Re: base64 URL decode - for jwt

Hi Jay,

I had the same problem with my small JWT library.

The easiest way to decode a base64url encoded string is, you have to do:

1. replace all "-" with "+"
2. replace all "_" with "/"
3. try to decode as base64
4. if it fails, append "=" and try to decode again as base64
5. if it fails, append another "=" and try to decode again as base64

I implemented that in RPG and the base64 decode with SQL (because I'm lazy).

HTH
Daniel

Am 04.03.2025 um 20:27 schrieb Jay Vaughn <jeffersonvaughn@xxxxxxxxx>:

I'm looking at decoding a jwt and discovered it can be base 64 decoded but
not just base64 but base64 URL.

I know we have the qsys2.base64_decode scalar function provided by db2 -
but what about a base64 URL version?

OR does someone know a simple way to decode the jwt using native languages
and sql/db2 on the IBM i?

It is my understanding there is a header/body/footer(signature) in each -
it is the body that is decodable.

any suggestions?

tia

Jay
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