SUNRPC: Introduce rpcauth_get_pseudoflavor()

A SECINFO reply may contain flavors whose kernel module is not
yet loaded by the client's kernel.  A new RPC client API, called
rpcauth_get_pseudoflavor(), is introduced to do proper checking
for support of a security flavor.

When this API is invoked, the RPC client now tries to load the
module for each flavor first before performing the "is this
supported?" check.  This means if a module is available on the
client, but has not been loaded yet, it will be loaded and
registered automatically when the SECINFO reply is processed.

The new API can take a full GSS tuple (OID, QoP, and service).
Previously only the OID and service were considered.

nfs_find_best_sec() is updated to verify all flavors requested in a
SECINFO reply, including AUTH_NULL and AUTH_UNIX.  Previously these
two flavors were simply assumed to be supported without consulting
the RPC client.

Note that the replaced version of nfs_find_best_sec() can return
RPC_AUTH_MAXFLAVOR if the server returns a recognized OID but an
unsupported "service" value.  nfs_find_best_sec() now returns
RPC_AUTH_UNIX in this case.

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

1 files changed, 23 insertions, 18 deletions

diff --git a/fs/nfs/nfs4namespace.c b/fs/nfs/nfs4namespace.c
index 88231c92317c..cdb0b41a4810 100644
--- a/fs/nfs/nfs4namespace.c
+++ b/fs/nfs/nfs4namespace.c
@@ -134,33 +134,38 @@ static size_t nfs_parse_server_name(char *string, size_t len,
 	return ret;
 }
 
+/**
+ * nfs_find_best_sec - Find a security mechanism supported locally
+ * @flavors: List of security tuples returned by SECINFO procedure
+ *
+ * Return the pseudoflavor of the first security mechanism in
+ * "flavors" that is locally supported.  Return RPC_AUTH_UNIX if
+ * no matching flavor is found in the array.  The "flavors" array
+ * is searched in the order returned from the server, per RFC 3530
+ * recommendation.
+ */
 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
 {
-	struct gss_api_mech *mech;
-	struct xdr_netobj oid;
+	rpc_authflavor_t pseudoflavor;
+	struct nfs4_secinfo4 *secinfo;
 	unsigned int i;
-	rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
 
 	for (i = 0; i < flavors->num_flavors; i++) {
-		struct nfs4_secinfo4 *flavor = &flavors->flavors[i];
-
-		if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
-			pseudoflavor = flavor->flavor;
-			break;
-		} else if (flavor->flavor == RPC_AUTH_GSS) {
-			oid.len  = flavor->flavor_info.oid.len;
-			oid.data = flavor->flavor_info.oid.data;
-			mech = gss_mech_get_by_OID(&oid);
-			if (!mech)
-				continue;
-			pseudoflavor = gss_svc_to_pseudoflavor(mech,
-						flavor->flavor_info.service);
-			gss_mech_put(mech);
+		secinfo = &flavors->flavors[i];
+
+		switch (secinfo->flavor) {
+		case RPC_AUTH_NULL:
+		case RPC_AUTH_UNIX:
+		case RPC_AUTH_GSS:
+			pseudoflavor = rpcauth_get_pseudoflavor(secinfo->flavor,
+							&secinfo->flavor_info);
+			if (pseudoflavor != RPC_AUTH_MAXFLAVOR)
+				return pseudoflavor;
 			break;
 		}
 	}
 
-	return pseudoflavor;
+	return RPC_AUTH_UNIX;
 }
 
 static rpc_authflavor_t nfs4_negotiate_security(struct inode *inode, struct qstr *name)