Malformed records or unknown records are now ignored

Previously there was a custom record which just hold the raw data.

package.json

@@ -58,17 +58,17 @@
   },
   "devDependencies": {
     "@types/debug": "^4.1.5",
-    "@types/jest": "^26.0.15",
-    "@types/node": "~10.17.47",
-    "@typescript-eslint/eslint-plugin": "^4.8.2",
-    "@typescript-eslint/parser": "^4.8.2",
-    "eslint": "^7.14.0",
+    "@types/jest": "^26.0.16",
+    "@types/node": "~10.17.48",
+    "@typescript-eslint/eslint-plugin": "^4.9.0",
+    "@typescript-eslint/parser": "^4.9.0",
+    "eslint": "^7.15.0",
     "jest": "^26.6.3",
     "rimraf": "^3.0.2",
-    "semver": "^7.3.2",
+    "semver": "^7.3.4",
     "ts-jest": "^26.4.4",
-    "ts-node": "^9.0.0",
-    "typedoc": "0.20.0-beta.17",
+    "ts-node": "^9.1.0",
+    "typedoc": "0.20.0-beta.24",
     "typescript": "^4.1.2"
   }
 }

src/coder/DNSPacket.ts

@@ -63,6 +63,11 @@ export interface DecodedData<T> {
   readBytes: number;
 }
 
+export interface OptionalDecodedData<T> {
+  data?: T;
+  readBytes: number;
+}
+
 export interface DNSQueryDefinition {
   questions: Question[];
   answers?: ResourceRecord[]; // list of known-answers
@@ -496,10 +501,10 @@ export class DNSPacket {
     const additionalsLength = buffer.readUInt16BE(offset);
     offset += 2;
 
-    const questions: Question[] = new Array(questionLength);
-    const answers: ResourceRecord[] = new Array(answerLength);
-    const authorities: ResourceRecord[] = new Array(authoritiesLength);
-    const additionals: ResourceRecord[] = new Array(additionalsLength);
+    const questions: Question[] = [];
+    const answers: ResourceRecord[] = [];
+    const authorities: ResourceRecord[] = [];
+    const additionals: ResourceRecord[] = [];
 
 
     offset += DNSPacket.decodeList(context, labelCoder, buffer, offset, questionLength, Question.decode.bind(Question), questions);
@@ -552,13 +557,16 @@ export class DNSPacket {
   }
 
   private static decodeList<T>(context: AddressInfo, coder: DNSLabelCoder, buffer: Buffer, offset: number,
-    length: number, decoder: (context: AddressInfo, coder: DNSLabelCoder, buffer: Buffer, offset: number) => DecodedData<T>, destination: T[]): number {
+    length: number, decoder: (context: AddressInfo, coder: DNSLabelCoder, buffer: Buffer, offset: number) => OptionalDecodedData<T>, destination: T[]): number {
     const oldOffset = offset;
 
     for (let i = 0; i < length; i++) {
       const decoded = decoder(context, coder, buffer, offset);
       offset += decoded.readBytes;
-      destination[i] = decoded.data;
+
+      if (decoded.data) { // if the rdata is not supported by us or we encountered an parsing error, we ignore the record
+        destination.push(decoded.data);
+      }
     }
 
     return offset - oldOffset;

src/coder/ResourceRecord.spec.ts

@@ -1,4 +1,4 @@
-import { RClass, RType } from "./DNSPacket";
+import { RType } from "./DNSPacket";
 import { AAAARecord } from "./records/AAAARecord";
 import { ARecord } from "./records/ARecord";
 import { CNAMERecord } from "./records/CNAMERecord";
@@ -7,7 +7,6 @@ import { OPTOption, OPTRecord } from "./records/OPTRecord";
 import { PTRRecord } from "./records/PTRRecord";
 import { SRVRecord } from "./records/SRVRecord";
 import { TXTRecord } from "./records/TXTRecord";
-import { UnsupportedOrMalformedRecord } from "./records/UnsupportedOrMalformedRecord";
 import { ResourceRecord } from "./ResourceRecord";
 import { runRecordEncodingTest } from "./test-utils";
 
@@ -60,14 +59,4 @@ describe(ResourceRecord, () => {
     runRecordEncodingTest(new TXTRecord("test.local.", [Buffer.from("key=value"), Buffer.from("key2=value2")]));
   });
 
-  it("should encode unsupported record", () => {
-    runRecordEncodingTest(new UnsupportedOrMalformedRecord({
-      type: 99,
-      class: RClass.IN,
-      name: "test.local.",
-      ttl: 250,
-      flushFlag: false,
-    }, Buffer.from("foo")));
-  });
-
 });

src/coder/ResourceRecord.ts

@@ -4,7 +4,7 @@ import { AddressInfo } from "net";
 import { dnsLowerCase } from "../util/dns-equal";
 import { dnsTypeToString } from "./dns-string-utils";
 import { DNSLabelCoder, NonCompressionLabelCoder } from "./DNSLabelCoder";
-import { DecodedData, DNSRecord, RClass, RType } from "./DNSPacket";
+import { DecodedData, DNSRecord, OptionalDecodedData, RClass, RType } from "./DNSPacket";
 
 const debug = createDebug("ciao:decoder");
 
@@ -25,7 +25,6 @@ export type RRDecoder = (coder: DNSLabelCoder, header: RecordRepresentation, buf
 export abstract class ResourceRecord implements DNSRecord { // RFC 1035 4.1.3.
 
   public static readonly typeToRecordDecoder: Map<RType, RRDecoder> = new Map();
-  public static unsupportedOrMalformedRecordDecoder: RRDecoder;
 
   private static readonly FLUSH_MASK = 0x8000; // 2 bytes, first bit set
   private static readonly NOT_FLUSH_MASK = 0x7FFF;
@@ -165,14 +164,18 @@ export abstract class ResourceRecord implements DNSRecord { // RFC 1035 4.1.3.
     return `RR ${this.name} ${this.type} ${this.class} ${this.dataAsString()}`;
   }
 
-  public static decode(context: AddressInfo, coder: DNSLabelCoder, buffer: Buffer, offset: number): DecodedData<ResourceRecord> {
+  public static decode(context: AddressInfo, coder: DNSLabelCoder, buffer: Buffer, offset: number): OptionalDecodedData<ResourceRecord> {
     const oldOffset = offset;
 
     const decodedHeader = this.decodeRecordHeader(coder, buffer, offset);
     offset += decodedHeader.readBytes;
 
     const header = decodedHeader.data;
-    const rrDecoder = this.typeToRecordDecoder.get(header.type) ?? ResourceRecord.unsupportedOrMalformedRecordDecoder;
+    const rrDecoder = this.typeToRecordDecoder.get(header.type);
+
+    if (!rrDecoder) {
+      return { readBytes: (offset + header.rDataLength) - oldOffset };
+    }
 
     coder.initRRLocation(oldOffset, offset, header.rDataLength); // defines record offset and rdata offset for local compression
 
@@ -183,8 +186,10 @@ export abstract class ResourceRecord implements DNSRecord { // RFC 1035 4.1.3.
       // we slice the buffer (below), so out of bounds error are instantly detected
       decodedRecord = rrDecoder(coder, header, rdata, offset);
     } catch (error) {
-      debug(`Received malformed rdata section for ${dnsTypeToString(header.type)} ${header.name} ${header.ttl} from ${context.address}:${context.port}: ${error.stack}`);
-      decodedRecord = ResourceRecord.unsupportedOrMalformedRecordDecoder(coder, header, rdata, offset);
+      debug(`Received malformed rdata section for ${dnsTypeToString(header.type)} ${header.name} ${header.ttl} \
+from ${context.address}:${context.port} with data '${rdata.slice(offset).toString("hex")}': ${error.stack}`);
+
+      return { readBytes: (offset + header.rDataLength) - oldOffset };
     }
     offset += decodedRecord.readBytes;
 

src/coder/records/index.ts

@@ -8,7 +8,6 @@ import { OPTRecord } from "./OPTRecord";
 import { PTRRecord } from "./PTRRecord";
 import { SRVRecord } from "./SRVRecord";
 import { TXTRecord } from "./TXTRecord";
-import { UnsupportedOrMalformedRecord } from "./UnsupportedOrMalformedRecord";
 
 ResourceRecord.typeToRecordDecoder.set(RType.AAAA, AAAARecord.decodeData);
 ResourceRecord.typeToRecordDecoder.set(RType.A, ARecord.decodeData);
@@ -18,4 +17,3 @@ ResourceRecord.typeToRecordDecoder.set(RType.PTR, PTRRecord.decodeData);
 ResourceRecord.typeToRecordDecoder.set(RType.SRV, SRVRecord.decodeData);
 ResourceRecord.typeToRecordDecoder.set(RType.OPT, OPTRecord.decodeData);
 ResourceRecord.typeToRecordDecoder.set(RType.TXT, TXTRecord.decodeData);
-ResourceRecord.unsupportedOrMalformedRecordDecoder = UnsupportedOrMalformedRecord.decodeData;

src/coder/test-utils.ts

@@ -29,7 +29,8 @@ export function runRecordEncodingTest(record: Question | ResourceRecord, legacyU
   expect(decodedRecord.readBytes).toBe(buffer.length);
 
   //
-  const record2 = decodedRecord.data;
+  const record2 = decodedRecord.data!;
+  expect(record2).toBeDefined();
 
   coder = new DNSLabelCoder(legacyUnicast);