sso-manager-node/docs/agents.md

layout, title, nav_order

layout	title	nav_order
default	Theta Agent & Endpoint Management	5

Theta Agent & Endpoint Management

The Theta Agent (theta-agent) is a unified, 2-way Command & Control (C2) endpoint management daemon written in Go for Linux hosts across your home lab, infrastructure, or data center. It connects outbound via a long-lived WebSocket connection to the central SSO Manager (wss://<sso-host>/api/agent/ws), enabling real-time host telemetry, automated host discovery, and local-first administrative management.

---

Enrollment (required)

An agent is only real if the SSO issued its token. Tokens the server did not issue are rejected at the WebSocket handshake.

Enroll from Directory → Install Agent:

1. Give the agent a name and, ideally, bind it to a host resource. The binding is what links telemetry, status and commands to a Directory entry.
2. Press Enroll & issue token. The SSO mints a 256-bit token, stores only its SHA-256, and shows the raw value once.
3. Copy the generated install command — it already carries the token and the server's public key.

Or via the API:

curl -X POST https://<SSO_HOST>/api/agent/enroll \
  -H "Authorization: Bearer <admin-api-token>" \
  -H 'Content-Type: application/json' \
  -d '{"name": "web01", "resourceId": "<host-resource-uuid>"}'

The response contains token (once only) and publicKey.

Endpoint	Purpose
GET /api/agent/nodes	Every enrolled agent, connected or not, plus the server public key
POST /api/agent/enroll	Mint an agent + token
PUT /api/agent/nodes/:id	Rename, or bind/unbind the host resource
POST /api/agent/nodes/:id/rotate	Issue a new token; the old one stops working immediately
POST /api/agent/nodes/:id/revoke	Disable the enrollment
DELETE /api/agent/nodes/:id	Remove the enrollment
POST /api/agent/nodes/:id/command	Send a command (signed automatically when high-risk)

Revoke, rotate and delete drop any live connection immediately — they do not wait for the agent to reconnect. Commands are addressed by agent id, never by token: a token is a credential and has no business in a URL or a log.

Enrollment, revocation, rotation, every command, and every rejected connection are written to the application log as structured "component":"agent" records with the acting user.

Lost the token? It cannot be recovered — only its hash is stored. Rotate the agent to issue a new one.

---

Core Functionality

1. Host Discovery & Inventory

Upon establishing a WebSocket connection, the agent immediately pushes a comprehensive discovery payload:

• Hostname & Network Interfaces: Hostname and all non-loopback IPv4 addresses and MACs.
• Operating System & Kernel: Linux distribution, platform, and kernel version.
• Hardware Specs: CPU model, total RAM (GB), and total root disk capacity (GB).
• Physical Location: Location identifier string (e.g. dc-01-rack-12) configured in agent.yml.

If the agent detects a network IP change, it automatically re-pushes an updated discovery payload to the SSO Manager.

2. Real-Time Telemetry Streaming

Every 30 seconds, the agent streams real-time performance metrics:

• CPU Load: System-wide CPU utilization percentage.
• Memory Utilization: RAM usage percentage and available memory.
• Disk Utilization: Root filesystem usage percentage.
• ZFS Storage Health: Health status of ZFS pools (e.g., ONLINE).
• NVIDIA GPU Load: GPU compute utilization percentage (via nvidia-smi).

---

Viewing in the SSO Manager

Agent status and telemetry live on the Directory page — there is no separate Agents page. For each host resource that has a connected theta-agent, the Directory shows a status dot in the row:

Color	Meaning
Green	Connected, healthy (CPU/RAM/disk within limits).
Yellow	Connected but under high load (CPU > 80% or RAM > 80% or disk > 90%).
Red	Enrolled but not connected. The agent exists and is expected — this is a fault.
Grey	No agent enrolled for this host, the enrollment is revoked, or the agent service is unreachable.

Red and grey used to be the same colour, which made an ordinary directory of hosts look like an outage. Because the enrollment now outlives the connection, "installed but down" is distinguishable from "never had an agent".

Opening a host's resource modal reveals a Metrics tab with the agent's live telemetry (CPU/RAM/disk/ZFS/GPU) and discovery info (OS, kernel, IPs, location).

An agent attaches to its host by its enrollment binding (resourceId), set when you enroll it or later via PUT /api/agent/nodes/:id. Agents enrolled without a binding fall back to matching their reported hostname against the resource name — the old behaviour, kept only as a fallback, because it silently failed whenever a Directory name differed from the machine's hostname and aliased two hosts that happened to share one.

Agent discovery feeds the Directory

A bound agent's discovery payload is written onto its host resource (os, kernel, cpu, ram_total_gb, disk_total_gb, ip), tagged with discovery_sources: ["theta-agent"] and an agentId back-reference. An agent runs on the host it describes, so it is the most authoritative source the directory has. An unbound agent goes through the normal discovery reconciler instead, matching like any other source.

---

Local-First Security & Capability Matrix

To protect hosts against unauthorized control, theta-agent enforces a strict, local-first capability matrix defined in /etc/theta42/agent.yml. Central SSO Manager requests are checked against local configuration before execution; permissions cannot be overridden remotely.

Capability	Config Key	Risk Level	Description & Impact
Telemetry	telemetry	Safe	Streams read-only system metrics (CPU, RAM, Disk, ZFS, GPU).
Configure LDAP	configure_ldap	Moderate	Writes updated SSSD configuration to /etc/sssd/sssd.conf & restarts sssd.
Service Control	service_control	High	Restarts systemd services listed in an explicit allowlist (e.g., ["nginx", "docker", "sssd"]).
Reboot	reboot	High	Triggers an immediate system reboot (systemctl reboot).
Arbitrary Bash	arbitrary_bash	Critical	Executes raw bash scripts sent from the SSO Manager as root (used for automated GitOps).

---

High-Risk Command Verification (Protocol v1.2.0)

High-risk management commands (reboot, service_restart, configure_ldap, arbitrary_bash, update_binary) are cryptographically verified using Ed25519 signatures:

1. The SSO Manager canonicalizes the command payload (sorted keys, no whitespace, no HTML escaping, signature omitted).
2. The payload is signed with the SSO Manager's Ed25519 private key.
3. The Base64 signature is appended to the message payload.
4. The agent verifies the signature against the configured public_key in /etc/theta42/agent.yml before executing the action.

The signing key is persistent. It lives in OpenBao at secret/agent/signing-key and survives restarts, so the public_key you pin in agent.yml keeps matching. (It used to be generated in memory at boot and changed on every restart, which made pinning impossible.) If the SSO cannot load or store a key it refuses to send high-risk commands rather than signing with one no agent has seen — GET /api/agent/nodes reports this as signingAvailable: false.

This requires the sso-broker OpenBao policy to grant secret/agent/*. Re-run ./setup.sh from theta-suite if you are upgrading.

Verification is fail-closed on the agent. An agent with no public_key configured rejects every high-risk command. Earlier versions logged "skipping signature verification" and executed them, so an agent installed without a key would run reboot, configure_ldap and arbitrary_bash unverified.

---

Installation & Deployment

Quick One-Liner Install

Run the following command as root on the target Linux host:

curl -fsSL https://<SSO_HOST>/resources/theta-agent/install.sh | sh -s -- \
  --url "https://<SSO_HOST>" --token "<ISSUED_TOKEN>" --public-key "<BASE64_PUBLIC_KEY>"

Both values come from enrollment. The Install Agent modal builds this line for you with them already filled in. Omitting --public-key leaves the agent able to report telemetry but unable to accept any high-risk command.

Custom Config Wizard

You can generate a Base64-encoded custom configuration using the Install Agent button on the Directory Management page in the SSO Manager UI:

curl -fsSL https://<SSO_HOST>/resources/theta-agent/install.sh | sh -s -- "<BASE64_ENCODED_CONFIG>"

---

Configuration File Example (/etc/theta42/agent.yml)

# /etc/theta42/agent.yml
server_url: "wss://sso.example.com"
# Issued by the SSO at enrollment. A token the server did not issue is rejected.
auth_token: "c8181ce0e55bf7302b11d719a7ae39adcd7604de461e6e363f8bb4fadf126acb"
location: "dc-01-rack-12"
# Base64 of the RAW 32-byte Ed25519 public key -- exactly the `publicKey` value
# from enrollment or GET /api/agent/nodes. Not a PEM body: a base64-decoded
# SPKI blob is 44 bytes, the agent requires 32, and it will refuse every signed
# command if this is wrong.
public_key: "D0cJB3iuStTzhXlu7tFDh/eEXFxRZwkuwQJJhFSqwlQ="

capabilities:
  telemetry: true
  configure_ldap: true
  reboot: false
  service_control: ["nginx", "docker", "sssd"]
  arbitrary_bash: false

---

Troubleshooting: agent is rejected (close 4001)

If the agent logs that the server rejected its token, the enrollment — not the network — is the problem. The SSO accepts the WebSocket upgrade and then closes with an application code:

Code	Meaning	Fix
4001	Token unknown, or never issued by this server	Enroll the host and put the issued token in agent.yml
4002	Superseded — another connection authenticated as this agent	Normal; two copies of the agent are running
4003	Enrollment revoked or deleted	Re-enroll
4004	Token rotated; agent.yml has the old value	Copy the new token

The agent backs off for 5 minutes on 4001/4003/4004 rather than retrying every 5 seconds — a credential that is wrong will not fix itself, and hammering the SSO only floods its audit log.

An agent installed before protocol v1.2.0 carries a token generated in the browser that the server never recorded, so it will be rejected with 4001 until re-enrolled.

---

Troubleshooting: agent can't connect (dial tcp ... i/o timeout)

If the agent host logs Dial error: dial tcp <ip>:443: i/o timeout while connecting to wss://<sso-host>/api/agent/ws, the WebSocket path is usually fine — this is a network/NAT problem, not an agent or SSO bug. A host behind the same NAT that owns the SSO often cannot reach its own public IP (no hairpin/loopback NAT on many home routers), so the TCP dial times out even though the same address works from outside.

Fix options:

1. Point agent.yml server_url at an address the host can reach directly — e.g. the SSO host's LAN IP (http://<lan-ip> or http://<lan-ip>:3001 for a no-TLS direct path).
2. Enable NAT reflection / hairpin NAT on the router so LAN hosts can reach their own public IP:443.
3. Add a local route/firewall rule on the agent host for its public IP.

Note: on a deployment where the theta42 proxy fronts sso.suite.example, make sure the proxy has a persistent Host record for the real SSO domain — not just the localtest.me placeholder — so routing survives a proxy restart (an in-memory lookup cache can mask a missing Redis record for up to ~1h).