First version of mobidedrm

Kindle_Mobi_Tools/lib/mobidedrm.py

@@ -0,0 +1,150 @@
+import sys,struct,binascii
+
+class DrmException(Exception):
+	pass
+
+#implementation of Pukall Cipher 1
+def PC1(key, src, decryption=True):
+    sum1 = 0;
+    sum2 = 0;
+    keyXorVal = 0;
+    if len(key)!=16:
+        print "Bad key length!"
+        return None
+    wkey = []
+    for i in xrange(8):
+        wkey.append(ord(key[i*2])<<8 | ord(key[i*2+1]))
+
+    dst = ""
+    for i in xrange(len(src)):
+        temp1 = 0;
+        byteXorVal = 0;
+        for j in xrange(8):
+            temp1 ^= wkey[j]
+            sum2  = (sum2+j)*20021 + sum1
+            sum1  = (temp1*346)&0xFFFF
+            sum2  = (sum2+sum1)&0xFFFF
+            temp1 = (temp1*20021+1)&0xFFFF
+            byteXorVal ^= temp1 ^ sum2
+        curByte = ord(src[i])
+        if not decryption:
+            keyXorVal = curByte * 257;
+        curByte = ((curByte ^ (byteXorVal >> 8)) ^ byteXorVal) & 0xFF
+        if decryption:
+            keyXorVal = curByte * 257;
+        for j in xrange(8):
+            wkey[j] ^= keyXorVal;
+        dst+=chr(curByte)
+    return dst
+
+def checksumPid(s):
+	letters = "ABCDEFGHIJKLMNPQRSTUVWXYZ123456789"
+	crc = (~binascii.crc32(s,-1))&0xFFFFFFFF 
+	crc = crc ^ (crc >> 16)
+	res = s
+	l = len(letters)
+	for i in (0,1):
+		b = crc & 0xff
+		pos = (b // l) ^ (b % l)
+		res += letters[pos%l]
+		crc >>= 8
+	return res
+
+class DrmStripper:
+	def loadSection(self, section):	
+		if (section + 1 == self.num_sections):
+			endoff = len(self.data_file)
+		else:
+			endoff = self.sections[section + 1][0]
+		off = self.sections[section][0]
+		return self.data_file[off:endoff]
+
+	def patch(self, off, new):	
+		self.data_file = self.data_file[:off] + new + self.data_file[off+len(new):]
+
+	def patchSection(self, section, new, in_off = 0):
+		if (section + 1 == self.num_sections):
+			endoff = len(self.data_file)
+		else:
+			endoff = self.sections[section + 1][0]
+		off = self.sections[section][0]
+		assert off + in_off + len(new) <= endoff
+		self.patch(off + in_off, new)
+
+	def parseDRM(self, data, count, pid):
+		pid = pid.ljust(16,'\0')
+		keyvec1 = "\x72\x38\x33\xB0\xB4\xF2\xE3\xCA\xDF\x09\x01\xD6\xE2\xE0\x3F\x96"
+		temp_key = PC1(keyvec1, pid, False)
+		temp_key_sum = sum(map(ord,temp_key)) & 0xff
+		found_key = None
+		for i in xrange(count):
+			verification, size, type, cksum, cookie = struct.unpack('>LLLBxxx32s', data[i*0x30:i*0x30+0x30])
+			cookie = PC1(temp_key, cookie)
+			ver,flags,finalkey,expiry,expiry2 = struct.unpack('>LL16sLL', cookie)
+			if verification == ver and cksum == temp_key_sum and (flags & 0x1F) == 1:
+				found_key = finalkey
+				break
+		return found_key		
+
+
+	def __init__(self, data_file, pid):
+
+		if checksumPid(pid[0:-2]) != pid:
+			raise DrmException("invalid PID checksum")
+		pid = pid[0:-2]
+		
+		self.data_file = data_file
+		header = data_file[0:72]
+		if header[0x3C:0x3C+8] != 'BOOKMOBI':
+			raise DrmException("invalid file format")
+		self.num_sections, = struct.unpack('>H', data_file[76:78])
+
+		self.sections = []
+		for i in xrange(self.num_sections):
+			offset, a1,a2,a3,a4 = struct.unpack('>LBBBB', data_file[78+i*8:78+i*8+8])
+			flags, val = a1, a2<<16|a3<<8|a4
+			self.sections.append( (offset, flags, val) )
+
+		sect = self.loadSection(0)
+		records, = struct.unpack('>H', sect[0x8:0x8+2])
+
+		crypto_type, = struct.unpack('>H', sect[0xC:0xC+2])
+		if crypto_type != 2:
+			raise DrmException("invalid encryption type: %d" % crypto_type)
+
+		# calculate the keys
+		drm_ptr, drm_count, drm_size, drm_flags = struct.unpack('>LLLL', sect[0xA8:0xA8+16])
+		found_key = self.parseDRM(sect[drm_ptr:drm_ptr+drm_size], drm_count, pid)
+		if not found_key:
+			raise DrmException("no key found. maybe the PID is incorrect")
+
+		# kill the drm keys
+		self.patchSection(0, "\0" * drm_size, drm_ptr)
+		# kill the drm pointers
+		self.patchSection(0, "\xff" * 4 + "\0" * 12, 0xA8)
+		# clear the crypto type
+		self.patchSection(0, "\0" * 2, 0xC)
+
+		# decrypt sections
+		print "Decrypting. Please wait...",
+		for i in xrange(1, records+1):
+			self.patchSection(i, PC1(found_key, self.loadSection(i)))
+		print "done"
+	def getResult(self):
+		return self.data_file
+
+
+
+print "MobiDeDrm v0.01. Copyright (c) 2008 The Dark Reverser"
+if len(sys.argv)<4:
+	print "Removes protection from Mobipocket books"
+	print "Usage: mobidedrm infile.mobi outfile.mobi PID"
+else:  
+	infile = sys.argv[1]
+	outfile = sys.argv[2]
+	pid = sys.argv[3]
+	data_file = file(infile, 'rb').read()
+	try:
+		file(outfile, 'wb').write(DrmStripper(data_file, pid).getResult())
+	except DrmException, e:
+		print "Error: %s" % e