From be59293def314adcf24810c2ad42cf5218f71e7a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mike=20F=C3=A4hrmann?= <mike_faehrmann@web.de>
Date: Wed, 25 Nov 2020 11:26:26 +0100
Subject: [PATCH] [hentainexus] update data decoding procedure (#1125)

---
 gallery_dl/extractor/hentainexus.py | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/gallery_dl/extractor/hentainexus.py b/gallery_dl/extractor/hentainexus.py
index e08bb72880b..a6db0d50e71 100644
--- a/gallery_dl/extractor/hentainexus.py
+++ b/gallery_dl/extractor/hentainexus.py
@@ -73,11 +73,25 @@ def images(self, _):
 
     @staticmethod
     def _decode(data):
+        # https://hentainexus.com/static/js/reader.min.js?r=6
         blob = binascii.a2b_base64(data)
-        return "".join(
-            chr(blob[i] ^ blob[i-64])
-            for i in range(64, len(blob))
-        )
+        key = blob[0:64]
+        indices = list(range(256))
+        result = ""
+
+        x = 0
+        for i in range(256):
+            x = (x + indices[i] + key[i % len(key)]) % 256
+            indices[i], indices[x] = indices[x], indices[i]
+
+        x = i = 0
+        for n in range(64, len(blob)):
+            i = (i + 1) % 256
+            x = (x + indices[i]) % 256
+            indices[i], indices[x] = indices[x], indices[i]
+            result += chr(blob[n] ^ indices[(indices[i] + indices[x]) % 256])
+
+        return result
 
     @staticmethod
     def _join_title(data):