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>

5 files changed, 143 insertions, 70 deletions

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index c8cd044f0982..bca6a3e3c49c 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -326,6 +326,7 @@ extern struct file_system_type nfs_xdev_fs_type;
 extern struct file_system_type nfs4_xdev_fs_type;
 extern struct file_system_type nfs4_referral_fs_type;
 #endif
+bool nfs_auth_info_match(const struct nfs_auth_info *, rpc_authflavor_t);
 struct dentry *nfs_try_mount(int, const char *, struct nfs_mount_info *,
                         struct nfs_subversion *);
 void nfs_initialise_sb(struct super_block *);
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index f6cc77c7d802..b4a160a405ce 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -964,6 +964,9 @@ static int nfs4_init_server(struct nfs_server *server,
         server->options = data->options;
         server->auth_info = data->auth_info;
 
+        /* Use the first specified auth flavor. If this flavor isn't
+         * allowed by the server, use the SECINFO path to try the
+         * other specified flavors */
         if (data->auth_info.flavor_len >= 1)
                 data->selected_flavor = data->auth_info.flavors[0];
         else
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;
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 0eb8dc5792da..b02c4cc7b0a9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2873,11 +2873,24 @@ static int nfs4_find_root_sec(struct nfs_server *server, struct nfs_fh *fhandle,
         int status = -EPERM;
         size_t i;
 
-        for (i = 0; i < ARRAY_SIZE(flav_array); i++) {
-                status = nfs4_lookup_root_sec(server, fhandle, info, flav_array[i]);
-                if (status == -NFS4ERR_WRONGSEC || status == -EACCES)
-                        continue;
-                break;
+        if (server->auth_info.flavor_len > 0) {
+                /* try each flavor specified by user */
+                for (i = 0; i < server->auth_info.flavor_len; i++) {
+                        status = nfs4_lookup_root_sec(server, fhandle, info,
+                                                server->auth_info.flavors[i]);
+                        if (status == -NFS4ERR_WRONGSEC || status == -EACCES)
+                                continue;
+                        break;
+                }
+        } else {
+                /* no flavors specified by user, try default list */
+                for (i = 0; i < ARRAY_SIZE(flav_array); i++) {
+                        status = nfs4_lookup_root_sec(server, fhandle, info,
+                                                      flav_array[i]);
+                        if (status == -NFS4ERR_WRONGSEC || status == -EACCES)
+                                continue;
+                        break;
+                }
         }
 
         /*
@@ -2919,9 +2932,6 @@ int nfs4_proc_get_rootfh(struct nfs_server *server, struct nfs_fh *fhandle,
                 status = nfs4_lookup_root(server, fhandle, info);
                 if (status != -NFS4ERR_WRONGSEC)
                         break;
-                /* Did user force a 'sec=' mount option? */
-                if (server->auth_info.flavor_len > 0)
-                        break;
         default:
                 status = nfs4_do_find_root_sec(server, fhandle, info);
         }
@@ -3179,9 +3189,6 @@ static int nfs4_proc_lookup_common(struct rpc_clnt **clnt, struct inode *dir,
                         err = -EPERM;
                         if (client != *clnt)
                                 goto out;
-                        /* No security negotiation if the user specified 'sec=' */
-                        if (NFS_SERVER(dir)->auth_info.flavor_len > 0)
-                                goto out;
                         client = nfs4_create_sec_client(client, dir, name);
                         if (IS_ERR(client))
                                 return PTR_ERR(client);
@@ -7942,6 +7949,9 @@ nfs41_find_root_sec(struct nfs_server *server, struct nfs_fh *fhandle,
                         break;
                 }
 
+                if (!nfs_auth_info_match(&server->auth_info, flavor))
+                        flavor = RPC_AUTH_MAXFLAVOR;
+
                 if (flavor != RPC_AUTH_MAXFLAVOR) {
                         err = nfs4_lookup_root_sec(server, fhandle,
                                                    info, flavor);
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 3a4f8bf5e5a5..317d6fc2160e 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -497,7 +497,8 @@ static const char *nfs_pseudoflavour_to_name(rpc_authflavor_t flavour)
         static const struct {
                 rpc_authflavor_t flavour;
                 const char *str;
-        } sec_flavours[] = {
+        } sec_flavours[NFS_AUTH_INFO_MAX_FLAVORS] = {
+                /* update NFS_AUTH_INFO_MAX_FLAVORS when this list changes! */
                 { RPC_AUTH_NULL, "null" },
                 { RPC_AUTH_UNIX, "sys" },
                 { RPC_AUTH_GSS_KRB5, "krb5" },
@@ -1019,6 +1020,52 @@ static void nfs_set_mount_transport_protocol(struct nfs_parsed_mount_data *mnt)
 }
 
 /*
+ * Add 'flavor' to 'auth_info' if not already present.
+ * Returns true if 'flavor' ends up in the list, false otherwise
+ */
+static bool nfs_auth_info_add(struct nfs_auth_info *auth_info,
+                              rpc_authflavor_t flavor)
+{
+        unsigned int i;
+        unsigned int max_flavor_len = (sizeof(auth_info->flavors) /
+                                       sizeof(auth_info->flavors[0]));
+
+        /* make sure this flavor isn't already in the list */
+        for (i = 0; i < auth_info->flavor_len; i++) {
+                if (flavor == auth_info->flavors[i])
+                        return true;
+        }
+
+        if (auth_info->flavor_len + 1 >= max_flavor_len) {
+                dfprintk(MOUNT, "NFS: too many sec= flavors\n");
+                return false;
+        }
+
+        auth_info->flavors[auth_info->flavor_len++] = flavor;
+        return true;
+}
+
+/*
+ * Return true if 'match' is in auth_info or auth_info is empty.
+ * Return false otherwise.
+ */
+bool nfs_auth_info_match(const struct nfs_auth_info *auth_info,
+                         rpc_authflavor_t match)
+{
+        int i;
+
+        if (!auth_info->flavor_len)
+                return true;
+
+        for (i = 0; i < auth_info->flavor_len; i++) {
+                if (auth_info->flavors[i] == match)
+                        return true;
+        }
+        return false;
+}
+EXPORT_SYMBOL_GPL(nfs_auth_info_match);
+
+/*
  * Parse the value of the 'sec=' option.
  */
 static int nfs_parse_security_flavors(char *value,
@@ -1026,49 +1073,55 @@ static int nfs_parse_security_flavors(char *value,
 {
         substring_t args[MAX_OPT_ARGS];
         rpc_authflavor_t pseudoflavor;
+        char *p;
 
         dfprintk(MOUNT, "NFS: parsing sec=%s option\n", value);
 
-        switch (match_token(value, nfs_secflavor_tokens, args)) {
-        case Opt_sec_none:
-                pseudoflavor = RPC_AUTH_NULL;
-                break;
-        case Opt_sec_sys:
-                pseudoflavor = RPC_AUTH_UNIX;
-                break;
-        case Opt_sec_krb5:
-                pseudoflavor = RPC_AUTH_GSS_KRB5;
-                break;
-        case Opt_sec_krb5i:
-                pseudoflavor = RPC_AUTH_GSS_KRB5I;
-                break;
-        case Opt_sec_krb5p:
-                pseudoflavor = RPC_AUTH_GSS_KRB5P;
-                break;
-        case Opt_sec_lkey:
-                pseudoflavor = RPC_AUTH_GSS_LKEY;
-                break;
-        case Opt_sec_lkeyi:
-                pseudoflavor = RPC_AUTH_GSS_LKEYI;
-                break;
-        case Opt_sec_lkeyp:
-                pseudoflavor = RPC_AUTH_GSS_LKEYP;
-                break;
-        case Opt_sec_spkm:
-                pseudoflavor = RPC_AUTH_GSS_SPKM;
-                break;
-        case Opt_sec_spkmi:
-                pseudoflavor = RPC_AUTH_GSS_SPKMI;
-                break;
-        case Opt_sec_spkmp:
-                pseudoflavor = RPC_AUTH_GSS_SPKMP;
-                break;
-        default:
-                return 0;
+        while ((p = strsep(&value, ":")) != NULL) {
+                switch (match_token(p, nfs_secflavor_tokens, args)) {
+                case Opt_sec_none:
+                        pseudoflavor = RPC_AUTH_NULL;
+                        break;
+                case Opt_sec_sys:
+                        pseudoflavor = RPC_AUTH_UNIX;
+                        break;
+                case Opt_sec_krb5:
+                        pseudoflavor = RPC_AUTH_GSS_KRB5;
+                        break;
+                case Opt_sec_krb5i:
+                        pseudoflavor = RPC_AUTH_GSS_KRB5I;
+                        break;
+                case Opt_sec_krb5p:
+                        pseudoflavor = RPC_AUTH_GSS_KRB5P;
+                        break;
+                case Opt_sec_lkey:
+                        pseudoflavor = RPC_AUTH_GSS_LKEY;
+                        break;
+                case Opt_sec_lkeyi:
+                        pseudoflavor = RPC_AUTH_GSS_LKEYI;
+                        break;
+                case Opt_sec_lkeyp:
+                        pseudoflavor = RPC_AUTH_GSS_LKEYP;
+                        break;
+                case Opt_sec_spkm:
+                        pseudoflavor = RPC_AUTH_GSS_SPKM;
+                        break;
+                case Opt_sec_spkmi:
+                        pseudoflavor = RPC_AUTH_GSS_SPKMI;
+                        break;
+                case Opt_sec_spkmp:
+                        pseudoflavor = RPC_AUTH_GSS_SPKMP;
+                        break;
+                default:
+                        dfprintk(MOUNT,
+                                 "NFS: sec= option '%s' not recognized\n", p);
+                        return 0;
+                }
+
+                if (!nfs_auth_info_add(&mnt->auth_info, pseudoflavor))
+                        return 0;
         }
 
-        mnt->auth_info.flavors[0] = pseudoflavor;
-        mnt->auth_info.flavor_len = 1;
         return 1;
 }
 
@@ -1615,12 +1668,14 @@ out_security_failure:
 }
 
 /*
- * Ensure that the specified authtype in args->auth_info is supported by
- * the server. Returns 0 if it's ok, and -EACCES if not.
+ * Ensure that a specified authtype in args->auth_info is supported by
+ * the server. Returns 0 and sets args->selected_flavor if it's ok, and
+ * -EACCES if not.
  */
-static int nfs_verify_authflavor(struct nfs_parsed_mount_data *args,
+static int nfs_verify_authflavors(struct nfs_parsed_mount_data *args,
                         rpc_authflavor_t *server_authlist, unsigned int count)
 {
+        rpc_authflavor_t flavor = RPC_AUTH_MAXFLAVOR;
         unsigned int i;
 
         /*
@@ -1632,17 +1687,19 @@ static int nfs_verify_authflavor(struct nfs_parsed_mount_data *args,
          * can be used.
          */
         for (i = 0; i < count; i++) {
-                if (args->auth_info.flavors[0] == server_authlist[i] ||
-                    server_authlist[i] == RPC_AUTH_NULL)
+                flavor = server_authlist[i];
+
+                if (nfs_auth_info_match(&args->auth_info, flavor) ||
+                    flavor == RPC_AUTH_NULL)
                         goto out;
         }
 
-        dfprintk(MOUNT, "NFS: auth flavor %u not supported by server\n",
-                args->auth_info.flavors[0]);
+        dfprintk(MOUNT,
+                 "NFS: specified auth flavors not supported by server\n");
         return -EACCES;
 
 out:
-        args->selected_flavor = args->auth_info.flavors[0];
+        args->selected_flavor = flavor;
         dfprintk(MOUNT, "NFS: using auth flavor %u\n", args->selected_flavor);
         return 0;
 }
@@ -1732,7 +1789,7 @@ static struct nfs_server *nfs_try_mount_request(struct nfs_mount_info *mount_inf
          * whether the server supports it, and then just try to use it if so.
          */
         if (args->auth_info.flavor_len > 0) {
-                status = nfs_verify_authflavor(args, authlist, authlist_len);
+                status = nfs_verify_authflavors(args, authlist, authlist_len);
                 dfprintk(MOUNT, "NFS: using auth flavor %u\n",
                          args->selected_flavor);
                 if (status)
@@ -2102,9 +2159,6 @@ static int nfs_validate_text_mount_data(void *options,
 
         nfs_set_port(sap, &args->nfs_server.port, port);
 
-        if (args->auth_info.flavor_len > 1)
-                goto out_bad_auth;
-
         return nfs_parse_devname(dev_name,
                                    &args->nfs_server.hostname,
                                    max_namelen,
@@ -2124,10 +2178,6 @@ out_invalid_transport_udp:
 out_no_address:
         dfprintk(MOUNT, "NFS: mount program didn't pass remote address\n");
         return -EINVAL;
-
-out_bad_auth:
-        dfprintk(MOUNT, "NFS: Too many RPC auth flavours specified\n");
-        return -EINVAL;
 }
 
 static int