The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/security/mac/mac_process.c

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    1 /*-
    2  * Copyright (c) 1999-2002, 2008-2009 Robert N. M. Watson
    3  * Copyright (c) 2001 Ilmar S. Habibulin
    4  * Copyright (c) 2001-2003 Networks Associates Technology, Inc.
    5  * Copyright (c) 2006 SPARTA, Inc.
    6  * Copyright (c) 2008 Apple Inc.
    7  * All rights reserved.
    8  *
    9  * This software was developed by Robert Watson and Ilmar Habibulin for the
   10  * TrustedBSD Project.
   11  *
   12  * This software was developed for the FreeBSD Project in part by Network
   13  * Associates Laboratories, the Security Research Division of Network
   14  * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
   15  * as part of the DARPA CHATS research program.
   16  *
   17  * This software was enhanced by SPARTA ISSO under SPAWAR contract
   18  * N66001-04-C-6019 ("SEFOS").
   19  *
   20  * This software was developed at the University of Cambridge Computer
   21  * Laboratory with support from a grant from Google, Inc.
   22  *
   23  * Redistribution and use in source and binary forms, with or without
   24  * modification, are permitted provided that the following conditions
   25  * are met:
   26  * 1. Redistributions of source code must retain the above copyright
   27  *    notice, this list of conditions and the following disclaimer.
   28  * 2. Redistributions in binary form must reproduce the above copyright
   29  *    notice, this list of conditions and the following disclaimer in the
   30  *    documentation and/or other materials provided with the distribution.
   31  *
   32  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   33  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   34  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   35  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   36  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   37  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   38  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   39  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   40  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   41  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   42  * SUCH DAMAGE.
   43  */
   44 
   45 #include <sys/cdefs.h>
   46 __FBSDID("$FreeBSD: releng/8.3/sys/security/mac/mac_process.c 191731 2009-05-01 21:05:40Z rwatson $");
   47 
   48 #include "opt_kdtrace.h"
   49 #include "opt_mac.h"
   50 
   51 #include <sys/param.h>
   52 #include <sys/condvar.h>
   53 #include <sys/imgact.h>
   54 #include <sys/kernel.h>
   55 #include <sys/lock.h>
   56 #include <sys/malloc.h>
   57 #include <sys/mutex.h>
   58 #include <sys/mac.h>
   59 #include <sys/proc.h>
   60 #include <sys/sbuf.h>
   61 #include <sys/sdt.h>
   62 #include <sys/systm.h>
   63 #include <sys/vnode.h>
   64 #include <sys/mount.h>
   65 #include <sys/file.h>
   66 #include <sys/namei.h>
   67 #include <sys/sysctl.h>
   68 
   69 #include <vm/vm.h>
   70 #include <vm/pmap.h>
   71 #include <vm/vm_map.h>
   72 #include <vm/vm_object.h>
   73 
   74 #include <security/mac/mac_framework.h>
   75 #include <security/mac/mac_internal.h>
   76 #include <security/mac/mac_policy.h>
   77 
   78 static int      mac_mmap_revocation = 1;
   79 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
   80     &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
   81     "relabel");
   82 
   83 static int      mac_mmap_revocation_via_cow = 0;
   84 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
   85     &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
   86     "copy-on-write semantics, or by removing all write access");
   87 
   88 static void     mac_proc_vm_revoke_recurse(struct thread *td,
   89                     struct ucred *cred, struct vm_map *map);
   90 
   91 static struct label *
   92 mac_proc_label_alloc(void)
   93 {
   94         struct label *label;
   95 
   96         label = mac_labelzone_alloc(M_WAITOK);
   97         MAC_POLICY_PERFORM(proc_init_label, label);
   98         return (label);
   99 }
  100 
  101 void
  102 mac_proc_init(struct proc *p)
  103 {
  104 
  105         if (mac_labeled & MPC_OBJECT_PROC)
  106                 p->p_label = mac_proc_label_alloc();
  107         else
  108                 p->p_label = NULL;
  109 }
  110 
  111 static void
  112 mac_proc_label_free(struct label *label)
  113 {
  114 
  115         MAC_POLICY_PERFORM_NOSLEEP(proc_destroy_label, label);
  116         mac_labelzone_free(label);
  117 }
  118 
  119 void
  120 mac_proc_destroy(struct proc *p)
  121 {
  122 
  123         if (p->p_label != NULL) {
  124                 mac_proc_label_free(p->p_label);
  125                 p->p_label = NULL;
  126         }
  127 }
  128 
  129 void
  130 mac_thread_userret(struct thread *td)
  131 {
  132 
  133         MAC_POLICY_PERFORM(thread_userret, td);
  134 }
  135 
  136 int
  137 mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
  138 {
  139         struct label *label;
  140         struct mac mac;
  141         char *buffer;
  142         int error;
  143 
  144         if (mac_p == NULL)
  145                 return (0);
  146 
  147         if (!(mac_labeled & MPC_OBJECT_CRED))
  148                 return (EINVAL);
  149 
  150         error = copyin(mac_p, &mac, sizeof(mac));
  151         if (error)
  152                 return (error);
  153 
  154         error = mac_check_structmac_consistent(&mac);
  155         if (error)
  156                 return (error);
  157 
  158         buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
  159         error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
  160         if (error) {
  161                 free(buffer, M_MACTEMP);
  162                 return (error);
  163         }
  164 
  165         label = mac_cred_label_alloc();
  166         error = mac_cred_internalize_label(label, buffer);
  167         free(buffer, M_MACTEMP);
  168         if (error) {
  169                 mac_cred_label_free(label);
  170                 return (error);
  171         }
  172         imgp->execlabel = label;
  173         return (0);
  174 }
  175 
  176 void
  177 mac_execve_exit(struct image_params *imgp)
  178 {
  179         if (imgp->execlabel != NULL) {
  180                 mac_cred_label_free(imgp->execlabel);
  181                 imgp->execlabel = NULL;
  182         }
  183 }
  184 
  185 void
  186 mac_execve_interpreter_enter(struct vnode *interpvp,
  187     struct label **interpvplabel)
  188 {
  189 
  190         if (mac_labeled & MPC_OBJECT_VNODE) {
  191                 *interpvplabel = mac_vnode_label_alloc();
  192                 mac_vnode_copy_label(interpvp->v_label, *interpvplabel);
  193         } else
  194                 *interpvplabel = NULL;
  195 }
  196 
  197 void
  198 mac_execve_interpreter_exit(struct label *interpvplabel)
  199 {
  200 
  201         if (interpvplabel != NULL)
  202                 mac_vnode_label_free(interpvplabel);
  203 }
  204 
  205 /*
  206  * When relabeling a process, call out to the policies for the maximum
  207  * permission allowed for each object type we know about in its memory space,
  208  * and revoke access (in the least surprising ways we know) when necessary.
  209  * The process lock is not held here.
  210  */
  211 void
  212 mac_proc_vm_revoke(struct thread *td)
  213 {
  214         struct ucred *cred;
  215 
  216         PROC_LOCK(td->td_proc);
  217         cred = crhold(td->td_proc->p_ucred);
  218         PROC_UNLOCK(td->td_proc);
  219 
  220         /* XXX freeze all other threads */
  221         mac_proc_vm_revoke_recurse(td, cred,
  222             &td->td_proc->p_vmspace->vm_map);
  223         /* XXX allow other threads to continue */
  224 
  225         crfree(cred);
  226 }
  227 
  228 static __inline const char *
  229 prot2str(vm_prot_t prot)
  230 {
  231 
  232         switch (prot & VM_PROT_ALL) {
  233         case VM_PROT_READ:
  234                 return ("r--");
  235         case VM_PROT_READ | VM_PROT_WRITE:
  236                 return ("rw-");
  237         case VM_PROT_READ | VM_PROT_EXECUTE:
  238                 return ("r-x");
  239         case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
  240                 return ("rwx");
  241         case VM_PROT_WRITE:
  242                 return ("-w-");
  243         case VM_PROT_EXECUTE:
  244                 return ("--x");
  245         case VM_PROT_WRITE | VM_PROT_EXECUTE:
  246                 return ("-wx");
  247         default:
  248                 return ("---");
  249         }
  250 }
  251 
  252 static void
  253 mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
  254     struct vm_map *map)
  255 {
  256         vm_map_entry_t vme;
  257         int vfslocked, result;
  258         vm_prot_t revokeperms;
  259         vm_object_t backing_object, object;
  260         vm_ooffset_t offset;
  261         struct vnode *vp;
  262         struct mount *mp;
  263 
  264         if (!mac_mmap_revocation)
  265                 return;
  266 
  267         vm_map_lock(map);
  268         for (vme = map->header.next; vme != &map->header; vme = vme->next) {
  269                 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
  270                         mac_proc_vm_revoke_recurse(td, cred,
  271                             vme->object.sub_map);
  272                         continue;
  273                 }
  274                 /*
  275                  * Skip over entries that obviously are not shared.
  276                  */
  277                 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
  278                     !vme->max_protection)
  279                         continue;
  280                 /*
  281                  * Drill down to the deepest backing object.
  282                  */
  283                 offset = vme->offset;
  284                 object = vme->object.vm_object;
  285                 if (object == NULL)
  286                         continue;
  287                 VM_OBJECT_LOCK(object);
  288                 while ((backing_object = object->backing_object) != NULL) {
  289                         VM_OBJECT_LOCK(backing_object);
  290                         offset += object->backing_object_offset;
  291                         VM_OBJECT_UNLOCK(object);
  292                         object = backing_object;
  293                 }
  294                 VM_OBJECT_UNLOCK(object);
  295                 /*
  296                  * At the moment, vm_maps and objects aren't considered by
  297                  * the MAC system, so only things with backing by a normal
  298                  * object (read: vnodes) are checked.
  299                  */
  300                 if (object->type != OBJT_VNODE)
  301                         continue;
  302                 vp = (struct vnode *)object->handle;
  303                 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
  304                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  305                 result = vme->max_protection;
  306                 mac_vnode_check_mmap_downgrade(cred, vp, &result);
  307                 VOP_UNLOCK(vp, 0);
  308                 /*
  309                  * Find out what maximum protection we may be allowing now
  310                  * but a policy needs to get removed.
  311                  */
  312                 revokeperms = vme->max_protection & ~result;
  313                 if (!revokeperms) {
  314                         VFS_UNLOCK_GIANT(vfslocked);
  315                         continue;
  316                 }
  317                 printf("pid %ld: revoking %s perms from %#lx:%ld "
  318                     "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
  319                     prot2str(revokeperms), (u_long)vme->start,
  320                     (long)(vme->end - vme->start),
  321                     prot2str(vme->max_protection), prot2str(vme->protection));
  322                 /*
  323                  * This is the really simple case: if a map has more
  324                  * max_protection than is allowed, but it's not being
  325                  * actually used (that is, the current protection is still
  326                  * allowed), we can just wipe it out and do nothing more.
  327                  */
  328                 if ((vme->protection & revokeperms) == 0) {
  329                         vme->max_protection -= revokeperms;
  330                 } else {
  331                         if (revokeperms & VM_PROT_WRITE) {
  332                                 /*
  333                                  * In the more complicated case, flush out all
  334                                  * pending changes to the object then turn it
  335                                  * copy-on-write.
  336                                  */
  337                                 vm_object_reference(object);
  338                                 (void) vn_start_write(vp, &mp, V_WAIT);
  339                                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  340                                 VM_OBJECT_LOCK(object);
  341                                 vm_object_page_clean(object,
  342                                     OFF_TO_IDX(offset),
  343                                     OFF_TO_IDX(offset + vme->end - vme->start +
  344                                         PAGE_MASK),
  345                                     OBJPC_SYNC);
  346                                 VM_OBJECT_UNLOCK(object);
  347                                 VOP_UNLOCK(vp, 0);
  348                                 vn_finished_write(mp);
  349                                 vm_object_deallocate(object);
  350                                 /*
  351                                  * Why bother if there's no read permissions
  352                                  * anymore?  For the rest, we need to leave
  353                                  * the write permissions on for COW, or
  354                                  * remove them entirely if configured to.
  355                                  */
  356                                 if (!mac_mmap_revocation_via_cow) {
  357                                         vme->max_protection &= ~VM_PROT_WRITE;
  358                                         vme->protection &= ~VM_PROT_WRITE;
  359                                 } if ((revokeperms & VM_PROT_READ) == 0)
  360                                         vme->eflags |= MAP_ENTRY_COW |
  361                                             MAP_ENTRY_NEEDS_COPY;
  362                         }
  363                         if (revokeperms & VM_PROT_EXECUTE) {
  364                                 vme->max_protection &= ~VM_PROT_EXECUTE;
  365                                 vme->protection &= ~VM_PROT_EXECUTE;
  366                         }
  367                         if (revokeperms & VM_PROT_READ) {
  368                                 vme->max_protection = 0;
  369                                 vme->protection = 0;
  370                         }
  371                         pmap_protect(map->pmap, vme->start, vme->end,
  372                             vme->protection & ~revokeperms);
  373                         vm_map_simplify_entry(map, vme);
  374                 }
  375                 VFS_UNLOCK_GIANT(vfslocked);
  376         }
  377         vm_map_unlock(map);
  378 }
  379 
  380 MAC_CHECK_PROBE_DEFINE2(proc_check_debug, "struct ucred *", "struct proc *");
  381 
  382 int
  383 mac_proc_check_debug(struct ucred *cred, struct proc *p)
  384 {
  385         int error;
  386 
  387         PROC_LOCK_ASSERT(p, MA_OWNED);
  388 
  389         MAC_POLICY_CHECK_NOSLEEP(proc_check_debug, cred, p);
  390         MAC_CHECK_PROBE2(proc_check_debug, error, cred, p);
  391 
  392         return (error);
  393 }
  394 
  395 MAC_CHECK_PROBE_DEFINE2(proc_check_sched, "struct ucred *", "struct proc *");
  396 
  397 int
  398 mac_proc_check_sched(struct ucred *cred, struct proc *p)
  399 {
  400         int error;
  401 
  402         PROC_LOCK_ASSERT(p, MA_OWNED);
  403 
  404         MAC_POLICY_CHECK_NOSLEEP(proc_check_sched, cred, p);
  405         MAC_CHECK_PROBE2(proc_check_sched, error, cred, p);
  406 
  407         return (error);
  408 }
  409 
  410 MAC_CHECK_PROBE_DEFINE3(proc_check_signal, "struct ucred *", "struct proc *",
  411     "int");
  412 
  413 int
  414 mac_proc_check_signal(struct ucred *cred, struct proc *p, int signum)
  415 {
  416         int error;
  417 
  418         PROC_LOCK_ASSERT(p, MA_OWNED);
  419 
  420         MAC_POLICY_CHECK_NOSLEEP(proc_check_signal, cred, p, signum);
  421         MAC_CHECK_PROBE3(proc_check_signal, error, cred, p, signum);
  422 
  423         return (error);
  424 }
  425 
  426 MAC_CHECK_PROBE_DEFINE2(proc_check_wait, "struct ucred *", "struct proc *");
  427 
  428 int
  429 mac_proc_check_wait(struct ucred *cred, struct proc *p)
  430 {
  431         int error;
  432 
  433         PROC_LOCK_ASSERT(p, MA_OWNED);
  434 
  435         MAC_POLICY_CHECK_NOSLEEP(proc_check_wait, cred, p);
  436         MAC_CHECK_PROBE2(proc_check_wait, error, cred, p);
  437 
  438         return (error);
  439 }

Cache object: a338729238c3b705c5f0d426f75d3564


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