[MESOS-10013] Have fine grained control over OpenSSL dependency.

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.10.0
• Component/s: build, libprocess
• Labels: JWT OpenSSL foundations techdebt
• Story Points: 3
• Assignee: Unassigned
• Reporter: Till Toenshoff
• Created: 18/Oct/19 01:06
• Updated: 18/Oct/19 01:25

Description

We currently decide during the build configuration phase whether to link against OpenSSL or not. Whenever the developer enabled both  libevent+openssl, we internally signal via USE_SSL_SOCKET.

OpenSSL already provides more to us than only code used for TLS – our JWT handling also relies on OpenSSL.

We should consider cleaning this up. We could introduce another internal configuration signal, say HAVE_SSL. When configuring, the user could enable SSL without  libevent and get our JWT specific code but no TLS.

In our CMake code, we could replace  https://github.com/apache/mesos/blob/558829eb24f4ad636348497075bbc0428a4794a4/cmake/CompilationConfigure.cmake#L583-L586 with

if (ENABLE_SSL)
  add_definitions(-DHAVE_SSL=1)
  if (ENABLE_LIBEVENT)
    add_definitions(-DUSE_SSL_SOCKET=1)
  endif ()
endif () 

When -DENABLE_SSL gets supplied, the preprocessor would see HAVE_SSL. When the user supplies -DENABLE_SSL and -DENABLE_LIBVENT, the resulting set preprocessor defines would be USE_SSL_SOCKET and HAVE_SSL.