Add Checksum verification to InstallAssistant.pkg download

resources/integrity_verification.py

@@ -0,0 +1,67 @@
+# Validate the integrity of Apple downloaded files via .chunklist and .integrityDataV1 files
+# Based off of chunklist.py:
+# - https://gist.github.com/dhinakg/cbe30edf31ddc153fd0b0c0570c9b041
+# Copyright (C) 2021-2022, Dhinak G, Mykola Grymalyuk
+
+import binascii
+import hashlib
+import struct
+from pathlib import Path
+
+CHUNK_LENGTH = 4 + 32
+
+
+def hexswap(i):
+    return struct.unpack("<I", struct.pack(">I", i))[0]
+
+
+def generate_chunklist_dict(chunklist):
+    chunklist = Path(chunklist).read_bytes() if isinstance(chunklist, str) else chunklist
+
+    header = {
+        "magic":       chunklist[:4],
+        "length":      int.from_bytes(chunklist[4:8], "little"),
+        "fileVersion": chunklist[8],
+        "chunkMethod": chunklist[9],
+        "sigMethod":   chunklist[10],
+        "chunkCount":  int.from_bytes(chunklist[12:20], "little"),
+        "chunkOffset": int.from_bytes(chunklist[20:28], "little"),
+        "sigOffset":   int.from_bytes(chunklist[28:36], "little")
+    }
+
+    all_chunks = chunklist[header["chunkOffset"]:header["chunkOffset"]+header["chunkCount"]*CHUNK_LENGTH]
+    chunks = [{"length": int.from_bytes(all_chunks[i:i+4], "little"), "checksum": all_chunks[i+4:i+CHUNK_LENGTH]} for i in range(0, len(all_chunks), CHUNK_LENGTH)]
+
+    return chunks
+
+
+def chunk(file_path, chunklist, verbose):
+    chunklist = Path(chunklist).read_bytes() if isinstance(
+        chunklist, str) else chunklist
+
+    header = {
+        "magic": chunklist[:4],
+        "length": int.from_bytes(chunklist[4:8], "little"),
+        "fileVersion": chunklist[8],
+        "chunkMethod": chunklist[9],
+        "sigMethod": chunklist[10],
+        "chunkCount": int.from_bytes(chunklist[12:20], "little"),
+        "chunkOffset": int.from_bytes(chunklist[20:28], "little"),
+        "sigOffset": int.from_bytes(chunklist[28:36], "little")
+    }
+
+    all_chunks = chunklist[header["chunkOffset"]:header["chunkOffset"]+header["chunkCount"]*CHUNK_LENGTH]
+    chunks = [{"length": int.from_bytes(all_chunks[i:i+4], "little"), "checksum": all_chunks[i+4:i+CHUNK_LENGTH]}
+              for i in range(0, len(all_chunks), CHUNK_LENGTH)]
+
+    with Path(file_path).open("rb") as f:
+        for chunk in chunks:
+            status = hashlib.sha256(f.read(chunk["length"])).digest()
+            if not status == chunk["checksum"]:
+                print(
+                    f"Chunk {chunks.index(chunk) + 1} checksum status FAIL: chunk sum {binascii.hexlify(chunk['checksum']).decode()}, calculated sum {binascii.hexlify(status).decode()}")
+                return False
+            elif verbose:
+                print(
+                    f"Chunk {chunks.index(chunk) + 1} checksum status success")
+    return True