Decoding and Encoding issue. Different implementations of Base64 Class in android.util.* and java.util.*?

Question

I am writing an App which does the following with a given String str:

encode(encrypt(encode(stringToBytearray(str))));

The Server receives the Base64 encoded String, which is then decoded -> decrypted -> decoded, to get the sent String str from the App.

Unfortunately it doesnt work for all Strings, long Strings lead to a long Base64 String and my Server throws the following Exception:

Exception in thread "main" java.lang.IllegalArgumentException: Illegal base64 character 5b
 at java.util.Base64$Decoder.decode0(Base64.java:714)
 at java.util.Base64$Decoder.decode(Base64.java:526)
 at Main.decode(Main.java:113)
 at Main.main(ain.java:33)

The String has the format "[string, string, ..., string]" without "s.

Like I mentioned above, for Strings which are not too long (sorry I cant quantify the length yet), this works. So I think I implemented it right.

Whats weird is, that if I dont send it, but decode(decrypt(decode(stringToBytearray(str)))); the String on the Device itself, it all works perfectly.

My Setup: JDK 7, eclipse (adt-bundle, android development) (Windows 7)

JDK 8, eclipse ('normal' java) (Linux (xubuntu))

Is it because both Classes (Base64) are implemented diffrently? If so, how can I make it work?

Here are the Encoding/Decoding Methods:

Encoding (Device: on Windows 7, adt-bundle, Android-Dev, jdk 7):

import android.util.Base64

public byte[] encode(byte[] bytearrayToEncode){
   return Base64.encode(bytearrayToEncode, Base64.NO_WRAP|Base64.URL_SAFE);
}

Decoding (Server: on Linux, jdk 8):

import java.util.Base64

public byte[] decode(byte[] bytearrayToEncode){
   return Base64.getUrlDecoder().decode(bytearrayToDecode);
}

Strings are all De-/Encoded with the same charset (utf-8)! Encoding/Decoding: Base64

Crypto: AES

If you need more Information, just ask, but I think I provided all neccessary informations.

Edit:

public String bytearrayToString(byte[] bytearray){
    String str = null;
    try {
        str = new String(bytearray, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return str;
}

public byte[] stringToBytearray(String str){
    byte[] bytearray = null;
    try {
        bytearray = str.getBytes("UTF-8");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return bytearray;
}

0x5b is [, and as I said the String format is [string, ..., string]. But why does all encoding/decoding work on the Device, but not on the Server, when the String is too long. (i compared both long strings, and they are equal) — user3469811
– user3469811, Commented Mar 27, 2014 at 18:41
Is your server trimming the query param when length is too large? Just try to echo the received base-64 message and check if they are exactly equal. Because truncated string may no longer be a valid Base-64 encrypted message. — D3V
– D3V, Commented Mar 27, 2014 at 19:12
I just found out, that the second call of encode, does not apply (even though i thought i have checked it). So far, thanks for all suggestions! I will try to figure out why it doesnt. — user3469811
– user3469811, Commented Mar 27, 2014 at 20:49
I have struggled a bit with the different encoders in java.util.Base64. Have you tried Base64.getDecoder() instead of Base64.getUrlDecoder()? — Johannes Brodwall
– Johannes Brodwall, Commented Apr 17, 2017 at 12:11

Mohsin Ali · Accepted Answer · 2015-09-01 19:41:36Z

11

You must be using JSONObjects to send the Base64 String to the server. If so then the JSONObject will add " \ " escape characters to the string which are illegal Base64 characters. All you need to do is

String rectifiedString = Base64String.replace("\\","");

on the server end before using the acquired string.

Optional

Also on the server side use

import javax.xml.bind.DatatypeConverter;

and

String result = DatatypeConverter.printBase64Binary(bytearrayToDecode);

byte[] result = DatatypeConverter.parseBase64Binary(str);

instead.

It will not only get the job done but is much faster at encoding/decoding (as benchmarked here).

edited Sep 1, 2015 at 19:41

answered Aug 31, 2015 at 20:39

Mohsin Ali

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1 Comment

cloudsurfin Over a year ago

Looks to me like printBase64Binary strips the backslash for you. Thanks for the insight. I had the same issue as OP.

Anand Varkey Philips · Accepted Answer · 2017-08-10 13:57:29Z

1

If you have a space in your encoded string, which is an illegal character in base64. If you remove it, it still generates the same image/data in the converter you linked to, and can be now decoded by your code as well.

UPDATE: Some decoders (like the one you linked, or Base64.getMimeDecoder() in Java) ignore illegal characters, others (like Base64.getDecoder()) don't allow them.

answered Aug 10, 2017 at 13:57

Anand Varkey Philips

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Comments

General Failure · Accepted Answer · 2017-09-19 05:00:28Z

0

Use for encode:

Base64.getEncoder().encodeToString(yourString.getBytes("UTF-8"));

and decode:

byte[] decodedBytes = Base64.getDecoder().decode(yourString);
String stringDecode = new String(decodedBytes, "UTF-8");

edited Sep 19, 2017 at 5:00

General Failure

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answered Sep 19, 2017 at 4:18

Leonardo Borges

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