tor-keymgr

Code to fetch, store, and update keys.

Overview

This crate is part of Arti, a project to implement Tor in Rust.

Likely to change

The APIs exposed by this crate (even without the keymgr feature) are new and are likely to change rapidly. We'll therefore often be making semver-breaking changes (and will update the crate version accordingly).

Key stores

The KeyMgr is an interface to one or more key stores. The key stores are types that implement the Keystore trait.

This crate provides the following key store implementations:

• Arti key store: an on-disk store that stores keys in OpenSSH format.
• (not yet implemented) C Tor key store: an on-disk store that is backwards-compatible with C Tor (new keys are stored in the format used by C Tor, and any existing keys are expected to be in this format too).

In the future we plan to also support HSM-based key stores.

Key specifiers and key types

The Keystore APIs expect a "key specifier" (specified for each supported key type via the KeySpecifier trait), and a KeyType.

A "key specifier" identifies a group of equivalent keys, each of a different type (algorithm). It is used to determine the path of the key within the key store (minus the extension).

KeyType represents the type of a key (e.g. "Ed25519 keypair"). KeyType::arti_extension specifies what file extension keys of that type are expected to have (when stored in an Arti store).

The KeySpecifier::arti_path and KeyType::arti_extension are joined to form the path of the key on disk (relative to the root dir of the key store). This enables the key stores to have multiple keys with the same role (i.e. the same KeySpecifier::arti_path), but different key types (i.e. different KeyType::arti_extensions).

KeySpecifier implementers must specify:

• arti_path: the location of the key in the Arti key store. This also serves as a unique identifier for a particular instance of a key.
• ctor_path: the location of the key in the C Tor key store (optional).

Feature flags

Additive features

(None yet.)

Experimental and unstable features

Note that the APIs enabled by these features are NOT covered by semantic versioning[^1] guarantees: we might break them or remove them between patch versions.

• keymgr -- build with full key manager support. Disabling this feature causes tor-keymgr to export a no-op, placeholder implementation.

[^1]: Remember, semantic versioning is what makes various cargo features work reliably. To be explicit: if you want cargo update to only make safe changes, then you cannot enable these features.