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setmode.c revision 1.24 
      1 /*	$NetBSD: setmode.c,v 1.24 2000/01/20 02:53:46 mycroft 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. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 #if 0
     42 static char sccsid[] = "@(#)setmode.c	8.2 (Berkeley) 3/25/94";
     43 #else
     44 __RCSID("$NetBSD: setmode.c,v 1.24 2000/01/20 02:53:46 mycroft Exp $");
     45 #endif
     46 #endif /* LIBC_SCCS and not lint */
     47 
     48 #include "namespace.h"
     49 #include <sys/types.h>
     50 #include <sys/stat.h>
     51 
     52 #include <assert.h>
     53 #include <ctype.h>
     54 #include <errno.h>
     55 #include <signal.h>
     56 #include <stdlib.h>
     57 #include <unistd.h>
     58 
     59 #ifdef SETMODE_DEBUG
     60 #include <stdio.h>
     61 #endif
     62 
     63 #ifdef __weak_alias
     64 __weak_alias(getmode,_getmode);
     65 __weak_alias(setmode,_setmode);
     66 #endif
     67 
     68 #define	SET_LEN	6		/* initial # of bitcmd struct to malloc */
     69 #define	SET_LEN_INCR 4		/* # of bitcmd structs to add as needed */
     70 
     71 typedef struct bitcmd {
     72 	char	cmd;
     73 	char	cmd2;
     74 	mode_t	bits;
     75 } BITCMD;
     76 
     77 #define	CMD2_CLR	0x01
     78 #define	CMD2_SET	0x02
     79 #define	CMD2_GBITS	0x04
     80 #define	CMD2_OBITS	0x08
     81 #define	CMD2_UBITS	0x10
     82 
     83 static BITCMD	*addcmd __P((BITCMD *, int, int, int, u_int));
     84 static void	 compress_mode __P((BITCMD *));
     85 #ifdef SETMODE_DEBUG
     86 static void	 dumpmode __P((BITCMD *));
     87 #endif
     88 
     89 /*
     90  * Given the old mode and an array of bitcmd structures, apply the operations
     91  * described in the bitcmd structures to the old mode, and return the new mode.
     92  * Note that there is no '=' command; a strict assignment is just a '-' (clear
     93  * bits) followed by a '+' (set bits).
     94  */
     95 mode_t
     96 getmode(bbox, omode)
     97 	const void *bbox;
     98 	mode_t omode;
     99 {
    100 	const BITCMD *set;
    101 	mode_t clrval, newmode, value;
    102 
    103 	_DIAGASSERT(bbox != NULL);
    104 
    105 	set = (const BITCMD *)bbox;
    106 	newmode = omode;
    107 	for (value = 0;; set++)
    108 		switch(set->cmd) {
    109 		/*
    110 		 * When copying the user, group or other bits around, we "know"
    111 		 * where the bits are in the mode so that we can do shifts to
    112 		 * copy them around.  If we don't use shifts, it gets real
    113 		 * grundgy with lots of single bit checks and bit sets.
    114 		 */
    115 		case 'u':
    116 			value = (newmode & S_IRWXU) >> 6;
    117 			goto common;
    118 
    119 		case 'g':
    120 			value = (newmode & S_IRWXG) >> 3;
    121 			goto common;
    122 
    123 		case 'o':
    124 			value = newmode & S_IRWXO;
    125 common:			if (set->cmd2 & CMD2_CLR) {
    126 				clrval =
    127 				    (set->cmd2 & CMD2_SET) ?  S_IRWXO : value;
    128 				if (set->cmd2 & CMD2_UBITS)
    129 					newmode &= ~((clrval<<6) & set->bits);
    130 				if (set->cmd2 & CMD2_GBITS)
    131 					newmode &= ~((clrval<<3) & set->bits);
    132 				if (set->cmd2 & CMD2_OBITS)
    133 					newmode &= ~(clrval & set->bits);
    134 			}
    135 			if (set->cmd2 & CMD2_SET) {
    136 				if (set->cmd2 & CMD2_UBITS)
    137 					newmode |= (value<<6) & set->bits;
    138 				if (set->cmd2 & CMD2_GBITS)
    139 					newmode |= (value<<3) & set->bits;
    140 				if (set->cmd2 & CMD2_OBITS)
    141 					newmode |= value & set->bits;
    142 			}
    143 			break;
    144 
    145 		case '+':
    146 			newmode |= set->bits;
    147 			break;
    148 
    149 		case '-':
    150 			newmode &= ~set->bits;
    151 			break;
    152 
    153 		case 'X':
    154 			if (omode & (S_IFDIR|S_IXUSR|S_IXGRP|S_IXOTH))
    155 				newmode |= set->bits;
    156 			break;
    157 
    158 		case '\0':
    159 		default:
    160 #ifdef SETMODE_DEBUG
    161 			(void)printf("getmode:%04o -> %04o\n", omode, newmode);
    162 #endif
    163 			return (newmode);
    164 		}
    165 }
    166 
    167 #define	ADDCMD(a, b, c, d)						\
    168 	if (set >= endset) {						\
    169 		BITCMD *newset;				\
    170 		setlen += SET_LEN_INCR;					\
    171 		newset = realloc(saveset, sizeof(BITCMD) * setlen);	\
    172 		if (!saveset)						\
    173 			return (NULL);					\
    174 		set = newset + (set - saveset);				\
    175 		saveset = newset;					\
    176 		endset = newset + (setlen - 2);				\
    177 	}								\
    178 	set = addcmd(set, (a), (b), (c), (d))
    179 
    180 #define	STANDARD_BITS	(S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
    181 
    182 void *
    183 setmode(p)
    184 	const char *p;
    185 {
    186 	int perm, who;
    187 	char op, *ep;
    188 	BITCMD *set, *saveset, *endset;
    189 	sigset_t sigset, sigoset;
    190 	mode_t mask;
    191 	int equalopdone = 0;	/* pacify gcc */
    192 	int permXbits, setlen;
    193 
    194 	if (!*p)
    195 		return (NULL);
    196 
    197 	/*
    198 	 * Get a copy of the mask for the permissions that are mask relative.
    199 	 * Flip the bits, we want what's not set.  Since it's possible that
    200 	 * the caller is opening files inside a signal handler, protect them
    201 	 * as best we can.
    202 	 */
    203 	sigfillset(&sigset);
    204         (void)sigprocmask(SIG_BLOCK, &sigset, &sigoset);
    205 	(void)umask(mask = umask(0));
    206 	mask = ~mask;
    207         (void)sigprocmask(SIG_SETMASK, &sigoset, NULL);
    208 
    209 	setlen = SET_LEN + 2;
    210 
    211 	if ((set = malloc((u_int)(sizeof(BITCMD) * setlen))) == NULL)
    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 		perm = (mode_t)strtol(p, &ep, 8);
    222 		if (*ep || perm & ~(STANDARD_BITS|S_ISTXT)) {
    223 			free(saveset);
    224 			return (NULL);
    225 		}
    226 		ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
    227 		set->cmd = 0;
    228 		return (saveset);
    229 	}
    230 
    231 	/*
    232 	 * Build list of structures to set/clear/copy bits as described by
    233 	 * each clause of the symbolic mode.
    234 	 */
    235 	for (;;) {
    236 		/* First, find out which bits might be modified. */
    237 		for (who = 0;; ++p) {
    238 			switch (*p) {
    239 			case 'a':
    240 				who |= STANDARD_BITS;
    241 				break;
    242 			case 'u':
    243 				who |= S_ISUID|S_IRWXU;
    244 				break;
    245 			case 'g':
    246 				who |= S_ISGID|S_IRWXG;
    247 				break;
    248 			case 'o':
    249 				who |= S_IRWXO;
    250 				break;
    251 			default:
    252 				goto getop;
    253 			}
    254 		}
    255 
    256 getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
    257 			free(saveset);
    258 			return (NULL);
    259 		}
    260 		if (op == '=')
    261 			equalopdone = 0;
    262 
    263 		who &= ~S_ISTXT;
    264 		for (perm = 0, permXbits = 0;; ++p) {
    265 			switch (*p) {
    266 			case 'r':
    267 				perm |= S_IRUSR|S_IRGRP|S_IROTH;
    268 				break;
    269 			case 's':
    270 				/*
    271 				 * If specific bits where requested and
    272 				 * only "other" bits ignore set-id.
    273 				 */
    274 				if (who == 0 || (who & ~S_IRWXO))
    275 					perm |= S_ISUID|S_ISGID;
    276 				break;
    277 			case 't':
    278 				/*
    279 				 * If specific bits where requested and
    280 				 * only "other" bits ignore set-id.
    281 				 */
    282 				if (who == 0 || (who & ~S_IRWXO)) {
    283 					who |= S_ISTXT;
    284 					perm |= S_ISTXT;
    285 				}
    286 				break;
    287 			case 'w':
    288 				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
    289 				break;
    290 			case 'X':
    291 				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
    292 				break;
    293 			case 'x':
    294 				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
    295 				break;
    296 			case 'u':
    297 			case 'g':
    298 			case 'o':
    299 				/*
    300 				 * When ever we hit 'u', 'g', or 'o', we have
    301 				 * to flush out any partial mode that we have,
    302 				 * and then do the copying of the mode bits.
    303 				 */
    304 				if (perm) {
    305 					ADDCMD(op, who, perm, mask);
    306 					perm = 0;
    307 				}
    308 				if (op == '=')
    309 					equalopdone = 1;
    310 				if (op == '+' && permXbits) {
    311 					ADDCMD('X', who, permXbits, mask);
    312 					permXbits = 0;
    313 				}
    314 				ADDCMD(*p, who, op, mask);
    315 				break;
    316 
    317 			default:
    318 				/*
    319 				 * Add any permissions that we haven't already
    320 				 * done.
    321 				 */
    322 				if (perm || (op == '=' && !equalopdone)) {
    323 					if (op == '=')
    324 						equalopdone = 1;
    325 					ADDCMD(op, who, perm, mask);
    326 					perm = 0;
    327 				}
    328 				if (permXbits) {
    329 					ADDCMD('X', who, permXbits, mask);
    330 					permXbits = 0;
    331 				}
    332 				goto apply;
    333 			}
    334 		}
    335 
    336 apply:		if (!*p)
    337 			break;
    338 		if (*p != ',')
    339 			goto getop;
    340 		++p;
    341 	}
    342 	set->cmd = 0;
    343 #ifdef SETMODE_DEBUG
    344 	(void)printf("Before compress_mode()\n");
    345 	dumpmode(saveset);
    346 #endif
    347 	compress_mode(saveset);
    348 #ifdef SETMODE_DEBUG
    349 	(void)printf("After compress_mode()\n");
    350 	dumpmode(saveset);
    351 #endif
    352 	return (saveset);
    353 }
    354 
    355 static BITCMD *
    356 addcmd(set, op, who, oparg, mask)
    357 	BITCMD *set;
    358 	int oparg, who;
    359 	int op;
    360 	u_int mask;
    361 {
    362 
    363 	_DIAGASSERT(set != NULL);
    364 
    365 	switch (op) {
    366 	case '=':
    367 		set->cmd = '-';
    368 		set->bits = who ? who : STANDARD_BITS;
    369 		set++;
    370 
    371 		op = '+';
    372 		/* FALLTHROUGH */
    373 	case '+':
    374 	case '-':
    375 	case 'X':
    376 		set->cmd = op;
    377 		set->bits = (who ? who : mask) & oparg;
    378 		break;
    379 
    380 	case 'u':
    381 	case 'g':
    382 	case 'o':
    383 		set->cmd = op;
    384 		if (who) {
    385 			set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
    386 				    ((who & S_IRGRP) ? CMD2_GBITS : 0) |
    387 				    ((who & S_IROTH) ? CMD2_OBITS : 0);
    388 			set->bits = (mode_t)~0;
    389 		} else {
    390 			set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
    391 			set->bits = mask;
    392 		}
    393 
    394 		if (oparg == '+')
    395 			set->cmd2 |= CMD2_SET;
    396 		else if (oparg == '-')
    397 			set->cmd2 |= CMD2_CLR;
    398 		else if (oparg == '=')
    399 			set->cmd2 |= CMD2_SET|CMD2_CLR;
    400 		break;
    401 	}
    402 	return (set + 1);
    403 }
    404 
    405 #ifdef SETMODE_DEBUG
    406 static void
    407 dumpmode(set)
    408 	BITCMD *set;
    409 {
    410 
    411 	_DIAGASSERT(set != NULL);
    412 
    413 	for (; set->cmd; ++set)
    414 		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
    415 		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
    416 		    set->cmd2 & CMD2_CLR ? " CLR" : "",
    417 		    set->cmd2 & CMD2_SET ? " SET" : "",
    418 		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
    419 		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
    420 		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
    421 }
    422 #endif
    423 
    424 /*
    425  * Given an array of bitcmd structures, compress by compacting consecutive
    426  * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
    427  * 'g' and 'o' commands continue to be separate.  They could probably be
    428  * compacted, but it's not worth the effort.
    429  */
    430 static void
    431 compress_mode(set)
    432 	BITCMD *set;
    433 {
    434 	BITCMD *nset;
    435 	int setbits, clrbits, Xbits, op;
    436 
    437 	_DIAGASSERT(set != NULL);
    438 
    439 	for (nset = set;;) {
    440 		/* Copy over any 'u', 'g' and 'o' commands. */
    441 		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
    442 			*set++ = *nset++;
    443 			if (!op)
    444 				return;
    445 		}
    446 
    447 		for (setbits = clrbits = Xbits = 0;; nset++) {
    448 			if ((op = nset->cmd) == '-') {
    449 				clrbits |= nset->bits;
    450 				setbits &= ~nset->bits;
    451 				Xbits &= ~nset->bits;
    452 			} else if (op == '+') {
    453 				setbits |= nset->bits;
    454 				clrbits &= ~nset->bits;
    455 				Xbits &= ~nset->bits;
    456 			} else if (op == 'X')
    457 				Xbits |= nset->bits & ~setbits;
    458 			else
    459 				break;
    460 		}
    461 		if (clrbits) {
    462 			set->cmd = '-';
    463 			set->cmd2 = 0;
    464 			set->bits = clrbits;
    465 			set++;
    466 		}
    467 		if (setbits) {
    468 			set->cmd = '+';
    469 			set->cmd2 = 0;
    470 			set->bits = setbits;
    471 			set++;
    472 		}
    473 		if (Xbits) {
    474 			set->cmd = 'X';
    475 			set->cmd2 = 0;
    476 			set->bits = Xbits;
    477 			set++;
    478 		}
    479 	}
    480 }
    481