[keycloak-user] OpenID Connect: Is storing access token in browser sercure?

[Timurhan Sungur]

Thank you for your answer. What is the reason behind keeping it short? In my use case, it is valid for 2 hours and I will store it somewhere during that period. 

Regards,

Timur

Sent from my mobile device.

> Am 22.03.2019 um 08:48 schrieb Sebastien Blanc <sblanc at redhat.com>:
> 
> I'm not sure to understand you usecase and anyway the access token lifespan should always be really short (it's 1 minute by default in Keycloak) so I don't really see the point of storing it in the local storage.  
> 
>> On Thu, Mar 21, 2019 at 8:42 PM Timurhan Sungur <timurhan.s at gmail.com> wrote:
>>  <https://security.stackexchange.com/questions/205837/openid-connect-is-storing-access-token-in-browser-sercure>
>> Hi,
>> 
>> I'm currently in the phase of integrating my web-site to OpenID Connect provided by KeyCloak. The web-site is not a single page application. However, different parts of the application are delivered by different web services.
>> In each site delivered by these different web services, the user can call a standard REST API. This REST API can only be accessed with an access token received from KeyCloak. Thus, the user needs to log-in on the web-site using authorization code flow of OpenId Connect <https://openid.net/specs/openid-connect-core-1_0.html> offered by KeyCloak <https://www.keycloak.org/> and use the access token given by the token endpoint. This request with the access token can be either sent by browser or by one of the back-end services delivering the current web-site. Thus, we can either do a a client-side integration or server-side integration with the REST API.
>> 
>> Unfortunately, the server-side integration is not that feasible due to the complex structure of back-end systems. I cannot even integrate most of web services with KeyCloak. Thus, I could store the access token in the browser in local storage <https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage> and access to the REST API directly from browser. However, I'm still unsure if storing the access token in browser will bring a security vulnerability.
>> 
>> I could not see any official statement regarding this in the standards or in the KeyCloak documentation, so far. I have seen applications both storing it in the back-end and storing in the browser and I still can't tell the exact security benefit of using a session over an access token when we store it in the back-end. I do not intend to save refresh token in the browser and use only authorization code flow with the help of a back-end service.
>> 
>> My questions:
>> 
>> Is it a security vulnerability to store the access token in browser? E.g., in local storage, in a cookie with HttpOnly, or both of them?
>> Is there a way to mitigate the security threat and still store it in browser?
>> Is there a best practice or guideline for storing the access tokens of OpenID Connect that you could refer to?
>> What is the difference from the security perspective between storing the access token and session, if we can use the session to access the API over an intermediary service?
>> Thank you for your assistance in advance!  
>> 
>> 
>> Regards,
>> 
>> Timur
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