theta-agent/README.md

Theta Agent

Theta Agent is a unified endpoint management daemon for the theta42 stack. It replaces legacy bash installation scripts and one-way metric scripts with a powerful, 2-way Command & Control (C2) Go daemon.

The agent dials out to the central SSO Manager via a persistent WebSocket connection, enabling real-time telemetry, dynamic discovery, and secure remote operations.

Core Functionality

1. Telemetry & Observability

• Host Discovery: Pushes a comprehensive profile (IPs, OS, Kernel, CPU, RAM/Disk) upon connection and automatically updates when network interface IPs change.
• Continuous Monitoring: Streams metrics every 30 seconds:
  • CPU, RAM, and Root Disk usage.
  • ZFS Health: Monitors pool status via zpool list.
  • GPU Utilization: Tracks NVIDIA GPU usage via nvidia-smi.
• Health Checks: Sends a periodic heartbeat to the SSO Manager to signal agent viability.

2. Remote Operations (C2)

The agent provides a powerful set of administrative tools, categorized by risk:

Standard Operations

• Config Reload: Triggers a reload of /etc/theta42/agent.yml from disk without restarting the process.
• Log Streaming: Fetch the last 100 lines of the agent's system logs via the C2 channel.

High-Risk Operations (Require Cryptographic Signatures)

To prevent unauthorized execution, these commands must be signed with a private key corresponding to the public_key in agent.yml:

• Service Control: Restart approved systemd services.
• System Control: Trigger a full system reboot.
• Config Management: Update /etc/sssd/sssd.conf and restart sssd.
• Remote Execution: Execute raw bash scripts.
• Self-Update: Securely download, verify (SHA256), and apply a new binary version.

The Security Model (Blast Radius & Zero-Trust)

Because Theta Agent runs as root, it is a high-value target. To prevent lateral movement and contain the blast radius, it operates on a strict, local-first capability matrix.

Local Configuration Wins

The agent will only execute commands that are explicitly enabled in its local configuration file (/etc/theta42/agent.yml). The central SSO Manager cannot override these settings.

Cryptographic Hardening

All high-risk commands require an Ed25519 signature. The agent verifies the signature against the public_key provided in the local config. If the signature is missing or invalid, the command is rejected regardless of the capability matrix.

Verification is fail-closed: an agent with no public_key configured rejects every high-risk command. (Before protocol v1.2.0 it logged "skipping signature verification" and executed them, so an agent installed without a key would run reboot, configure_ldap and arbitrary_bash unverified.)

Enrollment

The agent's token must be issued by the SSO. The server stores only its SHA-256 and rejects anything else at the WebSocket handshake, so a token cannot be minted client-side, and an enrollment can be revoked or rotated centrally — either drops the agent's live connection immediately. See PROTOCOL.md §1.1.

Capability Matrix

Capability	Risk Level	Description	Impact
telemetry	Safe	Read-only metrics.	Pushes system health to SSO Manager.
configure_ldap	Moderate	Configures SSSD.	Updates /etc/sssd/sssd.conf and restarts sssd.
reboot	High	System reboot.	Triggers an immediate host reboot.
service_control	High	Service management.	Restarts services listed in the allowed list.
arbitrary_bash	CRITICAL	Raw bash execution.	Executes any script sent by the manager as root.

Configuration

Configuration is stored in YAML format at /etc/theta42/agent.yml.

Example agent.yml

server_url: "wss://sso.theta42.local"
auth_token: "issued-by-the-sso-at-enrollment"
public_key: "base64-encoded-ed25519-public-key"
location: "dc-01-rack-12"
capabilities:
  telemetry: true
  configure_ldap: true
  reboot: true
  service_control: ["nginx", "gitea", "sssd"]
  arbitrary_bash: false

Installation

1. Build: Compile for your target architecture (see CI/CD artifacts).
2. Deploy: Place the binary in /usr/local/bin/theta-agent.
3. Enroll: In the SSO, open Directory → Install Agent, name the host, bind it to a host resource, and press Enroll & issue token. The SSO mints the token (shown once) and gives you its public key. Tokens the server did not issue are rejected.
4. Configure: Create /etc/theta42/agent.yml with the issued auth_token, the SSO's public_key, and your capabilities.
5. Service: Set up as a systemd unit (example: /etc/systemd/system/theta-agent.service).

For the fastest deployment, use the installation script:

curl -fsSL https://sso.example.com/resources/theta-agent/install.sh | sh -s -- "BASE64_ENCODED_CONFIG"

The Install Agent modal generates that command for you after enrollment, with the token and public key already embedded. The equivalent flag form is:

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

Development & Testing

The agent uses a decoupled execution engine for safety and testability.

• Run unit tests: go test -v ./...
• The test suite uses a MockExecutor to verify that system commands are only triggered when the corresponding capability is enabled in the configuration.