xref: /freebsd/lib/libutil/gr_util.c (revision d1d015864103b253b3fcb2f72a0da5b0cfeb31b6)
1 /*-
2  * Copyright (c) 2008 Sean C. Farley <scf@FreeBSD.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer,
10  *    without modification, immediately at the beginning of the file.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/errno.h>
32 #include <sys/stat.h>
33 
34 #include <ctype.h>
35 #include <err.h>
36 #include <fcntl.h>
37 #include <grp.h>
38 #include <inttypes.h>
39 #include <libutil.h>
40 #include <paths.h>
41 #include <stdbool.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include <string.h>
45 #include <unistd.h>
46 
47 static int lockfd = -1;
48 static char group_dir[PATH_MAX];
49 static char group_file[PATH_MAX];
50 static char tempname[PATH_MAX];
51 static int initialized;
52 static size_t grmemlen(const struct group *, const char *, int *);
53 static struct group *grcopy(const struct group *gr, char *mem, const char *, int ndx);
54 
55 /*
56  * Initialize statics
57  */
58 int
59 gr_init(const char *dir, const char *group)
60 {
61 
62 	if (dir == NULL) {
63 		strcpy(group_dir, _PATH_ETC);
64 	} else {
65 		if (strlen(dir) >= sizeof(group_dir)) {
66 			errno = ENAMETOOLONG;
67 			return (-1);
68 		}
69 		strcpy(group_dir, dir);
70 	}
71 
72 	if (group == NULL) {
73 		if (dir == NULL) {
74 			strcpy(group_file, _PATH_GROUP);
75 		} else if (snprintf(group_file, sizeof(group_file), "%s/group",
76 			group_dir) > (int)sizeof(group_file)) {
77 			errno = ENAMETOOLONG;
78 			return (-1);
79 		}
80 	} else {
81 		if (strlen(group) >= sizeof(group_file)) {
82 			errno = ENAMETOOLONG;
83 			return (-1);
84 		}
85 		strcpy(group_file, group);
86 	}
87 
88 	initialized = 1;
89 	return (0);
90 }
91 
92 /*
93  * Lock the group file
94  */
95 int
96 gr_lock(void)
97 {
98 	if (*group_file == '\0')
99 		return (-1);
100 
101 	for (;;) {
102 		struct stat st;
103 
104 		lockfd = flopen(group_file, O_RDONLY|O_NONBLOCK|O_CLOEXEC, 0);
105 		if (lockfd == -1) {
106 			if (errno == EWOULDBLOCK) {
107 				errx(1, "the group file is busy");
108 			} else {
109 				err(1, "could not lock the group file: ");
110 			}
111 		}
112 		if (fstat(lockfd, &st) == -1)
113 			err(1, "fstat() failed: ");
114 		if (st.st_nlink != 0)
115 			break;
116 		close(lockfd);
117 		lockfd = -1;
118 	}
119 	return (lockfd);
120 }
121 
122 /*
123  * Create and open a presmuably safe temp file for editing group data
124  */
125 int
126 gr_tmp(int mfd)
127 {
128 	char buf[8192];
129 	ssize_t nr;
130 	const char *p;
131 	int tfd;
132 
133 	if (*group_file == '\0')
134 		return (-1);
135 	if ((p = strrchr(group_file, '/')))
136 		++p;
137 	else
138 		p = group_file;
139 	if (snprintf(tempname, sizeof(tempname), "%.*sgroup.XXXXXX",
140 		(int)(p - group_file), group_file) >= (int)sizeof(tempname)) {
141 		errno = ENAMETOOLONG;
142 		return (-1);
143 	}
144 	if ((tfd = mkstemp(tempname)) == -1)
145 		return (-1);
146 	if (mfd != -1) {
147 		while ((nr = read(mfd, buf, sizeof(buf))) > 0)
148 			if (write(tfd, buf, (size_t)nr) != nr)
149 				break;
150 		if (nr != 0) {
151 			unlink(tempname);
152 			*tempname = '\0';
153 			close(tfd);
154 			return (-1);
155 		}
156 	}
157 	return (tfd);
158 }
159 
160 /*
161  * Copy the group file from one descriptor to another, replacing, deleting
162  * or adding a single record on the way.
163  */
164 int
165 gr_copy(int ffd, int tfd, const struct group *gr, struct group *old_gr)
166 {
167 	char buf[8192], *end, *line, *p, *q, *r, t;
168 	struct group *fgr;
169 	const struct group *sgr;
170 	size_t len;
171 	int eof, readlen;
172 
173 	sgr = gr;
174 	if (gr == NULL) {
175 		line = NULL;
176 		if (old_gr == NULL)
177 			return (-1);
178 		sgr = old_gr;
179 	} else if ((line = gr_make(gr)) == NULL)
180 		return (-1);
181 
182 	eof = 0;
183 	len = 0;
184 	p = q = end = buf;
185 	for (;;) {
186 		/* find the end of the current line */
187 		for (p = q; q < end && *q != '\0'; ++q)
188 			if (*q == '\n')
189 				break;
190 
191 		/* if we don't have a complete line, fill up the buffer */
192 		if (q >= end) {
193 			if (eof)
194 				break;
195 			if ((size_t)(q - p) >= sizeof(buf)) {
196 				warnx("group line too long");
197 				errno = EINVAL; /* hack */
198 				goto err;
199 			}
200 			if (p < end) {
201 				q = memmove(buf, p, end -p);
202 				end -= p - buf;
203 			} else {
204 				p = q = end = buf;
205 			}
206 			readlen = read(ffd, end, sizeof(buf) - (end -buf));
207 			if (readlen == -1)
208 				goto err;
209 			else
210 				len = (size_t)readlen;
211 			if (len == 0 && p == buf)
212 				break;
213 			end += len;
214 			len = end - buf;
215 			if (len < (ssize_t)sizeof(buf)) {
216 				eof = 1;
217 				if (len > 0 && buf[len -1] != '\n')
218 					++len, *end++ = '\n';
219 			}
220 			continue;
221 		}
222 
223 		/* is it a blank line or a comment? */
224 		for (r = p; r < q && isspace(*r); ++r)
225 			/* nothing */;
226 		if (r == q || *r == '#') {
227 			/* yep */
228 			if (write(tfd, p, q -p + 1) != q - p + 1)
229 				goto err;
230 			++q;
231 			continue;
232 		}
233 
234 		/* is it the one we're looking for? */
235 
236 		t = *q;
237 		*q = '\0';
238 
239 		fgr = gr_scan(r);
240 
241 		/* fgr is either a struct group for the current line,
242 		 * or NULL if the line is malformed.
243 		 */
244 
245 		*q = t;
246 		if (fgr == NULL || fgr->gr_gid != sgr->gr_gid) {
247 			/* nope */
248 			if (fgr != NULL)
249 				free(fgr);
250 			if (write(tfd, p, q - p + 1) != q - p + 1)
251 				goto err;
252 			++q;
253 			continue;
254 		}
255 		if (old_gr && !gr_equal(fgr, old_gr)) {
256 			warnx("entry inconsistent");
257 			free(fgr);
258 			errno = EINVAL; /* hack */
259 			goto err;
260 		}
261 		free(fgr);
262 
263 		/* it is, replace or remove it */
264 		if (line != NULL) {
265 			len = strlen(line);
266 			if (write(tfd, line, len) != (int) len)
267 				goto err;
268 		} else {
269 			/* when removed, avoid the \n */
270 			q++;
271 		}
272 		/* we're done, just copy the rest over */
273 		for (;;) {
274 			if (write(tfd, q, end - q) != end - q)
275 				goto err;
276 			q = buf;
277 			readlen = read(ffd, buf, sizeof(buf));
278 			if (readlen == 0)
279 				break;
280 			else
281 				len = (size_t)readlen;
282 			if (readlen == -1)
283 				goto err;
284 			end = buf + len;
285 		}
286 		goto done;
287 	}
288 
289 	/* if we got here, we didn't find the old entry */
290 	if (line == NULL) {
291 		errno = ENOENT;
292 		goto err;
293 	}
294 	len = strlen(line);
295 	if ((size_t)write(tfd, line, len) != len ||
296 	   write(tfd, "\n", 1) != 1)
297 		goto err;
298  done:
299 	if (line != NULL)
300 		free(line);
301 	return (0);
302  err:
303 	if (line != NULL)
304 		free(line);
305 	return (-1);
306 }
307 
308 /*
309  * Regenerate the group file
310  */
311 int
312 gr_mkdb(void)
313 {
314 	if (chmod(tempname, 0644) != 0)
315 		return (-1);
316 
317 	return (rename(tempname, group_file));
318 }
319 
320 /*
321  * Clean up. Preserves errno for the caller's convenience.
322  */
323 void
324 gr_fini(void)
325 {
326 	int serrno;
327 
328 	if (!initialized)
329 		return;
330 	initialized = 0;
331 	serrno = errno;
332 	if (*tempname != '\0') {
333 		unlink(tempname);
334 		*tempname = '\0';
335 	}
336 	if (lockfd != -1)
337 		close(lockfd);
338 	errno = serrno;
339 }
340 
341 /*
342  * Compares two struct group's.
343  */
344 int
345 gr_equal(const struct group *gr1, const struct group *gr2)
346 {
347 	int gr1_ndx;
348 	int gr2_ndx;
349 
350 	/* Check that the non-member information is the same. */
351 	if (gr1->gr_name == NULL || gr2->gr_name == NULL) {
352 		if (gr1->gr_name != gr2->gr_name)
353 			return (false);
354 	} else if (strcmp(gr1->gr_name, gr2->gr_name) != 0)
355 		return (false);
356 	if (gr1->gr_passwd == NULL || gr2->gr_passwd == NULL) {
357 		if (gr1->gr_passwd != gr2->gr_passwd)
358 			return (false);
359 	} else if (strcmp(gr1->gr_passwd, gr2->gr_passwd) != 0)
360 		return (false);
361 	if (gr1->gr_gid != gr2->gr_gid)
362 		return (false);
363 
364 	/* Check all members in both groups.
365 	 * getgrnam can return gr_mem with a pointer to NULL.
366 	 * gr_dup and gr_add strip out this superfluous NULL, setting
367 	 * gr_mem to NULL for no members.
368 	*/
369 	if (gr1->gr_mem != NULL && gr2->gr_mem != NULL) {
370 		int i;
371 
372 		for (i = 0; gr1->gr_mem[i] != NULL; i++) {
373 			if (strcmp(gr1->gr_mem[i], gr2->gr_mem[i]) != 0)
374 				return (false);
375 		}
376 	}
377 	/* Count number of members in both structs */
378 	gr2_ndx = 0;
379 	if (gr2->gr_mem != NULL)
380 		for(; gr2->gr_mem[gr2_ndx] != NULL; gr2_ndx++)
381 			/* empty */;
382 	gr1_ndx = 0;
383 	if (gr1->gr_mem != NULL)
384 		for(; gr1->gr_mem[gr1_ndx] != NULL; gr1_ndx++)
385 			/* empty */;
386 	if (gr1_ndx != gr2_ndx)
387 		return (false);
388 
389 	return (true);
390 }
391 
392 /*
393  * Make a group line out of a struct group.
394  */
395 char *
396 gr_make(const struct group *gr)
397 {
398 	const char *group_line_format = "%s:%s:%ju:";
399 	const char *sep;
400 	char *line;
401 	char *p;
402 	size_t line_size;
403 	int ndx;
404 
405 	/* Calculate the length of the group line. */
406 	line_size = snprintf(NULL, 0, group_line_format, gr->gr_name,
407 	    gr->gr_passwd, (uintmax_t)gr->gr_gid) + 1;
408 	if (gr->gr_mem != NULL) {
409 		for (ndx = 0; gr->gr_mem[ndx] != NULL; ndx++)
410 			line_size += strlen(gr->gr_mem[ndx]) + 1;
411 		if (ndx > 0)
412 			line_size--;
413 	}
414 
415 	/* Create the group line and fill it. */
416 	if ((line = p = malloc(line_size)) == NULL)
417 		return (NULL);
418 	p += sprintf(p, group_line_format, gr->gr_name, gr->gr_passwd,
419 	    (uintmax_t)gr->gr_gid);
420 	if (gr->gr_mem != NULL) {
421 		sep = "";
422 		for (ndx = 0; gr->gr_mem[ndx] != NULL; ndx++) {
423 			p = stpcpy(p, sep);
424 			p = stpcpy(p, gr->gr_mem[ndx]);
425 			sep = ",";
426 		}
427 	}
428 
429 	return (line);
430 }
431 
432 /*
433  * Duplicate a struct group.
434  */
435 struct group *
436 gr_dup(const struct group *gr)
437 {
438 	return (gr_add(gr, NULL));
439 }
440 /*
441  * Add a new member name to a struct group.
442  */
443 struct group *
444 gr_add(const struct group *gr, const char *newmember)
445 {
446 	char *mem;
447 	size_t len;
448 	int num_mem;
449 
450 	num_mem = 0;
451 	len = grmemlen(gr, newmember, &num_mem);
452 	/* Create new group and copy old group into it. */
453 	if ((mem = malloc(len)) == NULL)
454 		return (NULL);
455 	return (grcopy(gr, mem, newmember, num_mem));
456 }
457 
458 /* It is safer to walk the pointers given at gr_mem since there is no
459  * guarantee the gr_mem + strings are contiguous in the given struct group
460  * but compactify the new group into the following form.
461  *
462  * The new struct is laid out like this in memory. The example given is
463  * for a group with two members only.
464  *
465  * {
466  * (char *name)
467  * (char *passwd)
468  * (int gid)
469  * (gr_mem * newgrp + sizeof(struct group) + sizeof(**)) points to gr_mem area
470  * gr_mem area
471  * (member1 *)
472  * (member2 *)
473  * (NULL)
474  * (name string)
475  * (passwd string)
476  * (member1 string)
477  * (member2 string)
478  * }
479  */
480 /*
481  * Copy the contents of a group plus given name to a preallocated group struct
482  */
483 static struct group *
484 grcopy(const struct group *gr, char *dst, const char *name, int ndx)
485 {
486 	int i;
487 	struct group *newgr;
488 
489 	newgr = (struct group *)(void *)dst;	/* avoid alignment warning */
490 	dst += sizeof(*newgr);
491 	if (ndx != 0) {
492 		newgr->gr_mem = (char **)(void *)(dst);	/* avoid alignment warning */
493 		dst += (ndx + 1) * sizeof(*newgr->gr_mem);
494 	} else
495 		newgr->gr_mem = NULL;
496 	if (gr->gr_name != NULL) {
497 		newgr->gr_name = dst;
498 		dst = stpcpy(dst, gr->gr_name) + 1;
499 	} else
500 		newgr->gr_name = NULL;
501 	if (gr->gr_passwd != NULL) {
502 		newgr->gr_passwd = dst;
503 		dst = stpcpy(dst, gr->gr_passwd) + 1;
504 	} else
505 		newgr->gr_passwd = NULL;
506 	newgr->gr_gid = gr->gr_gid;
507 	i = 0;
508 	/* Original group struct might have a NULL gr_mem */
509 	if (gr->gr_mem != NULL) {
510 		for (; gr->gr_mem[i] != NULL; i++) {
511 			newgr->gr_mem[i] = dst;
512 			dst = stpcpy(dst, gr->gr_mem[i]) + 1;
513 		}
514 	}
515 	/* If name is not NULL, newgr->gr_mem is known to be not NULL */
516 	if (name != NULL) {
517 		newgr->gr_mem[i++] = dst;
518 		dst = stpcpy(dst, name) + 1;
519 	}
520 	/* if newgr->gr_mem is not NULL add NULL marker */
521 	if (newgr->gr_mem != NULL)
522 		newgr->gr_mem[i] = NULL;
523 
524 	return (newgr);
525 }
526 
527 /*
528  *  Calculate length of a struct group + given name
529  */
530 static size_t
531 grmemlen(const struct group *gr, const char *name, int *num_mem)
532 {
533 	size_t len;
534 	int i;
535 
536 	if (gr == NULL)
537 		return (0);
538 	/* Calculate size of the group. */
539 	len = sizeof(*gr);
540 	if (gr->gr_name != NULL)
541 		len += strlen(gr->gr_name) + 1;
542 	if (gr->gr_passwd != NULL)
543 		len += strlen(gr->gr_passwd) + 1;
544 	i = 0;
545 	if (gr->gr_mem != NULL) {
546 		for (; gr->gr_mem[i] != NULL; i++) {
547 			len += strlen(gr->gr_mem[i]) + 1;
548 			len += sizeof(*gr->gr_mem);
549 		}
550 	}
551 	if (name != NULL) {
552 		i++;
553 		len += strlen(name) + 1;
554 		len += sizeof(*gr->gr_mem);
555 	}
556 	/* Allow for NULL pointer */
557 	if (i != 0)
558 		len += sizeof(*gr->gr_mem);
559 	*num_mem = i;
560 	return(len);
561 }
562 
563 /*
564  * Scan a line and place it into a group structure.
565  */
566 static bool
567 __gr_scan(char *line, struct group *gr)
568 {
569 	char *loc;
570 	int ndx;
571 
572 	/* Assign non-member information to structure. */
573 	gr->gr_name = line;
574 	if ((loc = strchr(line, ':')) == NULL)
575 		return (false);
576 	*loc = '\0';
577 	gr->gr_passwd = loc + 1;
578 	if (*gr->gr_passwd == ':')
579 		*gr->gr_passwd = '\0';
580 	else {
581 		if ((loc = strchr(loc + 1, ':')) == NULL)
582 			return (false);
583 		*loc = '\0';
584 	}
585 	if (sscanf(loc + 1, "%u", &gr->gr_gid) != 1)
586 		return (false);
587 
588 	/* Assign member information to structure. */
589 	if ((loc = strchr(loc + 1, ':')) == NULL)
590 		return (false);
591 	line = loc + 1;
592 	gr->gr_mem = NULL;
593 	ndx = 0;
594 	do {
595 		gr->gr_mem = reallocf(gr->gr_mem, sizeof(*gr->gr_mem) *
596 		    (ndx + 1));
597 		if (gr->gr_mem == NULL)
598 			return (false);
599 
600 		/* Skip locations without members (i.e., empty string). */
601 		do {
602 			gr->gr_mem[ndx] = strsep(&line, ",");
603 		} while (gr->gr_mem[ndx] != NULL && *gr->gr_mem[ndx] == '\0');
604 	} while (gr->gr_mem[ndx++] != NULL);
605 
606 	return (true);
607 }
608 
609 /*
610  * Create a struct group from a line.
611  */
612 struct group *
613 gr_scan(const char *line)
614 {
615 	struct group gr;
616 	char *line_copy;
617 	struct group *new_gr;
618 
619 	if ((line_copy = strdup(line)) == NULL)
620 		return (NULL);
621 	if (!__gr_scan(line_copy, &gr)) {
622 		free(line_copy);
623 		return (NULL);
624 	}
625 	new_gr = gr_dup(&gr);
626 	free(line_copy);
627 	if (gr.gr_mem != NULL)
628 		free(gr.gr_mem);
629 
630 	return (new_gr);
631 }
632