Introduce Fuzzing with jsFuzz and fix issues found by fuzzing

.github/workflows/fuzz.yml

@@ -0,0 +1,23 @@
+# https://gitlab.com/gitlab-org/security-products/analyzers/fuzzers/jsfuzz
+
+name: Fuzz
+
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+
+jobs:
+  fuzzing:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Setup Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: "16"
+
+    - run: npm ci
+    - run: npm run test:fuzz

.gitignore

@@ -11,3 +11,6 @@ isolate-*.log
 
 # flamebearer
 flamegraph.html
+
+# jsfuzz
+corpus/

package.json

@@ -23,6 +23,7 @@
     "test:cover:purejs": "npx nyc --no-clean npm run test:purejs",
     "test:cover:te": "npx nyc --no-clean npm run test:te",
     "test:deno": "deno test test/deno_test.ts",
+    "test:fuzz": "npm exec -- jsfuzz@git+https://gitlab.com/gitlab-org/security-products/analyzers/fuzzers/jsfuzz.git --fuzzTime 60 --no-versifier test/decode.jsfuzz.js corpus",
     "cover:clean": "rimraf .nyc_output coverage/",
     "cover:report": "npx nyc report --reporter=text-summary --reporter=html --reporter=json",
     "test:browser": "karma start --single-run",

src/DecodeError.ts

@@ -0,0 +1,16 @@
+
+export class DecodeError extends Error {
+  constructor(message: string) {
+    super(message);
+
+    // fix the prototype chain in a cross-platform way
+    const proto: typeof DecodeError.prototype = Object.create(DecodeError.prototype);
+    Object.setPrototypeOf(this, proto);
+
+    Object.defineProperty(this, "name", {
+      configurable: true,
+      enumerable: false,
+      value: DecodeError.name,
+    });
+  }
+}

src/Decoder.ts

@@ -4,6 +4,7 @@ import { getInt64, getUint64 } from "./utils/int";
 import { utf8DecodeJs, TEXT_DECODER_THRESHOLD, utf8DecodeTD } from "./utils/utf8";
 import { createDataView, ensureUint8Array } from "./utils/typedArrays";
 import { CachedKeyDecoder, KeyDecoder } from "./CachedKeyDecoder";
+import { DecodeError } from "./DecodeError";
 
 const enum State {
   ARRAY,
@@ -60,22 +61,6 @@ const DEFAULT_MAX_LENGTH = 0xffff_ffff; // uint32_max
 
 const sharedCachedKeyDecoder = new CachedKeyDecoder();
 
-export class DecodeError extends Error {
-  constructor(message: string) {
-    super(message);
-
-    // fix the prototype chain in a cross-platform way
-    const proto: typeof DecodeError.prototype = Object.create(DecodeError.prototype);
-    Object.setPrototypeOf(this, proto);
-
-    Object.defineProperty(this, "name", {
-      configurable: true,
-      enumerable: false,
-      value: DecodeError.name,
-    });
-  }
-}
-
 export class Decoder<ContextType = undefined> {
   private totalPos = 0;
   private pos = 0;
@@ -133,6 +118,10 @@ export class Decoder<ContextType = undefined> {
     return new RangeError(`Extra ${view.byteLength - pos} of ${view.byteLength} byte(s) found at buffer[${posToShow}]`);
   }
 
+  /**
+   * @throws {DecodeError}
+   * @throws {RangeError}
+   */
   public decode(buffer: ArrayLike<number> | BufferSource): unknown {
     this.reinitializeState();
     this.setBuffer(buffer);

src/index.ts

@@ -13,8 +13,9 @@ export { DecodeOptions };
 import { decodeAsync, decodeArrayStream, decodeMultiStream, decodeStream } from "./decodeAsync";
 export { decodeAsync, decodeArrayStream, decodeMultiStream, decodeStream };
 
-import { Decoder, DecodeError } from "./Decoder";
-export { Decoder, DecodeError };
+import { Decoder, DataViewIndexOutOfBoundsError } from "./Decoder";
+import { DecodeError } from "./DecodeError";
+export { Decoder, DecodeError, DataViewIndexOutOfBoundsError };
 
 import { Encoder } from "./Encoder";
 export { Encoder };

src/timestamp.ts

@@ -1,4 +1,5 @@
 // https://github.com/msgpack/msgpack/blob/master/spec.md#timestamp-extension-type
+import { DecodeError } from "./DecodeError";
 import { getInt64, setInt64 } from "./utils/int";
 
 export const EXT_TIMESTAMP = -1;
@@ -91,7 +92,7 @@ export function decodeTimestampToTimeSpec(data: Uint8Array): TimeSpec {
       return { sec, nsec };
     }
     default:
-      throw new Error(`Unrecognized data size for timestamp: ${data.length}`);
+      throw new DecodeError(`Unrecognized data size for timestamp (expected 4, 8, or 12): ${data.length}`);
   }
 }
 

test/decode.jsfuzz.js

@@ -0,0 +1,30 @@
+/* eslint-disable */
+const assert = require("assert");
+const { Decoder, encode, DecodeError } = require("../dist/index.js");
+
+/**
+ * @param {Buffer} bytes
+ * @returns {void}
+ */
+module.exports.fuzz = function fuzz(bytes) {
+  const decoder = new Decoder();
+  try {
+    decoder.decode(bytes);
+  } catch (e) {
+    if (e instanceof DecodeError) {
+      // ok
+    } else if (e instanceof RangeError) {
+      // ok
+    } else {
+      throw e;
+    }
+  }
+
+  // make sure the decoder instance is not broken
+  const object = {
+    foo: 1,
+    bar: 2,
+    baz: ["one", "two", "three"],
+  };
+  assert.deepStrictEqual(decoder.decode(encode(object)), object);
+}