Re: Signal to end-user when using webauthn

The concern is not that attackers might collect biometric data from a 
webauthn-capable device, but from non-webauthn-capable (plain vanilla) 
biometric devices.

The vast majority of biometric authenticators today do not use/support 
FIDO/webuthn protocols (yet).  I surmise these devices manage {origin, 
userid, password} tuples much like password-managers, authenticating 
users to a site after authenticating them with a biometric-gesture.  
However, in the absence of a /webauthn-signal//, /these "plain vanilla" 
devices will _appear_ to function like webauthn-capable biometric 
devices from a UX pov,

Such "plain vanilla" devices are unlikely to disappear even if the 
webauthn spec is finalized and platforms support it immediately; RPs are 
unlikely to migrate to webauthn immediately for lots of non-technical 
reasons.  However, by having a /webauthn-signal/ show up before the 
biometric-gesture, end-users can be educated to recognize 
privacy-protecting devices/sites from potentially dubious ones.

In a world where every biometric device and site is webauthn-capable - 
_and_ enabled - this signal would be unnecessary.  But just as the "SSL 
lock" helps differentiate data-protecting sites from unprotected ones, a 
webauthn-signal can help differentiate privacy-protecting sites from 
questionable ones.

Arshad

P.S.  The phishing attacks, if successful, will work only on "plain 
vanilla" devices; but sans a webauthn-signal, the PR fallout will affect 
all devices - whether webauthn-capable or not - and potentially deter 
consumers from using any device.


On 07/05/2016 08:59 PM, Vijay Bharadwaj wrote:
> Arshad,
>
> Would you please elaborate on the phishing concern here? Is it that a website may somehow find a different way to show UI and gather the user's biometrics (and if so, how would it do that)?
>
> Similarly, what's the privacy issue? When would a biometric gesture be prompted by the browser without a WebAuthn call, and what would the website be hoping to gain?
>
> There are of course ways for a website to compromise privacy by overusing WebAuthn - for instance a site may call getAssertion for no good reason, just to check whether a particular user is present (figuring that if they are like most users they will provide a biometric, just to make the prompt go away). But isn't that more about what is in the heart of the caller, and unlikely to be affected by the type of signal you propose?
>
> -----Original Message-----
> From: Arshad Noor [mailto:arshad.noor@strongauth.com]
> Sent: Tuesday, July 05, 2016 5:55 PM
> To:public-webauthn@w3.org
> Subject: Re: Signal to end-user when using webauthn
>
> No, its not.  This is necessary not only for key-registration (where attestation comes into the picture) but for every authentication.
>
> Users are going to be prompted for the biometric gesture each time a biometric Webauthn Authenticator is activated for use: registration, authentication and transaction confirmation.  If they do not see a standard signal when Webauthn is in use, not only do they NOT know if there is a privacy-leak, but they also become vulnerable to phishing attacks (since the platform is not giving off any signals to the contrary).
>
> Arshad Noor
> StrongAuth, Inc.
>
> On 07/05/2016 04:18 PM, Anthony Nadalin wrote:
>> Isn't this already implied by the attestations that may be part of the registration (which is out of scope of the W3C WebAuthn WG).
>>
>> -----Original Message-----
>> From: Arshad Noor [mailto:arshad.noor@strongauth.com]
>> Sent: Sunday, July 3, 2016 6:41 PM
>> To:public-webauthn@w3.org
>> Subject: Signal to end-user when using webauthn
>>
>> I'm not sure if this is part of this WG's purview, but as the WG focuses on standardizing Webauthn, I would like to suggest adding one more element to its scope: a signal to the end-user when the platform is using the Webauthn standard to strongly-authenticate the user.
>>
>> An informal case for this is documented in this brief blog entry:
>> *Not all biometric authentication is equal* -https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2falesa.website&data=01%7c01%7ctonynad%40microsoft.com%7cc713a71937b848c356c608d3a3ac794a%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=7WkozRldsTeHy6HRLVcQ27tpPOI0VryBKbrWtCTuXWM%3d.
>>
>> Thank you.
>>
>> Arshad Noor
>> StrongAuth, Inc.
>>