From 15069df98488810840f17f2508bcea17c8538a2e Mon Sep 17 00:00:00 2001
From: p4u <p4u@dabax.net>
Date: Wed, 16 Jan 2019 12:27:35 +0100
Subject: [PATCH] Introduce crypto library

Add signature package based on nancl

Signed-off-by: p4u <p4u@dabax.net>
---
 crypto/signature/signature.go      | 69 ++++++++++++++++++++++++++++++
 crypto/signature/signature_test.go | 26 +++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 crypto/signature/signature.go
 create mode 100644 crypto/signature/signature_test.go

diff --git a/crypto/signature/signature.go b/crypto/signature/signature.go
new file mode 100644
index 0000000..5cf1a21
--- /dev/null
+++ b/crypto/signature/signature.go
@@ -0,0 +1,69 @@
+package signature
+
+import (
+	"fmt"
+	sign "golang.org/x/crypto/nacl/sign"
+	rand "crypto/rand"
+	hex "encoding/hex"
+	"errors"
+)
+
+const signatureSize = 128
+
+type SignKeys struct {
+    Public *[32]byte
+    Private *[64]byte
+}
+
+func (k *SignKeys) Generate() error {
+  var err error
+  k.Public = new([32]byte)
+  k.Private = new([64]byte)
+  k.Public, k.Private, err = sign.GenerateKey(rand.Reader)
+  return err
+}
+
+func (k *SignKeys) AddHexKeys(pubHex string, privHex string) error {
+  if len(pubHex) < 32 || len(privHex) < 64 {
+    return errors.New("Wrong key size, must be pub:32 priv:64 (bytes)")
+  }
+  pubKey, err := hex.DecodeString(pubHex)
+  if err != nil { return err }
+  privKey, err := hex.DecodeString(privHex)
+  if err != nil { return err }
+  k.Public = new([32]byte)
+  k.Private = new([64]byte)
+  copy(k.Public[:],pubKey[:32])
+  copy(k.Private[:],privKey[:64])
+  return nil
+}
+
+func (k *SignKeys) HexString() (string, string) {
+  pubHex := hex.EncodeToString(k.Public[:])
+  privHex := hex.EncodeToString(k.Private[:])
+  return pubHex, privHex
+}
+
+// message is a normal string (no HexString)
+func (k *SignKeys) Sign(message string) (string, error) {
+  if k.Private == nil {
+    return "", errors.New("No private key available")
+  }
+  signature := sign.Sign(nil, []byte(message), k.Private)
+  signHexFull := hex.EncodeToString(signature)
+  return signHexFull[:signatureSize], nil
+}
+
+// message is a normal string, signature and pubHex are HexStrings
+func (k *SignKeys) Verify(message, signature, pubHex string) (bool, error) {
+  msgHex := hex.EncodeToString([]byte(message))
+  signatureAndText := fmt.Sprintf("%s%s", signature, msgHex)
+  signatureToVerify, err :=  hex.DecodeString(signatureAndText)
+  if err != nil { return false, err }
+  pubKeyToVerify, err := hex.DecodeString(pubHex)
+  if err != nil { return false, err }
+  pubKey := new([32]byte)
+  copy(pubKey[:],pubKeyToVerify[:32])
+  _, result := sign.Open(nil, signatureToVerify, pubKey)
+  return result, nil
+}
diff --git a/crypto/signature/signature_test.go b/crypto/signature/signature_test.go
new file mode 100644
index 0000000..6281581
--- /dev/null
+++ b/crypto/signature/signature_test.go
@@ -0,0 +1,26 @@
+package signature
+
+import "testing"
+
+func TestSignature(t *testing.T) {
+	t.Log("Testing signature creation and verification")
+	var s SignKeys
+	s.Generate()
+	pub, priv := s.HexString()
+	t.Logf("Generated pub:%s priv:%s\n", pub, priv)
+	message := "Hello, this is gonna be signed!"
+	t.Logf("Message to sign: %s\n", message)
+	msgSign, err := s.Sign(message)
+	if err != nil {
+		t.Errorf("Error while signing %s\n", err)
+	}
+	t.Logf("Signature of message: %s\n", msgSign)
+	v, err := s.Verify(message, msgSign, pub)
+	if err != nil {
+		t.Errorf("Verification error: %s\n", err)
+	}
+	if !v {
+		t.Error("Verification failed!")
+	}
+	t.Logf("Testing verification... %t\n", v)
+}