decrypt-wave.js

(function() {
  let alg = {name: "AES-GCM", length: 256}
  let keyUsages = ["encrypt", "decrypt"]

  function base64ToBuffer(base64) {
    let binary_string =  window.atob(base64)
    let len = binary_string.length
    let bytes = new Uint8Array(len)
    for (var i = 0; i < len; i++) {
      bytes[i] = binary_string.charCodeAt(i)
    }
    return bytes.buffer
  }

  let getCryptoKey = (key) => {
    let keydata = {
        kty: "oct",
        k: key,
        alg: "A256GCM",
        ext: true,
    };
    return window.crypto.subtle.importKey("jwk", keydata, alg, false, keyUsages)
  }

  let decrypt = (key, msg) => {
    msg = msg.split(";")
    let iv = base64ToBuffer(msg[0])
    let data = base64ToBuffer(msg[1])
    let additionalData = base64ToBuffer(msg[2])
    let params = {
      name: "AES-GCM",
      iv,
      additionalData,
    }
    return window.crypto.subtle.decrypt(params, key, data).then(buffer => {
      return new TextDecoder("utf8").decode(buffer)
    })
  }

  let onServerResponse = (json) => {
    console.log(json)
    let texts = {}
    getCryptoKey(key).then(k => {
      key = k;
      let snapshot = json.snapshots[Object.keys(json.snapshots)[0]]

      Promise.all(Object.keys(snapshot.ciphertexts).map((c) => {
        return decrypt(key, snapshot.ciphertexts[c]).then(t => texts[c] = t)
      })).then(() => {
        console.log(texts)
        let content = ""
        let pieces = snapshot.pieces
        console.log(pieces)
        for (let k of Object.keys(pieces)) {
          console.log(JSON.stringify(pieces[k]))
          console.log(texts[pieces[k].opId].substring(pieces[k].offset, pieces[k].offset+pieces[k].len))
          content += texts[pieces[k].opId].substring(pieces[k].offset, pieces[k].offset+pieces[k].len)
        }
        let i = 0
        document.querySelector('.document').innerHTML = document.querySelector('.document').innerHTML.split('').map(c => {
          if (c == '*') {
            return content.charAt(i++)
          } else {
            return c
          }
        }).join('')
      })
    })
  }

  let waveId = location.hash.substr(1).split('!')[0]
  let key = location.hash.substr(1).split('!')[1];
  let r = new XMLHttpRequest()
  r.open("GET", "/crypto/snapshot/" + waveId + "/local.net/conv+root", true)
  r.onreadystatechange = function () {
    if (r.readyState != 4 || r.status != 200) return
    onServerResponse(JSON.parse(r.responseText))
  }
  r.send()
})()