Go httperrors

This tool was designed for troubleshooting requests when behind a reverse proxy, primarily Cloudflare. It is a personal project that I use as a Technical Support Engineer. It can also be placed behind Cloudflare Access and cloudflared Tunnels for troubleshooting.

Install

go install github.com/dsundquist/httperrors@latest

Usage

To run the basic webserver (assuming that you haven't yet added ~/go/bin directory to your path, and that you'll be using the default port 80 which will require sudo):

sudo ~/go/bin/httperrors serve

If you wish to not use the default port of 80, you can start the http server on alternate port using the -p flag.

~/go/bin/httperrors serve -p 8080

If you want to run an https server you'll need a self signed certificate. You can run the following 2x commands:

openssl req  -new  -newkey rsa:2048  -nodes  -keyout server.key  -out server.csr
openssl  x509  -req  -days 365  -in server.csr  -signkey server.key  -out server.crt

The 2x files server.crt and server.key should be in the same directory has ./httperrors:

* local_directory: 
   |-> httperrors
   |
   |-> server.crt 
   |-> server.key 

Then one can run the serve command with a -s flag:

sudo ~/go/bin/httperrors serve -s

The CLI is built from Cobra, to see additional usage use the --help flag:

./httperrors serve --help

HTTP Server Behavior

The main page will just return back the request headers that the server had received. This can be useful for analysis when behind a reverse proxy or a product like Cloudflared

To use generate 5xx errors, for troubleshooting behind Cloudflare, visit:

http://localhost/help

The 522 Error Page

A 522 error is defined here: Cloudflare Support - 522 Error

The error occurs at the network level when:

1. Before a connection is established, the origin web server does not return a SYN+ACK to Cloudflare within 15 seconds of Cloudflare sending a SYN.
2. After a connection is established, the origin web server doesn’t acknowledge (ACK) Cloudflare’s resource request within 90 seconds.

Therefore we cannot complete this from the same server, as we need to sabatoge the server at the network level. In my implementation I have another simple http server listening on port 80, in which I'm redirect requests over to. At that server I've added an iptables drop rule that is dropping all ack packets to the listening port, recreated #2 above.

dsundquist:~$ sudo iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-A INPUT -i eth1 -p tcp -m tcp --dport 80 -j DROP
-A INPUT -i eth0 -p tcp -m tcp --dport 80 -j DROP

For that sabatoged HTTP server, I also have it programmed to 30 seconds, and two routes to reach it, one via its normal IP address (behind Cloudflare) and one over a cloudflared tunnel

Todo

• Organize HTTP HandleFunch methods in serve.go (maybe pull out the 5xx errors into another file) by alphabetical
• Implement / Finish mTLS server
• Building out the client side here (not sure of the use yet), maybe it'll just be easier to implement with the server (?)
• Client call shouldn't need a -l, call should be like httperrors client -k https://1.2.3.4/ instead of httperrors client -kl https://1.2.3.4/
• Added a /Vary, to test some headers, clean this up
• Added a /Cache, to test other headers, clean this up
• Make something like localhost/response?header1=value1&header2=value2 to specify response headers for testing random headers?
• Document all of the above in this README / --help