Crate secrecy

Secret wrapper type for more carefully handling secret values (e.g. passwords, cryptographic keys, access tokens or other credentials)

Goals

• Make secret access explicit and easy-to-audit via the ExposeSecret trait. This also makes secret values immutable which helps avoid making accidental copies (e.g. reallocating the backing buffer for a Vec)
• Prevent accidental leakage of secrets via channels like debug logging
• Ensure secrets are wiped from memory on drop securely (using the zeroize crate)

Presently this crate favors a simple, no_std-friendly, safe i.e. forbid(unsafe_code)-based implementation and does not provide more advanced memory protection mechanisms e.g. ones based on mlock(2)/mprotect(2). We may explore more advanced protection mechanisms in the future.

Box, String, and Vec wrappers

Most users of this crate will simply want Secret wrappers around Rust’s core collection types: i.e. Box, String, and Vec.

When the alloc feature of this crate is enabled (which it is by default), [SecretBox], [SecretString], and [SecretVec] type aliases are available.

There’s nothing particularly fancy about these: they’re just the simple composition of Secret<Box<_>>, Secret<String>, and Secret<Vec<_>>! However, in many cases they’re all you will need.

Advanced usage

If you are hitting limitations on what’s possible with the collection type wrappers, you’ll want to define your own newtype which lets you customize the implementation:

use secrecy::{CloneableSecret, DebugSecret, Secret, Zeroize};

#[derive(Clone)]
pub struct AccountNumber(String);

impl Zeroize for AccountNumber {
    fn zeroize(&mut self) {
        self.0.zeroize();
    }
}

/// Permits cloning
impl CloneableSecret for AccountNumber {}

/// Provides a `Debug` impl (by default `[[REDACTED]]`)
impl DebugSecret for AccountNumber {}

/// Use this alias when storing secret values
pub type SecretAccountNumber = Secret<AccountNumber>;

serde support

When the serde feature of this crate is enabled, the Secret type will receive a [Deserialize] impl for all Secret<T> types where T: DeserializeOwned. This allows loading secret values from data deserialized from serde (be careful to clean up any intermediate secrets when doing this, e.g. the unparsed input!)

To prevent exfiltration of secret values via serde, by default Secret<T> does not receive a corresponding [Serialize] impl. If you would like types of Secret<T> to be serializable with serde, you will need to impl the [SerializableSecret] marker trait on T.

Re-exports

• pub use zeroize;

Structs

• Secret
  Wrapper type for values that contains secrets, which attempts to limit accidental exposure and ensure secrets are wiped from memory when dropped. (e.g. passwords, cryptographic keys, access tokens or other credentials)

Traits

• CloneableSecret
  Marker trait for secrets which are allowed to be cloned
• DebugSecret
  Debugging trait which is specialized for handling secret values
• ExposeSecret
  Expose a reference to an inner secret
• Zeroize
  Trait for securely erasing values from memory.