create DB struct

This is step one in detaching the Database layer from Headscale (h). The
ultimate goal is to have all function that does database operations in
its own package, and keep the business logic and writing separate.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/util/key.go

@@ -0,0 +1,117 @@
+package util
+
+import (
+	"encoding/json"
+	"errors"
+	"regexp"
+	"strings"
+
+	"tailscale.com/types/key"
+)
+
+const (
+
+	// These constants are copied from the upstream tailscale.com/types/key
+	// library, because they are not exported.
+	// https://github.com/tailscale/tailscale/tree/main/types/key
+
+	// nodePublicHexPrefix is the prefix used to identify a
+	// hex-encoded node public key.
+	//
+	// This prefix is used in the control protocol, so cannot be
+	// changed.
+	nodePublicHexPrefix = "nodekey:"
+
+	// machinePublicHexPrefix is the prefix used to identify a
+	// hex-encoded machine public key.
+	//
+	// This prefix is used in the control protocol, so cannot be
+	// changed.
+	machinePublicHexPrefix = "mkey:"
+
+	// discoPublicHexPrefix is the prefix used to identify a
+	// hex-encoded disco public key.
+	//
+	// This prefix is used in the control protocol, so cannot be
+	// changed.
+	discoPublicHexPrefix = "discokey:"
+
+	// privateKey prefix.
+	privateHexPrefix = "privkey:"
+
+	PermissionFallback = 0o700
+
+	ZstdCompression = "zstd"
+)
+
+var (
+	NodePublicKeyRegex       = regexp.MustCompile("nodekey:[a-fA-F0-9]+")
+	ErrCannotDecryptResponse = errors.New("cannot decrypt response")
+)
+
+func MachinePublicKeyStripPrefix(machineKey key.MachinePublic) string {
+	return strings.TrimPrefix(machineKey.String(), machinePublicHexPrefix)
+}
+
+func NodePublicKeyStripPrefix(nodeKey key.NodePublic) string {
+	return strings.TrimPrefix(nodeKey.String(), nodePublicHexPrefix)
+}
+
+func DiscoPublicKeyStripPrefix(discoKey key.DiscoPublic) string {
+	return strings.TrimPrefix(discoKey.String(), discoPublicHexPrefix)
+}
+
+func MachinePublicKeyEnsurePrefix(machineKey string) string {
+	if !strings.HasPrefix(machineKey, machinePublicHexPrefix) {
+		return machinePublicHexPrefix + machineKey
+	}
+
+	return machineKey
+}
+
+func NodePublicKeyEnsurePrefix(nodeKey string) string {
+	if !strings.HasPrefix(nodeKey, nodePublicHexPrefix) {
+		return nodePublicHexPrefix + nodeKey
+	}
+
+	return nodeKey
+}
+
+func DiscoPublicKeyEnsurePrefix(discoKey string) string {
+	if !strings.HasPrefix(discoKey, discoPublicHexPrefix) {
+		return discoPublicHexPrefix + discoKey
+	}
+
+	return discoKey
+}
+
+func PrivateKeyEnsurePrefix(privateKey string) string {
+	if !strings.HasPrefix(privateKey, privateHexPrefix) {
+		return privateHexPrefix + privateKey
+	}
+
+	return privateKey
+}
+
+func DecodeAndUnmarshalNaCl(
+	msg []byte,
+	output interface{},
+	pubKey *key.MachinePublic,
+	privKey *key.MachinePrivate,
+) error {
+	// log.Trace().
+	// 	Str("pubkey", pubKey.ShortString()).
+	// 	Int("length", len(msg)).
+	// 	Msg("Trying to decrypt")
+
+	decrypted, ok := privKey.OpenFrom(*pubKey, msg)
+	if !ok {
+		return ErrCannotDecryptResponse
+	}
+
+	if err := json.Unmarshal(decrypted, output); err != nil {
+		return err
+	}
+
+	return nil
+}