1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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 "namespace.h"
36#include <sys/types.h>
37#include <sys/stat.h>
38#include <sys/sysctl.h>
39
40#include <ctype.h>
41#include <errno.h>
42#include <limits.h>
43#include <signal.h>
44#include <stddef.h>
45#include <stdlib.h>
46#include <unistd.h>
47
48#ifdef SETMODE_DEBUG
49#include <stdio.h>
50#endif
51#include "un-namespace.h"
52#include "libc_private.h"
53
54#define	SET_LEN	6		/* initial # of bitcmd struct to malloc */
55#define	SET_LEN_INCR 4		/* # of bitcmd structs to add as needed */
56
57typedef struct bitcmd {
58	char	cmd;
59	char	cmd2;
60	mode_t	bits;
61} BITCMD;
62
63#define	CMD2_CLR	0x01
64#define	CMD2_SET	0x02
65#define	CMD2_GBITS	0x04
66#define	CMD2_OBITS	0x08
67#define	CMD2_UBITS	0x10
68
69static mode_t	 get_current_umask(void);
70static BITCMD	*addcmd(BITCMD *, mode_t, mode_t, mode_t, mode_t);
71static void	 compress_mode(BITCMD *);
72#ifdef SETMODE_DEBUG
73static void	 dumpmode(BITCMD *);
74#endif
75
76/*
77 * Given the old mode and an array of bitcmd structures, apply the operations
78 * described in the bitcmd structures to the old mode, and return the new mode.
79 * Note that there is no '=' command; a strict assignment is just a '-' (clear
80 * bits) followed by a '+' (set bits).
81 */
82mode_t
83getmode(const void *bbox, mode_t omode)
84{
85	const BITCMD *set;
86	mode_t clrval, newmode, value;
87
88	set = (const BITCMD *)bbox;
89	newmode = omode;
90	for (value = 0;; set++)
91		switch(set->cmd) {
92		/*
93		 * When copying the user, group or other bits around, we "know"
94		 * where the bits are in the mode so that we can do shifts to
95		 * copy them around.  If we don't use shifts, it gets real
96		 * grundgy with lots of single bit checks and bit sets.
97		 */
98		case 'u':
99			value = (newmode & S_IRWXU) >> 6;
100			goto common;
101
102		case 'g':
103			value = (newmode & S_IRWXG) >> 3;
104			goto common;
105
106		case 'o':
107			value = newmode & S_IRWXO;
108common:			if (set->cmd2 & CMD2_CLR) {
109				clrval =
110				    (set->cmd2 & CMD2_SET) ?  S_IRWXO : value;
111				if (set->cmd2 & CMD2_UBITS)
112					newmode &= ~((clrval<<6) & set->bits);
113				if (set->cmd2 & CMD2_GBITS)
114					newmode &= ~((clrval<<3) & set->bits);
115				if (set->cmd2 & CMD2_OBITS)
116					newmode &= ~(clrval & set->bits);
117			}
118			if (set->cmd2 & CMD2_SET) {
119				if (set->cmd2 & CMD2_UBITS)
120					newmode |= (value<<6) & set->bits;
121				if (set->cmd2 & CMD2_GBITS)
122					newmode |= (value<<3) & set->bits;
123				if (set->cmd2 & CMD2_OBITS)
124					newmode |= value & set->bits;
125			}
126			break;
127
128		case '+':
129			newmode |= set->bits;
130			break;
131
132		case '-':
133			newmode &= ~set->bits;
134			break;
135
136		case 'X':
137			if (omode & (S_IFDIR|S_IXUSR|S_IXGRP|S_IXOTH))
138				newmode |= set->bits;
139			break;
140
141		case '\0':
142		default:
143#ifdef SETMODE_DEBUG
144			(void)printf("getmode:%04o -> %04o\n", omode, newmode);
145#endif
146			return (newmode);
147		}
148}
149
150#define	ADDCMD(a, b, c, d)						\
151	if (set >= endset) {						\
152		BITCMD *newset;						\
153		setlen += SET_LEN_INCR;					\
154		newset = reallocarray(saveset, setlen, sizeof(BITCMD));	\
155		if (newset == NULL)					\
156			goto out;					\
157		set = newset + (set - saveset);				\
158		saveset = newset;					\
159		endset = newset + (setlen - 2);				\
160	}								\
161	set = addcmd(set, (mode_t)(a), (mode_t)(b), (mode_t)(c), (d))
162
163#define	STANDARD_BITS	(S_ISUID|S_ISGID|S_IRWXU|S_IRWXG|S_IRWXO)
164
165void *
166setmode(const char *p)
167{
168	int serrno;
169	char op, *ep;
170	BITCMD *set, *saveset, *endset;
171	mode_t mask, perm, permXbits, who;
172	long perml;
173	int equalopdone;
174	u_int setlen;
175
176	if (!*p) {
177		errno = EINVAL;
178		return (NULL);
179	}
180
181	/*
182	 * Get a copy of the mask for the permissions that are mask relative.
183	 * Flip the bits, we want what's not set.
184	 */
185	mask = ~get_current_umask();
186
187	setlen = SET_LEN + 2;
188
189	if ((set = malloc(setlen * sizeof(BITCMD))) == NULL)
190		return (NULL);
191	saveset = set;
192	endset = set + (setlen - 2);
193
194	/*
195	 * If an absolute number, get it and return; disallow non-octal digits
196	 * or illegal bits.
197	 */
198	if (isdigit((unsigned char)*p)) {
199		errno = 0;
200		perml = strtol(p, &ep, 8);
201		if (*ep) {
202			errno = EINVAL;
203			goto out;
204		}
205		if (errno == ERANGE && (perml == LONG_MAX || perml == LONG_MIN))
206			goto out;
207		if (perml & ~(STANDARD_BITS|S_ISTXT)) {
208			errno = EINVAL;
209			goto out;
210		}
211		perm = (mode_t)perml;
212		ADDCMD('=', (STANDARD_BITS|S_ISTXT), perm, mask);
213		set->cmd = 0;
214		return (saveset);
215	}
216
217	/*
218	 * Build list of structures to set/clear/copy bits as described by
219	 * each clause of the symbolic mode.
220	 */
221	equalopdone = 0;
222	for (;;) {
223		/* First, find out which bits might be modified. */
224		for (who = 0;; ++p) {
225			switch (*p) {
226			case 'a':
227				who |= STANDARD_BITS;
228				break;
229			case 'u':
230				who |= S_ISUID|S_IRWXU;
231				break;
232			case 'g':
233				who |= S_ISGID|S_IRWXG;
234				break;
235			case 'o':
236				who |= S_IRWXO;
237				break;
238			default:
239				goto getop;
240			}
241		}
242
243getop:		if ((op = *p++) != '+' && op != '-' && op != '=') {
244			errno = EINVAL;
245			goto out;
246		}
247		if (op == '=')
248			equalopdone = 0;
249
250		who &= ~S_ISTXT;
251		for (perm = 0, permXbits = 0;; ++p) {
252			switch (*p) {
253			case 'r':
254				perm |= S_IRUSR|S_IRGRP|S_IROTH;
255				break;
256			case 's':
257				/* If only "other" bits ignore set-id. */
258				if (!who || who & ~S_IRWXO)
259					perm |= S_ISUID|S_ISGID;
260				break;
261			case 't':
262				/* If only "other" bits ignore sticky. */
263				if (!who || who & ~S_IRWXO) {
264					who |= S_ISTXT;
265					perm |= S_ISTXT;
266				}
267				break;
268			case 'w':
269				perm |= S_IWUSR|S_IWGRP|S_IWOTH;
270				break;
271			case 'X':
272				permXbits = S_IXUSR|S_IXGRP|S_IXOTH;
273				break;
274			case 'x':
275				perm |= S_IXUSR|S_IXGRP|S_IXOTH;
276				break;
277			case 'u':
278			case 'g':
279			case 'o':
280				/*
281				 * When ever we hit 'u', 'g', or 'o', we have
282				 * to flush out any partial mode that we have,
283				 * and then do the copying of the mode bits.
284				 */
285				if (perm) {
286					ADDCMD(op, who, perm, mask);
287					perm = 0;
288				}
289				if (op == '=')
290					equalopdone = 1;
291				if (op == '+' && permXbits) {
292					ADDCMD('X', who, permXbits, mask);
293					permXbits = 0;
294				}
295				ADDCMD(*p, who, op, mask);
296				break;
297
298			default:
299				/*
300				 * Add any permissions that we haven't already
301				 * done.
302				 */
303				if (perm || (op == '=' && !equalopdone)) {
304					if (op == '=')
305						equalopdone = 1;
306					ADDCMD(op, who, perm, mask);
307					perm = 0;
308				}
309				if (permXbits) {
310					ADDCMD('X', who, permXbits, mask);
311					permXbits = 0;
312				}
313				goto apply;
314			}
315		}
316
317apply:		if (!*p)
318			break;
319		if (*p != ',')
320			goto getop;
321		++p;
322	}
323	set->cmd = 0;
324#ifdef SETMODE_DEBUG
325	(void)printf("Before compress_mode()\n");
326	dumpmode(saveset);
327#endif
328	compress_mode(saveset);
329#ifdef SETMODE_DEBUG
330	(void)printf("After compress_mode()\n");
331	dumpmode(saveset);
332#endif
333	return (saveset);
334out:
335	serrno = errno;
336	free(saveset);
337	errno = serrno;
338	return NULL;
339}
340
341static mode_t
342get_current_umask(void)
343{
344	sigset_t sigset, sigoset;
345	size_t len;
346	mode_t mask;
347	u_short smask;
348
349#ifdef KERN_PROC_UMASK
350	/*
351	 * First try requesting the umask without temporarily modifying it.
352	 * Note that this does not work if the sysctl
353	 * security.bsd.unprivileged_proc_debug is set to 0.
354	 */
355	len = sizeof(smask);
356	if (sysctl((int[4]){ CTL_KERN, KERN_PROC, KERN_PROC_UMASK, 0 },
357	    4, &smask, &len, NULL, 0) == 0)
358		return (smask);
359#endif
360	/*
361	 * Since it's possible that the caller is opening files inside a signal
362	 * handler, protect them as best we can.
363	 */
364	sigfillset(&sigset);
365	(void)__libc_sigprocmask(SIG_BLOCK, &sigset, &sigoset);
366	(void)umask(mask = umask(0));
367	(void)__libc_sigprocmask(SIG_SETMASK, &sigoset, NULL);
368	return (mask);
369}
370
371static BITCMD *
372addcmd(BITCMD *set, mode_t op, mode_t who, mode_t oparg, mode_t mask)
373{
374	switch (op) {
375	case '=':
376		set->cmd = '-';
377		set->bits = who ? who : STANDARD_BITS;
378		set++;
379
380		op = '+';
381		/* FALLTHROUGH */
382	case '+':
383	case '-':
384	case 'X':
385		set->cmd = op;
386		set->bits = (who ? who : mask) & oparg;
387		break;
388
389	case 'u':
390	case 'g':
391	case 'o':
392		set->cmd = op;
393		if (who) {
394			set->cmd2 = ((who & S_IRUSR) ? CMD2_UBITS : 0) |
395				    ((who & S_IRGRP) ? CMD2_GBITS : 0) |
396				    ((who & S_IROTH) ? CMD2_OBITS : 0);
397			set->bits = (mode_t)~0;
398		} else {
399			set->cmd2 = CMD2_UBITS | CMD2_GBITS | CMD2_OBITS;
400			set->bits = mask;
401		}
402
403		if (oparg == '+')
404			set->cmd2 |= CMD2_SET;
405		else if (oparg == '-')
406			set->cmd2 |= CMD2_CLR;
407		else if (oparg == '=')
408			set->cmd2 |= CMD2_SET|CMD2_CLR;
409		break;
410	}
411	return (set + 1);
412}
413
414#ifdef SETMODE_DEBUG
415static void
416dumpmode(BITCMD *set)
417{
418	for (; set->cmd; ++set)
419		(void)printf("cmd: '%c' bits %04o%s%s%s%s%s%s\n",
420		    set->cmd, set->bits, set->cmd2 ? " cmd2:" : "",
421		    set->cmd2 & CMD2_CLR ? " CLR" : "",
422		    set->cmd2 & CMD2_SET ? " SET" : "",
423		    set->cmd2 & CMD2_UBITS ? " UBITS" : "",
424		    set->cmd2 & CMD2_GBITS ? " GBITS" : "",
425		    set->cmd2 & CMD2_OBITS ? " OBITS" : "");
426}
427#endif
428
429/*
430 * Given an array of bitcmd structures, compress by compacting consecutive
431 * '+', '-' and 'X' commands into at most 3 commands, one of each.  The 'u',
432 * 'g' and 'o' commands continue to be separate.  They could probably be
433 * compacted, but it's not worth the effort.
434 */
435static void
436compress_mode(BITCMD *set)
437{
438	BITCMD *nset;
439	int setbits, clrbits, Xbits, op;
440
441	for (nset = set;;) {
442		/* Copy over any 'u', 'g' and 'o' commands. */
443		while ((op = nset->cmd) != '+' && op != '-' && op != 'X') {
444			*set++ = *nset++;
445			if (!op)
446				return;
447		}
448
449		for (setbits = clrbits = Xbits = 0;; nset++) {
450			if ((op = nset->cmd) == '-') {
451				clrbits |= nset->bits;
452				setbits &= ~nset->bits;
453				Xbits &= ~nset->bits;
454			} else if (op == '+') {
455				setbits |= nset->bits;
456				clrbits &= ~nset->bits;
457				Xbits &= ~nset->bits;
458			} else if (op == 'X')
459				Xbits |= nset->bits & ~setbits;
460			else
461				break;
462		}
463		if (clrbits) {
464			set->cmd = '-';
465			set->cmd2 = 0;
466			set->bits = clrbits;
467			set++;
468		}
469		if (setbits) {
470			set->cmd = '+';
471			set->cmd2 = 0;
472			set->bits = setbits;
473			set++;
474		}
475		if (Xbits) {
476			set->cmd = 'X';
477			set->cmd2 = 0;
478			set->bits = Xbits;
479			set++;
480		}
481	}
482}
483