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ubifs: authentication: Authenticate super block node

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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 <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Sascha Hauer 2018-09-07 14:36:42 +02:00 committed by Richard Weinberger
parent b5b1f08369
commit e158e02ff7
1 changed files with 69 additions and 1 deletions
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70
fs/ubifs/sb.c
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@ -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);