wireguard: introduce KeyPair.Validate()

it will also set the PublicKey field is empty

Signed-off-by: Alejandro Mery <amery@jpi.io>

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/burntSushi/toml v0.3.1
 	github.com/mgechev/revive v1.3.2
 	github.com/spf13/cobra v1.7.0
+	golang.org/x/crypto v0.12.0
 	gopkg.in/gcfg.v1 v1.2.3
 )
 

go.sum

@@ -70,6 +70,8 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+golang.org/x/crypto v0.12.0 h1:tFM/ta59kqch6LlvYnPa0yx5a83cL2nHflFhYKvv9Yk=
+golang.org/x/crypto v0.12.0/go.mod h1:NF0Gs7EO5K4qLn+Ylc+fih8BSTeIjAP05siRnAh98yw=
 golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 h1:MGwJjxBy0HJshjDNfLsYO8xppfqWlA5ZT9OhtUUhTNw=
 golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
 golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=

pkg/wireguard/config.go

@@ -31,13 +31,13 @@ func (f *Config) Peers() int {
 // InterfaceConfig represents the [Interface] section
 type InterfaceConfig struct {
 	Address    netip.Addr
-	PrivateKey BinaryKey
+	PrivateKey PrivateKey
 	ListenPort uint16
 }
 
 // PeerConfig represents a [Peer] section
 type PeerConfig struct {
-	PublicKey  BinaryKey
+	PublicKey  PublicKey
 	Endpoint   EndpointAddress
 	AllowedIPs []netip.Prefix
 }
@@ -135,7 +135,7 @@ func (p interfaceConfig) Export() (InterfaceConfig, error) {
 		ListenPort: p.ListenPort,
 	}
 
-	out.PrivateKey, err = BinaryKeyFromBase64(p.PrivateKey)
+	out.PrivateKey, err = PrivateKeyFromBase64(p.PrivateKey)
 	if err != nil {
 		err = core.Wrap(err, "PrivateKey")
 		return InterfaceConfig{}, err
@@ -162,7 +162,7 @@ func (v *intermediateConfig) ExportPeer(i int) (PeerConfig, error) {
 	}
 
 	// PublicKey
-	out.PublicKey, err = BinaryKeyFromBase64(v.Peer.PublicKey[i])
+	out.PublicKey, err = PublicKeyFromBase64(v.Peer.PublicKey[i])
 	if err != nil {
 		err = core.Wrap(err, "PublicKey")
 		return out, err

pkg/wireguard/keys.go

@@ -2,35 +2,171 @@ package wireguard
 
 import (
 	"bytes"
+	"crypto/rand"
 	"encoding/base64"
+	"errors"
+
+	"golang.org/x/crypto/curve25519"
 )
 
-// BinaryKey is a binary blob
-type BinaryKey []byte
+const (
+	// PrivateKeySize is the length in bytes of a Wireguard Private Key
+	PrivateKeySize = 32
+	// PublicKeySize is the length in bytes of a Wireguard Public Key
+	PublicKeySize = 32
+)
 
-func (k BinaryKey) String() string {
-	return base64.StdEncoding.EncodeToString(k)
+var (
+	// ErrInvalidKeySize indicates the key size is wrong
+	ErrInvalidKeySize = errors.New("invalid key size")
+	// ErrInvalidPrivateKey indicates the private key is invalid
+	ErrInvalidPrivateKey = errors.New("invalid private key")
+	// ErrInvalidPublicKey indicates the public key is invalid
+	ErrInvalidPublicKey = errors.New("invalid public key")
+)
+
+type (
+	// PrivateKey is a binary Wireguard Private Key
+	PrivateKey []byte
+	// PublicKey is a binary Wireguard Public Key
+	PublicKey []byte
+)
+
+func (key PrivateKey) String() string {
+	return encodeKey(key)
+}
+
+func (pub PublicKey) String() string {
+	return encodeKey(pub)
 }
 
 // IsZero tells if the key hasn't been set
-func (k BinaryKey) IsZero() bool {
-	return len(k) == 0
+func (key PrivateKey) IsZero() bool {
+	return len(key) == 0
 }
 
-// Equal checks if two keys are identical
-func (k BinaryKey) Equal(alter BinaryKey) bool {
-	return bytes.Equal(k, alter)
+// IsZero tells if the key hasn't been set
+func (pub PublicKey) IsZero() bool {
+	return len(pub) == 0
 }
 
-// BinaryKeyFromBase64 decodes a base64-based string into
-// a [BinaryKey]
-func BinaryKeyFromBase64(data string) (BinaryKey, error) {
+// Equal checks if two private keys are identical
+func (key PrivateKey) Equal(alter PrivateKey) bool {
+	return bytes.Equal(key, alter)
+}
+
+// Equal checks if two public keys are identical
+func (pub PublicKey) Equal(alter PublicKey) bool {
+	return bytes.Equal(pub, alter)
+}
+
+// PrivateKeyFromBase64 decodes a base64-based string into
+// a [PrivateKey]
+func PrivateKeyFromBase64(data string) (PrivateKey, error) {
+	b, err := decodeKey(data, PrivateKeySize)
+	return b, err
+}
+
+// PublicKeyFromBase64 decodes a base64-based string into
+// a [PublicKey]
+func PublicKeyFromBase64(data string) (PublicKey, error) {
+	b, err := decodeKey(data, PublicKeySize)
+	return b, err
+}
+
+func encodeKey(b []byte) string {
+	switch {
+	case len(b) == 0:
+		return ""
+	default:
+		return base64.StdEncoding.EncodeToString(b)
+	}
+}
+
+func decodeKey(data string, size int) ([]byte, error) {
 	b, err := base64.StdEncoding.DecodeString(data)
-	return BinaryKey(b), err
+	switch {
+	case err != nil:
+		return []byte{}, err
+	case len(b) != size:
+		err = ErrInvalidKeySize
+		return []byte{}, err
+	default:
+		return b, nil
+	}
+}
+
+// NewPrivateKey creates a new PrivateKey
+func NewPrivateKey() (PrivateKey, error) {
+	var s [PrivateKeySize]byte
+
+	_, err := rand.Read(s[:])
+	if err != nil {
+		return []byte{}, err
+	}
+
+	// apply same clamping as wireguard-go/device/noise-helpers.go
+	s[0] &= 0xf8
+	s[31] = (s[31] & 0x7f) | 0x40
+
+	return s[:], nil
+}
+
+// Public generates the corresponding PublicKey
+func (key PrivateKey) Public() PublicKey {
+	if len(key) != PrivateKeySize {
+		return []byte{}
+	}
+
+	out := [PublicKeySize]byte{}
+	in := (*[PrivateKeySize]byte)(key)
+
+	curve25519.ScalarBaseMult(&out, in)
+	return out[:]
 }
 
 // KeyPair holds a Key pair
 type KeyPair struct {
-	PrivateKey BinaryKey
-	PublicKey  BinaryKey
+	PrivateKey PrivateKey
+	PublicKey  PublicKey
+}
+
+// Validate checks the PublicKey matches the PrivateKey,
+// and sets the PublicKey if missing
+func (kp *KeyPair) Validate() error {
+	keyLen := len(kp.PrivateKey)
+	pubLen := len(kp.PublicKey)
+
+	switch {
+	case keyLen != PrivateKeySize:
+		// bad private key
+		return ErrInvalidPrivateKey
+	case pubLen == 0:
+		// no public key, set it
+		kp.PublicKey = kp.PrivateKey.Public()
+		return nil
+	case pubLen != PublicKeySize:
+		// bad public key
+		return ErrInvalidPublicKey
+	case !kp.PrivateKey.Public().Equal(kp.PublicKey):
+		// wrong public key
+		return ErrInvalidPublicKey
+	default:
+		// correct public key
+		return nil
+	}
+}
+
+// NewKeyPair creates a new KeyPair for Wireguard
+func NewKeyPair() (*KeyPair, error) {
+	key, err := NewPrivateKey()
+	if err != nil {
+		return nil, err
+	}
+
+	out := &KeyPair{
+		PrivateKey: key,
+		PublicKey:  key.Public(),
+	}
+	return out, nil
 }

pkg/zones/env.go

@@ -31,25 +31,7 @@ func (m *Zones) writeEnvZone(w io.Writer, z *Zone) {
 	m.writeEnvVar(w, z.Name, "ZONE%v_%s", zoneID, "NAME")
 
 	// ZONE{zoneID}_GW
-	firstNodeID := 0
-	gatewayID := 0
-	z.ForEachMachine(func(p *Machine) bool {
-		nodeID := p.ID()
-
-		if firstNodeID == 0 {
-			firstNodeID = nodeID
-		}
-
-		if _, found := p.getRingInfo(0); found {
-			gatewayID = nodeID
-		}
-
-		return gatewayID != 0
-	})
-
-	if gatewayID == 0 {
-		gatewayID = firstNodeID
-	}
+	gatewayID := getRingZeroGatewayID(z)
 	m.writeEnvVar(w, fmt.Sprintf("%v", gatewayID), "ZONE%v_%s", zoneID, "GW")
 
 	// ZONE{zoneID}_IP
@@ -95,3 +77,28 @@ func genEnvZoneNodes(z *Zone) string {
 	}
 	return strings.Join(s, " ")
 }
+
+func getRingZeroGatewayID(z *Zone) int {
+	var firstNodeID, gatewayID int
+
+	z.ForEachMachine(func(p *Machine) bool {
+		nodeID := p.ID()
+
+		if firstNodeID == 0 {
+			firstNodeID = nodeID
+		}
+
+		if _, found := p.getRingInfo(0); found {
+			gatewayID = nodeID
+		}
+
+		return gatewayID != 0
+	})
+
+	switch {
+	case gatewayID == 0:
+		return firstNodeID
+	default:
+		return gatewayID
+	}
+}