Architecture Overview

Open Sesame is a trust-scoped secret and identity fabric for Linux, built as 21 Rust crates organized into a Cargo workspace. The system runs as seven cooperating daemons under systemd, communicating over a Noise IK encrypted IPC bus. Two Debian packages partition the daemons into a headless core suitable for servers, containers, and VMs, and a desktop layer that requires a Wayland compositor.

Crate Topology

The workspace (Cargo.toml:2-26) contains 21 crates in five layers: memory and cryptographic foundations, shared abstractions, platform bindings, daemon binaries, and the extension system.

Foundation Layer

Abstraction Layer

Platform Layer

Daemon Layer

Orchestration and Extension Layer

Daemon Model

The seven daemons are split across two systemd targets and two Debian packages.

Headless Daemons (package: open-sesame)

These four daemons have no GUI dependencies and run on any system with systemd: bare-metal servers, containers, VMs, and desktops alike.

Desktop Daemons (package: open-sesame-desktop)

These three daemons require a COSMIC or Wayland compositor. The open-sesame-desktop package depends on open-sesame, so installing it pulls in all headless daemons automatically.

Headless/Desktop Split Rationale

The split exists so that secret management, application launching, and snippet expansion can run on headless infrastructure (CI runners, jump hosts, fleet nodes) without pulling in Wayland, GTK, or GPU dependencies. A server running only open-sesame gets encrypted vaults, profile-scoped secrets, and environment injection (sesame env -p work -- aws s3 ls) with no graphical stack. A developer workstation installs open-sesame-desktop for the full experience: window switching, clipboard history, and keyboard shortcuts layered on top of the same headless core.

IPC Bus

All inter-daemon communication flows through a Noise IK encrypted IPC bus implemented in core-ipc.

Hub-and-Spoke Topology

daemon-profile hosts the BusServer. Every other daemon and every sesame CLI invocation connects as a BusClient. There is no peer-to-peer communication between daemons; all messages route through the hub.

Noise IK Transport

The IPC bus uses the Noise IK handshake pattern from the snow crate (Cargo.toml:89). In the IK pattern the initiator (client) knows the responder’s (server’s) static public key before the handshake begins. This provides mutual authentication and forward secrecy on every connection. Messages are framed with postcard (Cargo.toml:65) for compact binary serialization and deserialized into core-types::EventKind variants.

Ephemeral CLI Connections

The sesame CLI binary does not maintain a long-lived connection. Each CLI invocation opens a Noise IK session to daemon-profile, sends one or more EventKind messages, receives the response, and disconnects. The CLI has no persistent state and can be invoked from scripts, cron jobs, or CI pipelines without session management.

Message Flow Example

A sesame secret get -p work aws-access-key invocation follows this path:

1. sesame CLI opens a Noise IK session to daemon-profile.
2. daemon-profile authenticates the client and routes the secret-get request to daemon-secrets.
3. daemon-secrets verifies the caller’s clearance against the vault ACL, decrypts the value from the SQLCipher store, and returns it as a SensitiveBytes payload.
4. daemon-profile forwards the response to the CLI.
5. The CLI writes the secret to stdout and exits.

All secret material in transit is encrypted by the Noise session. All secret material at rest in daemon memory is held in ProtectedAlloc pages backed by memfd_secret(2) (see Memory Protection).

Daemon Topology

graph TD
    subgraph "open-sesame (headless)"
        DP[daemon-profile<br/><i>IPC bus host, profiles</i>]
        DS[daemon-secrets<br/><i>vault broker</i>]
        DL[daemon-launcher<br/><i>app launch, frecency</i>]
        DN[daemon-snippets<br/><i>snippet expansion</i>]
    end

    subgraph "open-sesame-desktop (GUI)"
        DW[daemon-wm<br/><i>window switcher overlay</i>]
        DC[daemon-clipboard<br/><i>clipboard history</i>]
        DI[daemon-input<br/><i>keyboard capture</i>]
    end

    CLI[sesame CLI<br/><i>ephemeral connections</i>]

    DS -->|BusClient| DP
    DL -->|BusClient| DP
    DN -->|BusClient| DP
    DW -->|BusClient| DP
    DC -->|BusClient| DP
    DI -->|BusClient| DP
    CLI -.->|ephemeral BusClient| DP

    subgraph "Foundation Crates"
        CM[core-memory]
        CC[core-crypto]
        CT[core-types]
        CI[core-ipc]
        CF[core-config]
        CZ[core-fuzzy]
        CSE[core-secrets]
        CP[core-profile]
        CA[core-auth]
    end

    subgraph "Platform Crates"
        PL[platform-linux]
    end

    subgraph "Extension System"
        EH[extension-host]
        ES[extension-sdk]
    end

    DP --> CI
    DP --> CP
    DP --> CF
    DP --> CT
    DS --> CSE
    DS --> CC
    DS --> CM
    DL --> CZ
    DL --> CF
    DW --> PL
    DC --> PL
    DI --> PL
    CI --> CT
    CI --> CM
    CC --> CM
    CSE --> CC
    CA --> CC
    EH --> ES

Crate Dependency Highlights

• Every daemon depends on core-ipc (for bus connectivity) and core-types (for the EventKind protocol schema).
• core-ipc depends on core-memory because Noise session keys are held in ProtectedAlloc.
• core-crypto depends on core-memory because SecureBytes wraps ProtectedAlloc for key material.
• The three desktop daemons (daemon-wm, daemon-clipboard, daemon-input) depend on platform-linux for Wayland protocol bindings, evdev access, and compositor integration.
• core-secrets depends on core-crypto for vault encryption and core-auth depends on core-crypto for key derivation during authentication.
• The extension-host crate uses wasmtime (Cargo.toml:164) with the component model and pooling allocator for sandboxed WASM extension execution.

Security Boundaries

Each daemon runs as a separate systemd service with:

• Landlock filesystem restrictions (platform-linux, landlock crate at Cargo.toml:136) limiting each daemon to only the filesystem paths it needs.
• seccomp syscall filtering (platform-linux, libseccomp crate at Cargo.toml:137) restricting each daemon to a minimal syscall allowlist.
• Noise IK mutual authentication on every IPC connection, preventing unauthorized processes from joining the bus.
• ProtectedAlloc secure memory for all key material, with memfd_secret(2) removing secret pages from the kernel direct map (see Memory Protection).

See Also

• Memory Protection – secure memory allocator internals
• IPC Protocol – Noise IK handshake, framing, and message schema
• Sandbox Model – Landlock and seccomp configuration
• Profile Trust Model – profile isolation contracts