Re: [OAUTH-WG] Cookies & headers in OAuth 2.0 Security Best Current Practice?

[Dick Hardt <[e-mail]>]

Would you not agree that a "good" CSP config is a good line of defense
against XSS attacks?

I agree that the OAuth BCP should not provide details on CSP config. I do
think we should call out having a considered CSP config is a best practice.

I differentiate between headers and cookies and SQL injection etc. in that
the headers and cookies are part of the HTTP requests, which is the
protocol OAuth is built on, so weaknesses there weaken the protocol.

On Mon, Nov 6, 2023 at 11:25 AM Philippe De Ryck <
[e-mail]> wrote:

> I went back to the Security BCP and combed through the fine details, and
> there is indeed some guidance on CSP. But your initial remark that this is
> "vague" is definitely true, and this section is actually a good
> illustration of what I was trying to say. Let me unpack the details a bit …
>
> In section 4.16, the security BCP talks about how to restrict framing to
> avoid clickjacking/UI redressing attacks. Defending against such attacks
> cannot be done with secure coding, but must be done with specific framing
> restrictions. The best mechanism to achieve this is by setting security
> headers: the legacy X-Frame-Options header or the more modern CSP
> frame-ancestors directive. Given that this security requirement is closely
> linked to OAuth and is not something that “happens naturally”, but must be
> explicitly added, I totally agree that this should be part of the security
> BCP.
>
> Now, in paragraph 5 of the section, things get somewhat confusing
> (included below for reference). So far, every mention of "CSP" was used as
> a synonym for the "frame-ancestors" directive to restrict framing. However,
> all the way at the end of that paragraph, the text suddenly recommends
> using the "script-src" directive to restrict sources of JS that can execute
> on the page. The paragraph then points to a sample header, with the
> configuration of "script-src 'self'".
>
> *Using CSP allows authorization servers to specify multiple origins in a
> single response header field and to constrain these using flexible patterns
> (see [W3C.CSP-2 <https://www.w3.org/TR/CSP2>] for details). Level 2 of this
> standard provides a robust mechanism for protecting against clickjacking by
> using policies that restrict the origin of frames (using frame-ancestors)
> together with those that restrict the sources of scripts allowed to execute
> on an HTML page (by using script-src).*
>
> Unfortunately, this advice is too simplistic to be useful, as it prevents
> the loading of JS from any other origin, including CDNs, or third-party
> services. Additionally, it violates modern best practices for CSP, which
> recommend the use of hashes, nonces, and trust propagation (with nonce
> propagation or 'strict-dynamic'). If you’re interested in the details, I’ve
> done a few guest blog posts about CSP for Auth0 that cover this:
> https://auth0.com/blog/authors/philippe-de-rick/
>
>
> What I'm trying to say here is that a detailed CSP config (apart from the
> "frame-ancestors" directive) is not essential for a secure OAuth
> implementation or deployment. It can and should act as a second line of
> defense against content injection attacks, but not having such a CSP config
> does not automatically create a vulnerability. Therefore, my recommendation
> is to focus on the details directly relevant to OAuth security.
>
> For security guidelines for configuring cookies, I believe this would be
> more directly related and more useful, as I mentioned before.
>
> Finally, I can totally see that the community could benefit from more
> in-depth security best practices that go beyond OAuth-specific risks. Apart
> from CSP, there's a whole bunch more response headers that can be
> configured (as you and others have mentioned). On top of that, modern
> browsers send a lot of metadata in a request (e.g., the Sec-Fetch Metadata
> headers) that could be used by the AS to reject illegitimate requests.
> However, given the rapid development of these features and lack of
> widespread support, I would envision such recommendations to live in a more
> "dynamic" document than an RFC.
>
> Philippe
>
> —
> *Pragmatic Web Security*
> *Security for developers*
> https://pragmaticwebsecurity.com
>
> On 6 Nov 2023, at 18:07, Dick Hardt <[e-mail]> wrote:
>
> That's a surprising response Philippe. The BCP already has
> Content-Security-Policy and Referrer-Policy headers recommendations. The
> core of my feedback is to add Cookie and Header best practices to Section
> 2, and point to one or more living documents.
>
> On Mon, Nov 6, 2023 at 8:45 AM Philippe De Ryck <
> [e-mail]> wrote:
>
>> While I understand the idea of pointing to additional security resources,
>> I’m not sure if it is the role of the security BCP (or other specs) to take
>> on the responsibility to address these issues. In my point of view, the
>> security BCP should focus on OAuth aspects, and discuss security topics
>> that are directly relevant to that purpose.
>>
>> Concretely for the security mechanisms discussed here, I can see how
>> cookie configurations could be relevant (the session with the AS is
>> inherent to OAuth), but I don’t see defenses such as CSP as relevant in
>> that scope. If these are in scope, should we then also provide advice or
>> pointers on avoiding server-side implementation vulnerabilities, such as
>> SQL injection or SSRF?
>>
>> Additionally, many of these security mechanisms are quite complex and
>> non-trivial to deploy. For example, adding a generic pointer stating “you
>> should add CSP” does not say much, as CSP can control more than a dozen
>> features.
>>
>> To summarize, I would keep the scope of these specs as narrow as possible
>> and avoid aiming to address security concerns that are beyond the realm of
>> OAuth.
>>
>> Philippe
>>
>> —
>> *Pragmatic Web Security*
>> *Security for developers*
>> https://pragmaticwebsecurity.com
>>
>> On 6 Nov 2023, at 15:39, Dick Hardt <[e-mail]> wrote:
>>
>> +1 to referring to calling out that cookies / headers should follow best
>> security practice, and pointing to living documents
>>
>> On Mon, Nov 6, 2023 at 6:21 AM Giuseppe De Marco <[e-mail]>
>> wrote:
>>
>>> Hi,
>>>
>>> everytime I have implemented SAML2, OAuth 2.0, OpenID Connect, for
>>> different projects and orgs, I have included secured web cookie in
>>> the recipe.
>>> For the implementation profile of OpenID4VP I did the same, where the
>>> secured and httponly cookie is used an in particular as a basic security
>>> requirement for the cross device flow [1].
>>>
>>> Even if I got perfectly Daniel's and Aaron's editorial strategy and I
>>> agree, I think that Dick's proposal and your confirmation on that, Neil, is
>>> something to take into account to bring developers awareness during the
>>> implementation phases.
>>> A ref to living OWASP specs surrounded by a generic refs to the user
>>> agent security, even if out of scope, I think that should be in the specs.
>>>
>>> [1]
>>> https://italia.github.io/eudi-wallet-it-docs/versione-corrente/en/relying-party-solution.html#remote-protocol-flow
>>>
>>> Il giorno lun 6 nov 2023 alle ore 15:11 Neil Madden <
>>> [e-mail]> ha scritto:
>>>
>>>> Although I think we could add some basic advice, the list of security
>>>> headers to use is still evolving. For example, there were several headers
>>>> added after Spectre to limit cross-site interactions. And then there’s
>>>> things like the “X-XSS-Protection” header, which was best practice to add
>>>> to responses not too long ago but has now been universally removed from
>>>> browsers as it enabled certain content disclosure attacks.
>>>>
>>>> Cookie security attributes are perhaps a bit more stable, but in
>>>> general we probably just want to point people at “living” guidance like
>>>> OWASP.
>>>>
>>>> — Neil
>>>>
>>>> On 5 Nov 2023, at 19:28, Dick Hardt <[e-mail]> wrote:
>>>>
>>>> The cookie and header recommendations I am thinking of would be for the
>>>> AS as well as the client.
>>>>
>>>> A number of XSS attacks can be thwarted by a modern browser and the
>>>> right HTTP headers.
>>>>
>>>> My question is: Did the authors consider adding cookie and header
>>>> recommendations, and decided it was too general?
>>>>
>>>> Cookie and header best security practices have been around for years --
>>>> I'm not suggesting we make anything up -- I'm suggesting we raise
>>>> awareness.
>>>>
>>>> I consider myself to be fairly security aware, and I was not aware of
>>>> some of the HTTP headers that are best security practice.
>>>>
>>>> /Dick
>>>>
>>>>
>>>> On Sun, Nov 5, 2023 at 11:19 AM Aaron Parecki <aaron=
>>>> [e-mail]> wrote:
>>>>
>>>>> I don't think it's necessary to say "do the right things with cookies"
>>>>> in the Security BCP. The Browser Apps BCP has a much deeper discussion of
>>>>> how different browser-based architectures work with cookies so that seems
>>>>> like a better place to actually have a real discussion about it.
>>>>>
>>>>> Also +1 to what Daniel said about not continuing to add little things.
>>>>> Plus I think it's too late anyway, publication has already been requested
>>>>> for the Security BCP.
>>>>>
>>>>> Aaron
>>>>>
>>>>> On Sun, Nov 5, 2023 at 11:14 AM Daniel Fett <fett=
>>>>> [e-mail]> wrote:
>>>>>
>>>>>> I agree with Aaron!
>>>>>>
>>>>>> Also we should be very careful about any additions to the Security
>>>>>> BCP at this point. It is very easy to re-start the "one more thing" loop
>>>>>> we've been stuck in for the last years. There may be more useful things to
>>>>>> say, but we should put them on the list for a future second version of the
>>>>>> BCP.
>>>>>>
>>>>>> -Daniel
>>>>>> Am 05.11.23 um 20:03 schrieb Aaron Parecki:
>>>>>>
>>>>>> I don't think the Security BCP should incorporate cookie best
>>>>>> practices directly in the document. If anything, it sounds like possibly a
>>>>>> candidate for inclusion in the Browser Apps BCP.
>>>>>>
>>>>>> There are already some mentions of these cookie properties mentioned
>>>>>> in the Browser Apps BCP, though only in reference to specific
>>>>>> architectures, not as a general best practice. For example:
>>>>>>
>>>>>>
>>>>>> https://www.ietf.org/archive/id/draft-ietf-oauth-browser-based-apps-15.html#pattern-bff-cookie-security
>>>>>>
>>>>>> Aaron
>>>>>>
>>>>>> On Sun, Nov 5, 2023 at 10:48 AM Dick Hardt <[e-mail]>
>>>>>> wrote:
>>>>>>
>>>>>>> Hey
>>>>>>>
>>>>>>> I was reviewing security on some sites I managed and checked to see
>>>>>>> if the recommendations were in the BCP.
>>>>>>>
>>>>>>> I don't see anything around cookies such as httpOnly, sameSite,
>>>>>>> secure.
>>>>>>>
>>>>>>> I saw some HTTP security header suggestions buried in 4.16
>>>>>>> (X-Frame-Options, CSP), but not for Strict-Transport-Security,
>>>>>>> Permissions-Policy, or X-Content-Type-Options, and the CSP guidance is
>>>>>>> rather vague.
>>>>>>>
>>>>>>> I understand these are general web security best practices, and
>>>>>>> perhaps I missed it, but I think it would be useful to call out that best
>>>>>>> security practices around cookies and headers should also be followed in
>>>>>>> Section 2, and either have the best practices included, or direct the
>>>>>>> reader where to find them.
>>>>>>>
>>>>>>> /Dick
>>>>>>>
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