RFR: 8298381: Improve handling of session tickets for multiple SSLContexts [v6]

[Sergey Bylokhov]

On Tue, 3 Jan 2023 17:45:12 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:
> 
>   Updated copyright year to 2023

src/java.base/share/classes/sun/security/ssl/SSLSessionContextImpl.java line 199:

> 197:                 it.remove();
> 198:                 try {
> 199:                     k.key.destroy();

Is it safe to assume that "key.destroy()" is threadsafe?

src/java.base/share/classes/sun/security/ssl/SSLSessionContextImpl.java line 209:

> 207:     // Package-private, used only from SessionTicketExtension.KeyState::getCurrentKey.
> 208:     SessionTicketExtension.StatelessKey getKey(HandshakeContext hc) {
> 209:         SessionTicketExtension.StatelessKey ssk = keyHashMap.get(currentKeyID);

is it safe to assume that the "currentKeyID" initialized/updated before on a different thread can be correctly read here?

src/java.base/share/classes/sun/security/ssl/SSLSessionContextImpl.java line 220:

> 218:                 return ssk;
> 219:             }
> 220:             int newID = currentKeyID + 1;

Do we actually want to support the whole range of ints here? Probably some limitations can be applied?

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