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setmode.c revision 1.30 
      1 /*	$NetBSD: setmode.c,v 1.30 2003/08/07 16:42:56 agc 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 1.30 2003/08/07 16:42:56 agc 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 <unistd.h>
     54 
     55 #ifdef SETMODE_DEBUG
     56 #include <stdio.h>
     57 #endif
     58 
     59 #ifdef __weak_alias
     60 __weak_alias(getmode,_getmode)
     61 __weak_alias(setmode,_setmode)
     62 #endif
     63 
     64 #define	SET_LEN	6		/* initial # of bitcmd struct to malloc */
     65 #define	SET_LEN_INCR 4		/* # of bitcmd structs to add as needed */
     66 
     67 typedef struct bitcmd {
     68 	char	cmd;
     69 	char	cmd2;
     70 	mode_t	bits;
     71 } BITCMD;
     72 
     73 #define	CMD2_CLR	0x01
     74 #define	CMD2_SET	0x02
     75 #define	CMD2_GBITS	0x04
     76 #define	CMD2_OBITS	0x08
     77 #define	CMD2_UBITS	0x10
     78 
     79 static BITCMD	*addcmd __P((BITCMD *, int, int, int, u_int));
     80 static void	 compress_mode __P((BITCMD *));
     81 #ifdef SETMODE_DEBUG
     82 static void	 dumpmode __P((BITCMD *));
     83 #endif
     84 
     85 /*
     86  * Given the old mode and an array of bitcmd structures, apply the operations
     87  * described in the bitcmd structures to the old mode, and return the new mode.
     88  * Note that there is no '=' command; a strict assignment is just a '-' (clear
     89  * bits) followed by a '+' (set bits).
     90  */
     91 mode_t
     92 getmode(bbox, omode)
     93 	const void *bbox;
     94 	mode_t omode;
     95 {
     96 	const BITCMD *set;
     97 	mode_t clrval, newmode, value;
     98 
     99 	_DIAGASSERT(bbox != NULL);
    100 
    101 	set = (const BITCMD *)bbox;
    102 	newmode = omode;
    103 	for (value = 0;; set++)
    104 		switch(set->cmd) {
    105 		/*
    106 		 * When copying the user, group or other bits around, we "know"
    107 		 * where the bits are in the mode so that we can do shifts to
    108 		 * copy them around.  If we don't use shifts, it gets real
    109 		 * grundgy with lots of single bit checks and bit sets.
    110 		 */
    111 		case 'u':
    112 			value = (newmode & S_IRWXU) >> 6;
    113 			goto common;
    114 
    115 		case 'g':
    116 			value = (newmode & S_IRWXG) >> 3;
    117 			goto common;
    118 
    119 		case 'o':
    120 			value = newmode & S_IRWXO;
    121 common:			if (set->cmd2 & CMD2_CLR) {
    122 				clrval =
    123 				    (set->cmd2 & CMD2_SET) ?  S_IRWXO : value;
    124 				if (set->cmd2 & CMD2_UBITS)
    125 					newmode &= ~((clrval<<6) & set->bits);
    126 				if (set->cmd2 & CMD2_GBITS)
    127 					newmode &= ~((clrval<<3) & set->bits);
    128 				if (set->cmd2 & CMD2_OBITS)
    129 					newmode &= ~(clrval & set->bits);
    130 			}
    131 			if (set->cmd2 & CMD2_SET) {
    132 				if (set->cmd2 & CMD2_UBITS)
    133 					newmode |= (value<<6) & set->bits;
    134 				if (set->cmd2 & CMD2_GBITS)
    135 					newmode |= (value<<3) & set->bits;
    136 				if (set->cmd2 & CMD2_OBITS)
    137 					newmode |= value & set->bits;
    138 			}
    139 			break;
    140 
    141 		case '+':
    142 			newmode |= set->bits;
    143 			break;
    144 
    145 		case '-':
    146 			newmode &= ~set->bits;
    147 			break;
    148 
    149 		case 'X':
    150 			if (omode & (S_IFDIR|S_IXUSR|S_IXGRP|S_IXOTH))
    151 				newmode |= set->bits;
    152 			break;
    153 
    154 		case '\0':
    155 		default:
    156 #ifdef SETMODE_DEBUG
    157 			(void)printf("getmode:%04o -> %04o\n", omode, newmode);
    158 #endif
    159 			return (newmode);
    160 		}
    161 }
    162 
    163 #define	ADDCMD(a, b, c, d) do {						\
    164 	if (set >= endset) {						\
    165 		BITCMD *newset;						\
    166 		setlen += SET_LEN_INCR;					\
    167 		newset = realloc(saveset, sizeof(BITCMD) * setlen);	\
    168 		if (newset == NULL) {					\
    169 			free(saveset);					\
    170 			return (NULL);					\
    171 		}							\
    172 		set = newset + (set - saveset);				\
    173 		saveset = newset;					\
    174 		endset = newset + (setlen - 2);				\
    175 	}								\
    176 	set = addcmd(set, (a), (b), (c), (d));				\
    177 } while (/*CONSTCOND*/0)
    178 
    179 #define	STANDARD_BITS	(S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
    180 
    181 void *
    182 setmode(p)
    183 	const char *p;
    184 {
    185 	int perm, who;
    186 	char op, *ep;
    187 	BITCMD *set, *saveset, *endset;
    188 	sigset_t signset, sigoset;
    189 	mode_t mask;
    190 	int equalopdone = 0;	/* pacify gcc */
    191 	int permXbits, setlen;
    192 
    193 	if (!*p)
    194 		return (NULL);
    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 
    210 	if ((set = malloc((u_int)(sizeof(BITCMD) * setlen))) == NULL)
    211 		return (NULL);
    212 	saveset = set;
    213 	endset = set + (setlen - 2);
    214 
    215 	/*
    216 	 * If an absolute number, get it and return; disallow non-octal digits
    217 	 * or illegal bits.
    218 	 */
    219 	if (isdigit((unsigned char)*p)) {
    220 		perm = (mode_t)strtol(p, &ep, 8);
    221 		if (*ep || perm & ~(STANDARD_BITS|S_ISTXT)) {
    222 			free(saveset);
    223 			return (NULL);
    224 		}
    225 		ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
    226 		set->cmd = 0;
    227 		return (saveset);
    228 	}
    229 
    230 	/*
    231 	 * Build list of structures to set/clear/copy bits as described by
    232 	 * each clause of the symbolic mode.
    233 	 */
    234 	for (;;) {
    235 		/* First, find out which bits might be modified. */
    236 		for (who = 0;; ++p) {
    237 			switch (*p) {
    238 			case 'a':
    239 				who |= STANDARD_BITS;
    240 				break;
    241 			case 'u':
    242 				who |= S_ISUID|S_IRWXU;
    243 				break;
    244 			case 'g':
    245 				who |= S_ISGID|S_IRWXG;
    246 				break;
    247 			case 'o':
    248 				who |= S_IRWXO;
    249 				break;
    250 			default:
    251 				goto getop;
    252 			}
    253 		}
    254 
    255 getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
    256 			free(saveset);
    257 			return (NULL);
    258 		}
    259 		if (op == '=')
    260 			equalopdone = 0;
    261 
    262 		who &= ~S_ISTXT;
    263 		for (perm = 0, permXbits = 0;; ++p) {
    264 			switch (*p) {
    265 			case 'r':
    266 				perm |= S_IRUSR|S_IRGRP|S_IROTH;
    267 				break;
    268 			case 's':
    269 				/*
    270 				 * If specific bits where requested and
    271 				 * only "other" bits ignore set-id.
    272 				 */
    273 				if (who == 0 || (who & ~S_IRWXO))
    274 					perm |= S_ISUID|S_ISGID;
    275 				break;
    276 			case 't':
    277 				/*
    278 				 * If specific bits where requested and
    279 				 * only "other" bits ignore set-id.
    280 				 */
    281 				if (who == 0 || (who & ~S_IRWXO)) {
    282 					who |= S_ISTXT;
    283 					perm |= S_ISTXT;
    284 				}
    285 				break;
    286 			case 'w':
    287 				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
    288 				break;
    289 			case 'X':
    290 				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
    291 				break;
    292 			case 'x':
    293 				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
    294 				break;
    295 			case 'u':
    296 			case 'g':
    297 			case 'o':
    298 				/*
    299 				 * When ever we hit 'u', 'g', or 'o', we have
    300 				 * to flush out any partial mode that we have,
    301 				 * and then do the copying of the mode bits.
    302 				 */
    303 				if (perm) {
    304 					ADDCMD(op, who, perm, mask);
    305 					perm = 0;
    306 				}
    307 				if (op == '=')
    308 					equalopdone = 1;
    309 				if (op == '+' && permXbits) {
    310 					ADDCMD('X', who, permXbits, mask);
    311 					permXbits = 0;
    312 				}
    313 				ADDCMD(*p, who, op, mask);
    314 				break;
    315 
    316 			default:
    317 				/*
    318 				 * Add any permissions that we haven't already
    319 				 * done.
    320 				 */
    321 				if (perm || (op == '=' && !equalopdone)) {
    322 					if (op == '=')
    323 						equalopdone = 1;
    324 					ADDCMD(op, who, perm, mask);
    325 					perm = 0;
    326 				}
    327 				if (permXbits) {
    328 					ADDCMD('X', who, permXbits, mask);
    329 					permXbits = 0;
    330 				}
    331 				goto apply;
    332 			}
    333 		}
    334 
    335 apply:		if (!*p)
    336 			break;
    337 		if (*p != ',')
    338 			goto getop;
    339 		++p;
    340 	}
    341 	set->cmd = 0;
    342 #ifdef SETMODE_DEBUG
    343 	(void)printf("Before compress_mode()\n");
    344 	dumpmode(saveset);
    345 #endif
    346 	compress_mode(saveset);
    347 #ifdef SETMODE_DEBUG
    348 	(void)printf("After compress_mode()\n");
    349 	dumpmode(saveset);
    350 #endif
    351 	return (saveset);
    352 }
    353 
    354 static BITCMD *
    355 addcmd(set, op, who, oparg, mask)
    356 	BITCMD *set;
    357 	int oparg, who;
    358 	int op;
    359 	u_int mask;
    360 {
    361 
    362 	_DIAGASSERT(set != NULL);
    363 
    364 	switch (op) {
    365 	case '=':
    366 		set->cmd = '-';
    367 		set->bits = who ? who : STANDARD_BITS;
    368 		set++;
    369 
    370 		op = '+';
    371 		/* FALLTHROUGH */
    372 	case '+':
    373 	case '-':
    374 	case 'X':
    375 		set->cmd = op;
    376 		set->bits = (who ? who : mask) & oparg;
    377 		break;
    378 
    379 	case 'u':
    380 	case 'g':
    381 	case 'o':
    382 		set->cmd = op;
    383 		if (who) {
    384 			set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
    385 				    ((who & S_IRGRP) ? CMD2_GBITS : 0) |
    386 				    ((who & S_IROTH) ? CMD2_OBITS : 0);
    387 			set->bits = (mode_t)~0;
    388 		} else {
    389 			set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
    390 			set->bits = mask;
    391 		}
    392 
    393 		if (oparg == '+')
    394 			set->cmd2 |= CMD2_SET;
    395 		else if (oparg == '-')
    396 			set->cmd2 |= CMD2_CLR;
    397 		else if (oparg == '=')
    398 			set->cmd2 |= CMD2_SET|CMD2_CLR;
    399 		break;
    400 	}
    401 	return (set + 1);
    402 }
    403 
    404 #ifdef SETMODE_DEBUG
    405 static void
    406 dumpmode(set)
    407 	BITCMD *set;
    408 {
    409 
    410 	_DIAGASSERT(set != NULL);
    411 
    412 	for (; set->cmd; ++set)
    413 		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
    414 		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
    415 		    set->cmd2 & CMD2_CLR ? " CLR" : "",
    416 		    set->cmd2 & CMD2_SET ? " SET" : "",
    417 		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
    418 		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
    419 		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
    420 }
    421 #endif
    422 
    423 /*
    424  * Given an array of bitcmd structures, compress by compacting consecutive
    425  * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
    426  * 'g' and 'o' commands continue to be separate.  They could probably be
    427  * compacted, but it's not worth the effort.
    428  */
    429 static void
    430 compress_mode(set)
    431 	BITCMD *set;
    432 {
    433 	BITCMD *nset;
    434 	int setbits, clrbits, Xbits, op;
    435 
    436 	_DIAGASSERT(set != NULL);
    437 
    438 	for (nset = set;;) {
    439 		/* Copy over any 'u', 'g' and 'o' commands. */
    440 		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
    441 			*set++ = *nset++;
    442 			if (!op)
    443 				return;
    444 		}
    445 
    446 		for (setbits = clrbits = Xbits = 0;; nset++) {
    447 			if ((op = nset->cmd) == '-') {
    448 				clrbits |= nset->bits;
    449 				setbits &= ~nset->bits;
    450 				Xbits &= ~nset->bits;
    451 			} else if (op == '+') {
    452 				setbits |= nset->bits;
    453 				clrbits &= ~nset->bits;
    454 				Xbits &= ~nset->bits;
    455 			} else if (op == 'X')
    456 				Xbits |= nset->bits & ~setbits;
    457 			else
    458 				break;
    459 		}
    460 		if (clrbits) {
    461 			set->cmd = '-';
    462 			set->cmd2 = 0;
    463 			set->bits = clrbits;
    464 			set++;
    465 		}
    466 		if (setbits) {
    467 			set->cmd = '+';
    468 			set->cmd2 = 0;
    469 			set->bits = setbits;
    470 			set++;
    471 		}
    472 		if (Xbits) {
    473 			set->cmd = 'X';
    474 			set->cmd2 = 0;
    475 			set->bits = Xbits;
    476 			set++;
    477 		}
    478 	}
    479 }
    480