diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index f5a299daae95..4fc7582233db 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -4154,6 +4154,16 @@ static struct ceph_auth_handshake *get_authorizer(struct ceph_connection *con,
 	return auth;
 }
 
+static int add_authorizer_challenge(struct ceph_connection *con,
+				    void *challenge_buf, int challenge_buf_len)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
+
+	return ceph_auth_add_authorizer_challenge(ac, s->s_auth.authorizer,
+					    challenge_buf, challenge_buf_len);
+}
 
 static int verify_authorizer_reply(struct ceph_connection *con)
 {
@@ -4217,6 +4227,7 @@ static const struct ceph_connection_operations mds_con_ops = {
 	.put = con_put,
 	.dispatch = dispatch,
 	.get_authorizer = get_authorizer,
+	.add_authorizer_challenge = add_authorizer_challenge,
 	.verify_authorizer_reply = verify_authorizer_reply,
 	.invalidate_authorizer = invalidate_authorizer,
 	.peer_reset = peer_reset,
diff --git a/include/linux/ceph/auth.h b/include/linux/ceph/auth.h
index e931da8424a4..6728c2ee0205 100644
--- a/include/linux/ceph/auth.h
+++ b/include/linux/ceph/auth.h
@@ -64,6 +64,10 @@ struct ceph_auth_client_ops {
 	/* ensure that an existing authorizer is up to date */
 	int (*update_authorizer)(struct ceph_auth_client *ac, int peer_type,
 				 struct ceph_auth_handshake *auth);
+	int (*add_authorizer_challenge)(struct ceph_auth_client *ac,
+					struct ceph_authorizer *a,
+					void *challenge_buf,
+					int challenge_buf_len);
 	int (*verify_authorizer_reply)(struct ceph_auth_client *ac,
 				       struct ceph_authorizer *a);
 	void (*invalidate_authorizer)(struct ceph_auth_client *ac,
@@ -118,6 +122,10 @@ void ceph_auth_destroy_authorizer(struct ceph_authorizer *a);
 extern int ceph_auth_update_authorizer(struct ceph_auth_client *ac,
 				       int peer_type,
 				       struct ceph_auth_handshake *a);
+int ceph_auth_add_authorizer_challenge(struct ceph_auth_client *ac,
+				       struct ceph_authorizer *a,
+				       void *challenge_buf,
+				       int challenge_buf_len);
 extern int ceph_auth_verify_authorizer_reply(struct ceph_auth_client *ac,
 					     struct ceph_authorizer *a);
 extern void ceph_auth_invalidate_authorizer(struct ceph_auth_client *ac,
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);
 
diff --git a/include/linux/ceph/msgr.h b/include/linux/ceph/msgr.h
index 73ae2a926548..9e50aede46c8 100644
--- a/include/linux/ceph/msgr.h
+++ b/include/linux/ceph/msgr.h
@@ -91,7 +91,7 @@ struct ceph_entity_inst {
 #define CEPH_MSGR_TAG_SEQ           13 /* 64-bit int follows with seen seq number */
 #define CEPH_MSGR_TAG_KEEPALIVE2    14 /* keepalive2 byte + ceph_timespec */
 #define CEPH_MSGR_TAG_KEEPALIVE2_ACK 15 /* keepalive2 reply */
-
+#define CEPH_MSGR_TAG_CHALLENGE_AUTHORIZER 16  /* cephx v2 doing server challenge */
 
 /*
  * connection negotiation
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)
 {
diff --git a/net/ceph/auth_x.c b/net/ceph/auth_x.c
index 61cccb93f653..512eed4291fe 100644
--- a/net/ceph/auth_x.c
+++ b/net/ceph/auth_x.c
@@ -295,7 +295,8 @@ static int ceph_x_proc_ticket_reply(struct ceph_auth_client *ac,
  * authorizer.  The first part (ceph_x_authorize_a) should already be
  * encoded.
  */
-static int encrypt_authorizer(struct ceph_x_authorizer *au)
+static int encrypt_authorizer(struct ceph_x_authorizer *au,
+			      u64 *server_challenge)
 {
 	struct ceph_x_authorize_a *msg_a;
 	struct ceph_x_authorize_b *msg_b;
@@ -308,16 +309,28 @@ static int encrypt_authorizer(struct ceph_x_authorizer *au)
 	end = au->buf->vec.iov_base + au->buf->vec.iov_len;
 
 	msg_b = p + ceph_x_encrypt_offset();
-	msg_b->struct_v = 1;
+	msg_b->struct_v = 2;
 	msg_b->nonce = cpu_to_le64(au->nonce);
+	if (server_challenge) {
+		msg_b->have_challenge = 1;
+		msg_b->server_challenge_plus_one =
+		    cpu_to_le64(*server_challenge + 1);
+	} else {
+		msg_b->have_challenge = 0;
+		msg_b->server_challenge_plus_one = 0;
+	}
 
 	ret = ceph_x_encrypt(&au->session_key, p, end - p, sizeof(*msg_b));
 	if (ret < 0)
 		return ret;
 
 	p += ret;
-	WARN_ON(p > end);
-	au->buf->vec.iov_len = p - au->buf->vec.iov_base;
+	if (server_challenge) {
+		WARN_ON(p != end);
+	} else {
+		WARN_ON(p > end);
+		au->buf->vec.iov_len = p - au->buf->vec.iov_base;
+	}
 
 	return 0;
 }
@@ -382,7 +395,7 @@ static int ceph_x_build_authorizer(struct ceph_auth_client *ac,
 	     le64_to_cpu(msg_a->ticket_blob.secret_id));
 
 	get_random_bytes(&au->nonce, sizeof(au->nonce));
-	ret = encrypt_authorizer(au);
+	ret = encrypt_authorizer(au, NULL);
 	if (ret) {
 		pr_err("failed to encrypt authorizer: %d", ret);
 		goto out_au;
@@ -664,6 +677,54 @@ static int ceph_x_update_authorizer(
 	return 0;
 }
 
+static int decrypt_authorize_challenge(struct ceph_x_authorizer *au,
+				       void *challenge_buf,
+				       int challenge_buf_len,
+				       u64 *server_challenge)
+{
+	struct ceph_x_authorize_challenge *ch =
+	    challenge_buf + sizeof(struct ceph_x_encrypt_header);
+	int ret;
+
+	/* no leading len */
+	ret = __ceph_x_decrypt(&au->session_key, challenge_buf,
+			       challenge_buf_len);
+	if (ret < 0)
+		return ret;
+	if (ret < sizeof(*ch)) {
+		pr_err("bad size %d for ceph_x_authorize_challenge\n", ret);
+		return -EINVAL;
+	}
+
+	*server_challenge = le64_to_cpu(ch->server_challenge);
+	return 0;
+}
+
+static int ceph_x_add_authorizer_challenge(struct ceph_auth_client *ac,
+					   struct ceph_authorizer *a,
+					   void *challenge_buf,
+					   int challenge_buf_len)
+{
+	struct ceph_x_authorizer *au = (void *)a;
+	u64 server_challenge;
+	int ret;
+
+	ret = decrypt_authorize_challenge(au, challenge_buf, challenge_buf_len,
+					  &server_challenge);
+	if (ret) {
+		pr_err("failed to decrypt authorize challenge: %d", ret);
+		return ret;
+	}
+
+	ret = encrypt_authorizer(au, &server_challenge);
+	if (ret) {
+		pr_err("failed to encrypt authorizer w/ challenge: %d", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int ceph_x_verify_authorizer_reply(struct ceph_auth_client *ac,
 					  struct ceph_authorizer *a)
 {
@@ -816,6 +877,7 @@ static const struct ceph_auth_client_ops ceph_x_ops = {
 	.handle_reply = ceph_x_handle_reply,
 	.create_authorizer = ceph_x_create_authorizer,
 	.update_authorizer = ceph_x_update_authorizer,
+	.add_authorizer_challenge = ceph_x_add_authorizer_challenge,
 	.verify_authorizer_reply = ceph_x_verify_authorizer_reply,
 	.invalidate_authorizer = ceph_x_invalidate_authorizer,
 	.reset =  ceph_x_reset,
diff --git a/net/ceph/auth_x_protocol.h b/net/ceph/auth_x_protocol.h
index 32c13d763b9a..24b0b74564d0 100644
--- a/net/ceph/auth_x_protocol.h
+++ b/net/ceph/auth_x_protocol.h
@@ -70,6 +70,13 @@ struct ceph_x_authorize_a {
 struct ceph_x_authorize_b {
 	__u8 struct_v;
 	__le64 nonce;
+	__u8 have_challenge;
+	__le64 server_challenge_plus_one;
+} __attribute__ ((packed));
+
+struct ceph_x_authorize_challenge {
+	__u8 struct_v;
+	__le64 server_challenge;
 } __attribute__ ((packed));
 
 struct ceph_x_authorize_reply {
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 500cc3da586f..e915c8bce117 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2080,9 +2080,24 @@ static int process_connect(struct ceph_connection *con)
 	if (con->auth) {
 		/*
 		 * Any connection that defines ->get_authorizer()
-		 * should also define ->verify_authorizer_reply().
+		 * should also define ->add_authorizer_challenge() and
+		 * ->verify_authorizer_reply().
+		 *
 		 * See get_connect_authorizer().
 		 */
+		if (con->in_reply.tag == CEPH_MSGR_TAG_CHALLENGE_AUTHORIZER) {
+			ret = con->ops->add_authorizer_challenge(
+				    con, con->auth->authorizer_reply_buf,
+				    le32_to_cpu(con->in_reply.authorizer_len));
+			if (ret < 0)
+				return ret;
+
+			con_out_kvec_reset(con);
+			__prepare_write_connect(con);
+			prepare_read_connect(con);
+			return 0;
+		}
+
 		ret = con->ops->verify_authorizer_reply(con);
 		if (ret < 0) {
 			con->error_msg = "bad authorize reply";
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 8002b8e9ce24..60934bd8796c 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -5393,6 +5393,16 @@ static struct ceph_auth_handshake *get_authorizer(struct ceph_connection *con,
 	return auth;
 }
 
+static int add_authorizer_challenge(struct ceph_connection *con,
+				    void *challenge_buf, int challenge_buf_len)
+{
+	struct ceph_osd *o = con->private;
+	struct ceph_osd_client *osdc = o->o_osdc;
+	struct ceph_auth_client *ac = osdc->client->monc.auth;
+
+	return ceph_auth_add_authorizer_challenge(ac, o->o_auth.authorizer,
+					    challenge_buf, challenge_buf_len);
+}
 
 static int verify_authorizer_reply(struct ceph_connection *con)
 {
@@ -5442,6 +5452,7 @@ static const struct ceph_connection_operations osd_con_ops = {
 	.put = put_osd_con,
 	.dispatch = dispatch,
 	.get_authorizer = get_authorizer,
+	.add_authorizer_challenge = add_authorizer_challenge,
 	.verify_authorizer_reply = verify_authorizer_reply,
 	.invalidate_authorizer = invalidate_authorizer,
 	.alloc_msg = alloc_msg,