decryptFile method

Future<void> decryptFile(String filePath, String fileName)

Decrypt a file content The function takes ciphertext in an encrypted file, decrypt them using the key, and store the plaintext in the same file

Implementation

Future<void> decryptFile(String filePath, String fileName) async {
  /// Encrypted file URL
  //String encFileUrl = webId.replaceAll('profile/card#me', filePath + '/' + fileName);

  /// Get ciphertext file content
  String encFilePath = filePath + '/' + fileName;
  String fileContent = await fetchFile(encFilePath);
  EncProfile encFile = EncProfile(fileContent.toString());
  String encFileCont = encFile.getEncFileCont();
  String encIvVal = encFile.getEncIvVal();

  /// Get encryption key that is stored in the local storage
  String encKey = appStorage.getItem('encKey');

  /// Decrypt the ciphertext
  String plainFileCont = decryptVal(encKey, encFileCont, encIvVal);

  /// Get the list of locations of files that are encrypted
  var keyInfo = await fetchFile(encKeyFileLoc);
  EncProfile keyFile = EncProfile(keyInfo.toString());
  String encFileHash = keyFile.getEncFileHash();
  String encFileIvVal = keyFile.getEncIvVal();
  String encFilePlaintext = decryptVal(encKey, encFileHash, encFileIvVal);
  List encFileList = jsonDecode(encFilePlaintext);

  /// Delete the encrypted file
  String delResponse = await deleteItem(true, encFilePath);

  /// Create new file with plaintext content
  String fileCreateRes =
      await createItem(true, fileName, plainFileCont, fileLoc: filePath);

  /// Update the list of encrypted files
  encFileList.remove(encFilePath);
  String newFileListStr = jsonEncode(encFileList);

  String encKeyFileUrl = webId.replaceAll('profile/card#me', encKeyFileLoc);
  List fileListEncRes = encryptVal(encKey, newFileListStr);
  String fileListStrEnc = fileListEncRes[0];
  String fileListIv = fileListEncRes[1];

  // Update encrypted value
  String dPopToken =
      genDpopToken(encKeyFileUrl, rsaKeyPair, publicKeyJwk, 'PATCH');
  String updateQuery = genSparqlQuery(
      'UPDATE', '', encFilePred, fileListStrEnc,
      prevObject: encFileHash);

  String updateResponse =
      await runQuery(encKeyFileUrl, dPopToken, updateQuery);

  // Update IV value
  String dPopTokenIv =
      genDpopToken(encKeyFileUrl, rsaKeyPair, publicKeyJwk, 'PATCH');
  String updateQueryIv = genSparqlQuery('UPDATE', '', ivValPred, fileListIv,
      prevObject: encFileIvVal);

  String updateResponseIv =
      await runQuery(encKeyFileUrl, dPopTokenIv, updateQueryIv);

  if (delResponse != 'ok' ||
      fileCreateRes != 'ok' ||
      updateResponse != 'ok' ||
      updateResponseIv != 'ok') {
    throw Exception('Failed to revoke encrypted file $encFilePath.');
  }
}