send/frontend/src/fileSender.js

const EventEmitter = require('events');
const { ivToStr } = require('./utils');

class FileSender extends EventEmitter {
  constructor(file) {
    super();
    this.file = file;
    this.iv = window.crypto.getRandomValues(new Uint8Array(16));
  }

  static delete(fileId, token) {
    return new Promise((resolve, reject) => {
      if (!fileId || !token) {
        return resolve();
      }
      let xhr = new XMLHttpRequest();
      xhr.open('post', '/delete/' + fileId, true);
      xhr.setRequestHeader('Content-Type', 'application/json');

      xhr.onreadystatechange = () => {
        if (xhr.readyState === XMLHttpRequest.DONE) {
          resolve();
        }

        if (xhr.status === 200) {
          console.log('The file was successfully deleted.');
        } else {
          console.log('The file has expired, or has already been deleted.');
        }
      };

      xhr.send(JSON.stringify({ delete_token: token }));
    });
  }

  upload() {
    return Promise.all([
      window.crypto.subtle.generateKey(
        {
          name: 'AES-CBC',
          length: 128
        },
        true,
        ['encrypt', 'decrypt']
      ),
      new Promise((resolve, reject) => {
        const reader = new FileReader();
        reader.readAsArrayBuffer(this.file);
        reader.onload = function(event) {
          resolve(new Uint8Array(this.result));
        };
      })
    ])
      .then(([secretKey, plaintext]) => {
        return Promise.all([
          window.crypto.subtle.encrypt(
            {
              name: 'AES-CBC',
              iv: this.iv
            },
            secretKey,
            plaintext
          ),
          window.crypto.subtle.exportKey('jwk', secretKey)
        ]);
      })
      .then(([encrypted, keydata]) => {
        return new Promise((resolve, reject) => {
          let file = this.file;
          let fileId = ivToStr(this.iv);
          let dataView = new DataView(encrypted);
          let blob = new Blob([dataView], { type: file.type });
          let fd = new FormData();
          fd.append('fname', file.name);
          fd.append('data', blob, file.name);

          let xhr = new XMLHttpRequest();

          xhr.upload.addEventListener('progress', e => {
            if (e.lengthComputable) {
              let percentComplete = Math.floor(e.loaded / e.total * 100);
              this.emit('progress', percentComplete);
            }
          });

          xhr.onreadystatechange = () => {
            if (xhr.readyState == XMLHttpRequest.DONE) {
              // uuid field and url field
              let responseObj = JSON.parse(xhr.responseText);
              resolve({
                url: responseObj.url,
                fileId: fileId,
                secretKey: keydata.k,
                deleteToken: responseObj.uuid
              });
            }
          };

          xhr.open('post', '/upload/' + fileId, true);
          xhr.send(fd);
        });
      });
  }
}

module.exports = FileSender;