embeddable-dll-service: add key generation function to replace bcrypt

BCrypt is Win10+ and kind of clunky to use. The tunnel.dll binary has
this code in it anyway, so doing it there doesn't actually increase
the size of the binary.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/embeddable-dll-service/main.go b/embeddable-dll-service/main.go
index a8ce7c10..edf72fba 100644
--- a/embeddable-dll-service/main.go
+++ b/embeddable-dll-service/main.go
@@ -7,10 +7,16 @@ package main
 
 import (
 	"C"
+
+	"golang.org/x/crypto/curve25519"
+
 	"golang.zx2c4.com/wireguard/windows/conf"
 	"golang.zx2c4.com/wireguard/windows/tunnel"
+
+	"crypto/rand"
 	"log"
 	"path/filepath"
+	"unsafe"
 )
 
 //export WireGuardTunnelService
@@ -24,4 +30,18 @@ func WireGuardTunnelService(confFile string) bool {
 	return err == nil
 }
 
+//export WireGuardGenerateKeypair
+func WireGuardGenerateKeypair(publicKey *byte, privateKey *byte) {
+	publicKeyArray := (*[32]byte)(unsafe.Pointer(publicKey))
+	privateKeyArray := (*[32]byte)(unsafe.Pointer(privateKey))
+	n, err := rand.Read(privateKeyArray[:])
+	if err != nil || n != len(privateKeyArray) {
+		panic("Unable to generate random bytes")
+	}
+	privateKeyArray[0] &= 248
+	privateKeyArray[31] = (privateKeyArray[31] & 127) | 64
+
+	curve25519.ScalarBaseMult(publicKeyArray, privateKeyArray)
+}
+
 func main() {}