summaryrefslogtreecommitdiff
path: root/applets/applets.c
blob: 9dc69f36fbda273cc37d73a11fd94b62cccfe22e (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
/* 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.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * 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.
 *
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "busybox.h"

#undef APPLET
#undef APPLET_NOUSAGE
#undef PROTOTYPES
#include "applets.h"

static struct BB_applet *applet_using;

/* The -1 arises because of the {0,NULL,0,-1} entry above. */
const size_t NUM_APPLETS = (sizeof (applets) / sizeof (struct BB_applet) - 1);


#ifdef CONFIG_FEATURE_SUID

static void check_suid (struct BB_applet *app);

#ifdef CONFIG_FEATURE_SUID_CONFIG

#include <sys/stat.h>
#include <ctype.h>
#include "pwd_.h"
#include "grp_.h"

static void parse_config_file (void);

#define CONFIG_FILE "/etc/busybox.conf"

/* applets [] is const, so we have to define this "override" structure */
struct BB_suid_config
{
  struct BB_applet *m_applet;

  uid_t m_uid;
  gid_t m_gid;
  mode_t m_mode;

  struct BB_suid_config *m_next;
};

static struct BB_suid_config *suid_config;
static int suid_cfg_readable;

#endif /* CONFIG_FEATURE_SUID_CONFIG */

#endif /* CONFIG_FEATURE_SUID */



extern void
bb_show_usage (void)
{
  const char *format_string;
  const char *usage_string = usage_messages;
  int i;

  for (i = applet_using - applets; i > 0;) {
	if (!*usage_string++) {
	  --i;
	}
  }

  format_string = "%s\n\nUsage: %s %s\n\n";
  if (*usage_string == '\b')
	format_string = "%s\n\nNo help available.\n\n";
  fprintf (stderr, format_string, bb_msg_full_version, applet_using->name,
		   usage_string);

  exit (EXIT_FAILURE);
}

static int
applet_name_compare (const void *x, const void *y)
{
  const char *name = x;
  const struct BB_applet *applet = y;

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

extern const size_t NUM_APPLETS;

struct BB_applet *
find_applet_by_name (const char *name)
{
  return bsearch (name, applets, NUM_APPLETS, sizeof (struct BB_applet),
				  applet_name_compare);
}

void
run_applet_by_name (const char *name, int argc, char **argv)
{
  static int recurse_level = 0;
  extern int been_there_done_that;      /* From busybox.c */

#ifdef CONFIG_FEATURE_SUID_CONFIG
  if (recurse_level == 0)
	parse_config_file ();
#endif

  recurse_level++;
  /* Do a binary search to find the applet entry given the name. */
  if ((applet_using = find_applet_by_name (name)) != NULL) {
	bb_applet_name = applet_using->name;
	if (argv[1] && strcmp (argv[1], "--help") == 0) {
	  if (strcmp (applet_using->name, "busybox") == 0) {
		if (argv[2])
		  applet_using = find_applet_by_name (argv[2]);
		else
		  applet_using = NULL;
	  }
	  if (applet_using)
		bb_show_usage ();
	  been_there_done_that = 1;
	  busybox_main (0, NULL);
	}
#ifdef CONFIG_FEATURE_SUID
	check_suid (applet_using);
#endif

	exit ((*(applet_using->main)) (argc, argv));
  }
  /* Just in case they have renamed busybox - Check argv[1] */
  if (recurse_level == 1) {
	run_applet_by_name ("busybox", argc, argv);
  }
  recurse_level--;
}


#ifdef CONFIG_FEATURE_SUID

#ifdef CONFIG_FEATURE_SUID_CONFIG

/* 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;
}

#endif


void
check_suid (struct BB_applet *applet)
{
  uid_t ruid = getuid ();               /* real [ug]id */
  uid_t rgid = getgid ();

#ifdef CONFIG_FEATURE_SUID_CONFIG
  if (suid_cfg_readable) {
	struct BB_suid_config *sct;

	for (sct = suid_config; sct; sct = sct->m_next) {
	  if (sct->m_applet == applet)
		break;
	}
	if (sct) {
	  mode_t 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!");

	  if ((sct->m_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {     /* *both* have to be set for sgid */
		if (setegid (sct->m_gid))
		  bb_error_msg_and_die
			("BusyBox binary has insufficient rights to set proper GID for applet!");
	  } else
		setgid (rgid);                  /* no sgid -> drop */

	  if (sct->m_mode & S_ISUID) {
		if (seteuid (sct->m_uid))
		  bb_error_msg_and_die
			("BusyBox binary has insufficient rights to set proper UID for applet!");
	  } else
		setuid (ruid);                  /* no suid -> drop */
	} else {
		/* default: drop all priviledges */
	  setgid (rgid);
	  setuid (ruid);
	}
	return;
  } else {
#ifndef CONFIG_FEATURE_SUID_CONFIG_QUIET
	static int onetime = 0;

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

  if (applet->need_suid == _BB_SUID_ALWAYS) {
	if (geteuid () != 0)
	  bb_error_msg_and_die ("This applet requires root priviledges!");
  } else if (applet->need_suid == _BB_SUID_NEVER) {
	setgid (rgid);                          /* drop all priviledges */
	setuid (ruid);
  }
}

#ifdef CONFIG_FEATURE_SUID_CONFIG

/* 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 (char *) bb_skip_whitespace(s);
}


#define parse_error(x)  { err=x; goto pe_label; }

/* Don't depend on the tools to combine strings. */
static const char config_file[] = CONFIG_FILE;

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

/* 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[] = {
	/*  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 */
};

static void parse_config_file(void)
{
	struct BB_suid_config *sct_head;
	struct BB_suid_config *sct;
	struct BB_applet *applet;
	FILE *f;
	char *err;
	char *s;
	char *e;
	int i, lc, section;
	char buffer[256];
	struct stat st;

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

	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"))		/* Can not open? */
		) {
		return;
	}

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

	do {
		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. */
		if (!*(s = get_trimmed_slice(s, strchrnul(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. */
			if (!(e = strchr(s, ']'))	/* 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). */
			if (!!(e = strchr(s, '='))) {
				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. */
			if ((applet = find_applet_by_name(s))) {
				/* 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 = (char *) bb_skip_whitespace(e+1);

				for (i=0 ; i < 3 ; i++) {
					const char *q;
					if (!*(q = strchrnul(mode_chars + 5*i, *e++))) {
						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 = (char *) bb_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... */
				{
					char *e2;

					sct->m_uid = strtoul(s, &e2, 10);
					if (*e2 || (s == e2)) {
						struct passwd *pwd;
						if (!(pwd = getpwnam(s))) {
							parse_error("user");
						}
						sct->m_uid = pwd->pw_uid;
					}

					sct->m_gid = strtoul(e, &e2, 10);
					if (*e2 || (e == e2)) {
						struct group *grp;
						if (!(grp = getgrnam(e))) {
							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 desireable.
		 * 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, err);

	fclose(f);
	/* Release any allocated memory before returning. */
	while (sct_head) {
		sct = sct_head->m_next;
		free(sct_head);
		sct_head = sct;
	}
	return;
}

#endif

#endif

/* END CODE */
/*
  Local Variables:
  c-file-style: "linux"
  c-basic-offset: 4
  tab-width: 4
End:
*/