From e3584692a4d380e6fe58008a4d238932632d890a Mon Sep 17 00:00:00 2001
From: Hussein Ait Lahcen <hussein.aitlahcen@gmail.com>
Date: Mon, 9 Oct 2023 11:55:31 +0200
Subject: [PATCH] feat(galoisd): sha256 test

---
 galoisd/pkg/sha256/api.go      | 11 -----
 galoisd/pkg/sha256/api_test.go | 79 ++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 11 deletions(-)
 create mode 100644 galoisd/pkg/sha256/api_test.go

diff --git a/galoisd/pkg/sha256/api.go b/galoisd/pkg/sha256/api.go
index 7751c9eca7..95ed6d132c 100644
--- a/galoisd/pkg/sha256/api.go
+++ b/galoisd/pkg/sha256/api.go
@@ -283,7 +283,6 @@ func padding(api frontend.API, input []frontend.Variable, size frontend.Variable
 
 	// helpers
 	inputLen := len(input)
-	paddingLen := inputLen % 64
 
 	// t is start index of inputBitLen encoding
 	var t int
@@ -304,16 +303,6 @@ func padding(api frontend.API, input []frontend.Variable, size frontend.Variable
 		out[i] = 0
 	}
 
-	// return if no padding required
-	if paddingLen == 0 {
-
-		// overwrite into fixed size slice
-		for i := 0; i < inputLen; i++ {
-			out[i] = input[i]
-		}
-		return out
-	}
-
 	// existing bytes into out
 	for i := 0; i < inputLen; i++ {
 		out[i] = input[i]
diff --git a/galoisd/pkg/sha256/api_test.go b/galoisd/pkg/sha256/api_test.go
new file mode 100644
index 0000000000..39467b18b9
--- /dev/null
+++ b/galoisd/pkg/sha256/api_test.go
@@ -0,0 +1,79 @@
+package sha256
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"testing"
+
+	"github.com/consensys/gnark-crypto/ecc"
+	"github.com/consensys/gnark/backend"
+	"github.com/consensys/gnark/frontend"
+	"github.com/consensys/gnark/test"
+)
+
+const compressThreshold = 1000
+
+const MaxPreimageLength = 64
+
+const ImageLength = 32
+
+type sha256Circuit struct {
+	PreimageLength frontend.Variable
+	Preimage       [MaxPreimageLength]frontend.Variable
+	Image          [ImageLength]frontend.Variable
+}
+
+func (c *sha256Circuit) Define(api frontend.API) error {
+	api.AssertIsLessOrEqual(c.PreimageLength, MaxPreimageLength)
+	hash := NewSHA256(api)
+	actualPreimage := make([]frontend.Variable, MaxPreimageLength)
+	for i := 0; i < MaxPreimageLength; i++ {
+		actualPreimage[i] = c.Preimage[i]
+	}
+	image := hash.Hash(actualPreimage, c.PreimageLength)
+	for i := 0; i < ImageLength; i++ {
+		api.AssertIsEqual(image[i], c.Image[i])
+	}
+	return nil
+}
+
+func TestSha256(t *testing.T) {
+	message := make([]byte, MaxPreimageLength)
+	_, err := rand.Read(message)
+	if err != nil {
+		panic(err)
+	}
+
+	nativeHasher := sha256.New()
+	nativeHasher.Write(message)
+	final := nativeHasher.Sum(nil)
+
+	var preimage [MaxPreimageLength]frontend.Variable
+	for i := 0; i < MaxPreimageLength; i++ {
+		if i < len(message) {
+			preimage[i] = message[i]
+		} else {
+			preimage[i] = 0
+		}
+	}
+
+	var image [ImageLength]frontend.Variable
+	for i := 0; i < ImageLength; i++ {
+		image[i] = final[i]
+	}
+
+	circuit := sha256Circuit{}
+	assignment := sha256Circuit{
+		Preimage:       preimage,
+		PreimageLength: len(message),
+		Image:          image,
+	}
+	test.NewAssert(t).ProverSucceeded(
+		&circuit,
+		&assignment,
+		test.WithCurves(ecc.BN254),
+		test.NoFuzzing(),
+		test.WithCurves(ecc.BN254),
+		test.WithBackends(backend.GROTH16),
+	)
+}