tenseleyflow/shithub / 706426a

+// SPDX-License-Identifier: AGPL-3.0-or-later

+

+package webhook

+

+import (

+	"crypto/hmac"

+	"crypto/sha256"

+	"encoding/hex"

+)

+

+// SignSHA256 returns the X-Shithub-Signature-256 header value for the

+// given body and per-webhook secret. The format mirrors GitHub's

+// (`sha256=<hex>`) so existing receiver libraries verify cleanly.

+func SignSHA256(secret, body []byte) string {

+	mac := hmac.New(sha256.New, secret)

+	mac.Write(body)

+	return "sha256=" + hex.EncodeToString(mac.Sum(nil))

+}

+

+// VerifySHA256 returns true when sig matches HMAC-SHA256(secret, body).

+// Uses constant-time compare so the verifier doesn't leak timing info.

+// Provided as the receiver-side helper that test code (and any future

+// inbound webhook surface) can reuse.

+func VerifySHA256(secret, body []byte, sig string) bool {

+	want := SignSHA256(secret, body)

+	if len(want) != len(sig) {

+		return false

+	}

+	return hmac.Equal([]byte(want), []byte(sig))

+}

+// SPDX-License-Identifier: AGPL-3.0-or-later

+

+package webhook

+

+import "testing"

+

+func TestSignAndVerifyRoundtrip(t *testing.T) {

+	secret := []byte("super-secret")

+	body := []byte(`{"hello":"world"}`)

+

+	sig := SignSHA256(secret, body)

+	if !VerifySHA256(secret, body, sig) {

+		t.Fatalf("VerifySHA256 returned false on a freshly signed body")

+	}

+}

+

+func TestVerifyRejectsTamperedBody(t *testing.T) {

+	secret := []byte("super-secret")

+	body := []byte(`{"hello":"world"}`)

+	sig := SignSHA256(secret, body)

+

+	tampered := []byte(`{"hello":"WORLD"}`)

+	if VerifySHA256(secret, tampered, sig) {

+		t.Fatalf("VerifySHA256 accepted tampered body")

+	}

+}

+

+func TestVerifyRejectsWrongSecret(t *testing.T) {

+	body := []byte(`{"x":1}`)

+	sig := SignSHA256([]byte("alice"), body)

+	if VerifySHA256([]byte("bob"), body, sig) {

+		t.Fatalf("VerifySHA256 accepted wrong secret")

+	}

+}

+

+func TestSignaturePrefix(t *testing.T) {

+	sig := SignSHA256([]byte("k"), []byte("v"))

+	if got := sig[:7]; got != "sha256=" {

+		t.Fatalf("signature prefix = %q; want %q", got, "sha256=")

+	}

+}