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, 16 insertions, 0 deletions

diff --git a/net/ceph/auth.c b/net/ceph/auth.c
index dbde2b3c3c15..fbeee068ea14 100644
--- a/net/ceph/auth.c
+++ b/net/ceph/auth.c
@@ -315,6 +315,22 @@ int ceph_auth_update_authorizer(struct ceph_auth_client *ac,
 }
 EXPORT_SYMBOL(ceph_auth_update_authorizer);
 
+int ceph_auth_add_authorizer_challenge(struct ceph_auth_client *ac,
+				       struct ceph_authorizer *a,
+				       void *challenge_buf,
+				       int challenge_buf_len)
+{
+	int ret = 0;
+
+	mutex_lock(&ac->mutex);
+	if (ac->ops && ac->ops->add_authorizer_challenge)
+		ret = ac->ops->add_authorizer_challenge(ac, a, challenge_buf,
+							challenge_buf_len);
+	mutex_unlock(&ac->mutex);
+	return ret;
+}
+EXPORT_SYMBOL(ceph_auth_add_authorizer_challenge);
+
 int ceph_auth_verify_authorizer_reply(struct ceph_auth_client *ac,
 				      struct ceph_authorizer *a)
 {