Can't link Android app with Digital Asset Link since app doesn't have a signature

Question

I'm trying to to setup a Digital asset link from my website to my app, but I can't get it to work. I made sure the intent-filter was present in my manifest and I uploaded a assetlinks.json file using my Play store signing SHA 256 fingerprint, tested it with Google's statement list and it returned successfuly.

While going through verification steps again, I checked my device's app links with adb -d shell pm get-app-links --user current com.example.app and I realized that my app link didn't have a signature. I'm guessing that's its probably the reason the app can't link to my website since it can't compare a signature to the fingerprints given in the assetlinks.json hosted on my site's server.

My app link

com.example.app 01234567-89ab-cdef-0123-456789abcdef:
    User 0:
      Verification link handling allowed: true
      Selection state:
        Enabled:
          com.example.app

Compared to another

com.google.android.youtube:
    ID: 01234567-89ab-cdef-0123-456789abcdef
    Signatures: [<has-some-SHA256-certificate-fingerprints-here>]
    Domain verification state:
      youtu.be: system_configured
      m.youtube.com: system_configured
      youtube.com: system_configured
      www.youtube.com: system_configured
    User 0:
      Verification link handling allowed: true
      Selection state:
        Disabled:
          youtu.be
          m.youtube.com
          youtube.com
          www.youtube.com

For some reason, my app link doesn't have the same format as most of the other links, more importantly doesn't have a signature, and I can't figure out why. However I tried installing it, it always gave the same results. I tried installing it:

From the Play store's internal testing
From a signed apk downloaded from the App bundle explorer
From the signed apk we normally upload to the Play store
From a manually signed apk built on my local machine

Has anyone any idea what I'm missing?

score 2 · Accepted Answer · answered Nov 29 '21 at 13:19

I managed to find the solution to my problem. Turns out my intent-filter had multiple empty data tags which seemed to prevent my app to detect the website.

I forgot to specify that I'm my app's AndroidManifest is built by Cordova since I'm using Ionic. So I cannot edit my AndroidManifest directly. I have to use the ionic-plugin-deeplinks plugin.

The problem is, the ionic plugin generates an intent-filter with the data given in the package.json with the following format.

"cordova": {
  "plugins": {
    "ionic-plugin-deeplinks": {
      "URL_SCHEME": "my-url-scheme",
      "DEEPLINK_SCHEME": "https",
      "DEEPLINK_HOST": "com.example.app",
      "ANDROID_PATH_PREFIX": "/",
      "ANDROID_2_PATH_PREFIX": "/",
      "ANDROID_3_PATH_PREFIX": "/",
      "ANDROID_4_PATH_PREFIX": "/",
      "ANDROID_5_PATH_PREFIX": "/",
      "DEEPLINK_2_SCHEME": " ",
      "DEEPLINK_2_HOST": " ",
      "DEEPLINK_3_SCHEME": " ",
      "DEEPLINK_3_HOST": " ",
      "DEEPLINK_4_SCHEME": " ",
      "DEEPLINK_4_HOST": " ",
      "DEEPLINK_5_SCHEME": " ",
      "DEEPLINK_5_HOST": " "
    }
  }
}

This format is automatically generated by the plugin and adds multiple host/scheme/prefix to allow support of multiple addresses. However I'm using only one address, so when I'm generating the AndroidManifest with the plugin, it generates an intent-filter with many empty data tags in it.

<intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <data android:host="com.example.app" android:pathPrefix="/" android:scheme="https" />
    <data android:host=" " android:pathPrefix="/" android:scheme=" " />
    <data android:host=" " android:pathPrefix="/" android:scheme=" " />
    <data android:host=" " android:pathPrefix="/" android:scheme=" " />
    <data android:host=" " android:pathPrefix="/" android:scheme=" " />
</intent-filter>

As of now the only way I managed to remove the extra data tags was to fork the plugin's repository and remove the package.json extra properties from the plugin. It looks like this:

"cordova": {
  "plugins": {
    "ionic-plugin-deeplinks": {
      "URL_SCHEME": "my-url-scheme",
      "DEEPLINK_SCHEME": "https",
      "DEEPLINK_HOST": "com.example.app",
      "ANDROID_PATH_PREFIX": "/"
    }
  }
}

Which generates this intent-filter that is working has intented:

<intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <data android:host="com.example.app" android:pathPrefix="/" android:scheme="https" />
</intent-filter>

Thanks for this, put me on to the right track to solve an issue where supported web addresses in our cordova app were disabled by default. For anyone wondering where specifically these changes need to happen; when forking the ionic-plugin-deeplinks repo remove the `` attributes from `plugin.xml` starting from `$DEEPLINK_2_SCHEME` downwards. Leave the first `DEEPLINK_SCHEME` attribute in tact. — Loz, May 16 '23 at 09:51

score 1 · Answer 2 · edited Nov 30 '21 at 14:29

1

This might help other people, but I made 2 intent filters:

One with http/s only data tags and
The other with my app's name as the scheme.

It didn't seem to work when the custom theme was bundled under one intent filter.

edited Nov 30 '21 at 14:29

ouflak

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answered Nov 30 '21 at 14:04

while-loop

11
1

score 0 · Answer 3 · answered Nov 25 '21 at 14:35

I might just have solved something like this. Things to check:

Please note, i'm only using imgur.com as an example, I'm not affiliated/working for them in any way.

Check your assetlinks.json, and compare it to a working one (e.g. https://imgur.com/.well-known/assetlinks.json). You could also test your file like so: https://digitalassetlinks.googleapis.com/v1/statements:list?source.web.site=https://imgur.com&relation=delegate_permission/common.handle_all_urls
Next, check your AndroidManifest.xml, and ensure that the attribute android:autoVerify="true" is set on the intent-element (By mistake, I've declared mine on the activity-element) which caused same problem as above):

    <activity android:name=".MainActivity">
            <intent-filter android:autoVerify="true">
                <action android:name="android.intent.action.VIEW" />

                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.BROWSABLE" />

                <data
                    android:scheme="https"
                    android:host="imgur.com" />
            </intent-filter>
    </activity>

Next, build a signed .apk (use the same keystore to sign your .apk with, as you've used to set the footprint in the assetlinks.json file - i.e. $ keytool -list -v -keystore myapp.keystore), and install that into the emulator. Something like this (uninstall app from emulator first):

    $ adb install /myapp/app-release.apk
    $ adb shell
    : pm get-app-links com.myapp.app

Also, this reference page is handy while working with this: https://developer.android.com/training/app-links/verify-site-associations#manual-verification -- hope this helps!

Can't link Android app with Digital Asset Link since app doesn't have a signature

3 Answers3