How To Use Proxies With Invalid Certificates

If you've found an SSL proxy but your browser won't allow you to access it, it's not the end of the world. Usually, these proxy sites are run by administrators who cannot afford to have their certificates signed by a company like Trustwave, or Verisign, but wish to offer their proxy to the public to use. This is the case, more often than not. You can access these proxies by setting your permissions within your browser. Below is a typical error you'll see when trying to access a proxy site which has an invalid certificate. The web page won't load, but if you'll notice at the bottom left hand side of the error, the words, "Or you can add an exception..." This is the key to accessing the proxy with an invalid certificate. Click the link, and you'll be taken to the next page.

Your browser still displays the error, but this time it gives you a reason as to why you should not add an exception to your browser. This warning should be followed if you usually access a site fine, but you this error pops up suddenly one day. This could mean the server has been compromised. However, in the case of many proxy servers, it simply means the certificate has been self-signed and has to be allowed in your browser.

Once you click the Add Exception button, you'll be presented with the a window which describes why the proxy is invalid. This window allows you to one last chance to get a valid security certificate for the site. You'll see the address of the website in the Location box. Click Get Certificate, and FireFox will tell you the status of the certificate.

When attempting to validate the site, FireFox can return three errors. The first, Wrong Site, indicates that the certificate belongs to another site entirely. This could mean the certificate has been stolen and is being used in a separate location other than the one you tried to access it from. The second, Outdated Information, means the certificate is not valid, but Fire Fox cannot determine whether the identity was stolen or lost. The third error, Unknown Identity, means the certificate is not be trusted, because it hasn't been verified by a recognized authority.

When accessing proxies, you should only see two of these. The Outdated Information and Unknown Identity errors are common, and usually mean the proxy site has self-signed its certificate so that it can be considered secure. You should always watch for the Wrong Site error, as it usually  means a site's identity has been stolen.