If you find yourself in need of running serverless locally using serverless offline and you want an SSL certificate then fear not, it's not all that difficult. First you'll need an SSL certificate. For our purposes you we're going to use a self-signed certificate. This will cause browsers to complain but for local testing it isn't typically a big problem.
Generate a Cert Using OpenSSL
You should install OpenSSL (or one of the more secure alternatives like LibreSSL) and then run
openssl req -newkey rsa:2048 -nodes -keyout key.pem -x509 -days 365 -out cert.pem
This will prompt you for a bunch of information about your organization. You can put anything you want in most of those fields but do pay attention to the
Common Name field which needs to hold the value of
These are the answers I gave
Country Name (2 letter code) [AU]:US
You should now have a
cert.perm and a
key.pem in your local directory. Copy these into a
cert folder at the root of your serverless project.
Running with the Certificate
Now you need to tell serverless where to find your certificate. You can either run with the flag
custom: serverless-offline: httpsProtocol: "cert" ...
If you're seeing a warning about an invalid certificate then check that you're accessing serverless via `localhost` and not `127.0.0.1` or `0.0.0.0`. SSL works with domain names so you need to use one, even if it is just `localhost`.