/* AFS security handling
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/ctype.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
/*
* get a key
*/
struct key *afs_request_key(struct afs_cell *cell)
{
struct key *key;
_enter("{%x}", key_serial(cell->anonymous_key));
_debug("key %s", cell->anonymous_key->description);
key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
NULL);
if (IS_ERR(key)) {
if (PTR_ERR(key) != -ENOKEY) {
_leave(" = %ld", PTR_ERR(key));
return key;
}
/* act as anonymous user */
_leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
return key_get(cell->anonymous_key);
} else {
/* act as authorised user */
_leave(" = {%x} [auth]", key_serial(key));
return key;
}
}
/*
* dispose of a permits list
*/
void afs_zap_permits(struct rcu_head *rcu)
{
struct afs_permits *permits =
container_of(rcu, struct afs_permits, rcu);
int loop;
_enter("{%d}", permits->count);
for (loop = permits->count - 1; loop >= 0; loop--)
key_put(permits->permits[loop].key);
kfree(permits);
}
/*
* dispose of a permits list in which all the key pointers have been copied
*/
static void afs_dispose_of_permits(struct rcu_head *rcu)
{
struct afs_permits *permits =
container_of(rcu, struct afs_permits, rcu);
_enter("{%d}", permits->count);
kfree(permits);
}
/*
* get the authorising vnode - this is the specified inode itself if it's a
* directory or it's the parent directory if the specified inode is a file or
* symlink
* - the caller must release the ref on the inode
*/
static struct afs_vnode *afs_get_auth_inode(struct afs_vnode *vnode,
struct key *key)
{
struct afs_vnode *auth_vnode;
struct inode *auth_inode;
_enter("");
if (S_ISDIR(vnode->vfs_inode.i_mode)) {
auth_inode = igrab(&vnode->vfs_inode);
ASSERT(auth_inode != NULL);
} else {
auth_inode = afs_iget(vnode->vfs_inode.i_sb, key,
&vnode->status.parent);
if (IS_ERR(auth_inode))
return ERR_PTR(PTR_ERR(auth_inode));
}
auth_vnode = AFS_FS_I(auth_inode);
_leave(" = {%x}", auth_vnode->fid.vnode);
return auth_vnode;
}
/*
* clear the permit cache on a directory vnode
*/
void afs_clear_permits(struct afs_vnode *vnode)
{
struct afs_permits *permits;
_enter("{%x}", vnode->fid.vnode);
mutex_lock(&vnode->permits_lock);
permits = vnode->permits;
rcu_assign_pointer(vnode->permits, NULL);
mutex_unlock(&vnode->permits_lock);
if (permits)
call_rcu(&permits->rcu, afs_zap_permits);
_leave("");
}
/*
* add the result obtained for a vnode to its or its parent directory's cache
* for the key used to access it
*/
void afs_cache_permit(struct afs_vnode *vnode, struct key *key, long acl_order)
{
struct afs_permits *permits, *xpermits;
struct afs_permit *permit;
struct afs_vnode *auth_vnode;
int count, loop;
_enter("{%x},%x,%lx", vnode->fid.vnode, key_serial(key), acl_order);
auth_vnode = afs_get_auth_inode(vnode, key);
if (IS_ERR(auth_vnode)) {
_leave(" [get error %ld]", PTR_ERR(auth_vnode));
return;
}
mutex_lock(&auth_vnode->permits_lock);
/* guard against a rename being detected whilst we waited for the
* lock */
if (memcmp(&auth_vnode->fid, &vnode->status.parent,
sizeof(struct afs_fid)) != 0) {
_debug("renamed");
goto out_unlock;
}
/* have to be careful as the directory's callback may be broken between
* us receiving the status we're trying to cache and us getting the
* lock to update the cache for the status */
if (auth_vnode->acl_order - acl_order > 0) {
_debug("ACL changed?");
goto out_unlock;
}
/* always update the anonymous mask */
_debug("anon access %x", vnode->status.anon_access);
auth_vnode->status.anon_access = vnode->status.anon_access;
if (key == vnode->volume->cell->anonymous_key)
goto out_unlock;
xpermits = auth_vnode->permits;
count = 0;
if (xpermits) {
/* see if the permit is already in the list
* - if it is then we just amend the list
*/
count = xpermits->count;
permit = xpermits->permits;
for (loop = count; loop > 0; loop--) {
if (permit->key == key) {
permit->access_mask =
vnode->status.caller_access;
goto out_unlock;
}
permit++;
}
}
permits = kmalloc(sizeof(*permits) + sizeof(*permit) * (count + 1),
GFP_NOFS);
if (!permits)
goto out_unlock;
memcpy(permits->permits, xpermits->permits,
count * sizeof(struct afs_permit));
_debug("key %x access %x",
key_serial(key), vnode->status.caller_access);
permits->permits[count].access_mask = vnode->status.caller_access;
permits->permits[count].key = key_get(key);
permits->count = count + 1;
rcu_assign_pointer(auth_vnode->permits, permits);
if (xpermits)
call_rcu(&xpermits->rcu, afs_dispose_of_permits);
out_unlock:
mutex_unlock(&auth_vnode->permits_lock);
iput(&auth_vnode->vfs_inode);
_leave("");
}
/*
* check with the fileserver to see if the directory or parent directory is
* permitted to be accessed with this authorisation, and if so, what access it
* is granted
*/
static int afs_check_permit(struct afs_vnode *vnode, struct key *key,
afs_access_t *_access)
{
struct afs_permits *permits;
struct afs_permit *permit;
struct afs_vnode *auth_vnode;
bool valid;
int loop, ret;
_enter("");
auth_vnode = afs_get_auth_inode(vnode, key);
if (IS_ERR(auth_vnode)) {
*_access = 0;
_leave(" = %ld", PTR_ERR(auth_vnode));
return PTR_ERR(auth_vnode);
}
ASSERT(S_ISDIR(auth_vnode->vfs_inode.i_mode));
/* check the permits to see if we've got one yet */
if (key == auth_vnode->volume->cell->anonymous_key) {
_debug("anon");
*_access = auth_vnode->status.anon_access;
valid = true;
} else {
valid = false;
rcu_read_lock();
permits = rcu_dereference(auth_vnode->permits);
if (permits) {
permit = permits->permits;
for (loop = permits->count; loop > 0; loop--) {
if (permit->key == key) {
_debug("found in cache");
*_access = permit->access_mask;
valid = true;
break;
}
permit++;
}
}
rcu_read_unlock();
}
if (!valid) {
/* check the status on the file we're actually interested in
* (the post-processing will cache the result on auth_vnode) */
_debug("no valid permit");
set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
ret = afs_vnode_fetch_status(vnode, auth_vnode, key);
if (ret < 0) {
iput(&auth_vnode->vfs_inode);
*_access = 0;
_leave(" = %d", ret);
return ret;
}
}
*_access = vnode->status.caller_access;
iput(&auth_vnode->vfs_inode);
_leave(" = 0 [access %x]", *_access);
return 0;
}
/*
* check the permissions on an AFS file
* - AFS ACLs are attached to directories only, and a file is controlled by its
* parent directory's ACL
*/
int afs_permission(struct inode *inode, int mask, struct nameidata *nd)
{
struct afs_vnode *vnode = AFS_FS_I(inode);
afs_access_t access;
struct key *key;
int ret;
_enter("{%x:%x},%x,", vnode->fid.vid, vnode->fid.vnode, mask);
key = afs_request_key(vnode->volume->cell);
if (IS_ERR(key)) {
_leave(" = %ld [key]", PTR_ERR(key));
return PTR_ERR(key);
}
/* check the permits to see if we've got one yet */
ret = afs_check_permit(vnode, key, &access);
if (ret < 0) {
key_put(key);
_leave(" = %d [check]", ret);
return ret;
}
/* interpret the access mask */
_debug("REQ %x ACC %x on %s",
mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
if (S_ISDIR(inode->i_mode)) {
if (mask & MAY_EXEC) {
if (!(access & AFS_ACE_LOOKUP))
goto permission_denied;
} else if (mask & MAY_READ) {
if (!(access & AFS_ACE_READ))
goto permission_denied;
} else if (mask & MAY_WRITE) {
if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
AFS_ACE_INSERT | /* create, mkdir, symlink, rename to */
AFS_ACE_WRITE))) /* chmod */
goto permission_denied;
} else {
BUG();
}
} else {
if (!(access & AFS_ACE_LOOKUP))
goto permission_denied;
if (mask & (MAY_EXEC | MAY_READ)) {
if (!(access & AFS_ACE_READ))
goto permission_denied;
} else if (mask & MAY_WRITE) {
if (!(access & AFS_ACE_WRITE))
goto permission_denied;
}
}
key_put(key);
return generic_permission(inode, mask, NULL);
permission_denied:
key_put(key);
_leave(" = -EACCES");
return -EACCES;
}
