libc/citrus: Catch a NULL pointer earlier, check for empty string later.

[dragonfly.git] / sys / kern / kern_prot.c

/*
 * Copyright (c) 1982, 1986, 1989, 1990, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_prot.c 8.6 (Berkeley) 1/21/94
 * $FreeBSD: src/sys/kern/kern_prot.c,v 1.53.2.9 2002/03/09 05:20:26 dd Exp $
 */

/*
 * System calls related to processes and protection
 */

#include <sys/param.h>
#include <sys/acct.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/priv.h>
#include <sys/malloc.h>
#include <sys/pioctl.h>
#include <sys/resourcevar.h>
#include <sys/jail.h>
#include <sys/lockf.h>
#include <sys/spinlock.h>

#include <sys/thread2.h>
#include <sys/spinlock2.h>

static MALLOC_DEFINE(M_CRED, "cred", "credentials");

int
sys_getpid(struct getpid_args *uap)
{
        struct proc *p = curproc;

        uap->sysmsg_fds[0] = p->p_pid;
        return (0);
}

int
sys_getppid(struct getppid_args *uap)
{
        struct proc *p = curproc;

        uap->sysmsg_result = p->p_ppid;

        return (0);
}

int
sys_lwp_gettid(struct lwp_gettid_args *uap)
{
        struct lwp *lp = curthread->td_lwp;
        uap->sysmsg_result = lp->lwp_tid;
        return (0);
}

/* 
 * Get process group ID; note that POSIX getpgrp takes no parameter 
 */
int
sys_getpgrp(struct getpgrp_args *uap)
{
        struct proc *p = curproc;

        lwkt_gettoken_shared(&p->p_token);
        uap->sysmsg_result = p->p_pgrp->pg_id;
        lwkt_reltoken(&p->p_token);

        return (0);
}

/*
 * Get an arbitrary pid's process group id 
 */
int
sys_getpgid(struct getpgid_args *uap)
{
        struct proc *p = curproc;
        struct proc *pt;
        int error;

        error = 0;

        if (uap->pid == 0) {
                pt = p;
                PHOLD(pt);
        } else {
                pt = pfind(uap->pid);
                if (pt == NULL)
                        error = ESRCH;
        }
        if (error == 0) {
                lwkt_gettoken_shared(&pt->p_token);
                uap->sysmsg_result = pt->p_pgrp->pg_id;
                lwkt_reltoken(&pt->p_token);
        }
        if (pt)
                PRELE(pt);
        return (error);
}

/*
 * Get an arbitrary pid's session id.
 */
int
sys_getsid(struct getsid_args *uap)
{
        struct proc *p = curproc;
        struct proc *pt;
        int error;

        error = 0;

        if (uap->pid == 0) {
                pt = p;
                PHOLD(pt);
        } else {
                pt = pfind(uap->pid);
                if (pt == NULL)
                        error = ESRCH;
        }
        if (error == 0)
                uap->sysmsg_result = pt->p_session->s_sid;
        if (pt)
                PRELE(pt);
        return (error);
}


/*
 * getuid()
 */
int
sys_getuid(struct getuid_args *uap)
{
        struct ucred *cred = curthread->td_ucred;

        uap->sysmsg_fds[0] = cred->cr_ruid;
        return (0);
}

/*
 * geteuid()
 */
int
sys_geteuid(struct geteuid_args *uap)
{
        struct ucred *cred = curthread->td_ucred;

        uap->sysmsg_result = cred->cr_uid;
        return (0);
}

/*
 * getgid()
 */
int
sys_getgid(struct getgid_args *uap)
{
        struct ucred *cred = curthread->td_ucred;

        uap->sysmsg_fds[0] = cred->cr_rgid;
        return (0);
}

/*
 * Get effective group ID.  The "egid" is groups[0], and could be obtained
 * via getgroups.  This syscall exists because it is somewhat painful to do
 * correctly in a library function.
 */
int
sys_getegid(struct getegid_args *uap)
{
        struct ucred *cred = curthread->td_ucred;

        uap->sysmsg_result = cred->cr_groups[0];
        return (0);
}

int
sys_getgroups(struct getgroups_args *uap)
{
        struct ucred *cr;
        u_int ngrp;
        int error;

        cr = curthread->td_ucred;
        if ((ngrp = uap->gidsetsize) == 0) {
                uap->sysmsg_result = cr->cr_ngroups;
                return (0);
        }
        if (ngrp < cr->cr_ngroups)
                return (EINVAL);
        ngrp = cr->cr_ngroups;
        error = copyout((caddr_t)cr->cr_groups,
                        (caddr_t)uap->gidset, ngrp * sizeof(gid_t));
        if (error == 0)
                uap->sysmsg_result = ngrp;
        return (error);
}

int
sys_lwp_setname(struct lwp_setname_args *uap)
{
        struct proc *p = curproc;
        char comm0[MAXCOMLEN + 1];
        const char *comm = NULL;
        struct lwp *lp;
        int error;

        if (uap->name != NULL) {
                error = copyinstr(uap->name, comm0, sizeof(comm0), NULL);
                if (error) {
                        if (error != ENAMETOOLONG)
                                return error;
                        /* Truncate */
                        comm0[MAXCOMLEN] = '\0';
                }
                comm = comm0;
        } else {
                /* Restore to the default name, i.e. process name. */
                comm = p->p_comm;
        }

        lwkt_gettoken(&p->p_token);

        lp = lwp_rb_tree_RB_LOOKUP(&p->p_lwp_tree, uap->tid);
        if (lp != NULL) {
                strlcpy(lp->lwp_thread->td_comm, comm,
                    sizeof(lp->lwp_thread->td_comm));
                error = 0;
        } else {
                error = ESRCH;
        }

        lwkt_reltoken(&p->p_token);
        return error;
}

int
sys_setsid(struct setsid_args *uap)
{
        struct proc *p = curproc;
        struct pgrp *pg = NULL;
        int error;

        lwkt_gettoken(&p->p_token);
        if (p->p_pgid == p->p_pid || (pg = pgfind(p->p_pid)) != NULL) {
                error = EPERM;
                if (pg)
                        pgrel(pg);
        } else {
                enterpgrp(p, p->p_pid, 1);
                uap->sysmsg_result = p->p_pid;
                error = 0;
        }
        lwkt_reltoken(&p->p_token);
        return (error);
}

/*
 * set process group (setpgid/old setpgrp)
 *
 * caller does setpgid(targpid, targpgid)
 *
 * pid must be caller or child of caller (ESRCH)
 * if a child
 *      pid must be in same session (EPERM)
 *      pid can't have done an exec (EACCES)
 * if pgid != pid
 *      there must exist some pid in same session having pgid (EPERM)
 * pid must not be session leader (EPERM)
 */
int
sys_setpgid(struct setpgid_args *uap)
{
        struct proc *curp = curproc;
        struct proc *targp;             /* target process */
        struct pgrp *pgrp = NULL;       /* target pgrp */
        int error;

        if (uap->pgid < 0)
                return (EINVAL);

        if (uap->pid != 0 && uap->pid != curp->p_pid) {
                if ((targp = pfind(uap->pid)) == NULL || !inferior(targp)) {
                        if (targp)
                                PRELE(targp);
                        error = ESRCH;
                        targp = NULL;
                        goto done;
                }
                lwkt_gettoken(&targp->p_token);
                /* targp now referenced and its token is held */

                if (targp->p_pgrp == NULL ||
                    targp->p_session != curp->p_session) {
                        error = EPERM;
                        goto done;
                }
                if (targp->p_flags & P_EXEC) {
                        error = EACCES;
                        goto done;
                }
        } else {
                targp = curp;
                PHOLD(targp);
                lwkt_gettoken(&targp->p_token);
        }
        if (SESS_LEADER(targp)) {
                error = EPERM;
                goto done;
        }
        if (uap->pgid == 0) {
                uap->pgid = targp->p_pid;
        } else if (uap->pgid != targp->p_pid) {
                if ((pgrp = pgfind(uap->pgid)) == NULL ||
                    pgrp->pg_session != curp->p_session) {
                        error = EPERM;
                        goto done;
                }
        }
        error = enterpgrp(targp, uap->pgid, 0);
done:
        if (pgrp)
                pgrel(pgrp);
        if (targp) {
                lwkt_reltoken(&targp->p_token);
                PRELE(targp);
        }
        return (error);
}

/*
 * Use the clause in B.4.2.2 that allows setuid/setgid to be 4.2/4.3BSD
 * compatible.  It says that setting the uid/gid to euid/egid is a special
 * case of "appropriate privilege".  Once the rules are expanded out, this
 * basically means that setuid(nnn) sets all three id's, in all permitted
 * cases unless _POSIX_SAVED_IDS is enabled.  In that case, setuid(getuid())
 * does not set the saved id - this is dangerous for traditional BSD
 * programs.  For this reason, we *really* do not want to set
 * _POSIX_SAVED_IDS and do not want to clear POSIX_APPENDIX_B_4_2_2.
 */
#define POSIX_APPENDIX_B_4_2_2

int
sys_setuid(struct setuid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        uid_t uid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        /*
         * See if we have "permission" by POSIX 1003.1 rules.
         *
         * Note that setuid(geteuid()) is a special case of 
         * "appropriate privileges" in appendix B.4.2.2.  We need
         * to use this clause to be compatible with traditional BSD
         * semantics.  Basically, it means that "setuid(xx)" sets all
         * three id's (assuming you have privs).
         *
         * Notes on the logic.  We do things in three steps.
         * 1: We determine if the euid is going to change, and do EPERM
         *    right away.  We unconditionally change the euid later if this
         *    test is satisfied, simplifying that part of the logic.
         * 2: We determine if the real and/or saved uid's are going to
         *    change.  Determined by compile options.
         * 3: Change euid last. (after tests in #2 for "appropriate privs")
         */
        uid = uap->uid;
        if (uid != cr->cr_ruid &&               /* allow setuid(getuid()) */
#ifdef _POSIX_SAVED_IDS
            uid != crc->cr_svuid &&             /* allow setuid(saved gid) */
#endif
#ifdef POSIX_APPENDIX_B_4_2_2   /* Use BSD-compat clause from B.4.2.2 */
            uid != cr->cr_uid &&        /* allow setuid(geteuid()) */
#endif
            (error = priv_check_cred(cr, PRIV_CRED_SETUID, 0)))
                goto done;

#ifdef _POSIX_SAVED_IDS
        /*
         * Do we have "appropriate privileges" (are we root or uid == euid)
         * If so, we are changing the real uid and/or saved uid.
         */
        if (
#ifdef POSIX_APPENDIX_B_4_2_2   /* Use the clause from B.4.2.2 */
            uid == cr->cr_uid ||
#endif
            priv_check_cred(cr, PRIV_CRED_SETUID, 0) == 0) /* we are using privs */
#endif
        {
                /*
                 * Set the real uid and transfer proc count to new user.
                 */
                if (uid != cr->cr_ruid) {
                        cr = change_ruid(uid);
                        setsugid();
                }
                /*
                 * Set saved uid
                 *
                 * XXX always set saved uid even if not _POSIX_SAVED_IDS, as
                 * the security of seteuid() depends on it.  B.4.2.2 says it
                 * is important that we should do this.
                 */
                if (cr->cr_svuid != uid) {
                        cr = cratom_proc(p);
                        cr->cr_svuid = uid;
                        setsugid();
                }
        }

        /*
         * In all permitted cases, we are changing the euid.
         * Copy credentials so other references do not see our changes.
         */
        if (cr->cr_uid != uid) {
                change_euid(uid);
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_seteuid(struct seteuid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        uid_t euid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;
        euid = uap->euid;
        if (euid != cr->cr_ruid &&              /* allow seteuid(getuid()) */
            euid != cr->cr_svuid &&             /* allow seteuid(saved uid) */
            (error = priv_check_cred(cr, PRIV_CRED_SETEUID, 0))) {
                lwkt_reltoken(&p->p_token);
                return (error);
        }

        /*
         * Everything's okay, do it.  Copy credentials so other references do
         * not see our changes.
         */
        if (cr->cr_uid != euid) {
                change_euid(euid);
                setsugid();
        }
        lwkt_reltoken(&p->p_token);
        return (0);
}

int
sys_setgid(struct setgid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        gid_t gid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        /*
         * See if we have "permission" by POSIX 1003.1 rules.
         *
         * Note that setgid(getegid()) is a special case of
         * "appropriate privileges" in appendix B.4.2.2.  We need
         * to use this clause to be compatible with traditional BSD
         * semantics.  Basically, it means that "setgid(xx)" sets all
         * three id's (assuming you have privs).
         *
         * For notes on the logic here, see setuid() above.
         */
        gid = uap->gid;
        if (gid != cr->cr_rgid &&               /* allow setgid(getgid()) */
#ifdef _POSIX_SAVED_IDS
            gid != cr->cr_svgid &&              /* allow setgid(saved gid) */
#endif
#ifdef POSIX_APPENDIX_B_4_2_2   /* Use BSD-compat clause from B.4.2.2 */
            gid != cr->cr_groups[0] && /* allow setgid(getegid()) */
#endif
            (error = priv_check_cred(cr, PRIV_CRED_SETGID, 0))) {
                goto done;
        }

#ifdef _POSIX_SAVED_IDS
        /*
         * Do we have "appropriate privileges" (are we root or gid == egid)
         * If so, we are changing the real uid and saved gid.
         */
        if (
#ifdef POSIX_APPENDIX_B_4_2_2   /* use the clause from B.4.2.2 */
            gid == cr->cr_groups[0] ||
#endif
            priv_check_cred(cr, PRIV_CRED_SETGID, 0) == 0) /* we are using privs */
#endif
        {
                /*
                 * Set real gid
                 */
                if (cr->cr_rgid != gid) {
                        cr = cratom_proc(p);
                        cr->cr_rgid = gid;
                        setsugid();
                }
                /*
                 * Set saved gid
                 *
                 * XXX always set saved gid even if not _POSIX_SAVED_IDS, as
                 * the security of setegid() depends on it.  B.4.2.2 says it
                 * is important that we should do this.
                 */
                if (cr->cr_svgid != gid) {
                        cr = cratom_proc(p);
                        cr->cr_svgid = gid;
                        setsugid();
                }
        }
        /*
         * In all cases permitted cases, we are changing the egid.
         * Copy credentials so other references do not see our changes.
         */
        if (cr->cr_groups[0] != gid) {
                cr = cratom_proc(p);
                cr->cr_groups[0] = gid;
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_setegid(struct setegid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        gid_t egid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;
        egid = uap->egid;
        if (egid != cr->cr_rgid &&              /* allow setegid(getgid()) */
            egid != cr->cr_svgid &&             /* allow setegid(saved gid) */
            (error = priv_check_cred(cr, PRIV_CRED_SETEGID, 0))) {
                goto done;
        }
        if (cr->cr_groups[0] != egid) {
                cr = cratom_proc(p);
                cr->cr_groups[0] = egid;
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_setgroups(struct setgroups_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        u_int ngrp;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        if ((error = priv_check_cred(cr, PRIV_CRED_SETGROUPS, 0)))
                goto done;
        ngrp = uap->gidsetsize;
        if (ngrp > NGROUPS) {
                error = EINVAL;
                goto done;
        }
        /*
         * XXX A little bit lazy here.  We could test if anything has
         * changed before cratom() and setting P_SUGID.
         */
        cr = cratom_proc(p);
        if (ngrp < 1) {
                /*
                 * setgroups(0, NULL) is a legitimate way of clearing the
                 * groups vector on non-BSD systems (which generally do not
                 * have the egid in the groups[0]).  We risk security holes
                 * when running non-BSD software if we do not do the same.
                 */
                cr->cr_ngroups = 1;
        } else {
                error = copyin(uap->gidset, cr->cr_groups,
                               ngrp * sizeof(gid_t));
                if (error)
                        goto done;
                cr->cr_ngroups = ngrp;
        }
        setsugid();
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_setreuid(struct setreuid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        uid_t ruid, euid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        ruid = uap->ruid;
        euid = uap->euid;
        if (((ruid != (uid_t)-1 && ruid != cr->cr_ruid &&
              ruid != cr->cr_svuid) ||
             (euid != (uid_t)-1 && euid != cr->cr_uid &&
              euid != cr->cr_ruid && euid != cr->cr_svuid)) &&
            (error = priv_check_cred(cr, PRIV_CRED_SETREUID, 0)) != 0) {
                goto done;
        }

        if (euid != (uid_t)-1 && cr->cr_uid != euid) {
                cr = change_euid(euid);
                setsugid();
        }
        if (ruid != (uid_t)-1 && cr->cr_ruid != ruid) {
                cr = change_ruid(ruid);
                setsugid();
        }
        if ((ruid != (uid_t)-1 || cr->cr_uid != cr->cr_ruid) &&
            cr->cr_svuid != cr->cr_uid) {
                cr = cratom_proc(p);
                cr->cr_svuid = cr->cr_uid;
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_setregid(struct setregid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        gid_t rgid, egid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        rgid = uap->rgid;
        egid = uap->egid;
        if (((rgid != (gid_t)-1 && rgid != cr->cr_rgid &&
              rgid != cr->cr_svgid) ||
             (egid != (gid_t)-1 && egid != cr->cr_groups[0] &&
              egid != cr->cr_rgid && egid != cr->cr_svgid)) &&
            (error = priv_check_cred(cr, PRIV_CRED_SETREGID, 0)) != 0) {
                goto done;
        }

        if (egid != (gid_t)-1 && cr->cr_groups[0] != egid) {
                cr = cratom_proc(p);
                cr->cr_groups[0] = egid;
                setsugid();
        }
        if (rgid != (gid_t)-1 && cr->cr_rgid != rgid) {
                cr = cratom_proc(p);
                cr->cr_rgid = rgid;
                setsugid();
        }
        if ((rgid != (gid_t)-1 || cr->cr_groups[0] != cr->cr_rgid) &&
            cr->cr_svgid != cr->cr_groups[0]) {
                cr = cratom_proc(p);
                cr->cr_svgid = cr->cr_groups[0];
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

/*
 * setresuid(ruid, euid, suid) is like setreuid except control over the
 * saved uid is explicit.
 */
int
sys_setresuid(struct setresuid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        uid_t ruid, euid, suid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;

        ruid = uap->ruid;
        euid = uap->euid;
        suid = uap->suid;
        if (((ruid != (uid_t)-1 && ruid != cr->cr_ruid &&
              ruid != cr->cr_svuid && ruid != cr->cr_uid) ||
             (euid != (uid_t)-1 && euid != cr->cr_ruid &&
              euid != cr->cr_svuid && euid != cr->cr_uid) ||
             (suid != (uid_t)-1 && suid != cr->cr_ruid &&
              suid != cr->cr_svuid && suid != cr->cr_uid)) &&
            (error = priv_check_cred(cr, PRIV_CRED_SETRESUID, 0)) != 0) {
                goto done;
        }
        if (euid != (uid_t)-1 && cr->cr_uid != euid) {
                cr = change_euid(euid);
                setsugid();
        }
        if (ruid != (uid_t)-1 && cr->cr_ruid != ruid) {
                cr = change_ruid(ruid);
                setsugid();
        }
        if (suid != (uid_t)-1 && cr->cr_svuid != suid) {
                cr = cratom_proc(p);
                cr->cr_svuid = suid;
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

/*
 * setresgid(rgid, egid, sgid) is like setregid except control over the
 * saved gid is explicit.
 */
int
sys_setresgid(struct setresgid_args *uap)
{
        struct proc *p = curproc;
        struct ucred *cr;
        gid_t rgid, egid, sgid;
        int error;

        lwkt_gettoken(&p->p_token);
        cr = p->p_ucred;
        rgid = uap->rgid;
        egid = uap->egid;
        sgid = uap->sgid;
        if (((rgid != (gid_t)-1 && rgid != cr->cr_rgid &&
              rgid != cr->cr_svgid && rgid != cr->cr_groups[0]) ||
             (egid != (gid_t)-1 && egid != cr->cr_rgid &&
              egid != cr->cr_svgid && egid != cr->cr_groups[0]) ||
             (sgid != (gid_t)-1 && sgid != cr->cr_rgid &&
              sgid != cr->cr_svgid && sgid != cr->cr_groups[0])) &&
            (error = priv_check_cred(cr, PRIV_CRED_SETRESGID, 0)) != 0) {
                goto done;
        }

        if (egid != (gid_t)-1 && cr->cr_groups[0] != egid) {
                cr = cratom_proc(p);
                cr->cr_groups[0] = egid;
                setsugid();
        }
        if (rgid != (gid_t)-1 && cr->cr_rgid != rgid) {
                cr = cratom_proc(p);
                cr->cr_rgid = rgid;
                setsugid();
        }
        if (sgid != (gid_t)-1 && cr->cr_svgid != sgid) {
                cr = cratom_proc(p);
                cr->cr_svgid = sgid;
                setsugid();
        }
        error = 0;
done:
        lwkt_reltoken(&p->p_token);
        return (error);
}

int
sys_getresuid(struct getresuid_args *uap)
{
        struct ucred *cr;
        int error1 = 0, error2 = 0, error3 = 0;

        /*
         * copyout's can fault synchronously so we cannot use a shared
         * token here.
         */
        cr = curthread->td_ucred;
        if (uap->ruid)
                error1 = copyout((caddr_t)&cr->cr_ruid,
                    (caddr_t)uap->ruid, sizeof(cr->cr_ruid));
        if (uap->euid)
                error2 = copyout((caddr_t)&cr->cr_uid,
                    (caddr_t)uap->euid, sizeof(cr->cr_uid));
        if (uap->suid)
                error3 = copyout((caddr_t)&cr->cr_svuid,
                    (caddr_t)uap->suid, sizeof(cr->cr_svuid));
        return error1 ? error1 : (error2 ? error2 : error3);
}

int
sys_getresgid(struct getresgid_args *uap)
{
        struct ucred *cr;
        int error1 = 0, error2 = 0, error3 = 0;

        cr = curthread->td_ucred;
        if (uap->rgid)
                error1 = copyout(&cr->cr_rgid, uap->rgid,
                                 sizeof(cr->cr_rgid));
        if (uap->egid)
                error2 = copyout(&cr->cr_groups[0], uap->egid,
                                 sizeof(cr->cr_groups[0]));
        if (uap->sgid)
                error3 = copyout(&cr->cr_svgid, uap->sgid,
                                 sizeof(cr->cr_svgid));
        return error1 ? error1 : (error2 ? error2 : error3);
}


/*
 * NOTE: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
 * we use P_SUGID because we consider changing the owners as
 * "tainting" as well.
 * This is significant for procs that start as root and "become"
 * a user without an exec - programs cannot know *everything*
 * that libc *might* have put in their data segment.
 */
int
sys_issetugid(struct issetugid_args *uap)
{
        uap->sysmsg_result = (curproc->p_flags & P_SUGID) ? 1 : 0;
        return (0);
}

/*
 * Check if gid is a member of the group set.
 */
int
groupmember(gid_t gid, struct ucred *cred)
{
        gid_t *gp;
        gid_t *egp;

        egp = &(cred->cr_groups[cred->cr_ngroups]);
        for (gp = cred->cr_groups; gp < egp; gp++) {
                if (*gp == gid)
                        return (1);
        }
        return (0);
}

/*
 * Test whether the specified credentials have the privilege
 * in question.
 *
 * A kernel thread without a process context is assumed to have 
 * the privilege in question.  In situations where the caller always 
 * expect a cred to exist, the cred should be passed separately and 
 * priv_check_cred() should be used instead of priv_check().
 *
 * Returns 0 or error.
 */
int
priv_check(struct thread *td, int priv)
{
        if (td->td_lwp != NULL)
                return priv_check_cred(td->td_ucred, priv, 0);
        return (0);
}

/*
 * Check a credential for privilege.
 *
 * A non-null credential is expected unless NULL_CRED_OKAY is set.
 */
int
priv_check_cred(struct ucred *cred, int priv, int flags)
{
        int error;

        KASSERT(PRIV_VALID(priv), ("priv_check_cred: invalid privilege"));

        KASSERT(cred != NULL || (flags & NULL_CRED_OKAY),
                ("priv_check_cred: NULL cred!"));

        if (cred == NULL) {
                if (flags & NULL_CRED_OKAY)
                        return (0);
                else
                        return (EPERM);
        }
        if (cred->cr_uid != 0) 
                return (EPERM);

        error = prison_priv_check(cred, priv);
        if (error)
                return (error);

        /* NOTE: accounting for suser access (p_acflag/ASU) removed */
        return (0);
}

/*
 * Return zero if p1 can fondle p2, return errno (EPERM/ESRCH) otherwise.
 */
int
p_trespass(struct ucred *cr1, struct ucred *cr2)
{
        if (cr1 == cr2)
                return (0);
        if (!PRISON_CHECK(cr1, cr2))
                return (ESRCH);
        if (cr1->cr_ruid == cr2->cr_ruid)
                return (0);
        if (cr1->cr_uid == cr2->cr_ruid)
                return (0);
        if (cr1->cr_ruid == cr2->cr_uid)
                return (0);
        if (cr1->cr_uid == cr2->cr_uid)
                return (0);
        if (priv_check_cred(cr1, PRIV_PROC_TRESPASS, 0) == 0)
                return (0);
        return (EPERM);
}

static __inline void
_crinit(struct ucred *cr)
{
        cr->cr_ref = 1;
}

void
crinit(struct ucred *cr)
{
        bzero(cr, sizeof(*cr));
        _crinit(cr);
}

/*
 * Allocate a zeroed cred structure.
 */
struct ucred *
crget(void)
{
        struct ucred *cr;

        cr = kmalloc(sizeof(*cr), M_CRED, M_WAITOK|M_ZERO);
        _crinit(cr);
        return (cr);
}

/*
 * Claim another reference to a ucred structure.  Can be used with special
 * creds.
 *
 * It must be possible to call this routine with spinlocks held, meaning
 * that this routine itself cannot obtain a spinlock.
 */
struct ucred *
crhold(struct ucred *cr)
{
        if (cr != NOCRED && cr != FSCRED)
                atomic_add_long(&cr->cr_ref, 1);
        return(cr);
}

/*
 * Drop a reference from the cred structure, free it if the reference count
 * reaches 0. 
 *
 * NOTE: because we used atomic_add_int() above, without a spinlock, we
 * must also use atomic_subtract_int() below.  A spinlock is required
 * in crfree() to handle multiple callers racing the refcount to 0.
 */
void
crfree(struct ucred *cr)
{
        if (cr->cr_ref <= 0)
                panic("Freeing already free credential! %p", cr);
        if (atomic_fetchadd_long(&cr->cr_ref, -1) == 1) {
                /*
                 * Some callers of crget(), such as nfs_statfs(),
                 * allocate a temporary credential, but don't
                 * allocate a uidinfo structure.
                 */
                if (cr->cr_uidinfo != NULL) {
                        uidrop(cr->cr_uidinfo);
                        cr->cr_uidinfo = NULL;
                }
                if (cr->cr_ruidinfo != NULL) {
                        uidrop(cr->cr_ruidinfo);
                        cr->cr_ruidinfo = NULL;
                }

                /*
                 * Destroy empty prisons
                 */
                if (jailed(cr))
                        prison_free(cr->cr_prison);
                cr->cr_prison = NULL;   /* safety */

                kfree((caddr_t)cr, M_CRED);
        }
}

/*
 * Atomize a cred structure so it can be modified without polluting
 * other references to it.
 *
 * MPSAFE (however, *pcr must be stable)
 */
struct ucred *
cratom(struct ucred **pcr)
{
        struct ucred *oldcr;
        struct ucred *newcr;

        oldcr = *pcr;
        if (oldcr->cr_ref == 1)
                return (oldcr);
        newcr = crget();        /* this might block */
        oldcr = *pcr;           /* re-cache after potentially blocking */
        *newcr = *oldcr;
        uihold(newcr->cr_uidinfo);
        uihold(newcr->cr_ruidinfo);
        if (jailed(newcr))
                prison_hold(newcr->cr_prison);
        newcr->cr_ref = 1;
        crfree(oldcr);
        *pcr = newcr;

        return (newcr);
}

/*
 * Called with a modifying token held, but must still obtain p_spin to
 * actually replace p_ucred to handle races against syscall entry from
 * other threads which cache p_ucred->td_ucred.
 *
 * (the threads will only get the spin-lock, and they only need to in
 *  the case where td_ucred != p_ucred so this is optimal).
 */
struct ucred *
cratom_proc(struct proc *p)
{
        struct ucred *oldcr;
        struct ucred *newcr;

        oldcr = p->p_ucred;
        if (oldcr->cr_ref == 1)
                return(oldcr);

        newcr = crget();        /* this might block */
        oldcr = p->p_ucred;     /* so re-cache oldcr (do not re-test) */
        *newcr = *oldcr;
        uihold(newcr->cr_uidinfo);
        uihold(newcr->cr_ruidinfo);
        if (jailed(newcr))
                prison_hold(newcr->cr_prison);
        newcr->cr_ref = 1;

        spin_lock(&p->p_spin);
        p->p_ucred = newcr;
        spin_unlock(&p->p_spin);
        crfree(oldcr);

        return newcr;
}

/*
 * Dup cred struct to a new held one.
 */
struct ucred *
crdup(struct ucred *cr)
{
        struct ucred *newcr;

        newcr = crget();
        *newcr = *cr;
        uihold(newcr->cr_uidinfo);
        uihold(newcr->cr_ruidinfo);
        if (jailed(newcr))
                prison_hold(newcr->cr_prison);
        newcr->cr_ref = 1;
        return (newcr);
}

/*
 * Fill in a struct xucred based on a struct ucred.
 */
void
cru2x(struct ucred *cr, struct xucred *xcr)
{

        bzero(xcr, sizeof(*xcr));
        xcr->cr_version = XUCRED_VERSION;
        xcr->cr_uid = cr->cr_uid;
        xcr->cr_ngroups = cr->cr_ngroups;
        bcopy(cr->cr_groups, xcr->cr_groups, sizeof(cr->cr_groups));
}

/*
 * Get login name, if available.
 */
int
sys_getlogin(struct getlogin_args *uap)
{
        struct proc *p = curproc;
        char buf[MAXLOGNAME];
        int error;

        if (uap->namelen > MAXLOGNAME)          /* namelen is unsigned */
                uap->namelen = MAXLOGNAME;
        bzero(buf, sizeof(buf));
        lwkt_gettoken_shared(&p->p_token);
        bcopy(p->p_pgrp->pg_session->s_login, buf, uap->namelen);
        lwkt_reltoken(&p->p_token);

        error = copyout(buf, uap->namebuf, uap->namelen);
        return (error);
}

/*
 * Set login name.
 */
int
sys_setlogin(struct setlogin_args *uap)
{
        struct thread *td = curthread;
        struct proc *p;
        struct ucred *cred;
        char buf[MAXLOGNAME];
        int error;

        cred = td->td_ucred;
        p = td->td_proc;

        if ((error = priv_check_cred(cred, PRIV_PROC_SETLOGIN, 0)))
                return (error);
        bzero(buf, sizeof(buf));
        error = copyinstr(uap->namebuf, buf, sizeof(buf), NULL);
        if (error == ENAMETOOLONG)
                error = EINVAL;
        if (error == 0) {
                lwkt_gettoken_shared(&p->p_token);
                memcpy(p->p_pgrp->pg_session->s_login, buf, sizeof(buf));
                lwkt_reltoken(&p->p_token);
        }
        return (error);
}

void
setsugid(void)
{
        struct proc *p = curproc;

        KKASSERT(p != NULL);
        lwkt_gettoken(&p->p_token);
        p->p_flags |= P_SUGID;
        if (!(p->p_pfsflags & PF_ISUGID))
                p->p_stops = 0;
        lwkt_reltoken(&p->p_token);
}

/*
 * Helper function to change the effective uid of a process
 */
struct ucred *
change_euid(uid_t euid)
{
        struct  proc *p = curproc;
        struct  ucred *cr;

        KKASSERT(p != NULL);
        lf_count_adjust(p, 0);
        cr = cratom_proc(p);
        cr->cr_uid = euid;
        uireplace(&cr->cr_uidinfo, uifind(euid));
        lf_count_adjust(p, 1);
        return (cr);
}

/*
 * Helper function to change the real uid of a process
 *
 * The per-uid process count for this process is transfered from
 * the old uid to the new uid.
 */
struct ucred *
change_ruid(uid_t ruid)
{
        struct  proc *p = curproc;
        struct  ucred *cr;

        KKASSERT(p != NULL);

        cr = cratom_proc(p);
        chgproccnt(cr->cr_ruidinfo, -1, 0);
        cr->cr_ruid = ruid;
        uireplace(&cr->cr_ruidinfo, uifind(ruid));
        chgproccnt(cr->cr_ruidinfo, 1, 0);
        return (cr);
}