Initial commit

pkg/strenc/keyderive.go

@@ -0,0 +1,48 @@
+package strenc
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/binary"
+	"os"
+	"runtime"
+)
+
+const buildSeed = 0xDEAD_BEEF_CAFE_BABE
+
+func DeriveMasterKey(seed [32]byte) [32]byte {
+	var out [32]byte
+
+	mac := hmac.New(sha256.New, seed[:])
+	mac.Write([]byte("strenc.masterkey.v1"))
+	copy(out[:16], mac.Sum(nil))
+
+	mac.Reset()
+	mac.Write(seed[:])
+	mac.Write([]byte("strenc.masterkey.v2"))
+	copy(out[16:], mac.Sum(nil))
+
+	return out
+}
+
+func DeriveFromBinary() [32]byte {
+	exePath, err := os.Executable()
+	if err != nil {
+		exePath = "unknown"
+	}
+
+	mac := hmac.New(sha256.New, []byte("strenc.binary.seed"))
+	mac.Write([]byte(exePath))
+
+	var seedBuf [8]byte
+	binary.LittleEndian.PutUint64(seedBuf[:], buildSeed)
+	mac.Write(seedBuf[:])
+
+	mac.Write([]byte(runtime.GOOS))
+	mac.Write([]byte(runtime.GOARCH))
+
+	var seed [32]byte
+	copy(seed[:], mac.Sum(nil))
+
+	return DeriveMasterKey(seed)
+}