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Re: [OAUTH-WG] Android App Links (AKA Universal Links)

Dick Hardt <dick.hardt@gmail.com> Tue, 03 November 2020 19:14 UTC

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From: Dick Hardt <dick.hardt@gmail.com>
Date: Tue, 03 Nov 2020 11:13:26 -0800
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To: Joseph Heenan <joseph@authlete.com>, George Fletcher <gffletch@aol.com>
Cc: oauth <oauth@ietf.org>
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Subject: Re: [OAUTH-WG] Android App Links (AKA Universal Links)
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Thanks Joseph.

George Fletcher ran a great session on the topic at the last IIW as well.

George: do you have a link?

ᐧ

On Tue, Nov 3, 2020 at 11:09 AM Joseph Heenan <joseph@authlete.com> wrote:

> Hi Dick
>
> I didn’t attend the call so don’t know the background of this and the
> exact situation, but the general problem is mostly where the Authorization
> Server’s app is *not* installed. In that case Android falls back to much
> weaker mechanisms that allow other apps to get a look in. App links also
> aren’t consistently supported across all commonly used android browsers
> which causes further problems.
>
> In general to do app2app oauth redirections securely on Android it’s
> necessary for both apps to fetch the /.well-known/assetlinks.json for the
> url they want to redirect to, and verify that the intent the app intends to
> launch to handle the url is signed using the expected certificate. Web2app
> flows are trickier, on both iOS and on Android. There were lengthy
> discussions on at least the Android case at OAuth Security Workshop this
> year (recordings available).
>
> Joseph
>
>
> On 20 Oct 2020, at 00:09, Dick Hardt <dick.hardt@gmail.com> wrote:
>
> Hey Vittorio
>
> (cc'ing OAuth list as this was brought up in the office hours today)
>
> https://developer.android.com/training/app-links
>
> An app is the default handler and the developer has verified ownership of
> the HTTPS URL. While a user can override the app being the default handler
> in the system settings -- I don't see how a malicious app can be the
> default setting.
>
> What am I missing?
>
> /Dick
> ᐧ
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