117 lines
3.7 KiB
Markdown
117 lines
3.7 KiB
Markdown
# crypto-secret.cr
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[](https://github.com/didactic-drunk/crypto-secret.cr/actions/workflows/crystal.yml)
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[](https://github.com/didactic-drunk/crypto-secret.cr/releases)
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[](https://didactic-drunk.github.io/crypto-secret.cr/main)
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Secrets hold sensitive information
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The Secret interface manages limited time access to the secret and securely erasing the secret when no longer needed.
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Secret providers may implement additional protections via:
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* `#noaccess`, `#readonly` or `readwrite`.
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* Using [mprotect]() to control access
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* Encrypting the data when not in use
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* Deriving keys on demand from a HSM
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* Preventing the Secret from entering swap ([mlock]())
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* Preventing the Secret from entering core dumps
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* Other
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## Installation
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1. Add the dependency to your `shard.yml`:
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```yaml
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dependencies:
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crypto-secret:
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github: didactic-drunk/crypto-secret
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```
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2. Run `shards install`
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## Usage
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```crystal
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require "crypto-secret/not"
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not_secret = Crypto::Secret::Not.new 32
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not_secret.wipe do
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not_secret.readonly do |slice|
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# May only read slice
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end
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not_secret.readwrite do |slice|
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# May read or write to slice
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end
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end # Secret is erased
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```
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## What is a Secret?
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<strike>Secrets are Keys</strike>
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That's complicated and specific to the application. Some examples:
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* Passwords
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* A crypto key is always a Secret. Except when used for verification (sometimes)
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* A decrypted password vault (but it's not a Key)
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Not secrets:
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* Digest output. Except when used for key derivation, then it's a Secret, including the Digest state
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* IO::Memory or writing a file. Except when the file is a password vault, cryptocurrency wallet, encrypted mail/messages, goat porn, maybe normal porn, sometimes scat porn, occassionally furry, not vanilla porn
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## Why?
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The Secret interface is designed to handle varied levels of confidentiality with a unified API for cryptography libraries.
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There is no one size fits all solution. Different applications have different security requirements. Sometimes for the same algorithm.
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A master key (kgk) may reside on a HSM and generate subkeys on demand.
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Or for most applications the master key may use best effort protection using a combination of [guard pages, mlock, mprotect].
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Other keys in the same application may handle a high volume of messages where [guard pages, mlock, mprotect] overhead is too high.
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A key verifying a public key signature may not be Secret.
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## Implementing a new Secret holding class
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**Only intended for use by crypto library authors**
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```
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class MySecret
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include Crypto::Secret
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def initialize(size)
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# allocate storage
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# optionally mlock
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end
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def to_slice(& : Bytes -> Nil)
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# yield Slice.new(pointer, size)
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ensure
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# optionally reencrypt or signal HSM
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end
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def bytesize : Int32
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# return the size
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end
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# optionally override [noaccess, readonly, readwrite]
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# optionally override (almost) any other method with implementation specific version
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end
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```
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## Contributing
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**Open a discussion before creating PR's**
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1. Fork it (<https://github.com/your-github-user/crypto-secret/fork>)
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2. Create your feature branch (`git checkout -b my-new-feature`)
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3. Commit your changes (`git commit -am 'Add some feature'`)
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4. Push to the branch (`git push origin my-new-feature`)
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5. Create a new Pull Request
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## Contributors
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- [didactic-drunk](https://github.com/didactic-drunk) - current maintainer
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