1 files changed, 52 insertions, 0 deletions
diff --git a/internal/dns/fuzz_test.go b/internal/dns/fuzz_test.go
new file mode 100644
index 0000000..8aa1653
--- /dev/null
+++ b/internal/dns/fuzz_test.go
@@ -0,0 +1,52 @@
+package dns
+
+import (
+	"testing"
+)
+
+func FuzzUnpack(f *testing.F) {
+	seed := []byte{
+		0x00, 0x01, // ID
+		0x01, 0x00, // flags: RD=1
+		0x00, 0x01, // QDCOUNT = 1
+		0x00, 0x00, // ANCOUNT = 0
+		0x00, 0x00, // NSCOUNT = 0
+		0x00, 0x00, // ARCOUNT = 0
+		0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+		0x03, 'c', 'o', 'm',
+		0x00,       // root label
+		0x00, 0x01, // QTYPE = A
+		0x00, 0x01, // QCLASS = IN
+	}
+	f.Add(seed)
+
+	seedResp := []byte{
+		0x00, 0x01, // ID
+		0x85, 0x80, // flags: QR=1, AA=1, RD=1, RA=1
+		0x00, 0x01, // QDCOUNT = 1
+		0x00, 0x01, // ANCOUNT = 1
+		0x00, 0x00, // NSCOUNT = 0
+		0x00, 0x00, // ARCOUNT = 0
+		0x03, 'w', 'w', 'w',
+		0x07, 'e', 'x', 'a', 'm', 'p', 'l', 'e',
+		0x03, 'c', 'o', 'm',
+		0x00,
+		0x00, 0x01, // TYPE = A
+		0x00, 0x01, // CLASS = IN
+		0x00, 0x00, 0x00, 0x3C, // TTL = 60
+		0x00, 0x04, // RDLENGTH = 4
+		0x01, 0x02, 0x03, 0x04, // 1.2.3.4
+	}
+	f.Add(seedResp)
+
+	f.Fuzz(func(t *testing.T, data []byte) {
+		m, err := Unpack(data)
+		if err != nil {
+			return // error is fine; panic is not
+		}
+		_, err = Pack(m)
+		if err != nil {
+			t.Errorf("Pack after Unpack: %v", err)
+		}
+	})
+}