test: add fuzzing of NewCarReader

car_test.go

@@ -75,9 +75,11 @@ func TestRoundtrip(t *testing.T) {
 	}
 }
 
+// fixture is a clean single-block, single-root CAR
+const fixtureStr = "3aa265726f6f747381d82a58250001711220151fe9e73c6267a7060c6f6c4cca943c236f4b196723489608edb42a8b8fa80b6776657273696f6e012c01711220151fe9e73c6267a7060c6f6c4cca943c236f4b196723489608edb42a8b8fa80ba165646f646779f5"
+
 func TestEOFHandling(t *testing.T) {
-	// fixture is a clean single-block, single-root CAR
-	fixture, err := hex.DecodeString("3aa265726f6f747381d82a58250001711220151fe9e73c6267a7060c6f6c4cca943c236f4b196723489608edb42a8b8fa80b6776657273696f6e012c01711220151fe9e73c6267a7060c6f6c4cca943c236f4b196723489608edb42a8b8fa80ba165646f646779f5")
+	fixture, err := hex.DecodeString(fixtureStr)
 	if err != nil {
 		t.Fatal(err)
 	}

fuzz_test.go

@@ -0,0 +1,35 @@
+//go:build go1.18
+// +build go1.18
+
+package car_test
+
+import (
+	"bytes"
+	"encoding/hex"
+	"io"
+	"testing"
+
+	car "github.com/ipld/go-car"
+)
+
+func FuzzCarReader(f *testing.F) {
+	fixture, err := hex.DecodeString(fixtureStr)
+	if err != nil {
+		f.Fatal(err)
+	}
+	f.Add(fixture)
+
+	f.Fuzz(func(t *testing.T, data []byte) {
+		r, err := car.NewCarReader(bytes.NewReader(data))
+		if err != nil {
+			return
+		}
+
+		for {
+			_, err = r.Next()
+			if err == io.EOF {
+				return
+			}
+		}
+	})
+}

testdata/fuzz/FuzzCarReader/21a90a70853c333c6b9ddc133bae39a14164874ed8abdee1f6a6795311a0e546

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\xe0\xe0\xe0\xe0\xa7\x06\folLʔ<#oK\x19g#H\x96\b\xed\xb4*\x8b\x8f\xa8\vgversion\x19")

testdata/fuzz/FuzzCarReader/5857e57e4072c6b0d8684030cc13b5570849c89b3dbf5bc0152abc66c9642f3e

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte(":\xa2eroots\x81\xd80X%\x00\x0100 00000000000000000000000000000000gversion\x01\x010")