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setmode.c revision 1.32 
      1 /*	$NetBSD: setmode.c,v 1.32 2012/03/20 16:36:05 matt 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 1.32 2012/03/20 16:36:05 matt 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(bbox, omode)
     94 	const void *bbox;
     95 	mode_t omode;
     96 {
     97 	const BITCMD *set;
     98 	mode_t clrval, newmode, value;
     99 
    100 	_DIAGASSERT(bbox != NULL);
    101 
    102 	set = (const BITCMD *)bbox;
    103 	newmode = omode;
    104 	for (value = 0;; set++)
    105 		switch(set->cmd) {
    106 		/*
    107 		 * When copying the user, group or other bits around, we "know"
    108 		 * where the bits are in the mode so that we can do shifts to
    109 		 * copy them around.  If we don't use shifts, it gets real
    110 		 * grundgy with lots of single bit checks and bit sets.
    111 		 */
    112 		case 'u':
    113 			value = (newmode & S_IRWXU) >> 6;
    114 			goto common;
    115 
    116 		case 'g':
    117 			value = (newmode & S_IRWXG) >> 3;
    118 			goto common;
    119 
    120 		case 'o':
    121 			value = newmode & S_IRWXO;
    122 common:			if (set->cmd2 & CMD2_CLR) {
    123 				clrval =
    124 				    (set->cmd2 & CMD2_SET) ?  S_IRWXO : value;
    125 				if (set->cmd2 & CMD2_UBITS)
    126 					newmode &= ~((clrval<<6) & set->bits);
    127 				if (set->cmd2 & CMD2_GBITS)
    128 					newmode &= ~((clrval<<3) & set->bits);
    129 				if (set->cmd2 & CMD2_OBITS)
    130 					newmode &= ~(clrval & set->bits);
    131 			}
    132 			if (set->cmd2 & CMD2_SET) {
    133 				if (set->cmd2 & CMD2_UBITS)
    134 					newmode |= (value<<6) & set->bits;
    135 				if (set->cmd2 & CMD2_GBITS)
    136 					newmode |= (value<<3) & set->bits;
    137 				if (set->cmd2 & CMD2_OBITS)
    138 					newmode |= value & set->bits;
    139 			}
    140 			break;
    141 
    142 		case '+':
    143 			newmode |= set->bits;
    144 			break;
    145 
    146 		case '-':
    147 			newmode &= ~set->bits;
    148 			break;
    149 
    150 		case 'X':
    151 			if (omode & (S_IFDIR|S_IXUSR|S_IXGRP|S_IXOTH))
    152 				newmode |= set->bits;
    153 			break;
    154 
    155 		case '\0':
    156 		default:
    157 #ifdef SETMODE_DEBUG
    158 			(void)printf("getmode:%04o -> %04o\n", omode, newmode);
    159 #endif
    160 			return (newmode);
    161 		}
    162 }
    163 
    164 #define	ADDCMD(a, b, c, d) do {						\
    165 	if (set >= endset) {						\
    166 		BITCMD *newset;						\
    167 		setlen += SET_LEN_INCR;					\
    168 		newset = realloc(saveset, sizeof(BITCMD) * setlen);	\
    169 		if (newset == NULL)					\
    170 			goto out;					\
    171 		set = newset + (set - saveset);				\
    172 		saveset = newset;					\
    173 		endset = newset + (setlen - 2);				\
    174 	}								\
    175 	set = addcmd(set, (mode_t)(a), (mode_t)(b), (mode_t)(c), (d));	\
    176 } while (/*CONSTCOND*/0)
    177 
    178 #define	STANDARD_BITS	(S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
    179 
    180 void *
    181 setmode(p)
    182 	const char *p;
    183 {
    184 	int serrno;
    185 	char op, *ep;
    186 	BITCMD *set, *saveset, *endset;
    187 	sigset_t signset, sigoset;
    188 	mode_t mask, perm, permXbits, who;
    189 	long lval;
    190 	int equalopdone = 0;	/* pacify gcc */
    191 	int setlen;
    192 
    193 	if (!*p) {
    194 		errno = EINVAL;
    195 		return NULL;
    196 	}
    197 
    198 	/*
    199 	 * Get a copy of the mask for the permissions that are mask relative.
    200 	 * Flip the bits, we want what's not set.  Since it's possible that
    201 	 * the caller is opening files inside a signal handler, protect them
    202 	 * as best we can.
    203 	 */
    204 	sigfillset(&signset);
    205 	(void)sigprocmask(SIG_BLOCK, &signset, &sigoset);
    206 	(void)umask(mask = umask(0));
    207 	mask = ~mask;
    208 	(void)sigprocmask(SIG_SETMASK, &sigoset, NULL);
    209 
    210 	setlen = SET_LEN + 2;
    211 
    212 	if ((set = malloc((u_int)(sizeof(BITCMD) * setlen))) == NULL)
    213 		return (NULL);
    214 	saveset = set;
    215 	endset = set + (setlen - 2);
    216 
    217 	/*
    218 	 * If an absolute number, get it and return; disallow non-octal digits
    219 	 * or illegal bits.
    220 	 */
    221 	if (isdigit((unsigned char)*p)) {
    222 		errno = 0;
    223 		lval = strtol(p, &ep, 8);
    224 		if (*ep) {
    225 			errno = EINVAL;
    226 			goto out;
    227 		}
    228 		if (errno == ERANGE && (lval == LONG_MAX || lval == LONG_MIN))
    229 			goto out;
    230 		if (lval & ~(STANDARD_BITS|S_ISTXT)) {
    231 			errno = EINVAL;
    232 			goto out;
    233 		}
    234 		perm = (mode_t)lval;
    235 		ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
    236 		set->cmd = 0;
    237 		return (saveset);
    238 	}
    239 
    240 	/*
    241 	 * Build list of structures to set/clear/copy bits as described by
    242 	 * each clause of the symbolic mode.
    243 	 */
    244 	for (;;) {
    245 		/* First, find out which bits might be modified. */
    246 		for (who = 0;; ++p) {
    247 			switch (*p) {
    248 			case 'a':
    249 				who |= STANDARD_BITS;
    250 				break;
    251 			case 'u':
    252 				who |= S_ISUID|S_IRWXU;
    253 				break;
    254 			case 'g':
    255 				who |= S_ISGID|S_IRWXG;
    256 				break;
    257 			case 'o':
    258 				who |= S_IRWXO;
    259 				break;
    260 			default:
    261 				goto getop;
    262 			}
    263 		}
    264 
    265 getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
    266 			errno = EINVAL;
    267 			goto out;
    268 		}
    269 		if (op == '=')
    270 			equalopdone = 0;
    271 
    272 		who &= ~S_ISTXT;
    273 		for (perm = 0, permXbits = 0;; ++p) {
    274 			switch (*p) {
    275 			case 'r':
    276 				perm |= S_IRUSR|S_IRGRP|S_IROTH;
    277 				break;
    278 			case 's':
    279 				/*
    280 				 * If specific bits where requested and
    281 				 * only "other" bits ignore set-id.
    282 				 */
    283 				if (who == 0 || (who & ~S_IRWXO))
    284 					perm |= S_ISUID|S_ISGID;
    285 				break;
    286 			case 't':
    287 				/*
    288 				 * If specific bits where requested and
    289 				 * only "other" bits ignore set-id.
    290 				 */
    291 				if (who == 0 || (who & ~S_IRWXO)) {
    292 					who |= S_ISTXT;
    293 					perm |= S_ISTXT;
    294 				}
    295 				break;
    296 			case 'w':
    297 				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
    298 				break;
    299 			case 'X':
    300 				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
    301 				break;
    302 			case 'x':
    303 				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
    304 				break;
    305 			case 'u':
    306 			case 'g':
    307 			case 'o':
    308 				/*
    309 				 * When ever we hit 'u', 'g', or 'o', we have
    310 				 * to flush out any partial mode that we have,
    311 				 * and then do the copying of the mode bits.
    312 				 */
    313 				if (perm) {
    314 					ADDCMD(op, who, perm, mask);
    315 					perm = 0;
    316 				}
    317 				if (op == '=')
    318 					equalopdone = 1;
    319 				if (op == '+' && permXbits) {
    320 					ADDCMD('X', who, permXbits, mask);
    321 					permXbits = 0;
    322 				}
    323 				ADDCMD(*p, who, op, mask);
    324 				break;
    325 
    326 			default:
    327 				/*
    328 				 * Add any permissions that we haven't already
    329 				 * done.
    330 				 */
    331 				if (perm || (op == '=' && !equalopdone)) {
    332 					if (op == '=')
    333 						equalopdone = 1;
    334 					ADDCMD(op, who, perm, mask);
    335 					perm = 0;
    336 				}
    337 				if (permXbits) {
    338 					ADDCMD('X', who, permXbits, mask);
    339 					permXbits = 0;
    340 				}
    341 				goto apply;
    342 			}
    343 		}
    344 
    345 apply:		if (!*p)
    346 			break;
    347 		if (*p != ',')
    348 			goto getop;
    349 		++p;
    350 	}
    351 	set->cmd = 0;
    352 #ifdef SETMODE_DEBUG
    353 	(void)printf("Before compress_mode()\n");
    354 	dumpmode(saveset);
    355 #endif
    356 	compress_mode(saveset);
    357 #ifdef SETMODE_DEBUG
    358 	(void)printf("After compress_mode()\n");
    359 	dumpmode(saveset);
    360 #endif
    361 	return (saveset);
    362 out:
    363 	serrno = errno;
    364 	free(saveset);
    365 	errno = serrno;
    366 	return NULL;
    367 }
    368 
    369 static BITCMD *
    370 addcmd(BITCMD *set, mode_t oparg, mode_t who, mode_t op, mode_t mask)
    371 {
    372 
    373 	_DIAGASSERT(set != NULL);
    374 
    375 	switch (op) {
    376 	case '=':
    377 		set->cmd = '-';
    378 		set->bits = who ? who : STANDARD_BITS;
    379 		set++;
    380 
    381 		op = '+';
    382 		/* FALLTHROUGH */
    383 	case '+':
    384 	case '-':
    385 	case 'X':
    386 		set->cmd = op;
    387 		set->bits = (who ? who : mask) & oparg;
    388 		break;
    389 
    390 	case 'u':
    391 	case 'g':
    392 	case 'o':
    393 		set->cmd = op;
    394 		if (who) {
    395 			set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
    396 				    ((who & S_IRGRP) ? CMD2_GBITS : 0) |
    397 				    ((who & S_IROTH) ? CMD2_OBITS : 0);
    398 			set->bits = (mode_t)~0;
    399 		} else {
    400 			set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
    401 			set->bits = mask;
    402 		}
    403 
    404 		if (oparg == '+')
    405 			set->cmd2 |= CMD2_SET;
    406 		else if (oparg == '-')
    407 			set->cmd2 |= CMD2_CLR;
    408 		else if (oparg == '=')
    409 			set->cmd2 |= CMD2_SET|CMD2_CLR;
    410 		break;
    411 	}
    412 	return (set + 1);
    413 }
    414 
    415 #ifdef SETMODE_DEBUG
    416 static void
    417 dumpmode(BITCMD *set)
    418 {
    419 
    420 	_DIAGASSERT(set != NULL);
    421 
    422 	for (; set->cmd; ++set)
    423 		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
    424 		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
    425 		    set->cmd2 & CMD2_CLR ? " CLR" : "",
    426 		    set->cmd2 & CMD2_SET ? " SET" : "",
    427 		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
    428 		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
    429 		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
    430 }
    431 #endif
    432 
    433 /*
    434  * Given an array of bitcmd structures, compress by compacting consecutive
    435  * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
    436  * 'g' and 'o' commands continue to be separate.  They could probably be
    437  * compacted, but it's not worth the effort.
    438  */
    439 static void
    440 compress_mode(BITCMD *set)
    441 {
    442 	BITCMD *nset;
    443 	int setbits, clrbits, Xbits, op;
    444 
    445 	_DIAGASSERT(set != NULL);
    446 
    447 	for (nset = set;;) {
    448 		/* Copy over any 'u', 'g' and 'o' commands. */
    449 		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
    450 			*set++ = *nset++;
    451 			if (!op)
    452 				return;
    453 		}
    454 
    455 		for (setbits = clrbits = Xbits = 0;; nset++) {
    456 			if ((op = nset->cmd) == '-') {
    457 				clrbits |= nset->bits;
    458 				setbits &= ~nset->bits;
    459 				Xbits &= ~nset->bits;
    460 			} else if (op == '+') {
    461 				setbits |= nset->bits;
    462 				clrbits &= ~nset->bits;
    463 				Xbits &= ~nset->bits;
    464 			} else if (op == 'X')
    465 				Xbits |= nset->bits & ~setbits;
    466 			else
    467 				break;
    468 		}
    469 		if (clrbits) {
    470 			set->cmd = '-';
    471 			set->cmd2 = 0;
    472 			set->bits = clrbits;
    473 			set++;
    474 		}
    475 		if (setbits) {
    476 			set->cmd = '+';
    477 			set->cmd2 = 0;
    478 			set->bits = setbits;
    479 			set++;
    480 		}
    481 		if (Xbits) {
    482 			set->cmd = 'X';
    483 			set->cmd2 = 0;
    484 			set->bits = Xbits;
    485 			set++;
    486 		}
    487 	}
    488 }
    489