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How to use HAProxy ACL with Cookies

Did you know that ACLs in HAProxy are used to make routing decisions and apply rules according to different criteria?

ACLs allow us to inspect and manipulate HTTP cookies in requests or responses. This comes in handy to control traffic based on the presence, absence, or value of specific cookies.

Let’s take a look at how to use HAProxy ACLs with cookies:

1. 1. First, we have to define an ACL that matches specific cookie attributes. This involves using the acl keyword followed by a name for the ACL and a condition that specifies the cookie attributes we want to match.

      For example:

      acl has_session_cookie hdr_sub(cookie) SESSION_ID=

      Here, we define an ACL named has_session_cookie that checks whether the HTTP request headers contain a cookie named SESSION_ID.
   2. Then, we can use the ACL in our HAProxy configuration to make routing decisions or apply actions based on the presence or value of the cookie.

      For example:

      use_backend session_backend if has_session_cookie

      Here, if the has_session_cookie ACL condition is met, HAProxy will route the traffic to the session_backend.
   3. Furthermore, we can manipulate cookies in HAProxy with the set-cookie action and ACLs. For example, you can set or modify cookies based on certain conditions.

      For example:

      http-response set-cookie SESSION_ID=123 if is_authenticated

      Here, the set-cookie action sets the SESSION_ID cookie to “123” in the HTTP response if the is_authenticated ACL condition is met.
   4. Additionally, HAProxy ACLs offer flexibility in cookie matching. We can use operators to search for substrings within cookie values.

      For example:

      acl is_admin_cookie hdr_sub(cookie) admin=true

      Here, the is_admin_cookie ACL matches requests where the admin attribute within the cookie is set to “true.”

At the end of the day, using HAProxy ACLs with cookies is a powerful way to manage and control traffic based on cookie-related criteria.

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Conclusion

In brief, our Support Experts introduced us to using HAProxy ACL with Cookies and how helpful they are.