tls, binding: backport of process.binding('config') and regression fix

doc/api/process.md

@@ -375,6 +375,10 @@ An example of the possible output looks like:
 }
 ```
 
+*Note: the `process.config` property is **not** read-only and there are existing
+modules in the ecosystem that are known to extend, modify, or entirely replace
+the value of `process.config`.*
+
 ## process.connected
 
 * {Boolean} Set to false after `process.disconnect()` is called

lib/_tls_wrap.js

@@ -19,7 +19,7 @@ const defaultSessionIdContext = getDefaultSessionIdContext();
 function getDefaultSessionIdContext() {
   var defaultText = process.argv.join(' ');
   /* SSL_MAX_SID_CTX_LENGTH is 128 bits */
-  if (process.config.variables.openssl_fips) {
+  if (process.binding('config').fipsMode) {
     return crypto.createHash('sha1')
       .update(defaultText)
       .digest('hex').slice(0, 32);

node.gyp

@@ -124,6 +124,7 @@
         'src/js_stream.cc',
         'src/node.cc',
         'src/node_buffer.cc',
+        'src/node_config.cc',
         'src/node_constants.cc',
         'src/node_contextify.cc',
         'src/node_file.cc',

src/node_config.cc

@@ -0,0 +1,39 @@
+#include "node.h"
+#include "env.h"
+#include "env-inl.h"
+#include "util.h"
+#include "util-inl.h"
+
+
+namespace node {
+
+using v8::Context;
+using v8::Local;
+using v8::Object;
+using v8::Value;
+using v8::ReadOnly;
+
+// The config binding is used to provide an internal view of compile or runtime
+// config options that are required internally by lib/*.js code. This is an
+// alternative to dropping additional properties onto the process object as
+// has been the practice previously in node.cc.
+
+#define READONLY_BOOLEAN_PROPERTY(str)                                        \
+  do {                                                                        \
+    target->DefineOwnProperty(env->context(),                                 \
+                              OneByteString(env->isolate(), str),             \
+                              True(env->isolate()), ReadOnly).FromJust();     \
+  } while (0)
+
+void InitConfig(Local<Object> target,
+                Local<Value> unused,
+                Local<Context> context) {
+#ifdef NODE_FIPS_MODE
+  Environment* env = Environment::GetCurrent(context);
+  READONLY_BOOLEAN_PROPERTY("fipsMode");
+#endif
+}
+
+}  // namespace node
+
+NODE_MODULE_CONTEXT_AWARE_BUILTIN(config, node::InitConfig)