diff options
Diffstat (limited to 'fs/afs/security.c')
| -rw-r--r-- | fs/afs/security.c | 487 |
1 files changed, 487 insertions, 0 deletions
diff --git a/fs/afs/security.c b/fs/afs/security.c new file mode 100644 index 000000000..7c6a63a30 --- /dev/null +++ b/fs/afs/security.c @@ -0,0 +1,487 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* AFS security handling + * + * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/ctype.h> +#include <linux/sched.h> +#include <linux/hashtable.h> +#include <keys/rxrpc-type.h> +#include "internal.h" + +static DEFINE_HASHTABLE(afs_permits_cache, 10); +static DEFINE_SPINLOCK(afs_permits_lock); + +/* + * 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_net(&key_type_rxrpc, cell->anonymous_key->description, + cell->net->net, 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; + } +} + +/* + * Get a key when pathwalk is in rcuwalk mode. + */ +struct key *afs_request_key_rcu(struct afs_cell *cell) +{ + struct key *key; + + _enter("{%x}", key_serial(cell->anonymous_key)); + + _debug("key %s", cell->anonymous_key->description); + key = request_key_net_rcu(&key_type_rxrpc, + cell->anonymous_key->description, + cell->net->net); + 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 list of permits. + */ +static void afs_permits_rcu(struct rcu_head *rcu) +{ + struct afs_permits *permits = + container_of(rcu, struct afs_permits, rcu); + int i; + + for (i = 0; i < permits->nr_permits; i++) + key_put(permits->permits[i].key); + kfree(permits); +} + +/* + * Discard a permission cache. + */ +void afs_put_permits(struct afs_permits *permits) +{ + if (permits && refcount_dec_and_test(&permits->usage)) { + spin_lock(&afs_permits_lock); + hash_del_rcu(&permits->hash_node); + spin_unlock(&afs_permits_lock); + call_rcu(&permits->rcu, afs_permits_rcu); + } +} + +/* + * Clear a permit cache on callback break. + */ +void afs_clear_permits(struct afs_vnode *vnode) +{ + struct afs_permits *permits; + + spin_lock(&vnode->lock); + permits = rcu_dereference_protected(vnode->permit_cache, + lockdep_is_held(&vnode->lock)); + RCU_INIT_POINTER(vnode->permit_cache, NULL); + spin_unlock(&vnode->lock); + + afs_put_permits(permits); +} + +/* + * Hash a list of permits. Use simple addition to make it easy to add an extra + * one at an as-yet indeterminate position in the list. + */ +static void afs_hash_permits(struct afs_permits *permits) +{ + unsigned long h = permits->nr_permits; + int i; + + for (i = 0; i < permits->nr_permits; i++) { + h += (unsigned long)permits->permits[i].key / sizeof(void *); + h += permits->permits[i].access; + } + + permits->h = h; +} + +/* + * Cache the CallerAccess result obtained from doing a fileserver operation + * that returned a vnode status for a particular key. If a callback break + * occurs whilst the operation was in progress then we have to ditch the cache + * as the ACL *may* have changed. + */ +void afs_cache_permit(struct afs_vnode *vnode, struct key *key, + unsigned int cb_break, struct afs_status_cb *scb) +{ + struct afs_permits *permits, *xpermits, *replacement, *zap, *new = NULL; + afs_access_t caller_access = scb->status.caller_access; + size_t size = 0; + bool changed = false; + int i, j; + + _enter("{%llx:%llu},%x,%x", + vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access); + + rcu_read_lock(); + + /* Check for the common case first: We got back the same access as last + * time we tried and already have it recorded. + */ + permits = rcu_dereference(vnode->permit_cache); + if (permits) { + if (!permits->invalidated) { + for (i = 0; i < permits->nr_permits; i++) { + if (permits->permits[i].key < key) + continue; + if (permits->permits[i].key > key) + break; + if (permits->permits[i].access != caller_access) { + changed = true; + break; + } + + if (afs_cb_is_broken(cb_break, vnode)) { + changed = true; + break; + } + + /* The cache is still good. */ + rcu_read_unlock(); + return; + } + } + + changed |= permits->invalidated; + size = permits->nr_permits; + + /* If this set of permits is now wrong, clear the permits + * pointer so that no one tries to use the stale information. + */ + if (changed) { + spin_lock(&vnode->lock); + if (permits != rcu_access_pointer(vnode->permit_cache)) + goto someone_else_changed_it_unlock; + RCU_INIT_POINTER(vnode->permit_cache, NULL); + spin_unlock(&vnode->lock); + + afs_put_permits(permits); + permits = NULL; + size = 0; + } + } + + if (afs_cb_is_broken(cb_break, vnode)) + goto someone_else_changed_it; + + /* We need a ref on any permits list we want to copy as we'll have to + * drop the lock to do memory allocation. + */ + if (permits && !refcount_inc_not_zero(&permits->usage)) + goto someone_else_changed_it; + + rcu_read_unlock(); + + /* Speculatively create a new list with the revised permission set. We + * discard this if we find an extant match already in the hash, but + * it's easier to compare with memcmp this way. + * + * We fill in the key pointers at this time, but we don't get the refs + * yet. + */ + size++; + new = kzalloc(struct_size(new, permits, size), GFP_NOFS); + if (!new) + goto out_put; + + refcount_set(&new->usage, 1); + new->nr_permits = size; + i = j = 0; + if (permits) { + for (i = 0; i < permits->nr_permits; i++) { + if (j == i && permits->permits[i].key > key) { + new->permits[j].key = key; + new->permits[j].access = caller_access; + j++; + } + new->permits[j].key = permits->permits[i].key; + new->permits[j].access = permits->permits[i].access; + j++; + } + } + + if (j == i) { + new->permits[j].key = key; + new->permits[j].access = caller_access; + } + + afs_hash_permits(new); + + /* Now see if the permit list we want is actually already available */ + spin_lock(&afs_permits_lock); + + hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) { + if (xpermits->h != new->h || + xpermits->invalidated || + xpermits->nr_permits != new->nr_permits || + memcmp(xpermits->permits, new->permits, + new->nr_permits * sizeof(struct afs_permit)) != 0) + continue; + + if (refcount_inc_not_zero(&xpermits->usage)) { + replacement = xpermits; + goto found; + } + + break; + } + + for (i = 0; i < new->nr_permits; i++) + key_get(new->permits[i].key); + hash_add_rcu(afs_permits_cache, &new->hash_node, new->h); + replacement = new; + new = NULL; + +found: + spin_unlock(&afs_permits_lock); + + kfree(new); + + rcu_read_lock(); + spin_lock(&vnode->lock); + zap = rcu_access_pointer(vnode->permit_cache); + if (!afs_cb_is_broken(cb_break, vnode) && zap == permits) + rcu_assign_pointer(vnode->permit_cache, replacement); + else + zap = replacement; + spin_unlock(&vnode->lock); + rcu_read_unlock(); + afs_put_permits(zap); +out_put: + afs_put_permits(permits); + return; + +someone_else_changed_it_unlock: + spin_unlock(&vnode->lock); +someone_else_changed_it: + /* Someone else changed the cache under us - don't recheck at this + * time. + */ + rcu_read_unlock(); + return; +} + +static bool afs_check_permit_rcu(struct afs_vnode *vnode, struct key *key, + afs_access_t *_access) +{ + const struct afs_permits *permits; + int i; + + _enter("{%llx:%llu},%x", + vnode->fid.vid, vnode->fid.vnode, key_serial(key)); + + /* check the permits to see if we've got one yet */ + if (key == vnode->volume->cell->anonymous_key) { + *_access = vnode->status.anon_access; + _leave(" = t [anon %x]", *_access); + return true; + } + + permits = rcu_dereference(vnode->permit_cache); + if (permits) { + for (i = 0; i < permits->nr_permits; i++) { + if (permits->permits[i].key < key) + continue; + if (permits->permits[i].key > key) + break; + + *_access = permits->permits[i].access; + _leave(" = %u [perm %x]", !permits->invalidated, *_access); + return !permits->invalidated; + } + } + + _leave(" = f"); + return false; +} + +/* + * 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 + */ +int afs_check_permit(struct afs_vnode *vnode, struct key *key, + afs_access_t *_access) +{ + struct afs_permits *permits; + bool valid = false; + int i, ret; + + _enter("{%llx:%llu},%x", + vnode->fid.vid, vnode->fid.vnode, key_serial(key)); + + /* check the permits to see if we've got one yet */ + if (key == vnode->volume->cell->anonymous_key) { + _debug("anon"); + *_access = vnode->status.anon_access; + valid = true; + } else { + rcu_read_lock(); + permits = rcu_dereference(vnode->permit_cache); + if (permits) { + for (i = 0; i < permits->nr_permits; i++) { + if (permits->permits[i].key < key) + continue; + if (permits->permits[i].key > key) + break; + + *_access = permits->permits[i].access; + valid = !permits->invalidated; + break; + } + } + rcu_read_unlock(); + } + + if (!valid) { + /* Check the status on the file we're actually interested in + * (the post-processing will cache the result). + */ + _debug("no valid permit"); + + ret = afs_fetch_status(vnode, key, false, _access); + if (ret < 0) { + *_access = 0; + _leave(" = %d", ret); + return ret; + } + } + + _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 user_namespace *mnt_userns, struct inode *inode, + int mask) +{ + struct afs_vnode *vnode = AFS_FS_I(inode); + afs_access_t access; + struct key *key; + int ret = 0; + + _enter("{{%llx:%llu},%lx},%x,", + vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask); + + if (mask & MAY_NOT_BLOCK) { + key = afs_request_key_rcu(vnode->volume->cell); + if (IS_ERR(key)) + return -ECHILD; + + ret = -ECHILD; + if (!afs_check_validity(vnode) || + !afs_check_permit_rcu(vnode, key, &access)) + goto error; + } else { + key = afs_request_key(vnode->volume->cell); + if (IS_ERR(key)) { + _leave(" = %ld [key]", PTR_ERR(key)); + return PTR_ERR(key); + } + + ret = afs_validate(vnode, key); + if (ret < 0) + goto error; + + /* check the permits to see if we've got one yet */ + ret = afs_check_permit(vnode, key, &access); + if (ret < 0) + goto error; + } + + /* interpret the access mask */ + _debug("REQ %x ACC %x on %s", + mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file"); + + ret = 0; + if (S_ISDIR(inode->i_mode)) { + if (mask & (MAY_EXEC | MAY_READ | MAY_CHDIR)) { + if (!(access & AFS_ACE_LOOKUP)) + goto permission_denied; + } + if (mask & MAY_WRITE) { + if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */ + AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */ + goto permission_denied; + } + } else { + if (!(access & AFS_ACE_LOOKUP)) + goto permission_denied; + if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR)) + goto permission_denied; + if (mask & (MAY_EXEC | MAY_READ)) { + if (!(access & AFS_ACE_READ)) + goto permission_denied; + if (!(inode->i_mode & S_IRUSR)) + goto permission_denied; + } else if (mask & MAY_WRITE) { + if (!(access & AFS_ACE_WRITE)) + goto permission_denied; + if (!(inode->i_mode & S_IWUSR)) + goto permission_denied; + } + } + + key_put(key); + _leave(" = %d", ret); + return ret; + +permission_denied: + ret = -EACCES; +error: + key_put(key); + _leave(" = %d", ret); + return ret; +} + +void __exit afs_clean_up_permit_cache(void) +{ + int i; + + for (i = 0; i < HASH_SIZE(afs_permits_cache); i++) + WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i])); + +} |