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      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
     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 *
    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 *
    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
    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
    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