The API Challenges Mirror Mode shows you the HTTP request that you sent to the API server, an easy way to see if your REST API tool is performing as instructed or did it amend your request in ways you didn't expect? Did it add extra headers, or worse, remove headers that you wanted to include?
Mirror Mode
The API has a mirror mode, this allows you to experiment with different verbs and configurations.
You will see, in your API tool, a response showing you the details of the request that you sent.
There are two mirror end points:
mirror/requestmirror/raw
The mirror/request end point will try to honour the accept: header in the response, so if you ask for application/json then the response will be json format.
The mirror/raw end point will always send the request back as raw text format.
This endpoint can be very useful for seeing what your HTTP Rest Client is sending to the server. You can spot any additional http headers that the client has added and see if the HTTP Client has combined any headers, or dropped any headers.
Accessing The Mirror Mode
To access the mirror mode on the public cloud make requests to:
- https://apichallenges.eviltester.com/mirror/request
- https://apichallenges.eviltester.com/mirror/raw
Request EndPoint
e.g. to use the request endpoint:
GET https://apichallenges.eviltester.com/mirror/request
Will return 200... everything (almost) returns a 200.
The mirror/request endpoint will use the Accept header to format the response.
If you want the response in XML or JSON then add the relevant Accept header.
e.g.
GET /mirror/request HTTP/1.1
Accept: application/json
Content-Length: 0
Host: localhost:4567
Would return the response as json
HTTP/1.1 200 OK
Date: Sat, 17 Feb 2024 13:09:34 GMT
Content-Type: application/json
access-control-allow-origin: *
x-challenger: x-challenger-guid
access-control-allow-headers: *
Server: Jetty(9.4.12.v20180830)
Content-Length: 320
{
"details":"GET https://apichallenges.eviltester.com/mirror/request
\n\nQuery Params\n==..."
}
Raw EndPoint
e.g. to use on the public cloud version of apichallenges:
GET https://apichallenges.eviltester.com/mirror/raw
GET /mirror/raw HTTP/1.1
Accept: application/json
Content-Length: 0
Host: localhost:4567
Will return 200.
The mirror/raw endpoint will not use the Accept header to format the response and will always return a text representation.
HTTP/1.1 200 OK
Date: Sat, 17 Feb 2024 13:13:58 GMT
Content-Type: text/plain
access-control-allow-origin: *
x-challenger: x-challenger-guid
access-control-allow-headers: *
Server: Jetty(9.4.12.v20180830)
Content-Length: 276
GET https://apichallenges.eviltester.com/mirror/raw
Query Params
============
IP
=======
127.0.0.1
Raw Headers
=======
Accept: application/json
Content-Length: 2
Host: apichallenges.eviltester.com
Processed Headers
=======
host: localhost:4567
content-length: 2
accept: application/json
Body
====
OPTIONS, HEAD
Only options and head respond differently... because options and head should respond differently.
Useful for getting started and getting used to your tooling.
Why is this Mirror Mode Useful?
The mirror mode is another way of seeing the 'true' request received.
You can configure most API tools to use a Proxy like BurpSuite or OwaspZAP and you will see the actual request that the tool sends.
You can also use the Insomnia Timeline to see the request.
In Postman you can use the Postman Console to see the requests.
The Mirror Mode shows you the request received by the server. When run on Localhost there are no intermediate systems so you can see what the tooling sends in the logs.
When run on apichallenges.eviltester.com you see that the Cloud environment adds additional headers in to the request.
Additionally the REST Client we use may add or amend headers.
Very often we are not aware of this level of amendment when testing and may not test for this.
The Mirror mode makes it clear that there are multiple systems involved in issuing a request and they can all pose a risk to the system or our testing. e.g. some REST Clients will not send duplicate headers: some will combine headers, some will pick the first (or last) header.
Swagger OpenAPI File
You can download a simple Swagger OpenAPI File for mirror mode.