[PATCH] keys: Permit running process to instantiate keys

Make it possible for a running process (such as gssapid) to be able to
instantiate a key, as was requested by Trond Myklebust for NFS4.

The patch makes the following changes:

 (1) A new, optional key type method has been added. This permits a key type
     to intercept requests at the point /sbin/request-key is about to be
     spawned and do something else with them - passing them over the
     rpc_pipefs files or netlink sockets for instance.

     The uninstantiated key, the authorisation key and the intended operation
     name are passed to the method.

 (2) The callout_info is no longer passed as an argument to /sbin/request-key
     to prevent unauthorised viewing of this data using ps or by looking in
     /proc/pid/cmdline.

     This means that the old /sbin/request-key program will not work with the
     patched kernel as it will expect to see an extra argument that is no
     longer there.

     A revised keyutils package will be made available tomorrow.

 (3) The callout_info is now attached to the authorisation key. Reading this
     key will retrieve the information.

 (4) A new field has been added to the task_struct. This holds the
     authorisation key currently active for a thread. Searches now look here
     for the caller's set of keys rather than looking for an auth key in the
     lowest level of the session keyring.

     This permits a thread to be servicing multiple requests at once and to
     switch between them. Note that this is per-thread, not per-process, and
     so is usable in multithreaded programs.

     The setting of this field is inherited across fork and exec.

 (5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that
     permits a thread to assume the authority to deal with an uninstantiated
     key. Assumption is only permitted if the authorisation key associated
     with the uninstantiated key is somewhere in the thread's keyrings.

     This function can also clear the assumption.

 (6) A new magic key specifier has been added to refer to the currently
     assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY).

 (7) Instantiation will only proceed if the appropriate authorisation key is
     assumed first. The assumed authorisation key is discarded if
     instantiation is successful.

 (8) key_validate() is moved from the file of request_key functions to the
     file of permissions functions.

 (9) The documentation is updated.

From: <Valdis.Kletnieks@vt.edu>

    Build fix.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Alexander Zangerl <az@bond.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/key.h b/include/linux/key.h
index 4d189e51bc6c..cbf464ad9589 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -177,6 +177,8 @@ struct key {
 /*
  * kernel managed key type definition
  */
+typedef int (*request_key_actor_t)(struct key *key, struct key *authkey, const char *op);
+
 struct key_type {
 	/* name of the type */
 	const char *name;
@@ -218,6 +220,16 @@ struct key_type {
 	 */
 	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 */
 };
diff --git a/include/linux/keyctl.h b/include/linux/keyctl.h
index ec8f3d622a8d..3365945640c9 100644
--- a/include/linux/keyctl.h
+++ b/include/linux/keyctl.h
@@ -19,6 +19,7 @@
 #define KEY_SPEC_USER_KEYRING		-4	/* - key ID for UID-specific keyring */
 #define KEY_SPEC_USER_SESSION_KEYRING	-5	/* - key ID for UID-session keyring */
 #define KEY_SPEC_GROUP_KEYRING		-6	/* - key ID for GID-specific keyring */
+#define KEY_SPEC_REQKEY_AUTH_KEY	-7	/* - key ID for assumed request_key auth key */
 
 /* request-key default keyrings */
 #define KEY_REQKEY_DEFL_NO_CHANGE		-1
@@ -47,5 +48,6 @@
 #define KEYCTL_NEGATE			13	/* negate a partially constructed key */
 #define KEYCTL_SET_REQKEY_KEYRING	14	/* set default request-key keyring */
 #define KEYCTL_SET_TIMEOUT		15	/* set key timeout */
+#define KEYCTL_ASSUME_AUTHORITY		16	/* assume request_key() authorisation */
 
 #endif /*  _LINUX_KEYCTL_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 20bd70749104..78eb92ae4d94 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -771,6 +771,7 @@ struct task_struct {
 	unsigned keep_capabilities:1;
 	struct user_struct *user;
 #ifdef CONFIG_KEYS
+	struct key *request_key_auth;	/* assumed request_key authority */
 	struct key *thread_keyring;	/* keyring private to this thread */
 	unsigned char jit_keyring;	/* default keyring to attach requested keys to */
 #endif