1 files changed, 69 insertions, 1 deletions

diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 572756579532..7f0967771c9f 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -517,6 +517,65 @@ static struct ubifs_sb_node *ubifs_read_sb_node(struct ubifs_info *c)
         return sup;
 }
 
+static int authenticate_sb_node(struct ubifs_info *c,
+                                const struct ubifs_sb_node *sup)
+{
+        unsigned int sup_flags = le32_to_cpu(sup->flags);
+        u8 hmac_wkm[UBIFS_HMAC_ARR_SZ];
+        int authenticated = !!(sup_flags & UBIFS_FLG_AUTHENTICATION);
+        int hash_algo;
+        int err;
+
+        if (c->authenticated && !authenticated) {
+                ubifs_err(c, "authenticated FS forced, but found FS without authentication");
+                return -EINVAL;
+        }
+
+        if (!c->authenticated && authenticated) {
+                ubifs_err(c, "authenticated FS found, but no key given");
+                return -EINVAL;
+        }
+
+        ubifs_msg(c, "Mounting in %sauthenticated mode",
+                  c->authenticated ? "" : "un");
+
+        if (!c->authenticated)
+                return 0;
+
+        if (!IS_ENABLED(CONFIG_UBIFS_FS_AUTHENTICATION))
+                return -EOPNOTSUPP;
+
+        hash_algo = le16_to_cpu(sup->hash_algo);
+        if (hash_algo >= HASH_ALGO__LAST) {
+                ubifs_err(c, "superblock uses unknown hash algo %d",
+                          hash_algo);
+                return -EINVAL;
+        }
+
+        if (strcmp(hash_algo_name[hash_algo], c->auth_hash_name)) {
+                ubifs_err(c, "This filesystem uses %s for hashing,"
+                             " but %s is specified", hash_algo_name[hash_algo],
+                             c->auth_hash_name);
+                return -EINVAL;
+        }
+
+        err = ubifs_hmac_wkm(c, hmac_wkm);
+        if (err)
+                return err;
+
+        if (ubifs_check_hmac(c, hmac_wkm, sup->hmac_wkm)) {
+                ubifs_err(c, "provided key does not fit");
+                return -ENOKEY;
+        }
+
+        err = ubifs_node_verify_hmac(c, sup, sizeof(*sup),
+                                     offsetof(struct ubifs_sb_node, hmac));
+        if (err)
+                ubifs_err(c, "Failed to authenticate superblock: %d", err);
+
+        return err;
+}
+
 /**
  * ubifs_write_sb_node - write superblock node.
  * @c: UBIFS file-system description object
@@ -527,8 +586,13 @@ static struct ubifs_sb_node *ubifs_read_sb_node(struct ubifs_info *c)
 int ubifs_write_sb_node(struct ubifs_info *c, struct ubifs_sb_node *sup)
 {
         int len = ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size);
+        int err;
+
+        err = ubifs_prepare_node_hmac(c, sup, UBIFS_SB_NODE_SZ,
+                                      offsetof(struct ubifs_sb_node, hmac), 1);
+        if (err)
+                return err;
 
-        ubifs_prepare_node(c, sup, UBIFS_SB_NODE_SZ, 1);
         return ubifs_leb_change(c, UBIFS_SB_LNUM, sup, len);
 }
 
@@ -642,6 +706,10 @@ int ubifs_read_superblock(struct ubifs_info *c)
         c->double_hash = !!(sup_flags & UBIFS_FLG_DOUBLE_HASH);
         c->encrypted = !!(sup_flags & UBIFS_FLG_ENCRYPTION);
 
+        err = authenticate_sb_node(c, sup);
+        if (err)
+                goto out;
+
         if ((sup_flags & ~UBIFS_FLG_MASK) != 0) {
                 ubifs_err(c, "Unknown feature flags found: %#x",
                           sup_flags & ~UBIFS_FLG_MASK);