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Brute force media decoding

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This commit is contained in:
Adhiraj
2020-07-11 13:33:22 +05:30
parent 142a92cc49
commit 44bd50cf4d
1 changed files with 31 additions and 22 deletions
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53
src/WAClient/Utils.ts
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@@ -112,32 +112,41 @@ export async function decodeMediaMessage(message: WAMessageContent, filename: st
| proto.ImageMessage | proto.ImageMessage
| proto.AudioMessage | proto.AudioMessage
| proto.DocumentMessage | proto.DocumentMessage
// get the keys to decrypt the message
const mediaKeys = getMediaKeys(messageContent.mediaKey, type) //getMediaKeys(Buffer.from(messageContent.mediaKey, 'base64'), type)
const iv = mediaKeys.iv
const cipherKey = mediaKeys.cipherKey
const macKey = mediaKeys.macKey
// download the message // download the message
const fetched = await fetch(messageContent.url, {}) const fetched = await fetch(messageContent.url, {})
const buffer = await fetched.buffer() const buffer = await fetched.buffer()
// first part is actual file
const file = buffer.slice(0, buffer.length - 10)
// last 10 bytes is HMAC sign of file
const mac = buffer.slice(buffer.length - 10, buffer.length)
// sign IV+file & check for match with mac const decryptedMedia = (type: MessageType) => {
const testBuff = Buffer.concat([iv, file]) // get the keys to decrypt the message
const sign = hmacSign(testBuff, macKey).slice(0, 10) const mediaKeys = getMediaKeys(messageContent.mediaKey, type) //getMediaKeys(Buffer.from(messageContent.mediaKey, 'base64'), type)
// our sign should equal the mac // first part is actual file
if (sign.equals(mac)) { const file = buffer.slice(0, buffer.length - 10)
const decrypted = aesDecryptWithIV(file, cipherKey, iv) // decrypt media // last 10 bytes is HMAC sign of file
const mac = buffer.slice(buffer.length - 10, buffer.length)
const trueFileName = attachExtension ? (filename + '.' + getExtension(messageContent.mimetype)) : filename // sign IV+file & check for match with mac
fs.writeFileSync(trueFileName, decrypted) const testBuff = Buffer.concat([mediaKeys.iv, file])
const sign = hmacSign(testBuff, mediaKeys.macKey).slice(0, 10)
return trueFileName // our sign should equal the mac
} else { if (sign.equals(mac)) {
throw new Error('HMAC sign does not match') return aesDecryptWithIV(file, mediaKeys.cipherKey, mediaKeys.iv) // decrypt media
} else {
throw new Error('HMAC sign does not match')
}
} }
const allTypes = [type, ...Object.keys(HKDFInfoKeys)]
for (let i = 0; i < allTypes.length;i++) {
try {
const decrypted = decryptedMedia (allTypes[i] as MessageType)
if (i > 0) { console.log (`decryption of ${type} media with HKDF key of ${allTypes[i]}`) }
const trueFileName = attachExtension ? (filename + '.' + getExtension(messageContent.mimetype)) : filename
fs.writeFileSync(trueFileName, decrypted)
return trueFileName
} catch {
if (i === 0) { console.log (`decryption of ${type} media with original HKDF key failed`) }
}
}
throw new Error('HMAC sign does not match')
} }