def sign()

in functions/source/populate_NLB_TG_with_ALB/dns/tsig.py [0:0]

• 44 lines of code
• 8 McCabe index (conditional complexity)

def sign(wire, keyname, secret, time, fudge, original_id, error,
         other_data, request_mac, ctx=None, multi=False, first=True,
         algorithm=default_algorithm):
    """Return a (tsig_rdata, mac, ctx) tuple containing the HMAC TSIG rdata
    for the input parameters, the HMAC MAC calculated by applying the
    TSIG signature algorithm, and the TSIG digest context.
    @rtype: (string, string, hmac.HMAC object)
    @raises ValueError: I{other_data} is too long
    @raises NotImplementedError: I{algorithm} is not supported
    """

    if isinstance(other_data, text_type):
        other_data = other_data.encode()
    (algorithm_name, digestmod) = get_algorithm(algorithm)
    if first:
        ctx = hmac.new(secret, digestmod=digestmod)
        ml = len(request_mac)
        if ml > 0:
            ctx.update(struct.pack('!H', ml))
            ctx.update(request_mac)
    id = struct.pack('!H', original_id)
    ctx.update(id)
    ctx.update(wire[2:])
    if first:
        ctx.update(keyname.to_digestable())
        ctx.update(struct.pack('!H', dns.rdataclass.ANY))
        ctx.update(struct.pack('!I', 0))
    long_time = time + long(0)
    upper_time = (long_time >> 32) & long(0xffff)
    lower_time = long_time & long(0xffffffff)
    time_mac = struct.pack('!HIH', upper_time, lower_time, fudge)
    pre_mac = algorithm_name + time_mac
    ol = len(other_data)
    if ol > 65535:
        raise ValueError('TSIG Other Data is > 65535 bytes')
    post_mac = struct.pack('!HH', error, ol) + other_data
    if first:
        ctx.update(pre_mac)
        ctx.update(post_mac)
    else:
        ctx.update(time_mac)
    mac = ctx.digest()
    mpack = struct.pack('!H', len(mac))
    tsig_rdata = pre_mac + mpack + mac + id + post_mac
    if multi:
        ctx = hmac.new(secret, digestmod=digestmod)
        ml = len(mac)
        ctx.update(struct.pack('!H', ml))
        ctx.update(mac)
    else:
        ctx = None
    return (tsig_rdata, mac, ctx)