Digital Doodlings
Securely Sharing SSH Authentication With Docker Containers.
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Table of Contents

Problem

In the world of DevOps and containerization, securely managing access to resources is a critical aspect. One common challenge is sharing SSH authentication with a Docker container in a secure manner. There are several approaches to this, but not all are created equal when it comes to security and convenience.

One common but less secure approach is to directly mount SSH keys into the Docker container. While this method is straightforward, it exposes the keys to anyone who can access the container, and it makes key management more difficult.

Solution

Let's delve into a more secure and efficient approach: using the host's SSH agent within the Docker container. This method avoids exposing the keys directly, provides better key management, and can be more convenient for developers.

On the host:

ssh-add ~/.ssh/id_ed25519
ssh-add -l
docker run --rm -t -i  -v /run/host-services/ssh-auth.sock:/ssh-agent \
    -e SSH_AUTH_SOCK="/ssh-agent" alpine sh

Within the container:

apk add openssh
ssh-add -l

Conclusion

In conclusion, these commands allow you to manage SSH keys and run Docker containers with SSH access. This approach of using the host's SSH agent within the Docker container, rather than mounting the private key directly into the container, is a more secure method for a couple of reasons:

  1. Key Exposure: By using the SSH agent socket, we avoid copying the private key into the Docker container. This reduces the risk of the key being exposed to anyone who can access the container.

  2. Key Lifespan: The SSH agent automatically handles key lifespan and can be configured to automatically lock or remove keys after a certain period of time. This is not possible if the key is simply copied into the container.

  3. Key Management: Using the SSH agent allows for better key management, as keys can be added or removed from the agent without having to rebuild or restart the Docker container.

These commands are powerful tools in your developer toolkit, and understanding them can help you work more efficiently and securely. By leveraging the SSH agent, you can maintain a high level of security while still providing your Docker containers with the access they need.