Detection of misaligned value of 1st blob offset in cluster

Author: veloman-yunkan

src/cluster.cpp

@@ -108,6 +108,10 @@ getClusterReader(const Reader& zimReader, offset_t offset, Cluster::Compression*
 
     size_t n_offset = offset / sizeof(OFFSET_TYPE);
 
+    if ( n_offset * sizeof(OFFSET_TYPE) != offset ) {
+        throw zim::ZimFileFormatError("Error parsing cluster. Offset of the first blob is not properly aligned.");
+    }
+
     // read offsets
     m_blobOffsets.clear();
     m_blobOffsets.reserve(n_offset);

test/archive.cpp

@@ -806,6 +806,21 @@ TEST_F(ZimArchive, validate)
      "Error parsing cluster. Offset of the first blob is too small.\n"
   )
 
+  TEST_BROKEN_ZIM_NAME(
+    "invalid.misaligned_offset_of_first_blob_in_cluster_9.zim",
+     "Error parsing cluster. Offset of the first blob is not properly aligned.\n"
+  )
+
+  TEST_BROKEN_ZIM_NAME(
+    "invalid.misaligned_offset_of_first_blob_in_cluster_10.zim",
+     "Error parsing cluster. Offset of the first blob is not properly aligned.\n"
+  )
+
+  TEST_BROKEN_ZIM_NAME(
+    "invalid.misaligned_offset_of_first_blob_in_cluster_11.zim",
+     "Error parsing cluster. Offset of the first blob is not properly aligned.\n"
+  )
+
   TEST_BROKEN_ZIM_NAME(
     "invalid.offset_in_cluster.zim",
      "Error parsing cluster. Offsets are not ordered.\n"