From e198e6693fa281d448540f2ffabb09ef237f8499 Mon Sep 17 00:00:00 2001
From: Matt Morehouse <mattmorehouse@gmail.com>
Date: Fri, 28 Apr 2023 10:20:08 -0500
Subject: [PATCH] lnwire: add FuzzConvertFixedSignature test

Test conversion of fixed 64-byte signatures to DER-encoded signatures.
---
 lnwire/fuzz_test.go | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/lnwire/fuzz_test.go b/lnwire/fuzz_test.go
index b1392881e..53f152328 100644
--- a/lnwire/fuzz_test.go
+++ b/lnwire/fuzz_test.go
@@ -843,3 +843,39 @@ func FuzzParseRawSignature(f *testing.F) {
 		}
 	})
 }
+
+// FuzzConvertFixedSignature tests that conversion of fixed 64-byte signatures
+// to DER-encoded signatures does not panic and that parsing and reconverting
+// the signatures does not mutate them.
+func FuzzConvertFixedSignature(f *testing.F) {
+	f.Fuzz(func(t *testing.T, data []byte) {
+		var sig Sig
+		if len(data) > len(sig) {
+			return
+		}
+		copy(sig[:], data)
+
+		derSig, err := sig.ToSignature()
+		if err != nil {
+			return
+		}
+
+		sig2, err := NewSigFromSignature(derSig)
+		if err != nil {
+			t.Fatalf("failed to parse signature: %v", err)
+		}
+
+		derSig2, err := sig2.ToSignature()
+		if err != nil {
+			t.Fatalf("failed to reconvert signature to DER: %v",
+				err)
+		}
+
+		derBytes := derSig.Serialize()
+		derBytes2 := derSig2.Serialize()
+		if !bytes.Equal(derBytes, derBytes2) {
+			t.Fatalf("signature mismatch: %v != %v", derBytes,
+				derBytes2)
+		}
+	})
+}