RFR: 8298381: Improve handling of session tickets for multiple SSLContexts [v4]

Xue-Lei Andrew Fan xuelei at openjdk.org
Thu Dec 22 19:17:54 UTC 2022

On Thu, 22 Dec 2022 15:00:18 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>> Currently, TLS session tickets introduced by [JDK-8211018](https://bugs.openjdk.org/browse/JDK-8211018) in JDK 13 (i.e. `SessionTicketExtension$StatelessKey`) are generated in the class `SessionTicketExtension` and they use a single, global key ID (`currentKeyID`) for all `SSLContext`s.
>> This is problematic if more than one `SSLContext` is used, because every context which requests a session ticket will increment the global id `currentKeyID` when it creates a ticket. This means that in turn all the other contexts won't be able to find a ticket under the new id in their `SSLContextImpl` and create a new one (again incrementing `currentKeyID`). In fact, every time a ticket is requested from a different context, this will transitively trigger a new ticket creation in all the other contexts. We've observed millions of session ticket accumulating for some workloads.
>> Another issue with the curent implementation is that cleanup is racy because the underlying data structure (i.e. `keyHashMap` in `SSLContextImpl`) as well as the cleanup code itself are not threadsafe.
>> I therefor propose to move `currentKeyID` into the `SSLContextImpl` to solve these issues.
>> The following test program (contributed by Steven Collison (https://raycoll.com/)) can be used to demonstrate the current behaviour. It outputs the number of `StatelessKey` instances at the end of the program. Opening 1000 connections with a single `SSLContext` results in a single `StatelessKey` instance being created:
>> $ java -XX:+UseSerialGC -Xmx16m -cp ~/Java/ SSLSocketServerMultipleSSLContext 9999 1 1000
>> 605:             1             32  sun.security.ssl.SessionTicketExtension$StatelessKey (java.base at 20-internal)
>> The same example with the 1000 connections being opened alternatively on thwo different contexts will instead create 1000 `StatelessKey` instances:
>> $ java -XX:+UseSerialGC -Xmx16m -cp ~/Java/ SSLSocketServerMultipleSSLContext 9999 2 1000
>>   11:          1000          32000  sun.security.ssl.SessionTicketExtension$StatelessKey (java.base at 20-internal)
>> With my proposed patch, the numbers goes back to two instances again:
>> $ java -XX:+UseSerialGC -Xmx16m -cp ~/Java/ SSLSocketServerMultipleSSLContext 9999 2 1000
>> 611:             2             64  sun.security.ssl.SessionTicketExtension$StatelessKey (java.base at 20-internal)
>> I've attached the test program to the [JBS issue](https://bugs.openjdk.org/browse/JDK-8298381). If you think it makes sense, I can probably convert it into a JTreg test.
> Volker Simonis has updated the pull request incrementally with one additional commit since the last revision:
>   Moved stateless key logic from SSLContextImpl to SSLSessionContextImpl and addressed comments by @XueleiFan and @ascarpino

src/java.base/share/classes/sun/security/ssl/SSLSessionContextImpl.java line 95:

> 93:             // Should be "randomly generated" according to RFC 5077,
> 94:             // but doesn't necessarily has to be a true random number.
> 95:             currentKeyID = this.hashCode();

As the hashCode() is called in the constructor, I'm not very sure if it works as expected.   Maybe, the system nano time could be used instead.

src/java.base/share/classes/sun/security/ssl/SSLSessionContextImpl.java line 97:

> 95:             currentKeyID = this.hashCode();
> 96:         } else {
> 97:             keyHashMap = null;

I may use an unmodifiable empty map so that we don't have to worry about null pointer exception.

`keyHashMap = Map.of();`

src/java.base/share/classes/sun/security/ssl/SessionTicketExtension.java line 163:

> 161:             SSLSessionContextImpl serverCache =
> 162:                 (SSLSessionContextImpl)hc.sslContext.engineGetServerSessionContext();
> 163:             return serverCache.getKey();

I think the `HandshakeContext hc` could be passed as a parameter for the getKey() method, and thus you have a way to get the secure random for StatelessKey().

      return serverCache.getKey(hc);
->     SessionTicketExtension.StatelessKey getKey(HandshakeContext hc) {
->     ssk = new SessionTicketExtension.StatelessKey(hc, newID);
->     StatelessKey(HandshakeContext hc, int newNum) {
->     kg.init(KEYLEN, hc.sslContext.getSecureRandom());


PR: https://git.openjdk.org/jdk/pull/11590

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