diff --git a/swarm-secret-client/src/policy.rs b/swarm-secret-client/src/policy.rs index 4144bcc9..b0b4fed5 100644 --- a/swarm-secret-client/src/policy.rs +++ b/swarm-secret-client/src/policy.rs @@ -186,6 +186,46 @@ pub fn render_agent(agent: &str) -> Result { ))) } +/// Render `agent`'s policy document: read on that one agent's credentials and +/// on the hive's shared queue credential. +/// +/// Extends [`render_agent`] with a second stanza granting read on +/// `swarm/hives//queue/agent`. The queue credential is **hive-shared, +/// not per-agent** — every agent in a hive authenticates to the queue with the +/// same client secret (`queue.rs:1-8`), so a policy scoped strictly to +/// `agents//*` cannot read it and an in-container pull would fail. That +/// hive-shared credential is already handed to every agent container on that +/// hive by the host today, so this grant adds no new authority — it merely +/// makes the existing capability reachable through the agent's own token +/// instead of requiring the credential to be delivered out of band. +/// +/// ⚠️ **Every agent in a hive can read that hive's queue credential.** This is +/// not new authority (the host already provides this exact value to all agents +/// on the hive), but it is a documented property: an agent policy grants read +/// on a path shared across every agent on its hive, not on a path unique to +/// that agent alone. +/// +/// Read-only, for the same reason [`render_agent`]'s is: an agent that could +/// write credentials could hand itself an identity it was never issued. +/// +/// # Errors +/// [`Error::PathSegment`] when `agent` or `hive` holds anything but +/// `[A-Za-z0-9_-]` — both are interpolated into policy paths, so a name that +/// could close a stanza could grant itself anything. +pub fn render_agent_with_queue(agent: &str, hive: &str) -> Result { + checked_segment("agent", agent)?; + checked_segment("hive", hive)?; + let agent_stanza = read_stanza(&format!( + "{MOUNT}/data/{ROOT}/{}/{agent}/*", + <&str>::from(Kind::Agent) + )); + let queue_stanza = read_stanza(&format!( + "{MOUNT}/data/{ROOT}/{}/{hive}/queue/agent", + <&str>::from(Kind::Hive) + )); + Ok(format!("{agent_stanza}{queue_stanza}")) +} + #[cfg(test)] mod tests { use super::*; @@ -408,4 +448,95 @@ mod tests { // consistent with it. assert!(hive.contains("path \"secret/data/swarm/agents/*\"")); } + + #[test] + fn an_agents_document_with_queue_grants_both_paths() { + // The happy path: the document grants read on the agent's own namespace + // and on the hive's queue credential. + let p = render_agent_with_queue("atlas", "pr1ma").expect("legal"); + assert!( + p.contains("path \"secret/data/swarm/agents/atlas/*\""), + "must grant the agent's own path: {p}" + ); + assert!( + p.contains("path \"secret/data/swarm/hives/pr1ma/queue/agent\""), + "must grant the hive's queue credential: {p}" + ); + assert_eq!( + p.matches("path \"").count(), + 2, + "two stanzas, one for the agent and one for the queue: {p}" + ); + } + + #[test] + fn an_agents_document_with_queue_is_read_only() { + // An agent that could write the queue credential could hand every agent + // on its hive an identity they were never issued. + let p = render_agent_with_queue("atlas", "pr1ma").expect("legal"); + for capability in ["create", "update", "delete", "list", "sudo", "patch"] { + assert!(!p.contains(capability), "must not grant {capability}: {p}"); + } + assert!(p.contains("capabilities = [\"read\"]")); + } + + #[test] + fn an_agent_name_with_traversal_in_the_queue_variant_is_refused() { + // The agent parameter is an injection surface in both renderers, so + // refusing a traversal here proves the new one validates it. + assert!( + render_agent_with_queue("atlas/*\" { capabilities = [\"root\"] }", "pr1ma").is_err() + ); + assert!(render_agent_with_queue("", "pr1ma").is_err()); + // The control: legal names still work. + assert!(render_agent_with_queue("a-b_C9", "pr1ma").is_ok()); + } + + #[test] + fn a_hive_name_with_traversal_in_the_queue_variant_is_refused() { + // The hive parameter is a second injection surface that only the queue + // variant introduces, so this test proves that new parameter is + // validated. A name that could close the stanza could grant the agent + // anything. + assert!( + render_agent_with_queue("atlas", "pr1ma/*\" { capabilities = [\"root\"] }").is_err() + ); + assert!(render_agent_with_queue("atlas", "").is_err()); + assert!( + render_agent_with_queue("atlas", "../services/swarm-grafana").is_err(), + "a path traversal that could reach a different kind" + ); + // The control: legal names still work. + assert!(render_agent_with_queue("atlas", "a-b_C9").is_ok()); + } + + #[test] + fn the_queue_variant_does_not_widen_the_agent_stanza() { + // The queue grant must not cause the agent stanza to widen from + // `agents//*` to `agents/*` — that would give every agent every + // other agent's credentials. + let p = render_agent_with_queue("atlas", "pr1ma").expect("legal"); + assert!( + !p.contains("swarm/agents/*"), + "must not grant the whole agent prefix: {p}" + ); + assert!(p.contains("swarm/agents/atlas/*")); + } + + #[test] + fn the_queue_variant_does_not_grant_the_whole_hive_prefix() { + // The queue stanza must grant only the queue credential path, not + // `hives//*` — the latter would give the agent read on every + // secret of the hive that hosts it. + let p = render_agent_with_queue("atlas", "pr1ma").expect("legal"); + assert!( + !p.contains("swarm/hives/*"), + "must not grant the whole hive prefix: {p}" + ); + assert!( + !p.contains("swarm/hives/pr1ma/*"), + "must not grant the hive's whole path: {p}" + ); + assert!(p.contains("swarm/hives/pr1ma/queue/agent")); + } }