From 67dae1bececa8b96ff71261813acab0e3cbbdbfb Mon Sep 17 00:00:00 2001
From: cheetah <git@cheetah.cat>
Date: Thu, 13 Apr 2023 18:58:25 +0200
Subject: [PATCH] added decrypt

---
 decrypter.js |  9 +++++++++
 index.js     | 26 ++++++++++++++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 decrypter.js

diff --git a/decrypter.js b/decrypter.js
new file mode 100644
index 0000000..e5ec714
--- /dev/null
+++ b/decrypter.js
@@ -0,0 +1,9 @@
+//  npm install --save yargs
+
+const BOSkrypt = require('.');
+
+var argv = require('yargs/yargs')(process.argv)
+    .string(['key', 'message'])
+    .argv
+;
+console.log(BOSkrypt.decrypt(argv.message, argv.key))
diff --git a/index.js b/index.js
index d98dfcc..0cdbf9a 100644
--- a/index.js
+++ b/index.js
@@ -1,7 +1,6 @@
 const aesjs = require('./aes-64bit')
 const crc = require('node-crc')
 const crypto = require("crypto")
-//console.log(crypto.getCiphers())
 function randomIntInc(low, high) {
   return Math.floor(Math.random() * (high - low + 1) + low)
 }
@@ -39,6 +38,7 @@ class BOSkrypt {
         .substring(0, 7) //take first 7 chars
     }).join('') //join to one complete string
 
+    console.log('compressedPreparedPayload', compressedPreparedPayload)
     let compressedPayload = []
     for (let i=0;i<compressedPreparedPayload.length;i+=8) {
       let byte = parseInt(
@@ -51,7 +51,8 @@ class BOSkrypt {
       compressedPayload.push( byte ) //put in array
     }
     compressedPayload = Buffer.from(compressedPayload)
-
+    console.log('compressedPayload', compressedPayload)
+    console.log('uncPayloadHash', uncPayloadHash.length, uncPayloadHash)
     const toEncryptData = Buffer.concat([
       uncPayloadHash, compressedPayload
     ])
@@ -59,7 +60,28 @@ class BOSkrypt {
     const encrpytedIncludingIVandSHA1Checksum = Buffer.concat([
       ivWithTimestamp, encryptedPayload
     ])
+    console.log('ivWithTimestamp', ivWithTimestamp)
     return encrpytedIncludingIVandSHA1Checksum.toString('base64')
   }
+  decrypt(encrpytedIncludingIVandSHA1Checksum, key) {
+    key = Buffer.from(key, 'hex')
+    const ivPadBuffer = Buffer.from("00".repeat(8), 'hex')
+    let encrpytedIncludingIVandSHA1ChecksumArray = Buffer.from(encrpytedIncludingIVandSHA1Checksum, 'base64')
+    let ivWithTimestamp = encrpytedIncludingIVandSHA1ChecksumArray.slice(0, 8)
+    const ivWithTimestampPadded = Buffer.concat([ ivWithTimestamp, ivPadBuffer ])
+    let encryptedBuffer = encrpytedIncludingIVandSHA1ChecksumArray.slice(8)
+    let encryptedPayload = new aesjs.ModeOfOperation.ctr(key, new aesjs.Counter(ivWithTimestampPadded)).decrypt(encryptedBuffer)
+    let compressedPayload = Buffer.from(encryptedPayload).slice(5)
+    let uncompressed = ""
+    {
+      let b8s = ""
+      for (let b8 of compressedPayload) b8s += b8.toString(2).padStart(8, '0').split('').reverse().join('')
+      for (let i = 0; i < b8s.length; i += 7) uncompressed += String.fromCharCode(parseInt(b8s.substring(i, i + 7).split('').reverse().join(''), 2))
+    }
+    return {
+      keyIndex: ivWithTimestampPadded[4],
+      uncompressed
+    }
+  }
 }
 module.exports = new BOSkrypt()
\ No newline at end of file