Simple script to validation ssl certificate expiration dates
Python
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README.md

SSL Expiry

A simple script to check the expiration date on a list of domains.

This simple python 3 utility is meant to be deployed as a cron or run from a lambda service.

Usage

$ echo "google.com\nfacebook.com" | python ssl_expiry.py
> google.com cert is fine
> facebook.com cert is fine

Install

Setup your python environment and test it as follows.

$ conda env create -f environment.yml
$ source activate ssl-expiry
$ echo "google.com\nfacebook.com" | python ssl_expiry.py

AWS API Gateway and Lambda

AWS Lambda

To deploy to Lambda, create a zip that contains ssl_expiry.py and ssl_expiry_lambda.py and then follow the normal instructions to setup and configure a Lambda function. The ssl_expiry_lambda will use, if they exist, two env parameters:

  • HOSTLIST: a comma separated string of hostnames to validate, and
  • EXPIRY_BUFFER: an int that represents the days prior to expiration that the script will alert for, ie alert if the expiration is within EXPIRY_BUFFER days.

AWS API Gateway

Once the Lambda is configured, you can setup a new api in API Gateway. The important parts that are not obvious from the API Gateway admin ui are as follows:

You will need to create a new Integration Response for the exception that is raised when the check finds a failing or soon to fail certificate.

I configured this a a new Integration Response with a regex of

.*Cert Errors.*

and a Body Mapping Template with content type application/json and the template:

#set($inputRoot = $input.path('$'))
$input.path('$.errorMessage')

With this configuration, the exception raised by the main method will be parsed and returned as the body of the response. The HTTP status code will be a 400.

Additionally, in the Method Request section, I declared URL Query String Parameters for host_list and expiry_buffer.

Finally, you should also define a Method Response for the 400 status. This can be left with all for the default empty values for response headers and response body.