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dc38e1f Apr 21, 2018
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@thusoy @xbglowx
executable file 104 lines (80 sloc) 2.88 KB
#!/usr/bin/env python
import argparse
import socket
import ssl
import struct
import subprocess
import sys
try:
from urlparse import urlparse
except ImportError:
from urllib.parse import urlparse
def main():
args = get_args()
target = get_target_address_from_args(args)
sock = socket.create_connection(target)
try:
certificate_as_pem = get_certificate_from_socket(sock)
print(certificate_as_pem.decode('utf-8'))
except Exception as exc:
sys.stderr.write('Something failed while fetching certificate: {0}\n'.format(exc))
sys.exit(1)
finally:
sock.close()
def get_args():
parser = argparse.ArgumentParser()
parser.add_argument('database', help='Either an IP address, hostname or URL with host and port')
return parser.parse_args()
def get_target_address_from_args(args):
specified_target = args.database
if '//' not in specified_target:
specified_target = '//' + specified_target
parsed = urlparse(specified_target)
return (parsed.hostname, parsed.port or 5432)
def get_certificate_from_socket(sock):
request_ssl(sock)
ssl_context = get_ssl_context()
sock = ssl_context.wrap_socket(sock)
sock.do_handshake()
certificate_as_der = sock.getpeercert(binary_form=True)
certificate_as_pem = encode_der_as_pem(certificate_as_der)
return certificate_as_pem
def request_ssl(sock):
# 1234.5679 is the magic protocol version used to request TLS, defined
# in pgcomm.h)
version_ssl = postgres_protocol_version_to_binary(1234, 5679)
length = struct.pack('!I', 8)
packet = length + version_ssl
sock.sendall(packet)
data = read_n_bytes_from_socket(sock, 1)
if data != b'S':
raise Exception('Backend does not support TLS')
def get_ssl_context():
# Return the strongest SSL context available locally
for proto in ('PROTOCOL_TLSv1_2', 'PROTOCOL_TLSv1', 'PROTOCOL_SSLv23'):
protocol = getattr(ssl, proto, None)
if protocol:
break
return ssl.SSLContext(protocol)
def encode_der_as_pem(cert):
# Forking out to openssl to not have to add any dependencies to script,
# preferably you'd do this with pycrypto or other ssl libraries.
cmd = ['openssl', 'x509', '-inform', 'DER']
pipe = subprocess.PIPE
process = subprocess.Popen(cmd, stdin=pipe, stdout=pipe, stderr=pipe)
stdout, stderr = process.communicate(cert)
if stderr:
raise Exception('OpenSSL error when converting cert to PEM: {0}'.format(stderr))
return stdout.strip()
def read_n_bytes_from_socket(sock, n):
buf = bytearray(n)
view = memoryview(buf)
while n:
nbytes = sock.recv_into(view, n)
view = view[nbytes:] # slicing views is cheap
n -= nbytes
return buf
def postgres_protocol_version_to_binary(major, minor):
return struct.pack('!I', major << 16 | minor)
if __name__ == '__main__':
main()