使用utf8格式的值在json中传输加密数据

Question

I'm trying to stringify output from openssl_public_encrypt and other openssl functions i php, and the output don't seem to be utf8 encoded. Here is a sample code that generate the error that is my problem in a nutshell.

<?php
  $pubkey=<<<EOD
  -----BEGIN PUBLIC KEY-----
  MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAueWffJhr4j+PZhf4QlFF
  1HEmcu9d93YYBIQdZBZLWx4uqxsZ6Q3FaBVMkHh0h+sDHx1je2fQprTEMjWGSIu0
  HlXRZqPLkVUCpQg2j1oQk2BbZExS6kyziVa1G9ai094WqMz3MjyimOvJxuCAsb+i
  rQ/HaC2+vBAdm8wjLYEkqe/q7Q6Tnf+U6bpPYASXTz0WlLJj/G2LLTpEYzF3IgTB
  tRsTI6hwpmpHzpKUucEvliEesEPMAs3xp4AaKBdqKQoGFsiA2p1jxJIRUXC/ur7f
  2ZgWI59AtemVd+FRZfUapfe5uDD3M5cJy/6Uh9Yg+7vMzuCzi/yBDDFwyy4hD2RJ
  YwIDAQAB
  -----END PUBLIC KEY-----
  EOD;
  $jsontest= new \stdClass();
  $data="Testing some text ÆØåæøåéè";
  openssl_public_encrypt($data,$encrypted,$pubkey,OPENSSL_PKCS1_OAEP_PADDING);
  //Next line outputs encoding UTF8 sometimes but not consequently
  echo "

data1: ".mb_detect_encoding($encrypted)."
";
  $jsontest->data1=$encrypted;
  $data="Testing some other text ÆØåæøåéè";
  openssl_public_encrypt($data,$encrypted,$pubkey,OPENSSL_PKCS1_OAEP_PADDING);
  //Next line outputs encoding UTF8 sometimes but not consequently
  echo "

data1: ".mb_detect_encoding($encrypted)."
";
  $jsontest->data2=$encrypted;
  header('Content-Type: application/json; charset=UTF-8');
  //print_r($jsontest);
  $json=null;
  try {
      $json = json_encode($jsontest, JSON_THROW_ON_ERROR);
  } catch (JsonException $e) {
      echo 'Error:'.$e;
  }
  if($json)echo "JSON output:
$json";
?>

Expected output would be a stringified json object with utf8 encoded property values. Instead i get this error message:

"Error:JsonException: Malformed UTF-8 characters, possibly incorrectly encoded in 'the php file':24"

When i run the above code snippet, the 'mb_detect_encoding' lines output 'UTF-8' sometimes, but not always.

There seems to be a problem in openssl_public_encrypt, where the output is not conform to utf-8 encoding.

A very strange behavior detected: Probably mb_detect_encoding does not detect correct, because the json_encode function fails every time. and probably openssl_public_encrypt is to blame for this behavior.

Anyways i can't stringify the supposedly UTF-8 encoded output from openssl_public_encrypt. I use base64 encoding of encrypted data for now as a solution, but the data overhead is around the double of original data.

I use openssl in php to encrypt/decrypt with rsa, ecdh and aes, in conjuction with javascript webCrypto.

Can anybody help me solve this problem, as i am probably not the only one who has this problem.

Edit:

Got it wrong! The function json_encode in php is the showstopper! It doesn't accept UTF-8 encoded json strings although json is specified for UTF-8 to my knowledge. It certainly is accepted by and retrieved ok in file_get_contents("php://input"). Is there any reason for that?

Answer 1

"Malformed UTF-8 characters" means the input data contains invalid characters.

If the data is hard coded, save your file with UTF-8 (no BOM) encode.

If not, use iconv to convert or check the input data.

Encrypted data is in binary format, you may need do base64 encode before run json encode

$jsontest->data1 = base64_encode($encrypted);