Fix unconstrained session cache growth in TLSv1.3 (3.1/3.0) #24044
+351
−13
Commits on Apr 5, 2024
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Add a test for session cache handling
Repeatedly create sessions to be added to the cache and ensure we never exceed the expected size. Related to CVE-2024-2511
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Extend the multi_resume test for simultaneous resumptions
Test what happens if the same session gets resumed multiple times at the same time - and one of them gets marked as not_resumable. Related to CVE-2024-2511
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Fix unconstrained session cache growth in TLSv1.3
In TLSv1.3 we create a new session object for each ticket that we send. We do this by duplicating the original session. If SSL_OP_NO_TICKET is in use then the new session will be added to the session cache. However, if early data is not in use (and therefore anti-replay protection is being used), then multiple threads could be resuming from the same session simultaneously. If this happens and a problem occurs on one of the threads, then the original session object could be marked as not_resumable. When we duplicate the session object this not_resumable status gets copied into the new session object. The new session object is then added to the session cache even though it is not_resumable. Subsequently, another bug means that the session_id_length is set to 0 for sessions that are marked as not_resumable - even though that session is still in the cache. Once this happens the session can never be removed from the cache. When that object gets to be the session cache tail object the cache never shrinks again and grows indefinitely. CVE-2024-2511
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Hardening around not_resumable sessions
Make sure we can't inadvertently use a not_resumable session Related to CVE-2024-2511
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Add a test for session cache overflow
Test sessions behave as we expect even in the case that an overflow occurs when adding a new session into the session cache. Related to CVE-2024-2511
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