Python client for IP to ASN lookup services

aslookup is a client utility for two of the public IP/AS query services operated by the following organizations:

• Shadowserver -- https://www.shadowserver.org/wiki/pmwiki.php/Services/IP-BGP
• Team Cymru -- http://www.team-cymru.org/IP-ASN-mapping.html

The client implements both a simple Python module (aslookup) as well as a CLI utility (as-lookup). The lookups are currently done using DNS, which works well for a one-off lookups. It is not optimized for bulk lookups over the Whois protocol.

Currently only IPv4 addresses are looked up. The client also maintains a listing of IP networks which are unroutable internet addresses, typically special use ranges in RFCs. In this way it can both filter out addresses from queries which are a waste of time, as well as provide context to the user on the address.

The app has been tested on Python 3.

It's best to install the program into a Python virtualenv. If you will only use the command line interface, the recommended way to install it is using pipx:

pipx install aslookup

If you will use aslookup as a library, you'll instead want to install it using pip in your target Python environment:

python3 -m pip install aslookup

The Python module defaults to querying the Team Cymru data service. The desired service may be specified by passing the service parameter to get_as_data.

from aslookup import get_as_data
ip = "8.8.8.8"
get_as_data(ip, service="shadowserver")

It is possible to provide multiple IP addresses as arguments to the script, or to send them as a list on standard input, in which cases the script loops over them and returns output on separate lines. When providing invalid IPv4 addresses as arguments, the script reports the problem on standard error and exits with an error. When providing input on stdin, the error is reported on standard output but execution is not aborted.

as-lookup 8.8.8.8 9.9.9.9

or:

as-lookup < ipaddrs.txt

A list of test values for the script is included in the file tests/test_input.txt. This can be useful to validate included IP prefix classifications and see the output format.

as-lookup < tests/test_input.txt