fix: MaxRecordSize of 10 KiB

See rationale:
ipfs/specs#319 (comment)

errors.go

@@ -35,3 +35,10 @@ var ErrPublicKeyMismatch = errors.New("public key in record did not match expect
 
 // ErrBadRecord should be returned when an ipns record cannot be unmarshalled
 var ErrBadRecord = errors.New("record could not be unmarshalled")
+
+// 10 KiB limit defined in https://github.com/ipfs/specs/pull/319
+const MaxRecordSize int = 10 << (10 * 1)
+
+// ErrRecordSize should be returned when an ipns record is
+// invalid due to being too big
+var ErrRecordSize = errors.New("record exceeds allowed size limit")

ipns.go

@@ -132,6 +132,11 @@ func createCborDataForIpnsEntry(e *pb.IpnsEntry) ([]byte, error) {
 
 // Validates validates the given IPNS entry against the given public key.
 func Validate(pk ic.PubKey, entry *pb.IpnsEntry) error {
+	// Make sure max size is respected
+	if entry.Size() > MaxRecordSize {
+		return ErrRecordSize
+	}
+
 	// Check the ipns record signature with the public key
 	if entry.GetSignatureV2() == nil {
 		// always error if no valid signature could be found

validate_test.go

@@ -274,6 +274,26 @@ func TestSignatureV1Ignored(t *testing.T) {
 	}
 }
 
+func TestMaxSizeValidate(t *testing.T) {
+	goodeol := time.Now().Add(time.Hour)
+
+	sk, pk, err := crypto.GenerateEd25519Key(rand.New(rand.NewSource(42)))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create record over the max size (value+other fields)
+	value := make([]byte, MaxRecordSize)
+	entry, err := Create(sk, value, 1, goodeol, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Must fail with ErrRecordSize
+	if err := Validate(pk, entry); !errors.Is(err, ErrRecordSize) {
+		t.Fatal(err)
+	}
+}
+
 func TestCborDataCanonicalization(t *testing.T) {
 	goodeol := time.Now().Add(time.Hour)