xref: /freebsd/sys/kern/kern_prot.c (revision edf8578117e8844e02c0121147f45e4609b30680)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1982, 1986, 1989, 1990, 1991, 1993
5  *	The Regents of the University of California.
6  * (c) UNIX System Laboratories, Inc.
7  * Copyright (c) 2000-2001 Robert N. M. Watson.
8  * All rights reserved.
9  *
10  * All or some portions of this file are derived from material licensed
11  * to the University of California by American Telephone and Telegraph
12  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
13  * the permission of UNIX System Laboratories, Inc.
14  *
15  * Redistribution and use in source and binary forms, with or without
16  * modification, are permitted provided that the following conditions
17  * are met:
18  * 1. Redistributions of source code must retain the above copyright
19  *    notice, this list of conditions and the following disclaimer.
20  * 2. Redistributions in binary form must reproduce the above copyright
21  *    notice, this list of conditions and the following disclaimer in the
22  *    documentation and/or other materials provided with the distribution.
23  * 3. Neither the name of the University nor the names of its contributors
24  *    may be used to endorse or promote products derived from this software
25  *    without specific prior written permission.
26  *
27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37  * SUCH DAMAGE.
38  *
39  *	@(#)kern_prot.c	8.6 (Berkeley) 1/21/94
40  */
41 
42 /*
43  * System calls related to processes and protection
44  */
45 
46 #include <sys/cdefs.h>
47 #include "opt_inet.h"
48 #include "opt_inet6.h"
49 
50 #include <sys/param.h>
51 #include <sys/systm.h>
52 #include <sys/acct.h>
53 #include <sys/kdb.h>
54 #include <sys/kernel.h>
55 #include <sys/lock.h>
56 #include <sys/loginclass.h>
57 #include <sys/malloc.h>
58 #include <sys/mutex.h>
59 #include <sys/ptrace.h>
60 #include <sys/refcount.h>
61 #include <sys/sx.h>
62 #include <sys/priv.h>
63 #include <sys/proc.h>
64 #ifdef COMPAT_43
65 #include <sys/sysent.h>
66 #endif
67 #include <sys/sysproto.h>
68 #include <sys/jail.h>
69 #include <sys/racct.h>
70 #include <sys/rctl.h>
71 #include <sys/resourcevar.h>
72 #include <sys/socket.h>
73 #include <sys/socketvar.h>
74 #include <sys/syscallsubr.h>
75 #include <sys/sysctl.h>
76 
77 #ifdef REGRESSION
78 FEATURE(regression,
79     "Kernel support for interfaces necessary for regression testing (SECURITY RISK!)");
80 #endif
81 
82 #include <security/audit/audit.h>
83 #include <security/mac/mac_framework.h>
84 
85 static MALLOC_DEFINE(M_CRED, "cred", "credentials");
86 
87 SYSCTL_NODE(_security, OID_AUTO, bsd, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
88     "BSD security policy");
89 
90 static void crfree_final(struct ucred *cr);
91 static void crsetgroups_locked(struct ucred *cr, int ngrp,
92     gid_t *groups);
93 
94 static int cr_canseeotheruids(struct ucred *u1, struct ucred *u2);
95 static int cr_canseeothergids(struct ucred *u1, struct ucred *u2);
96 static int cr_canseejailproc(struct ucred *u1, struct ucred *u2);
97 
98 #ifndef _SYS_SYSPROTO_H_
99 struct getpid_args {
100 	int	dummy;
101 };
102 #endif
103 /* ARGSUSED */
104 int
105 sys_getpid(struct thread *td, struct getpid_args *uap)
106 {
107 	struct proc *p = td->td_proc;
108 
109 	td->td_retval[0] = p->p_pid;
110 #if defined(COMPAT_43)
111 	if (SV_PROC_FLAG(p, SV_AOUT))
112 		td->td_retval[1] = kern_getppid(td);
113 #endif
114 	return (0);
115 }
116 
117 #ifndef _SYS_SYSPROTO_H_
118 struct getppid_args {
119         int     dummy;
120 };
121 #endif
122 /* ARGSUSED */
123 int
124 sys_getppid(struct thread *td, struct getppid_args *uap)
125 {
126 
127 	td->td_retval[0] = kern_getppid(td);
128 	return (0);
129 }
130 
131 int
132 kern_getppid(struct thread *td)
133 {
134 	struct proc *p = td->td_proc;
135 
136 	return (p->p_oppid);
137 }
138 
139 /*
140  * Get process group ID; note that POSIX getpgrp takes no parameter.
141  */
142 #ifndef _SYS_SYSPROTO_H_
143 struct getpgrp_args {
144         int     dummy;
145 };
146 #endif
147 int
148 sys_getpgrp(struct thread *td, struct getpgrp_args *uap)
149 {
150 	struct proc *p = td->td_proc;
151 
152 	PROC_LOCK(p);
153 	td->td_retval[0] = p->p_pgrp->pg_id;
154 	PROC_UNLOCK(p);
155 	return (0);
156 }
157 
158 /* Get an arbitrary pid's process group id */
159 #ifndef _SYS_SYSPROTO_H_
160 struct getpgid_args {
161 	pid_t	pid;
162 };
163 #endif
164 int
165 sys_getpgid(struct thread *td, struct getpgid_args *uap)
166 {
167 	struct proc *p;
168 	int error;
169 
170 	if (uap->pid == 0) {
171 		p = td->td_proc;
172 		PROC_LOCK(p);
173 	} else {
174 		p = pfind(uap->pid);
175 		if (p == NULL)
176 			return (ESRCH);
177 		error = p_cansee(td, p);
178 		if (error) {
179 			PROC_UNLOCK(p);
180 			return (error);
181 		}
182 	}
183 	td->td_retval[0] = p->p_pgrp->pg_id;
184 	PROC_UNLOCK(p);
185 	return (0);
186 }
187 
188 /*
189  * Get an arbitrary pid's session id.
190  */
191 #ifndef _SYS_SYSPROTO_H_
192 struct getsid_args {
193 	pid_t	pid;
194 };
195 #endif
196 int
197 sys_getsid(struct thread *td, struct getsid_args *uap)
198 {
199 
200 	return (kern_getsid(td, uap->pid));
201 }
202 
203 int
204 kern_getsid(struct thread *td, pid_t pid)
205 {
206 	struct proc *p;
207 	int error;
208 
209 	if (pid == 0) {
210 		p = td->td_proc;
211 		PROC_LOCK(p);
212 	} else {
213 		p = pfind(pid);
214 		if (p == NULL)
215 			return (ESRCH);
216 		error = p_cansee(td, p);
217 		if (error) {
218 			PROC_UNLOCK(p);
219 			return (error);
220 		}
221 	}
222 	td->td_retval[0] = p->p_session->s_sid;
223 	PROC_UNLOCK(p);
224 	return (0);
225 }
226 
227 #ifndef _SYS_SYSPROTO_H_
228 struct getuid_args {
229         int     dummy;
230 };
231 #endif
232 /* ARGSUSED */
233 int
234 sys_getuid(struct thread *td, struct getuid_args *uap)
235 {
236 
237 	td->td_retval[0] = td->td_ucred->cr_ruid;
238 #if defined(COMPAT_43)
239 	td->td_retval[1] = td->td_ucred->cr_uid;
240 #endif
241 	return (0);
242 }
243 
244 #ifndef _SYS_SYSPROTO_H_
245 struct geteuid_args {
246         int     dummy;
247 };
248 #endif
249 /* ARGSUSED */
250 int
251 sys_geteuid(struct thread *td, struct geteuid_args *uap)
252 {
253 
254 	td->td_retval[0] = td->td_ucred->cr_uid;
255 	return (0);
256 }
257 
258 #ifndef _SYS_SYSPROTO_H_
259 struct getgid_args {
260         int     dummy;
261 };
262 #endif
263 /* ARGSUSED */
264 int
265 sys_getgid(struct thread *td, struct getgid_args *uap)
266 {
267 
268 	td->td_retval[0] = td->td_ucred->cr_rgid;
269 #if defined(COMPAT_43)
270 	td->td_retval[1] = td->td_ucred->cr_groups[0];
271 #endif
272 	return (0);
273 }
274 
275 /*
276  * Get effective group ID.  The "egid" is groups[0], and could be obtained
277  * via getgroups.  This syscall exists because it is somewhat painful to do
278  * correctly in a library function.
279  */
280 #ifndef _SYS_SYSPROTO_H_
281 struct getegid_args {
282         int     dummy;
283 };
284 #endif
285 /* ARGSUSED */
286 int
287 sys_getegid(struct thread *td, struct getegid_args *uap)
288 {
289 
290 	td->td_retval[0] = td->td_ucred->cr_groups[0];
291 	return (0);
292 }
293 
294 #ifndef _SYS_SYSPROTO_H_
295 struct getgroups_args {
296 	int	gidsetsize;
297 	gid_t	*gidset;
298 };
299 #endif
300 int
301 sys_getgroups(struct thread *td, struct getgroups_args *uap)
302 {
303 	struct ucred *cred;
304 	int ngrp, error;
305 
306 	cred = td->td_ucred;
307 	ngrp = cred->cr_ngroups;
308 
309 	if (uap->gidsetsize == 0) {
310 		error = 0;
311 		goto out;
312 	}
313 	if (uap->gidsetsize < ngrp)
314 		return (EINVAL);
315 
316 	error = copyout(cred->cr_groups, uap->gidset, ngrp * sizeof(gid_t));
317 out:
318 	td->td_retval[0] = ngrp;
319 	return (error);
320 }
321 
322 #ifndef _SYS_SYSPROTO_H_
323 struct setsid_args {
324         int     dummy;
325 };
326 #endif
327 /* ARGSUSED */
328 int
329 sys_setsid(struct thread *td, struct setsid_args *uap)
330 {
331 	struct pgrp *pgrp;
332 	int error;
333 	struct proc *p = td->td_proc;
334 	struct pgrp *newpgrp;
335 	struct session *newsess;
336 
337 	pgrp = NULL;
338 
339 	newpgrp = uma_zalloc(pgrp_zone, M_WAITOK);
340 	newsess = malloc(sizeof(struct session), M_SESSION, M_WAITOK | M_ZERO);
341 
342 again:
343 	error = 0;
344 	sx_xlock(&proctree_lock);
345 
346 	if (p->p_pgid == p->p_pid || (pgrp = pgfind(p->p_pid)) != NULL) {
347 		if (pgrp != NULL)
348 			PGRP_UNLOCK(pgrp);
349 		error = EPERM;
350 	} else {
351 		error = enterpgrp(p, p->p_pid, newpgrp, newsess);
352 		if (error == ERESTART)
353 			goto again;
354 		MPASS(error == 0);
355 		td->td_retval[0] = p->p_pid;
356 		newpgrp = NULL;
357 		newsess = NULL;
358 	}
359 
360 	sx_xunlock(&proctree_lock);
361 
362 	uma_zfree(pgrp_zone, newpgrp);
363 	free(newsess, M_SESSION);
364 
365 	return (error);
366 }
367 
368 /*
369  * set process group (setpgid/old setpgrp)
370  *
371  * caller does setpgid(targpid, targpgid)
372  *
373  * pid must be caller or child of caller (ESRCH)
374  * if a child
375  *	pid must be in same session (EPERM)
376  *	pid can't have done an exec (EACCES)
377  * if pgid != pid
378  * 	there must exist some pid in same session having pgid (EPERM)
379  * pid must not be session leader (EPERM)
380  */
381 #ifndef _SYS_SYSPROTO_H_
382 struct setpgid_args {
383 	int	pid;		/* target process id */
384 	int	pgid;		/* target pgrp id */
385 };
386 #endif
387 /* ARGSUSED */
388 int
389 sys_setpgid(struct thread *td, struct setpgid_args *uap)
390 {
391 	struct proc *curp = td->td_proc;
392 	struct proc *targp;	/* target process */
393 	struct pgrp *pgrp;	/* target pgrp */
394 	int error;
395 	struct pgrp *newpgrp;
396 
397 	if (uap->pgid < 0)
398 		return (EINVAL);
399 
400 	newpgrp = uma_zalloc(pgrp_zone, M_WAITOK);
401 
402 again:
403 	error = 0;
404 
405 	sx_xlock(&proctree_lock);
406 	if (uap->pid != 0 && uap->pid != curp->p_pid) {
407 		if ((targp = pfind(uap->pid)) == NULL) {
408 			error = ESRCH;
409 			goto done;
410 		}
411 		if (!inferior(targp)) {
412 			PROC_UNLOCK(targp);
413 			error = ESRCH;
414 			goto done;
415 		}
416 		if ((error = p_cansee(td, targp))) {
417 			PROC_UNLOCK(targp);
418 			goto done;
419 		}
420 		if (targp->p_pgrp == NULL ||
421 		    targp->p_session != curp->p_session) {
422 			PROC_UNLOCK(targp);
423 			error = EPERM;
424 			goto done;
425 		}
426 		if (targp->p_flag & P_EXEC) {
427 			PROC_UNLOCK(targp);
428 			error = EACCES;
429 			goto done;
430 		}
431 		PROC_UNLOCK(targp);
432 	} else
433 		targp = curp;
434 	if (SESS_LEADER(targp)) {
435 		error = EPERM;
436 		goto done;
437 	}
438 	if (uap->pgid == 0)
439 		uap->pgid = targp->p_pid;
440 	if ((pgrp = pgfind(uap->pgid)) == NULL) {
441 		if (uap->pgid == targp->p_pid) {
442 			error = enterpgrp(targp, uap->pgid, newpgrp,
443 			    NULL);
444 			if (error == 0)
445 				newpgrp = NULL;
446 		} else
447 			error = EPERM;
448 	} else {
449 		if (pgrp == targp->p_pgrp) {
450 			PGRP_UNLOCK(pgrp);
451 			goto done;
452 		}
453 		if (pgrp->pg_id != targp->p_pid &&
454 		    pgrp->pg_session != curp->p_session) {
455 			PGRP_UNLOCK(pgrp);
456 			error = EPERM;
457 			goto done;
458 		}
459 		PGRP_UNLOCK(pgrp);
460 		error = enterthispgrp(targp, pgrp);
461 	}
462 done:
463 	KASSERT(error == 0 || newpgrp != NULL,
464 	    ("setpgid failed and newpgrp is NULL"));
465 	if (error == ERESTART)
466 		goto again;
467 	sx_xunlock(&proctree_lock);
468 	uma_zfree(pgrp_zone, newpgrp);
469 	return (error);
470 }
471 
472 /*
473  * Use the clause in B.4.2.2 that allows setuid/setgid to be 4.2/4.3BSD
474  * compatible.  It says that setting the uid/gid to euid/egid is a special
475  * case of "appropriate privilege".  Once the rules are expanded out, this
476  * basically means that setuid(nnn) sets all three id's, in all permitted
477  * cases unless _POSIX_SAVED_IDS is enabled.  In that case, setuid(getuid())
478  * does not set the saved id - this is dangerous for traditional BSD
479  * programs.  For this reason, we *really* do not want to set
480  * _POSIX_SAVED_IDS and do not want to clear POSIX_APPENDIX_B_4_2_2.
481  */
482 #define POSIX_APPENDIX_B_4_2_2
483 
484 #ifndef _SYS_SYSPROTO_H_
485 struct setuid_args {
486 	uid_t	uid;
487 };
488 #endif
489 /* ARGSUSED */
490 int
491 sys_setuid(struct thread *td, struct setuid_args *uap)
492 {
493 	struct proc *p = td->td_proc;
494 	struct ucred *newcred, *oldcred;
495 	uid_t uid;
496 	struct uidinfo *uip;
497 	int error;
498 
499 	uid = uap->uid;
500 	AUDIT_ARG_UID(uid);
501 	newcred = crget();
502 	uip = uifind(uid);
503 	PROC_LOCK(p);
504 	/*
505 	 * Copy credentials so other references do not see our changes.
506 	 */
507 	oldcred = crcopysafe(p, newcred);
508 
509 #ifdef MAC
510 	error = mac_cred_check_setuid(oldcred, uid);
511 	if (error)
512 		goto fail;
513 #endif
514 
515 	/*
516 	 * See if we have "permission" by POSIX 1003.1 rules.
517 	 *
518 	 * Note that setuid(geteuid()) is a special case of
519 	 * "appropriate privileges" in appendix B.4.2.2.  We need
520 	 * to use this clause to be compatible with traditional BSD
521 	 * semantics.  Basically, it means that "setuid(xx)" sets all
522 	 * three id's (assuming you have privs).
523 	 *
524 	 * Notes on the logic.  We do things in three steps.
525 	 * 1: We determine if the euid is going to change, and do EPERM
526 	 *    right away.  We unconditionally change the euid later if this
527 	 *    test is satisfied, simplifying that part of the logic.
528 	 * 2: We determine if the real and/or saved uids are going to
529 	 *    change.  Determined by compile options.
530 	 * 3: Change euid last. (after tests in #2 for "appropriate privs")
531 	 */
532 	if (uid != oldcred->cr_ruid &&		/* allow setuid(getuid()) */
533 #ifdef _POSIX_SAVED_IDS
534 	    uid != oldcred->cr_svuid &&		/* allow setuid(saved gid) */
535 #endif
536 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
537 	    uid != oldcred->cr_uid &&		/* allow setuid(geteuid()) */
538 #endif
539 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETUID)) != 0)
540 		goto fail;
541 
542 #ifdef _POSIX_SAVED_IDS
543 	/*
544 	 * Do we have "appropriate privileges" (are we root or uid == euid)
545 	 * If so, we are changing the real uid and/or saved uid.
546 	 */
547 	if (
548 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use the clause from B.4.2.2 */
549 	    uid == oldcred->cr_uid ||
550 #endif
551 	    /* We are using privs. */
552 	    priv_check_cred(oldcred, PRIV_CRED_SETUID) == 0)
553 #endif
554 	{
555 		/*
556 		 * Set the real uid and transfer proc count to new user.
557 		 */
558 		if (uid != oldcred->cr_ruid) {
559 			change_ruid(newcred, uip);
560 			setsugid(p);
561 		}
562 		/*
563 		 * Set saved uid
564 		 *
565 		 * XXX always set saved uid even if not _POSIX_SAVED_IDS, as
566 		 * the security of seteuid() depends on it.  B.4.2.2 says it
567 		 * is important that we should do this.
568 		 */
569 		if (uid != oldcred->cr_svuid) {
570 			change_svuid(newcred, uid);
571 			setsugid(p);
572 		}
573 	}
574 
575 	/*
576 	 * In all permitted cases, we are changing the euid.
577 	 */
578 	if (uid != oldcred->cr_uid) {
579 		change_euid(newcred, uip);
580 		setsugid(p);
581 	}
582 	proc_set_cred(p, newcred);
583 #ifdef RACCT
584 	racct_proc_ucred_changed(p, oldcred, newcred);
585 	crhold(newcred);
586 #endif
587 	PROC_UNLOCK(p);
588 #ifdef RCTL
589 	rctl_proc_ucred_changed(p, newcred);
590 	crfree(newcred);
591 #endif
592 	uifree(uip);
593 	crfree(oldcred);
594 	return (0);
595 
596 fail:
597 	PROC_UNLOCK(p);
598 	uifree(uip);
599 	crfree(newcred);
600 	return (error);
601 }
602 
603 #ifndef _SYS_SYSPROTO_H_
604 struct seteuid_args {
605 	uid_t	euid;
606 };
607 #endif
608 /* ARGSUSED */
609 int
610 sys_seteuid(struct thread *td, struct seteuid_args *uap)
611 {
612 	struct proc *p = td->td_proc;
613 	struct ucred *newcred, *oldcred;
614 	uid_t euid;
615 	struct uidinfo *euip;
616 	int error;
617 
618 	euid = uap->euid;
619 	AUDIT_ARG_EUID(euid);
620 	newcred = crget();
621 	euip = uifind(euid);
622 	PROC_LOCK(p);
623 	/*
624 	 * Copy credentials so other references do not see our changes.
625 	 */
626 	oldcred = crcopysafe(p, newcred);
627 
628 #ifdef MAC
629 	error = mac_cred_check_seteuid(oldcred, euid);
630 	if (error)
631 		goto fail;
632 #endif
633 
634 	if (euid != oldcred->cr_ruid &&		/* allow seteuid(getuid()) */
635 	    euid != oldcred->cr_svuid &&	/* allow seteuid(saved uid) */
636 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETEUID)) != 0)
637 		goto fail;
638 
639 	/*
640 	 * Everything's okay, do it.
641 	 */
642 	if (oldcred->cr_uid != euid) {
643 		change_euid(newcred, euip);
644 		setsugid(p);
645 	}
646 	proc_set_cred(p, newcred);
647 	PROC_UNLOCK(p);
648 	uifree(euip);
649 	crfree(oldcred);
650 	return (0);
651 
652 fail:
653 	PROC_UNLOCK(p);
654 	uifree(euip);
655 	crfree(newcred);
656 	return (error);
657 }
658 
659 #ifndef _SYS_SYSPROTO_H_
660 struct setgid_args {
661 	gid_t	gid;
662 };
663 #endif
664 /* ARGSUSED */
665 int
666 sys_setgid(struct thread *td, struct setgid_args *uap)
667 {
668 	struct proc *p = td->td_proc;
669 	struct ucred *newcred, *oldcred;
670 	gid_t gid;
671 	int error;
672 
673 	gid = uap->gid;
674 	AUDIT_ARG_GID(gid);
675 	newcred = crget();
676 	PROC_LOCK(p);
677 	oldcred = crcopysafe(p, newcred);
678 
679 #ifdef MAC
680 	error = mac_cred_check_setgid(oldcred, gid);
681 	if (error)
682 		goto fail;
683 #endif
684 
685 	/*
686 	 * See if we have "permission" by POSIX 1003.1 rules.
687 	 *
688 	 * Note that setgid(getegid()) is a special case of
689 	 * "appropriate privileges" in appendix B.4.2.2.  We need
690 	 * to use this clause to be compatible with traditional BSD
691 	 * semantics.  Basically, it means that "setgid(xx)" sets all
692 	 * three id's (assuming you have privs).
693 	 *
694 	 * For notes on the logic here, see setuid() above.
695 	 */
696 	if (gid != oldcred->cr_rgid &&		/* allow setgid(getgid()) */
697 #ifdef _POSIX_SAVED_IDS
698 	    gid != oldcred->cr_svgid &&		/* allow setgid(saved gid) */
699 #endif
700 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
701 	    gid != oldcred->cr_groups[0] && /* allow setgid(getegid()) */
702 #endif
703 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETGID)) != 0)
704 		goto fail;
705 
706 #ifdef _POSIX_SAVED_IDS
707 	/*
708 	 * Do we have "appropriate privileges" (are we root or gid == egid)
709 	 * If so, we are changing the real uid and saved gid.
710 	 */
711 	if (
712 #ifdef POSIX_APPENDIX_B_4_2_2	/* use the clause from B.4.2.2 */
713 	    gid == oldcred->cr_groups[0] ||
714 #endif
715 	    /* We are using privs. */
716 	    priv_check_cred(oldcred, PRIV_CRED_SETGID) == 0)
717 #endif
718 	{
719 		/*
720 		 * Set real gid
721 		 */
722 		if (oldcred->cr_rgid != gid) {
723 			change_rgid(newcred, gid);
724 			setsugid(p);
725 		}
726 		/*
727 		 * Set saved gid
728 		 *
729 		 * XXX always set saved gid even if not _POSIX_SAVED_IDS, as
730 		 * the security of setegid() depends on it.  B.4.2.2 says it
731 		 * is important that we should do this.
732 		 */
733 		if (oldcred->cr_svgid != gid) {
734 			change_svgid(newcred, gid);
735 			setsugid(p);
736 		}
737 	}
738 	/*
739 	 * In all cases permitted cases, we are changing the egid.
740 	 * Copy credentials so other references do not see our changes.
741 	 */
742 	if (oldcred->cr_groups[0] != gid) {
743 		change_egid(newcred, gid);
744 		setsugid(p);
745 	}
746 	proc_set_cred(p, newcred);
747 	PROC_UNLOCK(p);
748 	crfree(oldcred);
749 	return (0);
750 
751 fail:
752 	PROC_UNLOCK(p);
753 	crfree(newcred);
754 	return (error);
755 }
756 
757 #ifndef _SYS_SYSPROTO_H_
758 struct setegid_args {
759 	gid_t	egid;
760 };
761 #endif
762 /* ARGSUSED */
763 int
764 sys_setegid(struct thread *td, struct setegid_args *uap)
765 {
766 	struct proc *p = td->td_proc;
767 	struct ucred *newcred, *oldcred;
768 	gid_t egid;
769 	int error;
770 
771 	egid = uap->egid;
772 	AUDIT_ARG_EGID(egid);
773 	newcred = crget();
774 	PROC_LOCK(p);
775 	oldcred = crcopysafe(p, newcred);
776 
777 #ifdef MAC
778 	error = mac_cred_check_setegid(oldcred, egid);
779 	if (error)
780 		goto fail;
781 #endif
782 
783 	if (egid != oldcred->cr_rgid &&		/* allow setegid(getgid()) */
784 	    egid != oldcred->cr_svgid &&	/* allow setegid(saved gid) */
785 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETEGID)) != 0)
786 		goto fail;
787 
788 	if (oldcred->cr_groups[0] != egid) {
789 		change_egid(newcred, egid);
790 		setsugid(p);
791 	}
792 	proc_set_cred(p, newcred);
793 	PROC_UNLOCK(p);
794 	crfree(oldcred);
795 	return (0);
796 
797 fail:
798 	PROC_UNLOCK(p);
799 	crfree(newcred);
800 	return (error);
801 }
802 
803 #ifndef _SYS_SYSPROTO_H_
804 struct setgroups_args {
805 	int	gidsetsize;
806 	gid_t	*gidset;
807 };
808 #endif
809 /* ARGSUSED */
810 int
811 sys_setgroups(struct thread *td, struct setgroups_args *uap)
812 {
813 	gid_t smallgroups[XU_NGROUPS];
814 	gid_t *groups;
815 	int gidsetsize, error;
816 
817 	gidsetsize = uap->gidsetsize;
818 	if (gidsetsize > ngroups_max + 1 || gidsetsize < 0)
819 		return (EINVAL);
820 
821 	if (gidsetsize > XU_NGROUPS)
822 		groups = malloc(gidsetsize * sizeof(gid_t), M_TEMP, M_WAITOK);
823 	else
824 		groups = smallgroups;
825 
826 	error = copyin(uap->gidset, groups, gidsetsize * sizeof(gid_t));
827 	if (error == 0)
828 		error = kern_setgroups(td, gidsetsize, groups);
829 
830 	if (gidsetsize > XU_NGROUPS)
831 		free(groups, M_TEMP);
832 	return (error);
833 }
834 
835 int
836 kern_setgroups(struct thread *td, u_int ngrp, gid_t *groups)
837 {
838 	struct proc *p = td->td_proc;
839 	struct ucred *newcred, *oldcred;
840 	int error;
841 
842 	MPASS(ngrp <= ngroups_max + 1);
843 	AUDIT_ARG_GROUPSET(groups, ngrp);
844 	newcred = crget();
845 	crextend(newcred, ngrp);
846 	PROC_LOCK(p);
847 	oldcred = crcopysafe(p, newcred);
848 
849 #ifdef MAC
850 	error = mac_cred_check_setgroups(oldcred, ngrp, groups);
851 	if (error)
852 		goto fail;
853 #endif
854 
855 	error = priv_check_cred(oldcred, PRIV_CRED_SETGROUPS);
856 	if (error)
857 		goto fail;
858 
859 	if (ngrp == 0) {
860 		/*
861 		 * setgroups(0, NULL) is a legitimate way of clearing the
862 		 * groups vector on non-BSD systems (which generally do not
863 		 * have the egid in the groups[0]).  We risk security holes
864 		 * when running non-BSD software if we do not do the same.
865 		 */
866 		newcred->cr_ngroups = 1;
867 	} else {
868 		crsetgroups_locked(newcred, ngrp, groups);
869 	}
870 	setsugid(p);
871 	proc_set_cred(p, newcred);
872 	PROC_UNLOCK(p);
873 	crfree(oldcred);
874 	return (0);
875 
876 fail:
877 	PROC_UNLOCK(p);
878 	crfree(newcred);
879 	return (error);
880 }
881 
882 #ifndef _SYS_SYSPROTO_H_
883 struct setreuid_args {
884 	uid_t	ruid;
885 	uid_t	euid;
886 };
887 #endif
888 /* ARGSUSED */
889 int
890 sys_setreuid(struct thread *td, struct setreuid_args *uap)
891 {
892 	struct proc *p = td->td_proc;
893 	struct ucred *newcred, *oldcred;
894 	uid_t euid, ruid;
895 	struct uidinfo *euip, *ruip;
896 	int error;
897 
898 	euid = uap->euid;
899 	ruid = uap->ruid;
900 	AUDIT_ARG_EUID(euid);
901 	AUDIT_ARG_RUID(ruid);
902 	newcred = crget();
903 	euip = uifind(euid);
904 	ruip = uifind(ruid);
905 	PROC_LOCK(p);
906 	oldcred = crcopysafe(p, newcred);
907 
908 #ifdef MAC
909 	error = mac_cred_check_setreuid(oldcred, ruid, euid);
910 	if (error)
911 		goto fail;
912 #endif
913 
914 	if (((ruid != (uid_t)-1 && ruid != oldcred->cr_ruid &&
915 	      ruid != oldcred->cr_svuid) ||
916 	     (euid != (uid_t)-1 && euid != oldcred->cr_uid &&
917 	      euid != oldcred->cr_ruid && euid != oldcred->cr_svuid)) &&
918 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETREUID)) != 0)
919 		goto fail;
920 
921 	if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
922 		change_euid(newcred, euip);
923 		setsugid(p);
924 	}
925 	if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
926 		change_ruid(newcred, ruip);
927 		setsugid(p);
928 	}
929 	if ((ruid != (uid_t)-1 || newcred->cr_uid != newcred->cr_ruid) &&
930 	    newcred->cr_svuid != newcred->cr_uid) {
931 		change_svuid(newcred, newcred->cr_uid);
932 		setsugid(p);
933 	}
934 	proc_set_cred(p, newcred);
935 #ifdef RACCT
936 	racct_proc_ucred_changed(p, oldcred, newcred);
937 	crhold(newcred);
938 #endif
939 	PROC_UNLOCK(p);
940 #ifdef RCTL
941 	rctl_proc_ucred_changed(p, newcred);
942 	crfree(newcred);
943 #endif
944 	uifree(ruip);
945 	uifree(euip);
946 	crfree(oldcred);
947 	return (0);
948 
949 fail:
950 	PROC_UNLOCK(p);
951 	uifree(ruip);
952 	uifree(euip);
953 	crfree(newcred);
954 	return (error);
955 }
956 
957 #ifndef _SYS_SYSPROTO_H_
958 struct setregid_args {
959 	gid_t	rgid;
960 	gid_t	egid;
961 };
962 #endif
963 /* ARGSUSED */
964 int
965 sys_setregid(struct thread *td, struct setregid_args *uap)
966 {
967 	struct proc *p = td->td_proc;
968 	struct ucred *newcred, *oldcred;
969 	gid_t egid, rgid;
970 	int error;
971 
972 	egid = uap->egid;
973 	rgid = uap->rgid;
974 	AUDIT_ARG_EGID(egid);
975 	AUDIT_ARG_RGID(rgid);
976 	newcred = crget();
977 	PROC_LOCK(p);
978 	oldcred = crcopysafe(p, newcred);
979 
980 #ifdef MAC
981 	error = mac_cred_check_setregid(oldcred, rgid, egid);
982 	if (error)
983 		goto fail;
984 #endif
985 
986 	if (((rgid != (gid_t)-1 && rgid != oldcred->cr_rgid &&
987 	    rgid != oldcred->cr_svgid) ||
988 	     (egid != (gid_t)-1 && egid != oldcred->cr_groups[0] &&
989 	     egid != oldcred->cr_rgid && egid != oldcred->cr_svgid)) &&
990 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETREGID)) != 0)
991 		goto fail;
992 
993 	if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
994 		change_egid(newcred, egid);
995 		setsugid(p);
996 	}
997 	if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
998 		change_rgid(newcred, rgid);
999 		setsugid(p);
1000 	}
1001 	if ((rgid != (gid_t)-1 || newcred->cr_groups[0] != newcred->cr_rgid) &&
1002 	    newcred->cr_svgid != newcred->cr_groups[0]) {
1003 		change_svgid(newcred, newcred->cr_groups[0]);
1004 		setsugid(p);
1005 	}
1006 	proc_set_cred(p, newcred);
1007 	PROC_UNLOCK(p);
1008 	crfree(oldcred);
1009 	return (0);
1010 
1011 fail:
1012 	PROC_UNLOCK(p);
1013 	crfree(newcred);
1014 	return (error);
1015 }
1016 
1017 /*
1018  * setresuid(ruid, euid, suid) is like setreuid except control over the saved
1019  * uid is explicit.
1020  */
1021 #ifndef _SYS_SYSPROTO_H_
1022 struct setresuid_args {
1023 	uid_t	ruid;
1024 	uid_t	euid;
1025 	uid_t	suid;
1026 };
1027 #endif
1028 /* ARGSUSED */
1029 int
1030 sys_setresuid(struct thread *td, struct setresuid_args *uap)
1031 {
1032 	struct proc *p = td->td_proc;
1033 	struct ucred *newcred, *oldcred;
1034 	uid_t euid, ruid, suid;
1035 	struct uidinfo *euip, *ruip;
1036 	int error;
1037 
1038 	euid = uap->euid;
1039 	ruid = uap->ruid;
1040 	suid = uap->suid;
1041 	AUDIT_ARG_EUID(euid);
1042 	AUDIT_ARG_RUID(ruid);
1043 	AUDIT_ARG_SUID(suid);
1044 	newcred = crget();
1045 	euip = uifind(euid);
1046 	ruip = uifind(ruid);
1047 	PROC_LOCK(p);
1048 	oldcred = crcopysafe(p, newcred);
1049 
1050 #ifdef MAC
1051 	error = mac_cred_check_setresuid(oldcred, ruid, euid, suid);
1052 	if (error)
1053 		goto fail;
1054 #endif
1055 
1056 	if (((ruid != (uid_t)-1 && ruid != oldcred->cr_ruid &&
1057 	     ruid != oldcred->cr_svuid &&
1058 	      ruid != oldcred->cr_uid) ||
1059 	     (euid != (uid_t)-1 && euid != oldcred->cr_ruid &&
1060 	    euid != oldcred->cr_svuid &&
1061 	      euid != oldcred->cr_uid) ||
1062 	     (suid != (uid_t)-1 && suid != oldcred->cr_ruid &&
1063 	    suid != oldcred->cr_svuid &&
1064 	      suid != oldcred->cr_uid)) &&
1065 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETRESUID)) != 0)
1066 		goto fail;
1067 
1068 	if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
1069 		change_euid(newcred, euip);
1070 		setsugid(p);
1071 	}
1072 	if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
1073 		change_ruid(newcred, ruip);
1074 		setsugid(p);
1075 	}
1076 	if (suid != (uid_t)-1 && oldcred->cr_svuid != suid) {
1077 		change_svuid(newcred, suid);
1078 		setsugid(p);
1079 	}
1080 	proc_set_cred(p, newcred);
1081 #ifdef RACCT
1082 	racct_proc_ucred_changed(p, oldcred, newcred);
1083 	crhold(newcred);
1084 #endif
1085 	PROC_UNLOCK(p);
1086 #ifdef RCTL
1087 	rctl_proc_ucred_changed(p, newcred);
1088 	crfree(newcred);
1089 #endif
1090 	uifree(ruip);
1091 	uifree(euip);
1092 	crfree(oldcred);
1093 	return (0);
1094 
1095 fail:
1096 	PROC_UNLOCK(p);
1097 	uifree(ruip);
1098 	uifree(euip);
1099 	crfree(newcred);
1100 	return (error);
1101 
1102 }
1103 
1104 /*
1105  * setresgid(rgid, egid, sgid) is like setregid except control over the saved
1106  * gid is explicit.
1107  */
1108 #ifndef _SYS_SYSPROTO_H_
1109 struct setresgid_args {
1110 	gid_t	rgid;
1111 	gid_t	egid;
1112 	gid_t	sgid;
1113 };
1114 #endif
1115 /* ARGSUSED */
1116 int
1117 sys_setresgid(struct thread *td, struct setresgid_args *uap)
1118 {
1119 	struct proc *p = td->td_proc;
1120 	struct ucred *newcred, *oldcred;
1121 	gid_t egid, rgid, sgid;
1122 	int error;
1123 
1124 	egid = uap->egid;
1125 	rgid = uap->rgid;
1126 	sgid = uap->sgid;
1127 	AUDIT_ARG_EGID(egid);
1128 	AUDIT_ARG_RGID(rgid);
1129 	AUDIT_ARG_SGID(sgid);
1130 	newcred = crget();
1131 	PROC_LOCK(p);
1132 	oldcred = crcopysafe(p, newcred);
1133 
1134 #ifdef MAC
1135 	error = mac_cred_check_setresgid(oldcred, rgid, egid, sgid);
1136 	if (error)
1137 		goto fail;
1138 #endif
1139 
1140 	if (((rgid != (gid_t)-1 && rgid != oldcred->cr_rgid &&
1141 	      rgid != oldcred->cr_svgid &&
1142 	      rgid != oldcred->cr_groups[0]) ||
1143 	     (egid != (gid_t)-1 && egid != oldcred->cr_rgid &&
1144 	      egid != oldcred->cr_svgid &&
1145 	      egid != oldcred->cr_groups[0]) ||
1146 	     (sgid != (gid_t)-1 && sgid != oldcred->cr_rgid &&
1147 	      sgid != oldcred->cr_svgid &&
1148 	      sgid != oldcred->cr_groups[0])) &&
1149 	    (error = priv_check_cred(oldcred, PRIV_CRED_SETRESGID)) != 0)
1150 		goto fail;
1151 
1152 	if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
1153 		change_egid(newcred, egid);
1154 		setsugid(p);
1155 	}
1156 	if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
1157 		change_rgid(newcred, rgid);
1158 		setsugid(p);
1159 	}
1160 	if (sgid != (gid_t)-1 && oldcred->cr_svgid != sgid) {
1161 		change_svgid(newcred, sgid);
1162 		setsugid(p);
1163 	}
1164 	proc_set_cred(p, newcred);
1165 	PROC_UNLOCK(p);
1166 	crfree(oldcred);
1167 	return (0);
1168 
1169 fail:
1170 	PROC_UNLOCK(p);
1171 	crfree(newcred);
1172 	return (error);
1173 }
1174 
1175 #ifndef _SYS_SYSPROTO_H_
1176 struct getresuid_args {
1177 	uid_t	*ruid;
1178 	uid_t	*euid;
1179 	uid_t	*suid;
1180 };
1181 #endif
1182 /* ARGSUSED */
1183 int
1184 sys_getresuid(struct thread *td, struct getresuid_args *uap)
1185 {
1186 	struct ucred *cred;
1187 	int error1 = 0, error2 = 0, error3 = 0;
1188 
1189 	cred = td->td_ucred;
1190 	if (uap->ruid)
1191 		error1 = copyout(&cred->cr_ruid,
1192 		    uap->ruid, sizeof(cred->cr_ruid));
1193 	if (uap->euid)
1194 		error2 = copyout(&cred->cr_uid,
1195 		    uap->euid, sizeof(cred->cr_uid));
1196 	if (uap->suid)
1197 		error3 = copyout(&cred->cr_svuid,
1198 		    uap->suid, sizeof(cred->cr_svuid));
1199 	return (error1 ? error1 : error2 ? error2 : error3);
1200 }
1201 
1202 #ifndef _SYS_SYSPROTO_H_
1203 struct getresgid_args {
1204 	gid_t	*rgid;
1205 	gid_t	*egid;
1206 	gid_t	*sgid;
1207 };
1208 #endif
1209 /* ARGSUSED */
1210 int
1211 sys_getresgid(struct thread *td, struct getresgid_args *uap)
1212 {
1213 	struct ucred *cred;
1214 	int error1 = 0, error2 = 0, error3 = 0;
1215 
1216 	cred = td->td_ucred;
1217 	if (uap->rgid)
1218 		error1 = copyout(&cred->cr_rgid,
1219 		    uap->rgid, sizeof(cred->cr_rgid));
1220 	if (uap->egid)
1221 		error2 = copyout(&cred->cr_groups[0],
1222 		    uap->egid, sizeof(cred->cr_groups[0]));
1223 	if (uap->sgid)
1224 		error3 = copyout(&cred->cr_svgid,
1225 		    uap->sgid, sizeof(cred->cr_svgid));
1226 	return (error1 ? error1 : error2 ? error2 : error3);
1227 }
1228 
1229 #ifndef _SYS_SYSPROTO_H_
1230 struct issetugid_args {
1231 	int dummy;
1232 };
1233 #endif
1234 /* ARGSUSED */
1235 int
1236 sys_issetugid(struct thread *td, struct issetugid_args *uap)
1237 {
1238 	struct proc *p = td->td_proc;
1239 
1240 	/*
1241 	 * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
1242 	 * we use P_SUGID because we consider changing the owners as
1243 	 * "tainting" as well.
1244 	 * This is significant for procs that start as root and "become"
1245 	 * a user without an exec - programs cannot know *everything*
1246 	 * that libc *might* have put in their data segment.
1247 	 */
1248 	td->td_retval[0] = (p->p_flag & P_SUGID) ? 1 : 0;
1249 	return (0);
1250 }
1251 
1252 int
1253 sys___setugid(struct thread *td, struct __setugid_args *uap)
1254 {
1255 #ifdef REGRESSION
1256 	struct proc *p;
1257 
1258 	p = td->td_proc;
1259 	switch (uap->flag) {
1260 	case 0:
1261 		PROC_LOCK(p);
1262 		p->p_flag &= ~P_SUGID;
1263 		PROC_UNLOCK(p);
1264 		return (0);
1265 	case 1:
1266 		PROC_LOCK(p);
1267 		p->p_flag |= P_SUGID;
1268 		PROC_UNLOCK(p);
1269 		return (0);
1270 	default:
1271 		return (EINVAL);
1272 	}
1273 #else /* !REGRESSION */
1274 
1275 	return (ENOSYS);
1276 #endif /* REGRESSION */
1277 }
1278 
1279 /*
1280  * Returns whether gid designates a supplementary group in cred.
1281  */
1282 static bool
1283 supplementary_group_member(gid_t gid, struct ucred *cred)
1284 {
1285 	int l, h, m;
1286 
1287 	/*
1288 	 * Perform a binary search of the supplemental groups.  This is possible
1289 	 * because we sort the groups in crsetgroups().
1290 	 */
1291 	l = 1;
1292 	h = cred->cr_ngroups;
1293 
1294 	while (l < h) {
1295 		m = l + (h - l) / 2;
1296 		if (cred->cr_groups[m] < gid)
1297 			l = m + 1;
1298 		else
1299 			h = m;
1300 	}
1301 
1302 	return (l < cred->cr_ngroups && cred->cr_groups[l] == gid);
1303 }
1304 
1305 /*
1306  * Check if gid is a member of the (effective) group set (i.e., effective and
1307  * supplementary groups).
1308  */
1309 bool
1310 groupmember(gid_t gid, struct ucred *cred)
1311 {
1312 
1313 	if (gid == cred->cr_groups[0])
1314 		return (true);
1315 
1316 	return (supplementary_group_member(gid, cred));
1317 }
1318 
1319 /*
1320  * Check if gid is a member of the real group set (i.e., real and supplementary
1321  * groups).
1322  */
1323 bool
1324 realgroupmember(gid_t gid, struct ucred *cred)
1325 {
1326 	if (gid == cred->cr_rgid)
1327 		return (true);
1328 
1329 	return (supplementary_group_member(gid, cred));
1330 }
1331 
1332 /*
1333  * Test the active securelevel against a given level.  securelevel_gt()
1334  * implements (securelevel > level).  securelevel_ge() implements
1335  * (securelevel >= level).  Note that the logic is inverted -- these
1336  * functions return EPERM on "success" and 0 on "failure".
1337  *
1338  * Due to care taken when setting the securelevel, we know that no jail will
1339  * be less secure that its parent (or the physical system), so it is sufficient
1340  * to test the current jail only.
1341  *
1342  * XXXRW: Possibly since this has to do with privilege, it should move to
1343  * kern_priv.c.
1344  */
1345 int
1346 securelevel_gt(struct ucred *cr, int level)
1347 {
1348 
1349 	return (cr->cr_prison->pr_securelevel > level ? EPERM : 0);
1350 }
1351 
1352 int
1353 securelevel_ge(struct ucred *cr, int level)
1354 {
1355 
1356 	return (cr->cr_prison->pr_securelevel >= level ? EPERM : 0);
1357 }
1358 
1359 /*
1360  * 'see_other_uids' determines whether or not visibility of processes
1361  * and sockets with credentials holding different real uids is possible
1362  * using a variety of system MIBs.
1363  * XXX: data declarations should be together near the beginning of the file.
1364  */
1365 static int	see_other_uids = 1;
1366 SYSCTL_INT(_security_bsd, OID_AUTO, see_other_uids, CTLFLAG_RW,
1367     &see_other_uids, 0,
1368     "Unprivileged processes may see subjects/objects with different real uid");
1369 
1370 /*-
1371  * Determine if u1 "can see" the subject specified by u2, according to the
1372  * 'see_other_uids' policy.
1373  * Returns: 0 for permitted, ESRCH otherwise
1374  * Locks: none
1375  * References: *u1 and *u2 must not change during the call
1376  *             u1 may equal u2, in which case only one reference is required
1377  */
1378 static int
1379 cr_canseeotheruids(struct ucred *u1, struct ucred *u2)
1380 {
1381 
1382 	if (!see_other_uids && u1->cr_ruid != u2->cr_ruid) {
1383 		if (priv_check_cred(u1, PRIV_SEEOTHERUIDS) != 0)
1384 			return (ESRCH);
1385 	}
1386 	return (0);
1387 }
1388 
1389 /*
1390  * 'see_other_gids' determines whether or not visibility of processes
1391  * and sockets with credentials holding different real gids is possible
1392  * using a variety of system MIBs.
1393  * XXX: data declarations should be together near the beginning of the file.
1394  */
1395 static int	see_other_gids = 1;
1396 SYSCTL_INT(_security_bsd, OID_AUTO, see_other_gids, CTLFLAG_RW,
1397     &see_other_gids, 0,
1398     "Unprivileged processes may see subjects/objects with different real gid");
1399 
1400 /*
1401  * Determine if u1 can "see" the subject specified by u2, according to the
1402  * 'see_other_gids' policy.
1403  * Returns: 0 for permitted, ESRCH otherwise
1404  * Locks: none
1405  * References: *u1 and *u2 must not change during the call
1406  *             u1 may equal u2, in which case only one reference is required
1407  */
1408 static int
1409 cr_canseeothergids(struct ucred *u1, struct ucred *u2)
1410 {
1411 	if (!see_other_gids) {
1412 		if (realgroupmember(u1->cr_rgid, u2))
1413 			return (0);
1414 
1415 		for (int i = 1; i < u1->cr_ngroups; i++)
1416 			if (realgroupmember(u1->cr_groups[i], u2))
1417 				return (0);
1418 
1419 		if (priv_check_cred(u1, PRIV_SEEOTHERGIDS) != 0)
1420 			return (ESRCH);
1421 	}
1422 
1423 	return (0);
1424 }
1425 
1426 /*
1427  * 'see_jail_proc' determines whether or not visibility of processes and
1428  * sockets with credentials holding different jail ids is possible using a
1429  * variety of system MIBs.
1430  *
1431  * XXX: data declarations should be together near the beginning of the file.
1432  */
1433 
1434 static int	see_jail_proc = 1;
1435 SYSCTL_INT(_security_bsd, OID_AUTO, see_jail_proc, CTLFLAG_RW,
1436     &see_jail_proc, 0,
1437     "Unprivileged processes may see subjects/objects with different jail ids");
1438 
1439 /*-
1440  * Determine if u1 "can see" the subject specified by u2, according to the
1441  * 'see_jail_proc' policy.
1442  * Returns: 0 for permitted, ESRCH otherwise
1443  * Locks: none
1444  * References: *u1 and *u2 must not change during the call
1445  *             u1 may equal u2, in which case only one reference is required
1446  */
1447 static int
1448 cr_canseejailproc(struct ucred *u1, struct ucred *u2)
1449 {
1450 	if (see_jail_proc || /* Policy deactivated. */
1451 	    u1->cr_prison == u2->cr_prison || /* Same jail. */
1452 	    priv_check_cred(u1, PRIV_SEEJAILPROC) == 0) /* Privileged. */
1453 		return (0);
1454 
1455 	return (ESRCH);
1456 }
1457 
1458 /*
1459  * Helper for cr_cansee*() functions to abide by system-wide security.bsd.see_*
1460  * policies.  Determines if u1 "can see" u2 according to these policies.
1461  * Returns: 0 for permitted, ESRCH otherwise
1462  */
1463 int
1464 cr_bsd_visible(struct ucred *u1, struct ucred *u2)
1465 {
1466 	int error;
1467 
1468 	if ((error = cr_canseeotheruids(u1, u2)))
1469 		return (error);
1470 	if ((error = cr_canseeothergids(u1, u2)))
1471 		return (error);
1472 	if ((error = cr_canseejailproc(u1, u2)))
1473 		return (error);
1474 	return (0);
1475 }
1476 
1477 /*-
1478  * Determine if u1 "can see" the subject specified by u2.
1479  * Returns: 0 for permitted, an errno value otherwise
1480  * Locks: none
1481  * References: *u1 and *u2 must not change during the call
1482  *             u1 may equal u2, in which case only one reference is required
1483  */
1484 int
1485 cr_cansee(struct ucred *u1, struct ucred *u2)
1486 {
1487 	int error;
1488 
1489 	if ((error = prison_check(u1, u2)))
1490 		return (error);
1491 #ifdef MAC
1492 	if ((error = mac_cred_check_visible(u1, u2)))
1493 		return (error);
1494 #endif
1495 	if ((error = cr_bsd_visible(u1, u2)))
1496 		return (error);
1497 	return (0);
1498 }
1499 
1500 /*-
1501  * Determine if td "can see" the subject specified by p.
1502  * Returns: 0 for permitted, an errno value otherwise
1503  * Locks: Sufficient locks to protect p->p_ucred must be held.  td really
1504  *        should be curthread.
1505  * References: td and p must be valid for the lifetime of the call
1506  */
1507 int
1508 p_cansee(struct thread *td, struct proc *p)
1509 {
1510 	/* Wrap cr_cansee() for all functionality. */
1511 	KASSERT(td == curthread, ("%s: td not curthread", __func__));
1512 	PROC_LOCK_ASSERT(p, MA_OWNED);
1513 
1514 	if (td->td_proc == p)
1515 		return (0);
1516 	return (cr_cansee(td->td_ucred, p->p_ucred));
1517 }
1518 
1519 /*
1520  * 'conservative_signals' prevents the delivery of a broad class of
1521  * signals by unprivileged processes to processes that have changed their
1522  * credentials since the last invocation of execve().  This can prevent
1523  * the leakage of cached information or retained privileges as a result
1524  * of a common class of signal-related vulnerabilities.  However, this
1525  * may interfere with some applications that expect to be able to
1526  * deliver these signals to peer processes after having given up
1527  * privilege.
1528  */
1529 static int	conservative_signals = 1;
1530 SYSCTL_INT(_security_bsd, OID_AUTO, conservative_signals, CTLFLAG_RW,
1531     &conservative_signals, 0, "Unprivileged processes prevented from "
1532     "sending certain signals to processes whose credentials have changed");
1533 /*-
1534  * Determine whether cred may deliver the specified signal to proc.
1535  * Returns: 0 for permitted, an errno value otherwise.
1536  * Locks: A lock must be held for proc.
1537  * References: cred and proc must be valid for the lifetime of the call.
1538  */
1539 int
1540 cr_cansignal(struct ucred *cred, struct proc *proc, int signum)
1541 {
1542 	int error;
1543 
1544 	PROC_LOCK_ASSERT(proc, MA_OWNED);
1545 	/*
1546 	 * Jail semantics limit the scope of signalling to proc in the
1547 	 * same jail as cred, if cred is in jail.
1548 	 */
1549 	error = prison_check(cred, proc->p_ucred);
1550 	if (error)
1551 		return (error);
1552 #ifdef MAC
1553 	if ((error = mac_proc_check_signal(cred, proc, signum)))
1554 		return (error);
1555 #endif
1556 	if ((error = cr_bsd_visible(cred, proc->p_ucred)))
1557 		return (error);
1558 
1559 	/*
1560 	 * UNIX signal semantics depend on the status of the P_SUGID
1561 	 * bit on the target process.  If the bit is set, then additional
1562 	 * restrictions are placed on the set of available signals.
1563 	 */
1564 	if (conservative_signals && (proc->p_flag & P_SUGID)) {
1565 		switch (signum) {
1566 		case 0:
1567 		case SIGKILL:
1568 		case SIGINT:
1569 		case SIGTERM:
1570 		case SIGALRM:
1571 		case SIGSTOP:
1572 		case SIGTTIN:
1573 		case SIGTTOU:
1574 		case SIGTSTP:
1575 		case SIGHUP:
1576 		case SIGUSR1:
1577 		case SIGUSR2:
1578 			/*
1579 			 * Generally, permit job and terminal control
1580 			 * signals.
1581 			 */
1582 			break;
1583 		default:
1584 			/* Not permitted without privilege. */
1585 			error = priv_check_cred(cred, PRIV_SIGNAL_SUGID);
1586 			if (error)
1587 				return (error);
1588 		}
1589 	}
1590 
1591 	/*
1592 	 * Generally, the target credential's ruid or svuid must match the
1593 	 * subject credential's ruid or euid.
1594 	 */
1595 	if (cred->cr_ruid != proc->p_ucred->cr_ruid &&
1596 	    cred->cr_ruid != proc->p_ucred->cr_svuid &&
1597 	    cred->cr_uid != proc->p_ucred->cr_ruid &&
1598 	    cred->cr_uid != proc->p_ucred->cr_svuid) {
1599 		error = priv_check_cred(cred, PRIV_SIGNAL_DIFFCRED);
1600 		if (error)
1601 			return (error);
1602 	}
1603 
1604 	return (0);
1605 }
1606 
1607 /*-
1608  * Determine whether td may deliver the specified signal to p.
1609  * Returns: 0 for permitted, an errno value otherwise
1610  * Locks: Sufficient locks to protect various components of td and p
1611  *        must be held.  td must be curthread, and a lock must be
1612  *        held for p.
1613  * References: td and p must be valid for the lifetime of the call
1614  */
1615 int
1616 p_cansignal(struct thread *td, struct proc *p, int signum)
1617 {
1618 
1619 	KASSERT(td == curthread, ("%s: td not curthread", __func__));
1620 	PROC_LOCK_ASSERT(p, MA_OWNED);
1621 	if (td->td_proc == p)
1622 		return (0);
1623 
1624 	/*
1625 	 * UNIX signalling semantics require that processes in the same
1626 	 * session always be able to deliver SIGCONT to one another,
1627 	 * overriding the remaining protections.
1628 	 */
1629 	/* XXX: This will require an additional lock of some sort. */
1630 	if (signum == SIGCONT && td->td_proc->p_session == p->p_session)
1631 		return (0);
1632 	/*
1633 	 * Some compat layers use SIGTHR and higher signals for
1634 	 * communication between different kernel threads of the same
1635 	 * process, so that they expect that it's always possible to
1636 	 * deliver them, even for suid applications where cr_cansignal() can
1637 	 * deny such ability for security consideration.  It should be
1638 	 * pretty safe to do since the only way to create two processes
1639 	 * with the same p_leader is via rfork(2).
1640 	 */
1641 	if (td->td_proc->p_leader != NULL && signum >= SIGTHR &&
1642 	    signum < SIGTHR + 4 && td->td_proc->p_leader == p->p_leader)
1643 		return (0);
1644 
1645 	return (cr_cansignal(td->td_ucred, p, signum));
1646 }
1647 
1648 /*-
1649  * Determine whether td may reschedule p.
1650  * Returns: 0 for permitted, an errno value otherwise
1651  * Locks: Sufficient locks to protect various components of td and p
1652  *        must be held.  td must be curthread, and a lock must
1653  *        be held for p.
1654  * References: td and p must be valid for the lifetime of the call
1655  */
1656 int
1657 p_cansched(struct thread *td, struct proc *p)
1658 {
1659 	int error;
1660 
1661 	KASSERT(td == curthread, ("%s: td not curthread", __func__));
1662 	PROC_LOCK_ASSERT(p, MA_OWNED);
1663 	if (td->td_proc == p)
1664 		return (0);
1665 	if ((error = prison_check(td->td_ucred, p->p_ucred)))
1666 		return (error);
1667 #ifdef MAC
1668 	if ((error = mac_proc_check_sched(td->td_ucred, p)))
1669 		return (error);
1670 #endif
1671 	if ((error = cr_bsd_visible(td->td_ucred, p->p_ucred)))
1672 		return (error);
1673 
1674 	if (td->td_ucred->cr_ruid != p->p_ucred->cr_ruid &&
1675 	    td->td_ucred->cr_uid != p->p_ucred->cr_ruid) {
1676 		error = priv_check(td, PRIV_SCHED_DIFFCRED);
1677 		if (error)
1678 			return (error);
1679 	}
1680 	return (0);
1681 }
1682 
1683 /*
1684  * Handle getting or setting the prison's unprivileged_proc_debug
1685  * value.
1686  */
1687 static int
1688 sysctl_unprivileged_proc_debug(SYSCTL_HANDLER_ARGS)
1689 {
1690 	int error, val;
1691 
1692 	val = prison_allow(req->td->td_ucred, PR_ALLOW_UNPRIV_DEBUG);
1693 	error = sysctl_handle_int(oidp, &val, 0, req);
1694 	if (error != 0 || req->newptr == NULL)
1695 		return (error);
1696 	if (val != 0 && val != 1)
1697 		return (EINVAL);
1698 	prison_set_allow(req->td->td_ucred, PR_ALLOW_UNPRIV_DEBUG, val);
1699 	return (0);
1700 }
1701 
1702 /*
1703  * The 'unprivileged_proc_debug' flag may be used to disable a variety of
1704  * unprivileged inter-process debugging services, including some procfs
1705  * functionality, ptrace(), and ktrace().  In the past, inter-process
1706  * debugging has been involved in a variety of security problems, and sites
1707  * not requiring the service might choose to disable it when hardening
1708  * systems.
1709  */
1710 SYSCTL_PROC(_security_bsd, OID_AUTO, unprivileged_proc_debug,
1711     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_PRISON | CTLFLAG_SECURE |
1712     CTLFLAG_MPSAFE, 0, 0, sysctl_unprivileged_proc_debug, "I",
1713     "Unprivileged processes may use process debugging facilities");
1714 
1715 /*-
1716  * Determine whether td may debug p.
1717  * Returns: 0 for permitted, an errno value otherwise
1718  * Locks: Sufficient locks to protect various components of td and p
1719  *        must be held.  td must be curthread, and a lock must
1720  *        be held for p.
1721  * References: td and p must be valid for the lifetime of the call
1722  */
1723 int
1724 p_candebug(struct thread *td, struct proc *p)
1725 {
1726 	int error, grpsubset, i, uidsubset;
1727 
1728 	KASSERT(td == curthread, ("%s: td not curthread", __func__));
1729 	PROC_LOCK_ASSERT(p, MA_OWNED);
1730 	if (td->td_proc == p)
1731 		return (0);
1732 	if ((error = priv_check(td, PRIV_DEBUG_UNPRIV)))
1733 		return (error);
1734 	if ((error = prison_check(td->td_ucred, p->p_ucred)))
1735 		return (error);
1736 #ifdef MAC
1737 	if ((error = mac_proc_check_debug(td->td_ucred, p)))
1738 		return (error);
1739 #endif
1740 	if ((error = cr_bsd_visible(td->td_ucred, p->p_ucred)))
1741 		return (error);
1742 
1743 	/*
1744 	 * Is p's group set a subset of td's effective group set?  This
1745 	 * includes p's egid, group access list, rgid, and svgid.
1746 	 */
1747 	grpsubset = 1;
1748 	for (i = 0; i < p->p_ucred->cr_ngroups; i++) {
1749 		if (!groupmember(p->p_ucred->cr_groups[i], td->td_ucred)) {
1750 			grpsubset = 0;
1751 			break;
1752 		}
1753 	}
1754 	grpsubset = grpsubset &&
1755 	    groupmember(p->p_ucred->cr_rgid, td->td_ucred) &&
1756 	    groupmember(p->p_ucred->cr_svgid, td->td_ucred);
1757 
1758 	/*
1759 	 * Are the uids present in p's credential equal to td's
1760 	 * effective uid?  This includes p's euid, svuid, and ruid.
1761 	 */
1762 	uidsubset = (td->td_ucred->cr_uid == p->p_ucred->cr_uid &&
1763 	    td->td_ucred->cr_uid == p->p_ucred->cr_svuid &&
1764 	    td->td_ucred->cr_uid == p->p_ucred->cr_ruid);
1765 
1766 	/*
1767 	 * If p's gids aren't a subset, or the uids aren't a subset,
1768 	 * or the credential has changed, require appropriate privilege
1769 	 * for td to debug p.
1770 	 */
1771 	if (!grpsubset || !uidsubset) {
1772 		error = priv_check(td, PRIV_DEBUG_DIFFCRED);
1773 		if (error)
1774 			return (error);
1775 	}
1776 
1777 	/*
1778 	 * Has the credential of the process changed since the last exec()?
1779 	 */
1780 	if ((p->p_flag & P_SUGID) != 0) {
1781 		error = priv_check(td, PRIV_DEBUG_SUGID);
1782 		if (error)
1783 			return (error);
1784 	}
1785 
1786 	/* Can't trace init when securelevel > 0. */
1787 	if (p == initproc) {
1788 		error = securelevel_gt(td->td_ucred, 0);
1789 		if (error)
1790 			return (error);
1791 	}
1792 
1793 	/*
1794 	 * Can't trace a process that's currently exec'ing.
1795 	 *
1796 	 * XXX: Note, this is not a security policy decision, it's a
1797 	 * basic correctness/functionality decision.  Therefore, this check
1798 	 * should be moved to the caller's of p_candebug().
1799 	 */
1800 	if ((p->p_flag & P_INEXEC) != 0)
1801 		return (EBUSY);
1802 
1803 	/* Denied explicitly */
1804 	if ((p->p_flag2 & P2_NOTRACE) != 0) {
1805 		error = priv_check(td, PRIV_DEBUG_DENIED);
1806 		if (error != 0)
1807 			return (error);
1808 	}
1809 
1810 	return (0);
1811 }
1812 
1813 /*-
1814  * Determine whether the subject represented by cred can "see" a socket.
1815  * Returns: 0 for permitted, ENOENT otherwise.
1816  */
1817 int
1818 cr_canseesocket(struct ucred *cred, struct socket *so)
1819 {
1820 	int error;
1821 
1822 	error = prison_check(cred, so->so_cred);
1823 	if (error)
1824 		return (ENOENT);
1825 #ifdef MAC
1826 	error = mac_socket_check_visible(cred, so);
1827 	if (error)
1828 		return (error);
1829 #endif
1830 	if (cr_bsd_visible(cred, so->so_cred))
1831 		return (ENOENT);
1832 
1833 	return (0);
1834 }
1835 
1836 /*-
1837  * Determine whether td can wait for the exit of p.
1838  * Returns: 0 for permitted, an errno value otherwise
1839  * Locks: Sufficient locks to protect various components of td and p
1840  *        must be held.  td must be curthread, and a lock must
1841  *        be held for p.
1842  * References: td and p must be valid for the lifetime of the call
1843 
1844  */
1845 int
1846 p_canwait(struct thread *td, struct proc *p)
1847 {
1848 	int error;
1849 
1850 	KASSERT(td == curthread, ("%s: td not curthread", __func__));
1851 	PROC_LOCK_ASSERT(p, MA_OWNED);
1852 	if ((error = prison_check(td->td_ucred, p->p_ucred)))
1853 		return (error);
1854 #ifdef MAC
1855 	if ((error = mac_proc_check_wait(td->td_ucred, p)))
1856 		return (error);
1857 #endif
1858 #if 0
1859 	/* XXXMAC: This could have odd effects on some shells. */
1860 	if ((error = cr_bsd_visible(td->td_ucred, p->p_ucred)))
1861 		return (error);
1862 #endif
1863 
1864 	return (0);
1865 }
1866 
1867 /*
1868  * Credential management.
1869  *
1870  * struct ucred objects are rarely allocated but gain and lose references all
1871  * the time (e.g., on struct file alloc/dealloc) turning refcount updates into
1872  * a significant source of cache-line ping ponging. Common cases are worked
1873  * around by modifying thread-local counter instead if the cred to operate on
1874  * matches td_realucred.
1875  *
1876  * The counter is split into 2 parts:
1877  * - cr_users -- total count of all struct proc and struct thread objects
1878  *   which have given cred in p_ucred and td_ucred respectively
1879  * - cr_ref -- the actual ref count, only valid if cr_users == 0
1880  *
1881  * If users == 0 then cr_ref behaves similarly to refcount(9), in particular if
1882  * the count reaches 0 the object is freeable.
1883  * If users > 0 and curthread->td_realucred == cred, then updates are performed
1884  * against td_ucredref.
1885  * In other cases updates are performed against cr_ref.
1886  *
1887  * Changing td_realucred into something else decrements cr_users and transfers
1888  * accumulated updates.
1889  */
1890 struct ucred *
1891 crcowget(struct ucred *cr)
1892 {
1893 
1894 	mtx_lock(&cr->cr_mtx);
1895 	KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
1896 	    __func__, cr->cr_users, cr));
1897 	cr->cr_users++;
1898 	cr->cr_ref++;
1899 	mtx_unlock(&cr->cr_mtx);
1900 	return (cr);
1901 }
1902 
1903 static struct ucred *
1904 crunuse(struct thread *td)
1905 {
1906 	struct ucred *cr, *crold;
1907 
1908 	MPASS(td->td_realucred == td->td_ucred);
1909 	cr = td->td_realucred;
1910 	mtx_lock(&cr->cr_mtx);
1911 	cr->cr_ref += td->td_ucredref;
1912 	td->td_ucredref = 0;
1913 	KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
1914 	    __func__, cr->cr_users, cr));
1915 	cr->cr_users--;
1916 	if (cr->cr_users == 0) {
1917 		KASSERT(cr->cr_ref > 0, ("%s: ref %ld not > 0 on cred %p",
1918 		    __func__, cr->cr_ref, cr));
1919 		crold = cr;
1920 	} else {
1921 		cr->cr_ref--;
1922 		crold = NULL;
1923 	}
1924 	mtx_unlock(&cr->cr_mtx);
1925 	td->td_realucred = NULL;
1926 	return (crold);
1927 }
1928 
1929 static void
1930 crunusebatch(struct ucred *cr, int users, int ref)
1931 {
1932 
1933 	KASSERT(users > 0, ("%s: passed users %d not > 0 ; cred %p",
1934 	    __func__, users, cr));
1935 	mtx_lock(&cr->cr_mtx);
1936 	KASSERT(cr->cr_users >= users, ("%s: users %d not > %d on cred %p",
1937 	    __func__, cr->cr_users, users, cr));
1938 	cr->cr_users -= users;
1939 	cr->cr_ref += ref;
1940 	cr->cr_ref -= users;
1941 	if (cr->cr_users > 0) {
1942 		mtx_unlock(&cr->cr_mtx);
1943 		return;
1944 	}
1945 	KASSERT(cr->cr_ref >= 0, ("%s: ref %ld not >= 0 on cred %p",
1946 	    __func__, cr->cr_ref, cr));
1947 	if (cr->cr_ref > 0) {
1948 		mtx_unlock(&cr->cr_mtx);
1949 		return;
1950 	}
1951 	crfree_final(cr);
1952 }
1953 
1954 void
1955 crcowfree(struct thread *td)
1956 {
1957 	struct ucred *cr;
1958 
1959 	cr = crunuse(td);
1960 	if (cr != NULL)
1961 		crfree(cr);
1962 }
1963 
1964 struct ucred *
1965 crcowsync(void)
1966 {
1967 	struct thread *td;
1968 	struct proc *p;
1969 	struct ucred *crnew, *crold;
1970 
1971 	td = curthread;
1972 	p = td->td_proc;
1973 	PROC_LOCK_ASSERT(p, MA_OWNED);
1974 
1975 	MPASS(td->td_realucred == td->td_ucred);
1976 	if (td->td_realucred == p->p_ucred)
1977 		return (NULL);
1978 
1979 	crnew = crcowget(p->p_ucred);
1980 	crold = crunuse(td);
1981 	td->td_realucred = crnew;
1982 	td->td_ucred = td->td_realucred;
1983 	return (crold);
1984 }
1985 
1986 /*
1987  * Batching.
1988  */
1989 void
1990 credbatch_add(struct credbatch *crb, struct thread *td)
1991 {
1992 	struct ucred *cr;
1993 
1994 	MPASS(td->td_realucred != NULL);
1995 	MPASS(td->td_realucred == td->td_ucred);
1996 	MPASS(TD_GET_STATE(td) == TDS_INACTIVE);
1997 	cr = td->td_realucred;
1998 	KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
1999 	    __func__, cr->cr_users, cr));
2000 	if (crb->cred != cr) {
2001 		if (crb->users > 0) {
2002 			MPASS(crb->cred != NULL);
2003 			crunusebatch(crb->cred, crb->users, crb->ref);
2004 			crb->users = 0;
2005 			crb->ref = 0;
2006 		}
2007 	}
2008 	crb->cred = cr;
2009 	crb->users++;
2010 	crb->ref += td->td_ucredref;
2011 	td->td_ucredref = 0;
2012 	td->td_realucred = NULL;
2013 }
2014 
2015 void
2016 credbatch_final(struct credbatch *crb)
2017 {
2018 
2019 	MPASS(crb->cred != NULL);
2020 	MPASS(crb->users > 0);
2021 	crunusebatch(crb->cred, crb->users, crb->ref);
2022 }
2023 
2024 /*
2025  * Allocate a zeroed cred structure.
2026  */
2027 struct ucred *
2028 crget(void)
2029 {
2030 	struct ucred *cr;
2031 
2032 	cr = malloc(sizeof(*cr), M_CRED, M_WAITOK | M_ZERO);
2033 	mtx_init(&cr->cr_mtx, "cred", NULL, MTX_DEF);
2034 	cr->cr_ref = 1;
2035 #ifdef AUDIT
2036 	audit_cred_init(cr);
2037 #endif
2038 #ifdef MAC
2039 	mac_cred_init(cr);
2040 #endif
2041 	cr->cr_groups = cr->cr_smallgroups;
2042 	cr->cr_agroups =
2043 	    sizeof(cr->cr_smallgroups) / sizeof(cr->cr_smallgroups[0]);
2044 	return (cr);
2045 }
2046 
2047 /*
2048  * Claim another reference to a ucred structure.
2049  */
2050 struct ucred *
2051 crhold(struct ucred *cr)
2052 {
2053 	struct thread *td;
2054 
2055 	td = curthread;
2056 	if (__predict_true(td->td_realucred == cr)) {
2057 		KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
2058 		    __func__, cr->cr_users, cr));
2059 		td->td_ucredref++;
2060 		return (cr);
2061 	}
2062 	mtx_lock(&cr->cr_mtx);
2063 	cr->cr_ref++;
2064 	mtx_unlock(&cr->cr_mtx);
2065 	return (cr);
2066 }
2067 
2068 /*
2069  * Free a cred structure.  Throws away space when ref count gets to 0.
2070  */
2071 void
2072 crfree(struct ucred *cr)
2073 {
2074 	struct thread *td;
2075 
2076 	td = curthread;
2077 	if (__predict_true(td->td_realucred == cr)) {
2078 		KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
2079 		    __func__, cr->cr_users, cr));
2080 		td->td_ucredref--;
2081 		return;
2082 	}
2083 	mtx_lock(&cr->cr_mtx);
2084 	KASSERT(cr->cr_users >= 0, ("%s: users %d not >= 0 on cred %p",
2085 	    __func__, cr->cr_users, cr));
2086 	cr->cr_ref--;
2087 	if (cr->cr_users > 0) {
2088 		mtx_unlock(&cr->cr_mtx);
2089 		return;
2090 	}
2091 	KASSERT(cr->cr_ref >= 0, ("%s: ref %ld not >= 0 on cred %p",
2092 	    __func__, cr->cr_ref, cr));
2093 	if (cr->cr_ref > 0) {
2094 		mtx_unlock(&cr->cr_mtx);
2095 		return;
2096 	}
2097 	crfree_final(cr);
2098 }
2099 
2100 static void
2101 crfree_final(struct ucred *cr)
2102 {
2103 
2104 	KASSERT(cr->cr_users == 0, ("%s: users %d not == 0 on cred %p",
2105 	    __func__, cr->cr_users, cr));
2106 	KASSERT(cr->cr_ref == 0, ("%s: ref %ld not == 0 on cred %p",
2107 	    __func__, cr->cr_ref, cr));
2108 
2109 	/*
2110 	 * Some callers of crget(), such as nfs_statfs(), allocate a temporary
2111 	 * credential, but don't allocate a uidinfo structure.
2112 	 */
2113 	if (cr->cr_uidinfo != NULL)
2114 		uifree(cr->cr_uidinfo);
2115 	if (cr->cr_ruidinfo != NULL)
2116 		uifree(cr->cr_ruidinfo);
2117 	if (cr->cr_prison != NULL)
2118 		prison_free(cr->cr_prison);
2119 	if (cr->cr_loginclass != NULL)
2120 		loginclass_free(cr->cr_loginclass);
2121 #ifdef AUDIT
2122 	audit_cred_destroy(cr);
2123 #endif
2124 #ifdef MAC
2125 	mac_cred_destroy(cr);
2126 #endif
2127 	mtx_destroy(&cr->cr_mtx);
2128 	if (cr->cr_groups != cr->cr_smallgroups)
2129 		free(cr->cr_groups, M_CRED);
2130 	free(cr, M_CRED);
2131 }
2132 
2133 /*
2134  * Copy a ucred's contents from a template.  Does not block.
2135  */
2136 void
2137 crcopy(struct ucred *dest, struct ucred *src)
2138 {
2139 
2140 	KASSERT(dest->cr_ref == 1, ("crcopy of shared ucred"));
2141 	bcopy(&src->cr_startcopy, &dest->cr_startcopy,
2142 	    (unsigned)((caddr_t)&src->cr_endcopy -
2143 		(caddr_t)&src->cr_startcopy));
2144 	dest->cr_flags = src->cr_flags;
2145 	crsetgroups(dest, src->cr_ngroups, src->cr_groups);
2146 	uihold(dest->cr_uidinfo);
2147 	uihold(dest->cr_ruidinfo);
2148 	prison_hold(dest->cr_prison);
2149 	loginclass_hold(dest->cr_loginclass);
2150 #ifdef AUDIT
2151 	audit_cred_copy(src, dest);
2152 #endif
2153 #ifdef MAC
2154 	mac_cred_copy(src, dest);
2155 #endif
2156 }
2157 
2158 /*
2159  * Dup cred struct to a new held one.
2160  */
2161 struct ucred *
2162 crdup(struct ucred *cr)
2163 {
2164 	struct ucred *newcr;
2165 
2166 	newcr = crget();
2167 	crcopy(newcr, cr);
2168 	return (newcr);
2169 }
2170 
2171 /*
2172  * Fill in a struct xucred based on a struct ucred.
2173  */
2174 void
2175 cru2x(struct ucred *cr, struct xucred *xcr)
2176 {
2177 	int ngroups;
2178 
2179 	bzero(xcr, sizeof(*xcr));
2180 	xcr->cr_version = XUCRED_VERSION;
2181 	xcr->cr_uid = cr->cr_uid;
2182 
2183 	ngroups = MIN(cr->cr_ngroups, XU_NGROUPS);
2184 	xcr->cr_ngroups = ngroups;
2185 	bcopy(cr->cr_groups, xcr->cr_groups,
2186 	    ngroups * sizeof(*cr->cr_groups));
2187 }
2188 
2189 void
2190 cru2xt(struct thread *td, struct xucred *xcr)
2191 {
2192 
2193 	cru2x(td->td_ucred, xcr);
2194 	xcr->cr_pid = td->td_proc->p_pid;
2195 }
2196 
2197 /*
2198  * Set initial process credentials.
2199  * Callers are responsible for providing the reference for provided credentials.
2200  */
2201 void
2202 proc_set_cred_init(struct proc *p, struct ucred *newcred)
2203 {
2204 
2205 	p->p_ucred = crcowget(newcred);
2206 }
2207 
2208 /*
2209  * Change process credentials.
2210  * Callers are responsible for providing the reference for passed credentials
2211  * and for freeing old ones.
2212  *
2213  * Process has to be locked except when it does not have credentials (as it
2214  * should not be visible just yet) or when newcred is NULL (as this can be
2215  * only used when the process is about to be freed, at which point it should
2216  * not be visible anymore).
2217  */
2218 void
2219 proc_set_cred(struct proc *p, struct ucred *newcred)
2220 {
2221 	struct ucred *cr;
2222 
2223 	cr = p->p_ucred;
2224 	MPASS(cr != NULL);
2225 	PROC_LOCK_ASSERT(p, MA_OWNED);
2226 	KASSERT(newcred->cr_users == 0, ("%s: users %d not 0 on cred %p",
2227 	    __func__, newcred->cr_users, newcred));
2228 	mtx_lock(&cr->cr_mtx);
2229 	KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
2230 	    __func__, cr->cr_users, cr));
2231 	cr->cr_users--;
2232 	mtx_unlock(&cr->cr_mtx);
2233 	p->p_ucred = newcred;
2234 	newcred->cr_users = 1;
2235 	PROC_UPDATE_COW(p);
2236 }
2237 
2238 void
2239 proc_unset_cred(struct proc *p)
2240 {
2241 	struct ucred *cr;
2242 
2243 	MPASS(p->p_state == PRS_ZOMBIE || p->p_state == PRS_NEW);
2244 	cr = p->p_ucred;
2245 	p->p_ucred = NULL;
2246 	KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
2247 	    __func__, cr->cr_users, cr));
2248 	mtx_lock(&cr->cr_mtx);
2249 	cr->cr_users--;
2250 	if (cr->cr_users == 0)
2251 		KASSERT(cr->cr_ref > 0, ("%s: ref %ld not > 0 on cred %p",
2252 		    __func__, cr->cr_ref, cr));
2253 	mtx_unlock(&cr->cr_mtx);
2254 	crfree(cr);
2255 }
2256 
2257 struct ucred *
2258 crcopysafe(struct proc *p, struct ucred *cr)
2259 {
2260 	struct ucred *oldcred;
2261 	int groups;
2262 
2263 	PROC_LOCK_ASSERT(p, MA_OWNED);
2264 
2265 	oldcred = p->p_ucred;
2266 	while (cr->cr_agroups < oldcred->cr_agroups) {
2267 		groups = oldcred->cr_agroups;
2268 		PROC_UNLOCK(p);
2269 		crextend(cr, groups);
2270 		PROC_LOCK(p);
2271 		oldcred = p->p_ucred;
2272 	}
2273 	crcopy(cr, oldcred);
2274 
2275 	return (oldcred);
2276 }
2277 
2278 /*
2279  * Extend the passed in credential to hold n items.
2280  */
2281 void
2282 crextend(struct ucred *cr, int n)
2283 {
2284 	int cnt;
2285 
2286 	/* Truncate? */
2287 	if (n <= cr->cr_agroups)
2288 		return;
2289 
2290 	/*
2291 	 * We extend by 2 each time since we're using a power of two
2292 	 * allocator until we need enough groups to fill a page.
2293 	 * Once we're allocating multiple pages, only allocate as many
2294 	 * as we actually need.  The case of processes needing a
2295 	 * non-power of two number of pages seems more likely than
2296 	 * a real world process that adds thousands of groups one at a
2297 	 * time.
2298 	 */
2299 	if ( n < PAGE_SIZE / sizeof(gid_t) ) {
2300 		if (cr->cr_agroups == 0)
2301 			cnt = MAX(1, MINALLOCSIZE / sizeof(gid_t));
2302 		else
2303 			cnt = cr->cr_agroups * 2;
2304 
2305 		while (cnt < n)
2306 			cnt *= 2;
2307 	} else
2308 		cnt = roundup2(n, PAGE_SIZE / sizeof(gid_t));
2309 
2310 	/* Free the old array. */
2311 	if (cr->cr_groups != cr->cr_smallgroups)
2312 		free(cr->cr_groups, M_CRED);
2313 
2314 	cr->cr_groups = malloc(cnt * sizeof(gid_t), M_CRED, M_WAITOK | M_ZERO);
2315 	cr->cr_agroups = cnt;
2316 }
2317 
2318 /*
2319  * Copy groups in to a credential, preserving any necessary invariants.
2320  * Currently this includes the sorting of all supplemental gids.
2321  * crextend() must have been called before hand to ensure sufficient
2322  * space is available.
2323  */
2324 static void
2325 crsetgroups_locked(struct ucred *cr, int ngrp, gid_t *groups)
2326 {
2327 	int i;
2328 	int j;
2329 	gid_t g;
2330 
2331 	KASSERT(cr->cr_agroups >= ngrp, ("cr_ngroups is too small"));
2332 
2333 	bcopy(groups, cr->cr_groups, ngrp * sizeof(gid_t));
2334 	cr->cr_ngroups = ngrp;
2335 
2336 	/*
2337 	 * Sort all groups except cr_groups[0] to allow groupmember to
2338 	 * perform a binary search.
2339 	 *
2340 	 * XXX: If large numbers of groups become common this should
2341 	 * be replaced with shell sort like linux uses or possibly
2342 	 * heap sort.
2343 	 */
2344 	for (i = 2; i < ngrp; i++) {
2345 		g = cr->cr_groups[i];
2346 		for (j = i-1; j >= 1 && g < cr->cr_groups[j]; j--)
2347 			cr->cr_groups[j + 1] = cr->cr_groups[j];
2348 		cr->cr_groups[j + 1] = g;
2349 	}
2350 }
2351 
2352 /*
2353  * Copy groups in to a credential after expanding it if required.
2354  * Truncate the list to (ngroups_max + 1) if it is too large.
2355  */
2356 void
2357 crsetgroups(struct ucred *cr, int ngrp, gid_t *groups)
2358 {
2359 
2360 	if (ngrp > ngroups_max + 1)
2361 		ngrp = ngroups_max + 1;
2362 
2363 	crextend(cr, ngrp);
2364 	crsetgroups_locked(cr, ngrp, groups);
2365 }
2366 
2367 /*
2368  * Get login name, if available.
2369  */
2370 #ifndef _SYS_SYSPROTO_H_
2371 struct getlogin_args {
2372 	char	*namebuf;
2373 	u_int	namelen;
2374 };
2375 #endif
2376 /* ARGSUSED */
2377 int
2378 sys_getlogin(struct thread *td, struct getlogin_args *uap)
2379 {
2380 	char login[MAXLOGNAME];
2381 	struct proc *p = td->td_proc;
2382 	size_t len;
2383 
2384 	if (uap->namelen > MAXLOGNAME)
2385 		uap->namelen = MAXLOGNAME;
2386 	PROC_LOCK(p);
2387 	SESS_LOCK(p->p_session);
2388 	len = strlcpy(login, p->p_session->s_login, uap->namelen) + 1;
2389 	SESS_UNLOCK(p->p_session);
2390 	PROC_UNLOCK(p);
2391 	if (len > uap->namelen)
2392 		return (ERANGE);
2393 	return (copyout(login, uap->namebuf, len));
2394 }
2395 
2396 /*
2397  * Set login name.
2398  */
2399 #ifndef _SYS_SYSPROTO_H_
2400 struct setlogin_args {
2401 	char	*namebuf;
2402 };
2403 #endif
2404 /* ARGSUSED */
2405 int
2406 sys_setlogin(struct thread *td, struct setlogin_args *uap)
2407 {
2408 	struct proc *p = td->td_proc;
2409 	int error;
2410 	char logintmp[MAXLOGNAME];
2411 
2412 	CTASSERT(sizeof(p->p_session->s_login) >= sizeof(logintmp));
2413 
2414 	error = priv_check(td, PRIV_PROC_SETLOGIN);
2415 	if (error)
2416 		return (error);
2417 	error = copyinstr(uap->namebuf, logintmp, sizeof(logintmp), NULL);
2418 	if (error != 0) {
2419 		if (error == ENAMETOOLONG)
2420 			error = EINVAL;
2421 		return (error);
2422 	}
2423 	AUDIT_ARG_LOGIN(logintmp);
2424 	PROC_LOCK(p);
2425 	SESS_LOCK(p->p_session);
2426 	strcpy(p->p_session->s_login, logintmp);
2427 	SESS_UNLOCK(p->p_session);
2428 	PROC_UNLOCK(p);
2429 	return (0);
2430 }
2431 
2432 void
2433 setsugid(struct proc *p)
2434 {
2435 
2436 	PROC_LOCK_ASSERT(p, MA_OWNED);
2437 	p->p_flag |= P_SUGID;
2438 }
2439 
2440 /*-
2441  * Change a process's effective uid.
2442  * Side effects: newcred->cr_uid and newcred->cr_uidinfo will be modified.
2443  * References: newcred must be an exclusive credential reference for the
2444  *             duration of the call.
2445  */
2446 void
2447 change_euid(struct ucred *newcred, struct uidinfo *euip)
2448 {
2449 
2450 	newcred->cr_uid = euip->ui_uid;
2451 	uihold(euip);
2452 	uifree(newcred->cr_uidinfo);
2453 	newcred->cr_uidinfo = euip;
2454 }
2455 
2456 /*-
2457  * Change a process's effective gid.
2458  * Side effects: newcred->cr_gid will be modified.
2459  * References: newcred must be an exclusive credential reference for the
2460  *             duration of the call.
2461  */
2462 void
2463 change_egid(struct ucred *newcred, gid_t egid)
2464 {
2465 
2466 	newcred->cr_groups[0] = egid;
2467 }
2468 
2469 /*-
2470  * Change a process's real uid.
2471  * Side effects: newcred->cr_ruid will be updated, newcred->cr_ruidinfo
2472  *               will be updated, and the old and new cr_ruidinfo proc
2473  *               counts will be updated.
2474  * References: newcred must be an exclusive credential reference for the
2475  *             duration of the call.
2476  */
2477 void
2478 change_ruid(struct ucred *newcred, struct uidinfo *ruip)
2479 {
2480 
2481 	(void)chgproccnt(newcred->cr_ruidinfo, -1, 0);
2482 	newcred->cr_ruid = ruip->ui_uid;
2483 	uihold(ruip);
2484 	uifree(newcred->cr_ruidinfo);
2485 	newcred->cr_ruidinfo = ruip;
2486 	(void)chgproccnt(newcred->cr_ruidinfo, 1, 0);
2487 }
2488 
2489 /*-
2490  * Change a process's real gid.
2491  * Side effects: newcred->cr_rgid will be updated.
2492  * References: newcred must be an exclusive credential reference for the
2493  *             duration of the call.
2494  */
2495 void
2496 change_rgid(struct ucred *newcred, gid_t rgid)
2497 {
2498 
2499 	newcred->cr_rgid = rgid;
2500 }
2501 
2502 /*-
2503  * Change a process's saved uid.
2504  * Side effects: newcred->cr_svuid will be updated.
2505  * References: newcred must be an exclusive credential reference for the
2506  *             duration of the call.
2507  */
2508 void
2509 change_svuid(struct ucred *newcred, uid_t svuid)
2510 {
2511 
2512 	newcred->cr_svuid = svuid;
2513 }
2514 
2515 /*-
2516  * Change a process's saved gid.
2517  * Side effects: newcred->cr_svgid will be updated.
2518  * References: newcred must be an exclusive credential reference for the
2519  *             duration of the call.
2520  */
2521 void
2522 change_svgid(struct ucred *newcred, gid_t svgid)
2523 {
2524 
2525 	newcred->cr_svgid = svgid;
2526 }
2527 
2528 bool allow_ptrace = true;
2529 SYSCTL_BOOL(_security_bsd, OID_AUTO, allow_ptrace, CTLFLAG_RWTUN,
2530     &allow_ptrace, 0,
2531     "Deny ptrace(2) use by returning ENOSYS");
2532