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Date: Wed, 30 Apr 2008 02:18:55 -0700 (PDT)
From: "Robert Rodewald (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Updated: (CODEC-68) isBase64 throws
 ArrayIndexOutOfBoundsException on some non-BASE64 bytes
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     [ https://issues.apache.org/jira/browse/CODEC-68?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Rodewald updated CODEC-68:
---------------------------------

    Description: 
the following code throws an ArrayIndexOutOfBoundsException although it is perfectly valid (the byte 0x9c should be ignored according to the standard):

{code}
byte[x] = new byte[] { 'n', 'A', '=', '=', 0x9c };
Base64.decodeBase64(x);
{code}

The problem is the following method:

{code}
    private static boolean isBase64(byte octect) {
        if (octect == PAD) {
            return true;
        } else if (base64Alphabet[octect] == -1) {
            return false;
        } else {
            return true;
        }
    }
{code}

in Java octect is a *signed* value, so it is not correct to use it as an offset for an array [0..254] which base64Alphabet is. 0x9c is -100!

FIX:
use base64Alphabet[ 0xff & octect ] in the "else if" block to convert the octet prior using it as an offset for the lookup table

  was:
the following code throws an ArrayIndexOutOfBoundsException although it is perfectly valid (the byte 0x9c should be ignored according to the standard):

<code>
byte[x] = new byte[] { 'n', 'A', '=', '=', 0x9c };
Base64.decodeBase64(x);
</code>

The problem is the following method:

    private static boolean isBase64(byte octect) {
        if (octect == PAD) {
            return true;
        } else if (base64Alphabet[octect] == -1) {
            return false;
        } else {
            return true;
        }
    }

in Java octect is a *signed* value, so it is not correct to use it as an offset for an array [0..254] which base64Alphabet is. 0x9c is -100!

FIX:
use base64Alphabet[ 0xff & octect ] in the "else if" block to convert the octet prior using it as an offset for the lookup table


> isBase64 throws ArrayIndexOutOfBoundsException on some non-BASE64 bytes
> -----------------------------------------------------------------------
>
>                 Key: CODEC-68
>                 URL: https://issues.apache.org/jira/browse/CODEC-68
>             Project: Commons Codec
>          Issue Type: Bug
>    Affects Versions: 1.3
>            Reporter: Robert Rodewald
>   Original Estimate: 0.25h
>  Remaining Estimate: 0.25h
>
> the following code throws an ArrayIndexOutOfBoundsException although it is perfectly valid (the byte 0x9c should be ignored according to the standard):
> {code}
> byte[x] = new byte[] { 'n', 'A', '=', '=', 0x9c };
> Base64.decodeBase64(x);
> {code}
> The problem is the following method:
> {code}
>     private static boolean isBase64(byte octect) {
>         if (octect == PAD) {
>             return true;
>         } else if (base64Alphabet[octect] == -1) {
>             return false;
>         } else {
>             return true;
>         }
>     }
> {code}
> in Java octect is a *signed* value, so it is not correct to use it as an offset for an array [0..254] which base64Alphabet is. 0x9c is -100!
> FIX:
> use base64Alphabet[ 0xff & octect ] in the "else if" block to convert the octet prior using it as an offset for the lookup table

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