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Commit e158e02f authored by Sascha Hauer's avatar Sascha Hauer Committed by Richard Weinberger
Browse files

ubifs: authentication: Authenticate super block node 



This adds a HMAC covering the super block node and adds the logic that
decides if a filesystem shall be mounted unauthenticated or
authenticated.

Signed-off-by: default avatarSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent b5b1f083

fs/ubifs/sb.c

+69 −1
Original line number Diff line number Diff line
@@ -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);