get_known_host_entry.py

#!/usr/bin/env python3
import argparse
import base64
import hashlib
import hmac
import os


def match(line, hostname):
    host_str = line.split(' ')[0]
    if host_str.startswith('|'):
        host_array = host_str.split('|')
        salt = base64.b64decode(host_array[-2])
        result = hmac.digest(salt, hostname.encode(), hashlib.sha1)
        return base64.b64encode(result) == host_array[-1].encode()
    else:
        return hostname in host_str.split(',')

    
def print_known_host_entry(hostname_or_ip, port):
    if port != 22:
        hostname_or_ip = f'[{hostname_or_ip}]:{port}'
    with open('{}/.ssh/known_hosts'.format(os.getenv("HOME"))) as f:
        for line in f.readlines():
            if match(line, hostname_or_ip):
                print(line)


def main():
    parser = argparse.ArgumentParser(
        description='get host entry from ~/.ssh/known_hosts')
    parser.add_argument('hostname_or_ip')
    parser.add_argument('-p', type=int, default=22)
    args = parser.parse_args()
    print_known_host_entry(args.hostname_or_ip, args.p)

if __name__ == '__main__':
    main()