fs/afs/security.c

   1 /* AFS security handling
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/init.h>
  13 #include <linux/slab.h>
  14 #include <linux/fs.h>
  15 #include <linux/ctype.h>
  16 #include <linux/sched.h>
  17 #include <keys/rxrpc-type.h>
  18 #include "internal.h"
  19
  20 /*
  21  * get a key
  22  */
  23 struct key *afs_request_key(struct afs_cell *cell)
  24 {
  25         struct key *key;
  26
  27         _enter("{%x}", key_serial(cell->anonymous_key));
  28
  29         _debug("key %s", cell->anonymous_key->description);
  30         key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
  31                           NULL);
  32         if (IS_ERR(key)) {
  33                 if (PTR_ERR(key) != -ENOKEY) {
  34                         _leave(" = %ld", PTR_ERR(key));
  35                         return key;
  36                 }
  37
  38                 /* act as anonymous user */
  39                 _leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
  40                 return key_get(cell->anonymous_key);
  41         } else {
  42                 /* act as authorised user */
  43                 _leave(" = {%x} [auth]", key_serial(key));
  44                 return key;
  45         }
  46 }
  47
  48 /*
  49  * dispose of a permits list
  50  */
  51 void afs_zap_permits(struct rcu_head *rcu)
  52 {
  53         struct afs_permits *permits =
  54                 container_of(rcu, struct afs_permits, rcu);
  55         int loop;
  56
  57         _enter("{%d}", permits->count);
  58
  59         for (loop = permits->count - 1; loop >= 0; loop--)
  60                 key_put(permits->permits[loop].key);
  61         kfree(permits);
  62 }
  63
  64 /*
  65  * dispose of a permits list in which all the key pointers have been copied
  66  */
  67 static void afs_dispose_of_permits(struct rcu_head *rcu)
  68 {
  69         struct afs_permits *permits =
  70                 container_of(rcu, struct afs_permits, rcu);
  71
  72         _enter("{%d}", permits->count);
  73
  74         kfree(permits);
  75 }
  76
  77 /*
  78  * get the authorising vnode - this is the specified inode itself if it's a
  79  * directory or it's the parent directory if the specified inode is a file or
  80  * symlink
  81  * - the caller must release the ref on the inode
  82  */
  83 static struct afs_vnode *afs_get_auth_inode(struct afs_vnode *vnode,
  84                                             struct key *key)
  85 {
  86         struct afs_vnode *auth_vnode;
  87         struct inode *auth_inode;
  88
  89         _enter("");
  90
  91         if (S_ISDIR(vnode->vfs_inode.i_mode)) {
  92                 auth_inode = igrab(&vnode->vfs_inode);
  93                 ASSERT(auth_inode != NULL);
  94         } else {
  95                 auth_inode = afs_iget(vnode->vfs_inode.i_sb, key,
  96                                       &vnode->status.parent, NULL, NULL);
  97                 if (IS_ERR(auth_inode))
  98                         return ERR_CAST(auth_inode);
  99         }
 100
 101         auth_vnode = AFS_FS_I(auth_inode);
 102         _leave(" = {%x}", auth_vnode->fid.vnode);
 103         return auth_vnode;
 104 }
 105
 106 /*
 107  * clear the permit cache on a directory vnode
 108  */
 109 void afs_clear_permits(struct afs_vnode *vnode)
 110 {
 111         struct afs_permits *permits;
 112
 113         _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
 114
 115         mutex_lock(&vnode->permits_lock);
 116         permits = vnode->permits;
 117         rcu_assign_pointer(vnode->permits, NULL);
 118         mutex_unlock(&vnode->permits_lock);
 119
 120         if (permits)
 121                 call_rcu(&permits->rcu, afs_zap_permits);
 122         _leave("");
 123 }
 124
 125 /*
 126  * add the result obtained for a vnode to its or its parent directory's cache
 127  * for the key used to access it
 128  */
 129 void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
 130 {
 131         struct afs_permits *permits, *xpermits;
 132         struct afs_permit *permit;
 133         struct afs_vnode *auth_vnode;
 134         int count, loop;
 135
 136         _enter("{%x:%u},%x,%lx",
 137                vnode->fid.vid, vnode->fid.vnode, key_serial(key), acl_order);
 138
 139         auth_vnode = afs_get_auth_inode(vnode, key);
 140         if (IS_ERR(auth_vnode)) {
 141                 _leave(" [get error %ld]", PTR_ERR(auth_vnode));
 142                 return;
 143         }
 144
 145         mutex_lock(&auth_vnode->permits_lock);
 146
 147         /* guard against a rename being detected whilst we waited for the
 148          * lock */
 149         if (memcmp(&auth_vnode->fid, &vnode->status.parent,
 150                    sizeof(struct afs_fid)) != 0) {
 151                 _debug("renamed");
 152                 goto out_unlock;
 153         }
 154
 155         /* have to be careful as the directory's callback may be broken between
 156          * us receiving the status we're trying to cache and us getting the
 157          * lock to update the cache for the status */
 158         if (auth_vnode->acl_order - acl_order > 0) {
 159                 _debug("ACL changed?");
 160                 goto out_unlock;
 161         }
 162
 163         /* always update the anonymous mask */
 164         _debug("anon access %x", vnode->status.anon_access);
 165         auth_vnode->status.anon_access = vnode->status.anon_access;
 166         if (key == vnode->volume->cell->anonymous_key)
 167                 goto out_unlock;
 168
 169         xpermits = auth_vnode->permits;
 170         count = 0;
 171         if (xpermits) {
 172                 /* see if the permit is already in the list
 173                  * - if it is then we just amend the list
 174                  */
 175                 count = xpermits->count;
 176                 permit = xpermits->permits;
 177                 for (loop = count; loop > 0; loop--) {
 178                         if (permit->key == key) {
 179                                 permit->access_mask =
 180                                         vnode->status.caller_access;
 181                                 goto out_unlock;
 182                         }
 183                         permit++;
 184                 }
 185         }
 186
 187         permits = kmalloc(sizeof(*permits) + sizeof(*permit) * (count + 1),
 188                           GFP_NOFS);
 189         if (!permits)
 190                 goto out_unlock;
 191
 192         if (xpermits)
 193                 memcpy(permits->permits, xpermits->permits,
 194                         count * sizeof(struct afs_permit));
 195
 196         _debug("key %x access %x",
 197                key_serial(key), vnode->status.caller_access);
 198         permits->permits[count].access_mask = vnode->status.caller_access;
 199         permits->permits[count].key = key_get(key);
 200         permits->count = count + 1;
 201
 202         rcu_assign_pointer(auth_vnode->permits, permits);
 203         if (xpermits)
 204                 call_rcu(&xpermits->rcu, afs_dispose_of_permits);
 205
 206 out_unlock:
 207         mutex_unlock(&auth_vnode->permits_lock);
 208         iput(&auth_vnode->vfs_inode);
 209         _leave("");
 210 }
 211
 212 /*
 213  * check with the fileserver to see if the directory or parent directory is
 214  * permitted to be accessed with this authorisation, and if so, what access it
 215  * is granted
 216  */
 217 static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
 218                             afs_access_t *_access)
 219 {
 220         struct afs_permits *permits;
 221         struct afs_permit *permit;
 222         struct afs_vnode *auth_vnode;
 223         bool valid;
 224         int loop, ret;
 225
 226         _enter("{%x:%u},%x",
 227                vnode->fid.vid, vnode->fid.vnode, key_serial(key));
 228
 229         auth_vnode = afs_get_auth_inode(vnode, key);
 230         if (IS_ERR(auth_vnode)) {
 231                 *_access = 0;
 232                 _leave(" = %ld", PTR_ERR(auth_vnode));
 233                 return PTR_ERR(auth_vnode);
 234         }
 235
 236         ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));
 237
 238         /* check the permits to see if we've got one yet */
 239         if (key == auth_vnode->volume->cell->anonymous_key) {
 240                 _debug("anon");
 241                 *_access = auth_vnode->status.anon_access;
 242                 valid = true;
 243         } else {
 244                 valid = false;
 245                 rcu_read_lock();
 246                 permits = rcu_dereference(auth_vnode->permits);
 247                 if (permits) {
 248                         permit = permits->permits;
 249                         for (loop = permits->count; loop > 0; loop--) {
 250                                 if (permit->key == key) {
 251                                         _debug("found in cache");
 252                                         *_access = permit->access_mask;
 253                                         valid = true;
 254                                         break;
 255                                 }
 256                                 permit++;
 257                         }
 258                 }
 259                 rcu_read_unlock();
 260         }
 261
 262         if (!valid) {
 263                 /* check the status on the file we're actually interested in
 264                  * (the post-processing will cache the result on auth_vnode) */
 265                 _debug("no valid permit");
 266
 267                 set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
 268                 ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
 269                 if (ret < 0) {
 270                         iput(&auth_vnode->vfs_inode);
 271                         *_access = 0;
 272                         _leave(" = %d", ret);
 273                         return ret;
 274                 }
 275                 *_access = vnode->status.caller_access;
 276         }
 277
 278         iput(&auth_vnode->vfs_inode);
 279         _leave(" = 0 [access %x]", *_access);
 280         return 0;
 281 }
 282
 283 /*
 284  * check the permissions on an AFS file
 285  * - AFS ACLs are attached to directories only, and a file is controlled by its
 286  *   parent directory's ACL
 287  */
 288 int afs_permission(struct inode *inode, int mask)
 289 {
 290         struct afs_vnode *vnode = AFS_FS_I(inode);
 291         afs_access_t uninitialized_var(access);
 292         struct key *key;
 293         int ret;
 294
 295         if (mask & MAY_NOT_BLOCK)
 296                 return -ECHILD;
 297
 298         _enter("{{%x:%u},%lx},%x,",
 299                vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
 300
 301         key = afs_request_key(vnode->volume->cell);
 302         if (IS_ERR(key)) {
 303                 _leave(" = %ld [key]", PTR_ERR(key));
 304                 return PTR_ERR(key);
 305         }
 306
 307         /* if the promise has expired, we need to check the server again */
 308         if (!vnode->cb_promised) {
 309                 _debug("not promised");
 310                 ret = afs_vnode_fetch_status(vnode, NULL, key);
 311                 if (ret < 0)
 312                         goto error;
 313                 _debug("new promise [fl=%lx]", vnode->flags);
 314         }
 315
 316         /* check the permits to see if we've got one yet */
 317         ret = afs_check_permit(vnode, key, &access);
 318         if (ret < 0)
 319                 goto error;
 320
 321         /* interpret the access mask */
 322         _debug("REQ %x ACC %x on %s",
 323                mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
 324
 325         if (S_ISDIR(inode->i_mode)) {
 326                 if (mask & MAY_EXEC) {
 327                         if (!(access & AFS_ACE_LOOKUP))
 328                                 goto permission_denied;
 329                 } else if (mask & MAY_READ) {
 330                         if (!(access & AFS_ACE_READ))
 331                                 goto permission_denied;
 332                 } else if (mask & MAY_WRITE) {
 333                         if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
 334                                         AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
 335                                         AFS_ACE_WRITE))) /* chmod */
 336                                 goto permission_denied;
 337                 } else {
 338                         BUG();
 339                 }
 340         } else {
 341                 if (!(access & AFS_ACE_LOOKUP))
 342                         goto permission_denied;
 343                 if (mask & (MAY_EXEC | MAY_READ)) {
 344                         if (!(access & AFS_ACE_READ))
 345                                 goto permission_denied;
 346                 } else if (mask & MAY_WRITE) {
 347                         if (!(access & AFS_ACE_WRITE))
 348                                 goto permission_denied;
 349                 }
 350         }
 351
 352         key_put(key);
 353         ret = generic_permission(inode, mask);
 354         _leave(" = %d", ret);
 355         return ret;
 356
 357 permission_denied:
 358         ret = -EACCES;
 359 error:
 360         key_put(key);
 361         _leave(" = %d", ret);
 362         return ret;
 363 }