FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_prot.c

     /*      $NetBSD: kern_prot.c,v 1.122 2020/05/23 23:42:43 ad Exp $       */
     
     /*
      * 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 8.9 (Berkeley) 2/14/95
     */
    
    /*
     * System calls related to processes and protection
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: kern_prot.c,v 1.122 2020/05/23 23:42:43 ad Exp $");
    
    #ifdef _KERNEL_OPT
    #include "opt_compat_43.h"
    #endif
    
    #include <sys/param.h>
    #include <sys/acct.h>
    #include <sys/systm.h>
    #include <sys/ucred.h>
    #include <sys/proc.h>
    #include <sys/timeb.h>
    #include <sys/times.h>
    #include <sys/pool.h>
    #include <sys/prot.h>
    #include <sys/syslog.h>
    #include <sys/uidinfo.h>
    #include <sys/kauth.h>
    
    #include <sys/mount.h>
    #include <sys/syscallargs.h>
    
    int     sys_getpid(struct lwp *, const void *, register_t *);
    int     sys_getpid_with_ppid(struct lwp *, const void *, register_t *);
    int     sys_getuid(struct lwp *, const void *, register_t *);
    int     sys_getuid_with_euid(struct lwp *, const void *, register_t *);
    int     sys_getgid(struct lwp *, const void *, register_t *);
    int     sys_getgid_with_egid(struct lwp *, const void *, register_t *);
    
    /* ARGSUSED */
    int
    sys_getpid(struct lwp *l, const void *v, register_t *retval)
    {
            struct proc *p = l->l_proc;
    
            *retval = p->p_pid;
            return (0);
    }
    
    /* ARGSUSED */
    int
    sys_getpid_with_ppid(struct lwp *l, const void *v, register_t *retval)
    {
            struct proc *p = l->l_proc;
    
            retval[0] = p->p_pid;
            retval[1] = p->p_ppid;
            return (0);
    }
    
    /* ARGSUSED */
    int
    sys_getppid(struct lwp *l, const void *v, register_t *retval)
    {
            struct proc *p = l->l_proc;
    
           *retval = p->p_ppid;
           return (0);
   }
   
   /* Get process group ID; note that POSIX getpgrp takes no parameter */
   int
   sys_getpgrp(struct lwp *l, const void *v, register_t *retval)
   {
           struct proc *p = l->l_proc;
   
           mutex_enter(&proc_lock);
           *retval = p->p_pgrp->pg_id;
           mutex_exit(&proc_lock);
           return (0);
   }
   
   /*
    * Return the process group ID of the session leader (session ID)
    * for the specified process.
    */
   int
   sys_getsid(struct lwp *l, const struct sys_getsid_args *uap, register_t *retval)
   {
           /* {
                   syscalldarg(pid_t) pid;
           } */
           pid_t pid = SCARG(uap, pid);
           struct proc *p;
           int error = 0;
   
           mutex_enter(&proc_lock);
           if (pid == 0)
                   *retval = l->l_proc->p_session->s_sid;
           else if ((p = proc_find(pid)) != NULL)
                   *retval = p->p_session->s_sid;
           else
                   error = ESRCH;
           mutex_exit(&proc_lock);
   
           return error;
   }
   
   int
   sys_getpgid(struct lwp *l, const struct sys_getpgid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(pid_t) pid;
           } */
           pid_t pid = SCARG(uap, pid);
           struct proc *p;
           int error = 0;
   
           mutex_enter(&proc_lock);
           if (pid == 0)
                   *retval = l->l_proc->p_pgid;
           else if ((p = proc_find(pid)) != NULL)
                   *retval = p->p_pgid;
           else
                   error = ESRCH;
           mutex_exit(&proc_lock);
   
           return error;
   }
   
   /* ARGSUSED */
   int
   sys_getuid(struct lwp *l, const void *v, register_t *retval)
   {
   
           *retval = kauth_cred_getuid(l->l_cred);
           return (0);
   }
   
   /* ARGSUSED */
   int
   sys_getuid_with_euid(struct lwp *l, const void *v, register_t *retval)
   {
   
           retval[0] = kauth_cred_getuid(l->l_cred);
           retval[1] = kauth_cred_geteuid(l->l_cred);
           return (0);
   }
   
   /* ARGSUSED */
   int
   sys_geteuid(struct lwp *l, const void *v, register_t *retval)
   {
   
           *retval = kauth_cred_geteuid(l->l_cred);
           return (0);
   }
   
   /* ARGSUSED */
   int
   sys_getgid(struct lwp *l, const void *v, register_t *retval)
   {
   
           *retval = kauth_cred_getgid(l->l_cred);
           return (0);
   }
   
   /* ARGSUSED */
   int
   sys_getgid_with_egid(struct lwp *l, const void *v, register_t *retval)
   {
   
           retval[0] = kauth_cred_getgid(l->l_cred);
           retval[1] = kauth_cred_getegid(l->l_cred);
           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.
    */
   /* ARGSUSED */
   int
   sys_getegid(struct lwp *l, const void *v, register_t *retval)
   {
   
           *retval = kauth_cred_getegid(l->l_cred);
           return (0);
   }
   
   int
   sys_getgroups(struct lwp *l, const struct sys_getgroups_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(int) gidsetsize;
                   syscallarg(gid_t *) gidset;
           } */
   
           *retval = kauth_cred_ngroups(l->l_cred);
           if (SCARG(uap, gidsetsize) == 0)
                   return 0;
           if (SCARG(uap, gidsetsize) < (int)*retval)
                   return EINVAL;
   
           return kauth_cred_getgroups(l->l_cred, SCARG(uap, gidset), *retval,
               UIO_USERSPACE);
   }
   
   int
   sys_setsid(struct lwp *l, const void *v, register_t *retval)
   {
           struct proc *p = l->l_proc;
           int error;
   
           error = proc_enterpgrp(p, p->p_pid, p->p_pid, true);
           *retval = p->p_pid;
           return (error);
   }
   
   
   /*
    * set process group (setpgid/old setpgrp)
    *
    * caller does setpgid(targpid, targpgid)
    *
    * pgid must be in valid range (EINVAL)
    * 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)
    *
    * Permission checks now in proc_enterpgrp()
    */
   int
   sys_setpgid(struct lwp *l, const struct sys_setpgid_args *uap,
       register_t *retval)
   {
           /* {
                   syscallarg(int) pid;
                   syscallarg(int) pgid;
           } */
           struct proc *p = l->l_proc;
           pid_t targp, pgid;
   
           if (SCARG(uap, pgid) < 0)
                   return EINVAL;
           if ((targp = SCARG(uap, pid)) == 0)
                   targp = p->p_pid;
           if ((pgid = SCARG(uap, pgid)) == 0)
                   pgid = targp;
   
           return proc_enterpgrp(p, targp, pgid, false);
   }
   
   /*
    * Set real, effective and saved uids to the requested values.
    * non-root callers can only ever change uids to values that match
    * one of the processes current uid values.
    * This is further restricted by the flags argument.
    */
   
   int
   do_setresuid(struct lwp *l, uid_t r, uid_t e, uid_t sv, u_int flags)
   {
           struct proc *p = l->l_proc;
           kauth_cred_t cred, ncred;
   
           ncred = kauth_cred_alloc();
   
           /* Get a write lock on the process credential. */
           proc_crmod_enter();
           cred = p->p_cred;
   
           /*
            * Check that the new value is one of the allowed existing values,
            * or that we have root privilege.
            */
           if ((r != -1
               && !((flags & ID_R_EQ_R) && r == kauth_cred_getuid(cred))
               && !((flags & ID_R_EQ_E) && r == kauth_cred_geteuid(cred))
               && !((flags & ID_R_EQ_S) && r == kauth_cred_getsvuid(cred))) ||
               (e != -1
               && !((flags & ID_E_EQ_R) && e == kauth_cred_getuid(cred))
               && !((flags & ID_E_EQ_E) && e == kauth_cred_geteuid(cred))
               && !((flags & ID_E_EQ_S) && e == kauth_cred_getsvuid(cred))) ||
               (sv != -1
               && !((flags & ID_S_EQ_R) && sv == kauth_cred_getuid(cred))
               && !((flags & ID_S_EQ_E) && sv == kauth_cred_geteuid(cred))
               && !((flags & ID_S_EQ_S) && sv == kauth_cred_getsvuid(cred)))) {
                   int error;
   
                   error = kauth_authorize_process(cred, KAUTH_PROCESS_SETID,
                       p, NULL, NULL, NULL);
                   if (error != 0) {
                           proc_crmod_leave(cred, ncred, false);
                           return error;
                   }
           }
   
           /* If nothing has changed, short circuit the request */
           if ((r == -1 || r == kauth_cred_getuid(cred))
               && (e == -1 || e == kauth_cred_geteuid(cred))
               && (sv == -1 || sv == kauth_cred_getsvuid(cred))) {
                   proc_crmod_leave(cred, ncred, false);
                   return 0;
           }
   
           kauth_cred_clone(cred, ncred);
   
           if (r != -1 && r != kauth_cred_getuid(ncred)) {
                   u_long nlwps;
   
                   /* Update count of processes for this user. */
                   (void)chgproccnt(kauth_cred_getuid(ncred), -1);
                   (void)chgproccnt(r, 1);
   
                   /* The first LWP of a process is excluded. */
                   KASSERT(mutex_owned(p->p_lock));
                   nlwps = p->p_nlwps - 1;
                   (void)chglwpcnt(kauth_cred_getuid(ncred), -nlwps);
                   (void)chglwpcnt(r, nlwps);
   
                   kauth_cred_setuid(ncred, r);
           }
           if (sv != -1)
                   kauth_cred_setsvuid(ncred, sv);
           if (e != -1)
                   kauth_cred_seteuid(ncred, e);
   
           /* Broadcast our credentials to the process and other LWPs. */
           proc_crmod_leave(ncred, cred, true);
   
           return 0;
   }
   
   /*
    * Set real, effective and saved gids to the requested values.
    * non-root callers can only ever change gids to values that match
    * one of the processes current gid values.
    * This is further restricted by the flags argument.
    */
   
   int
   do_setresgid(struct lwp *l, gid_t r, gid_t e, gid_t sv, u_int flags)
   {
           struct proc *p = l->l_proc;
           kauth_cred_t cred, ncred;
   
           ncred = kauth_cred_alloc();
   
           /* Get a write lock on the process credential. */
           proc_crmod_enter();
           cred = p->p_cred;
   
           /*
            * check new value is one of the allowed existing values.
            * otherwise, check if we have root privilege.
            */
           if ((r != -1
               && !((flags & ID_R_EQ_R) && r == kauth_cred_getgid(cred))
               && !((flags & ID_R_EQ_E) && r == kauth_cred_getegid(cred))
               && !((flags & ID_R_EQ_S) && r == kauth_cred_getsvgid(cred))) ||
               (e != -1
               && !((flags & ID_E_EQ_R) && e == kauth_cred_getgid(cred))
               && !((flags & ID_E_EQ_E) && e == kauth_cred_getegid(cred))
               && !((flags & ID_E_EQ_S) && e == kauth_cred_getsvgid(cred))) ||
               (sv != -1
               && !((flags & ID_S_EQ_R) && sv == kauth_cred_getgid(cred))
               && !((flags & ID_S_EQ_E) && sv == kauth_cred_getegid(cred))
               && !((flags & ID_S_EQ_S) && sv == kauth_cred_getsvgid(cred)))) {
                   int error;
   
                   error = kauth_authorize_process(cred, KAUTH_PROCESS_SETID,
                       p, NULL, NULL, NULL);
                   if (error != 0) {
                           proc_crmod_leave(cred, ncred, false);
                           return error;
                   }
           }
   
           /* If nothing has changed, short circuit the request */
           if ((r == -1 || r == kauth_cred_getgid(cred))
               && (e == -1 || e == kauth_cred_getegid(cred))
               && (sv == -1 || sv == kauth_cred_getsvgid(cred))) {
                   proc_crmod_leave(cred, ncred, false);
                   return 0;
           }
   
           kauth_cred_clone(cred, ncred);
   
           if (r != -1)
                   kauth_cred_setgid(ncred, r);
           if (sv != -1)
                   kauth_cred_setsvgid(ncred, sv);
           if (e != -1)
                   kauth_cred_setegid(ncred, e);
   
           /* Broadcast our credentials to the process and other LWPs. */
           proc_crmod_leave(ncred, cred, true);
   
           return 0;
   }
   
   /* ARGSUSED */
   int
   sys_setuid(struct lwp *l, const struct sys_setuid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(uid_t) uid;
           } */
           uid_t uid = SCARG(uap, uid);
   
           return do_setresuid(l, uid, uid, uid,
                               ID_R_EQ_R | ID_E_EQ_R | ID_S_EQ_R);
   }
   
   /* ARGSUSED */
   int
   sys_seteuid(struct lwp *l, const struct sys_seteuid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(uid_t) euid;
           } */
   
           return do_setresuid(l, -1, SCARG(uap, euid), -1, ID_E_EQ_R | ID_E_EQ_S);
   }
   
   int
   sys_setreuid(struct lwp *l, const struct sys_setreuid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(uid_t) ruid;
                   syscallarg(uid_t) euid;
           } */
           kauth_cred_t cred = l->l_cred;
           uid_t ruid, euid, svuid;
   
           ruid = SCARG(uap, ruid);
           euid = SCARG(uap, euid);
   
           if (ruid == -1)
                   ruid = kauth_cred_getuid(cred);
           if (euid == -1)
                   euid = kauth_cred_geteuid(cred);
   
           /* Saved uid is set to the new euid if the ruid changed */
           svuid = (ruid == kauth_cred_getuid(cred)) ? -1 : euid;
   
           return do_setresuid(l, ruid, euid, svuid,
                               ID_R_EQ_R | ID_R_EQ_E |
                               ID_E_EQ_R | ID_E_EQ_E | ID_E_EQ_S |
                               ID_S_EQ_R | ID_S_EQ_E | ID_S_EQ_S);
   }
   
   /* ARGSUSED */
   int
   sys_setgid(struct lwp *l, const struct sys_setgid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(gid_t) gid;
           } */
           gid_t gid = SCARG(uap, gid);
   
           return do_setresgid(l, gid, gid, gid,
                               ID_R_EQ_R | ID_E_EQ_R | ID_S_EQ_R);
   }
   
   /* ARGSUSED */
   int
   sys_setegid(struct lwp *l, const struct sys_setegid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(gid_t) egid;
           } */
   
           return do_setresgid(l, -1, SCARG(uap, egid), -1, ID_E_EQ_R | ID_E_EQ_S);
   }
   
   int
   sys_setregid(struct lwp *l, const struct sys_setregid_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(gid_t) rgid;
                   syscallarg(gid_t) egid;
           } */
           kauth_cred_t cred = l->l_cred;
           gid_t rgid, egid, svgid;
   
           rgid = SCARG(uap, rgid);
           egid = SCARG(uap, egid);
   
           if (rgid == -1)
                   rgid = kauth_cred_getgid(cred);
           if (egid == -1)
                   egid = kauth_cred_getegid(cred);
   
           /* Saved gid is set to the new egid if the rgid changed */
           svgid = rgid == kauth_cred_getgid(cred) ? -1 : egid;
   
           return do_setresgid(l, rgid, egid, svgid,
                           ID_R_EQ_R | ID_R_EQ_E |
                           ID_E_EQ_R | ID_E_EQ_E | ID_E_EQ_S |
                           ID_S_EQ_R | ID_S_EQ_E | ID_S_EQ_S);
   }
   
   int
   sys_issetugid(struct lwp *l, const void *v, register_t *retval)
   {
           struct proc *p = l->l_proc;
   
           /*
            * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
            * we use PK_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.
            */
           *retval = (p->p_flag & PK_SUGID) != 0;
           return (0);
   }
   
   /* ARGSUSED */
   int
   sys_setgroups(struct lwp *l, const struct sys_setgroups_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(int) gidsetsize;
                   syscallarg(const gid_t *) gidset;
           } */
           kauth_cred_t ncred;
           int error;
   
           ncred = kauth_cred_alloc();
           error = kauth_cred_setgroups(ncred, SCARG(uap, gidset),
               SCARG(uap, gidsetsize), -1, UIO_USERSPACE);
           if (error != 0) {
                   kauth_cred_free(ncred);
                   return error;
           }
   
           return kauth_proc_setgroups(l, ncred);
   }
   
   /*
    * Get login name, if available.
    */
   /* ARGSUSED */
   int
   sys___getlogin(struct lwp *l, const struct sys___getlogin_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(char *) namebuf;
                   syscallarg(size_t) namelen;
           } */
           struct proc *p = l->l_proc;
           char login[sizeof(p->p_session->s_login)];
           size_t namelen = SCARG(uap, namelen);
   
           if (namelen > sizeof(login))
                   namelen = sizeof(login);
           mutex_enter(&proc_lock);
           memcpy(login, p->p_session->s_login, namelen);
           mutex_exit(&proc_lock);
           return (copyout(login, (void *)SCARG(uap, namebuf), namelen));
   }
   
   /*
    * Set login name.
    */
   /* ARGSUSED */
   int
   sys___setlogin(struct lwp *l, const struct sys___setlogin_args *uap, register_t *retval)
   {
           /* {
                   syscallarg(const char *) namebuf;
           } */
           struct proc *p = l->l_proc;
           struct session *sp;
           char newname[sizeof sp->s_login + 1];
           int error;
   
           if ((error = kauth_authorize_process(l->l_cred, KAUTH_PROCESS_SETID,
               p, NULL, NULL, NULL)) != 0)
                   return (error);
           error = copyinstr(SCARG(uap, namebuf), newname, sizeof newname, NULL);
           if (error != 0)
                   return (error == ENAMETOOLONG ? EINVAL : error);
   
           mutex_enter(&proc_lock);
           sp = p->p_session;
           if (sp->s_flags & S_LOGIN_SET && p->p_pid != sp->s_sid &&
               strncmp(newname, sp->s_login, sizeof sp->s_login) != 0)
                   log(LOG_WARNING, "%s (pid %d) changing logname from "
                       "%.*s to %s\n", p->p_comm, p->p_pid,
                       (int)sizeof sp->s_login, sp->s_login, newname);
           sp->s_flags |= S_LOGIN_SET;
           strncpy(sp->s_login, newname, sizeof sp->s_login);
           mutex_exit(&proc_lock);
           return (0);
   }

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