Improve decodeBase64() to throw on invalid input rather than silently accept it

common/api-review/util.api.md

@@ -93,6 +93,14 @@ export function createSubscribe<T>(executor: Executor<T>, onNoObservers?: Execut
 // @public
 export const decode: (token: string) => DecodedToken;
 
+// Warning: (ae-missing-release-tag) "DecodeBase64StringError" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
+//
+// @public
+export class DecodeBase64StringError extends Error {
+    // (undocumented)
+    readonly name = "DecodeBase64StringError";
+}
+
 // Warning: (ae-missing-release-tag) "deepCopy" is exported by the package, but it is missing a release tag (@alpha, @beta, @public, or @internal)
 //
 // @public

packages/firestore/src/core/firestore_client.ts

@@ -41,7 +41,8 @@ import { Document } from '../model/document';
 import { DocumentKey } from '../model/document_key';
 import { Mutation } from '../model/mutation';
 import { toByteStreamReader } from '../platform/byte_stream_reader';
-import { newSerializer, newTextEncoder } from '../platform/serializer';
+import { newSerializer } from '../platform/serializer';
+import { newTextEncoder } from '../platform/text_serializer';
 import { Datastore } from '../remote/datastore';
 import {
   canUseNetwork,

packages/firestore/src/platform/base64.ts

@@ -15,13 +15,24 @@
  * limitations under the License.
  */
 
+import { Base64DecodeError } from '../util/base64_decode_error';
+
 // This file is only used under ts-node.
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 const platform = require(`./${process.env.TEST_PLATFORM ?? 'node'}/base64`);
 
 /** Converts a Base64 encoded string to a binary string. */
 export function decodeBase64(encoded: string): string {
-  return platform.decodeBase64(encoded);
+  const decoded = platform.decodeBase64(encoded);
+
+  // A quick sanity check as node and rn will not throw error if input is an
+  // invalid base64 string, e.g., "A===".
+  const expectedEncodedLength = 4 * Math.ceil(decoded.length / 3);
+  if (encoded.length !== expectedEncodedLength) {
+    throw new Base64DecodeError('Invalid base64 string');
+  }
+
+  return decoded;
 }
 
 /** Converts a binary string to a Base64 encoded string. */

packages/firestore/src/platform/browser/base64.ts

@@ -15,9 +15,19 @@
  * limitations under the License.
  */
 
+import { Base64DecodeError } from '../../util/base64_decode_error';
+
 /** Converts a Base64 encoded string to a binary string. */
 export function decodeBase64(encoded: string): string {
-  return atob(encoded);
+  try {
+    return atob(encoded);
+  } catch (e) {
+    if (e instanceof DOMException) {
+      throw new Base64DecodeError('Invalid base64 string: ' + e);
+    } else {
+      throw e;
+    }
+  }
 }
 
 /** Converts a binary string to a Base64 encoded string. */

packages/firestore/src/platform/browser/serializer.ts

@@ -22,17 +22,3 @@ import { JsonProtoSerializer } from '../../remote/serializer';
 export function newSerializer(databaseId: DatabaseId): JsonProtoSerializer {
   return new JsonProtoSerializer(databaseId, /* useProto3Json= */ true);
 }
-
-/**
- * An instance of the Platform's 'TextEncoder' implementation.
- */
-export function newTextEncoder(): TextEncoder {
-  return new TextEncoder();
-}
-
-/**
- * An instance of the Platform's 'TextDecoder' implementation.
- */
-export function newTextDecoder(): TextDecoder {
-  return new TextDecoder('utf-8');
-}

packages/firestore/src/platform/browser/text_serializer.ts

@@ -0,0 +1,30 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * An instance of the Platform's 'TextEncoder' implementation.
+ */
+export function newTextEncoder(): TextEncoder {
+  return new TextEncoder();
+}
+
+/**
+ * An instance of the Platform's 'TextDecoder' implementation.
+ */
+export function newTextDecoder(): TextDecoder {
+  return new TextDecoder('utf-8');
+}

packages/firestore/src/platform/browser_lite/text_serializer.ts

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export * from '../browser/text_serializer';

packages/firestore/src/platform/node/serializer.ts

@@ -16,25 +16,9 @@
  */
 
 /** Return the Platform-specific serializer monitor. */
-import { TextDecoder, TextEncoder } from 'util';
-
 import { DatabaseId } from '../../core/database_info';
 import { JsonProtoSerializer } from '../../remote/serializer';
 
 export function newSerializer(databaseId: DatabaseId): JsonProtoSerializer {
   return new JsonProtoSerializer(databaseId, /* useProto3Json= */ false);
 }
-
-/**
- * An instance of the Platform's 'TextEncoder' implementation.
- */
-export function newTextEncoder(): TextEncoder {
-  return new TextEncoder();
-}
-
-/**
- * An instance of the Platform's 'TextDecoder' implementation.
- */
-export function newTextDecoder(): TextDecoder {
-  return new TextDecoder('utf-8');
-}

packages/firestore/src/platform/node/text_serializer.ts

@@ -0,0 +1,32 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { TextDecoder, TextEncoder } from 'util';
+
+/**
+ * An instance of the Platform's 'TextEncoder' implementation.
+ */
+export function newTextEncoder(): TextEncoder {
+  return new TextEncoder();
+}
+
+/**
+ * An instance of the Platform's 'TextDecoder' implementation.
+ */
+export function newTextDecoder(): TextDecoder {
+  return new TextDecoder('utf-8');
+}

packages/firestore/src/platform/node_lite/text_serializer.ts

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export * from '../browser_lite/text_serializer';

packages/firestore/src/platform/rn/base64.ts

@@ -15,21 +15,31 @@
  * limitations under the License.
  */
 
-import { base64 } from '@firebase/util';
+import { base64, DecodeBase64StringError } from '@firebase/util';
+
+import { Base64DecodeError } from '../../util/base64_decode_error';
 
 // WebSafe uses a different URL-encoding safe alphabet that doesn't match
 // the encoding used on the backend.
 const WEB_SAFE = false;
 
 /** Converts a Base64 encoded string to a binary string. */
 export function decodeBase64(encoded: string): string {
-  return String.fromCharCode.apply(
-    null,
-    // We use `decodeStringToByteArray()` instead of `decodeString()` since
-    // `decodeString()` returns Unicode strings, which doesn't match the values
-    // returned by `atob()`'s Latin1 representation.
-    base64.decodeStringToByteArray(encoded, WEB_SAFE)
-  );
+  try {
+    return String.fromCharCode.apply(
+      null,
+      // We use `decodeStringToByteArray()` instead of `decodeString()` since
+      // `decodeString()` returns Unicode strings, which doesn't match the values
+      // returned by `atob()`'s Latin1 representation.
+      base64.decodeStringToByteArray(encoded, WEB_SAFE)
+    );
+  } catch (e) {
+    if (e instanceof DecodeBase64StringError) {
+      throw new Base64DecodeError('Invalid base64 string: ' + e);
+    } else {
+      throw e;
+    }
+  }
 }
 
 /** Converts a binary string to a Base64 encoded string. */

packages/firestore/src/platform/rn/serializer.ts

@@ -15,8 +15,4 @@
  * limitations under the License.
  */
 
-export {
-  newSerializer,
-  newTextEncoder,
-  newTextDecoder
-} from '../browser/serializer';
+export { newSerializer } from '../browser/serializer';

packages/firestore/src/platform/rn/text_serializer.ts

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export { newTextEncoder, newTextDecoder } from '../browser/text_serializer';

packages/firestore/src/platform/rn_lite/text_serializer.ts

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export * from '../browser_lite/text_serializer';

packages/firestore/src/platform/serializer.ts

@@ -15,45 +15,13 @@
  * limitations under the License.
  */
 
-import { isNode, isReactNative } from '@firebase/util';
-
 import { DatabaseId } from '../core/database_info';
 import { JsonProtoSerializer } from '../remote/serializer';
 
-import * as browser from './browser/serializer';
-import * as node from './node/serializer';
-import * as rn from './rn/serializer';
-
 // This file is only used under ts-node.
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 const platform = require(`./${process.env.TEST_PLATFORM ?? 'node'}/serializer`);
 
 export function newSerializer(databaseId: DatabaseId): JsonProtoSerializer {
   return platform.newSerializer(databaseId);
 }
-
-/**
- * An instance of the Platform's 'TextEncoder' implementation.
- */
-export function newTextEncoder(): TextEncoder {
-  if (isNode()) {
-    return node.newTextEncoder();
-  } else if (isReactNative()) {
-    return rn.newTextEncoder();
-  } else {
-    return browser.newTextEncoder();
-  }
-}
-
-/**
- * An instance of the Platform's 'TextDecoder' implementation.
- */
-export function newTextDecoder(): TextDecoder {
-  if (isNode()) {
-    return node.newTextDecoder() as TextDecoder;
-  } else if (isReactNative()) {
-    return rn.newTextDecoder();
-  } else {
-    return browser.newTextDecoder();
-  }
-}