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setmode.c revision 1.17 
      1 /*	$NetBSD: setmode.c,v 1.17 1997/07/21 14:07:31 jtc 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 1.17 1997/07/21 14:07:31 jtc 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 		return (saveset);
    230 	}
    231 
    232 	/*
    233 	 * Build list of structures to set/clear/copy bits as described by
    234 	 * each clause of the symbolic mode.
    235 	 */
    236 	for (;;) {
    237 		/* First, find out which bits might be modified. */
    238 		for (who = 0;; ++p) {
    239 			switch (*p) {
    240 			case 'a':
    241 				who |= STANDARD_BITS;
    242 				break;
    243 			case 'u':
    244 				who |= S_ISUID|S_IRWXU;
    245 				break;
    246 			case 'g':
    247 				who |= S_ISGID|S_IRWXG;
    248 				break;
    249 			case 'o':
    250 				who |= S_IRWXO;
    251 				break;
    252 			default:
    253 				goto getop;
    254 			}
    255 		}
    256 
    257 getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
    258 			free(saveset);
    259 			return (NULL);
    260 		}
    261 		if (op == '=')
    262 			equalopdone = 0;
    263 
    264 		who &= ~S_ISTXT;
    265 		for (perm = 0, permXbits = 0;; ++p) {
    266 			switch (*p) {
    267 			case 'r':
    268 				perm |= S_IRUSR|S_IRGRP|S_IROTH;
    269 				break;
    270 			case 's':
    271 				/*
    272 				 * If specific bits where requested and
    273 				 * only "other" bits ignore set-id.
    274 				 */
    275 				if (who == 0 || (who & ~S_IRWXO))
    276 					perm |= S_ISUID|S_ISGID;
    277 				break;
    278 			case 't':
    279 				/*
    280 				 * If specific bits where requested and
    281 				 * only "other" bits ignore set-id.
    282 				 */
    283 				if (who == 0 || (who & ~S_IRWXO)) {
    284 					who |= S_ISTXT;
    285 					perm |= S_ISTXT;
    286 				}
    287 				break;
    288 			case 'w':
    289 				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
    290 				break;
    291 			case 'X':
    292 				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
    293 				break;
    294 			case 'x':
    295 				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
    296 				break;
    297 			case 'u':
    298 			case 'g':
    299 			case 'o':
    300 				/*
    301 				 * When ever we hit 'u', 'g', or 'o', we have
    302 				 * to flush out any partial mode that we have,
    303 				 * and then do the copying of the mode bits.
    304 				 */
    305 				if (perm) {
    306 					ADDCMD(op, who, perm, mask);
    307 					perm = 0;
    308 				}
    309 				if (op == '=')
    310 					equalopdone = 1;
    311 				if (op == '+' && permXbits) {
    312 					ADDCMD('X', who, permXbits, mask);
    313 					permXbits = 0;
    314 				}
    315 				ADDCMD(*p, who, op, mask);
    316 				break;
    317 
    318 			default:
    319 				/*
    320 				 * Add any permissions that we haven't already
    321 				 * done.
    322 				 */
    323 				if (perm || (op == '=' && !equalopdone)) {
    324 					if (op == '=')
    325 						equalopdone = 1;
    326 					ADDCMD(op, who, perm, mask);
    327 					perm = 0;
    328 				}
    329 				if (permXbits) {
    330 					ADDCMD('X', who, permXbits, mask);
    331 					permXbits = 0;
    332 				}
    333 				goto apply;
    334 			}
    335 		}
    336 
    337 apply:		if (!*p)
    338 			break;
    339 		if (*p != ',')
    340 			goto getop;
    341 		++p;
    342 	}
    343 	set->cmd = 0;
    344 #ifdef SETMODE_DEBUG
    345 	(void)printf("Before compress_mode()\n");
    346 	dumpmode(saveset);
    347 #endif
    348 	compress_mode(saveset);
    349 #ifdef SETMODE_DEBUG
    350 	(void)printf("After compress_mode()\n");
    351 	dumpmode(saveset);
    352 #endif
    353 	return (saveset);
    354 }
    355 
    356 static BITCMD *
    357 addcmd(set, op, who, oparg, mask)
    358 	BITCMD *set;
    359 	register int oparg, who;
    360 	register int op;
    361 	u_int mask;
    362 {
    363 	switch (op) {
    364 	case '=':
    365 		set->cmd = '-';
    366 		set->bits = who ? who : STANDARD_BITS;
    367 		set++;
    368 
    369 		op = '+';
    370 		/* FALLTHROUGH */
    371 	case '+':
    372 	case '-':
    373 	case 'X':
    374 		set->cmd = op;
    375 		set->bits = (who ? who : mask) & oparg;
    376 		break;
    377 
    378 	case 'u':
    379 	case 'g':
    380 	case 'o':
    381 		set->cmd = op;
    382 		if (who) {
    383 			set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
    384 				    ((who & S_IRGRP) ? CMD2_GBITS : 0) |
    385 				    ((who & S_IROTH) ? CMD2_OBITS : 0);
    386 			set->bits = ~0;
    387 		} else {
    388 			set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
    389 			set->bits = mask;
    390 		}
    391 
    392 		if (oparg == '+')
    393 			set->cmd2 |= CMD2_SET;
    394 		else if (oparg == '-')
    395 			set->cmd2 |= CMD2_CLR;
    396 		else if (oparg == '=')
    397 			set->cmd2 |= CMD2_SET|CMD2_CLR;
    398 		break;
    399 	}
    400 	return (set + 1);
    401 }
    402 
    403 #ifdef SETMODE_DEBUG
    404 static void
    405 dumpmode(set)
    406 	register BITCMD *set;
    407 {
    408 	for (; set->cmd; ++set)
    409 		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
    410 		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
    411 		    set->cmd2 & CMD2_CLR ? " CLR" : "",
    412 		    set->cmd2 & CMD2_SET ? " SET" : "",
    413 		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
    414 		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
    415 		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
    416 }
    417 #endif
    418 
    419 /*
    420  * Given an array of bitcmd structures, compress by compacting consecutive
    421  * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
    422  * 'g' and 'o' commands continue to be separate.  They could probably be
    423  * compacted, but it's not worth the effort.
    424  */
    425 static void
    426 compress_mode(set)
    427 	register BITCMD *set;
    428 {
    429 	register BITCMD *nset;
    430 	register int setbits, clrbits, Xbits, op;
    431 
    432 	for (nset = set;;) {
    433 		/* Copy over any 'u', 'g' and 'o' commands. */
    434 		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
    435 			*set++ = *nset++;
    436 			if (!op)
    437 				return;
    438 		}
    439 
    440 		for (setbits = clrbits = Xbits = 0;; nset++) {
    441 			if ((op = nset->cmd) == '-') {
    442 				clrbits |= nset->bits;
    443 				setbits &= ~nset->bits;
    444 				Xbits &= ~nset->bits;
    445 			} else if (op == '+') {
    446 				setbits |= nset->bits;
    447 				clrbits &= ~nset->bits;
    448 				Xbits &= ~nset->bits;
    449 			} else if (op == 'X')
    450 				Xbits |= nset->bits & ~setbits;
    451 			else
    452 				break;
    453 		}
    454 		if (clrbits) {
    455 			set->cmd = '-';
    456 			set->cmd2 = 0;
    457 			set->bits = clrbits;
    458 			set++;
    459 		}
    460 		if (setbits) {
    461 			set->cmd = '+';
    462 			set->cmd2 = 0;
    463 			set->bits = setbits;
    464 			set++;
    465 		}
    466 		if (Xbits) {
    467 			set->cmd = 'X';
    468 			set->cmd2 = 0;
    469 			set->bits = Xbits;
    470 			set++;
    471 		}
    472 	}
    473 }
    474