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#!/usr/bin/python3
import socket
import ssl
import argparse
import time
import sys
import configparser
import os
# Sends authentication request to MFA server
# Receive either pass or fail response from MFA server
# Returns status to PAM
HEADER_LENGTH = 64
KEY_LENGTH = 64
ACK_LENGTH = 3
DISCONNECT_MESSAGE = "DISCONNECT"
FORMAT = "utf-8"
RESPONSE_LENGTH = 1
PAM_SUCCESS = 0
PAM_AUTH_ERR = 7
def die(msg):
print(msg)
sys.exit(1)
def parse_arguments():
# Parse command line arguments
parser = argparse.ArgumentParser()
parser.add_argument("--user",type=str,help="PAM username",required=True)
parser.add_argument("--service",type=str,help="PAM service",required=True)
parser.add_argument("--host",type=str,help="PAM hostname")
parser.add_argument("--config",type=str,help="Path to config file",\
default="/etc/mfa/mfa.conf")
parser.add_argument("--server",type=str,help="MFA server address")
parser.add_argument("--port",type=str,help="MFA server PAM connection port")
parser.add_argument("--plain",action="store_true",help="Connect without TLS")
parser.add_argument("--insecure",action="store_true",
help="Accept invalid TLS certificates")
return parser.parse_args()
def init_connection_tls(mfa_server, pam_port, insecure):
# Attempts to connect to MFA server with provided address and port
# Repeats connection attempts once per second until timeout is reached
# Returns the socket if connection was successful or None otherwise
connection = None
timeout = 0
timeout_length = 5
sleep_length = 1
context = ssl.create_default_context()
if insecure:
context.check_hostname = False
context.verify_mode = 0
while connection == None and timeout < timeout_length:
try:
connection = context.wrap_socket(socket.socket(socket.AF_INET),
server_hostname=mfa_server)
connection.connect((mfa_server,int(pam_port)))
return connection
except (ConnectionError,ConnectionRefusedError):
time.sleep(sleep_length)
timeout += sleep_length
except ssl.SSLCertVerificationError:
die("error: server presented invalid certificate")
return None
def init_connection(mfa_server, pam_port):
# Attempts to connect to MFA server with provided address and port
# Repeats connection attempts once per second until timeout is reached
# Returns the socket if connection was successful or None otherwise
connection = None
timeout = 0
timeout_length = 5
sleep_length = 1
while connection == None and timeout < timeout_length:
try:
connection = socket.create_connection((mfa_server,pam_port))
return connection
except (ConnectionError,ConnectionRefusedError):
time.sleep(sleep_length)
timeout += sleep_length
return None
def read_config(config_file):
# Read config file for server and port info
# Return tuple (server,port)
server = ""
port = 0
with open(config_file) as conf:
line = None
while line != "":
line = conf.readline()
if line.startswith("server ="):
server = line.split("=")[1].strip()
if line.startswith("port ="):
port = int(line.split("=")[1].strip())
return (server,port)
def read_config(config_file):
parser = configparser.ConfigParser(inline_comment_prefixes="#")
parser.read(config_file)
return parser
def get_vars(args,confparser):
if not os.path.exists(args.config):
print("Unable to open config file")
sys.exit(1)
server = None
port = None
plain = None
insecure = None
# Set values from config file first
if confparser.has_section("pam"):
server = confparser.get("pam","server",fallback=None)
port = confparser.get("pam","port",fallback=None)
plain = confparser.get("client","plain",fallback=False)
insecure = confparser.get("client","insecure",fallback=False)
if plain.lower() == "false":
plain = False
if insecure.lower() == "false":
insecure = False
# Let command line args overwrite any values
if args.server != None:
server = args.server
if args.port != None:
port = args.port
if args.plain:
plain = args.plain
if args.insecure:
insecure = args.insecure
# Exit if any value is null
if None in [server,port]:
print("error: one or more items unspecified")
sys.exit(1)
return server,port,plain,insecure
def main():
authed = "0"
failed = "1"
# Get arguments
args = parse_arguments()
confparser = read_config(args.config)
mfa_server,pam_port,plain,insecure = get_vars(args,confparser)
user = args.user
service = args.service
# Compile data to send to server
# Read server and port from config file but allow command line options
# to override those settings
if args.server != None:
mfa_server = args.server
if args.port != None:
pam_port = args.port
# Get hostname if not given on command line
if args.host == None:
with open("/etc/hostname") as f:
hostname = f.read().strip()
else:
hostname = args.host
data = user + "," + hostname + "," + service
# Initalize connection to MFA server. Quit if unable to connect.
if plain:
connection = init_connection(mfa_server, pam_port)
else:
connection = init_connection_tls(mfa_server,pam_port,insecure)
if connection == None:
die("failed to connect")
# Send authentication data to MFA server
data_length = len(data)
length_msg = str(data_length)
length_msg += ' ' * (HEADER_LENGTH - len(length_msg))
connection.send(length_msg.encode(FORMAT))
connection.send(data.encode(FORMAT))
# Listen for response from MFA server
# Response will be 0 for authenticated and 1 for denied
response = connection.recv(RESPONSE_LENGTH).decode(FORMAT)
if response == "":
# lost connection to server
response = 1
# Print success/failure for PAM module
print(response)
if __name__ == '__main__':
main()
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