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Historical question as BEAST is mitigated in TLS 1.1 and earlier TLS is deprecated.

BEAST is a chosen plaintext attack, possible in web browsers because cross-origin requests have cookies automatically attached. This puts both attacker-controlled data and sensitive data in the same encryption context, making chosen plaintext attacks possible.

If an application uses the authorisation header to transmit the session token, instead of cookies, then tokens are not automatically attached and such an attack would apparently (to my eyes) not be possible.

I understand we'd still want to migrate to newer versions of TLS, but this would have been a reasonable "sticking plaster" mitigation. Is there any reason we did not see this at the time?

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    $\begingroup$ Chosen plaintext are also possible in other ways, so the protocol needed to be fixed anyway. And fixing things at higher level - possibly on a per site basis - seems much harder to me than updating the transport protocol by updating a library. That said, I'm not sure that "this wasn't seen" and I was not part of the update at that time, so this is just conjecture. $\endgroup$
    – Maarten Bodewes ♦
    Commented Sep 9 at 10:09
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    $\begingroup$ See also Is there a way to mitigate BEAST without disabling AES completely? $\endgroup$
    – Sjoerd
    Commented Sep 9 at 10:39

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Is there any reason we did not see this at the time?

Providing authentication credentials in way that they are not automatically sent, such as in the Authorization header, is only possible with a single page application (SPA). In a SPA, the application loads once and performs requests using JavaScript, which also attaches the authentication credentials. The page can keep the credentials in a JavaScript variable or in web storage. Single page applications were not popular yet when BEAST was discovered. Most websites used separate pages with cookie authentication, and it would not be possible to convert these to use an authorization header.

  • 2010: JWT specification
  • 2010: AngularJS
  • 2011: BEAST attack
  • 2015: Web storage widely supported
  • 2016: Same-site cookies

Google Trends show that searches for "single page applications" were low in september 2011 when BEAST was discovered.

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