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Pouch

Secret management tool written in Swift. This was heavily inspired by CcocoaPods-Keys & NSHipster article regarding secret management.

Usage

Set up a config file for a project once:

secrets:
- API_KEY
- API_SECRET
outputs:
- ./Secrets.swift

Now, with API_KEY and API_SECRET stored in environment variables, you can generate a file with secrets using:

pouch retrieve

Which should generate an output similar to this one (applied xor on a string (+ randomly generated salt) with a reverse func to read it in the app)):

import Foundation

enum Secret {
    static let apiKey: String = Secret._xored([15, 26, 26, 243, 46, 124, 234, 140, 48, 169, 192], salt: [97, 115, 121, 150, 65, 18, 143, 225, 81, 221, 165, 134, 36, 222, 157, 20, 172, 203, 97, 8, 26, 81, 49, 144, 147, 1, 197, 21, 35, 32, 83, 156, 247, 108, 211, 108, 202, 174, 119, 134, 141, 176, 180, 38, 171, 110, 89, 21, 213, 32, 171, 146, 63, 245, 87, 139, 162, 194, 63, 57, 75, 0, 165, 122, 142])
    static let apiSecret: String = Secret._xored([153, 59, 35, 31, 242, 106, 45, 3, 19, 67, 207, 9, 190, 40, 55, 197, 218, 221, 1, 40, 170, 117, 103, 211, 204, 168, 44, 18, 39, 207, 44, 158, 217, 135, 163, 16, 145, 120, 158, 221, 212, 49, 229, 116, 188, 145, 91, 203, 174, 184, 158, 78, 146, 106, 100, 166, 93, 239, 8, 18, 38, 129, 97, 249, 218, 137, 48, 58, 80, 252, 102, 47, 7, 92, 90, 194, 64, 61, 151, 221, 39], salt: [252, 85, 73, 112, 139, 3, 67, 100, 51, 55, 167, 96, 205, 8, 68, 168, 187, 177, 109, 8, 222, 26, 8, 191, 243, 136, 101, 50, 80, 160, 89, 242, 189, 167, 207, 127, 231, 29, 190, 174, 187, 92, 128, 84, 212, 244, 55, 187, 142, 207, 247, 58, 250, 74, 13, 210, 124, 207, 88, 64, 85, 174, 8, 138, 169])

    private static func _xored(_ secret: [UInt8], salt: [UInt8]) -> String {
        return String(bytes: secret.enumerated().map { index, character in
            return character ^ salt[index % salt.count]
        }, encoding: .utf8) ?? ""
    }
}

Now, add this file to your project structure (and to .gitignore) and use it!

api.auth(key: Secret.apiKey, secret: Secret.apiSecret)

Note: The idea is that each developer would regenerate that file and not commit to the repository (however, you can use it however you want).

Why?

Let's face it - managing secret keys is not an easy task. We usually want:

  1. Protect ourselves against unwanted intruders that gain access to the repository (plain text is bad and so is e.g. symetric cryptography that only needs the attacker to either run the code to get the keys or calculate the secret by hand)
  2. Protect ourselves against unwanted access to binary through e.g. jailbreak (e.g. in iOS the binary will hold plain text keys even if you ignored them in git, storing them in .xcconfig makes it even easier to the attacker)
  3. The secret management to be as simple as possible.

While writing this tool there was nothing that I found that helped with all of the above.

pouch will make sure that static analysis tools will not be able to get to the keys easily. Though, for your own good, do not commit this file to the repository.

Configuration options

The config is in YAML format. By default the tool will look for .pouch.yml file, but you can provide a custom file path as a parameter:

pouch retrieve --config ./.custom.pouch.yml

For the config itself, you are required to have at least one secret and one output:

secrets:
- API_KEY
outputs:
- ./Secrets.swift

Though, there are also custom properties you can set.

Generated type name

You can change the generated type name (it's Secrets by default):

secrets:
- API_KEY
outputs:
- filePath: ./Constants.swift
  typeName: Constant

Generated secret name

You are also able to provide a custom generated name for a secret (otherwise it will do the camelCase):

secrets:
- name: API_KEY
  generatedName: youtubeApiKey
- API_SECRET
outputs:
- ./Secrets.swift

There are also things like custom inputs, but for now we only support environment variables.

Installing

You can either build & install it by using my Homebrew tap:

brew install sunshinejr/formulae/pouch

or by cloning the repo and using Make:

make install

Contributing

This project is at its early stage and it currently only supports xor with random salt & only Swift output, but I'm open to:

  • Adding new ciphers (ideally something that works on all characters, e.g. Caesar is great but shifting might be problematic for things like emoji)
  • Adding new cipher options (e.g. salt length)
  • Adding new outputs (e.g. Kotlin, though I'd love to add only things that would be quite useful, not just a PoC)

Notes about security

While this is for sure an improvement to your normal, plain-text based flow, this doesn't guarantee that your keys won't be reverse-engineered. If you want to learn more about secret management and it's security, I recomend you to read the whole article I linked at the top of the Readme: NSHipster article regarding secret management

Kudos

License

Mit