Adhiraj Singh
63 lines
2.9 KiB
TypeScript
63 lines
2.9 KiB
TypeScript
import { Boom } from '@hapi/boom'
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import BinaryNode from "../BinaryNode"
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import { aesDecrypt, hmacSign } from "./generics"
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import { DisconnectReason, WATag } from "../Types"
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export const decodeWAMessage = (
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message: string | Buffer,
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auth: { macKey: Buffer, encKey: Buffer },
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fromMe: boolean=false
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) => {
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let commaIndex = message.indexOf(',') // all whatsapp messages have a tag and a comma, followed by the actual message
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if (commaIndex < 0) throw new Boom('invalid message', { data: message }) // if there was no comma, then this message must be not be valid
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if (message[commaIndex+1] === ',') commaIndex += 1
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let data = message.slice(commaIndex+1, message.length)
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// get the message tag.
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// If a query was done, the server will respond with the same message tag we sent the query with
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const messageTag: string = message.slice(0, commaIndex).toString()
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let json: any
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let tags: WATag
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if (data.length > 0) {
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if (typeof data === 'string') {
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json = JSON.parse(data) // parse the JSON
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} else {
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const { macKey, encKey } = auth || {}
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if (!macKey || !encKey) {
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throw new Boom('recieved encrypted buffer when auth creds unavailable', { data: message, statusCode: DisconnectReason.badSession })
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}
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/*
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If the data recieved was not a JSON, then it must be an encrypted message.
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Such a message can only be decrypted if we're connected successfully to the servers & have encryption keys
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*/
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if (fromMe) {
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tags = [data[0], data[1]]
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data = data.slice(2, data.length)
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}
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const checksum = data.slice(0, 32) // the first 32 bytes of the buffer are the HMAC sign of the message
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data = data.slice(32, data.length) // the actual message
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const computedChecksum = hmacSign(data, macKey) // compute the sign of the message we recieved using our macKey
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if (checksum.equals(computedChecksum)) {
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// the checksum the server sent, must match the one we computed for the message to be valid
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const decrypted = aesDecrypt(data, encKey) // decrypt using AES
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json = BinaryNode.from(decrypted) // decode the binary message into a JSON array
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} else {
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throw new Boom('Bad checksum', {
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data: {
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received: checksum.toString('hex'),
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computed: computedChecksum.toString('hex'),
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data: data.slice(0, 80).toString(),
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tag: messageTag,
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message: message.slice(0, 80).toString()
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},
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statusCode: DisconnectReason.badSession
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})
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}
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}
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}
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return [messageTag, json, tags] as const
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} |