Within a web browser, is it possible for JavaScript to obtain information about the HTTPS Certificate being used for the current page?

Question

Is there a method for JavaScript running in a browser to determine which CA certificate is being used to authenticate the remote host for the browser's current HTTPS connection, and also obtain properties of that certificate, such as the name of the CA?

If not, are there any other options for programatically obtaining this information, such as ActiveX, Java, CGI on the server side, ...?

Answer 1

You can use the opensource Forge project to do this. It implements SSL/TLS in JavaScript. You can make an ajax call to the server and use a callback to inspect the certificate. Keep in mind that the server is the one sending the JavaScript so this shouldn't be used to determine whether or not you trust the server the JavaScript is from. The Forge project does allow cross-domain requests, so if you are using this for trust, you can load the Forge JavaScript from a server you already trust and then contact the server you don't yet trust. However, unless that other server provides a cross-domain policy, you will not be able to perform the cross-domain request.

https://github.com/digitalbazaar/forge/blob/master/README.md

The blog links in the README provide more information on how Forge can be used and how it works.