收紧媒体导出载荷边界

将图片和音频导出载荷预校验提升到共享 HostBridge 契约
让 H5 facade 按共享媒体导出边界归一化文件名、MIME 和 base64 载荷
保留 Expo 与 Tauri 壳对真实字节和 MIME 的二次校验
增加媒体导出载荷测试和三端壳总门禁反查
同步宿主壳协议文档和共享决策记录

packages/shared/src/contracts/hostBridge.test.ts

@@ -37,7 +37,9 @@ import {
   normalizeHostBridgeClipboardText,
   normalizeHostBridgeColorScheme,
   normalizeHostBridgeConnectionType,
+  normalizeHostBridgeExportAudioPayload,
   normalizeHostBridgeExportFileName,
+  normalizeHostBridgeExportImagePayload,
   normalizeHostBridgeExternalUrl,
   normalizeHostBridgeExternalUrlPayload,
   normalizeHostBridgeHapticsImpactStyle,
@@ -349,6 +351,45 @@ describe('HostBridge shared contract helpers', () => {
     expect(HOST_BRIDGE_IMPORT_DOCUMENT_MAX_BYTES).toBe(5 * 1024 * 1024);
   });
 
+  test('归一化宿主图片和音频导出载荷', () => {
+    expect(
+      normalizeHostBridgeExportImagePayload({
+        fileName: ' ../分享:卡?.png ',
+        base64Data: ' c2hhcmU= ',
+        mimeType: 'image/png',
+      }),
+    ).toEqual({
+      fileName: '分享-卡-.png',
+      base64Data: 'c2hhcmU=',
+      mimeType: 'image/png',
+    });
+    expect(
+      normalizeHostBridgeExportAudioPayload({
+        fileName: '敲击音效.wav',
+        base64Data: ' YXVkaW8= ',
+        mimeType: 'audio/wav',
+      }),
+    ).toEqual({
+      fileName: '敲击音效.wav',
+      base64Data: 'YXVkaW8=',
+      mimeType: 'audio/wav',
+    });
+    expect(
+      normalizeHostBridgeExportImagePayload({
+        fileName: 'bad.gif',
+        base64Data: 'c2hhcmU=',
+        mimeType: 'image/gif',
+      }),
+    ).toBeNull();
+    expect(
+      normalizeHostBridgeExportAudioPayload({
+        fileName: 'empty.wav',
+        base64Data: '   ',
+        mimeType: 'audio/wav',
+      }),
+    ).toBeNull();
+  });
+
   test('归一化宿主本地通知内容', () => {
     expect(
       normalizeHostBridgeLocalNotification({

packages/shared/src/contracts/hostBridge.ts

@@ -573,6 +573,10 @@ export const HOST_BRIDGE_IMAGE_MIME_TYPES = [
   'image/webp',
 ] as const satisfies readonly HostBridgeImageMimeType[];
 
+const HOST_BRIDGE_IMAGE_MIME_TYPE_SET = new Set<HostBridgeImageMimeType>(
+  HOST_BRIDGE_IMAGE_MIME_TYPES,
+);
+
 export type FileImportImageResult = {
   action: 'selected' | 'dropped' | 'captured';
   fileName: string;
@@ -625,6 +629,10 @@ export const HOST_BRIDGE_AUDIO_MIME_TYPES = [
   'audio/webm',
 ] as const satisfies readonly HostBridgeAudioMimeType[];
 
+const HOST_BRIDGE_AUDIO_MIME_TYPE_SET = new Set<HostBridgeAudioMimeType>(
+  HOST_BRIDGE_AUDIO_MIME_TYPES,
+);
+
 export type FileImportAudioResult = {
   action: 'selected';
   fileName: string;
@@ -653,6 +661,80 @@ export const HOST_BRIDGE_IMPORT_IMAGE_MAX_BYTES = 10 * 1024 * 1024;
 export const HOST_BRIDGE_EXPORT_AUDIO_MAX_BYTES = 20 * 1024 * 1024;
 export const HOST_BRIDGE_IMPORT_AUDIO_MAX_BYTES = 20 * 1024 * 1024;
 
+function normalizeHostBridgeBase64Data(rawData: unknown) {
+  if (typeof rawData !== 'string') {
+    return null;
+  }
+
+  const base64Data = rawData.trim();
+  if (!base64Data || hasHostBridgeControlCharacter(base64Data)) {
+    return null;
+  }
+
+  return base64Data;
+}
+
+function estimateHostBridgeBase64Bytes(base64Data: string) {
+  const normalizedLength = base64Data.replace(/\s+/g, '').length;
+  return Math.ceil((normalizedLength * 3) / 4);
+}
+
+export function normalizeHostBridgeExportImagePayload(
+  payload: unknown,
+): FileExportImagePayload | null {
+  if (!payload || typeof payload !== 'object') {
+    return null;
+  }
+
+  const candidate = payload as Partial<FileExportImagePayload>;
+  const mimeType = candidate.mimeType as HostBridgeImageMimeType;
+  if (!HOST_BRIDGE_IMAGE_MIME_TYPE_SET.has(mimeType)) {
+    return null;
+  }
+
+  const base64Data = normalizeHostBridgeBase64Data(candidate.base64Data);
+  if (
+    !base64Data ||
+    estimateHostBridgeBase64Bytes(base64Data) > HOST_BRIDGE_EXPORT_IMAGE_MAX_BYTES
+  ) {
+    return null;
+  }
+
+  return {
+    fileName: normalizeHostBridgeExportFileName(candidate.fileName),
+    base64Data,
+    mimeType,
+  };
+}
+
+export function normalizeHostBridgeExportAudioPayload(
+  payload: unknown,
+): FileExportAudioPayload | null {
+  if (!payload || typeof payload !== 'object') {
+    return null;
+  }
+
+  const candidate = payload as Partial<FileExportAudioPayload>;
+  const mimeType = candidate.mimeType as HostBridgeAudioMimeType;
+  if (!HOST_BRIDGE_AUDIO_MIME_TYPE_SET.has(mimeType)) {
+    return null;
+  }
+
+  const base64Data = normalizeHostBridgeBase64Data(candidate.base64Data);
+  if (
+    !base64Data ||
+    estimateHostBridgeBase64Bytes(base64Data) > HOST_BRIDGE_EXPORT_AUDIO_MAX_BYTES
+  ) {
+    return null;
+  }
+
+  return {
+    fileName: normalizeHostBridgeExportFileName(candidate.fileName),
+    base64Data,
+    mimeType,
+  };
+}
+
 export const HOST_BRIDGE_HAPTICS_IMPACT_STYLES = [
   'light',
   'medium',