base64_encode() from php function to Java does not return same data

Question

I'm working on a java project that needs to have an authentication from accounts created on a local website. Those account's passwords are encrypted by a php function before inserted to the database :

public function crypter($mdp){
    $j = 0;
    $tmp = 0;
    $key = $mdp;

    $res = "";

    for($i = 0; $i < strlen($mdp) ; $i++)
    {
        $tmp = ord($mdp[$i]) + ord($key[$i]);
        if($tmp > 255){
            $tmp = $tmp - 256;
        }

        $res[$i] = chr($tmp);

        if($j == strlen($key)-1){
            $j = 0;
        }
        else{
            $j = (($j % (strlen($key))) +1 );
        }
    }

    $res = base64_encode($res);

    return $res;
}

NOTE : This function has not been written by me, so if you guys figure out what the $j variable is used for let me know. I also (obviously) can not change this code.

So I've tried to translate that function in Java which gave this :

public String cryptMdp(String mdp){
    String res = "";
    String key = mdp;

    int j = 0;
    int tmp = 0;

    for (int i = 0; i < mdp.length(); i++) {
        char c = mdp.charAt(i);
        char c2 = key.charAt(i);

        tmp = (int) c + (int) c2;
        if (tmp > 255) {
            tmp = tmp - 256;
        }

        res += (char) tmp;

        if (j == key.length() - 1){
            j = 0;
        }
        else{
            j = (j % key.length()) + 1;
        }
    }
    return Base64.getMimeEncoder().encodeToString(res.getBytes());
}

Unfortunately, those do not return the same string (ex: For the string a, php returns wg== and Java returns w4I=.), even though according to this question this is supposed to be a standard.

Can you guys see what I'm doing wrong ?

@Penguine Already saw it, but this guy solution was the use of hmac, which I'm not using in my case — Natty
– Natty, Commented Jul 2, 2018 at 12:43
Check charset in java and php. They can be different. And another thing - java use wchar in its string. — Petya
– Petya, Commented Jul 2, 2018 at 13:16

Andreas · Accepted Answer · 2018-07-02 12:50:02Z

0

Use the existing Java functionality for Base64: https://docs.oracle.com/javase/8/docs/api/java/util/Base64.html

You are probably looking for this method:

encode(byte[] src) Encodes all bytes from the specified byte array into a newly-allocated byte array using the Base64 encoding scheme.

answered Jul 2, 2018 at 12:50

Andreas

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4 Comments

Natty Over a year ago

Sill not working :( I've tried Base64.getMimeEncoder().encode(), Base64.getMimeEncoder().encodeToString(), Base64.getEncoder().encode() and Base64.getEncoder().encodeToString() I'm getting the same result with all of them

Andreas Over a year ago

Are you 150% sure that the inputs are the same?

Andreas Over a year ago

Compare them directly and make sure there are no invisible characters anywhere.

Andreas Over a year ago

You could also try debugging both methods to see at which point exactly the outputs start deviating. That should give you a hint where to find the problem.

Natty · Accepted Answer · 2019-02-05 09:35:04Z

I've been able to do what I want using URLConnection to send a HTTP request to my PHP page, like so :

public String cryptMdp(String mdp){
    try {
        URL url = new URL("http://myaddress/someproject/create_pwd.php?pwd=" + mdp);
        URLConnection conn = url.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));

        String inputline = "";

        while((inputline = in.readLine()) != null){
            return inputline;
        }
        in.close();
    } catch (MalformedURLException ex) {
        System.out.println("error URL");
    } catch (IOException ex) {
        System.out.println("error connection");
    }
    return null;
}

The problem was that the PHP was using unknown characters before encoding them, which means that all of the passwords are incorrectly crypted...

EDIT :

Actually the password is crypted differently in the IDE (Netbeans) and in the builded app (.jar), so Base64.getMimeEncoder().encodeToString(res.getBytes()); actually produce the same as the PHP method...

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