xref: /freebsd/lib/libutil/pw_util.c (revision 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c)
1 /*--
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1990, 1993, 1994
5  *	The Regents of the University of California.  All rights reserved.
6  * Copyright (c) 2002 Networks Associates Technology, Inc.
7  * All rights reserved.
8  *
9  * Portions of this software were developed for the FreeBSD Project by
10  * ThinkSec AS and NAI Labs, the Security Research Division of Network
11  * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
12  * ("CBOSS"), as part of the DARPA CHATS research program.
13  *
14  * Redistribution and use in source and binary forms, with or without
15  * modification, are permitted provided that the following conditions
16  * are met:
17  * 1. Redistributions of source code must retain the above copyright
18  *    notice, this list of conditions and the following disclaimer.
19  * 2. Redistributions in binary form must reproduce the above copyright
20  *    notice, this list of conditions and the following disclaimer in the
21  *    documentation and/or other materials provided with the distribution.
22  * 3. 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 
40 /*
41  * This file is used by all the "password" programs; vipw(8), chpass(1),
42  * and passwd(1).
43  */
44 
45 #include <sys/param.h>
46 #include <sys/errno.h>
47 #include <sys/time.h>
48 #include <sys/resource.h>
49 #include <sys/stat.h>
50 #include <sys/wait.h>
51 
52 #include <ctype.h>
53 #include <err.h>
54 #include <fcntl.h>
55 #include <inttypes.h>
56 #include <paths.h>
57 #include <pwd.h>
58 #include <signal.h>
59 #include <stdio.h>
60 #include <stdlib.h>
61 #include <string.h>
62 #include <unistd.h>
63 
64 #include "libutil.h"
65 
66 static pid_t editpid = -1;
67 static int lockfd = -1;
68 static char masterpasswd[PATH_MAX];
69 static char passwd_dir[PATH_MAX];
70 static char tempname[PATH_MAX];
71 static int initialized;
72 
73 #if 0
74 void
75 pw_cont(int sig)
76 {
77 
78 	if (editpid != -1)
79 		kill(editpid, sig);
80 }
81 #endif
82 
83 /*
84  * Initialize statics and set limits, signals & umask to try to avoid
85  * interruptions, crashes etc. that might expose passord data.
86  */
87 int
88 pw_init(const char *dir, const char *master)
89 {
90 #if 0
91 	struct rlimit rlim;
92 #endif
93 
94 	if (dir == NULL) {
95 		strcpy(passwd_dir, _PATH_ETC);
96 	} else {
97 		if (strlen(dir) >= sizeof(passwd_dir)) {
98 			errno = ENAMETOOLONG;
99 			return (-1);
100 		}
101 		strcpy(passwd_dir, dir);
102 	}
103 
104 	if (master == NULL) {
105 		if (dir == NULL) {
106 			strcpy(masterpasswd, _PATH_MASTERPASSWD);
107 		} else if (snprintf(masterpasswd, sizeof(masterpasswd), "%s/%s",
108 		    passwd_dir, _MASTERPASSWD) > (int)sizeof(masterpasswd)) {
109 			errno = ENAMETOOLONG;
110 			return (-1);
111 		}
112 	} else {
113 		if (strlen(master) >= sizeof(masterpasswd)) {
114 			errno = ENAMETOOLONG;
115 			return (-1);
116 		}
117 		strcpy(masterpasswd, master);
118 	}
119 
120 	/*
121 	 * The code that follows is extremely disruptive to the calling
122 	 * process, and is therefore disabled until someone can conceive
123 	 * of a realistic scenario where it would fend off a compromise.
124 	 * Race conditions concerning the temporary files can be guarded
125 	 * against in other ways than masking signals (by checking stat(2)
126 	 * results after creation).
127 	 */
128 #if 0
129 	/* Unlimited resource limits. */
130 	rlim.rlim_cur = rlim.rlim_max = RLIM_INFINITY;
131 	(void)setrlimit(RLIMIT_CPU, &rlim);
132 	(void)setrlimit(RLIMIT_FSIZE, &rlim);
133 	(void)setrlimit(RLIMIT_STACK, &rlim);
134 	(void)setrlimit(RLIMIT_DATA, &rlim);
135 	(void)setrlimit(RLIMIT_RSS, &rlim);
136 
137 	/* Don't drop core (not really necessary, but GP's). */
138 	rlim.rlim_cur = rlim.rlim_max = 0;
139 	(void)setrlimit(RLIMIT_CORE, &rlim);
140 
141 	/* Turn off signals. */
142 	(void)signal(SIGALRM, SIG_IGN);
143 	(void)signal(SIGHUP, SIG_IGN);
144 	(void)signal(SIGINT, SIG_IGN);
145 	(void)signal(SIGPIPE, SIG_IGN);
146 	(void)signal(SIGQUIT, SIG_IGN);
147 	(void)signal(SIGTERM, SIG_IGN);
148 	(void)signal(SIGCONT, pw_cont);
149 
150 	/* Create with exact permissions. */
151 	(void)umask(0);
152 #endif
153 	initialized = 1;
154 	return (0);
155 }
156 
157 /*
158  * Lock the master password file.
159  */
160 int
161 pw_lock(void)
162 {
163 
164 	if (*masterpasswd == '\0')
165 		return (-1);
166 
167 	/*
168 	 * If the master password file doesn't exist, the system is hosed.
169 	 * Might as well try to build one.  Set the close-on-exec bit so
170 	 * that users can't get at the encrypted passwords while editing.
171 	 * Open should allow flock'ing the file; see 4.4BSD.	XXX
172 	 */
173 	for (;;) {
174 		struct stat st;
175 
176 		lockfd = flopen(masterpasswd, O_RDONLY|O_NONBLOCK|O_CLOEXEC, 0);
177 		if (lockfd == -1) {
178 			if (errno == EWOULDBLOCK) {
179 				errx(1, "the password db file is busy");
180 			} else {
181 				err(1, "could not lock the passwd file");
182 			}
183 		}
184 
185 		/*
186 		 * If the password file was replaced while we were trying to
187 		 * get the lock, our hardlink count will be 0 and we have to
188 		 * close and retry.
189 		 */
190 		if (fstat(lockfd, &st) == -1)
191 			err(1, "fstat() failed");
192 		if (st.st_nlink != 0)
193 			break;
194 		close(lockfd);
195 		lockfd = -1;
196 	}
197 	return (lockfd);
198 }
199 
200 /*
201  * Create and open a presumably safe temp file for editing the password
202  * data, and copy the master password file into it.
203  */
204 int
205 pw_tmp(int mfd)
206 {
207 	char buf[8192];
208 	ssize_t nr;
209 	const char *p;
210 	int tfd;
211 
212 	if (*masterpasswd == '\0')
213 		return (-1);
214 	if ((p = strrchr(masterpasswd, '/')))
215 		++p;
216 	else
217 		p = masterpasswd;
218 	if (snprintf(tempname, sizeof(tempname), "%.*spw.XXXXXX",
219 		(int)(p - masterpasswd), masterpasswd) >= (int)sizeof(tempname)) {
220 		errno = ENAMETOOLONG;
221 		return (-1);
222 	}
223 	if ((tfd = mkostemp(tempname, 0)) == -1)
224 		return (-1);
225 	if (mfd != -1) {
226 		while ((nr = read(mfd, buf, sizeof(buf))) > 0)
227 			if (write(tfd, buf, (size_t)nr) != nr)
228 				break;
229 		if (nr != 0) {
230 			unlink(tempname);
231 			*tempname = '\0';
232 			close(tfd);
233 			return (-1);
234 		}
235 	}
236 	return (tfd);
237 }
238 
239 /*
240  * Regenerate the password database.
241  */
242 int
243 pw_mkdb(const char *user)
244 {
245 	int pstat;
246 	pid_t pid;
247 
248 	(void)fflush(stderr);
249 	switch ((pid = fork())) {
250 	case -1:
251 		return (-1);
252 	case 0:
253 		/* child */
254 		if (user == NULL)
255 			execl(_PATH_PWD_MKDB, "pwd_mkdb", "-p",
256 			    "-d", passwd_dir, tempname, (char *)NULL);
257 		else
258 			execl(_PATH_PWD_MKDB, "pwd_mkdb", "-p",
259 			    "-d", passwd_dir, "-u", user, tempname,
260 			    (char *)NULL);
261 		_exit(1);
262 		/* NOTREACHED */
263 	default:
264 		/* parent */
265 		break;
266 	}
267 	if (waitpid(pid, &pstat, 0) == -1)
268 		return (-1);
269 	if (WIFEXITED(pstat) && WEXITSTATUS(pstat) == 0)
270 		return (0);
271 	errno = 0;
272 	return (-1);
273 }
274 
275 /*
276  * Edit the temp file.  Return -1 on error, >0 if the file was modified, 0
277  * if it was not.
278  */
279 int
280 pw_edit(int notsetuid)
281 {
282 	struct sigaction sa, sa_int, sa_quit;
283 	sigset_t oldsigset, nsigset;
284 	struct stat st1, st2;
285 	const char *editor;
286 	int pstat;
287 
288 	if ((editor = getenv("EDITOR")) == NULL)
289 		editor = _PATH_VI;
290 	if (stat(tempname, &st1) == -1)
291 		return (-1);
292 	sa.sa_handler = SIG_IGN;
293 	sigemptyset(&sa.sa_mask);
294 	sa.sa_flags = 0;
295 	sigaction(SIGINT, &sa, &sa_int);
296 	sigaction(SIGQUIT, &sa, &sa_quit);
297 	sigemptyset(&nsigset);
298 	sigaddset(&nsigset, SIGCHLD);
299 	sigprocmask(SIG_BLOCK, &nsigset, &oldsigset);
300 	switch ((editpid = fork())) {
301 	case -1:
302 		return (-1);
303 	case 0:
304 		sigaction(SIGINT, &sa_int, NULL);
305 		sigaction(SIGQUIT, &sa_quit, NULL);
306 		sigprocmask(SIG_SETMASK, &oldsigset, NULL);
307 		if (notsetuid) {
308 			if (setgid(getgid()) == -1)
309 				err(1, "setgid");
310 			if (setuid(getuid()) == -1)
311 				err(1, "setuid");
312 		}
313 		execlp(editor, editor, tempname, (char *)NULL);
314 		err(1, "%s", editor);
315 	default:
316 		/* parent */
317 		break;
318 	}
319 	for (;;) {
320 		if (waitpid(editpid, &pstat, WUNTRACED) == -1) {
321 			if (errno == EINTR)
322 				continue;
323 			unlink(tempname);
324 			editpid = -1;
325 			break;
326 		} else if (WIFSTOPPED(pstat)) {
327 			raise(WSTOPSIG(pstat));
328 		} else if (WIFEXITED(pstat)) {
329 			if (WEXITSTATUS(pstat) != 0)
330 				errx(1, "\"%s\" exited with status %d", editor, WEXITSTATUS(pstat));
331 			editpid = -1;
332 			break;
333 		} else {
334 			unlink(tempname);
335 			editpid = -1;
336 			break;
337 		}
338 	}
339 	sigaction(SIGINT, &sa_int, NULL);
340 	sigaction(SIGQUIT, &sa_quit, NULL);
341 	sigprocmask(SIG_SETMASK, &oldsigset, NULL);
342 	if (stat(tempname, &st2) == -1)
343 		return (-1);
344 	return (st1.st_mtim.tv_sec != st2.st_mtim.tv_sec ||
345 	    st1.st_mtim.tv_nsec != st2.st_mtim.tv_nsec);
346 }
347 
348 /*
349  * Clean up.  Preserve errno for the caller's convenience.
350  */
351 void
352 pw_fini(void)
353 {
354 	int serrno, status;
355 
356 	if (!initialized)
357 		return;
358 	initialized = 0;
359 	serrno = errno;
360 	if (editpid != -1) {
361 		kill(editpid, SIGTERM);
362 		kill(editpid, SIGCONT);
363 		waitpid(editpid, &status, 0);
364 		editpid = -1;
365 	}
366 	if (*tempname != '\0') {
367 		unlink(tempname);
368 		*tempname = '\0';
369 	}
370 	if (lockfd != -1)
371 		close(lockfd);
372 	errno = serrno;
373 }
374 
375 /*
376  * Compares two struct pwds.
377  */
378 int
379 pw_equal(const struct passwd *pw1, const struct passwd *pw2)
380 {
381 	return (strcmp(pw1->pw_name, pw2->pw_name) == 0 &&
382 	    pw1->pw_uid == pw2->pw_uid &&
383 	    pw1->pw_gid == pw2->pw_gid &&
384 	    strcmp(pw1->pw_class, pw2->pw_class) == 0 &&
385 	    pw1->pw_change == pw2->pw_change &&
386 	    pw1->pw_expire == pw2->pw_expire &&
387 	    strcmp(pw1->pw_gecos, pw2->pw_gecos) == 0 &&
388 	    strcmp(pw1->pw_dir, pw2->pw_dir) == 0 &&
389 	    strcmp(pw1->pw_shell, pw2->pw_shell) == 0);
390 }
391 
392 /*
393  * Make a passwd line out of a struct passwd.
394  */
395 char *
396 pw_make(const struct passwd *pw)
397 {
398 	char *line;
399 
400 	asprintf(&line, "%s:%s:%ju:%ju:%s:%ju:%ju:%s:%s:%s", pw->pw_name,
401 	    pw->pw_passwd, (uintmax_t)pw->pw_uid, (uintmax_t)pw->pw_gid,
402 	    pw->pw_class, (uintmax_t)pw->pw_change, (uintmax_t)pw->pw_expire,
403 	    pw->pw_gecos, pw->pw_dir, pw->pw_shell);
404 	return (line);
405 }
406 
407 /*
408  * Make a passwd line (in v7 format) out of a struct passwd
409  */
410 char *
411 pw_make_v7(const struct passwd *pw)
412 {
413 	char *line;
414 
415 	asprintf(&line, "%s:*:%ju:%ju:%s:%s:%s", pw->pw_name,
416 	    (uintmax_t)pw->pw_uid, (uintmax_t)pw->pw_gid,
417 	    pw->pw_gecos, pw->pw_dir, pw->pw_shell);
418 	return (line);
419 }
420 
421 /*
422  * Copy password file from one descriptor to another, replacing, deleting
423  * or adding a single record on the way.
424  */
425 int
426 pw_copy(int ffd, int tfd, const struct passwd *pw, struct passwd *old_pw)
427 {
428 	char *buf, *end, *line, *p, *q, *r, *tmp;
429 	struct passwd *fpw;
430 	const struct passwd *spw;
431 	size_t len, size;
432 	int eof, readlen;
433 	char t;
434 
435 	if (old_pw == NULL && pw == NULL)
436 			return (-1);
437 
438 	spw = old_pw;
439 	/* deleting a user */
440 	if (pw == NULL) {
441 		line = NULL;
442 	} else {
443 		if ((line = pw_make(pw)) == NULL)
444 			return (-1);
445 	}
446 
447 	/* adding a user */
448 	if (spw == NULL)
449 		spw = pw;
450 
451 	/* initialize the buffer */
452 	if ((buf = malloc(size = 1024)) == NULL)
453 		goto err;
454 
455 	eof = 0;
456 	len = 0;
457 	p = q = end = buf;
458 	for (;;) {
459 		/* find the end of the current line */
460 		for (p = q; q < end && *q != '\0'; ++q)
461 			if (*q == '\n')
462 				break;
463 
464 		/* if we don't have a complete line, fill up the buffer */
465 		if (q >= end) {
466 			if (eof)
467 				break;
468 			while ((size_t)(q - p) >= size) {
469 				if ((tmp = reallocarray(buf, 2, size)) == NULL) {
470 					warnx("passwd line too long");
471 					goto err;
472 				}
473 				p = tmp + (p - buf);
474 				q = tmp + (q - buf);
475 				end = tmp + (end - buf);
476 				buf = tmp;
477 				size = size * 2;
478 			}
479 			if (p < end) {
480 				q = memmove(buf, p, end - p);
481 				end -= p - buf;
482 			} else {
483 				p = q = end = buf;
484 			}
485 			readlen = read(ffd, end, size - (end - buf));
486 			if (readlen == -1)
487 				goto err;
488 			else
489 				len = (size_t)readlen;
490 			if (len == 0 && p == buf)
491 				break;
492 			end += len;
493 			len = end - buf;
494 			if (len < size) {
495 				eof = 1;
496 				if (len > 0 && buf[len - 1] != '\n')
497 					++len, *end++ = '\n';
498 			}
499 			continue;
500 		}
501 
502 		/* is it a blank line or a comment? */
503 		for (r = p; r < q && isspace(*r); ++r)
504 			/* nothing */ ;
505 		if (r == q || *r == '#') {
506 			/* yep */
507 			if (write(tfd, p, q - p + 1) != q - p + 1)
508 				goto err;
509 			++q;
510 			continue;
511 		}
512 
513 		/* is it the one we're looking for? */
514 
515 		t = *q;
516 		*q = '\0';
517 
518 		fpw = pw_scan(r, PWSCAN_MASTER);
519 
520 		/*
521 		 * fpw is either the struct passwd for the current line,
522 		 * or NULL if the line is malformed.
523 		 */
524 
525 		*q = t;
526 		if (fpw == NULL || strcmp(fpw->pw_name, spw->pw_name) != 0) {
527 			/* nope */
528 			if (fpw != NULL)
529 				free(fpw);
530 			if (write(tfd, p, q - p + 1) != q - p + 1)
531 				goto err;
532 			++q;
533 			continue;
534 		}
535 		if (old_pw && !pw_equal(fpw, old_pw)) {
536 			warnx("entry inconsistent");
537 			free(fpw);
538 			errno = EINVAL; /* hack */
539 			goto err;
540 		}
541 		free(fpw);
542 
543 		/* it is, replace or remove it */
544 		if (line != NULL) {
545 			len = strlen(line);
546 			if (write(tfd, line, len) != (int)len)
547 				goto err;
548 		} else {
549 			/* when removed, avoid the \n */
550 			q++;
551 		}
552 		/* we're done, just copy the rest over */
553 		for (;;) {
554 			if (write(tfd, q, end - q) != end - q)
555 				goto err;
556 			q = buf;
557 			readlen = read(ffd, buf, size);
558 			if (readlen == 0)
559 				break;
560 			else
561 				len = (size_t)readlen;
562 			if (readlen == -1)
563 				goto err;
564 			end = buf + len;
565 		}
566 		goto done;
567 	}
568 
569 	/* if we got here, we didn't find the old entry */
570 	if (line == NULL) {
571 		errno = ENOENT;
572 		goto err;
573 	}
574 	len = strlen(line);
575 	if ((size_t)write(tfd, line, len) != len ||
576 	    write(tfd, "\n", 1) != 1)
577 		goto err;
578  done:
579 	free(line);
580 	free(buf);
581 	return (0);
582  err:
583 	free(line);
584 	free(buf);
585 	return (-1);
586 }
587 
588 /*
589  * Return the current value of tempname.
590  */
591 const char *
592 pw_tempname(void)
593 {
594 
595 	return (tempname);
596 }
597 
598 /*
599  * Duplicate a struct passwd.
600  */
601 struct passwd *
602 pw_dup(const struct passwd *pw)
603 {
604 	char *dst;
605 	struct passwd *npw;
606 	ssize_t len;
607 
608 	len = sizeof(*npw);
609 	if (pw->pw_name != NULL)
610 		len += strlen(pw->pw_name) + 1;
611 	if (pw->pw_passwd != NULL)
612 		len += strlen(pw->pw_passwd) + 1;
613 	if (pw->pw_class != NULL)
614 		len += strlen(pw->pw_class) + 1;
615 	if (pw->pw_gecos != NULL)
616 		len += strlen(pw->pw_gecos) + 1;
617 	if (pw->pw_dir != NULL)
618 		len += strlen(pw->pw_dir) + 1;
619 	if (pw->pw_shell != NULL)
620 		len += strlen(pw->pw_shell) + 1;
621 	if ((npw = malloc((size_t)len)) == NULL)
622 		return (NULL);
623 	memcpy(npw, pw, sizeof(*npw));
624 	dst = (char *)npw + sizeof(*npw);
625 	if (pw->pw_name != NULL) {
626 		npw->pw_name = dst;
627 		dst = stpcpy(npw->pw_name, pw->pw_name) + 1;
628 	}
629 	if (pw->pw_passwd != NULL) {
630 		npw->pw_passwd = dst;
631 		dst = stpcpy(npw->pw_passwd, pw->pw_passwd) + 1;
632 	}
633 	if (pw->pw_class != NULL) {
634 		npw->pw_class = dst;
635 		dst = stpcpy(npw->pw_class, pw->pw_class) + 1;
636 	}
637 	if (pw->pw_gecos != NULL) {
638 		npw->pw_gecos = dst;
639 		dst = stpcpy(npw->pw_gecos, pw->pw_gecos) + 1;
640 	}
641 	if (pw->pw_dir != NULL) {
642 		npw->pw_dir = dst;
643 		dst = stpcpy(npw->pw_dir, pw->pw_dir) + 1;
644 	}
645 	if (pw->pw_shell != NULL) {
646 		npw->pw_shell = dst;
647 		dst = stpcpy(npw->pw_shell, pw->pw_shell) + 1;
648 	}
649 	return (npw);
650 }
651 
652 #include "pw_scan.h"
653 
654 /*
655  * Wrapper around some internal libc functions.
656  */
657 
658 void
659 pw_initpwd(struct passwd *pw)
660 {
661 
662 	__pw_initpwd(pw);
663 }
664 
665 struct passwd *
666 pw_scan(const char *line, int flags)
667 {
668 	struct passwd pw, *ret;
669 	char *bp;
670 
671 	if ((bp = strdup(line)) == NULL)
672 		return (NULL);
673 	__pw_initpwd(&pw);
674 	if (!__pw_scan(bp, &pw, flags)) {
675 		free(bp);
676 		return (NULL);
677 	}
678 	ret = pw_dup(&pw);
679 	free(bp);
680 	return (ret);
681 }
682