NFS: add support for multiple sec= mount options

This patch adds support for multiple security options which can be
specified using a colon-delimited list of security flavors (the same
syntax as nfsd's exports file).

This is useful, for instance, when NFSv4.x mounts cross SECINFO
boundaries. With this patch a user can use "sec=krb5i,krb5p"
to mount a remote filesystem using krb5i, but can still cross
into krb5p-only exports.

New mounts will try all security options before failing.  NFSv4.x
SECINFO results will be compared against the sec= flavors to
find the first flavor in both lists or if no match is found will
return -EPERM.

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 13 insertions, 4 deletions

diff --git a/fs/nfs/nfs4namespace.c b/fs/nfs/nfs4namespace.c
index b947054f0ca1..c08cbf40c59e 100644
--- a/fs/nfs/nfs4namespace.c
+++ b/fs/nfs/nfs4namespace.c
@@ -137,6 +137,7 @@ static size_t nfs_parse_server_name(char *string, size_t len,
 
 /**
  * nfs_find_best_sec - Find a security mechanism supported locally
+ * @server: NFS server struct
  * @flavors: List of security tuples returned by SECINFO procedure
  *
  * Return the pseudoflavor of the first security mechanism in
@@ -145,7 +146,8 @@ static size_t nfs_parse_server_name(char *string, size_t len,
  * is searched in the order returned from the server, per RFC 3530
  * recommendation.
  */
-static rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
+static rpc_authflavor_t nfs_find_best_sec(struct nfs_server *server,
+					  struct nfs4_secinfo_flavors *flavors)
 {
 	rpc_authflavor_t pseudoflavor;
 	struct nfs4_secinfo4 *secinfo;
@@ -160,12 +162,19 @@ static rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
 		case RPC_AUTH_GSS:
 			pseudoflavor = rpcauth_get_pseudoflavor(secinfo->flavor,
 							&secinfo->flavor_info);
-			if (pseudoflavor != RPC_AUTH_MAXFLAVOR)
+			/* make sure pseudoflavor matches sec= mount opt */
+			if (pseudoflavor != RPC_AUTH_MAXFLAVOR &&
+			    nfs_auth_info_match(&server->auth_info,
+						pseudoflavor))
 				return pseudoflavor;
 			break;
 		}
 	}
 
+	/* if there were any sec= options then nothing matched */
+	if (server->auth_info.flavor_len > 0)
+		return -EPERM;
+
 	return RPC_AUTH_UNIX;
 }
 
@@ -187,7 +196,7 @@ static rpc_authflavor_t nfs4_negotiate_security(struct inode *inode, struct qstr
 		goto out;
 	}
 
-	flavor = nfs_find_best_sec(flavors);
+	flavor = nfs_find_best_sec(NFS_SERVER(inode), flavors);
 
 out:
 	put_page(page);
@@ -390,7 +399,7 @@ struct vfsmount *nfs4_submount(struct nfs_server *server, struct dentry *dentry,
 
 	if (client->cl_auth->au_flavor != flavor)
 		flavor = client->cl_auth->au_flavor;
-	else if (server->auth_info.flavor_len == 0) {
+	else {
 		rpc_authflavor_t new = nfs4_negotiate_security(dir, name);
 		if ((int)new >= 0)
 			flavor = new;