[Apache HTTP Client] Stop auto-enabling TLS protocol versions #2934

Bennett-Lynch · 2021-12-22T03:34:10Z

Motivation

Since 2014, in the Java SDK v1, the SDK's Apache HTTP Client has auto-enabled certain TLS protocol versions if they are supported by the local system. The versions auto-enabled are: TLSv1.2, TLSv1.1, TLSv1, and TLS. The original motivation was to always try to use the latest and most secure version. This made sense at the time, especially when both Java 6 and Java 7 defaulted to only TLSv1.0. It wasn't until Java 8 that the default became TLSv1.2. So there was some apparent value in the SDK nudging clients towards the latest version that they may otherwise be slow to adopt.

Java Version	Release Date	SSL/TLS Default	Other Supported Versions
Java 6	December 2006	TLS 1.0	TLS 1.1 (update 111 and later), SSLv3.0*
Java 7	July 2011	TLS 1.0	TLS 1.2, TLS 1.1, SSLv3.0*
Java 8	March 2014	TLS 1.2	TLS 1.1, TLS 1.0, SSLv3.0*

sources: [1] [2]

Fast-forward 7+ years and most JVM vendors now enable newer TLS versions (TLSv1.3) by default and many of the above versions are now considered older and less secure, yet the SDK continues to auto-enable them. Furthermore, the Java SDK v2 requires Java 8 or higher, which has an implicit guarantee of defaulting to TLSv1.2 or higher, meaning these SDK-enabled versions are never newer than default version.

While the TLS negotiation will resolve to the highest mutually supported version, some users may still wish to explicitly disable older versions as an extra precaution. The recommended and conventional way to do this is via the jdk.tls.client.protocols system property, but the SDK's implementation will continue to append its own list of enabled versions to the user's declared list. The only way for users to ensure they disable those versions is via the jdk.tls.disabledAlgorithms system property.

https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/security-java-tls.html

https://java.com/en/configure_crypto.html

Since the SDK's list of preferred TLS versions is no longer up to date, and any new preferences would be similarly subject to becoming stale in the future, the SDK should stop trying to offer opinions on the preferred TLS version to use and instead allow the JVM defaults and user-declared properties to fully control this behavior.

Modifications

Stop appending TLS versions to the list of enabled protocol versions.

License

I confirm that this pull request can be released under the Apache 2 license

## Motivation Since 2014, in the Java SDK v1, the SDK's Apache HTTP Client has auto-enabled certain TLS protocol versions if they are supported by the local system. The versions auto-enabled are: `TLSv1.2`, `TLSv1.1`, `TLSv1`, and `TLS`. The original motivation was to always try to use the latest and most secure version. This made sense at the time, especially when both Java 6 and Java 7 defaulted to only `TLSv1.0`. It wasn't until Java 8 that the default became `TLSv1.2`. So there was some apparent value in the SDK nudging clients towards the latest version that they may otherwise be slow to adopt. Fast-forward 7+ years and most JVM vendors now enable newer TLS versions by default and many of the above versions are now considered older and less secure, yet the SDK continues to auto-enable them. Furthermore, the Java SDK v2 requires Java 8 or higher, which has an implicit guarantee of defaulting to `TLSv1.2` or higher, meaning these SDK-enabled versions are never newer than default version. While this isn't strictly a security concern (because the TLS negotiation will resolve to the highest mutually supported version), some users may still wish to explicitly disable older versions as an extra precaution. The recommended and conventional way to do this is via the `jdk.tls.client.protocols` system property, but the SDK's implementation will continue to append its own list of enabled versions to the user's declared list. The only way for users to ensure they disable those versions is via the `jdk.tls.disabledAlgorithms` system property. Since the SDK's list of preferred TLS versions is no longer up to date, and any new preferences would be similarly subject to becoming stale in the future, the SDK should stop trying to offer opinions on the preferred TLS version to use and allow the JVM defaults and user-declared properties to control this behavior. https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/security-java-tls.html https://java.com/en/configure_crypto.html ## Modifications * Stop appending TLS versions to the list of enabled protocol versions.