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path: root/fs/ubifs/master.c
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Diffstat (limited to 'fs/ubifs/master.c')
-rw-r--r--fs/ubifs/master.c53
1 files changed, 47 insertions, 6 deletions
diff --git a/fs/ubifs/master.c b/fs/ubifs/master.c
index b42a768709c0..52a85c01397e 100644
--- a/fs/ubifs/master.c
+++ b/fs/ubifs/master.c
@@ -48,6 +48,39 @@ int ubifs_compare_master_node(struct ubifs_info *c, void *m1, void *m2)
return 0;
}
+/* mst_node_check_hash - Check hash of a master node
+ * @c: UBIFS file-system description object
+ * @mst: The master node
+ * @expected: The expected hash of the master node
+ *
+ * This checks the hash of a master node against a given expected hash.
+ * Note that we have two master nodes on a UBIFS image which have different
+ * sequence numbers and consequently different CRCs. To be able to match
+ * both master nodes we exclude the common node header containing the sequence
+ * number and CRC from the hash.
+ *
+ * Returns 0 if the hashes are equal, a negative error code otherwise.
+ */
+static int mst_node_check_hash(const struct ubifs_info *c,
+ const struct ubifs_mst_node *mst,
+ const u8 *expected)
+{
+ u8 calc[UBIFS_MAX_HASH_LEN];
+ const void *node = mst;
+
+ SHASH_DESC_ON_STACK(shash, c->hash_tfm);
+
+ shash->tfm = c->hash_tfm;
+
+ crypto_shash_digest(shash, node + sizeof(struct ubifs_ch),
+ UBIFS_MST_NODE_SZ - sizeof(struct ubifs_ch), calc);
+
+ if (ubifs_check_hash(c, expected, calc))
+ return -EPERM;
+
+ return 0;
+}
+
/**
* scan_for_master - search the valid master node.
* @c: UBIFS file-system description object
@@ -102,14 +135,22 @@ static int scan_for_master(struct ubifs_info *c)
if (!ubifs_authenticated(c))
return 0;
- err = ubifs_node_verify_hmac(c, c->mst_node,
- sizeof(struct ubifs_mst_node),
- offsetof(struct ubifs_mst_node, hmac));
- if (err) {
- ubifs_err(c, "Failed to verify master node HMAC");
- return -EPERM;
+ if (ubifs_hmac_zero(c, c->mst_node->hmac)) {
+ err = mst_node_check_hash(c, c->mst_node,
+ c->sup_node->hash_mst);
+ if (err)
+ ubifs_err(c, "Failed to verify master node hash");
+ } else {
+ err = ubifs_node_verify_hmac(c, c->mst_node,
+ sizeof(struct ubifs_mst_node),
+ offsetof(struct ubifs_mst_node, hmac));
+ if (err)
+ ubifs_err(c, "Failed to verify master node HMAC");
}
+ if (err)
+ return -EPERM;
+
return 0;
out: