Add support for Java 15

[normanmaurer]

Conscrypt seems to not work with the latest Java15 release:

Caused by: javax.net.ssl.SSLPeerUnverifiedException: Could not find class: java.lang.ClassNotFoundException: com/sun/security/cert/internal/x509/X509V1CertImpl
	at org.conscrypt.SSLUtils.toCertificateChain(SSLUtils.java:338)
	... 31 common frames omitted

This is most likely caused by:

openjdk/jdk@d243e40#diff-06dcd66603a23837e5639cdccee0d1ea

As this commit removed the class.

 /Users/norman/Downloads/jdk-15.jdk/Contents/Home/bin/java -version
openjdk version "15-ea" 2020-09-15
OpenJDK Runtime Environment (build 15-ea+20-899)
OpenJDK 64-Bit Server VM (build 15-ea+20-899, mixed mode, sharing)

This showed up while adding support for running our testsuite in netty with Java15:

netty/netty#10210

[prbprbprb]

This seems like an incomplete change on the openjdk end, they've removed X509V1CertImpl but kept javax.security.cert.X509Certificate whose getInstance method depends on it by reflection.

However javax.security.cert.X509Certificate is also deprecated in favour of java.security.cert.X509Certificate which doesn't allow construction in this manner. So this won't be a trivial fix if they remove the javax classes...

[normanmaurer]

@prbprbprb can you report this to the openjdk devs ?

[kruton]

Does OpenJDK 15 without Conscrypt also fail? It looks like the default implementation just throws UnsupportedOperationException. Maybe Conscrypt should have a Platform call for this that does the same on OpenJDK.

[normanmaurer]

@kruton Yes I think Conscrypt should also throw UnsupportedOperationException in case of JDK15+

[prbprbprb]

Looks like we can migrate to the java.security version of X509Certificate on all platforms

[yschimke]

ping: "JDK 15 is planned for release on September 15, 2020"

[yschimke]

Where did this end up?

[MiiSwi]

Seems like 2.7.0 is a far future goal. Java 15.0.1 is here but I can't use Conscrypt. Can't it be implemented more sooner?

[prbprbprb]

On the one hand, this easier than I first thought, there are only half a dozen uses of javax.security.cert.X509Certificate, all around SSLSession implementation classes and the rest of Conscrypt all uses java.security.cert.X509Certificate already.

On the other hand, on Android 6 and below, javax.net.ssl.SSLSession uses javax.security.cert.X509Certificate so there'll be some fun with wrappers to support it :/

[prbprbprb]

Actually my bad, so does current Android and openjdk1.8 so we'll have to make openjdk 15 the special case here