initial: ZeroTier-like P2P mesh VPN server with multi-tenant Web UI

internal/vl1/noise.go

@@ -0,0 +1,103 @@
+package vl1
+
+import (
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/chacha20poly1305"
+	"golang.org/x/crypto/sha3"
+)
+
+type NoiseCipher struct {
+	sendCipher cipher.AEAD
+	recvCipher cipher.AEAD
+	sendNonce  uint64
+	recvNonce  uint64
+}
+
+func NewNoiseCipher(sendKey, recvKey [32]byte) *NoiseCipher {
+	send, err := chacha20poly1305.New(sendKey[:])
+	if err != nil {
+		panic(err)
+	}
+	recv, err := chacha20poly1305.New(recvKey[:])
+	if err != nil {
+		panic(err)
+	}
+	return &NoiseCipher{
+		sendCipher: send,
+		recvCipher: recv,
+	}
+}
+
+func DeriveKeysFromPSK(psk string, localPub, remotePub []byte) ([32]byte, [32]byte) {
+	h := sha3.New256()
+	h.Write([]byte(psk))
+	h.Write(localPub)
+	h.Write(remotePub)
+	sum := h.Sum(nil)
+
+	var sendKey, recvKey [32]byte
+	copy(sendKey[:], sum[:32])
+
+	h.Reset()
+	h.Write(sum)
+	h.Write([]byte("reverse"))
+	rev := h.Sum(nil)
+	copy(recvKey[:], rev[:32])
+
+	return sendKey, recvKey
+}
+
+func (nc *NoiseCipher) Encrypt(plaintext []byte) ([]byte, error) {
+	nonce := make([]byte, 12)
+	binary.BigEndian.PutUint64(nonce[4:], nc.sendNonce)
+	nc.sendNonce++
+
+	ciphertext := nc.sendCipher.Seal(nil, nonce, plaintext, nil)
+	return ciphertext, nil
+}
+
+func (nc *NoiseCipher) Decrypt(ciphertext []byte) ([]byte, error) {
+	nonce := make([]byte, 12)
+	binary.BigEndian.PutUint64(nonce[4:], nc.recvNonce)
+	nc.recvNonce++
+
+	plaintext, err := nc.recvCipher.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, fmt.Errorf("decrypt: %w", err)
+	}
+	return plaintext, nil
+}
+
+func (nc *NoiseCipher) EncryptTo(buf []byte, plaintext []byte) (int, error) {
+	nonce := make([]byte, 12)
+	binary.BigEndian.PutUint64(nonce[4:], nc.sendNonce)
+	nc.sendNonce++
+
+	ciphertext := nc.sendCipher.Seal(buf[:0], nonce, plaintext, nil)
+	return len(ciphertext), nil
+}
+
+func (nc *NoiseCipher) DecryptTo(buf []byte, ciphertext []byte) ([]byte, error) {
+	nonce := make([]byte, 12)
+	binary.BigEndian.PutUint64(nonce[4:], nc.recvNonce)
+	nc.recvNonce++
+
+	plaintext, err := nc.recvCipher.Open(buf[:0], nonce, ciphertext, nil)
+	if err != nil {
+		return nil, fmt.Errorf("decrypt: %w", err)
+	}
+	return plaintext, nil
+}
+
+func generateSessionKey() [32]byte {
+	var key [32]byte
+	if _, err := io.ReadFull(rand.Reader, key[:]); err != nil {
+		panic(err)
+	}
+	return key
+}