Check an owned endpoint TLS certificate

Before you begin

• Python 3.12 or later.
• A reachable TLS service you own or are authorized to inspect, with a certificate trusted by the OS/Python store.

Set up your example

1. Save as security-tls-expiry.py.
2. Open a terminal in its folder.
3. Run python "security-tls-expiry.py" --help and prepare the listed input files.

This recipe uses your own local input or creates its own example output. Follow the setup steps below.

Download the ZIP, extract it, and open a terminal inside the extracted folder. The source file is security-tls-expiry.py.

Run the script

python "security-tls-expiry.py" --host localhost --port 443

If your system uses python3 instead of python, use that command for Python examples. Keep paths containing spaces in quotes. Required inputs and optional settings are described in the code and setup steps.

What to expect

The complete script

#!/usr/bin/env python3
"""Make one verified TLS connection and report the leaf certificate expiry and protocol."""
import argparse
import sys
import json
from pathlib import Path
import ssl
import socket
from datetime import datetime,timezone

def main():
    parser = argparse.ArgumentParser(description='Make one verified TLS connection and report the leaf certificate expiry and protocol.')
    parser.add_argument('--host',default='localhost')
    parser.add_argument('--port',type=int,default=443)
    args = parser.parse_args()
    if not 1<=args.port<=65535:raise ValueError('--port must be 1..65535')
    context=ssl.create_default_context()
    with socket.create_connection((args.host,args.port),timeout=10) as raw:
        with context.wrap_socket(raw,server_hostname=args.host) as connection:
            cert=connection.getpeercert()
            expiry=datetime.fromtimestamp(ssl.cert_time_to_seconds(cert['notAfter']),timezone.utc)
            print(json.dumps({'host':args.host,'protocol':connection.version(),'expires_utc':expiry.isoformat(),'days_remaining':(expiry-datetime.now(timezone.utc)).days}))

if __name__ == '__main__':
    try:
        main()
    except (OSError, ValueError, RuntimeError) as exc:
        print(f'Error: {exc}', file=sys.stderr)
        sys.exit(1)

Open source as plain text · Download source and sample files

How it works

1. Make one verified TLS connection and report the leaf certificate expiry and protocol.
2. Arguments are explicit and expected input errors produce a message with a nonzero exit code.
3. Results reflect your selected local data or the specific endpoint you choose; the example illustrates the result shape.

Make it your own

Adapt the task

Set --host and --port to one endpoint you administer. Do not disable certificate validation to hide verification failures.

Adjust presentation

Edit final print statements or json.dumps indentation to adjust the report layout. Keep input validation and exclusive-create file modes intact.

Change one setting at a time, run it again on sample data, and compare the output. The customization guide walks through this process.

If something goes wrong

Reference & next steps

• Python standard library documentation ↗

These official references explain the underlying tools. The Scriptage example and guide are original instructional content. See verification notes for what has been checked and the limits of those checks.

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