SSL Certificate Chain Validator

A Python tool for downloading, validating, and saving SSL certificate chains from domains.

Features

• Downloads complete SSL certificate chains from domains
• Validates certificate chain integrity
• Checks certificate date validity
• Verifies basic constraints
• Saves certificate chains in PEM format
• Supports custom port specification

Setup

• Create and activate a virtual environment:

python3 -m venv venv
source venv/bin/activate

• Install dependencies:

pip install -r requirements.txt

Usage

Basic usage:

python get_cert.py uwaterloo.ca

With custom port:

python get_cert.py uwaterloo.ca --port 8443

Output

The script will:

1. Fetch the certificate chain
2. Validate the certificates
3. Display validation results
4. Save the certificate chain to certs/domain-chain.pem

Example output:

Fetching certificate chain for uwaterloo.ca:443...

Validation Results for uwaterloo.ca:
------------------------------------------------------------
✓ Date Validity:
  Valid from 2024-01-01 00:00:00 to 2025-01-01 00:00:00
✓ Basic Constraints:
  Certificate extensions are present
✓ Chain of Trust:
  Certificate chain validates successfully
------------------------------------------------------------
Certificate chain saved to: certs/example.com-chain.pem
Number of certificates in chain: 3

Requirements

• Python 3.6+
• pyOpenSSL

Directory Structure

.
├── README.md
├── requirements.txt
├── get_cert.py
└── certs/           # Created automatically when saving certificates
    └── *.pem       # Certificate chain files