Rack state re-pins rollcall.ca in stored boot entries

Commission, deploy and stateless entries are stored with the root's
fingerprint of the moment; after a rotation switch a machine booting
from one refused its rack. The state now writes the root the rack serves.
Found in the lab rotation (node002's entry on pxe-rack2).

Refs #12

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

cmd/rollcall/carot.go

@@ -33,6 +33,7 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"sync"
 	"time"
@@ -671,3 +672,8 @@ func (r *rackd) stageBundle(t *rackTrustState, trust []*x509.Certificate) error
 	}
 	return writeAtomic(filepath.Join(dir, "ca-ready"), []byte("1\n"), 0o644)
 }
+
+var caWordRe = regexp.MustCompile(`\brollcall\.ca=[0-9a-fA-F]{64}\b`)
+
+// pinCA points the rollcall.ca= words of a boot entry at the root fp.
+func pinCA(entry, fp string) string { return caWordRe.ReplaceAllString(entry, "rollcall.ca="+fp) }

cmd/rollcall/carot_test.go

@@ -176,3 +176,15 @@ func TestCARefreshScript(t *testing.T) {
 		t.Fatal("shQuote")
 	}
 }
+
+func TestPinCA(t *testing.T) {
+	old, nw := strings.Repeat("7e", 32), strings.Repeat("a1", 32)
+	in := "LABEL deploy\n  APPEND initrd=x rollcall.tls=https://10.213.78.1 rollcall.ca=" + old + " quiet\n  APPEND rollcall.ca=" + old + "\n"
+	got := pinCA(in, nw)
+	if strings.Contains(got, old) || strings.Count(got, "rollcall.ca="+nw) != 2 || !strings.Contains(got, "rollcall.tls=https://10.213.78.1 rollcall.ca="+nw+" quiet") {
+		t.Fatalf("%q", got)
+	}
+	if pinCA("APPEND rollcall.server=x", nw) != "APPEND rollcall.server=x" {
+		t.Fatal("changed an entry without rollcall.ca")
+	}
+}

cmd/rollcall/rackctl.go

@@ -15,6 +15,7 @@ package main
 import (
 	"context"
 	"crypto/subtle"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -488,6 +489,12 @@ func (a *App) rackState(ctx context.Context, name string) (*rackState, error) {
 	if st.PXE, err = a.store.PXEFiles(ctx, name); err != nil {
 		return nil, err
 	}
+	if a.ca != nil { // entries keep the root they were written with; a rotation moves it
+		fp := certFingerprint(a.serverCAFor(base))
+		for k, v := range st.PXE {
+			st.PXE[k] = pinCA(v, hex.EncodeToString(fp[:]))
+		}
+	}
 	subnets, err := a.store.Subnets(ctx)
 	if err != nil {
 		return nil, err