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Date: Wed, 8 May 2019 19:04:25 +0900
From: Seong-Joong Kim <sungjungk@...il.com>
To: Noel Kuntze <noel.kuntze+oss-security@...rmi.consulting>
Cc: oss-security@...ts.openwall.com, Roman Drahtmueller <draht@...altsekun.de>
Subject: Re: Re: fprintd: found storing user fingerprints
 without encryption

In Microsoft's Windows Hello, fingerprint data is kept locally on user's PC
in an encrypted way while Linux does not, even though they are based on
same fingerprint reader hardware.
Windows Hello may use Next Generation Cryptography (called CNG) to protect
and store user private data and encryption keys.
(see
https://support.microsoft.com/en-au/help/4468253/windows-hello-and-privacy-microsoft-privacy
)

Lenovo's Fingerprint Manager Pro also stores user's fingerprints encrypted
in its local environment.
In this regard, a flaw was discovered in Lenovo Fingerprint Manager Pro
(see CVE-2017-3762).
(see
https://thenextweb.com/security/2018/01/26/lenovo-fingerprint-manager-flaw-windows/
)

Moreover, FireEye researchers Tao Wei and Yulong Zhang outlined new ways to
attack Android devices to extract user fingerprints at Black Hat USA 2015
(see Fingerprints On Mobile Devices: Abusing and Leaking?).
(see
https://www.zdnet.com/article/hackers-can-remotely-steal-fingerprints-from-android-phones/
)


This vulnerability could allow a process to access the stored fingerprint
and then it can be reverted to natural-looking original fingerprint image.
It allows the attacker to impersonate a legitimate
authentication/identification by using stolen fingerprints.

Once fingerprint has been leaked, victims are leaked for the rest of life
since it lasts for a life.
Moreover, fingerprints are usually associated with every citizen’s identity
and immigration record.
It would be a hazard if the attacker can remotely harvest fingerprints in a
large scale.

What do you think of it?


2019년 5월 8일 (수) 오후 6:29, Noel Kuntze
<noel.kuntze+oss-security@...rmi.consulting>님이 작성:

> Hello List,
>
> Am 08.05.19 um 11:19 schrieb Roman Drahtmueller:
> >>> Dear all,
> >>>
> >>> I would like to report a vulnerability of 'fprintd'.
> >>>
> >>> 'fprintd' does not encrypt sensitive information before storage.
> >>> *CWE-311: Missing Encryption of Sensitive Data*
> >
> > [...]
> >
> > This misses the point.
> >
> > * Encryption shifts the problem to protecting the symmetric key, which
> >   is the very same problem. => Encryption solves other problems, but not
> >   this one.
> > * If you have sufficient privileges to access the fingerprint data,
> >   then you no longer need the data.
> > * You can't "safeguard" the fingerprint data by applying additional O/S
> >   controls such as SELinux, AppArmor, etc, you can only add more useful
> >   privilege transitions and protect against attacks that exploit
> >   implementation errors. Google "store fingerprint data ios android",
> >   there are suitable solutions.
> >
> > Mostly: Your fingerprint is not a secret like a password, it is a
> username.
> >
> > Since you can't change the fingerprint (biometrics problem), it is not
> very useful as a single authentication factor. Either you live with this,
> or you combine the fingerprint with a different authentication factor type.
> >
> > Roman.
>
> Another argument: You leave your fingerprint on everything you touch. The
> glass you drank from at the bar on Saturday evening? That has your
> fingerprints. Your front door? It has those, too.
> Fingerprints aren't sensitive information. The only entities attributing
> any sensitivity to them are the following: Court systems where fingerprints
> are allowed as evidence (although it's stupid because you can easily
> duplicate fingerprints) and companies/persons using fingerprints for
> authentication (which for the same reason as previously mentioned is not a
> good idea).
> And as Roman mentioned already, you can't change your fingerprints easily
> (Sand paper and acids are your friends, but that's not comfortable at all
> and compromises your ability to hold things in your hands. So don't to
> that.).
>
> If, for some reason, you still want to "securely" (at least with a higher
> level of security than plain text) store your fingerprint, you need to use
> a hardware backed kernel keyring that stores the encryption keys or use a
> hardware based security solution for storing the fingerprints in the first
> case. You likely won't find any such solution though that isn't broken
> already in some regard.
>
> Kind regards
>
> Noel
>
> --
> Noel Kuntze
> IT security consultant
>
> GPG Key ID: 0x0739AD6C
> Fingerprint: 3524 93BE B5F7 8E63 1372 AF2D F54E E40B 0739 AD6C
>
>
>

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