DNS Proxy

DNS proxy listens for incoming DNS requests (A,NS,MX,TXT,SRV..) on the local interface (UDP only) and resolves using an external PHP script, through simple HTTP requests.

If you can't use tunnels to resolve names externally (i.e. TOR users), DNS proxy is a simple and efficient solution.

To work, it needs to know a PHP-enabled external server, completeley TOR-friendly.

Building

For debian/ubuntu users:

apt-get install libcurl4-openssl-dev

then

gcc dnsp.c -lcurl -g -lpthread -DTLS -o dnsp -rdynamic

Usage

dnsp -p 53 -l 127.0.0.1 -h 127.0.0.1 -r 8118 -w 80 -s https://www.fantuz.net/nslookup.php

In this example, DNS proxy listens on local UDP port 53 and sends the HTTPed requests to PHP external script through the 10.0.0.2:8080 proxyi (TORed ?).

IMPORTANT: Please, don't use the script hosted on my server as demonstration. It might be subjected to umpredicted change, offlining, deface. Instead - host yourself the nslookup.php script, and spread it on a friend's server! The more we are, the less DNS becomes a 'trackable' TOR leak.

 dnsp 1.01
 usage: dnsp -l [local_host] -h [proxy_host] -r [proxy_port] -w [webport] \
	-s [lookup_script] -t [stack_size]

 OPTIONS:
      -l		 Local server address
      -p		 Local server port
      -h		 Remote proxy address
      -r		 Remote proxy port
      -u		 Proxy username (optional)
      -k		 Proxy password (optional)
      -s		 Lookup script URL
      -w		 Webserver port (optional, default 80)
      -t		 Stack size in format 0x1000000 (MB)
      -v		 Enable juicy DEBUG logging

 Example: dnsp -p 53 -l 127.0.0.1 -h 127.0.0.1 -r 8118 -w 80 \
	-s https://www.fantuz.net/nslookup.php -t 0x1000000

Testing

To test if DNS proxy is working correctly, first run the program as following, by filling in Your favorite TOR proxy address:

dnsp -l 127.0.0.1 -h 127.0.0.1 -r 8118 -w 443 -s http://www.fantuz.net/nslookup.php

then, try to resolve an hostname using the dig command:

dig www.google.com @127.0.0.1

The result must be something like this:

; <<>> DiG 9.8.1-P1 <<>> www.google.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29155
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.google.com. 		IN	A

;; ANSWER SECTION:
www.google.com.		3600	IN	A	173.194.64.106

;; Query time: 325 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri May 17 11:52:08 2013
;; MSG SIZE  rcvd: 48

When You properly implement cache on the webserver, answers will come back in few milliseconds, after the first recursive resolution.

Changelog:

Version 1.01 - April 2015:

• HTTPS resolver support (even more privacy)
• Multithreading listener/responder
• Better nginx/polipo setup
• Stack size option
• Will add TCP listener/responder soon
• Some issue to set the proper ETag on polipo

Version 0.99 - July 2014:

• Add HTTP port selection
• Add NS, MX, AAAA, PTR, CNAME and other resolving capabilities.
• Code cleanup and performance review.
• Implementation with nginx and memcache and load testing

Version 0.5 - May 17 2013:

• Add proxy authentication support
• port option is now optional (default is 53)
• Fixed compilation error
• Minor bug fixes

Version 0.4 - November 16 2009:

• Now using libCurl for http requests
• Implemented concurrent DNS server
• Bug fixes
• Code clean

Version 0.1 - April 09 2009:

• Initial release