Add SSLContext to OpenSSL SSL_CTX ex data

Summary: Adding SSLContext members to SSL_CTX ex data to access them inside callbacks attached to SSL_CTX (e.g. session callbacks)

Reviewed By: yfeldblum, mingtaoy

Differential Revision: D21021353

fbshipit-source-id: 6aa3995f7d719ca7e87bad798876a92dd5765b86

folly/io/async/SSLContext.cpp

@@ -27,6 +27,20 @@
 // ---------------------------------------------------------------------
 // SSLContext implementation
 // ---------------------------------------------------------------------
+namespace {
+
+int getExDataIndex() {
+  static auto index =
+      SSL_CTX_get_ex_new_index(0, nullptr, nullptr, nullptr, nullptr);
+  return index;
+}
+
+void setExData(folly::SSLContext* context, SSL_CTX* ctx) {
+  SSL_CTX_set_ex_data(ctx, getExDataIndex(), context);
+}
+
+} // namespace
+
 namespace folly {
 //
 // For OpenSSL portability API
@@ -78,6 +92,8 @@ SSLContext::SSLContext(SSLVersion version) {
 
   sslAcceptRunner_ = std::make_unique<SSLAcceptRunner>();
 
+  setExData(this, ctx_);
+
 #if FOLLY_OPENSSL_HAS_SNI
   SSL_CTX_set_tlsext_servername_callback(ctx_, baseServerNameOpenSSLCallback);
   SSL_CTX_set_tlsext_servername_arg(ctx_, this);
@@ -143,6 +159,7 @@ void SSLContext::setServerECCurve(const std::string& curveName) {
 }
 
 SSLContext::SSLContext(SSL_CTX* ctx) : ctx_(ctx) {
+  setExData(this, ctx);
   if (SSL_CTX_up_ref(ctx) == 0) {
     throw std::runtime_error("Failed to increment SSL_CTX refcount");
   }
@@ -655,6 +672,10 @@ void SSLContext::enableTLS13() {
 #endif
 }
 
+SSLContext* SSLContext::getFromSSLCtx(const SSL_CTX* ctx) {
+  return static_cast<SSLContext*>(SSL_CTX_get_ex_data(ctx, getExDataIndex()));
+}
+
 std::ostream& operator<<(std::ostream& os, const PasswordCollector& collector) {
   os << collector.describe();
   return os;

folly/io/async/SSLContext.h

@@ -559,6 +559,11 @@ class SSLContext {
    */
   void enableTLS13();
 
+  /**
+   * Get SSLContext from the ex data of a SSL_CTX.
+   */
+  static SSLContext* getFromSSLCtx(const SSL_CTX* ctx);
+
   [[deprecated("Use folly::ssl::init")]] static void initializeOpenSSL();
 
  protected:

folly/io/async/test/SSLContextTest.cpp

@@ -179,4 +179,15 @@ TEST_F(SSLContextTest, TestLoadCertificateChain) {
   EXPECT_EQ(1, sk_X509_num(stack));
 }
 
+TEST_F(SSLContextTest, TestGetFromSSLCtx) {
+  // Positive test
+  SSLContext* contextPtr = SSLContext::getFromSSLCtx(ctx.getSSLCtx());
+  EXPECT_EQ(contextPtr, &ctx);
+
+  // Negative test
+  SSL_CTX* randomCtx = SSL_CTX_new(SSLv23_method());
+  EXPECT_EQ(nullptr, SSLContext::getFromSSLCtx(randomCtx));
+  SSL_CTX_free(randomCtx);
+}
+
 } // namespace folly