crypto: check that LUKS PBKDF2 iterations count is non-zero

Both the master key and key slot passphrases are run through the PBKDF2
algorithm. The iterations count is expected to be generally very large
(many 10's or 100's of 1000s). It is hard to define a low level cutoff,
but we can certainly say that iterations count should be non-zero. A
zero count likely indicates an initialization mistake so reject it.

Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index e6ee8506b2e7b7a93a1c54752398cdd405f2b97f..254490c256d943244b02a4e7dd994d6d370d696d 100644 (file)
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -579,6 +579,11 @@ qcrypto_block_luks_check_header(const QCryptoBlockLUKS *luks, Error **errp)
         return -1;
     }
 
+    if (luks->header.master_key_iterations == 0) {
+        error_setg(errp, "LUKS key iteration count is zero");
+        return -1;
+    }
+
     /* Check all keyslots for corruption  */
     for (i = 0 ; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS ; i++) {
 
@@ -602,6 +607,12 @@ qcrypto_block_luks_check_header(const QCryptoBlockLUKS *luks, Error **errp)
             return -1;
         }
 
+        if (slot1->active == QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED &&
+            slot1->iterations == 0) {
+            error_setg(errp, "Keyslot %zu iteration count is zero", i);
+            return -1;
+        }
+
         if (start1 < DIV_ROUND_UP(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET,
                                   QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) {
             error_setg(errp,