libceph: add authorizer challenge

When a client authenticates with a service, an authorizer is sent with
a nonce to the service (ceph_x_authorize_[ab]) and the service responds
with a mutation of that nonce (ceph_x_authorize_reply).  This lets the
client verify the service is who it says it is but it doesn't protect
against a replay: someone can trivially capture the exchange and reuse
the same authorizer to authenticate themselves.

Allow the service to reject an initial authorizer with a random
challenge (ceph_x_authorize_challenge).  The client then has to respond
with an updated authorizer proving they are able to decrypt the
service's challenge and that the new authorizer was produced for this
specific connection instance.

The accepting side requires this challenge and response unconditionally
if the client side advertises they have CEPHX_V2 feature bit.

This addresses CVE-2018-1128.

Link: http://tracker.ceph.com/issues/24836
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 021718570b50..fc2b4491ee0a 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -31,6 +31,9 @@ struct ceph_connection_operations {
 	struct ceph_auth_handshake *(*get_authorizer) (
 				struct ceph_connection *con,
 			       int *proto, int force_new);
+	int (*add_authorizer_challenge)(struct ceph_connection *con,
+					void *challenge_buf,
+					int challenge_buf_len);
 	int (*verify_authorizer_reply) (struct ceph_connection *con);
 	int (*invalidate_authorizer)(struct ceph_connection *con);