Question

I have a string saved to a database that is encoded by Actionscript by base64ing it and then zlib compressing it.

An example string is this: “eNrj4mZkrShgWdHBx1mUmJfNosQIACUhBCI=”

If I unzip and un base64 this via Actionscript, I get what I expect:

{“xp”: 656398, “rank”: 34}

But, I need to be able to also read this server-side. For now I’m using Python but I’d be open to a working PHP solution or similar.

So far in Python I have tried this:

import base64
import zlib

s = 'eNrj4mZkrShgWdHBx1mUmJfNosQIACUhBCI='

print s.decode("base64").decode("zlib")

It looks like Actionscript adds some extra bits into the header, but my Python is not strong enough to defeat this 🙂 Any help would be much appreciated!

EDIT: Actionscript first takes an AS Object and converts it to a ByteArray, before zlib compressing it and base64ing it. It looks like this is what is generating the extra header/mangled data info.

Answer 1

Flash could be mangling this, but you should share an example from Actionscript that creates and checks this data.

If you’re using a 3rd party library, it might be using an alternate characterset than Python is expecting.

if you’re using the official library, it seems that Actionscript implements UTF8 and ascii differently. ( there are different methods here – http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/mx/utils/Base64Encoder.html)

it’s much easier to just see the actionscript and note if there’s an issue with the library or your code, than try to reverse engineer this.

I think it also might be worth trying to bugfix this in reverse…

import base64
import zlib

flash =  "eNrj4mZkrShgWdHBx1mUmJfNosQIACUhBCI="

original = '{"xp": 656398, "rank": 34}'
encoded = original.encode('zlib').encode('base64')
decoded = encoded.decode('base64').decode('zlib')
print original
print encoded
print decoded

Can I also ask why you’re even doing this ?

1- unless your packets are much bigger, you’re not going to be saving much bandwidth. in fact, compression on small payloads can actually increase the size.

2- assuming this is web based, you should be able to have the server do this on the fly.