artiliusjoker/proxy-server

A simple proxy server in C

proxy-server in C

Programming language: C/C++
OS: Linux (Kali distro)
Multi processes

Turn on proxy

foo@bar:~$ make all
foo@bar:~$ exe/1712695 8888
#or
foo@bar:~$ exe/1712695 8888 filter_string

Turn off proxy

foo@bar:~$ pkill 1712695 --signal 12

1. GET/HEAD

• GET request from web browser (FF or Chrome)
  Test case: http://example.com/, http://students.iitk.ac.in/gymkhana/, http://phthiraptera.info/
  Result: browser display the requested web sites

• GET request from curl
  Test case: $ curl -v --proxy localhost:8888 http://www.hcmus.edu.vn
  Result: browser display the requested web sites

• HEAD request from curl
  Test case: $ curl -v --proxy localhost:8888 -X HEAD http://www.hcmus.edu.vn
  Result: 200 (OK) HTTP header

2. Filltering URLs
   input : $ ./ 8888 fit.hcmus.edu

• Suffix filtering
  Test case: $ curl -v --proxy localhost:8888 http://www.fit.hcmus.edu/~lqvu/ -> missing suffix '.vn'
  Result: 403 (Forbidden) HTTP response. The proxy doesn't send the request to the web server
• Prefix Filtering
  Test case: $ curl -v --proxy localhost:8 888 http://fit.hcmus.edu.vn/~lqvu/ -> missing prefix 'www.'
  Result: 403 (Forbidden) HTTP reponse.
• Non-filtering case
  Test case: $ curl -v – proxy localhost:8888 http://www.fit.hcmus.edu.vn/~lqvu/ -> has prefix and suffix
  Result: 301 (Moved Permanently) or 302 (Found) HTTP response from web server

3. Simultaneously serve multiple requests
   Test case: $./conctest.sh
   (Script will open 4 terminals and each terminal will send a HTTP request to http://tuoitre.vn)
   Result: 200 (OK) HTTP reponses

4. Signal handling

• SIGUSR2 (5 points)
  Test case: $ pkill 1712695 --signal 12
  Result: Proxy shutdown
• SIGINT
  Test case: Ctrl-C while executing
  Result: Program ignore SIGINT

5. Memory leak

• Proxy side
  $ valgrind --leak-check=full --show-reachable=yes ./ 8888
• Client side
  $ curl -v --proxy localhost:8888 http://hcmus.edu.vn/
  Result:
  LEAK SUMMARY:
  definitely lost: 0 bytes in 0 blocks
  indirectly lost: 0 bytes in 0 blocks
  possibly lost: 0 bytes in 0 blocks
  still reachable: 0 bytes in 0 blocks
  suppressed: 0 bytes in 0 blocks

6. Only allow GET and HEAD methods
   Test case: $ curl -v --proxy localhost:8888 -X OPTIONS http://hcmus.edu.vn/
   Result: 405 (Method Not Allowed) or 501 (Not Implemented) HTTP response.
   Proxy build custom response and send to client, doesn't send the request to web server.

7. Non-HTTP request
   Bad HTTP request
   Test case: $ telnet localhost 8888
   <type ’abcdefg’ and enter>
   Result: Proxy ignores it and continue serving other requests