BMC hints: the password stays on the region

GET /api/v1/bmc-hint answered with the BMC password to anyone with the
agent token (public on the PXE command line) and a MAC (visible on the
wire). It now returns the address and user only. When a machine reports
in, the region matches its MACs against bmc_hints itself, seals the
configured password into the record, and checks the BMC with a status
call from the rack controller (verified_oob). The agent skips its own
check when no password comes; old agents keep working.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

agent/rollcall-agent.py

@@ -416,7 +416,12 @@ def bmc_hint(server, macs):
     if not h or not h.get("address"):
         return None
     res = {"source": "hint", "address": h["address"], "port": h.get("port", 623),
-           "user": h.get("user"), "password": h.get("password"), "errors": []}
+           "user": h.get("user"), "errors": []}
+    if not h.get("password"):
+        # the region keeps the credentials and checks the BMC itself (rollcall >= 0.3)
+        res["configured"] = True
+        return res
+    res["password"] = h["password"]
     base = ["-I", "lanplus", "-H", h["address"], "-p", str(h.get("port", 623)), "-U", h.get("user", ""),
             "-P", h.get("password", "")]
     rc, mc = ipmi(base + ["mc", "info"], timeout=20)

cmd/rollcall/ipmi.go

@@ -114,6 +114,27 @@ func (s *Store) SetBMC(ctx context.Context, id string, bmc []byte, secret []byte
 // probeBMC: after commissioning, a BMC still on plain IPMI is asked whether it
 // speaks Redfish with the same account; if it does, the vendor's driver takes over.
 // An operator's explicit choice (driver_set) is left alone.
+// verifyHintedBMC runs a status call against a BMC from bmc_hints (the agent no
+// longer gets its password) and records whether it answered.
+func (a *App) verifyHintedBMC(m *Machine) {
+	var b obj
+	if m.BMC == nil || json.Unmarshal(m.BMC, &b) != nil || str(b["source"]) != "hint" || b["driver_set"] == true {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+	out, err := a.power(ctx, m, "status", "")
+	b["verified_oob"] = err == nil
+	if err != nil {
+		b["errors"] = []string{"hinted BMC did not answer: " + oneLine(err.Error())}
+	} else {
+		delete(b, "errors")
+	}
+	nb, _ := json.Marshal(b)
+	_ = a.store.SetBMC(ctx, m.ID, nb, nil)
+	_ = a.store.AddEvent(ctx, m.ID, "bmc hint", fmt.Sprintf("%s: %s", str(b["address"]), oneLine(orDefault(out, fmt.Sprint(err)))))
+}
+
 func (a *App) probeBMC(m *Machine) {
 	if m.BMC == nil || m.bmcSecret == nil {
 		return

cmd/rollcall/security_test.go

@@ -6,9 +6,11 @@ import (
 	"crypto/rand"
 	"crypto/tls"
 	"crypto/x509"
+	"encoding/json"
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 )
@@ -107,3 +109,18 @@ func TestIdentitiesOnlyFromTheRoot(t *testing.T) {
 		t.Error("an admin certificate passed as the region's")
 	}
 }
+
+// The hint API names the BMC but never hands out its password.
+func TestBMCHintHasNoPassword(t *testing.T) {
+	a := &App{cfg: &Config{BMCHints: []BMCHint{{MAC: "52:54:00:AA:BB:01", Address: "10.0.0.11", User: "admin", Password: "s3cret"}}}}
+	rec := httptest.NewRecorder()
+	a.handleHint(rec, httptest.NewRequest("GET", "/api/v1/bmc-hint?macs=02:00:00:00:00:09,52-54-00-aa-bb-01", nil))
+	var h map[string]any
+	_ = json.Unmarshal(rec.Body.Bytes(), &h)
+	if h["address"] != "10.0.0.11" || h["user"] != "admin" || h["password"] != nil || strings.Contains(rec.Body.String(), "s3cret") {
+		t.Errorf("hint %s", rec.Body.String())
+	}
+	if a.hintFor([]string{"../x", ""}) != nil {
+		t.Error("garbage matched a hint")
+	}
+}

cmd/rollcall/server.go

@@ -554,8 +554,28 @@ func (a *App) handleCommission(w http.ResponseWriter, r *http.Request) {
 	// Pull the BMC password out of the payload before anything is persisted.
 	var secret []byte
 	detail := "bmc=none"
+	if bmc, _ := inv["bmc"].(obj); bmc == nil || str(bmc["source"]) == "hint" || str(bmc["address"]) == "" {
+		// a configured out-of-band BMC: the region's credentials, whatever the agent sent
+		if h := a.hintFor(macs); h != nil {
+			port := h.Port
+			if port == 0 {
+				port = 623
+			}
+			nb := obj{"source": "hint", "address": h.Address, "port": port, "user": h.User, "configured": true, "password": "<from bmc_hints>"}
+			if bmc != nil {
+				nb["agent"] = obj{"source": bmc["source"], "errors": bmc["errors"]}
+			}
+			inv["bmc"] = nb
+			if h.Password != "" {
+				if secret, err = a.sealer.Seal(h.Password, m.ID); err != nil {
+					fail(w, 500, err)
+					return
+				}
+			}
+		}
+	}
 	if bmc, ok := inv["bmc"].(obj); ok {
-		if pw := str(bmc["password"]); pw != "" {
+		if pw := str(bmc["password"]); pw != "" && str(bmc["source"]) != "hint" {
 			secret, err = a.sealer.Seal(pw, m.ID)
 			if err != nil {
 				fail(w, 500, err)
@@ -603,9 +623,15 @@ func (a *App) handleCommission(w http.ResponseWriter, r *http.Request) {
 	if isNew || oldErr != nil || old.State == "recommission" || old.RackController == "" {
 		_ = a.store.SetRackController(r.Context(), m.ID, a.fromRack(r)) // a ready machine is not moved by whoever reports it
 	}
-	if full, err := a.store.Get(r.Context(), m.ID); err == nil {
+	go func(id string) { // check a hinted BMC from where it is reachable, then look for Redfish
-		go a.probeBMC(full)
+		ctx := context.Background()
-	}
+		if full, err := a.store.Get(ctx, id); err == nil {
+			a.verifyHintedBMC(full)
+		}
+		if full, err := a.store.Get(ctx, id); err == nil {
+			a.probeBMC(full)
+		}
+	}(m.ID)
 	if full, err := a.store.Get(r.Context(), m.ID); err == nil {
 		m = full // carries profile / node token when this is a re-commission of a stateless node
 	}
@@ -623,22 +649,37 @@ func recommissionable(state string) bool {
 	return state == "new" || state == "ready" || state == "recommission" || strings.HasSuffix(state, "-failed")
 }
 
-func (a *App) handleHint(w http.ResponseWriter, r *http.Request) {
+// hintFor is the configured out-of-band BMC for one of these MACs.
+func (a *App) hintFor(macs []string) *BMCHint {
 	want := map[string]bool{}
-	for _, m := range strings.Split(r.URL.Query().Get("macs"), ",") {
+	for _, m := range macs {
-		want[normMAC(m)] = true
+		if n := normMAC(m); n != "" {
-	}
+			want[n] = true
-	for _, h := range a.cfg.BMCHints {
-		if want[normMAC(h.MAC)] {
-			port := h.Port
-			if port == 0 {
-				port = 623
-			}
-			writeJSON(w, 200, obj{"address": h.Address, "port": port, "user": h.User, "password": h.Password})
-			return
 		}
 	}
-	writeJSON(w, 200, obj{})
+	for i, h := range a.cfg.BMCHints {
+		if want[normMAC(h.MAC)] {
+			return &a.cfg.BMCHints[i]
+		}
+	}
+	return nil
+}
+
+// handleHint tells a commissioning agent that a BMC is configured for it: the
+// address, never the password (the agent token is public, MACs are visible on
+// the wire). The region attaches the credentials itself when the machine
+// reports in (handleCommission) and checks them from the rack controller.
+func (a *App) handleHint(w http.ResponseWriter, r *http.Request) {
+	h := a.hintFor(strings.Split(r.URL.Query().Get("macs"), ","))
+	if h == nil {
+		writeJSON(w, 200, obj{})
+		return
+	}
+	port := h.Port
+	if port == 0 {
+		port = 623
+	}
+	writeJSON(w, 200, obj{"address": h.Address, "port": port, "user": h.User, "credentials": "on the region"})
 }
 
 func (a *App) handleList(w http.ResponseWriter, r *http.Request) {