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How to use self-signed certificates?


  • If you want to use https in your local dev setup and you don't want to generate public certificates with Let'sEncrypt or something similar.
  • NEVER use self-signed certificates in production unless you absolutely know what you are doing!

How it works

Entities you should be aware of:

  • private CA - a private certificate authority that can generate TLS certificates. Since this is not a publicly recognized CA, its certificates will not be respected by (almost) anyone - but you can teach OPAL to respect that CA's certificates.
  • localserver - a local program running with https:// signed with a certificate that was generated by the "private" CA.
  • opal-client - can be directed to fetch data from localserver, can be told to respect the private CA's certificates

How to generate self-signed certificates

  1. Generate a private key for the "private" CA
openssl genrsa -des3 -out ca-private-key.key 2048
  1. Generate a public key / certificate for the "private" CA
openssl req -x509 -new -nodes -key ca-private-key.key -sha256 -days 365 -out ca-public.crt
  1. Generate a private key for the "localserver" service
openssl genrsa -out localserver-private.key 2048
  1. Generate a certificate request signed by the "localserver" private key. NOTE: you must specify the FQDN to be the host of the (self-signed) https service, e.g: localhost
openssl req -new -key localserver-private.key -out localserver-request.csr
  1. Your "private" CA self-signs on the certificate request and generates a valid self-signed certificate
openssl x509 -req -in localserver-request.csr -CA ca-public.crt -CAkey ca-private-key.key -CAcreateserial -out localserver-cert.crt -days 365 -sha256

configuring a uvicorn service to use the private certificate as the HTTPs certificate

uvicorn myservice.main:app --reload --port=8000 --ssl-keyfile=localserver-private.key --ssl-certfile=localserver-cert.crt

Configuring a data entry (via OPAL_DATA_CONFIG_SOURCES) to redirect to the self-signed https service

Run OPAL server with:


Teaching the opal-client to respect the self signed certificate

Run OPAL client with:


If you run OPAL client with docker - don't forget to mount /path/to/ca-public.crt on a docker volume.