multi: handle all blinding point validation in ValidateParsedPayloadTypes

This commit moves all our validation related to the presence of fields
into ValidateParsedPayloadTypes so that we can handle them in a single
place. We draw the distinction between:
- Validation of the payload (and the context within it's being parsed,
  final hop / blinded hop etc)
- Processing and validation of encrypted data, where we perform
  additional cryptographic operations and validate that the fields
  contained in the blob are valid.

This helps draw the line more clearly between the two validation types,
rather than splitting some payload-releated blinded hop processing
into the encrypted data processing part. The downside of this approach
(vs doing the blinded path payload check _after_ payload validation)
is that we have to pass additional context into payload validation
(ie, whether we got a blinding point in our UpdateAddHtlc - as we
already do for isFinalHop).

htlcswitch/hop/payload_test.go

@@ -26,6 +26,7 @@ type decodePayloadTest struct {
 	name               string
 	payload            []byte
 	isFinalHop         bool
+	updateAddBlinded   bool
 	expErr             error
 	expCustomRecords   map[uint64][]byte
 	shouldHaveMPP      bool
@@ -271,8 +272,9 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:       "intermediate hop with encrypted data",
-		isFinalHop: false,
+		name:             "intermediate hop with encrypted data",
+		isFinalHop:       false,
+		updateAddBlinded: true,
 		payload: []byte{
 			// encrypted data
 			0x0a, 0x03, 0x03, 0x02, 0x01,
@@ -365,8 +367,9 @@ var decodePayloadTests = []decodePayloadTest{
 		shouldHaveTotalAmt: true,
 	},
 	{
-		name:       "final blinded hop with total amount",
-		isFinalHop: true,
+		name:             "final blinded hop with total amount",
+		isFinalHop:       true,
+		updateAddBlinded: true,
 		payload: []byte{
 			// amount
 			0x02, 0x00,
@@ -378,8 +381,9 @@ var decodePayloadTests = []decodePayloadTest{
 		shouldHaveEncData: true,
 	},
 	{
-		name:       "final blinded missing amt",
-		isFinalHop: true,
+		name:             "final blinded missing amt",
+		isFinalHop:       true,
+		updateAddBlinded: true,
 		payload: []byte{
 			// cltv
 			0x04, 0x00,
@@ -394,8 +398,9 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:       "final blinded missing cltv",
-		isFinalHop: true,
+		name:             "final blinded missing cltv",
+		isFinalHop:       true,
+		updateAddBlinded: true,
 		payload: []byte{
 			// amount
 			0x02, 0x00,
@@ -410,8 +415,9 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:       "intermediate blinded has amount",
-		isFinalHop: false,
+		name:             "intermediate blinded has amount",
+		isFinalHop:       false,
+		updateAddBlinded: true,
 		payload: []byte{
 			// amount
 			0x02, 0x00,
@@ -425,8 +431,9 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:       "intermediate blinded has expiry",
-		isFinalHop: false,
+		name:             "intermediate blinded has expiry",
+		isFinalHop:       false,
+		updateAddBlinded: true,
 		payload: []byte{
 			// cltv
 			0x04, 0x00,
@@ -439,6 +446,67 @@ var decodePayloadTests = []decodePayloadTest{
 			FinalHop:  false,
 		},
 	},
+	{
+		name:       "update add blinding no data",
+		isFinalHop: false,
+		payload: []byte{
+			// cltv
+			0x04, 0x00,
+		},
+		updateAddBlinded: true,
+		expErr: hop.ErrInvalidPayload{
+			Type:      record.EncryptedDataOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  false,
+		},
+	},
+	{
+		name:       "onion blinding point no data",
+		isFinalHop: false,
+		payload: append([]byte{
+			// blinding point (type / length)
+			0x0c, 0x21,
+		},
+			// blinding point (value)
+			testPubKey.SerializeCompressed()...,
+		),
+		expErr: hop.ErrInvalidPayload{
+			Type:      record.EncryptedDataOnionType,
+			Violation: hop.OmittedViolation,
+			FinalHop:  false,
+		},
+	},
+	{
+		name:       "encrypted data no blinding",
+		isFinalHop: false,
+		payload: []byte{
+			// encrypted data
+			0x0a, 0x03, 0x03, 0x02, 0x01,
+		},
+		expErr: hop.ErrInvalidPayload{
+			Type:      record.EncryptedDataOnionType,
+			Violation: hop.IncludedViolation,
+		},
+	},
+	{
+		name:             "both blinding points",
+		isFinalHop:       false,
+		updateAddBlinded: true,
+		payload: append([]byte{
+			// encrypted data
+			0x0a, 0x03, 0x03, 0x02, 0x01,
+			// blinding point (type / length)
+			0x0c, 0x21,
+		},
+			// blinding point (value)
+			testPubKey.SerializeCompressed()...,
+		),
+		expErr: hop.ErrInvalidPayload{
+			Type:      record.BlindingPointOnionType,
+			Violation: hop.IncludedViolation,
+			FinalHop:  false,
+		},
+	},
 }
 
 // TestDecodeHopPayloadRecordValidation asserts that parsing the payloads in the
@@ -481,6 +549,7 @@ func testDecodeHopPayloadValidation(t *testing.T, test decodePayloadTest) {
 
 	p, _, err := hop.NewPayloadFromReader(
 		bytes.NewReader(test.payload), test.isFinalHop,
+		test.updateAddBlinded,
 	)
 	if !reflect.DeepEqual(test.expErr, err) {
 		t.Fatalf("expected error mismatch, want: %v, got: %v",