Keep the machine's forge SSH key and its keys entry (issue 955 S1)

2026-10-16 22:43:18 +02:00
parent 017b729bc9
commit b2009f1bb5
5 changed files with 281 additions and 1 deletions
@@ -0,0 +1,140 @@
+package main
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Issue 955, area S1: the key the machine's account makes for the forge, and its entry in the keys state.
+
+type fakeState struct{ puts map[string][]byte }
+
+func (f *fakeState) Put(key string, value any) error {
+	raw, _ := json.Marshal(value)
+	if f.puts == nil {
+		f.puts = map[string][]byte{}
+	}
+	f.puts[key] = raw
+	return nil
+}
+
+// ed25519Line is a public key line with a well-formed ed25519 blob.
+func ed25519Line(seed byte, comment string) string {
+	blob := []byte{}
+	for _, part := range [][]byte{[]byte("ssh-ed25519"), make([]byte, 32)} {
+		part2 := append([]byte(nil), part...)
+		if len(part2) == 32 {
+			part2[0] = seed
+		}
+		l := make([]byte, 4)
+		binary.BigEndian.PutUint32(l, uint32(len(part2)))
+		blob = append(append(blob, l...), part2...)
+	}
+	return "ssh-ed25519 " + base64.StdEncoding.EncodeToString(blob) + " " + comment
+}
+
+// keygenRunner stands in for ssh-keygen -t ed25519: it writes the pair the command names.
+func keygenRunner(calls *[][]string) Runner {
+	return func(ctx context.Context, env []string, name string, args ...string) Ran {
+		*calls = append(*calls, append([]string{name}, args...))
+		var file, comment string
+		for i, a := range args {
+			switch a {
+			case "-f":
+				file = args[i+1]
+			case "-C":
+				comment = args[i+1]
+			}
+		}
+		if name != "ssh-keygen" || file == "" {
+			return Ran{Status: 1, Stderr: "unexpected"}
+		}
+		os.WriteFile(file, []byte("-----BEGIN OPENSSH PRIVATE KEY-----\nPRIVATE-SECRET\n"), 0o600)
+		os.WriteFile(file+".pub", []byte(ed25519Line(7, comment)+"\n"), 0o644)
+		return Ran{}
+	}
+}
+
+func newKeeper(t *testing.T, home string, st *fakeState, calls *[][]string) *KeyKeeper {
+	return &KeyKeeper{Home: home, Node: "g14", Account: "nox", Run: keygenRunner(calls), State: st,
+		Now: func() time.Time { return time.Date(2026, 10, 16, 12, 0, 0, 0, time.UTC) }}
+}
+
+func TestKeeperMakesTheKeyAndWritesItsEntry(t *testing.T) {
+	home := t.TempDir()
+	st, calls := &fakeState{}, &[][]string{}
+	if err := newKeeper(t, home, st, calls).Once(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+	raw, ok := st.puts["g14.nox"]
+	if !ok || len(st.puts) != 1 {
+		t.Fatalf("entries = %v, want one under g14.nox", st.puts)
+	}
+	var e map[string]string
+	json.Unmarshal(raw, &e)
+	if e["node"] != "g14" || e["account"] != "nox" || e["kind"] != "machine" || e["at"] != "2026-10-16T12:00:00Z" {
+		t.Errorf("entry = %v", e)
+	}
+	if !strings.HasPrefix(e["public"], "ssh-ed25519 ") || !strings.HasSuffix(e["public"], " nox@g14 (mesh)") {
+		t.Errorf("public = %q", e["public"])
+	}
+	if !strings.HasPrefix(e["fingerprint"], "SHA256:") {
+		t.Errorf("fingerprint = %q", e["fingerprint"])
+	}
+	if strings.Contains(strings.ToUpper(string(raw)), "PRIVATE") {
+		t.Errorf("the entry carries private material: %s", raw)
+	}
+	cmd := strings.Join((*calls)[0], " ")
+	for _, want := range []string{"-t ed25519", "-N ", "-C nox@g14 (mesh)", filepath.Join(home, ".ssh", "mesh_ed25519")} {
+		if !strings.Contains(cmd, want) {
+			t.Errorf("ssh-keygen call %q lacks %q", cmd, want)
+		}
+	}
+}
+
+func TestKeeperKeepsAnExistingKeyByteForByte(t *testing.T) {
+	home := t.TempDir()
+	os.MkdirAll(filepath.Join(home, ".ssh"), 0o700)
+	priv, pub := filepath.Join(home, ".ssh", "mesh_ed25519"), filepath.Join(home, ".ssh", "mesh_ed25519.pub")
+	os.WriteFile(priv, []byte("mine"), 0o600)
+	os.WriteFile(pub, []byte(ed25519Line(9, "nox@g14 (mesh)")+"\n"), 0o644)
+	st, calls := &fakeState{}, &[][]string{}
+	k := newKeeper(t, home, st, calls)
+	if err := k.Once(context.Background()); err != nil {
+		t.Fatal(err)
+	}
+	if len(*calls) != 0 {
+		t.Errorf("ssh-keygen ran over an existing key: %v", *calls)
+	}
+	if b, _ := os.ReadFile(priv); string(b) != "mine" {
+		t.Errorf("private file changed: %q", b)
+	}
+	if _, ok := st.puts["g14.nox"]; !ok {
+		t.Errorf("no entry for the existing key")
+	}
+	// A second round with nothing changed writes nothing.
+	delete(st.puts, "g14.nox")
+	k.Once(context.Background())
+	if len(st.puts) != 0 {
+		t.Errorf("an unchanged key was put again")
+	}
+}
+
+func TestKeeperNeverTouchesTheOperatorsOwnKeys(t *testing.T) {
+	home := t.TempDir()
+	os.MkdirAll(filepath.Join(home, ".ssh"), 0o700)
+	own := filepath.Join(home, ".ssh", "id_ed25519")
+	os.WriteFile(own, []byte("operator"), 0o600)
+	st, calls := &fakeState{}, &[][]string{}
+	newKeeper(t, home, st, calls).Once(context.Background())
+	if b, _ := os.ReadFile(own); string(b) != "operator" {
+		t.Errorf("the operator's key changed")
+	}
+}