[AFS]: Add security support.

Add security support to the AFS filesystem.  Kerberos IV tickets are added as
RxRPC keys are added to the session keyring with the klog program.  open() and
other VFS operations then find this ticket with request_key() and either use
it immediately (eg: mkdir, unlink) or attach it to a file descriptor (open).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 345 insertions, 0 deletions

diff --git a/fs/afs/security.c b/fs/afs/security.c
new file mode 100644
index 00000000000..cbdd7f7162f
--- /dev/null
+++ b/fs/afs/security.c
@@ -0,0 +1,345 @@
+/* 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;
+}