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Development Environment Secrets

As developers, we often have to setup development environments that allows us to edit our software source code as well as being able to test run the software in a simulated environment.

When these environments need access external resources such as databases like MySQL or SaaS services like Amazon S3, they require configuration that includes secret credentials.

This configuration can be setup in configuration files, as constants in the source code, or injected at the terminal via environment variables or command line parameters.

In 2011, Heroku developed a methodology called the 12 factor app that argued that the best way of setting secrets for development environments is through environment variables.

Operating systems will run software processes within process environment, and environment variables are key-value strings that can be set prior to launching the program which reads the environment variables on startup.

Developers use shells including bash, zsh and sh to create "parent" program environments that can be inherited by child programs. Environment variables in Unix-shells can be setup in 3 ways:

  • For the shell itself - X=3; echo "$X"
  • For the shell and child programs - export X=3; echo "$X" && sh -c 'echo $X'
  • For the child program and its child programs (but not the shell) - X=3 sh -c 'echo $X'

The command X=3 sh -c 'echo $X' first sets the variable X to 3, then runs the program sh (as a child program with respect to the shell) which will read and output the value of X.

This has several advantages:

  • The environment variables are not persisted in the source code, this avoids a common vector for leaking secrets accidentally via source code version control systems such as Git, GitHub and GitLab.
  • The environment variables can be easily programatically changed depending on different environments, so there is minimal change required between development and production environments.
  • There is only 1 place to set secret configuration, which is the shell/process environment, which simplifies how to configure software.
  • Environment variables are framework and programming language agnostic, all major operating systems support environment variables.
  • Environment variables only exist while the process is alive, when the process dies, the environment variables would automatically be deleted.

There is one major challenge with using environment variables: If environment variables are temporary and only exist while the process is alive, then:

  • How do we remember what environment variables need to be set when we log off for the day and start working on the application after a restart of the computer?
  • How do we communicate what environment variables are required to other developers who are also working on the same software system?
  • How do we handle the increasing number of environment variables to be set as our software gains more features? It would be a chore to have to set them every time we ran our application.

In order to meet these challenges, the development community evolved the above idea into a workflow pattern called "dotenv".

The idea is to create a .env file that is ignored by source code control systems, and is located at the root of your project repository. This file contains all of your application environment configuration, for example:







This file is then loaded into your terminal shell with source ./.env when you start working on the software.

In Matrix AI, we also create a .env.example that is saved into the source control system, which lists all of the environment variables, and has commentary on what they are for. New developers then copy the .env.example to .env before sourcing it into their shell.

However by using .env file we end up now managing a configuration file.

There are still some problems here:

  • The usage of .env is not secure at rest, the .env is a plaintext file and can easily be read by malicious programs or accidentally leaked or exposed.
  • Security in transit isn't addressed, when working with other developers, you still need to communicate the right environment variable values to be used to access AWS, PostgreSQL or other services.
  • Security in use is still primitive, there's nothing to address the principle of least privilege, and nothing tracking secret provenance.
  • If you work on multiple projects with different environment variable configuration, it is possible to mix up your development shell environments by forgetting to exit a shell, and end up clobbering your secret variables

This is where Polykey can help.

Every Polykey node contains multiple vaults. Each vault is an encrypted filesystem. Rather than putting 1 large file containing all the secrets we want like .env, we break up each secret into separate files that will be put into the vault. These secrets can be more easily manipulated. This gives us flexibility to choose which secrets we need, and how they should be injected during use.

In this situation, developers can create a new vault for this project: my-software-project.

pk vault create my-software-project

Once we have this vault, we can now add in every secret that is necessary

# using the argument style, note that we add 1 space ahead of the command ensure CLI history is not tracking this command
pk secrets put my-software-project:AWS_ACCESS_KEY_ID '****'

# using the prompt style, finish the message by sending EOF <CTRL> + <D>
pk secrets put my-software-project:GOOGLE_MAPS_API_KEY
> '****'

# using the file descriptor style
pk secrets put my-software-project:PG_PASSWORD -f ./pg_password_data
# ... now add in all the other secrets

Now when we want to start development on the project, we have 2 options:

  1. Open up a shell with Polykey sourcing the environment variables
  2. Use Polykey to inject environment variables into a sub-shell

Either result is the same, because you'll be running a shell with environment variables set so that your test runs of your software can inherit this environment configuration. Let's demonstrate both.

In the first case, we will reuse the source command and ask pk to constuct the equivalent of the .env file but entirely in-memory and only for this specific usage. We must also use process substitution <(...) so that the pk command output can be redirected into a temporary file descriptor that is read by the source command.

# one secret
source <(pk secrets env my-software-project:AWS_ACCESS_KEY_ID)

# multiple secrets
source <(pk secrets env my-software-project:AWS_ACCESS_KEY_ID my-software-project:GOOGLE_MAPS_API_KEY)

# globbing style (you can use globstar as well, this will only export immediate files)
source <(pk secrets env my-software-project:*)

# use the -e flag to export all variables
source <(pk secrets env -e my-software-project:*)
# use the -- to separate so you can export just one out of many
source <(pk secrets env -- my-software-project:AWS_ACCESS_KEY_ID -e my-software-project:GOOGLE_MAPS_API_KEY)
source <(pk secrets env -e -- my-software-project:AWS_ACCESS_KEY_ID my-software-project:GOOGLE_MAPS_API_KEY)

Now your shell has the relevant environment variables set by Polykey, and they will exist for as long as this current shell is alive.

In the second case, we ill use pk secrets env command to run a subshell, it can run any subprogram, but in the context of a development environment, you usually want a shell.

# one secret
pk secrets env my-software-project:AWS_ACCESS_KEY_ID bash

# multiple secrets
pk secrets env my-software-project:AWS_ACCESS_KEY_ID my-software-project:GOOGLE_MAPS_API_KEY bash

# globbing style
pk secrets env my-software-project:* bash

# the -e flag has no effect when using it this way
# this is because the subprogram determines whether to export variable or not
# it usually exports the variable
pk secrets env -e my-software-project:* bash

Now you have a subshell that has the environment variables configured, it will also automatically export it to child programs. When you have finished your development, you can just exit the shell, and the environment variables are gone!

Doing this with Polykey means you no longer leave around a .env file, however you can still make use of the .env.example to document (give default values and examples) what environment variables are needed when working on the project. However you can also just point your developers to a specific secret vault.

Now when you have other developers also working on the same project, you can share this vault with them through the Polykey network which ensures that the secrets are shared securely without going through any insecure third-party. Furthermore as the project develops, when new secrets and new configuration are added and existing secrets changed, it is trivial to inject these secrets into the vault, and to have your co-developers pull down updates to the vault.

pk vaults pull my-software-project

Polykey can setup automatic pulls regularly to acquire new updates, because the Polykey agent runs in the background.


Show how different development environments can be handled

Show how compose and split vaults

Show how developers inject secrets from development to production

Show how to handle secret provenance here

Show how to rotate secrets easily in your development environment

Show how we handle privilege bracketing (suppose you have a vault, you can refer to a minimal set of secrets when entering an environment)

Show how to export with a different name