在网站与 Android 应用间配置凭据共享

一、概览：用关联证明同一服务

如果同一服务同时有网站和Android应用，要求用户分别登录会增加操作负担。Digital Asset Links（DAL）让网站和应用声明关联，使Google Password Manager等支持的密码管理器可以在它们之间使用已保存的密码与passkey；这不是让任意网页脚本读取另一个站点的密码库。

两类凭据所需关系不同：密码需要 delegate_permission/common.get_login_creds；网站与Android应用共享passkey还必须包含 delegate_permission/common.handle_all_urls，用来证明应用与passkey所属域名的关联。该关系也用于Android App Links深链，不能因已经配置密码关系就省略它。

原文引用eBay案例称采用DAL后登录成功率提高10%；这是原案例报告，不是对其他服务的性能保证。完成本教程需要JSON和Android开发基础，并熟悉Credential Manager前置条件。

网站必须能在准确域名的 https://{your-domain}/.well-known/assetlinks.json 托管JSON。Play Console路线需要已在Google Play发布的应用；手动路线需要可以修改和构建的Android工程，而且要让Google Password Manager共享凭据，应用仍必须发布到Google Play，本地未发布应用不满足这一条件。

关联是双向的：Web→App由网站文件声明信任的Android应用；App→Web则需要应用侧声明信任的网站。可用Play Console自动管理应用侧关联，也可手动配置。

二、推荐路线：Google Play Console

此路线由Google Play管理App→Web关系，无需修改应用manifest或重新发布应用版本。你需要访问Deep links页面的Play Console权限，以及发布域名关联文件的权限。

1. 进入Play Console的 Grow → Deep links。
2. 如果域名尚未列出，在App configuration下选择Add domain。
3. 找到该域名的Credential sharing列，点击Turn on；新增域名时确认Enable credential sharing已开启。
4. 复制Play Console生成的JSON片段。
5. 把JSON发布到该域名的 /.well-known/assetlinks.json。已有文件时，在现有JSON数组中追加新声明，保留其他有效关联。
6. 返回Play Console，选择Create website association或Turn on credential sharing，由控制台验证托管内容。

网址必须可通过HTTPS访问，响应类型为 Content-Type: application/json，不能重定向。验证后关联生效，但配置变化传播可能需要1–2周；不要仅凭上传成功就判断所有设备已经更新。

三、手动路线：网站文件与Android资源

无法使用Play Console或需要更多控制时，可以自行建立双向关系。手动方式仍不绕过Google Password Manager对应用已发布到Google Play的要求。

1. 取得应用身份

对每个Android应用，取得build.gradle中声明的application ID及签名证书SHA-256指纹；原文推荐通过Credential Manager API实现登录。应使用实际发布身份，区分Play App Signing、调试、发布及不同flavor；指纹是公开证书摘要，不是私钥。原文允许指纹数组包含多把签名密钥，但生产域名只应关联真实需要且仍受控制的身份。

2. 创建assetlinks.json

下面保留原文结构及公开示例指纹。需要密码和passkey时同时包含两项关系。包名、域名和指纹都必须替换为自己的正确值，不能原样部署。

网站→Android原示例

[{
  "relation": [
    "delegate_permission/common.handle_all_urls",
    "delegate_permission/common.get_login_creds"
    ],
  "target": {
    "namespace": "android_app",
    "package_name": "com.example.app",
    "sha256_cert_fingerprints":
    ["14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5"]
  }
}]

3. 托管关联文件

放到域名根目录下的 .well-known/assetlinks.json，再次检查HTTPS、application/json和无重定向。子域要按实际认证主机分别配置，检查CDN缓存及代理是否改写JSON。

4. 配置Android应用

在res/values/strings.xml加入asset_statements字符串，注意JSON引号要转义。然后在AndroidManifest.xml的application元素中增加meta-data引用该字符串资源。以下两个完整片段来自原文；其余应用设置要与真实工程合并，不能把示例包名或备份设置无条件覆盖到现有项目。

strings.xml原示例

<resources>
    <string name="asset_statements" translatable="false">
      [{
        \"include\": \"https://www.example.com/.well-known/assetlinks.json\"
      }]
    </string>
</resources>

AndroidManifest.xml原示例

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.app">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">

        <meta-data
            android:name="asset_statements"
            android:resource="@string/asset_statements" />

        <activity android:name=".MainActivity">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>
    </manifest>

完成后发布新应用版本，支持DAL的密码管理器才能在www.example.com与com.example.app之间提供凭据建议；传播同样可能需要1–2周。该配置没有实现登录服务器，也不能代替应用鉴权、CSRF、防钓鱼、MFA或账号恢复。

四、验证设置

错误JSON或无法访问的文件可能静默导致关联失败。上线前使用官方Statement Generator and Validator：输入网站域名与应用包名，按界面要求填写签名指纹并选择要检查的关系，点击Test Statement；工具检查文件是否正确托管并包含有效关联。分别验证密码与passkey所需关系，不把一次检查当作完整登录流程测试。

还应在目标密码管理器和测试账号中检查网站/应用互相提示凭据的行为。关联文件不含秘密，但部署权限、域名控制和签名身份属于信任边界；不要加入未知第三方应用或已失去控制的域名。

五、多个网站：密码与passkey分别配置

如果example.com与example.co.uk使用同一个登录系统，可把它们声明为关联网站。密码使用web→web的get_login_creds关系；在example.com的assetlinks.json中加入下列声明，并在example.co.uk发布指向example.com的对等声明。

网站→网站密码关联

[{
  "relation": ["delegate_permission/common.get_login_creds"],
  "target": {
    "namespace": "web",
    "site": "https://example.co.uk"
  }
}]

Chrome会自动在某些same-site网站之间共享已保存凭据，例如www.example.com与m.example.com。但网站与Android应用（含App WebView）的行为不同：必须在实际发生登录的子域的 /.well-known/assetlinks.json 提供有效DAL。

跨网站使用passkey

passkey绑定Relying Party ID（RP ID）域名。多个网站共享同一passkey时需要使用同一RP ID；跨站来源可以通过Related Origin Requests声明允许使用该RP ID的其他origin。这与网站→Android使用DAL中的handle_all_urls不同。

原例选择example.com作为规范RP ID：example.co.uk的WebAuthn API调用必须使用 rpId: 'example.com'；example.com在 https://example.com/.well-known/webauthn 发布以下允许列表。这样example.co.uk可创建和使用关联到example.com的passkey。是否支持仍需按目标浏览器和平台验证，不能任意扩大来源。

RP域名的.webauthn文件

{
  "origins": [
    "https://example.co.uk"
  ]
}

关联具有传递性。原文明确指出，如果实体A与B（网站或应用）都与C关联，密码管理器会把A与B也视为可共享凭据的关联方。因此每新增一个关系都可能扩大共享组，应只纳入同一授权体系并定期检查退役身份。

结语与验证边界

完成且验证上述配置后，用户可在同一服务的网站和Android应用中使用支持的密码或passkey，减少重复登录。可以继续阅读原文链接的Digital Asset Links官方文档、Credential Sharing Fundamentals和eBay案例。这里没有声称已经为任何真实应用部署或验证；所有JSON/XML和WebAuthn参数只经静态审查，没有调用Play Console、修改账户、发布应用或传输凭据。

来源与许可

原页及本文翻译来源：Google Developers Codelabs，Set Up Seamless Credential Sharing Across Websites and Android Apps。除另有说明，页面文档内容为Creative Commons Attribution 4.0，代码样例为Apache License 2.0。本稿进行中文翻译、结构重排和明确标注的安全解释，原五幅图片和五个代码块未改；不表示Google对编辑注释背书。原图中商标权不变；Java是Oracle及/或其关联公司的注册商标。完整代码许可证如下。

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