Snapshot picked files into memory-backed Files to prevent request queue poisoning

src/libs/snapshotPickedFile/index.native.ts

@@ -0,0 +1,12 @@
+/**
+ * Native keeps the picked File as-is: there is no IndexedDB blob path to poison, and the
+ * File polyfill has no arrayBuffer. Only rename when the cleaned name differs.
+ */
+function snapshotPickedFile(file: File, name: string): Promise<File> {
+    if (file.name !== name) {
+        return Promise.resolve(new File([file], name, {type: file.type}));
+    }
+    return Promise.resolve(file);
+}
+
+export default snapshotPickedFile;

src/libs/snapshotPickedFile/index.ts

@@ -0,0 +1,11 @@
+/**
+ * Copies a picked file's bytes into a memory-backed File. A picked File only references its OS
+ * file, so if that file is modified or deleted before the queued request is persisted, the
+ * IndexedDB write fails with "Failed to write blobs" and poisons the persisted request queue.
+ * Rejects when the backing file is already unreadable.
+ */
+async function snapshotPickedFile(file: File, name: string): Promise<File> {
+    return new File([await file.arrayBuffer()], name, {type: file.type, lastModified: file.lastModified});
+}
+
+export default snapshotPickedFile;

src/libs/validateAttachmentFile.ts

@@ -4,6 +4,7 @@ import type {FileObject} from '@src/types/utils/Attachment';
 import type {ValueOf} from 'type-fest';
 
 import {cleanFileName, hasHeicOrHeifExtension, isValidReceiptExtension, normalizeFileObject, validateImageForCorruption} from './fileDownload/FileUtils';
+import snapshotPickedFile from './snapshotPickedFile';
 
 type ValidateAttachmentValidResult = {
     isValid: true;
@@ -67,12 +68,16 @@ async function validateAttachmentFile(file: FileObject, item?: DataTransferItem,
          */
         let updatedFile = normalizedFile;
         const cleanName = cleanFileName(updatedFile.name);
-        if (updatedFile.name !== cleanName) {
-            updatedFile = new File([updatedFile], cleanName, {type: updatedFile.type});
+        // On web this snapshots the bytes into a memory-backed File so a later change to the OS file
+        // can't invalidate the queued request (see snapshotPickedFile); on native it only cleans the name.
+        try {
+            updatedFile = await snapshotPickedFile(updatedFile, cleanName);
+        } catch {
+            // The backing file was already modified or deleted since it was picked.
+            return {isValid: false, error: CONST.FILE_VALIDATION_ERRORS.FILE_INVALID};
         }
-        // Read the superseded URI from normalizedFile: when the name needed cleaning, updatedFile was
-        // reassigned to a fresh File that doesn't carry the custom .uri property, so reading it there
-        // would skip the revoke exactly for cleaned filenames (e.g. default macOS screenshot names).
+        // Read the superseded URI from normalizedFile: updatedFile is always a fresh File that
+        // doesn't carry the custom .uri property.
         const previousUri = normalizedFile.uri;
         const inputSource = URL.createObjectURL(updatedFile);
         if (previousUri && previousUri !== inputSource && previousUri.startsWith('blob:')) {

tests/unit/ValidateAttachmentFileSnapshotTest.ts

@@ -0,0 +1,67 @@
+import validateAttachmentFile from '@libs/validateAttachmentFile';
+
+import type {FileObject} from '@src/types/utils/Attachment';
+
+import CONST from '../../src/CONST';
+import * as FileUtils from '../../src/libs/fileDownload/FileUtils';
+
+// Jest resolves the .native variant of platform-split modules; force the web implementation
+// since the OS-file snapshot behavior under test is web-only.
+jest.mock('@src/libs/snapshotPickedFile', () => jest.requireActual<{default: (file: File, name: string) => Promise<File>}>('@src/libs/snapshotPickedFile/index.ts'));
+
+// Mock only normalizeFileObject and validateImageForCorruption; keep the rest real
+jest.mock('@src/libs/fileDownload/FileUtils', () => {
+    const actual = jest.requireActual<typeof FileUtils>('@src/libs/fileDownload/FileUtils');
+    return {
+        ...actual,
+        normalizeFileObject: jest.fn(),
+        validateImageForCorruption: jest.fn(),
+    };
+});
+
+const mockFileUtils = jest.mocked(FileUtils);
+
+describe('validateAttachmentFile OS-backed file snapshot (web)', () => {
+    beforeEach(() => {
+        jest.clearAllMocks();
+        mockFileUtils.normalizeFileObject.mockImplementation(async (file) => file);
+        mockFileUtils.validateImageForCorruption.mockResolvedValue(undefined);
+    });
+
+    it('snapshots the picked file bytes into a new memory-backed File', async () => {
+        const createObjectURLSpy = jest.spyOn(URL, 'createObjectURL').mockReturnValue('blob:new-url');
+        try {
+            const file: FileObject = new File([new Blob(['content'], {type: 'text/plain'})], 'image.png', {type: 'image/png'});
+            // The RN File polyfill in Jest has no arrayBuffer; emulate the web File API.
+            const arrayBufferSpy = jest.fn().mockResolvedValue(new ArrayBuffer(7));
+            Object.defineProperty(file, 'arrayBuffer', {value: arrayBufferSpy, configurable: true});
+
+            const result = await validateAttachmentFile(file);
+
+            expect(result.isValid).toBe(true);
+            if (!result.isValid) {
+                throw new Error('validateAttachmentFile should return a valid result');
+            }
+            expect(arrayBufferSpy).toHaveBeenCalled();
+            // The returned File must be a fresh memory-backed copy, not the OS-backed original.
+            expect(result.file).not.toBe(file);
+        } finally {
+            createObjectURLSpy.mockRestore();
+        }
+    });
+
+    it('returns FILE_INVALID when the picked file can no longer be read (deleted or modified on disk)', async () => {
+        const file: FileObject = new File([new Blob(['content'], {type: 'text/plain'})], 'image.png', {type: 'image/png'});
+        // Chromium rejects the read when the backing OS file changed since it was picked.
+        const arrayBufferSpy = jest.fn().mockRejectedValue(new DOMException('The requested file could not be read', 'NotReadableError'));
+        Object.defineProperty(file, 'arrayBuffer', {value: arrayBufferSpy, configurable: true});
+
+        const result = await validateAttachmentFile(file);
+
+        expect(result.isValid).toBe(false);
+        if (result.isValid) {
+            throw new Error('validateAttachmentFile should return an invalid result');
+        }
+        expect(result.error).toBe(CONST.FILE_VALIDATION_ERRORS.FILE_INVALID);
+    });
+});