I am trying to decode a Base64 format Token after retrieving it from Object store in Anypoint Studio. Help resolve the dataweave error?

Question

I am trying to decode a BASE 64 format token after getting it from object store but getting error in transform message.

Output after Object Store Retrieval. This needs to be decoded.

eyJhbGciOiJodHRwOi8vd3d3LnczLm9yZy8yMDAxLzA0L3htbGRzaWctbW9yZSNobWFjLXNoYTI1NiIsInR5cCI6IkpXVCJ9.eyJVc2VySUQiOiIxNzMzIiwiVXNlck5hbWUiOiJhY2hhbjAzMiIsIkN1bHR1cmVUYWciOm51bGwsImlhdCI6IjE1Njc2Njk3MDgiLCJleHAiOiIxNTY3NzU2MTA4IiwiaXNzIjoiVGltZVNoYXJlV2FyZSIsImF1ZCI6Imh0dHBzOi8vVGltZVNoYXJlV2FyZS5jb20vIn0.w2h6j7gbAs6CouE9WoYEDQRzBYEsNIqry70w2K4JAZg

    %dw 2.0
    import * from dw::core::Binaries
    output application/octet-stream
    ---
    fromBase64(payload as String) as Binary

ERROR MESSAGE:

    Message               : "Illegal base64 character 2e

    5| fromBase64(payload as String) as Binary
                  ^^^^^^^^^^^^^^^^^
    Trace:
      at fromBase64 (line: 5, column: 12)
      at main (line: 5, column: 1)" evaluating expression: "%dw 2.0
    import * from dw::core::Binaries
    output application/octet-stream
    ---
    fromBase64(payload as String) as Binary".
    Error type            : MULE:EXPRESSION
    Element               : authenticationflowtswFlow/processors/3 @ authenticationflowtsw:authenticationflowtsw.xml:30 (Transform Message)
    Element XML           : <ee:transform doc:name="Transform Message" doc:id="0cf3e737-e6a1-4d67-9a7c-60017db4ccf9">
    <ee:message>
    <ee:set-payload>%dw 2.0
    import * from dw::core::Binaries
    output application/octet-stream
    ---
    fromBase64(payload as String) as Binary</ee:set-payload>
    </ee:message>
    </ee:transform>

I expect to get something like-

{
"alg":"http://www.w3.org/2001/04/xmldsig-more#hmac-sha256",
"typ":"JWT"}{"UserID":"1733",
"UserName":"achan032",
"CultureTag":null,
"iat":"1567669708",
"exp":"1567756108",
"iss":"TimeShareWare",
"aud":"https://TimeShareWare.com/"}0OVA`K
    "L6+@f

It looks like your encoder is the problem or it is rejecting a character that you are passing in. How are you encoding your payload? Are you using the Dataweave 2.0's function for encoding (toBase64)? Also, your expected output is not well formed JSON. Is that really your expected output? — granthbr

Jason Gray Jason Gray · Accepted Answer · 2020-01-11T03:18:38

Web Tokens use Base64Url instead of the typical Base64. They are basically the same except Base64Url are safe to pass in a URL because they use – instead of + and _ instead of / and they omit the = padding characters at the end of the string. You can do string replacement to properly convert the token then call fromBase64.

The 2e in the error message is a period "." which is not a Base64 standard character. This is because the token is a JWT and is structured like [Header].[Payload].[Signature] and each part individually Base64Url encoded. If you want to get the payload where all the claims are you will need to split the string/token by the period ".".

On the flip side if you defined a custom function called Base64Url, since no such function currently exists in Mule 4/Dataweave 2, you could build a JWT like the following: Base64Url(header) + "." + Base64Url(payload) + "." + Base64Url(signature)

I am trying to decode a Base64 format Token after retrieving it from Object store in Anypoint Studio. Help resolve the dataweave error?

1 Answers