From bd3735939306c831f7b98f34606000c3fdfe6182 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 22 Jan 2020 18:24:58 +0300
Subject: [PATCH] compiler: implement ECDSA signature verification

Add VerifySignature interop for signature verification.
It is converted to VERIFY opcode.
---
 pkg/compiler/analysis.go     |  1 +
 pkg/compiler/codegen.go      |  2 ++
 pkg/compiler/verify_test.go  | 55 ++++++++++++++++++++++++++++++++++++
 pkg/interop/crypto/crypto.go |  5 ++++
 4 files changed, 63 insertions(+)
 create mode 100644 pkg/compiler/verify_test.go

diff --git a/pkg/compiler/analysis.go b/pkg/compiler/analysis.go
index f57abf85d..da05ad2f6 100644
--- a/pkg/compiler/analysis.go
+++ b/pkg/compiler/analysis.go
@@ -14,6 +14,7 @@ var (
 	builtinFuncs = []string{
 		"len", "append", "SHA256",
 		"SHA1", "Hash256", "Hash160",
+		"VerifySignature",
 		"FromAddress", "Equals",
 	}
 )
diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index d0923956e..ee4b57562 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -666,6 +666,8 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		emitOpcode(c.prog.BinWriter, opcode.HASH256)
 	case "Hash160":
 		emitOpcode(c.prog.BinWriter, opcode.HASH160)
+	case "VerifySignature":
+		emitOpcode(c.prog.BinWriter, opcode.VERIFY)
 	case "Equals":
 		emitOpcode(c.prog.BinWriter, opcode.EQUAL)
 	case "FromAddress":
diff --git a/pkg/compiler/verify_test.go b/pkg/compiler/verify_test.go
new file mode 100644
index 000000000..276e2fab2
--- /dev/null
+++ b/pkg/compiler/verify_test.go
@@ -0,0 +1,55 @@
+package compiler_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/crypto/keys"
+	"github.com/stretchr/testify/require"
+)
+
+func TestVerifyGood(t *testing.T) {
+	msg := []byte("test message")
+	pub, sig := signMessage(t, msg)
+	src := getVerifyProg(pub, sig, msg)
+
+	eval(t, src, true)
+}
+
+func TestVerifyBad(t *testing.T) {
+	msg := []byte("test message")
+	pub, sig := signMessage(t, msg)
+	sig[0] = ^sig[0]
+	src := getVerifyProg(pub, sig, msg)
+
+	eval(t, src, false)
+}
+
+func signMessage(t *testing.T, msg []byte) ([]byte, []byte) {
+	key, err := keys.NewPrivateKey()
+	require.NoError(t, err)
+
+	sig := key.Sign(msg)
+	pub := key.PublicKey().Bytes()
+
+	return pub, sig
+}
+
+func getVerifyProg(pub, sig, msg []byte) string {
+	pubS := fmt.Sprintf("%#v", pub)
+	sigS := fmt.Sprintf("%#v", sig)
+	msgS := fmt.Sprintf("%#v", msg)
+
+	return `
+		package hello
+
+		import "github.com/CityOfZion/neo-go/pkg/interop/crypto"
+
+		func Main() bool {
+			pub := ` + pubS + `
+			sig := ` + sigS + `
+			msg := ` + msgS + `
+			return crypto.VerifySignature(msg, sig, pub)
+		}
+	`
+}
diff --git a/pkg/interop/crypto/crypto.go b/pkg/interop/crypto/crypto.go
index 6877fd46e..abfe586e8 100644
--- a/pkg/interop/crypto/crypto.go
+++ b/pkg/interop/crypto/crypto.go
@@ -22,3 +22,8 @@ func Hash160(b []byte) []byte {
 func Hash256(b []byte) []byte {
 	return nil
 }
+
+// VerifySignature checks that sig is msg's signature with pub.
+func VerifySignature(msg []byte, sig []byte, pub []byte) bool {
+	return false
+}