[PATCH v2 12/13] qcrypto-luks: more rigorous header checking

[Maxim Levitsky <mlevitsk@redhat.com>]

Check that keyslots don't overlap with the data,
and check that keyslots don't overlap with each other.
(this is done using naive O(n^2) nested loops,
but since there are just 8 keyslots, this doesn't really matter.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 crypto/block-luks.c | 52 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index a53d5d1916..4861db810c 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -530,6 +530,11 @@ qcrypto_block_luks_load_header(QCryptoBlock *block,
 static int
 qcrypto_block_luks_check_header(const QCryptoBlockLUKS *luks, Error **errp)
 {
+    size_t i, j;
+
+    unsigned int header_sectors = QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
+        QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
+
     if (memcmp(luks->header.magic, qcrypto_block_luks_magic,
                QCRYPTO_BLOCK_LUKS_MAGIC_LEN) != 0) {
         error_setg(errp, "Volume is not in LUKS format");
@@ -541,6 +546,53 @@ qcrypto_block_luks_check_header(const QCryptoBlockLUKS *luks, Error **errp)
                    luks->header.version);
         return -1;
     }
+
+    /* Check all keyslots for corruption  */
+    for (i = 0 ; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS ; i++) {
+
+        const QCryptoBlockLUKSKeySlot *slot1 = &luks->header.key_slots[i];
+        unsigned int start1 = slot1->key_offset_sector;
+        unsigned int len1 =
+            qcrypto_block_luks_splitkeylen_sectors(luks,
+                                                   header_sectors,
+                                                   slot1->stripes);
+
+        if (slot1->stripes == 0) {
+            error_setg(errp, "Keyslot %zu is corrupted (stripes == 0)", i);
+            return -1;
+        }
+
+        if (slot1->active != QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED &&
+            slot1->active != QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED) {
+            error_setg(errp,
+                       "Keyslot %zu state (active/disable) is corrupted", i);
+            return -1;
+        }
+
+        if (start1 + len1 > luks->header.payload_offset_sector) {
+            error_setg(errp,
+                       "Keyslot %zu is overlapping with the encrypted payload",
+                       i);
+            return -1;
+        }
+
+        for (j = i + 1 ; j < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS ; j++) {
+            const QCryptoBlockLUKSKeySlot *slot2 = &luks->header.key_slots[j];
+            unsigned int start2 = slot2->key_offset_sector;
+            unsigned int len2 =
+                qcrypto_block_luks_splitkeylen_sectors(luks,
+                                                       header_sectors,
+                                                       slot2->stripes);
+
+            if (start1 + len1 > start2 && start2 + len2 > start1) {
+                error_setg(errp,
+                           "Keyslots %zu and %zu are overlapping in the header",
+                           i, j);
+                return -1;
+            }
+        }
+
+    }
     return 0;
 }
 
-- 
2.17.2