3 files changed, 110 insertions, 0 deletions
diff --git a/types/key/node.go b/types/key/node.go
index c83aba15a..bf7088c3d 100644
--- a/types/key/node.go
+++ b/types/key/node.go
@@ -307,3 +307,10 @@ func (k NodePublic) WireGuardGoString() string {
 	b[second+3] = b64((k.k[31] << 2) & 63)
 	return string(b)
 }
+
+// AsNodeKey returns k converted to a NodeKey.
+//
+// Cross-compatibility shim as part of #3206.
+func (k NodePublic) AsNodeKey() NodeKey {
+	return k.Raw32()
+}
diff --git a/types/key/node_legacy.go b/types/key/node_legacy.go
new file mode 100644
index 000000000..7fc1944cf
--- /dev/null
+++ b/types/key/node_legacy.go
@@ -0,0 +1,28 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package key
+
+import (
+	"go4.org/mem"
+)
+
+// NodeKey is the legacy form of NodePublic.
+// See #3206 for removal effort.
+type NodeKey [32]byte
+
+func (k NodeKey) ShortString() string          { return k.AsNodePublic().ShortString() }
+func (k NodeKey) String() string               { return k.AsNodePublic().String() }
+func (k NodeKey) MarshalText() ([]byte, error) { return k.AsNodePublic().MarshalText() }
+func (k NodeKey) AsNodePublic() NodePublic     { return NodePublicFromRaw32(mem.B(k[:])) }
+func (k NodeKey) IsZero() bool                 { return k == NodeKey{} }
+
+func (k *NodeKey) UnmarshalText(text []byte) error {
+	var nk NodePublic
+	if err := nk.UnmarshalText(text); err != nil {
+		return err
+	}
+	*k = nk.AsNodeKey()
+	return nil
+}
diff --git a/types/key/node_legacy_test.go b/types/key/node_legacy_test.go
new file mode 100644
index 000000000..e70143b10
--- /dev/null
+++ b/types/key/node_legacy_test.go
@@ -0,0 +1,75 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package key
+
+import (
+	"bytes"
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestNodeKeyMarshal(t *testing.T) {
+	var k1, k2 NodeKey
+	for i := range k1 {
+		k1[i] = byte(i)
+	}
+
+	const prefix = "nodekey:"
+	got, err := k1.MarshalText()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := k2.UnmarshalText(got); err != nil {
+		t.Fatal(err)
+	}
+	if s := k1.String(); string(got) != s {
+		t.Errorf("MarshalText = %q != String %q", got, s)
+	}
+	if !strings.HasPrefix(string(got), prefix) {
+		t.Errorf("%q didn't start with prefix %q", got, prefix)
+	}
+	if k2 != k1 {
+		t.Errorf("mismatch after unmarshal")
+	}
+}
+
+func TestNodeKeyRoundTrip(t *testing.T) {
+	serialized := `{
+      "Pub":"nodekey:50d20b455ecf12bc453f83c2cfdb2a24925d06cf2598dcaa54e91af82ce9f765"
+    }`
+
+	// Carefully check that the expected serialized data decodes and
+	// re-encodes to the expected keys. These types are serialized to
+	// disk all over the place and need to be stable.
+	pub := NodeKey{
+		0x50, 0xd2, 0xb, 0x45, 0x5e, 0xcf, 0x12, 0xbc, 0x45, 0x3f, 0x83,
+		0xc2, 0xcf, 0xdb, 0x2a, 0x24, 0x92, 0x5d, 0x6, 0xcf, 0x25, 0x98,
+		0xdc, 0xaa, 0x54, 0xe9, 0x1a, 0xf8, 0x2c, 0xe9, 0xf7, 0x65,
+	}
+
+	type key struct {
+		Pub NodeKey
+	}
+
+	var a key
+	if err := json.Unmarshal([]byte(serialized), &a); err != nil {
+		t.Fatal(err)
+	}
+	if a.Pub != pub {
+		t.Errorf("wrong deserialization of public key, got %#v want %#v", a.Pub, pub)
+	}
+
+	bs, err := json.MarshalIndent(a, "", "  ")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var b bytes.Buffer
+	json.Indent(&b, []byte(serialized), "", "  ")
+	if got, want := string(bs), b.String(); got != want {
+		t.Error("json serialization doesn't roundtrip")
+	}
+}