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-rw-r--r--fs/afs/security.c419
1 files changed, 419 insertions, 0 deletions
diff --git a/fs/afs/security.c b/fs/afs/security.c
new file mode 100644
index 000000000..66042b432
--- /dev/null
+++ b/fs/afs/security.c
@@ -0,0 +1,419 @@
+/* AFS security handling
+ *
+ * Copyright (C) 2007, 2017 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 <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(&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 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_permits *permits, *xpermits, *replacement, *zap, *new = NULL;
+ afs_access_t caller_access = READ_ONCE(vnode->status.caller_access);
+ size_t size = 0;
+ bool changed = false;
+ int i, j;
+
+ _enter("{%x:%u},%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 (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest)) {
+ 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 (cb_break != afs_cb_break_sum(vnode, vnode->cb_interest))
+ 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(sizeof(struct afs_permits) +
+ sizeof(struct afs_permit) * 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);
+
+ spin_lock(&vnode->lock);
+ zap = rcu_access_pointer(vnode->permit_cache);
+ if (cb_break == afs_cb_break_sum(vnode, vnode->cb_interest) &&
+ zap == permits)
+ rcu_assign_pointer(vnode->permit_cache, replacement);
+ else
+ zap = replacement;
+ spin_unlock(&vnode->lock);
+ 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;
+}
+
+/*
+ * 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("{%x:%u},%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);
+ if (ret < 0) {
+ *_access = 0;
+ _leave(" = %d", ret);
+ return ret;
+ }
+ *_access = vnode->status.caller_access;
+ }
+
+ _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 afs_vnode *vnode = AFS_FS_I(inode);
+ afs_access_t uninitialized_var(access);
+ struct key *key;
+ int ret;
+
+ if (mask & MAY_NOT_BLOCK)
+ return -ECHILD;
+
+ _enter("{{%x:%u},%lx},%x,",
+ vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
+
+ 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");
+
+ 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]));
+
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-28 22:59:43 +0000