RE: base64 URL decode - for jwt

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.



--
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