fix(NODE-6124): utf8 validation is insufficiently strict

etc/rollup/rollup-plugin-require-vendor/require_vendor.mjs

@@ -1,9 +1,12 @@
 import MagicString from 'magic-string';
 
-const REQUIRE_POLYFILLS =
-  `const { TextEncoder, TextDecoder } = require('../vendor/text-encoding');
+const REQUIRE_WEB_UTILS_POLYFILLS =
+  `const { TextEncoder } = require('../vendor/text-encoding');
 const { encode: btoa, decode: atob } = require('../vendor/base64');\n`
 
+const REQUIRE_PARSE_UTF8_POLYFILLS = 
+  `const { TextDecoder } = require('../vendor/text-encoding');\n`;
+
 export class RequireVendor {
   /**
    * Take the compiled source code input; types are expected to already have been removed.
@@ -14,17 +17,24 @@ export class RequireVendor {
    * @returns {{ code: string; map: import('magic-string').SourceMap }}
    */
   transform(code, id) {
-    if (!id.includes('web_byte_utils')) {
-      return;
-    }
+    if (id.includes('parse_utf8')) {
+      // MagicString lets us edit the source code and still generate an accurate source map
+      const magicString = new MagicString(code);
+      magicString.prepend(REQUIRE_PARSE_UTF8_POLYFILLS);
 
-    // MagicString lets us edit the source code and still generate an accurate source map
-    const magicString = new MagicString(code);
-    magicString.prepend(REQUIRE_POLYFILLS);
+      return {
+        code: magicString.toString(),
+        map: magicString.generateMap({ hires: true })
+      };
+    } else if (id.includes('web_byte_utils')) {
+      // MagicString lets us edit the source code and still generate an accurate source map
+      const magicString = new MagicString(code);
+      magicString.prepend(REQUIRE_WEB_UTILS_POLYFILLS);
 
-    return {
-      code: magicString.toString(),
-      map: magicString.generateMap({ hires: true })
-    };
+      return {
+        code: magicString.toString(),
+        map: magicString.generateMap({ hires: true })
+      };
+    }
   }
 }

src/binary.ts

@@ -224,8 +224,8 @@ export class Binary extends BSONValue {
     if (encoding === 'hex') return ByteUtils.toHex(this.buffer.subarray(0, this.position));
     if (encoding === 'base64') return ByteUtils.toBase64(this.buffer.subarray(0, this.position));
     if (encoding === 'utf8' || encoding === 'utf-8')
-      return ByteUtils.toUTF8(this.buffer, 0, this.position);
-    return ByteUtils.toUTF8(this.buffer, 0, this.position);
+      return ByteUtils.toUTF8(this.buffer, 0, this.position, false);
+    return ByteUtils.toUTF8(this.buffer, 0, this.position, false);
   }
 
   /** @internal */

src/parse_utf8.ts

@@ -0,0 +1,35 @@
+import { BSONError } from './error';
+
+type TextDecoder = {
+  readonly encoding: string;
+  readonly fatal: boolean;
+  readonly ignoreBOM: boolean;
+  decode(input?: Uint8Array): string;
+};
+type TextDecoderConstructor = {
+  new (label: 'utf8', options: { fatal: boolean; ignoreBOM?: boolean }): TextDecoder;
+};
+
+// parse utf8 globals
+declare const TextDecoder: TextDecoderConstructor;
+let TextDecoderFatal: TextDecoder;
+let TextDecoderNonFatal: TextDecoder;
+
+/**
+ * Determines if the passed in bytes are valid utf8
+ * @param bytes - An array of 8-bit bytes. Must be indexable and have length property
+ * @param start - The index to start validating
+ * @param end - The index to end validating
+ */
+export function parseUtf8(buffer: Uint8Array, start: number, end: number, fatal: boolean): string {
+  if (fatal) {
+    TextDecoderFatal ??= new TextDecoder('utf8', { fatal: true });
+    try {
+      return TextDecoderFatal.decode(buffer.subarray(start, end));
+    } catch (cause) {
+      throw new BSONError('Invalid UTF-8 string in BSON document');
+    }
+  }
+  TextDecoderNonFatal ??= new TextDecoder('utf8', { fatal: false });
+  return TextDecoderNonFatal.decode(buffer.subarray(start, end));
+}

src/parser/deserializer.ts

@@ -15,7 +15,6 @@ import { BSONRegExp } from '../regexp';
 import { BSONSymbol } from '../symbol';
 import { Timestamp } from '../timestamp';
 import { BSONDataView, ByteUtils } from '../utils/byte_utils';
-import { validateUtf8 } from '../validate_utf8';
 
 /** @public */
 export interface DeserializeOptions {
@@ -236,7 +235,7 @@ function deserializeObject(
     if (i >= buffer.byteLength) throw new BSONError('Bad BSON Document: illegal CString');
 
     // Represents the key
-    const name = isArray ? arrayIndex++ : ByteUtils.toUTF8(buffer, index, i);
+    const name = isArray ? arrayIndex++ : ByteUtils.toUTF8(buffer, index, i, false);
 
     // shouldValidateKey is true if the key should be validated, false otherwise
     let shouldValidateKey = true;
@@ -266,7 +265,7 @@ function deserializeObject(
       ) {
         throw new BSONError('bad string length in bson');
       }
-      value = getValidatedString(buffer, index, index + stringSize - 1, shouldValidateKey);
+      value = ByteUtils.toUTF8(buffer, index, index + stringSize - 1, shouldValidateKey);
       index = index + stringSize;
     } else if (elementType === constants.BSON_DATA_OID) {
       const oid = ByteUtils.allocate(12);
@@ -476,7 +475,7 @@ function deserializeObject(
       // If are at the end of the buffer there is a problem with the document
       if (i >= buffer.length) throw new BSONError('Bad BSON Document: illegal CString');
       // Return the C string
-      const source = ByteUtils.toUTF8(buffer, index, i);
+      const source = ByteUtils.toUTF8(buffer, index, i, false);
       // Create the regexp
       index = i + 1;
 
@@ -489,7 +488,7 @@ function deserializeObject(
       // If are at the end of the buffer there is a problem with the document
       if (i >= buffer.length) throw new BSONError('Bad BSON Document: illegal CString');
       // Return the C string
-      const regExpOptions = ByteUtils.toUTF8(buffer, index, i);
+      const regExpOptions = ByteUtils.toUTF8(buffer, index, i, false);
       index = i + 1;
 
       // For each option add the corresponding one for javascript
@@ -521,7 +520,7 @@ function deserializeObject(
       // If are at the end of the buffer there is a problem with the document
       if (i >= buffer.length) throw new BSONError('Bad BSON Document: illegal CString');
       // Return the C string
-      const source = ByteUtils.toUTF8(buffer, index, i);
+      const source = ByteUtils.toUTF8(buffer, index, i, false);
       index = i + 1;
 
       // Get the start search index
@@ -533,7 +532,7 @@ function deserializeObject(
       // If are at the end of the buffer there is a problem with the document
       if (i >= buffer.length) throw new BSONError('Bad BSON Document: illegal CString');
       // Return the C string
-      const regExpOptions = ByteUtils.toUTF8(buffer, index, i);
+      const regExpOptions = ByteUtils.toUTF8(buffer, index, i, false);
       index = i + 1;
 
       // Set the object
@@ -551,7 +550,7 @@ function deserializeObject(
       ) {
         throw new BSONError('bad string length in bson');
       }
-      const symbol = getValidatedString(buffer, index, index + stringSize - 1, shouldValidateKey);
+      const symbol = ByteUtils.toUTF8(buffer, index, index + stringSize - 1, shouldValidateKey);
       value = promoteValues ? symbol : new BSONSymbol(symbol);
       index = index + stringSize;
     } else if (elementType === constants.BSON_DATA_TIMESTAMP) {
@@ -587,7 +586,7 @@ function deserializeObject(
       ) {
         throw new BSONError('bad string length in bson');
       }
-      const functionString = getValidatedString(
+      const functionString = ByteUtils.toUTF8(
         buffer,
         index,
         index + stringSize - 1,
@@ -626,7 +625,7 @@ function deserializeObject(
       }
 
       // Javascript function
-      const functionString = getValidatedString(
+      const functionString = ByteUtils.toUTF8(
         buffer,
         index,
         index + stringSize - 1,
@@ -673,12 +672,7 @@ function deserializeObject(
       )
         throw new BSONError('bad string length in bson');
       // Namespace
-      if (validation != null && validation.utf8) {
-        if (!validateUtf8(buffer, index, index + stringSize - 1)) {
-          throw new BSONError('Invalid UTF-8 string in BSON document');
-        }
-      }
-      const namespace = ByteUtils.toUTF8(buffer, index, index + stringSize - 1);
+      const namespace = ByteUtils.toUTF8(buffer, index, index + stringSize - 1, shouldValidateKey);
       // Update parse index position
       index = index + stringSize;
 
@@ -728,24 +722,3 @@ function deserializeObject(
 
   return object;
 }
-
-function getValidatedString(
-  buffer: Uint8Array,
-  start: number,
-  end: number,
-  shouldValidateUtf8: boolean
-) {
-  const value = ByteUtils.toUTF8(buffer, start, end);
-  // if utf8 validation is on, do the check
-  if (shouldValidateUtf8) {
-    for (let i = 0; i < value.length; i++) {
-      if (value.charCodeAt(i) === 0xfffd) {
-        if (!validateUtf8(buffer, start, end)) {
-          throw new BSONError('Invalid UTF-8 string in BSON document');
-        }
-        break;
-      }
-    }
-  }
-  return value;
-}

src/utils/byte_utils.ts

@@ -26,7 +26,7 @@ export type ByteUtils = {
   /** Create a Uint8Array containing utf8 code units from a string */
   fromUTF8: (text: string) => Uint8Array;
   /** Create a string from utf8 code units */
-  toUTF8: (buffer: Uint8Array, start: number, end: number) => string;
+  toUTF8: (buffer: Uint8Array, start: number, end: number, fatal: boolean) => string;
   /** Get the utf8 code unit count from a string if it were to be transformed to utf8 */
   utf8ByteLength: (input: string) => number;
   /** Encode UTF8 bytes generated from `source` string into `destination` at byteOffset. Returns the number of bytes encoded. */

src/utils/node_byte_utils.ts

@@ -1,4 +1,5 @@
 import { BSONError } from '../error';
+import { parseUtf8 } from '../parse_utf8';
 
 type NodeJsEncoding = 'base64' | 'hex' | 'utf8' | 'binary';
 type NodeJsBuffer = ArrayBufferView &
@@ -125,8 +126,16 @@ export const nodeJsByteUtils = {
     return Buffer.from(text, 'utf8');
   },
 
-  toUTF8(buffer: Uint8Array, start: number, end: number): string {
-    return nodeJsByteUtils.toLocalBufferType(buffer).toString('utf8', start, end);
+  toUTF8(buffer: Uint8Array, start: number, end: number, fatal: boolean): string {
+    const value = nodeJsByteUtils.toLocalBufferType(buffer).toString('utf8', start, end);
+    if (fatal) {
+      for (let i = 0; i < value.length; i++) {
+        if (value.charCodeAt(i) === 0xfffd) {
+          parseUtf8(buffer, start, end, fatal);
+        }
+      }
+    }
+    return value;
   },
 
   utf8ByteLength(input: string): number {

src/utils/web_byte_utils.ts

@@ -1,14 +1,5 @@
 import { BSONError } from '../error';
-
-type TextDecoder = {
-  readonly encoding: string;
-  readonly fatal: boolean;
-  readonly ignoreBOM: boolean;
-  decode(input?: Uint8Array): string;
-};
-type TextDecoderConstructor = {
-  new (label: 'utf8', options: { fatal: boolean; ignoreBOM?: boolean }): TextDecoder;
-};
+import { parseUtf8 } from '../parse_utf8';
 
 type TextEncoder = {
   readonly encoding: string;
@@ -19,7 +10,6 @@ type TextEncoderConstructor = {
 };
 
 // Web global
-declare const TextDecoder: TextDecoderConstructor;
 declare const TextEncoder: TextEncoderConstructor;
 declare const atob: (base64: string) => string;
 declare const btoa: (binary: string) => string;
@@ -172,8 +162,8 @@ export const webByteUtils = {
     return new TextEncoder().encode(text);
   },
 
-  toUTF8(uint8array: Uint8Array, start: number, end: number): string {
-    return new TextDecoder('utf8', { fatal: false }).decode(uint8array.slice(start, end));
+  toUTF8(uint8array: Uint8Array, start: number, end: number, fatal: boolean): string {
+    return parseUtf8(uint8array, start, end, fatal);
   },
 
   utf8ByteLength(input: string): number {

test/node/byte_utils.test.ts

@@ -8,6 +8,7 @@ import { webByteUtils } from '../../src/utils/web_byte_utils';
 import * as sinon from 'sinon';
 import { loadCJSModuleBSON, loadReactNativeCJSModuleBSON, loadESModuleBSON } from '../load_bson';
 import * as crypto from 'node:crypto';
+import { utf8WebPlatformSpecTests } from './data/utf8_wpt_error_cases';
 
 type ByteUtilTest<K extends keyof ByteUtils> = {
   name: string;
@@ -400,20 +401,32 @@ const fromUTF8Tests: ByteUtilTest<'fromUTF8'>[] = [
 const toUTF8Tests: ByteUtilTest<'toUTF8'>[] = [
   {
     name: 'should create utf8 string from buffer input',
-    inputs: [Buffer.from('abc\u{1f913}', 'utf8')],
+    inputs: [Buffer.from('abc\u{1f913}', 'utf8'), 0, 7, false],
     expectation({ output, error }) {
       expect(error).to.be.null;
       expect(output).to.deep.equal(Buffer.from('abc\u{1f913}', 'utf8').toString('utf8'));
     }
   },
   {
     name: 'should return empty string for empty buffer input',
-    inputs: [Buffer.alloc(0)],
+    inputs: [Buffer.alloc(0), 0, 0, false],
     expectation({ output, error }) {
       expect(error).to.be.null;
       expect(output).to.be.a('string').with.lengthOf(0);
     }
-  }
+  },
+  ...utf8WebPlatformSpecTests.map(t => ({
+    name: t.name,
+    inputs: [Uint8Array.from(t.input), 0, t.input.length, true] as [
+      buffer: Uint8Array,
+      start: number,
+      end: number,
+      fatal: boolean
+    ],
+    expectation({ error }) {
+      expect(error).to.match(/Invalid UTF-8 string in BSON document/i);
+    }
+  }))
 ];
 const utf8ByteLengthTests: ByteUtilTest<'utf8ByteLength'>[] = [
   {