1 files changed, 42 insertions, 0 deletions
diff --git a/samloader/crypt.py b/samloader/crypt.py
new file mode 100644
index 0000000..d5cf6de
--- /dev/null
+++ b/samloader/crypt.py
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2020 Nayil Mukhametshin
+
+# Calculate keys and decrypt encrypted firmware packages.
+
+import hashlib
+import xml.etree.ElementTree as ET
+from Crypto.Cipher import AES
+from clint.textui import progress
+
+from . import request
+from . import fusclient
+from . import versionfetch
+
+unpad = lambda d: d[:-d[-1]]
+
+def getv4key(version, model, region):
+    client = fusclient.FUSClient()
+    req = request.binaryinform(version, region, model, client.nonce)
+    resp = client.makereq("NF_DownloadBinaryInform.do", req)
+    root = ET.fromstring(resp)
+    logicval = root.find("./FUSBody/Put/LOGIC_VALUE_FACTORY/Data").text
+    deckey = request.getlogiccheck(version, logicval)
+    return hashlib.md5(deckey.encode()).digest()
+
+def getv2key(version, model, region):
+    deckey = region + ":" + model + ":" + version
+    return hashlib.md5(deckey.encode()).digest()
+
+def decrypt_progress(inf, outf, key, length):
+    cipher = AES.new(key, AES.MODE_ECB)
+    assert length % 16 == 0
+    chunks = length//4096+1
+    for i in progress.bar(range(chunks)):
+        block = inf.read(4096)
+        if not block:
+            break
+        decblock = cipher.decrypt(block)
+        if i == chunks - 1:
+            outf.write(unpad(decblock))
+        else:
+            outf.write(decblock)