dkpriv

#!/usr/bin/python3
#
# SPDX-License-Identifier: 0BSD
# Part of badkeys: https://badkeys.info/
#
# Sometimes, people accidentally publish private keys in DKIM records,
# script to extract them.

import argparse
import base64
import pathlib

from cryptography.hazmat.primitives import serialization

ap = argparse.ArgumentParser()
ap.add_argument("input", nargs="+")
args = ap.parse_args()

for fn in args.input:
    raw = pathlib.Path(fn).read_text()
    raw = raw.replace(" ", "").replace('"', "")
    for el in raw.split(";"):
        if el.startswith("p="):
            bkey = el[2:]
            break
    der = base64.b64decode(bkey.encode())
    pkey = serialization.load_der_private_key(der, password=None)
    pem = pkey.private_bytes(serialization.Encoding.PEM,
                             serialization.PrivateFormat.TraditionalOpenSSL,
                             serialization.NoEncryption()).decode()
    print(pem, end="")