From e158e02ff70038936d374928a5484f16daa4c7d4 Mon Sep 17 00:00:00 2001 From: Sascha Hauer Date: Fri, 7 Sep 2018 14:36:42 +0200 Subject: 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: Sascha Hauer Signed-off-by: Richard Weinberger --- fs/ubifs/sb.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 69 insertions(+), 1 deletion(-) diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c index 5727565795327..7f0967771c9f7 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); -- cgit v1.2.3