip_data *bd;
	int i;

	i = start_bunzip(&bd,
			/* src_fd: */ -1,
			/* inbuf:  */ packed_usage,
			/* len:    */ sizeof(packed_usage));
	/* read_bunzip can longjmp to start_bunzip, and ultimately
	 * end up here with i != 0 on read data errors! Not trivial */
	if (!i) {
		/* Cannot use xmalloc: will leak bd in NOFORK case! */
		outbuf = malloc_or_warn(SIZEOF_usage_messages);
		if (outbuf)
			read_bunzip(bd, outbuf, SIZEOF_usage_messages);
	}
	dealloc_bunzip(bd);
	return outbuf;
}
#define dealloc_usage_messages(s) free(s)

#else

#define unpack_usage_messages() usage_messages
#define dealloc_usage_messages(s) ((void)(s))

#endif /* FEATURE_COMPRESS_USAGE */


void bb_show_usage(void)
{
	if (ENABLE_SHOW_USAGE) {
		const char *format_string;
		const char *p;
		const char *usage_string = p = unpack_usage_messages();
		int i;

		i = current_applet - applets;
		while (i) {
			while (*p++) continue;
			i--;
		}

		fprintf(stderr, "%s multi-call binary\n", bb_banner);
		format_string = "\nUsage: %s %s\n\n";
		if (*p == '\b')
			format_string = "\nNo help available.\n\n";
		fprintf(stderr, format_string, applet_name, p);
		dealloc_usage_messages((char*)usage_string);
	}
	xfunc_die();
}


static int applet_name_compare(const void *name, const void *vapplet)
{
	const struct bb_applet *applet = vapplet;

	return strcmp(name, applet->name);
}

const struct bb_applet *find_applet_by_name(const char *name)
{
	/* Do a binary search to find the applet entry given the name. */
	return bsearch(name, applets, ARRAY_SIZE(applets)-1, sizeof(applets[0]),
				applet_name_compare);
}


#if ENABLE_FEATURE_INSTALLER
/* create (sym)links for each applet */
static void install_links(const char *busybox, int use_symbolic_links)
{
	/* directory table
	 * this should be consistent w/ the enum,
	 * busybox.h::bb_install_loc_t, or else... */
	static const char usr_bin [] ALIGN1 = "/usr/bin";
	static const char usr_sbin[] ALIGN1 = "/usr/sbin";
	static const char *const install_dir[] = {
		&usr_bin [8], /* "", equivalent to "/" for concat_path_file() */
		&usr_bin [4], /* "/bin" */
		&usr_sbin[4], /* "/sbin" */
		usr_bin,
		usr_sbin
	};

	int (*lf)(const char *, const char *) = link;
	char *fpc;
	int i;
	int rc;

	if (use_symbolic_links)
		lf = symlink;

	for (i = 0; applets[i].name != NULL; i++) {
		fpc = concat_path_file(
				install_dir[applets[i].install_loc],
				applets[i].name);
		rc = lf(busybox, fpc);
		if (rc != 0 && errno != EEXIST) {
			bb_perror_msg("%s", fpc);
		}
		free(fpc);
	}
}
#else
#define install_links(x,y) ((void)0)
#endif /* FEATURE_INSTALLER */


/* If we were called as "busybox..." */
static int busybox_main(char **argv)
{
	if (!argv[1]) {
		/* Called without arguments */
		const struct bb_applet *a;
		int col, output_width;
 help:
		output_width = 80;
		if (ENABLE_FEATURE_AUTOWIDTH) {
			/* Obtain the terminal width.  */
			get_terminal_width_height(0, &output_width, NULL);
		}
		/* leading tab and room to wrap */
		output_width -= sizeof("start-stop-daemon, ") + 8;

		printf("%s multi-call binary\n", bb_banner); /* reuse const string... */
		printf("Copyright (C) 1998-2006  Erik Andersen, Rob Landley, and others.\n"
		       "Licensed under GPLv2.  See source distribution for full notice.\n"
		       "\n"
		       "Usage: busybox [function] [arguments]...\n"
		       "   or: [function] [arguments]...\n"
		       "\n"
		       "\tBusyBox is a multi-call binary that combines many common Unix\n"
		       "\tutilities into a single executable.  Most people will create a\n"
		       "\tlink to busybox for each function they wish to use and BusyBox\n"
		       "\twill act like whatever it was invoked as!\n"
		       "\nCurrently defined functions:\n");
		col = 0;
		a = applets;
		while (a->name) {
			if (col > output_width) {
				puts(",");
				col = 0;
			}
			col += printf("%s%s", (col ? ", " : "\t"), a->name);
			a++;
		}
		puts("\n");
		return 0;
	}

	if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) {
		const char *busybox;
		busybox = xmalloc_readlink_or_warn(bb_busybox_exec_path);
		if (!busybox)
			busybox = bb_busybox_exec_path;
		/* -s makes symlinks */
		install_links(busybox,
				 argv[2] && strcmp(argv[2], "-s") == 0);
		return 0;
	}

	if (strcmp(argv[1], "--help") == 0) {
		/* "busybox --help [<applet>]" */
		if (!argv[2])
			goto help;
		/* convert to "<applet> --help" */
		argv[0] = argv[2];
		argv[2] = NULL;
	} else {
		/* "busybox <applet> arg1 arg2 ..." */
		argv++;
	}
	/* We support "busybox /a/path/to/applet args..." too. Allows for
	 * "#!/bin/busybox"-style wrappers */
	applet_name = bb_get_last_path_component(argv[0]);
	run_applet_and_exit(applet_name, argv);
	bb_error_msg_and_die("applet not found");
}

void run_current_applet_and_exit(char **argv)
{
	int argc = 1;

	while (argv[argc])
		argc++;

	/* Reinit some shared global data */
	optind = 1;
	xfunc_error_retval = EXIT_FAILURE;

	applet_name = current_applet->name;
	if (argc == 2 && !strcmp(argv[1], "--help"))
		bb_show_usage();
	if (ENABLE_FEATURE_SUID)
		check_suid(current_applet);
	exit(current_applet->main(argc, argv));
}

void run_applet_and_exit(const char *name, char **argv)
{
	current_applet = find_applet_by_name(name);
	if (current_applet)
		run_current_applet_and_exit(argv);
	if (!strncmp(name, "busybox", 7))
		exit(busybox_main(argv));
}


#ifdef __GLIBC__
/* Make it reside in R/W memory: */
int *const bb_errno __attribute__ ((section (".data")));
#endif

int main(int argc, char **argv)
{
#ifdef __GLIBC__
	(*(int **)&bb_errno) = __errno_location();
#endif

#if !BB_MMU
	/* NOMMU re-exec trick sets high-order bit in first byte of name */
	if (argv[0][0] & 0x80) {
		re_execed = 1;
		argv[0][0] &= 0x7f;
	}
#endif
	applet_name = argv[0];
	if (applet_name[0] == '-')
		applet_name++;
	applet_name = bb_basename(applet_name);

	parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */

	/* Set locale for everybody except 'init' */
	if (ENABLE_LOCALE_SUPPORT && getpid() != 1)
		setlocale(LC_ALL, "");

	run_applet_and_exit(applet_name, argv);
	bb_error_msg_and_die("applet not found");
}