一个奇怪的权限问题

Google搜索该bug，几乎找不到解决该问题的答案(也有可能是我没找到)，特此记录一下

Caused by: java.lang.SecurityException: UID 10799 does not have permission to content://com.miui.gallery.open/raw/%2Fstorage%2Femulated%2F0%2FDCIM%2FCamera%2FIMG_20210210_103348.jpg [user 0]

前段时间，项目组的一个小伙伴向我寻求了帮助。他负责的头像上传功能，在小米手机上突然无法走通，在某个阶段，系统打印出了以上错误日志。粗粗一看权限问题。根据线下实测，刚好在小米10上能复现问题，在小米11、华为手机上都没问题。第一反应感觉有点不可思议，按常理，一段代码如果不是系统版本问题，应该是全都有问题才对呀。如果是系统问题，那可就有点棘手了。

在解决问题前，首先介绍下业务场景。点击头像控件，跳转到系统相册选择图片，选择完毕跳转到系统裁剪程序裁剪图片。

跳转裁剪程序代码如下

fun gotoSystemCrop(uri: Uri) {
    val intent = Intent("com.android.camera.action.CROP")
    intent.setDataAndType(uri, "image/*")

    grantPermission(intent, uri)
    intent.putExtra("crop", "true");// 进行修剪
    intent.putExtra("aspectX", 1)
    intent.putExtra("aspectY", 1)
    intent.putExtra("outputX", 360)
    intent.putExtra("outputY", 360)
    val tmpFile =
        File(externalCacheDir.toString() + File.separator + "photo" + "_" + System.currentTimeMillis() + ".png")
    var cropUri = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        FileProvider.getUriForFile(
            this,
            "com.peter.viewgrouptutorial1",
            tmpFile
        )
    } else {
        Uri.fromFile(tmpFile)
    }
    intent.putExtra(MediaStore.EXTRA_OUTPUT, cropUri);

    grantPermission(intent, cropUri)
    startActivityForResult(intent, REQUEST_SYSTEM_CROP);
}

请求授权代码如下

private fun grantPermission(intent: Intent, uri: Uri?) {
    var flag = Intent.FLAG_GRANT_READ_URI_PERMISSION
    flag = flag or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
    intent.addFlags(flag)
    val resInfoList = packageManager
        .queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY)
    for (resolveInfo in resInfoList) {
        val packageName = resolveInfo.activityInfo.packageName
        println("xiaozhan $packageName")
        grantUriPermission(packageName, uri, flag)
    }
}

首先 分析下gotoSystemCrop方法中的代码，调用了两次grantPermission方法，grantPermission(intent, uri)和grantPermission(intent, cropUri)。我们都知道Intent有显式调用和隐式调用两种，在此用的是隐式调用。后者可能会匹配到多个符合条件的Activity。uri表示图片选择程序返回给业务应用的图片路径，cropUri表示将裁剪后的图片保存到业务应用的存储路径。

其次 假设intent匹配到的程序包名叫com.miui.gallery，我的业务app包名叫com.peter.viewgrouptutorial。那么grantPermission(intent, uri)表示给com.miui.gallery赋予读写uri的权限，而uri的主人正是com.miui.gallery，而在Android中，App对自己暴露出去的Uri的读写权限是与生俱来的。所以第一个授权是不需要的。

再次 grantPermission(intent, cropUri) 表示在com.peter.viewgrouptutorial程序中给com.miui.gallery授予访问com.peter.viewgrouptutorial暴露出来的Uri的权限。换句话说，就是让裁剪程序裁剪完成后，把图像保存到业务App中的存储路径中去。而跨App读写文件，是需要请求权限的。

上图我们需要明白一个道理 A应用能把UriA的读写权限赋予给B、C。而不能把UriB的权限赋予给C。

最后 说明下问题产生的原因。根据隐式Intent，系统匹配到了两个程序可以处理图片裁剪com.miui.gallery和com.miui.mediaeditor。

1. 运行代码，在第一个grant处，业务应用把com.miui.gallery的uri读写权限授权给com.miui.mediaeditor，报错如下

 java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://com.miui.gallery.open/raw//storage/emulated/0/DCIM/Camera/IMG_20210210_103348.jpg typ=image/jpeg flg=0x1 }} to activity {com.peter.viewgrouptutorial/com.peter.viewgrouptutorial.PhotoActivity}: java.lang.SecurityException: UID 10799 does not have permission to content://com.miui.gallery.open/raw/%2Fstorage%2Femulated%2F0%2FDCIM%2FCamera%2FIMG_20210210_103348.jpg [user 0]
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4940)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:4981)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2046)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:225)
        at android.app.ActivityThread.main(ActivityThread.java:7564)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

2. 注释掉1处的授权代码，运行报错如下，报错差不多。但是此时是ResolverActivity没有访问图片Uri的权限。

    Process: com.peter.viewgrouptutorial, PID: 3894
    java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://com.miui.gallery.open/raw//storage/emulated/0/DCIM/Camera/IMG_20210210_103348.jpg typ=image/jpeg flg=0x1 }} to activity {com.peter.viewgrouptutorial/com.peter.viewgrouptutorial.PhotoActivity}: java.lang.SecurityException: UID 10799 does not have permission to content://com.miui.gallery.open/raw/%2Fstorage%2Femulated%2F0%2FDCIM%2FCamera%2FIMG_20210210_103348.jpg [user 0]
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4940)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:4981)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2046)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:225)
        at android.app.ActivityThread.main(ActivityThread.java:7564)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
     Caused

3. 最后总结是，由于隐式启动裁剪程序，会调起应用选择界面ResolveActivity，而它没有访问Media程序图片Uri的权限。那么我们就要想办法把隐式调用转成显式调用。解决方案如下

fun gotoSystemCrop(uri: Uri) {
    val intent = Intent("com.android.camera.action.CROP")
    intent.setDataAndType(uri, "image/*")

    intent.putExtra("crop", "true");// 进行修剪
    intent.putExtra("aspectX", 1)
    intent.putExtra("aspectY", 1)
    intent.putExtra("outputX", 360)
    intent.putExtra("outputY", 360)
    val tmpFile =
        File(externalCacheDir.toString() + File.separator + "photo" + "_" + System.currentTimeMillis() + ".png")
    var cropUri = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        FileProvider.getUriForFile(
            this,
            "com.peter.viewgrouptutorial1",
            tmpFile
        )
    } else {
        Uri.fromFile(tmpFile)
    }
    intent.putExtra(MediaStore.EXTRA_OUTPUT, cropUri);

    grantPermissionFix(intent, cropUri)
    startActivityForResult(intent, REQUEST_SYSTEM_CROP);
}

 private fun grantPermissionFix(intent: Intent, uri: Uri?) {
      var flag = Intent.FLAG_GRANT_READ_URI_PERMISSION
      flag = flag or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
      intent.addFlags(flag)
      val resInfoList = packageManager
          .queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY)
      for (resolveInfo in resInfoList) {
          val packageName = resolveInfo.activityInfo.packageName
          try {
              grantUriPermission(packageName, uri, flag)
          } catch (e: Exception) {
              continue
          }
          intent.action = null
          intent.component =
              ComponentName(resolveInfo.activityInfo.packageName, resolveInfo.activityInfo.name)
          break
      }
  }