ViewSubscriber with page caching - Denial of Service (SA-CONTRIB-2013-042)

Problem/Motivation

SA-CONTRIB-2013-042 - RESTful Web Services (RESTWS) - Denial of Service is also present in Drupal 8 core.

Since Drupal's page cache uses only the URL as a cache ID (not the HTTP Accept header), cached JSON responses can get accidentally served to HTML clients and vice-versa.

This enables a denial-of-service attack where an attacker could populate the target's cache with JSON responses, essentially transforming the site into jibberish for the majority of visitors.

Steps to reproduce:

• Install Drupal 8 core
• create a node
• Enable "Use internal page cache" (admin/config/development/performance), set minimum age >= 1 minute
• Run curl -H'Accept:application/json' http://example.com/node/1
• Visit http://example.com/node/1 in your browser as an anonymous user

Expected result: The browser should show the normal HTML page.
Actual result: The cached JSON output is sent.

Proposed resolution

Possible solutions are proposed in these related issues:
#1303010: Page cache only uses URL as cache ID, not HTTP Accept headers or language
#1597696: Consider whether HttpCache offers any significant benefit over the existing page cache

This issue is to track the advisory follow-up specifically, as well as any changes needed to ViewSubscriber should the above solution(s) get implemented.

Remaining tasks

Patch needed.

User interface changes

N/A

API changes

???