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, 62 insertions, 0 deletions

diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index 5626d358ee2e..853e8d609bb3 100644
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -18,6 +18,9 @@
 #include <linux/nfs_fs.h>
 #include <linux/nfs_mount.h>
 #include <linux/nfs4_mount.h>
+
+#include <net/handshake.h>
+
 #include "nfs.h"
 #include "internal.h"
 
@@ -88,6 +91,7 @@ enum nfs_param {
 	Opt_vers,
 	Opt_wsize,
 	Opt_write,
+	Opt_xprtsec,
 };
 
 enum {
@@ -194,6 +198,7 @@ static const struct fs_parameter_spec nfs_fs_parameters[] = {
 	fsparam_string("vers",		Opt_vers),
 	fsparam_enum  ("write",		Opt_write, nfs_param_enums_write),
 	fsparam_u32   ("wsize",		Opt_wsize),
+	fsparam_string("xprtsec",	Opt_xprtsec),
 	{}
 };
 
@@ -267,6 +272,20 @@ static const struct constant_table nfs_secflavor_tokens[] = {
 	{}
 };
 
+enum {
+	Opt_xprtsec_none,
+	Opt_xprtsec_tls,
+	Opt_xprtsec_mtls,
+	nr__Opt_xprtsec
+};
+
+static const struct constant_table nfs_xprtsec_policies[] = {
+	{ "none",	Opt_xprtsec_none },
+	{ "tls",	Opt_xprtsec_tls },
+	{ "mtls",	Opt_xprtsec_mtls },
+	{}
+};
+
 /*
  * Sanity-check a server address provided by the mount command.
  *
@@ -320,9 +339,21 @@ static int nfs_validate_transport_protocol(struct fs_context *fc,
 	default:
 		ctx->nfs_server.protocol = XPRT_TRANSPORT_TCP;
 	}
+
+	if (ctx->xprtsec.policy != RPC_XPRTSEC_NONE)
+		switch (ctx->nfs_server.protocol) {
+		case XPRT_TRANSPORT_TCP:
+			ctx->nfs_server.protocol = XPRT_TRANSPORT_TCP_TLS;
+			break;
+		default:
+			goto out_invalid_xprtsec_policy;
+	}
+
 	return 0;
 out_invalid_transport_udp:
 	return nfs_invalf(fc, "NFS: Unsupported transport protocol udp");
+out_invalid_xprtsec_policy:
+	return nfs_invalf(fc, "NFS: Transport does not support xprtsec");
 }
 
 /*
@@ -430,6 +461,29 @@ static int nfs_parse_security_flavors(struct fs_context *fc,
 	return 0;
 }
 
+static int nfs_parse_xprtsec_policy(struct fs_context *fc,
+				    struct fs_parameter *param)
+{
+	struct nfs_fs_context *ctx = nfs_fc2context(fc);
+
+	trace_nfs_mount_assign(param->key, param->string);
+
+	switch (lookup_constant(nfs_xprtsec_policies, param->string, -1)) {
+	case Opt_xprtsec_none:
+		ctx->xprtsec.policy = RPC_XPRTSEC_NONE;
+		break;
+	case Opt_xprtsec_tls:
+		ctx->xprtsec.policy = RPC_XPRTSEC_TLS_ANON;
+		break;
+	case Opt_xprtsec_mtls:
+		ctx->xprtsec.policy = RPC_XPRTSEC_TLS_X509;
+		break;
+	default:
+		return nfs_invalf(fc, "NFS: Unrecognized transport security policy");
+	}
+	return 0;
+}
+
 static int nfs_parse_version_string(struct fs_context *fc,
 				    const char *string)
 {
@@ -696,6 +750,11 @@ static int nfs_fs_context_parse_param(struct fs_context *fc,
 		if (ret < 0)
 			return ret;
 		break;
+	case Opt_xprtsec:
+		ret = nfs_parse_xprtsec_policy(fc, param);
+		if (ret < 0)
+			return ret;
+		break;
 
 	case Opt_proto:
 		if (!param->string)
@@ -1574,6 +1633,9 @@ static int nfs_init_fs_context(struct fs_context *fc)
 		ctx->selected_flavor	= RPC_AUTH_MAXFLAVOR;
 		ctx->minorversion	= 0;
 		ctx->need_mount		= true;
+		ctx->xprtsec.policy	= RPC_XPRTSEC_NONE;
+		ctx->xprtsec.cert_serial	= TLS_NO_CERT;
+		ctx->xprtsec.privkey_serial	= TLS_NO_PRIVKEY;
 
 		fc->s_iflags		|= SB_I_STABLE_WRITES;
 	}