ceph: add support for auth_x authentication protocol

The auth_x protocol implements support for a kerberos-like mutual
authentication infrastructure used by Ceph.  We do not simply use vanilla
kerberos because of scalability and performance issues when dealing with
a large cluster of nodes providing a single logical service.

Auth_x provides mutual authentication of client and server and protects
against replay and man in the middle attacks.  It does not encrypt
the full session over the wire, however, so data payload may still be
snooped.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/Makefile

@@ -15,6 +15,7 @@ ceph-objs := super.o inode.o dir.o file.o addr.o ioctl.o \
 	debugfs.o \
 	auth.o auth_none.o \
 	crypto.o armor.o \
+	auth_x.o \
 	ceph_fs.o ceph_strings.o ceph_hash.o ceph_frag.o
 
 else

fs/ceph/auth.c

@@ -5,6 +5,7 @@
 
 #include "types.h"
 #include "auth_none.h"
+#include "auth_x.h"
 #include "decode.h"
 #include "super.h"
 
@@ -14,14 +15,17 @@
  * get protocol handler
  */
 static u32 supported_protocols[] = {
-	CEPH_AUTH_NONE
+	CEPH_AUTH_NONE,
+	CEPH_AUTH_CEPHX
 };
 
 int ceph_auth_init_protocol(struct ceph_auth_client *ac, int protocol)
 {
 	switch (protocol) {
 	case CEPH_AUTH_NONE:
 		return ceph_auth_none_init(ac);
+	case CEPH_AUTH_CEPHX:
+		return ceph_x_init(ac);
 	default:
 		return -ENOENT;
 	}