From cd9201d7f8fbca78c840e35881e205488eb3eae7 Mon Sep 17 00:00:00 2001
From: Nzix <iminezn5656@outlook.com>
Date: Thu, 18 Apr 2019 18:45:50 +0800
Subject: [PATCH] fit png format cover & empty meta data #14

---
 ncmdump.py | 89 ++++++++++++++++++++++++++----------------------------
 1 file changed, 42 insertions(+), 47 deletions(-)

diff --git a/ncmdump.py b/ncmdump.py
index 56662eb..923e4ed 100644
--- a/ncmdump.py
+++ b/ncmdump.py
@@ -5,18 +5,19 @@ Created on Sun Jul 15 01:05:58 2018
 @author: Nzix
 """
 
-import binascii
-import struct
-import base64
-import json
-import os
+import binascii, struct
+import base64, json
+import os, traceback
+
 from Crypto.Cipher import AES
 from Crypto.Util.strxor import strxor as XOR
 from mutagen import mp3, flac, id3
 
 def dump(input_path, output_path = None, skip = True):
 
-    output_path = (lambda path, meta : os.path.splitext(path)[0] + '.' + meta['format']) if not output_path else output_path
+    output_path = (lambda path, meta: os.path.splitext(path)[0] + '.' + meta['format']) if not output_path else output_path
+    output_path = (lambda path, meta: path) if not callable(output_path) else output_path
+
     core_key = binascii.a2b_hex('687A4852416D736F356B496E62617857')
     meta_key = binascii.a2b_hex('2331346C6A6B5F215C5D2630553C2728')
     unpad = lambda s : s[0:-(s[-1] if type(s[-1]) == int else ord(s[-1]))]
@@ -52,13 +53,16 @@ def dump(input_path, output_path = None, skip = True):
     meta_length = f.read(4)
     meta_length = struct.unpack('<I', bytes(meta_length))[0]
 
-    meta_data = bytearray(f.read(meta_length))
-    meta_data = bytes(bytearray([byte ^ 0x63 for byte in meta_data]))
-    meta_data = base64.b64decode(meta_data[22:])
+    if meta_length:
+        meta_data = bytearray(f.read(meta_length))
+        meta_data = bytes(bytearray([byte ^ 0x63 for byte in meta_data]))
+        meta_data = base64.b64decode(meta_data[22:])
 
-    cryptor = AES.new(meta_key, AES.MODE_ECB)
-    meta_data = unpad(cryptor.decrypt(meta_data)).decode('utf-8')[6:]
-    meta_data = json.loads(meta_data)
+        cryptor = AES.new(meta_key, AES.MODE_ECB)
+        meta_data = unpad(cryptor.decrypt(meta_data)).decode('utf-8')[6:]
+        meta_data = json.loads(meta_data)
+    else:
+        meta_data = {'format': 'flac' if os.fstat(f.fileno()).st_size > 1024 ** 2 * 16 else 'mp3'}
 
     # crc32
     crc32 = f.read(4)
@@ -68,7 +72,7 @@ def dump(input_path, output_path = None, skip = True):
     f.seek(5, 1)
     image_size = f.read(4)
     image_size = struct.unpack('<I', bytes(image_size))[0]
-    image_data = f.read(image_size)
+    image_data = f.read(image_size) if image_size else None
 
     # media data
     output_path = output_path(input_path, meta_data)
@@ -78,15 +82,6 @@ def dump(input_path, output_path = None, skip = True):
     f.close()
 
     # stream cipher (modified RC4 Pseudo-random generation algorithm)
-    # data = bytearray(data)
-    # i = 0
-    # j = 0
-    # for k, _ in enumerate(data):
-    #     i = (i + 1) % 256
-    #     j = (i + S[i]) % 256 # in RC4, is j = (j + S[i]) % 256
-    #     # S[i], S[j] = S[j], S[i] # no swapping
-    #     data[k] ^= S[(S[i] + S[j]) % 256]
-
     stream = [S[(S[i] + S[(i + S[i]) & 0xFF]) & 0xFF] for i in range(256)]
     stream = bytes(bytearray(stream * (len(data) // 256 + 1))[1:1 + len(data)])
     data = XOR(data, stream)
@@ -96,32 +91,32 @@ def dump(input_path, output_path = None, skip = True):
     m.close()
 
     # media tag
-    if meta_data['format'] == 'flac':
-        audio = flac.FLAC(output_path)
-        # audio.delete()
-        image = flac.Picture()
-        image.encoding = 0
-        image.type = 3
-        image.mime = 'image/jpeg'
-        image.data = image_data
-        audio.clear_pictures()
-        audio.add_picture(image)
-    elif meta_data['format'] == 'mp3':
-        audio = mp3.MP3(output_path)
-        # audio.delete()
-        image = id3.APIC()
-        image.encoding = 0
-        image.type = 3
-        image.mime = 'image/jpeg'
-        image.data = image_data
-        audio.tags.add(image)
+    def embed(item, content):
+        item.encoding = 0
+        item.type = 3
+        item.mime = 'image/png' if content[0:4] == binascii.a2b_hex('89504E47') else 'image/jpeg'
+        item.data = content
+    
+    if image_data:
+        if meta_data['format'] == 'flac':
+            audio = flac.FLAC(output_path)
+            image = flac.Picture()
+            embed(image, image_data)
+            audio.clear_pictures()
+            audio.add_picture(image)
+        elif meta_data['format'] == 'mp3':
+            audio = mp3.MP3(output_path)
+            image = id3.APIC()
+            embed(image, image_data)
+            audio.tags.add(image)
         audio.save()
-        audio = mp3.EasyMP3(output_path)
 
-    audio['title'] = meta_data['musicName']
-    audio['album'] = meta_data['album']
-    audio['artist'] = '/'.join([artist[0] for artist in meta_data['artist']])
-    audio.save()
+    if meta_length:
+        audio = flac.FLAC(output_path) if meta_data['format'] == 'flac' else mp3.EasyMP3(output_path)
+        audio['title'] = meta_data['musicName']
+        audio['album'] = meta_data['album']
+        audio['artist'] = '/'.join([artist[0] for artist in meta_data['artist']])
+        audio.save()
     
     return output_path
 
@@ -143,5 +138,5 @@ if __name__ == '__main__':
             dump(path)
             print(os.path.split(path)[-1])
         except Exception as e:
-            print(e)
+            print(traceback.format_exc())
             pass
\ No newline at end of file