Bascule

Identity-aware SSH proxy for modern infrastructure.

Bascule is a lightweight SSH proxy that authenticates users via SSH keys or AI agent tokens, then connects them to a local shell, remote host, or ephemeral container. No agents. No control plane. One binary.

Quick Start

cargo build --release -p bascule-server
./target/release/bascule --config config/bascule.example.toml
# In another terminal:
ssh -p 2222 localhost

See docs/quickstart.md for Docker and container mode.

Session Modes

Mode	Config	Use case
Local PTY	(default)	Spawn a local shell
Remote proxy	[proxy]	Forward to a remote SSH host
Container	[container]	Ephemeral container per session

Container mode

Each SSH session spawns a fresh container. The image defines the toolset — if it's not in the image, the operator can't use it.

[container]
image = "bascule-shell:k8s-ops"
ephemeral = true
hardened = true
memory_limit = "512m"

Features

• Three backends — local PTY, remote SSH proxy, ephemeral containers
• Identity-aware sessions — every connection authenticated and attributed
• SSH key authentication — standard authorized_keys file
• AI agent authentication — Microsoft Entra Agent ID support (optional feature)
• Session limiting — configurable max concurrent sessions
• Right-sized images — curated container images (minimal, k8s-ops, net-ops, dev)
• SessionHandler trait — extend with custom policy, audit, or recording
• Structured logging — JSON format for production observability
• Small footprint — single binary, ~7MB, <64MB memory

Comparison

	Bascule	Teleport	Boundary
Agents	None	Required	Required
Control plane	None	Required	Required
License	Apache 2.0	AGPL	MPL
Container sessions	Native	No	No
AI Agent Identity	Native	No	No
Auth	SSH keys, Entra Agent ID	OIDC, SAML, GitHub	OIDC, LDAP
Binary size	~7MB	~150MB	~100MB

See docs/comparison.md for the full comparison.

Extending Bascule

Implement the SessionHandler trait to add custom behavior:

use bascule_core::hooks::{SessionHandler, SessionInfo};

struct MyAuditHandler;

#[async_trait]
impl SessionHandler for MyAuditHandler {
    async fn on_session_start(&self, session: &SessionInfo) -> anyhow::Result<()> {
        log::info!("{} connected from {}", session.principal, session.source_ip);
        Ok(())
    }

    async fn on_exec(&self, session: &SessionInfo, command: &str) -> anyhow::Result<()> {
        log::info!("{} executed: {}", session.principal, command);
        Ok(())
    }
}

Projects like Guildhouse use the SessionHandler trait to add custom authorization, audit logging, and session governance.

Documentation

• Quick Start
• Configuration
• Authentication
• Architecture
• Observability
• Comparison
• Container Images

Roadmap

• OIDC authentication (Keycloak, Entra, Okta, Google)
• Certificate-based authentication
• OpenTelemetry OTLP trace export
• Prometheus metrics endpoint
• Session recording
• Web UI for session management

License

Apache 2.0