KEYS: Make request_key() and co fundamentally asynchronous

Make request_key() and co fundamentally asynchronous to make it easier for
NFS to make use of them.  There are now accessor functions that do
asynchronous constructions, a wait function to wait for construction to
complete, and a completion function for the key type to indicate completion
of construction.

Note that the construction queue is now gone.  Instead, keys under
construction are linked in to the appropriate keyring in advance, and that
anyone encountering one must wait for it to be complete before they can use
it.  This is done automatically for userspace.

The following auxiliary changes are also made:

 (1) Key type implementation stuff is split from linux/key.h into
     linux/key-type.h.

 (2) AF_RXRPC provides a way to allocate null rxrpc-type keys so that AFS does
     not need to call key_instantiate_and_link() directly.

 (3) Adjust the debugging macros so that they're -Wformat checked even if
     they are disabled, and make it so they can be enabled simply by defining
     __KDEBUG to be consistent with other code of mine.

 (3) Documentation.

[alan@lxorguk.ukuu.org.uk: keys: missing word in documentation]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 112 insertions, 0 deletions

diff --git a/include/linux/key-type.h b/include/linux/key-type.h
new file mode 100644
index 000000000000..65833d4d5998
--- /dev/null
+++ b/include/linux/key-type.h
@@ -0,0 +1,112 @@
+/* Definitions for key type implementations
+ *
+ * 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 Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_KEY_TYPE_H
+#define _LINUX_KEY_TYPE_H
+
+#include <linux/key.h>
+
+#ifdef CONFIG_KEYS
+
+/*
+ * key under-construction record
+ * - passed to the request_key actor if supplied
+ */
+struct key_construction {
+	struct key	*key;	/* key being constructed */
+	struct key	*authkey;/* authorisation for key being constructed */
+};
+
+typedef int (*request_key_actor_t)(struct key_construction *key,
+				   const char *op, void *aux);
+
+/*
+ * kernel managed key type definition
+ */
+struct key_type {
+	/* name of the type */
+	const char *name;
+
+	/* default payload length for quota precalculation (optional)
+	 * - this can be used instead of calling key_payload_reserve(), that
+	 *   function only needs to be called if the real datalen is different
+	 */
+	size_t def_datalen;
+
+	/* instantiate a key of this type
+	 * - this method should call key_payload_reserve() to determine if the
+	 *   user's quota will hold the payload
+	 */
+	int (*instantiate)(struct key *key, const void *data, size_t datalen);
+
+	/* update a key of this type (optional)
+	 * - this method should call key_payload_reserve() to recalculate the
+	 *   quota consumption
+	 * - the key must be locked against read when modifying
+	 */
+	int (*update)(struct key *key, const void *data, size_t datalen);
+
+	/* match a key against a description */
+	int (*match)(const struct key *key, const void *desc);
+
+	/* clear some of the data from a key on revokation (optional)
+	 * - the key's semaphore will be write-locked by the caller
+	 */
+	void (*revoke)(struct key *key);
+
+	/* clear the data from a key (optional) */
+	void (*destroy)(struct key *key);
+
+	/* describe a key */
+	void (*describe)(const struct key *key, struct seq_file *p);
+
+	/* read a key's data (optional)
+	 * - permission checks will be done by the caller
+	 * - the key's semaphore will be readlocked by the caller
+	 * - should return the amount of data that could be read, no matter how
+	 *   much is copied into the buffer
+	 * - shouldn't do the copy if the buffer is NULL
+	 */
+	long (*read)(const struct key *key, char __user *buffer, size_t buflen);
+
+	/* handle request_key() for this type instead of invoking
+	 * /sbin/request-key (optional)
+	 * - key is the key to instantiate
+	 * - authkey is the authority to assume when instantiating this key
+	 * - op is the operation to be done, usually "create"
+	 * - the call must not return until the instantiation process has run
+	 *   its course
+	 */
+	request_key_actor_t request_key;
+
+	/* internal fields */
+	struct list_head	link;		/* link in types list */
+};
+
+extern struct key_type key_type_keyring;
+
+extern int register_key_type(struct key_type *ktype);
+extern void unregister_key_type(struct key_type *ktype);
+
+extern int key_payload_reserve(struct key *key, size_t datalen);
+extern int key_instantiate_and_link(struct key *key,
+				    const void *data,
+				    size_t datalen,
+				    struct key *keyring,
+				    struct key *instkey);
+extern int key_negate_and_link(struct key *key,
+			       unsigned timeout,
+			       struct key *keyring,
+			       struct key *instkey);
+extern void complete_request_key(struct key_construction *cons, int error);
+
+#endif /* CONFIG_KEYS */
+#endif /* _LINUX_KEY_TYPE_H */