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setmode.c revision 1.18 
      1 /*	$NetBSD: setmode.c,v 1.18 1997/10/08 17:19:13 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 1.18 1997/10/08 17:19:13 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 <ctype.h>
     53 #include <errno.h>
     54 #include <signal.h>
     55 #include <stdlib.h>
     56 #include <unistd.h>
     57 
     58 #ifdef SETMODE_DEBUG
     59 #include <stdio.h>
     60 #endif
     61 
     62 #ifdef __weak_alias
     63 __weak_alias(getmode,_getmode);
     64 __weak_alias(setmode,_setmode);
     65 #endif
     66 
     67 #define	SET_LEN	6		/* initial # of bitcmd struct to malloc */
     68 #define	SET_LEN_INCR 4		/* # of bitcmd structs to add as needed */
     69 
     70 typedef struct bitcmd {
     71 	char	cmd;
     72 	char	cmd2;
     73 	mode_t	bits;
     74 } BITCMD;
     75 
     76 #define	CMD2_CLR	0x01
     77 #define	CMD2_SET	0x02
     78 #define	CMD2_GBITS	0x04
     79 #define	CMD2_OBITS	0x08
     80 #define	CMD2_UBITS	0x10
     81 
     82 static BITCMD	*addcmd __P((BITCMD *, int, int, int, u_int));
     83 static void	 compress_mode __P((BITCMD *));
     84 #ifdef SETMODE_DEBUG
     85 static void	 dumpmode __P((BITCMD *));
     86 #endif
     87 
     88 /*
     89  * Given the old mode and an array of bitcmd structures, apply the operations
     90  * described in the bitcmd structures to the old mode, and return the new mode.
     91  * Note that there is no '=' command; a strict assignment is just a '-' (clear
     92  * bits) followed by a '+' (set bits).
     93  */
     94 mode_t
     95 getmode(bbox, omode)
     96 	const void *bbox;
     97 	mode_t omode;
     98 {
     99 	register const BITCMD *set;
    100 	register mode_t clrval, newmode, value;
    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)						\
    165 	if (set >= endset) {						\
    166 		register BITCMD *newset;				\
    167 		setlen += SET_LEN_INCR;					\
    168 		newset = realloc(saveset, sizeof(BITCMD) * setlen);	\
    169 		if (!saveset)						\
    170 			return (NULL);					\
    171 		set = newset + (set - saveset);				\
    172 		saveset = newset;					\
    173 		endset = newset + (setlen - 2);				\
    174 	}								\
    175 	set = addcmd(set, (a), (b), (c), (d))
    176 
    177 #define	STANDARD_BITS	(S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
    178 
    179 void *
    180 setmode(p)
    181 	register const char *p;
    182 {
    183 	register int perm, who;
    184 	register char op;
    185 	BITCMD *set, *saveset, *endset;
    186 	sigset_t sigset, sigoset;
    187 	mode_t mask;
    188 	int equalopdone = 0;	/* pacify gcc */
    189 	int permXbits, setlen;
    190 
    191 	if (!*p)
    192 		return (NULL);
    193 
    194 	/*
    195 	 * Get a copy of the mask for the permissions that are mask relative.
    196 	 * Flip the bits, we want what's not set.  Since it's possible that
    197 	 * the caller is opening files inside a signal handler, protect them
    198 	 * as best we can.
    199 	 */
    200 	sigfillset(&sigset);
    201         (void)sigprocmask(SIG_BLOCK, &sigset, &sigoset);
    202 	(void)umask(mask = umask(0));
    203 	mask = ~mask;
    204         (void)sigprocmask(SIG_SETMASK, &sigoset, NULL);
    205 
    206 	setlen = SET_LEN + 2;
    207 
    208 	if ((set = malloc((u_int)(sizeof(BITCMD) * setlen))) == NULL)
    209 		return (NULL);
    210 	saveset = set;
    211 	endset = set + (setlen - 2);
    212 
    213 	/*
    214 	 * If an absolute number, get it and return; disallow non-octal digits
    215 	 * or illegal bits.
    216 	 */
    217 	if (isdigit(*p)) {
    218 		perm = (mode_t)strtol(p, NULL, 8);
    219 		if (perm & ~(STANDARD_BITS|S_ISTXT)) {
    220 			free(saveset);
    221 			return (NULL);
    222 		}
    223 		while (*++p)
    224 			if (*p < '0' || *p > '7') {
    225 				free(saveset);
    226 				return (NULL);
    227 			}
    228 		ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
    229 		set->cmd = 0;
    230 		return (saveset);
    231 	}
    232 
    233 	/*
    234 	 * Build list of structures to set/clear/copy bits as described by
    235 	 * each clause of the symbolic mode.
    236 	 */
    237 	for (;;) {
    238 		/* First, find out which bits might be modified. */
    239 		for (who = 0;; ++p) {
    240 			switch (*p) {
    241 			case 'a':
    242 				who |= STANDARD_BITS;
    243 				break;
    244 			case 'u':
    245 				who |= S_ISUID|S_IRWXU;
    246 				break;
    247 			case 'g':
    248 				who |= S_ISGID|S_IRWXG;
    249 				break;
    250 			case 'o':
    251 				who |= S_IRWXO;
    252 				break;
    253 			default:
    254 				goto getop;
    255 			}
    256 		}
    257 
    258 getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
    259 			free(saveset);
    260 			return (NULL);
    261 		}
    262 		if (op == '=')
    263 			equalopdone = 0;
    264 
    265 		who &= ~S_ISTXT;
    266 		for (perm = 0, permXbits = 0;; ++p) {
    267 			switch (*p) {
    268 			case 'r':
    269 				perm |= S_IRUSR|S_IRGRP|S_IROTH;
    270 				break;
    271 			case 's':
    272 				/*
    273 				 * If specific bits where requested and
    274 				 * only "other" bits ignore set-id.
    275 				 */
    276 				if (who == 0 || (who & ~S_IRWXO))
    277 					perm |= S_ISUID|S_ISGID;
    278 				break;
    279 			case 't':
    280 				/*
    281 				 * If specific bits where requested and
    282 				 * only "other" bits ignore set-id.
    283 				 */
    284 				if (who == 0 || (who & ~S_IRWXO)) {
    285 					who |= S_ISTXT;
    286 					perm |= S_ISTXT;
    287 				}
    288 				break;
    289 			case 'w':
    290 				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
    291 				break;
    292 			case 'X':
    293 				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
    294 				break;
    295 			case 'x':
    296 				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
    297 				break;
    298 			case 'u':
    299 			case 'g':
    300 			case 'o':
    301 				/*
    302 				 * When ever we hit 'u', 'g', or 'o', we have
    303 				 * to flush out any partial mode that we have,
    304 				 * and then do the copying of the mode bits.
    305 				 */
    306 				if (perm) {
    307 					ADDCMD(op, who, perm, mask);
    308 					perm = 0;
    309 				}
    310 				if (op == '=')
    311 					equalopdone = 1;
    312 				if (op == '+' && permXbits) {
    313 					ADDCMD('X', who, permXbits, mask);
    314 					permXbits = 0;
    315 				}
    316 				ADDCMD(*p, who, op, mask);
    317 				break;
    318 
    319 			default:
    320 				/*
    321 				 * Add any permissions that we haven't already
    322 				 * done.
    323 				 */
    324 				if (perm || (op == '=' && !equalopdone)) {
    325 					if (op == '=')
    326 						equalopdone = 1;
    327 					ADDCMD(op, who, perm, mask);
    328 					perm = 0;
    329 				}
    330 				if (permXbits) {
    331 					ADDCMD('X', who, permXbits, mask);
    332 					permXbits = 0;
    333 				}
    334 				goto apply;
    335 			}
    336 		}
    337 
    338 apply:		if (!*p)
    339 			break;
    340 		if (*p != ',')
    341 			goto getop;
    342 		++p;
    343 	}
    344 	set->cmd = 0;
    345 #ifdef SETMODE_DEBUG
    346 	(void)printf("Before compress_mode()\n");
    347 	dumpmode(saveset);
    348 #endif
    349 	compress_mode(saveset);
    350 #ifdef SETMODE_DEBUG
    351 	(void)printf("After compress_mode()\n");
    352 	dumpmode(saveset);
    353 #endif
    354 	return (saveset);
    355 }
    356 
    357 static BITCMD *
    358 addcmd(set, op, who, oparg, mask)
    359 	BITCMD *set;
    360 	register int oparg, who;
    361 	register int op;
    362 	u_int mask;
    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 = ~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 	register BITCMD *set;
    408 {
    409 	for (; set->cmd; ++set)
    410 		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
    411 		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
    412 		    set->cmd2 & CMD2_CLR ? " CLR" : "",
    413 		    set->cmd2 & CMD2_SET ? " SET" : "",
    414 		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
    415 		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
    416 		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
    417 }
    418 #endif
    419 
    420 /*
    421  * Given an array of bitcmd structures, compress by compacting consecutive
    422  * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
    423  * 'g' and 'o' commands continue to be separate.  They could probably be
    424  * compacted, but it's not worth the effort.
    425  */
    426 static void
    427 compress_mode(set)
    428 	register BITCMD *set;
    429 {
    430 	register BITCMD *nset;
    431 	register int setbits, clrbits, Xbits, op;
    432 
    433 	for (nset = set;;) {
    434 		/* Copy over any 'u', 'g' and 'o' commands. */
    435 		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
    436 			*set++ = *nset++;
    437 			if (!op)
    438 				return;
    439 		}
    440 
    441 		for (setbits = clrbits = Xbits = 0;; nset++) {
    442 			if ((op = nset->cmd) == '-') {
    443 				clrbits |= nset->bits;
    444 				setbits &= ~nset->bits;
    445 				Xbits &= ~nset->bits;
    446 			} else if (op == '+') {
    447 				setbits |= nset->bits;
    448 				clrbits &= ~nset->bits;
    449 				Xbits &= ~nset->bits;
    450 			} else if (op == 'X')
    451 				Xbits |= nset->bits & ~setbits;
    452 			else
    453 				break;
    454 		}
    455 		if (clrbits) {
    456 			set->cmd = '-';
    457 			set->cmd2 = 0;
    458 			set->bits = clrbits;
    459 			set++;
    460 		}
    461 		if (setbits) {
    462 			set->cmd = '+';
    463 			set->cmd2 = 0;
    464 			set->bits = setbits;
    465 			set++;
    466 		}
    467 		if (Xbits) {
    468 			set->cmd = 'X';
    469 			set->cmd2 = 0;
    470 			set->bits = Xbits;
    471 			set++;
    472 		}
    473 	}
    474 }
    475