Initial commit

WhatsAppWeb.Utils.js

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+const Crypto = require("crypto")
+
+/* 
+    Basic cryptographic utilities to interact with WhatsApp servers
+*/
+module.exports = {
+    // decrypt AES 256 CBC; where the IV is prefixed to the buffer
+    aesDecrypt: function (buffer, key) {
+        const aes = Crypto.createDecipheriv('aes-256-cbc', key, buffer.slice(0,16) ) // first 16 bytes of buffer is IV
+        return Buffer.concat( [ aes.update(buffer.slice(16, buffer.length)), aes.final() ] )
+    },
+    // encrypt AES 256 CBC; where the IV is prefixed to the buffer
+    aesEncrypt: function (buffer, key) {
+        const IV = this.randomBytes(16)
+        const aes = Crypto.createCipheriv('aes-256-cbc', key, IV)
+        return Buffer.concat( [ IV, aes.update(buffer), aes.final() ] ) // prefix IV to the buffer
+    },
+    // sign HMAC using SHA 256
+    hmacSign: function (buffer, key) {
+        return Crypto.createHmac('sha256', key).update(buffer).digest()
+    },
+    // generate a buffer with random bytes of the specified length
+    randomBytes: function (length) { return Crypto.randomBytes(length) },
+
+    // whatsapp requires a message tag for every message, we just use the timestamp as one
+    generateMessageTag: function () { return new Date().getTime().toString() },
+    // generate a random 16 byte client ID
+    generateClientID: function () { return this.randomBytes(16).toString('base64') },
+    // generate a random 10 byte ID to attach to a message
+	generateMessageID: function () { return this.randomBytes(10).toString('hex').toUpperCase() }
+}