Added partial support for new Kindle for PC

Author: Satsuoni

DeDRM_plugin/ion.py

@@ -810,6 +810,101 @@ def pkcs7unpad(msg, blocklen):
     "V5683": (0x05, b'z3\n\x039\x12\x13`\x06=v,\x02MTK\x1e%}L\x1c\x1f\x15\x0c\x11\x02\x0c\n8\x17p'),
 }
 
+def scramble3(st,magic):
+  ret=bytearray(len(st))
+  padlen=len(st)
+  divs = padlen // magic
+  cntr = 0
+  iVar6 = 0
+  offset = 0
+  if (0 < ((magic - 1) + divs)):
+    while True:
+      if (offset & 1) == 0 :
+        uVar4 = divs - 1
+        if offset < divs:
+          iVar3 = 0
+          uVar4 = offset
+        else:
+          iVar3 = (offset - divs) + 1
+        if uVar4>=0:
+          iVar5 = uVar4 * magic
+          index =  ((padlen - 1) - cntr)
+          while True:
+            if (magic <= iVar3): break
+            ret[index] = st[iVar3 + iVar5]
+            iVar3 = iVar3 + 1
+            cntr = cntr + 1
+            uVar4 = uVar4 - 1
+            iVar5 = iVar5 - magic
+            index -= 1
+            if uVar4<=-1: break
+      else: 
+        if (offset < magic):
+          iVar3 = 0
+        else :
+          iVar3 = (offset - magic) + 1
+        if (iVar3 < divs):
+          uVar4 = offset
+          if (magic <= offset):
+            uVar4 = magic - 1
+          
+          index = ((padlen - 1) - cntr)
+          iVar5 = iVar3 * magic
+          while True:
+            if (uVar4 < 0) : break
+            iVar3 += 1
+            ret[index] = st[uVar4 + iVar5]
+            uVar4 -= 1
+            index=index-1
+            iVar5 = iVar5 + magic;
+            cntr += 1;
+            if iVar3>=divs: break 
+      offset = offset + 1
+      if offset >= ((magic - 1) + divs) :break 
+  return ret
+  
+#not sure if the third variant is used anywhere, but it is in Kindle, so I tried to add it
+def obfuscate3(secret, version):
+    if version == 1:  # v1 does not use obfuscation
+        return secret
+    magic, word = OBFUSCATION_TABLE["V%d" % version]
+    # extend secret so that its length is divisible by the magic number
+    if len(secret) % magic != 0:
+        secret = secret + b'\x00' * (magic - len(secret) % magic)
+    #secret = bytearray(secret)
+    obfuscated = bytearray(len(secret))
+    wordhash = bytearray(hashlib.sha256(word).digest())
+    print(wordhash.hex())
+    shuffled=bytearray(scramble3(secret,magic))
+    print(shuffled)
+    # shuffle secret and xor it with the first half of the word hash
+    for i in range(0, len(secret)):
+        obfuscated[i] = shuffled[i] ^ wordhash[i % 16]
+    return obfuscated
+    
+def scramble(st,magic):
+  ret=bytearray(len(st))
+  padlen=len(st)
+  for counter in range(len(st)):
+    ivar2=(padlen//2)-2*(counter%magic)+magic+counter-1
+    ret[ivar2%padlen]=st[counter]
+  return ret
+  
+def obfuscate2(secret, version):
+    if version == 1:  # v1 does not use obfuscation
+        return secret
+    magic, word = OBFUSCATION_TABLE["V%d" % version]
+    # extend secret so that its length is divisible by the magic number
+    if len(secret) % magic != 0:
+        secret = secret + b'\x00' * (magic - len(secret) % magic)
+    obfuscated = bytearray(len(secret))
+    wordhash = bytearray(hashlib.sha256(word).digest()[16:])
+    print(wordhash.hex())
+    shuffled=bytearray(scramble(secret,magic))
+    # shuffle secret and xor it with the first half of the word hash
+    for i in range(0, len(secret)):
+        obfuscated[i] = shuffled[i] ^ wordhash[i % 16]
+    return obfuscated
 
 # obfuscate shared secret according to the VoucherEnvelope version
 def obfuscate(secret, version):
@@ -868,7 +963,6 @@ def __init__(self, voucherenv, dsn, secret):
 
     def decryptvoucher(self):
         shared = ("PIDv3" + self.encalgorithm + self.enctransformation + self.hashalgorithm).encode('ASCII')
-
         self.lockparams.sort()
         for param in self.lockparams:
             if param == "ACCOUNT_SECRET":
@@ -877,14 +971,24 @@ def decryptvoucher(self):
                 shared += param.encode('ASCII') + self.dsn
             else:
                 _assert(False, "Unknown lock parameter: %s" % param)
-
-        sharedsecret = obfuscate(shared, self.version)
-
-        key = hmac.new(sharedsecret, b"PIDv3", digestmod=hashlib.sha256).digest()
-        aes = AES.new(key[:32], AES.MODE_CBC, self.cipheriv[:16])
-        b = aes.decrypt(self.ciphertext)
-        b = pkcs7unpad(b, 16)
-
+        
+                
+        sharedsecrets = [obfuscate(shared, self.version),obfuscate2(shared, self.version),obfuscate3(shared, self.version)]
+        decrypted=False
+        ex=None
+        for sharedsecret in sharedsecrets:
+          key = hmac.new(sharedsecret, b"PIDv3", digestmod=hashlib.sha256).digest()
+          aes = AES.new(key[:32], AES.MODE_CBC, self.cipheriv[:16])
+          try:
+            b = aes.decrypt(self.ciphertext)
+            b = pkcs7unpad(b, 16)
+            decrypted=True 
+            print("Decryption succeeded")
+            break
+          except Exception as ex:
+            print("Decryption failed, trying next fallback ")
+        if not decrypted:
+          raise ex
         self.drmkey = BinaryIonParser(BytesIO(b))
         addprottable(self.drmkey)
 
@@ -923,6 +1027,7 @@ def parse(self):
         while self.envelope.hasnext():
             self.envelope.next()
             field = self.envelope.getfieldname()
+            print(field)
             if field == "voucher":
                 self.voucher = BinaryIonParser(BytesIO(self.envelope.lobvalue()))
                 addprottable(self.voucher)
@@ -936,6 +1041,10 @@ def parse(self):
             while self.envelope.hasnext():
                 self.envelope.next()
                 field = self.envelope.getfieldname()
+                try:
+                 print(self.envelope.stringvalue())
+                except:
+                 pass
                 if field == "encryption_algorithm":
                     self.encalgorithm = self.envelope.stringvalue()
                 elif field == "encryption_transformation":

README.md

@@ -1,3 +1,8 @@
+# Note
+
+Forked this for my own convenience. Release includes bugfixes from [noDRM](https://github.com/noDRM) that were not in latest release and partial support of Kindle for PC 1.40 .
+I will probably not maintain this, unless I need some functionality. 
+
 # DeDRM_tools
 DeDRM tools for ebooks