1/*	$NetBSD: kern_prot.c,v 1.122 2020/05/23 23:42:43 ad Exp $	*/
2
3/*
4 * Copyright (c) 1982, 1986, 1989, 1990, 1991, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
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. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 *	@(#)kern_prot.c	8.9 (Berkeley) 2/14/95
37 */
38
39/*
40 * System calls related to processes and protection
41 */
42
43#include <sys/cdefs.h>
44__KERNEL_RCSID(0, "$NetBSD: kern_prot.c,v 1.122 2020/05/23 23:42:43 ad Exp $");
45
46#ifdef _KERNEL_OPT
47#include "opt_compat_43.h"
48#endif
49
50#include <sys/param.h>
51#include <sys/acct.h>
52#include <sys/systm.h>
53#include <sys/ucred.h>
54#include <sys/proc.h>
55#include <sys/timeb.h>
56#include <sys/times.h>
57#include <sys/pool.h>
58#include <sys/prot.h>
59#include <sys/syslog.h>
60#include <sys/uidinfo.h>
61#include <sys/kauth.h>
62
63#include <sys/mount.h>
64#include <sys/syscallargs.h>
65
66int	sys_getpid(struct lwp *, const void *, register_t *);
67int	sys_getpid_with_ppid(struct lwp *, const void *, register_t *);
68int	sys_getuid(struct lwp *, const void *, register_t *);
69int	sys_getuid_with_euid(struct lwp *, const void *, register_t *);
70int	sys_getgid(struct lwp *, const void *, register_t *);
71int	sys_getgid_with_egid(struct lwp *, const void *, register_t *);
72
73/* ARGSUSED */
74int
75sys_getpid(struct lwp *l, const void *v, register_t *retval)
76{
77	struct proc *p = l->l_proc;
78
79	*retval = p->p_pid;
80	return (0);
81}
82
83/* ARGSUSED */
84int
85sys_getpid_with_ppid(struct lwp *l, const void *v, register_t *retval)
86{
87	struct proc *p = l->l_proc;
88
89	retval[0] = p->p_pid;
90	retval[1] = p->p_ppid;
91	return (0);
92}
93
94/* ARGSUSED */
95int
96sys_getppid(struct lwp *l, const void *v, register_t *retval)
97{
98	struct proc *p = l->l_proc;
99
100	*retval = p->p_ppid;
101	return (0);
102}
103
104/* Get process group ID; note that POSIX getpgrp takes no parameter */
105int
106sys_getpgrp(struct lwp *l, const void *v, register_t *retval)
107{
108	struct proc *p = l->l_proc;
109
110	mutex_enter(&proc_lock);
111	*retval = p->p_pgrp->pg_id;
112	mutex_exit(&proc_lock);
113	return (0);
114}
115
116/*
117 * Return the process group ID of the session leader (session ID)
118 * for the specified process.
119 */
120int
121sys_getsid(struct lwp *l, const struct sys_getsid_args *uap, register_t *retval)
122{
123	/* {
124		syscalldarg(pid_t) pid;
125	} */
126	pid_t pid = SCARG(uap, pid);
127	struct proc *p;
128	int error = 0;
129
130	mutex_enter(&proc_lock);
131	if (pid == 0)
132		*retval = l->l_proc->p_session->s_sid;
133	else if ((p = proc_find(pid)) != NULL)
134		*retval = p->p_session->s_sid;
135	else
136		error = ESRCH;
137	mutex_exit(&proc_lock);
138
139	return error;
140}
141
142int
143sys_getpgid(struct lwp *l, const struct sys_getpgid_args *uap, register_t *retval)
144{
145	/* {
146		syscallarg(pid_t) pid;
147	} */
148	pid_t pid = SCARG(uap, pid);
149	struct proc *p;
150	int error = 0;
151
152	mutex_enter(&proc_lock);
153	if (pid == 0)
154		*retval = l->l_proc->p_pgid;
155	else if ((p = proc_find(pid)) != NULL)
156		*retval = p->p_pgid;
157	else
158		error = ESRCH;
159	mutex_exit(&proc_lock);
160
161	return error;
162}
163
164/* ARGSUSED */
165int
166sys_getuid(struct lwp *l, const void *v, register_t *retval)
167{
168
169	*retval = kauth_cred_getuid(l->l_cred);
170	return (0);
171}
172
173/* ARGSUSED */
174int
175sys_getuid_with_euid(struct lwp *l, const void *v, register_t *retval)
176{
177
178	retval[0] = kauth_cred_getuid(l->l_cred);
179	retval[1] = kauth_cred_geteuid(l->l_cred);
180	return (0);
181}
182
183/* ARGSUSED */
184int
185sys_geteuid(struct lwp *l, const void *v, register_t *retval)
186{
187
188	*retval = kauth_cred_geteuid(l->l_cred);
189	return (0);
190}
191
192/* ARGSUSED */
193int
194sys_getgid(struct lwp *l, const void *v, register_t *retval)
195{
196
197	*retval = kauth_cred_getgid(l->l_cred);
198	return (0);
199}
200
201/* ARGSUSED */
202int
203sys_getgid_with_egid(struct lwp *l, const void *v, register_t *retval)
204{
205
206	retval[0] = kauth_cred_getgid(l->l_cred);
207	retval[1] = kauth_cred_getegid(l->l_cred);
208	return (0);
209}
210
211/*
212 * Get effective group ID.  The "egid" is groups[0], and could be obtained
213 * via getgroups.  This syscall exists because it is somewhat painful to do
214 * correctly in a library function.
215 */
216/* ARGSUSED */
217int
218sys_getegid(struct lwp *l, const void *v, register_t *retval)
219{
220
221	*retval = kauth_cred_getegid(l->l_cred);
222	return (0);
223}
224
225int
226sys_getgroups(struct lwp *l, const struct sys_getgroups_args *uap, register_t *retval)
227{
228	/* {
229		syscallarg(int) gidsetsize;
230		syscallarg(gid_t *) gidset;
231	} */
232
233	*retval = kauth_cred_ngroups(l->l_cred);
234	if (SCARG(uap, gidsetsize) == 0)
235		return 0;
236	if (SCARG(uap, gidsetsize) < (int)*retval)
237		return EINVAL;
238
239	return kauth_cred_getgroups(l->l_cred, SCARG(uap, gidset), *retval,
240	    UIO_USERSPACE);
241}
242
243int
244sys_setsid(struct lwp *l, const void *v, register_t *retval)
245{
246	struct proc *p = l->l_proc;
247	int error;
248
249	error = proc_enterpgrp(p, p->p_pid, p->p_pid, true);
250	*retval = p->p_pid;
251	return (error);
252}
253
254
255/*
256 * set process group (setpgid/old setpgrp)
257 *
258 * caller does setpgid(targpid, targpgid)
259 *
260 * pgid must be in valid range (EINVAL)
261 * pid must be caller or child of caller (ESRCH)
262 * if a child
263 *	pid must be in same session (EPERM)
264 *	pid can't have done an exec (EACCES)
265 * if pgid != pid
266 * 	there must exist some pid in same session having pgid (EPERM)
267 * pid must not be session leader (EPERM)
268 *
269 * Permission checks now in proc_enterpgrp()
270 */
271int
272sys_setpgid(struct lwp *l, const struct sys_setpgid_args *uap,
273    register_t *retval)
274{
275	/* {
276		syscallarg(int) pid;
277		syscallarg(int) pgid;
278	} */
279	struct proc *p = l->l_proc;
280	pid_t targp, pgid;
281
282	if (SCARG(uap, pgid) < 0)
283		return EINVAL;
284	if ((targp = SCARG(uap, pid)) == 0)
285		targp = p->p_pid;
286	if ((pgid = SCARG(uap, pgid)) == 0)
287		pgid = targp;
288
289	return proc_enterpgrp(p, targp, pgid, false);
290}
291
292/*
293 * Set real, effective and saved uids to the requested values.
294 * non-root callers can only ever change uids to values that match
295 * one of the processes current uid values.
296 * This is further restricted by the flags argument.
297 */
298
299int
300do_setresuid(struct lwp *l, uid_t r, uid_t e, uid_t sv, u_int flags)
301{
302	struct proc *p = l->l_proc;
303	kauth_cred_t cred, ncred;
304
305	ncred = kauth_cred_alloc();
306
307	/* Get a write lock on the process credential. */
308	proc_crmod_enter();
309	cred = p->p_cred;
310
311	/*
312	 * Check that the new value is one of the allowed existing values,
313	 * or that we have root privilege.
314	 */
315	if ((r != -1
316	    && !((flags & ID_R_EQ_R) && r == kauth_cred_getuid(cred))
317	    && !((flags & ID_R_EQ_E) && r == kauth_cred_geteuid(cred))
318	    && !((flags & ID_R_EQ_S) && r == kauth_cred_getsvuid(cred))) ||
319	    (e != -1
320	    && !((flags & ID_E_EQ_R) && e == kauth_cred_getuid(cred))
321	    && !((flags & ID_E_EQ_E) && e == kauth_cred_geteuid(cred))
322	    && !((flags & ID_E_EQ_S) && e == kauth_cred_getsvuid(cred))) ||
323	    (sv != -1
324	    && !((flags & ID_S_EQ_R) && sv == kauth_cred_getuid(cred))
325	    && !((flags & ID_S_EQ_E) && sv == kauth_cred_geteuid(cred))
326	    && !((flags & ID_S_EQ_S) && sv == kauth_cred_getsvuid(cred)))) {
327		int error;
328
329		error = kauth_authorize_process(cred, KAUTH_PROCESS_SETID,
330		    p, NULL, NULL, NULL);
331		if (error != 0) {
332		 	proc_crmod_leave(cred, ncred, false);
333			return error;
334		}
335	}
336
337	/* If nothing has changed, short circuit the request */
338	if ((r == -1 || r == kauth_cred_getuid(cred))
339	    && (e == -1 || e == kauth_cred_geteuid(cred))
340	    && (sv == -1 || sv == kauth_cred_getsvuid(cred))) {
341		proc_crmod_leave(cred, ncred, false);
342		return 0;
343	}
344
345	kauth_cred_clone(cred, ncred);
346
347	if (r != -1 && r != kauth_cred_getuid(ncred)) {
348		u_long nlwps;
349
350		/* Update count of processes for this user. */
351		(void)chgproccnt(kauth_cred_getuid(ncred), -1);
352		(void)chgproccnt(r, 1);
353
354		/* The first LWP of a process is excluded. */
355		KASSERT(mutex_owned(p->p_lock));
356		nlwps = p->p_nlwps - 1;
357		(void)chglwpcnt(kauth_cred_getuid(ncred), -nlwps);
358		(void)chglwpcnt(r, nlwps);
359
360		kauth_cred_setuid(ncred, r);
361	}
362	if (sv != -1)
363		kauth_cred_setsvuid(ncred, sv);
364	if (e != -1)
365		kauth_cred_seteuid(ncred, e);
366
367	/* Broadcast our credentials to the process and other LWPs. */
368 	proc_crmod_leave(ncred, cred, true);
369
370	return 0;
371}
372
373/*
374 * Set real, effective and saved gids to the requested values.
375 * non-root callers can only ever change gids to values that match
376 * one of the processes current gid values.
377 * This is further restricted by the flags argument.
378 */
379
380int
381do_setresgid(struct lwp *l, gid_t r, gid_t e, gid_t sv, u_int flags)
382{
383	struct proc *p = l->l_proc;
384	kauth_cred_t cred, ncred;
385
386	ncred = kauth_cred_alloc();
387
388	/* Get a write lock on the process credential. */
389	proc_crmod_enter();
390	cred = p->p_cred;
391
392	/*
393	 * check new value is one of the allowed existing values.
394	 * otherwise, check if we have root privilege.
395	 */
396	if ((r != -1
397	    && !((flags & ID_R_EQ_R) && r == kauth_cred_getgid(cred))
398	    && !((flags & ID_R_EQ_E) && r == kauth_cred_getegid(cred))
399	    && !((flags & ID_R_EQ_S) && r == kauth_cred_getsvgid(cred))) ||
400	    (e != -1
401	    && !((flags & ID_E_EQ_R) && e == kauth_cred_getgid(cred))
402	    && !((flags & ID_E_EQ_E) && e == kauth_cred_getegid(cred))
403	    && !((flags & ID_E_EQ_S) && e == kauth_cred_getsvgid(cred))) ||
404	    (sv != -1
405	    && !((flags & ID_S_EQ_R) && sv == kauth_cred_getgid(cred))
406	    && !((flags & ID_S_EQ_E) && sv == kauth_cred_getegid(cred))
407	    && !((flags & ID_S_EQ_S) && sv == kauth_cred_getsvgid(cred)))) {
408		int error;
409
410		error = kauth_authorize_process(cred, KAUTH_PROCESS_SETID,
411		    p, NULL, NULL, NULL);
412		if (error != 0) {
413		 	proc_crmod_leave(cred, ncred, false);
414			return error;
415		}
416	}
417
418	/* If nothing has changed, short circuit the request */
419	if ((r == -1 || r == kauth_cred_getgid(cred))
420	    && (e == -1 || e == kauth_cred_getegid(cred))
421	    && (sv == -1 || sv == kauth_cred_getsvgid(cred))) {
422	 	proc_crmod_leave(cred, ncred, false);
423		return 0;
424	}
425
426	kauth_cred_clone(cred, ncred);
427
428	if (r != -1)
429		kauth_cred_setgid(ncred, r);
430	if (sv != -1)
431		kauth_cred_setsvgid(ncred, sv);
432	if (e != -1)
433		kauth_cred_setegid(ncred, e);
434
435	/* Broadcast our credentials to the process and other LWPs. */
436 	proc_crmod_leave(ncred, cred, true);
437
438	return 0;
439}
440
441/* ARGSUSED */
442int
443sys_setuid(struct lwp *l, const struct sys_setuid_args *uap, register_t *retval)
444{
445	/* {
446		syscallarg(uid_t) uid;
447	} */
448	uid_t uid = SCARG(uap, uid);
449
450	return do_setresuid(l, uid, uid, uid,
451			    ID_R_EQ_R | ID_E_EQ_R | ID_S_EQ_R);
452}
453
454/* ARGSUSED */
455int
456sys_seteuid(struct lwp *l, const struct sys_seteuid_args *uap, register_t *retval)
457{
458	/* {
459		syscallarg(uid_t) euid;
460	} */
461
462	return do_setresuid(l, -1, SCARG(uap, euid), -1, ID_E_EQ_R | ID_E_EQ_S);
463}
464
465int
466sys_setreuid(struct lwp *l, const struct sys_setreuid_args *uap, register_t *retval)
467{
468	/* {
469		syscallarg(uid_t) ruid;
470		syscallarg(uid_t) euid;
471	} */
472	kauth_cred_t cred = l->l_cred;
473	uid_t ruid, euid, svuid;
474
475	ruid = SCARG(uap, ruid);
476	euid = SCARG(uap, euid);
477
478	if (ruid == -1)
479		ruid = kauth_cred_getuid(cred);
480	if (euid == -1)
481		euid = kauth_cred_geteuid(cred);
482
483	/* Saved uid is set to the new euid if the ruid changed */
484	svuid = (ruid == kauth_cred_getuid(cred)) ? -1 : euid;
485
486	return do_setresuid(l, ruid, euid, svuid,
487			    ID_R_EQ_R | ID_R_EQ_E |
488			    ID_E_EQ_R | ID_E_EQ_E | ID_E_EQ_S |
489			    ID_S_EQ_R | ID_S_EQ_E | ID_S_EQ_S);
490}
491
492/* ARGSUSED */
493int
494sys_setgid(struct lwp *l, const struct sys_setgid_args *uap, register_t *retval)
495{
496	/* {
497		syscallarg(gid_t) gid;
498	} */
499	gid_t gid = SCARG(uap, gid);
500
501	return do_setresgid(l, gid, gid, gid,
502			    ID_R_EQ_R | ID_E_EQ_R | ID_S_EQ_R);
503}
504
505/* ARGSUSED */
506int
507sys_setegid(struct lwp *l, const struct sys_setegid_args *uap, register_t *retval)
508{
509	/* {
510		syscallarg(gid_t) egid;
511	} */
512
513	return do_setresgid(l, -1, SCARG(uap, egid), -1, ID_E_EQ_R | ID_E_EQ_S);
514}
515
516int
517sys_setregid(struct lwp *l, const struct sys_setregid_args *uap, register_t *retval)
518{
519	/* {
520		syscallarg(gid_t) rgid;
521		syscallarg(gid_t) egid;
522	} */
523	kauth_cred_t cred = l->l_cred;
524	gid_t rgid, egid, svgid;
525
526	rgid = SCARG(uap, rgid);
527	egid = SCARG(uap, egid);
528
529	if (rgid == -1)
530		rgid = kauth_cred_getgid(cred);
531	if (egid == -1)
532		egid = kauth_cred_getegid(cred);
533
534	/* Saved gid is set to the new egid if the rgid changed */
535	svgid = rgid == kauth_cred_getgid(cred) ? -1 : egid;
536
537	return do_setresgid(l, rgid, egid, svgid,
538			ID_R_EQ_R | ID_R_EQ_E |
539			ID_E_EQ_R | ID_E_EQ_E | ID_E_EQ_S |
540			ID_S_EQ_R | ID_S_EQ_E | ID_S_EQ_S);
541}
542
543int
544sys_issetugid(struct lwp *l, const void *v, register_t *retval)
545{
546	struct proc *p = l->l_proc;
547
548	/*
549	 * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
550	 * we use PK_SUGID because we consider changing the owners as
551	 * "tainting" as well.
552	 * This is significant for procs that start as root and "become"
553	 * a user without an exec - programs cannot know *everything*
554	 * that libc *might* have put in their data segment.
555	 */
556	*retval = (p->p_flag & PK_SUGID) != 0;
557	return (0);
558}
559
560/* ARGSUSED */
561int
562sys_setgroups(struct lwp *l, const struct sys_setgroups_args *uap, register_t *retval)
563{
564	/* {
565		syscallarg(int) gidsetsize;
566		syscallarg(const gid_t *) gidset;
567	} */
568	kauth_cred_t ncred;
569	int error;
570
571	ncred = kauth_cred_alloc();
572	error = kauth_cred_setgroups(ncred, SCARG(uap, gidset),
573	    SCARG(uap, gidsetsize), -1, UIO_USERSPACE);
574	if (error != 0) {
575		kauth_cred_free(ncred);
576		return error;
577	}
578
579	return kauth_proc_setgroups(l, ncred);
580}
581
582/*
583 * Get login name, if available.
584 */
585/* ARGSUSED */
586int
587sys___getlogin(struct lwp *l, const struct sys___getlogin_args *uap, register_t *retval)
588{
589	/* {
590		syscallarg(char *) namebuf;
591		syscallarg(size_t) namelen;
592	} */
593	struct proc *p = l->l_proc;
594	char login[sizeof(p->p_session->s_login)];
595	size_t namelen = SCARG(uap, namelen);
596
597	if (namelen > sizeof(login))
598		namelen = sizeof(login);
599	mutex_enter(&proc_lock);
600	memcpy(login, p->p_session->s_login, namelen);
601	mutex_exit(&proc_lock);
602	return (copyout(login, (void *)SCARG(uap, namebuf), namelen));
603}
604
605/*
606 * Set login name.
607 */
608/* ARGSUSED */
609int
610sys___setlogin(struct lwp *l, const struct sys___setlogin_args *uap, register_t *retval)
611{
612	/* {
613		syscallarg(const char *) namebuf;
614	} */
615	struct proc *p = l->l_proc;
616	struct session *sp;
617	char newname[sizeof sp->s_login + 1];
618	int error;
619
620	if ((error = kauth_authorize_process(l->l_cred, KAUTH_PROCESS_SETID,
621	    p, NULL, NULL, NULL)) != 0)
622		return (error);
623	error = copyinstr(SCARG(uap, namebuf), newname, sizeof newname, NULL);
624	if (error != 0)
625		return (error == ENAMETOOLONG ? EINVAL : error);
626
627	mutex_enter(&proc_lock);
628	sp = p->p_session;
629	if (sp->s_flags & S_LOGIN_SET && p->p_pid != sp->s_sid &&
630	    strncmp(newname, sp->s_login, sizeof sp->s_login) != 0)
631		log(LOG_WARNING, "%s (pid %d) changing logname from "
632		    "%.*s to %s\n", p->p_comm, p->p_pid,
633		    (int)sizeof sp->s_login, sp->s_login, newname);
634	sp->s_flags |= S_LOGIN_SET;
635	strncpy(sp->s_login, newname, sizeof sp->s_login);
636	mutex_exit(&proc_lock);
637	return (0);
638}
639