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/11.0/sys/security/mac/mac_process.c 258541 2013-11-25 07:38:45Z attilio $");
   47 
   48 #include "opt_mac.h"
   49 
   50 #include <sys/param.h>
   51 #include <sys/condvar.h>
   52 #include <sys/imgact.h>
   53 #include <sys/kernel.h>
   54 #include <sys/lock.h>
   55 #include <sys/malloc.h>
   56 #include <sys/mac.h>
   57 #include <sys/proc.h>
   58 #include <sys/rwlock.h>
   59 #include <sys/sbuf.h>
   60 #include <sys/sdt.h>
   61 #include <sys/systm.h>
   62 #include <sys/vnode.h>
   63 #include <sys/mount.h>
   64 #include <sys/file.h>
   65 #include <sys/namei.h>
   66 #include <sys/sysctl.h>
   67 
   68 #include <vm/vm.h>
   69 #include <vm/pmap.h>
   70 #include <vm/vm_map.h>
   71 #include <vm/vm_object.h>
   72 
   73 #include <security/mac/mac_framework.h>
   74 #include <security/mac/mac_internal.h>
   75 #include <security/mac/mac_policy.h>
   76 
   77 static int      mac_mmap_revocation = 1;
   78 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
   79     &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
   80     "relabel");
   81 
   82 static int      mac_mmap_revocation_via_cow = 0;
   83 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
   84     &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
   85     "copy-on-write semantics, or by removing all write access");
   86 
   87 static void     mac_proc_vm_revoke_recurse(struct thread *td,
   88                     struct ucred *cred, struct vm_map *map);
   89 
   90 static struct label *
   91 mac_proc_label_alloc(void)
   92 {
   93         struct label *label;
   94 
   95         label = mac_labelzone_alloc(M_WAITOK);
   96         MAC_POLICY_PERFORM(proc_init_label, label);
   97         return (label);
   98 }
   99 
  100 void
  101 mac_proc_init(struct proc *p)
  102 {
  103 
  104         if (mac_labeled & MPC_OBJECT_PROC)
  105                 p->p_label = mac_proc_label_alloc();
  106         else
  107                 p->p_label = NULL;
  108 }
  109 
  110 static void
  111 mac_proc_label_free(struct label *label)
  112 {
  113 
  114         MAC_POLICY_PERFORM_NOSLEEP(proc_destroy_label, label);
  115         mac_labelzone_free(label);
  116 }
  117 
  118 void
  119 mac_proc_destroy(struct proc *p)
  120 {
  121 
  122         if (p->p_label != NULL) {
  123                 mac_proc_label_free(p->p_label);
  124                 p->p_label = NULL;
  125         }
  126 }
  127 
  128 void
  129 mac_thread_userret(struct thread *td)
  130 {
  131 
  132         MAC_POLICY_PERFORM(thread_userret, td);
  133 }
  134 
  135 int
  136 mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
  137 {
  138         struct label *label;
  139         struct mac mac;
  140         char *buffer;
  141         int error;
  142 
  143         if (mac_p == NULL)
  144                 return (0);
  145 
  146         if (!(mac_labeled & MPC_OBJECT_CRED))
  147                 return (EINVAL);
  148 
  149         error = copyin(mac_p, &mac, sizeof(mac));
  150         if (error)
  151                 return (error);
  152 
  153         error = mac_check_structmac_consistent(&mac);
  154         if (error)
  155                 return (error);
  156 
  157         buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
  158         error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
  159         if (error) {
  160                 free(buffer, M_MACTEMP);
  161                 return (error);
  162         }
  163 
  164         label = mac_cred_label_alloc();
  165         error = mac_cred_internalize_label(label, buffer);
  166         free(buffer, M_MACTEMP);
  167         if (error) {
  168                 mac_cred_label_free(label);
  169                 return (error);
  170         }
  171         imgp->execlabel = label;
  172         return (0);
  173 }
  174 
  175 void
  176 mac_execve_exit(struct image_params *imgp)
  177 {
  178         if (imgp->execlabel != NULL) {
  179                 mac_cred_label_free(imgp->execlabel);
  180                 imgp->execlabel = NULL;
  181         }
  182 }
  183 
  184 void
  185 mac_execve_interpreter_enter(struct vnode *interpvp,
  186     struct label **interpvplabel)
  187 {
  188 
  189         if (mac_labeled & MPC_OBJECT_VNODE) {
  190                 *interpvplabel = mac_vnode_label_alloc();
  191                 mac_vnode_copy_label(interpvp->v_label, *interpvplabel);
  192         } else
  193                 *interpvplabel = NULL;
  194 }
  195 
  196 void
  197 mac_execve_interpreter_exit(struct label *interpvplabel)
  198 {
  199 
  200         if (interpvplabel != NULL)
  201                 mac_vnode_label_free(interpvplabel);
  202 }
  203 
  204 /*
  205  * When relabeling a process, call out to the policies for the maximum
  206  * permission allowed for each object type we know about in its memory space,
  207  * and revoke access (in the least surprising ways we know) when necessary.
  208  * The process lock is not held here.
  209  */
  210 void
  211 mac_proc_vm_revoke(struct thread *td)
  212 {
  213         struct ucred *cred;
  214 
  215         PROC_LOCK(td->td_proc);
  216         cred = crhold(td->td_proc->p_ucred);
  217         PROC_UNLOCK(td->td_proc);
  218 
  219         /* XXX freeze all other threads */
  220         mac_proc_vm_revoke_recurse(td, cred,
  221             &td->td_proc->p_vmspace->vm_map);
  222         /* XXX allow other threads to continue */
  223 
  224         crfree(cred);
  225 }
  226 
  227 static __inline const char *
  228 prot2str(vm_prot_t prot)
  229 {
  230 
  231         switch (prot & VM_PROT_ALL) {
  232         case VM_PROT_READ:
  233                 return ("r--");
  234         case VM_PROT_READ | VM_PROT_WRITE:
  235                 return ("rw-");
  236         case VM_PROT_READ | VM_PROT_EXECUTE:
  237                 return ("r-x");
  238         case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
  239                 return ("rwx");
  240         case VM_PROT_WRITE:
  241                 return ("-w-");
  242         case VM_PROT_EXECUTE:
  243                 return ("--x");
  244         case VM_PROT_WRITE | VM_PROT_EXECUTE:
  245                 return ("-wx");
  246         default:
  247                 return ("---");
  248         }
  249 }
  250 
  251 static void
  252 mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
  253     struct vm_map *map)
  254 {
  255         vm_map_entry_t vme;
  256         int result;
  257         vm_prot_t revokeperms;
  258         vm_object_t backing_object, object;
  259         vm_ooffset_t offset;
  260         struct vnode *vp;
  261         struct mount *mp;
  262 
  263         if (!mac_mmap_revocation)
  264                 return;
  265 
  266         vm_map_lock(map);
  267         for (vme = map->header.next; vme != &map->header; vme = vme->next) {
  268                 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
  269                         mac_proc_vm_revoke_recurse(td, cred,
  270                             vme->object.sub_map);
  271                         continue;
  272                 }
  273                 /*
  274                  * Skip over entries that obviously are not shared.
  275                  */
  276                 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
  277                     !vme->max_protection)
  278                         continue;
  279                 /*
  280                  * Drill down to the deepest backing object.
  281                  */
  282                 offset = vme->offset;
  283                 object = vme->object.vm_object;
  284                 if (object == NULL)
  285                         continue;
  286                 VM_OBJECT_RLOCK(object);
  287                 while ((backing_object = object->backing_object) != NULL) {
  288                         VM_OBJECT_RLOCK(backing_object);
  289                         offset += object->backing_object_offset;
  290                         VM_OBJECT_RUNLOCK(object);
  291                         object = backing_object;
  292                 }
  293                 VM_OBJECT_RUNLOCK(object);
  294                 /*
  295                  * At the moment, vm_maps and objects aren't considered by
  296                  * the MAC system, so only things with backing by a normal
  297                  * object (read: vnodes) are checked.
  298                  */
  299                 if (object->type != OBJT_VNODE)
  300                         continue;
  301                 vp = (struct vnode *)object->handle;
  302                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  303                 result = vme->max_protection;
  304                 mac_vnode_check_mmap_downgrade(cred, vp, &result);
  305                 VOP_UNLOCK(vp, 0);
  306                 /*
  307                  * Find out what maximum protection we may be allowing now
  308                  * but a policy needs to get removed.
  309                  */
  310                 revokeperms = vme->max_protection & ~result;
  311                 if (!revokeperms)
  312                         continue;
  313                 printf("pid %ld: revoking %s perms from %#lx:%ld "
  314                     "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
  315                     prot2str(revokeperms), (u_long)vme->start,
  316                     (long)(vme->end - vme->start),
  317                     prot2str(vme->max_protection), prot2str(vme->protection));
  318                 /*
  319                  * This is the really simple case: if a map has more
  320                  * max_protection than is allowed, but it's not being
  321                  * actually used (that is, the current protection is still
  322                  * allowed), we can just wipe it out and do nothing more.
  323                  */
  324                 if ((vme->protection & revokeperms) == 0) {
  325                         vme->max_protection -= revokeperms;
  326                 } else {
  327                         if (revokeperms & VM_PROT_WRITE) {
  328                                 /*
  329                                  * In the more complicated case, flush out all
  330                                  * pending changes to the object then turn it
  331                                  * copy-on-write.
  332                                  */
  333                                 vm_object_reference(object);
  334                                 (void) vn_start_write(vp, &mp, V_WAIT);
  335                                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  336                                 VM_OBJECT_WLOCK(object);
  337                                 vm_object_page_clean(object, offset, offset +
  338                                     vme->end - vme->start, OBJPC_SYNC);
  339                                 VM_OBJECT_WUNLOCK(object);
  340                                 VOP_UNLOCK(vp, 0);
  341                                 vn_finished_write(mp);
  342                                 vm_object_deallocate(object);
  343                                 /*
  344                                  * Why bother if there's no read permissions
  345                                  * anymore?  For the rest, we need to leave
  346                                  * the write permissions on for COW, or
  347                                  * remove them entirely if configured to.
  348                                  */
  349                                 if (!mac_mmap_revocation_via_cow) {
  350                                         vme->max_protection &= ~VM_PROT_WRITE;
  351                                         vme->protection &= ~VM_PROT_WRITE;
  352                                 } if ((revokeperms & VM_PROT_READ) == 0)
  353                                         vme->eflags |= MAP_ENTRY_COW |
  354                                             MAP_ENTRY_NEEDS_COPY;
  355                         }
  356                         if (revokeperms & VM_PROT_EXECUTE) {
  357                                 vme->max_protection &= ~VM_PROT_EXECUTE;
  358                                 vme->protection &= ~VM_PROT_EXECUTE;
  359                         }
  360                         if (revokeperms & VM_PROT_READ) {
  361                                 vme->max_protection = 0;
  362                                 vme->protection = 0;
  363                         }
  364                         pmap_protect(map->pmap, vme->start, vme->end,
  365                             vme->protection & ~revokeperms);
  366                         vm_map_simplify_entry(map, vme);
  367                 }
  368         }
  369         vm_map_unlock(map);
  370 }
  371 
  372 MAC_CHECK_PROBE_DEFINE2(proc_check_debug, "struct ucred *", "struct proc *");
  373 
  374 int
  375 mac_proc_check_debug(struct ucred *cred, struct proc *p)
  376 {
  377         int error;
  378 
  379         PROC_LOCK_ASSERT(p, MA_OWNED);
  380 
  381         MAC_POLICY_CHECK_NOSLEEP(proc_check_debug, cred, p);
  382         MAC_CHECK_PROBE2(proc_check_debug, error, cred, p);
  383 
  384         return (error);
  385 }
  386 
  387 MAC_CHECK_PROBE_DEFINE2(proc_check_sched, "struct ucred *", "struct proc *");
  388 
  389 int
  390 mac_proc_check_sched(struct ucred *cred, struct proc *p)
  391 {
  392         int error;
  393 
  394         PROC_LOCK_ASSERT(p, MA_OWNED);
  395 
  396         MAC_POLICY_CHECK_NOSLEEP(proc_check_sched, cred, p);
  397         MAC_CHECK_PROBE2(proc_check_sched, error, cred, p);
  398 
  399         return (error);
  400 }
  401 
  402 MAC_CHECK_PROBE_DEFINE3(proc_check_signal, "struct ucred *", "struct proc *",
  403     "int");
  404 
  405 int
  406 mac_proc_check_signal(struct ucred *cred, struct proc *p, int signum)
  407 {
  408         int error;
  409 
  410         PROC_LOCK_ASSERT(p, MA_OWNED);
  411 
  412         MAC_POLICY_CHECK_NOSLEEP(proc_check_signal, cred, p, signum);
  413         MAC_CHECK_PROBE3(proc_check_signal, error, cred, p, signum);
  414 
  415         return (error);
  416 }
  417 
  418 MAC_CHECK_PROBE_DEFINE2(proc_check_wait, "struct ucred *", "struct proc *");
  419 
  420 int
  421 mac_proc_check_wait(struct ucred *cred, struct proc *p)
  422 {
  423         int error;
  424 
  425         PROC_LOCK_ASSERT(p, MA_OWNED);
  426 
  427         MAC_POLICY_CHECK_NOSLEEP(proc_check_wait, cred, p);
  428         MAC_CHECK_PROBE2(proc_check_wait, error, cred, p);
  429 
  430         return (error);
  431 }

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