Custom TLS certificates

How to use custom TLS certificates with LocalStack

Background

LocalStack sometimes performs on-demand fetching of resources from the public internet. This requires that LocalStack is able to access public URLs. If there is a proxy server in your network that uses a non-standard TLS certificate, LocalStack will not be able to download any files on demand. You may see errors in the logs relating to TLS such as “unable to get local issuer certificate”.

Solution

There are three options when running LocalStack:

  1. creating a custom Docker image,
  2. using init hooks or
  3. when running in host mode.

They all can be summarised as:

  1. get your proxy’s custom certificate into the system certificate store, and
  2. configure requests to use the custom certificate, and
  3. configure curl to use the custom certificate.

Creating a custom docker image

If you run LocalStack in a docker container (which includes using the CLI, docker, docker-compose, cockpit or helm), to include a custom TLS root certificate a new docker image should be created.

Create a Dockerfile containing the following commands:

FROM localstack/localstack:latest
# or if using the pro image:
FROM localstack/localstack-pro:latest

COPY <your custom certificate.crt> /usr/local/share/ca-certificates/cert-bundle.crt
RUN update-ca-certificates
ENV CURL_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt
ENV REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt

and build the image:

$ docker build -t <image name> .

Starting LocalStack with the custom image

LocalStack now needs to be configured to use this custom image. The workflow is different depending on how you start localstack.

IMAGE_NAME=<image name> localstack start
docker run <docker arguments> <image name>
services:
  localstack:
    image: <image name>
    # the rest of your configuration

Custom TLS certificates with init hooks

It is recommended to create a boot init hook. Create a directory on your local system that includes

  • the certificate you wish to copy, and
  • the following shell script:
#!/bin/bash

set -euo pipefail

cp /etc/localstack/init/boot.d/<your certificate file>.crt /usr/local/share/ca-certificates
update-ca-certificates

Then run LocalStack with the environment variables

  • REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt, and
  • CURL_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt, and

and follow the instructions fn the init hooks documentation for configuring LocalStack to use the hook directory as a boot hook.

Custom TLS certificates with host mode

Linux

On linux the custom certificate should be added to your ca-certificates bundle. For example on Debian based systems (as root):

# cp <your custom certificate.crt> /usr/local/share/ca-certificates
# update-ca-certificates

Then run LocalStack with the environment variables REQUESTS_CA_BUNDLE and CURL_CA_BUNDLE:

$ CURL_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt localstack start --host

macos

On macos the custom certificate should be added to your keychain. See this Apple support article for more information.

Then run LocalStack with the environment variables REQUESTS_CA_BUNDLE and CURL_CA_BUNDLE:

$ CURL_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt REQUESTS_CA_BUNDLE=/etc/ssl/certs/ca-certificates.crt localstack start --host

Windows

Currently host mode does not work with Windows. If you are using WSL2 you should follow the Linux steps above.


Last modified December 15, 2022: Document custom ssl certificate (#404) (156be24e)