NFS: Add an "xprtsec=" NFS mount option

After some discussion, we decided that controlling transport layer
security policy should be separate from the setting for the user
authentication flavor. To accomplish this, add a new NFS mount
option to select a transport layer security policy for RPC
operations associated with the mount point.

  xprtsec=none     - Transport layer security is forced off.

  xprtsec=tls      - Establish an encryption-only TLS session. If
                     the initial handshake fails, the mount fails.
                     If TLS is not available on a reconnect, drop
                     the connection and try again.

  xprtsec=mtls     - Both sides authenticate and an encrypted
                     session is created. If the initial handshake
                     fails, the mount fails. If TLS is not available
                     on a reconnect, drop the connection and try
                     again.

To support client peer authentication (mtls), the handshake daemon
will have configurable default authentication material (certificate
or pre-shared key). In the future, mount options can be added that
can provide this material on a per-mount basis.

Updates to mount.nfs (to support xprtsec=auto) and nfs(5) will be
sent under separate cover.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 30e53e93049e..059b0beabc1b 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -59,6 +59,8 @@
 #include <linux/uaccess.h>
 #include <linux/nfs_ssc.h>
 
+#include <uapi/linux/tls.h>
+
 #include "nfs4_fs.h"
 #include "callback.h"
 #include "delegation.h"
@@ -491,6 +493,16 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss,
 	seq_printf(m, ",timeo=%lu", 10U * nfss->client->cl_timeout->to_initval / HZ);
 	seq_printf(m, ",retrans=%u", nfss->client->cl_timeout->to_retries);
 	seq_printf(m, ",sec=%s", nfs_pseudoflavour_to_name(nfss->client->cl_auth->au_flavor));
+	switch (clp->cl_xprtsec.policy) {
+	case RPC_XPRTSEC_TLS_ANON:
+		seq_puts(m, ",xprtsec=tls");
+		break;
+	case RPC_XPRTSEC_TLS_X509:
+		seq_puts(m, ",xprtsec=mtls");
+		break;
+	default:
+		break;
+	}
 
 	if (version != 4)
 		nfs_show_mountd_options(m, nfss, showdefaults);