Forum Discussion
Can the F5 APM API Protection profile use for a DNS resolver a local F5 DNS/GTM listener VS?
- Nov 08, 2022
I finally got to this (I upgraded to 16.1.3.2 from 16.1.3 so this could also be important) and I also tested with the pet store that was given as an example in https://support.f5.com/csp/article/K12744365?utm_source=f5support&utm_medium=RSS . With external DNS resolver (in my case google 8.8.8.8) it works like a charm and it seems to me that when referensing external or internal DNS resolvable API then the server mode is best used and when referensing a local pool of API servers then the pool mode is best used. My picture below is with the petstore servers without having a pool attached to the virtual server.
Now I have other issues as after intergrating with Azure AD as oauth provider and a sync of the public keys that are at https://login.microsoftonline.com/common/discovery/keys I see the F5 APM getting the keys every hour and they are correct but when I request a token with postman and get a correct token that I have checked at https://jwt.io/ the APM things that there is no valid key that signed the token but this seems like a Job for the support hah as the key is in the APM after I checked.
Nov 8 18:16:15 bigip1.com err apmd[12601]: 01490290:3: /Common/API-PETS_ap::77A02581./Common/oauth/HYQYY5JU7+XxiUmSSuLWgsiAtUEug9m2c9njSNvseiQ=:/Common/oauth_act_oauth_scope_subsession_ag: OAuth Scope: failed for jwt-provider-list '/Common/exampleJWTProvider' , error: None of the configured JWK keys match the received JWT token, JWT Header: eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6IjJaUXBKM1VwYmpBWVhZR2FYRUpsOGxWMFRPSSJ9
I even dumped the token with a subsession variable just to see if the APM is getting the correct one with variable assign agent in the Per-Request API protection policy " subsession.logon.last.jwt = expr { "[mcget {request.header.authorization}]"} " and the logging agent " %{subsession.logon.last.jwt} " and it is the the same one in Postman and valid so enough of the support was done by me 🙂
I am closing this and as a recommendation an external DNS resolver going to an IP address not on the same F5 device needs to be configured. I may create an iRule and community Tech Article with TCP::collect and TCP::respond to see if this can be bypassed but that is in the future.
Edit:
I even checked when the web browser clients are using authorization codes and F5 exchanges them with Azure AD for tokens and validates them it works normally without an issue ( with https://support.f5.com/csp/article/K07645403 the tokens the F5 per-request policy gets under "subsession.oauth.client.last.access_token" can be decrypted but a logging agent is used as the per-request policy does not have message agent ) but when tokens are send directly to the F5 with postman for API protection well it seems a bug to me.
Zdravo Niki,
I am pretty sure this won't work. API Protection is using a combination of HTTP methods and URIs to build a so called "path". Once a client is accessing this path, the APM will respond (for example with HTTP status 429 Too many requests). However, it's all HTTP.
DNS Requests are... not HTTP. Hence API Protection won't do anything to them.
DoH might be a different story....
Pozdrav
Daniel
Hello Daniel_Wolf I agree that this is not for DNS but HTTP traffic as I am not trying to do API Protection for a DNS traffic but web traffic but I think that the DNS resolver in the API protection still needs to do the DNS resolution on the server objects that are configured and related to each URI/Path before sending the HTTP/HTTPS traffic to the servers and as I am using the same F5 box for DNS resolution where the F5 APM API protection is located I think I am hitting a wall with this rare case where the DNS server in the DNS resolver is not an external DNS server but a local DNS lisener.
I could be wrong as I just started playing with API Protection but as the DNS resolver is a requered object in the API Protection profile and for the server objects you can't add directly just the server IP address but it should something like http://x.x.x.x/ this is why I think the DNS resolution just does not work when trying to make the DNS call as F5 will reply to itself using the loopback and this be the issue.
I think I saw similar issue in a Advanced WAF Bot defense profile long ago for a DNS resolver having an IP address of a DNS virtual server/lisener as the configured DNS server on the same F5 box where the WAF was located.
Recent Discussions
Related Content
* Getting Started on DevCentral
* Community Guidelines
* Community Terms of Use / EULA
* Community Ranking Explained
* Community Resources
* Contact the DevCentral Team
* Update MFA on account.f5.com