Tuesday , 17 July 2018
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Verifying and testing that Firefox is restricted to TLS 1.2

TLS is the protocol invoked under the covers when viewing secure websites (those loaded with HTTPS rather than HTTP). There are multiple versions of the TLS protocol, and the most recent version, 1.2, is the most secure. Last time, I discussed tweaking Firefox so that it only supports TLS version 1.2 and not the older versions (1.0 and 1.1) of the protocol.

But that begs the question: what happens when a security-reinforced copy of Firefox encounters a website that does not support TLS 1.2? The answer is shown below.

firefox.unsupported.ssl.version2Michael Horowitz

The error message from Firefox 54 when a website does not support TLS 1.2 and it only supports TLS 1.2

For the benefit of search engines, the error reads

Secure Connection Failed.

An error occurred during a connection to [website name]. Peer using unsupported version of security protocol. Error code: SSL_ERROR_UNSUPPORTED_VERSION

The security protocol it refers to is TLS. There are three problems, however, with this Firefox error message.

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