I use a wireless network at a library which requires me to login and authenticate through a web-browser login form. Once I log in, how can I find what the details of the proxy are (IP, proxy type and port)?
I am on a Ubuntu 12 machine.
Assuming by 'the proxy' you mean you think the library implements an authenticating proxy to provide you Internet access? Actually what generally will happen is after authenticating, your MAC address is permitted direct access (via the libraries gateway router) to the Internet. Determine your path to a website with:
The proxy server will be one of if not the first 'hop' to an Internet address.
Try to match this up with the domain/address of the page you are redirected to in the first place to login to the proxy server. Remember not all network protocols such as IM will work over proxy servers - you might need to 'tunnel' these programs through the proxy using something like SOCKS.
If the browser can connect to all web sites, no proxy configuration is needed for it and any other programsrunning on the HTTP port 80.
Have you considered asking them? They might tell you right away that chatting / file sharing / your_favourite_tool is not welcome, or they might just tell you where/how to connect.
Have a look at SOCKS 5 proxies running on the HTTP port, often called HTTP Tunnel. You might be able to redirect all your non-browser traffic through it, and your library will very likely not block it.