feat: added a decrypt and save function

src/api/helpers/decrypt.ts

@@ -17,11 +17,15 @@
 
 import * as crypto from 'crypto';
 import hkdf from 'futoin-hkdf';
-import atob = require('atob');
+import atob from 'atob';
 import { ResponseType } from 'axios';
+import { Transform } from 'stream';
 
-export const makeOptions = (useragentOverride: string) => ({
-  responseType: 'arraybuffer' as ResponseType,
+export const makeOptions = (
+  useragentOverride: string,
+  responseType: ResponseType = 'arraybuffer'
+) => ({
+  responseType: responseType,
   headers: {
     'User-Agent': processUA(useragentOverride),
     DNT: '1',
@@ -110,3 +114,55 @@ const base64ToBytes = (base64Str: any) => {
   }
   return byteArray;
 };
+
+export const newMagix = (
+  mediaKeyBase64: string,
+  mediaType: string,
+  expectedSize: number
+) => {
+  const mediaKeyBytes = newBase64ToBytes(mediaKeyBase64);
+  const info = `WhatsApp ${mediaTypes[mediaType.toUpperCase()]} Keys`;
+  const hash = 'sha256';
+  const salt = Buffer.alloc(32);
+  const expandedSize = 112;
+  const mediaKeyExpanded = hkdf(mediaKeyBytes, expandedSize, {
+    salt,
+    info,
+    hash,
+  });
+  const iv = mediaKeyExpanded.slice(0, 16);
+  const cipherKey = mediaKeyExpanded.slice(16, 48);
+
+  const decipher = crypto.createDecipheriv('aes-256-cbc', cipherKey, iv);
+  let processedBytes: number = 0;
+  let buffer = Buffer.alloc(0);
+
+  const transformStream = new Transform({
+    transform(chunk, encoding, callback) {
+      try {
+        const decryptedChunk = decipher.update(chunk);
+        processedBytes += decryptedChunk.length;
+        if (processedBytes > expectedSize) {
+          const paddedChunk = Buffer.from(decryptedChunk).slice(
+            0,
+            buffer.length - (processedBytes - expectedSize)
+          );
+          callback(null, paddedChunk);
+        } else {
+          callback(null, decryptedChunk);
+        }
+      } catch (error: any) {
+        callback(error);
+      }
+    },
+  });
+
+  transformStream.on('error', (error) => {
+    console.error('Error during decryption:', error);
+  });
+
+  return transformStream;
+};
+
+const newBase64ToBytes = (base64Str: string) =>
+  Buffer.from(base64Str, 'base64');

src/api/whatsapp.ts

@@ -20,10 +20,11 @@ import { Page } from 'puppeteer';
 import { CreateConfig } from '../config/create-config';
 import { useragentOverride } from '../config/WAuserAgente';
 import { evaluateAndReturn } from './helpers';
-import { magix, makeOptions, timeout } from './helpers/decrypt';
+import { magix, makeOptions, newMagix, timeout } from './helpers/decrypt';
 import { BusinessLayer } from './layers/business.layer';
 import { GetMessagesParam, Message } from './model';
-import treekill = require('tree-kill');
+import * as fs from 'fs';
+import { sleep } from '../utils/sleep';
 
 export class Whatsapp extends BusinessLayer {
   private connected: boolean | null = null;
@@ -39,7 +40,7 @@ export class Whatsapp extends BusinessLayer {
       });
     }
 
-    interval = setInterval(async (state) => {
+    interval = setInterval(async () => {
       const newConnected = await page
         .evaluate(() => WPP.conn.isRegistered())
         .catch(() => null);
@@ -232,6 +233,104 @@ export class Whatsapp extends BusinessLayer {
     return magix(buff, message.mediaKey, message.type, message.size);
   }
 
+  public async decryptAndSaveFile(
+    message: Message,
+    savePath: string
+  ): Promise<void> {
+    const mediaUrl = message.clientUrl || message.deprecatedMms3Url;
+
+    if (!mediaUrl) {
+      throw new Error(
+        'Message is missing critical data needed to download the file.'
+      );
+    }
+
+    try {
+      const tempSavePath: string = savePath + '.encrypted';
+      await this.downloadEncryptedFile(mediaUrl.trim(), tempSavePath);
+
+      const inputReadStream = fs.createReadStream(tempSavePath);
+      const outputWriteStream = fs.createWriteStream(savePath);
+      const decryptedStream = newMagix(
+        message.mediaKey,
+        message.type,
+        message.size
+      );
+
+      inputReadStream.pipe(decryptedStream).pipe(outputWriteStream);
+
+      await new Promise<void>((resolve, reject) => {
+        outputWriteStream.on('finish', () => {
+          console.log(
+            `Deciphering complete. Deleting the encrypted file: ${tempSavePath}`
+          );
+          fs.unlink(tempSavePath, (error) => {
+            if (error) {
+              console.error(
+                `Error deleting the input file: ${tempSavePath}`,
+                error
+              );
+              reject(error);
+            } else {
+              console.log('Encrypted file deleted successfully');
+              resolve();
+            }
+          });
+        });
+
+        outputWriteStream.on('error', (error) => {
+          console.error(`Error during writing file: ${savePath}`, error);
+          reject(error);
+        });
+
+        decryptedStream.on('error', (error) => {
+          console.error('An error occurred while decrypting the file', error);
+          reject(error);
+        });
+      });
+    } catch (error) {
+      throw error;
+    }
+  }
+
+  downloadEncryptedFile = async (
+    url: string,
+    outputPath: string,
+    retries: number = 3
+  ) => {
+    for (let attempt = 1; attempt <= retries; attempt++) {
+      try {
+        const response = await axios.get(
+          url,
+          makeOptions(useragentOverride, 'stream')
+        );
+
+        await new Promise((resolve, reject) => {
+          const writer = fs.createWriteStream(outputPath);
+          response.data.pipe(writer);
+          writer.on('finish', resolve);
+          writer.on('error', reject);
+        });
+
+        console.log(`Encrypted file downloaded at ${outputPath}`);
+        return;
+      } catch (error) {
+        console.error(`Attempt ${attempt} failed: `, error.message);
+        if (attempt === retries) {
+          console.error(
+            `${outputPath} - All attempt failed to download the file: ${url}`
+          );
+          throw error;
+        }
+
+        console.log(
+          `${outputPath} - Retrying to download the file: ${url} in 5 seconds...`
+        );
+        await sleep(5000);
+      }
+    }
+  };
+
   /**
    * Rejects a call received via WhatsApp
    * @param callId string Call ID, if not passed, all calls will be rejected