pretty-print a browserid assertion

gistfile1.py

import base64
import json
from datetime import datetime

def decodeB64(b64input):
    """
    Add padding to b64input if necessary.  I think python's base64
    implementation is broken and this should not be necessary.
    """
    out = b64input.strip()
    lastBytesLen = len(out) % 4
    if lastBytesLen == 0:
        pass
    elif lastBytesLen == 3:
        out += '='
    elif lastBytesLen == 2:
        out += '=='
    else:
        print out, lastBytesLen
        raise Exception("Bad base64 input; last group contained weird number of bytes.")

    return base64.b64decode(out)

def decode(encoded):
    return json.loads(decodeB64(encoded))

def unpackAssertion(assertion):
    # ignore signatures; we're not a verifier
    header, claim, _, payload, _ = assertion.split('.');
    return {"header": decode(header),
            "claim": decode(claim),
            "payload": decode(payload)}

def printAssertionSummary(data):
    email = data['claim']['principal'].get('email', '')
    unverified_email = data['claim']['principal'].get('unverified-email', '')
    exp = datetime.fromtimestamp(int(data['payload']['exp']) / 1000.0).strftime('%Y-%m-%d %H:%M:%S')
    iss = data['claim']['iss']
    aud = data['payload']['aud']

    print """\
 Issuer:           %(iss)s
 Audience:         %(aud)s
 Email:            %(email)s
 Unverified Email: %(unverified_email)s
 Expires:          %(exp)s
""" % (vars())

# Example:
#
# printAssertionSummary(unpackAssertion(assertion))