fix: update sha generation logic

Signed-off-by: Anish Ramasekar <[email protected]>

Author: aramase

pkg/util/secretutil/secret.go

@@ -23,12 +23,13 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
-	"io"
-	"sort"
+	"math"
 	"strings"
 
+	"golang.org/x/crypto/cryptobyte"
 	"golang.org/x/crypto/pkcs12"
 	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/util/sets"
 
 	secretsyncv1alpha1 "sigs.k8s.io/secrets-store-sync-controller/api/v1alpha1"
 )
@@ -212,23 +213,33 @@ func GetSecretData(secretObjData []secretsyncv1alpha1.SecretObjectData, secretTy
 
 // GetSHAFromSecret gets SHA for the secret data
 func GetSHAFromSecret(data map[string][]byte) (string, error) {
-	values := make([]string, 0, len(data))
-	for k, v := range data {
-		values = append(values, k+"="+string(v))
-	}
-	// sort the values to always obtain a deterministic SHA for
-	// same content in different order
-	sort.Strings(values)
-	return generateSHA(strings.Join(values, ";"))
-}
+	if len(data) == 0 {
+		return "", nil
+	}
+
+	b := cryptobyte.NewBuilder(nil)
+	if len(data) > math.MaxUint32 {
+		return "", fmt.Errorf("data too large: length exceeds uint32 max")
+	}
+	// we are checking the length of the data to be less than uint32 max
+	// so we can safely cast it to uint32 without worrying about overflow
+	b.AddUint32(uint32(len(data))) // nolint:gosec
 
-// generateSHA generates SHA from string
-func generateSHA(data string) (string, error) {
-	hasher := sha256.New()
-	_, err := io.WriteString(hasher, data)
+	keys := sets.StringKeySet(data).List()
+
+	for _, k := range keys {
+		b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
+			b.AddBytes([]byte(k))
+		})
+		b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
+			b.AddBytes(data[k])
+		})
+	}
+
+	hashData, err := b.Bytes()
 	if err != nil {
 		return "", err
 	}
-	sha := hasher.Sum(nil)
-	return fmt.Sprintf("%x", sha), nil
+
+	return fmt.Sprintf("%x", sha256.Sum256(hashData)), nil
 }