@briandlee/smuggler

Smuggler

Smuggle encrypted environment variables into your deployment.

Why?

Vercel has a 4KB restriction to the total size of all environment variables. This limitation is especially troublesome if you use Firebase or Google service account authentication or if you require SSL certificates as part of your production application (such as with Google Cloud SQL and Prisma).

https://vercel.com/support/articles/how-do-i-workaround-vercel-s-4-kb-environment-variables-limit

This problem and workaround are well-advertised on several issues in GitHub and a support article provided directly by Vercel. The recommended work around feels hacky to introduce into your code. Furthermore, depending on your build system an actual import might be required in order for the build process to not leave the configuration files behind when the final product is uploaded.

In an attempt to address this with my own organization and provide a stable solution for others to use, smuggler was created.

This package may also help with the common issue of injecting GOOGLE_APPLICATION_CREDENTIALS (the path to a Google service account credentials JSON file) or a Firebase credentials file into your application. See the "The author's use case" below.

Live demo

Take a look at the live demo at https://smuggler.brian-dlee.dev.

The code is in the demo directory.

Getting started

npm i --save @briandlee/smuggler

Config File: .smuggler.json

The following properties are allows in the config file.

Note: if neither includeVariablePrefix or includeFiles are supplied, there is nothing for Smuggler to do.

option	required	description
encryptionKeyEnvironmentVariable	yes	The environment variable that contains the encryption key
encryptionIVEnvironmentVariable	yes	The environment variable that contains the encryption iv
includeVariablePrefix	no	A prefix used to match environment variables to smuggle
includeFiles	no	A list of files to smuggle (as base64)

includeFiles

Entries in includeFiles can take on one of two forms:

type: file

This is used for files that exist on disk somewhere. The file indicated by path will be read and converted to base64 before it's encrypted into the smuggler data file under the name indicated by variable. If the file does not exist or cannot be read, the operation will fail.

interface File {
  type: "file";
  path: string;
  variable: string;
}

type: variable

This is used for files that exist on disk somewhere, but their path is stored in an environment variable. The variable indicated by name will be read, the file it refers to will then be read, and finally it is converted to base64 and encrypted into the smuggler data file under the name indicated by variable, if supplied, or name otherwise. If the variable is not defined, the file does not exist, or the file cannot be read the operation will fail.

interface Variable {
  type: "variable";
  variable?: string;
  name: string;
}

CLI

Operation: prepare

Use prepare to store environment variables and files into an encrypted file that can be uploaded as part of your deployment.

This is part of step-1, in a 2 phase deployment. During part 1, expose sensitive variables to the build environment where they can be read and exported in an encrypted format before being uploaded to the build system (i.e. Vercel) to be packaged with the application during the application build phase.

Operation: generate

Use generate to convert prepared data from phase 1 into application files that can be bundled with your application. Without this step, the encoded variables do not become part of the application and will be shaken as part of builder optimization. If you did not prepare the data beforehand, this step can also do both the preparation and generation.

It's important to run this step as part of the normal development process. Without the generated files that result from this step, the application will not run if smuggler is invoked. Even an empty generated file will close the circuit. A common remedy is to include smuggler generate as part of prestart in your package.json.

Operation: read

Use read to inspect the contents of data resulting from the prepare step. This is only used a debugging tool.

Following the author's use case

Creating the config file

In my case, I prefix variables I want to feed into smuggler with VERCEL_SECRET__, and I store the key and iv parameters for encryption/decryption in the variables VERCEL_ENCRYPTION_KEY and VERCEL_ENCRYPTION_IV as recommended in the support article. If you are using this for Vercel you might want to follow the instructions for creating these variables as outlined in the article. I've retained the encryption algorithm recommended there which requires the key and iv parameters to be 16 character secrets.

The algorithm used in the project can be configured, but the project has not been tailored for those customizations. So make sure you generate your secrets accordingly.

{
  "encryptionKeyEnvironmentVariable": "VERCEL_ENCRYPTION_KEY",
  "encryptionIVEnvironmentVariable": "VERCEL_ENCRYPTION_IV",
  "includeVariablePrefix": "VERCEL_SECRET__",
  "includeFiles": [
    { "type": "variable", "name":  "GOOGLE_APPLICATION_CREDENTIALS", "variable": "GOOGLE_SERVICE_ACCOUNT_CREDENTIALS_JSON_BASE64" }
  ]
}

Execute smuggler prepare during your CI's build phase

All necessary variables must be available during the build phase. With Vercel's CLI you can use -b or --build-env to create them for the build phase only.

Most deployments might happen solely on Vercel's end with a Git integration, but this won't work if you have environment variables exceeding 4KB because there is no where to add them unless they are in version control. If you are venturing down this avenue you've probably found you need to run custom CI calling Vercel's CLI when necessary. prepare should be used during this phase prior to calling Vercel's CLI to commence the build.

This step creates the encrypted data in the intermediate storage location.

Note: All variables you intend to inject into your build must be available during the prepare phase

npx -y @briandlee/smuggler prepare

Add smuggler generate to your build phase

This step copies configuration from the intermediate storage location to the build storage location

A good place for this is in prebuild in your package.json.

  "scripts": {
    "prebuild": "smuggler generate",

I also add it to prestart so the necessary files for startup with smuggler are always present.

Load the configuration at runtime

The data is pre-processed into source code at build time (when smuggler create is ran). Calling read will call this compiled loader, decode the data and return it. In many cases, you may want to cache this result so you do not end up decoding data multiple times during your apps execution unless you are worried about the vulnerability of holding secret data in memory or if your config data is really large.

Your key and iv values must be available for read to work.

import { writeFileSync } from "fs";
import { read, withDefaultReadOptions } from '@briandlee/smuggler';
import { randomString } from "~/utils/my-random-lib"

const data = read(withDefaultReadOptions({
  key: process.env.VERCEL_ENCRYPTION_KEY,
  iv: process.env.VERCEL_ENCRYPTION_IV
}));

// Read and write my Google service account credentials
if (data.GOOGLE_SERVICE_ACCOUNT_CREDENTIALS_JSON_BASE64) {
  const filePath = `/tmp/${randomString(64)}.json`;
  writeFileSync(
    filePath,
    Buffer.from(data.GOOGLE_SERVICE_ACCOUNT_CREDENTIALS_JSON_BASE64, 'base64')
  );
  process.env.GOOGLE_APPLICATION_CREDENTIALS = filePath;
}

An Example

See the example for an illustration for how the package is designed to be used.

Caveats

• At the time of writing this, I'm using Remix (which uses esbuild). If you are using another framework that uses a different build system you encounter a situation where the smuggler data is pruned from the final build (maybe in the case of Next.js and their use of nft).

TODO

• [ ] Support additional encryption methods

---

Made by me.