Re: base64 URL decode - for jwt

Hi Chris

As I understand it, and I think Jay mentioned it, the so-called BASE4
part is actually BASE64URL - this replaces a couple things in BASE64
that don't work in URLs - like a forward slash, I believe. I forget, but
I looked it up.

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*Vern Hamberg*

IBM Champion 2025 <cid:part1.yF3xcJ7F.stqK4olY@centurylink.net> CAAC
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On 3/10/2025 2:58 PM, Hiebert, Chris via MIDRANGE-L wrote:

From my understanding, you need to split the three strings before you

attempt to base64 decode.

A snipped from my RPG code uses:


TokenID Varchar(512);

Dcl-s splitSession Varchar(512) dim(3);
Dcl-s decoded_key char(4096) CCSID(*UTF8);

splitSession = %Split( TokenID :'.');

len = base64_decode( %Addr( splitSession(2) :*data ) :

%len(splitSession(2))

: %Addr( decoded_key ) : %Size( decoded_key ) );


Then parse the Json string now contained in decoded_key.

I imported Scott Klement’s BASE64R4 service program code a few years go

and use that base64_decode procedure in RPG.

Also, you shouldn’t need to Cast your string to 1208. Once decoded it

should BE 1208 already.

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Chris Hiebert
Lead Software Developer
Disclaimer: Any views or opinions presented are solely those of the

author and do not necessarily represent those of the company.

From: MIDRANGE-L<midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of

Jay Vaughn

Sent: Wednesday, March 5, 2025 11:50 AM
To: Midrange Systems Technical Discussion<midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: base64 URL decode - for jwt


yeah this is definitely the piece I cannot hack.



I did a base64 encode in another project and before the encoding I'd

declare an rpg variable as varchar(256) and ccsid(1208)

then base64 encode would work fine.



but



base64_decode will result in a blob...



and even though I'm doing a...



set o_token = cast( qsys2.base64_decode(trim(i_token))

as varchar(2048) ccsid 1208);



It is still not legible. (even if I remove the ccsid 1208 - it is not

legible.



Daniel, are you able to reference any live code and tell me which part

I'm

missing here?



thanks



Jay

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