Pulse/docs/AGENT_SECURITY.md

Agent Security

Pulse agents incorporate several security mechanisms to ensure that the code running on your infrastructure is authentic and untampered with.

Agent Privilege Model

Pulse's Linux/systemd installer runs the unified agent as root by default. That is intentional for full host telemetry: disk SMART data, mdadm/RAID state, temperature sensors, Docker or Podman socket reads, Proxmox host-local details that are not available through the API, and some NAS/platform integrations commonly require root or equivalent local privileges. Running the service as a lower-privilege user may work for a narrow subset of metrics, but it is not a supported full-telemetry profile today.

Treat a host agent like other infrastructure monitoring software with local root read access:

• install it only on hosts you trust Pulse to monitor;
• keep the agent token scoped to that Pulse server;
• keep command execution disabled unless you explicitly need governed remediation;
• update from signed release assets rather than arbitrary branch snapshots.

The agent is primarily an outbound reporter to your Pulse server. By default it binds the health and Prometheus endpoints to 127.0.0.1:9191, so a root agent does not expose that HTTP surface to the network unless you explicitly opt in. Set --health-addr :9191 only when you intentionally scrape the agent from another host. Use --health-addr "" or PULSE_HEALTH_ADDR=off to disable the listener.

Generated Linux/systemd units also include conservative sandboxing such as NoNewPrivileges=true, PrivateTmp=true, kernel/control-group write protection, a private umask, and setuid/personality restrictions. Those directives reduce service blast radius while keeping the filesystem and device access needed for full host telemetry, Proxmox token setup, SMART, Docker, and NAS integrations.

Command execution is disabled by default. It can be enabled with --enable-commands, PULSE_ENABLE_COMMANDS=true, or the centralized agent command setting after enrollment. Leave it disabled for read-only monitoring. When enabled, commands still flow through Pulse's command policy and approval surfaces instead of silently turning every agent into an unrestricted remote shell.

Agent command tokens must be bound to a host or agent identity before command registration is accepted. Proxmox install-command tokens are the only first-use exception: because the server mints them before the installer knows the final hostname, Pulse binds them to the first command agent that registers with that token. Generic unbound agent:exec tokens still fail closed.

Proxmox Deployment Choices

You do not need a Pulse agent on every Proxmox-related host just to see basic cluster inventory and utilization. Start with the least-privilege path that answers your monitoring question:

Goal	Recommended path	Root agent needed?
PVE/PBS/PMG inventory, node status, VM/container status, storage usage, and normal Proxmox API metrics	Add the Proxmox connection with a read-only or narrowly scoped API token	No
VM guest disk and memory details through QEMU Guest Agent	Use Proxmox API permissions such as VM.GuestAgent.Audit and VM.GuestAgent.FileRead where supported	No host agent for the Proxmox node
Docker/Podman containers inside a VM or LXC through guest-local reporting	Install the agent inside that VM/LXC with Docker/Podman monitoring enabled, or use another explicit guest access/reporting path	Usually requires root or Docker socket-equivalent access
Docker containers inside an LXC from a Proxmox host agent	Start Pulse with PULSE_ENABLE_PROXMOX_GUEST_DOCKER_INVENTORY=true; optionally limit guests with PULSE_PROXMOX_GUEST_DOCKER_INVENTORY_VMIDS=101,102	Requires a root/equivalent Pulse agent on the Proxmox node and explicit server opt-in
Host SMART, temperatures, local ZFS/Ceph/mdadm detail, arbitrary mount reads, and full host telemetry	Install the agent on that host	Yes, for the supported full-telemetry profile
Kubernetes node/pod monitoring from a cluster	Use the Kubernetes agent/DaemonSet profile	Depends on whether host metrics are enabled

Inside-guest runtime visibility is explicit. Installing the agent inside a VM or LXC authorizes that guest-local agent to report Docker/Podman monitoring data according to its local module flags. A Proxmox node agent does not look inside LXCs by default. It can collect Docker container inventory from LXC guests through pct exec, but only when the server is started with PULSE_ENABLE_PROXMOX_GUEST_DOCKER_INVENTORY=true. Inventory collection is disabled by default, can be VMID-allowlisted, and is limited to the Docker page summary path: Docker host/runtime version, container ID, name, image, state/status, ports, and aggregate docker stats counters. It does not run docker inspect and does not collect guest environment values, mount sources, container commands, files, or process details. The lighter socket-presence hint remains separately available through PULSE_ENABLE_PROXMOX_GUEST_DOCKER_DETECTION=true.

For VMs, a Proxmox host agent still cannot see Docker/Podman inventory without guest cooperation such as a guest-local Pulse agent, QEMU guest-agent mediated integration, SSH, or an explicitly exposed Docker/Podman reporting endpoint.

If Proxmox API data is enough for your use case, prefer API-only monitoring and do not install a host agent just because the installer exists. Install agents where you need data that Proxmox cannot provide through its API, or where the data lives inside a guest/container rather than at the Proxmox node layer. The Settings Proxmox setup flow uses this API inventory path as the default; the host telemetry agent path is for the full-telemetry cases above. Generated API Inventory setup still needs a one-time privileged shell on the Proxmox host so it can create the pulse-monitor account, token, and ACLs, but steady-state monitoring uses the Proxmox API rather than a root Pulse agent. For PVE, the generated script creates a privilege-separated API token and mirrors the generated read/monitoring ACLs onto both the service user and the token. For PBS, the generated script grants the Audit ACL to both the service user and token.

Running pulse-agent as a custom non-root systemd user is possible by editing the service unit, but it is not a supported full-telemetry mode today. Expect gaps in SMART, temperature, Docker socket, ZFS/Ceph/mdadm, mount, and platform integration data unless you deliberately grant equivalent capabilities or group access. If you choose that route, treat it as a local hardening profile and verify the exact metrics you care about after the change.

Supply-Chain Boundary

The agent self-update path is not just "download the latest binary and run it". Release builds require checksum validation, and when trusted update keys are embedded they also require an Ed25519 release signature before replacing the running binary.

The initial installer is different: if you paste and run a shell command as root, you are granting root to that installer at that moment. Prefer the release-pinned, signature-verified server installer flow documented in README.md and INSTALL.md, then use the agent install command generated by your own Pulse server.

For the server installer, avoid latest when you want a tighter change-control boundary. Download a specific release tag, verify the install.sh.sshsig signature, and pass that same tag to bash install.sh --version. Agent self-updates still verify checksum headers, and release builds require signatures when a trusted update key is embedded.

The first automatic hop from an already-installed v5 pulse-agent to v6 is performed by the v5 updater. That updater verifies TLS by default, requires the server-provided SHA-256 checksum, validates executable magic, enforces the size limit, and swaps atomically, but it does not yet have the v6 Ed25519 signature requirement or downloaded-binary --self-test. For that migration hop, use HTTPS or a trusted local network. In high-assurance environments, reinstall the v6 pulse-agent through the signed installer path instead of relying on the automatic v5-to-v6 first hop over plain HTTP.

Self-Update Security

The agent's self-update mechanism is critical for security and stability. To prevent supply chain attacks or compromised update servers from distributing malicious or broken agents, Pulse employs a rigorous verification process.

1. Checksum Verification

The agent verifies a SHA-256 checksum of the downloaded binary. The server must provide X-Checksum-Sha256; updates are rejected if the header is missing or mismatched.

2. Signature Verification

Release builds embed trusted Ed25519 update public keys and require X-Signature-Ed25519 in addition to the checksum header. Updates are rejected when the signature is missing or does not verify against the embedded trust root.

3. Pre-Flight Checks

To prevent "brick-updates"—bad updates that crash immediately and require manual recovery—agents perform pre-flight validation before replacing the running executable.

Unified agent (pulse-agent):

1. Download new binary.
2. Verify checksum (required).
3. Verify the Ed25519 release signature when trusted update keys are embedded.
4. Validate binary magic (ELF/Mach-O/PE) and size limits (100MB max).
5. Run the downloaded binary with --self-test, passing any live token through a short-lived 0600 token file rather than argv.
6. Make executable and swap atomically.

API Security

• Token Authentication: All agent-to-server communication requires a valid API token.
• TLS: Encrypted by default (unless specifically disabled).
• Network Isolation (optional): Agent check-in can be served on a dedicated, separately firewalled port that exposes only the agent-ingest routes (/api/agents/*), so a host that can reach the agent endpoint over an untrusted network cannot pivot to the web UI or management API. See Split-Port Agent Ingest.