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>

3 files changed, 59 insertions, 5 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index f5294047df77..9b81be8d9946 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -124,6 +124,41 @@ rpcauth_unregister(const struct rpc_authops *ops)
 EXPORT_SYMBOL_GPL(rpcauth_unregister);
 
 /**
+ * rpcauth_get_pseudoflavor - check if security flavor is supported
+ * @flavor: a security flavor
+ * @info: a GSS mech OID, quality of protection, and service value
+ *
+ * Verifies that an appropriate kernel module is available or already loaded.
+ * Returns an equivalent pseudoflavor, or RPC_AUTH_MAXFLAVOR if "flavor" is
+ * not supported locally.
+ */
+rpc_authflavor_t
+rpcauth_get_pseudoflavor(rpc_authflavor_t flavor, struct rpcsec_gss_info *info)
+{
+        const struct rpc_authops *ops;
+        rpc_authflavor_t pseudoflavor;
+
+        ops = auth_flavors[flavor];
+        if (ops == NULL)
+                request_module("rpc-auth-%u", flavor);
+        spin_lock(&rpc_authflavor_lock);
+        ops = auth_flavors[flavor];
+        if (ops == NULL || !try_module_get(ops->owner)) {
+                spin_unlock(&rpc_authflavor_lock);
+                return RPC_AUTH_MAXFLAVOR;
+        }
+        spin_unlock(&rpc_authflavor_lock);
+
+        pseudoflavor = flavor;
+        if (ops->info2flavor != NULL)
+                pseudoflavor = ops->info2flavor(info);
+
+        module_put(ops->owner);
+        return pseudoflavor;
+}
+EXPORT_SYMBOL_GPL(rpcauth_get_pseudoflavor);
+
+/**
  * rpcauth_list_flavors - discover registered flavors and pseudoflavors
  * @array: array to fill in
  * @size: size of "array"
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 282dfb14db05..a7420076ef39 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1641,6 +1641,7 @@ static const struct rpc_authops authgss_ops = {
         .pipes_create   = gss_pipes_dentries_create,
         .pipes_destroy  = gss_pipes_dentries_destroy,
         .list_pseudoflavors = gss_mech_list_pseudoflavors,
+        .info2flavor    = gss_mech_info2flavor,
 };
 
 static const struct rpc_credops gss_credops = {
diff --git a/net/sunrpc/auth_gss/gss_mech_switch.c b/net/sunrpc/auth_gss/gss_mech_switch.c
index f0f4eee63a35..4db66f5f490e 100644
--- a/net/sunrpc/auth_gss/gss_mech_switch.c
+++ b/net/sunrpc/auth_gss/gss_mech_switch.c
@@ -171,8 +171,7 @@ struct gss_api_mech * gss_mech_get_by_name(const char *name)
 }
 EXPORT_SYMBOL_GPL(gss_mech_get_by_name);
 
-struct gss_api_mech *
-gss_mech_get_by_OID(struct xdr_netobj *obj)
+static struct gss_api_mech *gss_mech_get_by_OID(struct rpcsec_gss_oid *obj)
 {
         struct gss_api_mech     *pos, *gm = NULL;
 
@@ -188,11 +187,8 @@ gss_mech_get_by_OID(struct xdr_netobj *obj)
         }
         spin_unlock(&registered_mechs_lock);
         return gm;
-
 }
 
-EXPORT_SYMBOL_GPL(gss_mech_get_by_OID);
-
 static inline int
 mech_supports_pseudoflavor(struct gss_api_mech *gm, u32 pseudoflavor)
 {
@@ -282,6 +278,28 @@ gss_svc_to_pseudoflavor(struct gss_api_mech *gm, u32 service)
 }
 EXPORT_SYMBOL_GPL(gss_svc_to_pseudoflavor);
 
+/**
+ * gss_mech_info2flavor - look up a pseudoflavor given a GSS tuple
+ * @info: a GSS mech OID, quality of protection, and service value
+ *
+ * Returns a matching pseudoflavor, or RPC_AUTH_MAXFLAVOR if the tuple is
+ * not supported.
+ */
+rpc_authflavor_t gss_mech_info2flavor(struct rpcsec_gss_info *info)
+{
+        rpc_authflavor_t pseudoflavor;
+        struct gss_api_mech *gm;
+
+        gm = gss_mech_get_by_OID(&info->oid);
+        if (gm == NULL)
+                return RPC_AUTH_MAXFLAVOR;
+
+        pseudoflavor = gss_svc_to_pseudoflavor(gm, info->service);
+
+        gss_mech_put(gm);
+        return pseudoflavor;
+}
+
 u32
 gss_pseudoflavor_to_service(struct gss_api_mech *gm, u32 pseudoflavor)
 {