Audiobuzz
a46e5edf69
The tracking.log read was still returning empty under enforcing with NO AVC —
the tell of a DAC (not SELinux) denial. Root cause: /var/log/chrony is mode
0750 chrony:chrony (others have no access), so the agent's DynamicUser (group
tss only) can't even traverse the directory to reach the 0644 tracking.log —
EACCES on open, which produces no audit record. Manager confirmed genuinely on
fleet-manager-1db3977 (chrony-capable), and uptime flowed while chrony didn't,
proving the agent was sending empty chrony (failed read), not a manager gap.
Earlier manual reads worked only as root (sudo) or because fleetadmin had been
usermod'd into chrony during the socket test (reverted on reboot — /etc/group
is on the volatile overlay).
Fix: SupplementaryGroups=tss chrony on the unit — the chrony group has r-x on
the 0750 dir so the agent can traverse it; the log file is world-readable. This
is the DAC half; the fleet_agent_chronylog SELinux module (02a6621) is the TE
half — BOTH are required (verified: group-only -> TE-denied; module-only ->
DAC-denied silently). Corrected the now-stale 'no group' code comment; recorded
the two-layer requirement in the .te and stig-deviations #16. Needs a
workstation image rebuild + reboot.
fleet-agent — on-host control-plane client (telemetry v1)
The workstation-side half of the fleet management plane. It dials the
fleet-manager agent plane, identifies with the host's TPM, and streams
health telemetry up. It is the client peer of the server hub in
serving/fleet-manager/ (agent.go + proto/fleet_agent.proto).
Baked into the immutable verity image, so — like fleet-hostapi and fleet-enrol
— it is a static, reproducible, CGO_ENABLED=0 Go binary built out of the
build VM by CI (deps proxy-fetched, go.sum-pinned) and file-provisioned in.
What it does (v1 — telemetry only)
- Reuses the TPM identity for mTLS. Loads the signing key at the persistent
handle (
0x81000100) as acrypto.Signer(tpmkey.LoadSigner— the private key never leaves the TPM) and the enrolment cert from NV (0x01800100), and presents them as the mTLS client cert. The manager verifies the chain to the fleet CA and derives the cert serial = inventory key — a host can only ever report as itself (agent.go:peerSerial). - Opens the long-lived
Sessionbidi stream (host dials out; no inbound host port — works across the OPNsense L3 hop from the host VLAN to the mgmt plane). - Sends
Hello(image version, kernel, kiosk URL, root hash, starship name — the fleet-generic facts, pulled fromfleet-hostapion127.0.0.1:9099). - Sends a
HealthSnapshoteveryFLEET_AGENT_INTERVAL— load/cpu/temp/mem/ tmpfs, nvme-root, 802.1X-macsec, selinux, chrony, kiosk-active — probed read-only from/proc+/sys(each probe degrades gracefully; a failure never kills the stream). - Receives
DesiredState/Commandand LOGS them. This build does not act on them. The reconcile actuators (apply kiosk URL, reboot, drain) are a deliberate follow-up (seedocs/TODO.md#14) — the receive path is wired now so adding them needs no protocol change.
A dropped stream is retried with jittered backoff; the manager treats stream loss as the host going offline.
Prerequisite: the host must already be enrolled
The manager rejects the stream (PermissionDenied) until an inventory record
exists for the host's cert serial — that record is born when an admin approves
the host's TPM enrolment (fleet-enrol → enrol-broker → manager). Enrolment
precedes the agent; this ordering is expected.
Config (/etc/fleet-agent/agent.env)
All values are fleet-generic (invariant #1). See the file for the full list:
FLEET_AGENT_MANAGER (manager host:port), FLEET_AGENT_CA (fleet root, reused
from /etc/dot1x/radius-ca.pem), FLEET_AGENT_HANDLE / FLEET_AGENT_NVINDEX (TPM
identity, mirror rd.dot1x.*), FLEET_AGENT_INTERVAL, FLEET_AGENT_HOSTAPI.
Layout
| file | purpose |
|---|---|
main.go |
config, connect loop (jittered backoff), Session send/recv |
identity.go |
TPM-backed mTLS client cert + fleet-CA-verifying tls.Config |
snapshot.go |
read-only /proc+/sys health probes + hostapi facts fetch |
tpmkey/ |
copy of files/enrol/tpmkey + read-only LoadSigner (see its header) |
proto/ |
copy of the generated fleet.agent.v1 package (one .proto contract, two peers) |
fleet-agent.service |
hardened unit (tss group for the TPM, INET egress) |
Build / test
cd files/agent
CGO_ENABLED=0 go build -trimpath -buildvcs=false -ldflags '-s -w -buildid=' -o bin/fleet-agent .
go test ./...
# TPM handshake end-to-end (go-tpm software simulator, CGO — isolated module):
( cd simtest && CGO_ENABLED=1 go test ./... )