1 /* $NetBSD: setmode.c,v 1.38 2022/04/19 20:32:15 rillig Exp $ */
2
3 /*
4 * Copyright (c) 1989, 1993, 1994
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Dave Borman at Cray Research, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #if defined(LIBC_SCCS) && !defined(lint)
37 #if 0
38 static char sccsid[] = "@(#)setmode.c 8.2 (Berkeley) 3/25/94";
39 #else
40 __RCSID("$NetBSD: setmode.c,v 1.38 2022/04/19 20:32:15 rillig Exp $");
41 #endif
42 #endif /* LIBC_SCCS and not lint */
43
44 #include "namespace.h"
45 #include <sys/types.h>
46 #include <sys/stat.h>
47
48 #include <assert.h>
49 #include <ctype.h>
50 #include <errno.h>
51 #include <signal.h>
52 #include <stdlib.h>
53 #include <limits.h>
54 #include <unistd.h>
55
56 #ifdef SETMODE_DEBUG
57 #include <stdio.h>
58 #endif
59
60 #ifdef __weak_alias
61 __weak_alias(getmode,_getmode)
62 __weak_alias(setmode,_setmode)
63 #endif
64
65 #define SET_LEN 6 /* initial # of bitcmd struct to malloc */
66 #define SET_LEN_INCR 4 /* # of bitcmd structs to add as needed */
67
68 typedef struct bitcmd {
69 char cmd;
70 char cmd2;
71 mode_t bits;
72 } BITCMD;
73
74 #define CMD2_CLR 0x01
75 #define CMD2_SET 0x02
76 #define CMD2_GBITS 0x04
77 #define CMD2_OBITS 0x08
78 #define CMD2_UBITS 0x10
79
80 static BITCMD *addcmd(BITCMD *, mode_t, mode_t, mode_t, mode_t);
81 static void compress_mode(BITCMD *);
82 #ifdef SETMODE_DEBUG
83 static void dumpmode(BITCMD *);
84 #endif
85
86 /*
87 * Given the old mode and an array of bitcmd structures, apply the operations
88 * described in the bitcmd structures to the old mode, and return the new mode.
89 * Note that there is no '=' command; a strict assignment is just a '-' (clear
90 * bits) followed by a '+' (set bits).
91 */
92 mode_t
getmode(const void * bbox,mode_t omode)93 getmode(const void *bbox, mode_t omode)
94 {
95 const BITCMD *set;
96 mode_t clrval, newmode, value;
97
98 _DIAGASSERT(bbox != NULL);
99
100 set = (const BITCMD *)bbox;
101 newmode = omode;
102 for (value = 0;; set++)
103 switch(set->cmd) {
104 /*
105 * When copying the user, group or other bits around, we "know"
106 * where the bits are in the mode so that we can do shifts to
107 * copy them around. If we don't use shifts, it gets real
108 * grundgy with lots of single bit checks and bit sets.
109 */
110 case 'u':
111 value = (newmode & S_IRWXU) >> 6;
112 goto common;
113
114 case 'g':
115 value = (newmode & S_IRWXG) >> 3;
116 goto common;
117
118 case 'o':
119 value = newmode & S_IRWXO;
120 common: if (set->cmd2 & CMD2_CLR) {
121 clrval =
122 (set->cmd2 & CMD2_SET) ? S_IRWXO : value;
123 if (set->cmd2 & CMD2_UBITS)
124 newmode &= ~((clrval<<6) & set->bits);
125 if (set->cmd2 & CMD2_GBITS)
126 newmode &= ~((clrval<<3) & set->bits);
127 if (set->cmd2 & CMD2_OBITS)
128 newmode &= ~(clrval & set->bits);
129 }
130 if (set->cmd2 & CMD2_SET) {
131 if (set->cmd2 & CMD2_UBITS)
132 newmode |= (value<<6) & set->bits;
133 if (set->cmd2 & CMD2_GBITS)
134 newmode |= (value<<3) & set->bits;
135 if (set->cmd2 & CMD2_OBITS)
136 newmode |= value & set->bits;
137 }
138 break;
139
140 case '+':
141 newmode |= set->bits;
142 break;
143
144 case '-':
145 newmode &= ~set->bits;
146 break;
147
148 case 'X':
149 if (omode & (S_IFDIR|S_IXUSR|S_IXGRP|S_IXOTH))
150 newmode |= set->bits;
151 break;
152
153 case '\0':
154 default:
155 #ifdef SETMODE_DEBUG
156 (void)printf("getmode:%04o -> %04o\n", omode, newmode);
157 #endif
158 return (newmode);
159 }
160 }
161
162 #define ADDCMD(a, b, c, d) do { \
163 if (set >= endset) { \
164 BITCMD *newset; \
165 setlen += SET_LEN_INCR; \
166 newset = saveset; \
167 errno = reallocarr(&newset, setlen, sizeof(*newset)); \
168 if (errno) \
169 goto out; \
170 set = newset + (set - saveset); \
171 saveset = newset; \
172 endset = newset + (setlen - 2); \
173 } \
174 set = addcmd(set, (mode_t)(a), (mode_t)(b), (mode_t)(c), (d)); \
175 } while (0)
176
177 #define STANDARD_BITS (S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
178
179 void *
setmode(const char * p)180 setmode(const char *p)
181 {
182 int serrno;
183 char op, *ep;
184 BITCMD *set, *saveset, *endset;
185 sigset_t signset, sigoset;
186 mode_t mask, perm, permXbits, who;
187 long lval;
188 int equalopdone = 0; /* pacify gcc */
189 int setlen;
190
191 if (!*p) {
192 errno = EINVAL;
193 return NULL;
194 }
195
196 /*
197 * Get a copy of the mask for the permissions that are mask relative.
198 * Flip the bits, we want what's not set. Since it's possible that
199 * the caller is opening files inside a signal handler, protect them
200 * as best we can.
201 */
202 sigfillset(&signset);
203 (void)sigprocmask(SIG_BLOCK, &signset, &sigoset);
204 (void)umask(mask = umask(0));
205 mask = ~mask;
206 (void)sigprocmask(SIG_SETMASK, &sigoset, NULL);
207
208 setlen = SET_LEN + 2;
209 set = NULL;
210 errno = reallocarr(&set, setlen, sizeof(*set));
211 if (errno)
212 return NULL;
213 saveset = set;
214 endset = set + (setlen - 2);
215
216 /*
217 * If an absolute number, get it and return; disallow non-octal digits
218 * or illegal bits.
219 */
220 if (isdigit((unsigned char)*p)) {
221 errno = 0;
222 lval = strtol(p, &ep, 8);
223 if (*ep) {
224 errno = EINVAL;
225 goto out;
226 }
227 if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN))
228 goto out;
229 if (lval & ~(STANDARD_BITS|S_ISTXT)) {
230 errno = EINVAL;
231 goto out;
232 }
233 perm = (mode_t)lval;
234 ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
235 set->cmd = 0;
236 return (saveset);
237 }
238
239 /*
240 * Build list of structures to set/clear/copy bits as described by
241 * each clause of the symbolic mode.
242 */
243 for (;;) {
244 /* First, find out which bits might be modified. */
245 for (who = 0;; ++p) {
246 switch (*p) {
247 case 'a':
248 who |= STANDARD_BITS;
249 break;
250 case 'u':
251 who |= S_ISUID|S_IRWXU;
252 break;
253 case 'g':
254 who |= S_ISGID|S_IRWXG;
255 break;
256 case 'o':
257 who |= S_IRWXO;
258 break;
259 default:
260 goto getop;
261 }
262 }
263
264 getop: if ((op = *p++) != '+' && op != '-' && op != '=') {
265 errno = EINVAL;
266 goto out;
267 }
268 if (op == '=')
269 equalopdone = 0;
270
271 who &= ~S_ISTXT;
272 for (perm = 0, permXbits = 0;; ++p) {
273 switch (*p) {
274 case 'r':
275 perm |= S_IRUSR|S_IRGRP|S_IROTH;
276 break;
277 case 's':
278 /*
279 * If specific bits where requested and
280 * only "other" bits ignore set-id.
281 */
282 if (who == 0 || (who & ~S_IRWXO))
283 perm |= S_ISUID|S_ISGID;
284 break;
285 case 't':
286 /*
287 * If specific bits where requested and
288 * only "other" bits ignore set-id.
289 */
290 if (who == 0 || (who & ~S_IRWXO)) {
291 who |= S_ISTXT;
292 perm |= S_ISTXT;
293 }
294 break;
295 case 'w':
296 perm |= S_IWUSR|S_IWGRP|S_IWOTH;
297 break;
298 case 'X':
299 permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
300 break;
301 case 'x':
302 perm |= S_IXUSR|S_IXGRP|S_IXOTH;
303 break;
304 case 'u':
305 case 'g':
306 case 'o':
307 /*
308 * When ever we hit 'u', 'g', or 'o', we have
309 * to flush out any partial mode that we have,
310 * and then do the copying of the mode bits.
311 */
312 if (perm) {
313 ADDCMD(op, who, perm, mask);
314 perm = 0;
315 }
316 if (op == '=')
317 equalopdone = 1;
318 if (op == '+' && permXbits) {
319 ADDCMD('X', who, permXbits, mask);
320 permXbits = 0;
321 }
322 ADDCMD(*p, who, op, mask);
323 break;
324
325 default:
326 /*
327 * Add any permissions that we haven't already
328 * done.
329 */
330 if (perm || (op == '=' && !equalopdone)) {
331 if (op == '=')
332 equalopdone = 1;
333 ADDCMD(op, who, perm, mask);
334 perm = 0;
335 }
336 if (permXbits) {
337 ADDCMD('X', who, permXbits, mask);
338 permXbits = 0;
339 }
340 goto apply;
341 }
342 }
343
344 apply: if (!*p)
345 break;
346 if (*p != ',')
347 goto getop;
348 ++p;
349 }
350 set->cmd = 0;
351 #ifdef SETMODE_DEBUG
352 (void)printf("Before compress_mode()\n");
353 dumpmode(saveset);
354 #endif
355 compress_mode(saveset);
356 #ifdef SETMODE_DEBUG
357 (void)printf("After compress_mode()\n");
358 dumpmode(saveset);
359 #endif
360 return (saveset);
361 out:
362 serrno = errno;
363 free(saveset);
364 errno = serrno;
365 return NULL;
366 }
367
368 static BITCMD *
addcmd(BITCMD * set,mode_t op,mode_t who,mode_t oparg,mode_t mask)369 addcmd(BITCMD *set, mode_t op, mode_t who, mode_t oparg, mode_t mask)
370 {
371
372 _DIAGASSERT(set != NULL);
373
374 switch (op) {
375 case '=':
376 set->cmd = '-';
377 set->bits = who ? who : STANDARD_BITS;
378 set++;
379
380 op = '+';
381 /* FALLTHROUGH */
382 case '+':
383 case '-':
384 case 'X':
385 set->cmd = op;
386 set->bits = (who ? who : mask) & oparg;
387 break;
388
389 case 'u':
390 case 'g':
391 case 'o':
392 set->cmd = op;
393 if (who) {
394 set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
395 ((who & S_IRGRP) ? CMD2_GBITS : 0) |
396 ((who & S_IROTH) ? CMD2_OBITS : 0);
397 set->bits = (mode_t)~0;
398 } else {
399 set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
400 set->bits = mask;
401 }
402
403 if (oparg == '+')
404 set->cmd2 |= CMD2_SET;
405 else if (oparg == '-')
406 set->cmd2 |= CMD2_CLR;
407 else if (oparg == '=')
408 set->cmd2 |= CMD2_SET|CMD2_CLR;
409 break;
410 }
411 return (set + 1);
412 }
413
414 #ifdef SETMODE_DEBUG
415 static void
dumpmode(BITCMD * set)416 dumpmode(BITCMD *set)
417 {
418
419 _DIAGASSERT(set != NULL);
420
421 for (; set->cmd; ++set)
422 (void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
423 set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
424 set->cmd2 & CMD2_CLR ? " CLR" : "",
425 set->cmd2 & CMD2_SET ? " SET" : "",
426 set->cmd2 & CMD2_UBITS ? " UBITS" : "",
427 set->cmd2 & CMD2_GBITS ? " GBITS" : "",
428 set->cmd2 & CMD2_OBITS ? " OBITS" : "");
429 }
430 #endif
431
432 /*
433 * Given an array of bitcmd structures, compress by compacting consecutive
434 * '+', '-' and 'X' commands into at most 3 commands, one of each. The 'u',
435 * 'g' and 'o' commands continue to be separate. They could probably be
436 * compacted, but it's not worth the effort.
437 */
438 static void
compress_mode(BITCMD * set)439 compress_mode(BITCMD *set)
440 {
441 BITCMD *nset;
442 int setbits, clrbits, Xbits, op;
443
444 _DIAGASSERT(set != NULL);
445
446 for (nset = set;;) {
447 /* Copy over any 'u', 'g' and 'o' commands. */
448 while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
449 *set++ = *nset++;
450 if (!op)
451 return;
452 }
453
454 for (setbits = clrbits = Xbits = 0;; nset++) {
455 if ((op = nset->cmd) == '-') {
456 clrbits |= nset->bits;
457 setbits &= ~nset->bits;
458 Xbits &= ~nset->bits;
459 } else if (op == '+') {
460 setbits |= nset->bits;
461 clrbits &= ~nset->bits;
462 Xbits &= ~nset->bits;
463 } else if (op == 'X')
464 Xbits |= nset->bits & ~setbits;
465 else
466 break;
467 }
468 if (clrbits) {
469 set->cmd = '-';
470 set->cmd2 = 0;
471 set->bits = clrbits;
472 set++;
473 }
474 if (setbits) {
475 set->cmd = '+';
476 set->cmd2 = 0;
477 set->bits = setbits;
478 set++;
479 }
480 if (Xbits) {
481 set->cmd = 'X';
482 set->cmd2 = 0;
483 set->bits = Xbits;
484 set++;
485 }
486 }
487 }
488