xref: /freebsd/lib/libutil/pw_util.c (revision b52b9d56d4e96089873a75f9e29062eec19fabba) 
1 /*-
2  * Copyright (c) 1990, 1993, 1994
3  *	The Regents of the University of California.  All rights reserved.
4  * Copyright (c) 2002 Networks Associates Technology, Inc.
5  * All rights reserved.
6  *
7  * Portions of this software were developed for the FreeBSD Project by
8  * ThinkSec AS and NAI Labs, the Security Research Division of Network
9  * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
10  * ("CBOSS"), as part of the DARPA CHATS research program.
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright
18  *    notice, this list of conditions and the following disclaimer in the
19  *    documentation and/or other materials provided with the distribution.
20  * 3. All advertising materials mentioning features or use of this software
21  *    must display the following acknowledgement:
22  *	This product includes software developed by the University of
23  *	California, Berkeley and its contributors.
24  * 4. Neither the name of the University nor the names of its contributors
25  *    may be used to endorse or promote products derived from this software
26  *    without specific prior written permission.
27  *
28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38  * SUCH DAMAGE.
39  */
40 
41 #ifndef lint
42 #if 0
43 static const char sccsid[] = "@(#)pw_util.c	8.3 (Berkeley) 4/2/94";
44 #endif
45 static const char rcsid[] =
46   "$FreeBSD$";
47 #endif /* not lint */
48 
49 /*
50  * This file is used by all the "password" programs; vipw(8), chpass(1),
51  * and passwd(1).
52  */
53 
54 #include <sys/param.h>
55 #include <sys/errno.h>
56 #include <sys/time.h>
57 #include <sys/resource.h>
58 #include <sys/stat.h>
59 #include <sys/wait.h>
60 
61 #include <err.h>
62 #include <ctype.h>
63 #include <fcntl.h>
64 #include <inttypes.h>
65 #include <libgen.h>
66 #include <paths.h>
67 #include <pwd.h>
68 #include <signal.h>
69 #include <stdio.h>
70 #include <stdlib.h>
71 #include <string.h>
72 #include <unistd.h>
73 
74 #include <libutil.h>
75 
76 static pid_t editpid = -1;
77 static int lockfd = -1;
78 static char masterpasswd[PATH_MAX];
79 static char passwd_dir[PATH_MAX];
80 static char tempname[PATH_MAX];
81 static int initialized;
82 
83 void
84 pw_cont(int sig)
85 {
86 
87 	if (editpid != -1)
88 		kill(editpid, sig);
89 }
90 
91 /*
92  * Initialize statics and set limits, signals & umask to try to avoid
93  * interruptions, crashes etc. that might expose passord data.
94  */
95 int
96 pw_init(const char *dir, const char *master)
97 {
98 #if 0
99 	struct rlimit rlim;
100 #endif
101 
102 	if (dir == NULL) {
103 		strcpy(passwd_dir, _PATH_ETC);
104 	} else {
105 		if (strlen(dir) >= sizeof passwd_dir) {
106 			errno = ENAMETOOLONG;
107 			return (-1);
108 		}
109 		strcpy(passwd_dir, dir);
110 	}
111 
112 	if (master == NULL) {
113 		if (dir == NULL) {
114 			strcpy(masterpasswd, _PATH_MASTERPASSWD);
115 		} else if (snprintf(masterpasswd, sizeof masterpasswd, "%s/%s",
116 		    passwd_dir, _MASTERPASSWD) > sizeof masterpasswd) {
117 			errno = ENAMETOOLONG;
118 			return (-1);
119 		}
120 	} else {
121 		if (strlen(master) >= sizeof masterpasswd) {
122 			errno = ENAMETOOLONG;
123 			return (-1);
124 		}
125 		strcpy(masterpasswd, master);
126 	}
127 
128 	/*
129 	 * The code that follows is extremely disruptive to the calling
130 	 * process, and is therefore disabled until someone can conceive
131 	 * of a realistic scenario where it would fend off a compromise.
132 	 * Race conditions concerning the temporary files can be guarded
133 	 * against in other ways than masking signals (by checking stat(2)
134 	 * results after creation).
135 	 */
136 #if 0
137 	/* Unlimited resource limits. */
138 	rlim.rlim_cur = rlim.rlim_max = RLIM_INFINITY;
139 	(void)setrlimit(RLIMIT_CPU, &rlim);
140 	(void)setrlimit(RLIMIT_FSIZE, &rlim);
141 	(void)setrlimit(RLIMIT_STACK, &rlim);
142 	(void)setrlimit(RLIMIT_DATA, &rlim);
143 	(void)setrlimit(RLIMIT_RSS, &rlim);
144 
145 	/* Don't drop core (not really necessary, but GP's). */
146 	rlim.rlim_cur = rlim.rlim_max = 0;
147 	(void)setrlimit(RLIMIT_CORE, &rlim);
148 
149 	/* Turn off signals. */
150 	(void)signal(SIGALRM, SIG_IGN);
151 	(void)signal(SIGHUP, SIG_IGN);
152 	(void)signal(SIGINT, SIG_IGN);
153 	(void)signal(SIGPIPE, SIG_IGN);
154 	(void)signal(SIGQUIT, SIG_IGN);
155 	(void)signal(SIGTERM, SIG_IGN);
156 	(void)signal(SIGCONT, pw_cont);
157 
158 	/* Create with exact permissions. */
159 	(void)umask(0);
160 #endif
161 	initialized = 1;
162 	return (0);
163 }
164 
165 /*
166  * Lock the master password file.
167  */
168 int
169 pw_lock(void)
170 {
171 
172 	if (*masterpasswd == '\0')
173 		return (-1);
174 
175 	/*
176 	 * If the master password file doesn't exist, the system is hosed.
177 	 * Might as well try to build one.  Set the close-on-exec bit so
178 	 * that users can't get at the encrypted passwords while editing.
179 	 * Open should allow flock'ing the file; see 4.4BSD.	XXX
180 	 */
181 	for (;;) {
182 		struct stat st;
183 
184 		lockfd = open(masterpasswd, O_RDONLY, 0);
185 		if (lockfd < 0 || fcntl(lockfd, F_SETFD, 1) == -1)
186 			err(1, "%s", masterpasswd);
187 		/* XXX vulnerable to race conditions */
188 		if (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
189 			if (errno == EWOULDBLOCK) {
190 				errx(1, "the password db file is busy");
191 			} else {
192 				err(1, "could not lock the passwd file: ");
193 			}
194 		}
195 
196 		/*
197 		 * If the password file was replaced while we were trying to
198 		 * get the lock, our hardlink count will be 0 and we have to
199 		 * close and retry.
200 		 */
201 		if (fstat(lockfd, &st) == -1)
202 			err(1, "fstat() failed: ");
203 		if (st.st_nlink != 0)
204 			break;
205 		close(lockfd);
206 		lockfd = -1;
207 	}
208 	return (lockfd);
209 }
210 
211 /*
212  * Create and open a presumably safe temp file for editing the password
213  * data, and copy the master password file into it.
214  */
215 int
216 pw_tmp(int mfd)
217 {
218 	char buf[8192];
219 	ssize_t nr, nw;
220 	const char *p;
221 	int tfd;
222 
223 	if (*masterpasswd == '\0')
224 		return (-1);
225 	if ((p = strrchr(masterpasswd, '/')))
226 		++p;
227 	else
228 		p = masterpasswd;
229 	if (snprintf(tempname, sizeof tempname, "%.*spw.XXXXXX",
230 		(int)(p - masterpasswd), masterpasswd) >= sizeof tempname) {
231 		errno = ENAMETOOLONG;
232 		return (-1);
233 	}
234 	if ((tfd = mkstemp(tempname)) == -1)
235 		return (-1);
236 	if (mfd != -1) {
237 		while ((nr = read(mfd, buf, sizeof buf)) > 0)
238 			if ((nw = write(tfd, buf, nr)) != nr)
239 				break;
240 		if (nr != 0) {
241 			unlink(tempname);
242 			*tempname = '\0';
243 			close(tfd);
244 			return (-1);
245 		}
246 	}
247 	return (tfd);
248 }
249 
250 /*
251  * Regenerate the password database.
252  */
253 int
254 pw_mkdb(const char *user)
255 {
256 	int pstat;
257 	pid_t pid;
258 
259 	(void)fflush(stderr);
260 	switch ((pid = fork())) {
261 	case -1:
262 		return (-1);
263 	case 0:
264 		/* child */
265 		if (user == NULL)
266 			execl(_PATH_PWD_MKDB, "pwd_mkdb", "-p",
267 			    "-d", passwd_dir, tempname, NULL);
268 		else
269 			execl(_PATH_PWD_MKDB, "pwd_mkdb", "-p",
270 			    "-d", passwd_dir, "-u", user, tempname, NULL);
271 		_exit(1);
272 	default:
273 		/* parent */
274 		break;
275 	}
276 	if (waitpid(pid, &pstat, 0) == -1)
277 		return (-1);
278 	if (WIFEXITED(pstat) && WEXITSTATUS(pstat) == 0)
279 		return (0);
280 	errno = 0;
281 	return (-1);
282 }
283 
284 /*
285  * Edit the temp file.  Return -1 on error, >0 if the file was modified, 0
286  * if it was not.
287  */
288 int
289 pw_edit(int notsetuid)
290 {
291 	struct stat st1, st2;
292 	const char *editor;
293 	int pstat;
294 
295 	if ((editor = getenv("EDITOR")) == NULL)
296 		editor = _PATH_VI;
297 	if (stat(tempname, &st1) == -1)
298 		return (-1);
299 	switch ((editpid = fork())) {
300 	case -1:
301 		return (-1);
302 	case 0:
303 		/* child */
304 		if (notsetuid) {
305 			(void)setgid(getgid());
306 			(void)setuid(getuid());
307 		}
308 		errno = 0;
309 		execlp(editor, basename(editor), tempname, NULL);
310 		_exit(errno);
311 	default:
312 		/* parent */
313 		break;
314 	}
315 	for (;;) {
316 		editpid = waitpid(editpid, &pstat, WUNTRACED);
317 		if (editpid == -1) {
318 			unlink(tempname);
319 			return (-1);
320 		} else if (WIFSTOPPED(pstat)) {
321 			raise(WSTOPSIG(pstat));
322 		} else if (WIFEXITED(pstat) && WEXITSTATUS(pstat) == 0) {
323 			editpid = -1;
324 			break;
325 		} else {
326 			unlink(tempname);
327 			*tempname = '\0';
328 			editpid = -1;
329 			return (-1);
330 		}
331 	}
332 	if (stat(tempname, &st2) == -1)
333 		return (-1);
334 	return (st1.st_mtime != st2.st_mtime);
335 }
336 
337 /*
338  * Clean up.  Preserve errno for the caller's convenience.
339  */
340 void
341 pw_fini(void)
342 {
343 	int serrno, status;
344 
345 	if (!initialized)
346 		return;
347 	initialized = 0;
348 	serrno = errno;
349 	if (editpid != -1) {
350 		kill(editpid, SIGTERM);
351 		kill(editpid, SIGCONT);
352 		waitpid(editpid, &status, 0);
353 		editpid = -1;
354 	}
355 	if (*tempname != '\0') {
356 		unlink(tempname);
357 		*tempname = '\0';
358 	}
359 	if (lockfd != -1)
360 		close(lockfd);
361 	errno = serrno;
362 }
363 
364 /*
365  * Compares two struct pwds.
366  */
367 int
368 pw_equal(struct passwd *pw1, struct passwd *pw2)
369 {
370 	return (strcmp(pw1->pw_name, pw2->pw_name) == 0 &&
371 	    pw1->pw_uid == pw2->pw_uid &&
372 	    pw1->pw_gid == pw2->pw_gid &&
373 	    strcmp(pw1->pw_class, pw2->pw_class) == 0 &&
374 	    pw1->pw_change == pw2->pw_change &&
375 	    pw1->pw_expire == pw2->pw_expire &&
376 	    strcmp(pw1->pw_gecos, pw2->pw_gecos) == 0 &&
377 	    strcmp(pw1->pw_dir, pw2->pw_dir) == 0 &&
378 	    strcmp(pw1->pw_shell, pw2->pw_shell) == 0);
379 }
380 
381 /*
382  * Make a passwd line out of a struct passwd.
383  */
384 char *
385 pw_make(struct passwd *pw)
386 {
387 	char *line;
388 
389 	asprintf(&line, "%s:%s:%ju:%ju:%s:%ju:%ju:%s:%s:%s", pw->pw_name,
390 	    pw->pw_passwd, (uintmax_t)pw->pw_uid, (uintmax_t)pw->pw_gid,
391 	    pw->pw_class, (uintmax_t)pw->pw_change, (uintmax_t)pw->pw_expire,
392 	    pw->pw_gecos, pw->pw_dir, pw->pw_shell);
393 	return line;
394 }
395 
396 /*
397  * Copy password file from one descriptor to another, replacing or adding
398  * a single record on the way.
399  */
400 int
401 pw_copy(int ffd, int tfd, struct passwd *pw, struct passwd *old_pw)
402 {
403 	char buf[8192], *end, *line, *p, *q, *r, t;
404 	struct passwd *fpw;
405 	ssize_t len;
406 	int eof;
407 
408 	if ((line = pw_make(pw)) == NULL)
409 		return (-1);
410 
411 	eof = 0;
412 	len = 0;
413 	p = q = end = buf;
414 	for (;;) {
415 		/* find the end of the current line */
416 		for (p = q; q < end && *q != '\0'; ++q)
417 			if (*q == '\n')
418 				break;
419 
420 		/* if we don't have a complete line, fill up the buffer */
421 		if (q >= end) {
422 			if (eof)
423 				break;
424 			if (q - p >= sizeof buf) {
425 				warnx("passwd line too long");
426 				errno = EINVAL; /* hack */
427 				goto err;
428 			}
429 			if (p < end) {
430 				q = memmove(buf, p, end - p);
431 				end -= p - buf;
432 			} else {
433 				p = q = end = buf;
434 			}
435 			len = read(ffd, end, sizeof buf - (end - buf));
436 			if (len == -1)
437 				goto err;
438 			if (len == 0 && p == buf)
439 				break;
440 			end += len;
441 			len = end - buf;
442 			if (len < sizeof buf) {
443 				eof = 1;
444 				if (len > 0 && buf[len - 1] != '\n')
445 					++len, *end++ = '\n';
446 			}
447 			continue;
448 		}
449 
450 		/* is it a blank line or a comment? */
451 		for (r = p; r < q && isspace(*r); ++r)
452 			/* nothing */ ;
453 		if (r == q || *r == '#') {
454 			/* yep */
455 			if (write(tfd, p, q - p + 1) != q - p + 1)
456 				goto err;
457 			++q;
458 			continue;
459 		}
460 
461 		/* is it the one we're looking for? */
462 		t = *q;
463 		*q = '\0';
464 		fpw = pw_scan(r, PWSCAN_MASTER);
465 		*q = t;
466 		if ((old_pw && !pw_equal(fpw, old_pw)) ||
467 		    (!old_pw && strcmp(fpw->pw_name, pw->pw_name))) {
468 			/* nope */
469 			free(fpw);
470 			if (write(tfd, p, q - p + 1) != q - p + 1)
471 				goto err;
472 			++q;
473 			continue;
474 		}
475 		free(fpw);
476 
477 		/* it is, replace it */
478 		len = strlen(line);
479 		if (write(tfd, line, len) != len)
480 			goto err;
481 
482 		/* we're done, just copy the rest over */
483 		for (;;) {
484 			if (write(tfd, q, end - q) != end - q)
485 				goto err;
486 			q = buf;
487 			len = read(ffd, buf, sizeof buf);
488 			if (len == 0)
489 				break;
490 			if (len == -1)
491 				goto err;
492 			end = buf + len;
493 		}
494 		goto done;
495 	}
496 
497 	/* if we got here, we have a new entry */
498 	len = strlen(line);
499 	if (write(tfd, line, len) != len)
500 		goto err;
501  done:
502 	free(line);
503 	return (0);
504  err:
505 	free(line);
506 	return (-1);
507 }
508 
509 /*
510  * Return the current value of tempname.
511  */
512 const char *
513 pw_tempname(void)
514 {
515 
516 	return (tempname);
517 }
518 
519 /*
520  * Duplicate a struct passwd.
521  */
522 struct passwd *
523 pw_dup(struct passwd *pw)
524 {
525 	struct passwd *npw;
526 	size_t len;
527 
528 	len = sizeof *npw +
529 	    (pw->pw_name ? strlen(pw->pw_name) + 1 : 0) +
530 	    (pw->pw_passwd ? strlen(pw->pw_passwd) + 1 : 0) +
531 	    (pw->pw_class ? strlen(pw->pw_class) + 1 : 0) +
532 	    (pw->pw_gecos ? strlen(pw->pw_gecos) + 1 : 0) +
533 	    (pw->pw_dir ? strlen(pw->pw_dir) + 1 : 0) +
534 	    (pw->pw_shell ? strlen(pw->pw_shell) + 1 : 0);
535 	if ((npw = malloc(len)) == NULL)
536 		return (NULL);
537 	memcpy(npw, pw, sizeof *npw);
538 	len = sizeof *npw;
539 	if (pw->pw_name) {
540 		npw->pw_name = ((char *)npw) + len;
541 		len += sprintf(npw->pw_name, "%s", pw->pw_name) + 1;
542 	}
543 	if (pw->pw_passwd) {
544 		npw->pw_passwd = ((char *)npw) + len;
545 		len += sprintf(npw->pw_passwd, "%s", pw->pw_passwd) + 1;
546 	}
547 	if (pw->pw_class) {
548 		npw->pw_class = ((char *)npw) + len;
549 		len += sprintf(npw->pw_class, "%s", pw->pw_class) + 1;
550 	}
551 	if (pw->pw_gecos) {
552 		npw->pw_gecos = ((char *)npw) + len;
553 		len += sprintf(npw->pw_gecos, "%s", pw->pw_gecos) + 1;
554 	}
555 	if (pw->pw_dir) {
556 		npw->pw_dir = ((char *)npw) + len;
557 		len += sprintf(npw->pw_dir, "%s", pw->pw_dir) + 1;
558 	}
559 	if (pw->pw_shell) {
560 		npw->pw_shell = ((char *)npw) + len;
561 		len += sprintf(npw->pw_shell, "%s", pw->pw_shell) + 1;
562 	}
563 	return (npw);
564 }
565 
566 #include "pw_scan.h"
567 
568 /*
569  * Wrapper around an internal libc function
570  */
571 struct passwd *
572 pw_scan(const char *line, int flags)
573 {
574 	struct passwd pw, *ret;
575 	char *bp;
576 
577 	if ((bp = strdup(line)) == NULL)
578 		return (NULL);
579 	if (!__pw_scan(bp, &pw, flags)) {
580 		free(bp);
581 		return (NULL);
582 	}
583 	ret = pw_dup(&pw);
584 	free(bp);
585 	return (ret);
586 }
587