http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/proposals/229-further-socks5-extensions.html
References
Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., Jones L., "SOCKS
Protocol Version 5", RFC 1928, March 1996.
Tor Project, "Tor's extensions to the SOCKS protocol"
Leech, M. "Username/Password Authentication for SOCKS V5", RFC 1929,
March 1996.