Enrolment hands out the broker CA, and now the PC keeps it

The server has always sent the broker's CA certificate in the enrolment
response, precisely so it never has to ship in an installer. Nothing on
the receiving end wrote it anywhere: the agent read the field under the
wrong name (ca_pem, the server says ca_cert) and the desktop app read it
correctly and dropped it. Every claimed PC therefore dialled
tls://mcp.loyaly.ai:8883 with the system trust store, the private CA
failed verification, and the agent reported 'the broker did not accept
this PC' - a TLS failure is indistinguishable from a refusal at that
layer. No real site could ever have published a visit.

Found by claiming this Mac as a real shop against production; fixed by
writing the CA to broker-ca.crt beside agent.json on both claim paths.
Verified: broker connected over TLS, camera pushed from head office,
engine streaming it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KGcjxF1cNLcuwc3DAPcnfj

.gitignore

@@ -65,3 +65,4 @@ node_modules/
 
 # Left behind by `pip install .` of the engine (setuptools metadata), not source.
 /behavision.egg-info/
+/.prod/

agent/main.go

@@ -119,6 +119,11 @@ func cmdClaim(args []string) error {
 	cfg.BrokerPassword = b.MQTTPass
 	cfg.AgentToken = b.AgentToken
 	cfg.CloudBase = base
+	caPath, err := enrol.SaveCA(b.CACert, paths.BrokerCA())
+	if err != nil {
+		return err
+	}
+	cfg.BrokerCAFile = caPath
 	// A PC that was running on its own and has now been linked is no longer
 	// standalone.
 	cfg.Standalone = false

agent/pkg/enrol/enrol.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 	"strings"
 	"time"
 )
@@ -31,7 +32,7 @@ type Bootstrap struct {
 	MQTTURL    string `json:"mqtt_url"`
 	MQTTUser   string `json:"mqtt_username"`
 	MQTTPass   string `json:"mqtt_password"`
-	CAPem      string `json:"ca_pem,omitempty"`
+	CACert     string `json:"ca_cert,omitempty"`
 	AgentToken string `json:"agent_token"`
 }
 
@@ -90,3 +91,23 @@ func Claim(ctx context.Context, base, code string) (Bootstrap, error) {
 	}
 	return out, nil
 }
+
+// SaveCA writes the broker's CA beside the agent config and returns its path.
+//
+// The server hands the CA out at enrolment precisely so it never has to be
+// shipped in an installer - and for a while nothing on the receiving end
+// wrote it anywhere. Every claimed PC then dialled tls://mcp.loyaly.ai:8883
+// with the system trust store, the private CA failed verification, and the
+// agent reported "the broker did not accept this PC" (a TLS failure is
+// indistinguishable from a refusal at that layer). No real site could ever
+// publish a visit. An empty CA returns "" so a deployment on a public
+// certificate keeps working unchanged.
+func SaveCA(pem, path string) (string, error) {
+	if strings.TrimSpace(pem) == "" {
+		return "", nil
+	}
+	if err := os.WriteFile(path, []byte(pem), 0o600); err != nil {
+		return "", fmt.Errorf("write broker CA: %w", err)
+	}
+	return path, nil
+}

agent/pkg/paths/paths.go

@@ -57,6 +57,9 @@ func InstallRoot() string {
 }
 
 func AgentConfig() string { return filepath.Join(StateRoot(), "agent.json") }
+
+// BrokerCA is the broker's CA certificate, written at enrolment.
+func BrokerCA() string  { return filepath.Join(StateRoot(), "broker-ca.crt") }
 func SpoolDir() string  { return filepath.Join(StateRoot(), "spool") }
 func EngineLog() string { return filepath.Join(StateRoot(), "engine.log") }
 

desktop/app.go

@@ -23,6 +23,7 @@ import (
 	agentcameras "github.com/loyaly/behavision-agent/pkg/cameras"
 	agentcfg "github.com/loyaly/behavision-agent/pkg/config"
 	agentengine "github.com/loyaly/behavision-agent/pkg/engine"
+	"github.com/loyaly/behavision-agent/pkg/enrol"
 	agentmqtt "github.com/loyaly/behavision-agent/pkg/mqtt"
 	agentpaths "github.com/loyaly/behavision-agent/pkg/paths"
 	agentspool "github.com/loyaly/behavision-agent/pkg/spool"
@@ -434,6 +435,11 @@ func (a *App) Claim(code string) (SessionInfo, error) {
 	a.cfg.BrokerPassword = b.MQTTPass
 	a.cfg.AgentToken = b.AgentToken
 	a.cfg.CloudBase = a.cloud.Base
+	caPath, err := enrol.SaveCA(b.CACert, agentpaths.BrokerCA())
+	if err != nil {
+		return SessionInfo{}, err
+	}
+	a.cfg.BrokerCAFile = caPath
 	// A PC that was running on its own and has now been linked is no longer
 	// standalone. Leaving the flag set would keep the head-office screens
 	// hidden on the one machine that just earned them.