[PATCH] Keys: Allow in-kernel key requestor to pass auxiliary data to upcaller

The proposed NFS key type uses its own method of passing key requests to
userspace (upcalling) rather than invoking /sbin/request-key.  This is
because the responsible userspace daemon should already be running and will
be contacted through rpc_pipefs.

This patch permits the NFS filesystem to pass auxiliary data to the upcall
operation (struct key_type::request_key) so that the upcaller can use a
pre-existing communications channel more easily.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-By: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/Documentation/keys.txt b/Documentation/keys.txt
index 61c0fad2fe2f..e373f0212843 100644
--- a/Documentation/keys.txt
+++ b/Documentation/keys.txt
@@ -780,6 +780,17 @@ payload contents" for more information.
     See also Documentation/keys-request-key.txt.
 
 
+(*) To search for a key, passing auxiliary data to the upcaller, call:
+
+        struct key *request_key_with_auxdata(const struct key_type *type,
+                                             const char *description,
+                                             const char *callout_string,
+                                             void *aux);
+
+    This is identical to request_key(), except that the auxiliary data is
+    passed to the key_type->request_key() op if it exists.
+
+
 (*) When it is no longer required, the key should be released using:
 
         void key_put(struct key *key);
@@ -1031,6 +1042,24 @@ The structure has a number of fields, some of which are mandatory:
      as might happen when the userspace buffer is accessed.
 
 
+ (*) int (*request_key)(struct key *key, struct key *authkey, const char *op,
+                        void *aux);
+
+     This method is optional.  If provided, request_key() and
+     request_key_with_auxdata() will invoke this function rather than
+     upcalling to /sbin/request-key to operate upon a key of this type.
+
+     The aux parameter is as passed to request_key_with_auxdata() or is NULL
+     otherwise.  Also passed are the key to be operated upon, the
+     authorisation key for this operation and the operation type (currently
+     only "create").
+
+     This function should return only when the upcall is complete.  Upon return
+     the authorisation key will be revoked, and the target key will be
+     negatively instantiated if it is still uninstantiated.  The error will be
+     returned to the caller of request_key*().
+
+
 ============================
 REQUEST-KEY CALLBACK SERVICE
 ============================