ssl: Add an SslCtxCb hook to Ssl::HandshakerFactory.

include/envoy/ssl/context_config.h

@@ -84,6 +84,11 @@ class ContextConfig {
    * @return the set of capabilities for handshaker instances created by this context.
    */
   virtual HandshakerCapabilities capabilities() const PURE;
+
+  /**
+   * @return a callback for configuring an SSL_CTX before use.
+   */
+  virtual SslCtxCb sslctxCb() const PURE;
 };
 
 class ClientContextConfig : public virtual ContextConfig {

include/envoy/ssl/handshaker.h

@@ -56,6 +56,9 @@ using HandshakerSharedPtr = std::shared_ptr<Handshaker>;
 using HandshakerFactoryCb =
     std::function<HandshakerSharedPtr(bssl::UniquePtr<SSL>, int, HandshakeCallbacks*)>;
 
+// Callback for modifying an SSL_CTX.
+using SslCtxCb = std::function<void(SSL_CTX*)>;
+
 class HandshakerFactoryContext {
 public:
   virtual ~HandshakerFactoryContext() = default;
@@ -115,6 +118,14 @@ class HandshakerFactory : public Config::TypedFactory {
    * capability.
    */
   virtual HandshakerCapabilities capabilities() const PURE;
+
+  /**
+   * Implementations should return a callback for configuring an SSL_CTX context
+   * before it is used to create any SSL objects. Providing
+   * |handshaker_factory_context| as an argument allows callsites to access the
+   * API and other factory context methods.
+   */
+  virtual SslCtxCb sslctxCb(HandshakerFactoryContext& handshaker_factory_context) const PURE;
 };
 
 } // namespace Ssl

source/extensions/transport_sockets/tls/context_config_impl.cc

@@ -234,6 +234,7 @@ ContextConfigImpl::ContextConfigImpl(
         factory_context.messageValidationVisitor());
   }
   capabilities_ = handshaker_factory->capabilities();
+  sslctx_cb_ = handshaker_factory->sslctxCb(handshaker_factory_context);
 }
 
 Ssl::CertificateValidationContextConfigPtr ContextConfigImpl::getCombinedValidationContextConfig(

source/extensions/transport_sockets/tls/context_config_impl.h

@@ -57,6 +57,7 @@ class ContextConfigImpl : public virtual Ssl::ContextConfig {
   void setSecretUpdateCallback(std::function<void()> callback) override;
   Ssl::HandshakerFactoryCb createHandshaker() const override;
   Ssl::HandshakerCapabilities capabilities() const override { return capabilities_; }
+  Ssl::SslCtxCb sslctxCb() const override { return sslctx_cb_; }
 
   Ssl::CertificateValidationContextConfigPtr getCombinedValidationContextConfig(
       const envoy::extensions::transport_sockets::tls::v3::CertificateValidationContext&
@@ -99,6 +100,7 @@ class ContextConfigImpl : public virtual Ssl::ContextConfig {
 
   Ssl::HandshakerFactoryCb handshaker_factory_cb_;
   Ssl::HandshakerCapabilities capabilities_;
+  Ssl::SslCtxCb sslctx_cb_;
 };
 
 class ClientContextConfigImpl : public ContextConfigImpl, public Envoy::Ssl::ClientContextConfig {

source/extensions/transport_sockets/tls/context_impl.cc

@@ -335,6 +335,14 @@ ContextImpl::ContextImpl(Stats::Scope& scope, const Envoy::Ssl::ContextConfig& c
     }
   }
 
+  // As late as possible, run the custom SSL_CTX configuration callback on each
+  // SSL_CTX, if set.
+  if (auto sslctx_cb = config.sslctxCb(); sslctx_cb) {
+    for (TlsContext& ctx : tls_contexts_) {
+      sslctx_cb(ctx.ssl_ctx_.get());
+    }
+  }
+
   // Add supported cipher suites from the TLS 1.3 spec:
   // https://tools.ietf.org/html/rfc8446#appendix-B.4
   // AES-CCM cipher suites are removed (no BoringSSL support).

source/extensions/transport_sockets/tls/ssl_handshaker.h

@@ -137,6 +137,11 @@ class HandshakerFactoryImpl : public Ssl::HandshakerFactory {
     return Ssl::HandshakerCapabilities{};
   }
 
+  Ssl::SslCtxCb sslctxCb(Ssl::HandshakerFactoryContext&) const override {
+    // The default handshaker impl doesn't additionally modify SSL_CTX.
+    return nullptr;
+  }
+
   static HandshakerFactory* getDefaultHandshakerFactory() {
     static HandshakerFactoryImpl default_handshaker_factory;
     return &default_handshaker_factory;

source/extensions/transport_sockets/tls/ssl_socket.h

@@ -71,6 +71,8 @@ class SslSocket : public Network::TransportSocket,
   void onFailure() override;
   Network::TransportSocketCallbacks* transportSocketCallbacks() override { return callbacks_; }
 
+  SSL* rawSslForTest() const { return rawSsl(); }
+
 protected:
   SSL* rawSsl() const { return info_->ssl_.get(); }
 

test/extensions/transport_sockets/tls/BUILD

@@ -183,6 +183,26 @@ envoy_cc_test(
     ],
 )
 
+envoy_cc_test(
+    name = "handshaker_factory_test",
+    srcs = ["handshaker_factory_test.cc"],
+    deps = [
+        "//source/common/stream_info:stream_info_lib",
+        "//source/extensions/transport_sockets/tls:context_config_lib",
+        "//source/extensions/transport_sockets/tls:context_lib",
+        "//source/extensions/transport_sockets/tls:ssl_handshaker_lib",
+        "//source/extensions/transport_sockets/tls:ssl_socket_lib",
+        "//source/server:process_context_lib",
+        "//test/mocks/buffer:buffer_mocks",
+        "//test/mocks/network:network_mocks",
+        "//test/mocks/runtime:runtime_mocks",
+        "//test/mocks/server:server_mocks",
+        "//test/mocks/ssl:ssl_mocks",
+        "//test/mocks/stats:stats_mocks",
+        "//test/test_common:registry_lib",
+    ],
+)
+
 envoy_cc_benchmark_binary(
     name = "tls_throughput_benchmark",
     srcs = ["tls_throughput_benchmark.cc"],

test/extensions/transport_sockets/tls/handshaker_factory_test.cc

@@ -0,0 +1,149 @@
+#include <openssl/ssl3.h>
+
+#include "envoy/network/transport_socket.h"
+#include "envoy/ssl/handshaker.h"
+
+#include "common/stream_info/stream_info_impl.h"
+
+#include "server/process_context_impl.h"
+
+#include "extensions/transport_sockets/tls/context_config_impl.h"
+#include "extensions/transport_sockets/tls/context_manager_impl.h"
+#include "extensions/transport_sockets/tls/ssl_handshaker.h"
+#include "extensions/transport_sockets/tls/ssl_socket.h"
+
+#include "test/mocks/network/connection.h"
+#include "test/mocks/server/transport_socket_factory_context.h"
+#include "test/test_common/registry.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "openssl/evp.h"
+#include "openssl/hmac.h"
+#include "openssl/ssl.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace TransportSockets {
+namespace Tls {
+namespace {
+
+// Test-only custom process object which accepts an `SslCtxCb` for in-test SSL_CTX
+// manipulation.
+class CustomProcessObjectForTest : public ProcessObject {
+public:
+  CustomProcessObjectForTest(Ssl::SslCtxCb cb) : cb_(cb) {}
+
+  Ssl::SslCtxCb getSslCtxCb() { return cb_; }
+
+  static CustomProcessObjectForTest* get(const ProcessContextOptRef& process_context_opt_ref) {
+    auto& process_context = process_context_opt_ref.value().get();
+    auto& process_object = dynamic_cast<CustomProcessObjectForTest&>(process_context.get());
+    return &process_object;
+  }
+
+private:
+  Ssl::SslCtxCb cb_;
+};
+
+// Example SslHandshakerFactoryImpl demonstrating special-case behavior; in this
+// case, using a process context to modify the SSL_CTX.
+class HandshakerFactoryImplForTest
+    : public Extensions::TransportSockets::Tls::HandshakerFactoryImpl {
+  std::string name() const override { return "envoy.testonly_handshaker"; }
+
+  Ssl::SslCtxCb sslctxCb(Ssl::HandshakerFactoryContext& handshaker_factory_context) const override {
+    // Get process object, cast to custom process object, and return custom
+    // callback.
+    return CustomProcessObjectForTest::get(handshaker_factory_context.api().processContext())
+        ->getSslCtxCb();
+  }
+};
+
+class HandshakerFactoryTest : public testing::Test {
+protected:
+  HandshakerFactoryTest()
+      : context_manager_(
+            std::make_unique<Extensions::TransportSockets::Tls::ContextManagerImpl>(time_system_)),
+        registered_factory_(handshaker_factory_) {
+    // UpstreamTlsContext proto expects to use the newly-registered handshaker.
+    envoy::config::core::v3::TypedExtensionConfig* custom_handshaker_ =
+        tls_context_.mutable_common_tls_context()->mutable_custom_handshaker();
+    custom_handshaker_->set_name("envoy.testonly_handshaker");
+  }
+
+  // Helper for downcasting a socket to a test socket so we can examine its
+  // SSL_CTX.
+  SSL_CTX* extractSslCtx(Network::TransportSocket* socket) {
+    SslSocket* ssl_socket = dynamic_cast<SslSocket*>(socket);
+    SSL* ssl = ssl_socket->rawSslForTest();
+    return SSL_get_SSL_CTX(ssl);
+  }
+
+  Event::GlobalTimeSystem time_system_;
+  Stats::IsolatedStoreImpl stats_store_;
+  std::unique_ptr<Extensions::TransportSockets::Tls::ContextManagerImpl> context_manager_;
+  HandshakerFactoryImplForTest handshaker_factory_;
+  Registry::InjectFactory<Ssl::HandshakerFactory> registered_factory_;
+  envoy::extensions::transport_sockets::tls::v3::UpstreamTlsContext tls_context_;
+};
+
+TEST_F(HandshakerFactoryTest, SetMockFunctionCb) {
+  testing::MockFunction<void(SSL_CTX*)> cb;
+  EXPECT_CALL(cb, Call);
+
+  CustomProcessObjectForTest custom_process_object_for_test(cb.AsStdFunction());
+  auto process_context_impl = std::make_unique<Envoy::ProcessContextImpl>(
+      static_cast<Envoy::ProcessObject&>(custom_process_object_for_test));
+
+  NiceMock<Server::Configuration::MockTransportSocketFactoryContext> mock_factory_ctx;
+  EXPECT_CALL(mock_factory_ctx.api_, processContext())
+      .WillRepeatedly(
+          testing::Return(std::reference_wrapper<Envoy::ProcessContext>(*process_context_impl)));
+
+  Extensions::TransportSockets::Tls::ClientSslSocketFactory socket_factory(
+      /*config=*/
+      std::make_unique<Extensions::TransportSockets::Tls::ClientContextConfigImpl>(
+          tls_context_, "", mock_factory_ctx),
+      *context_manager_, stats_store_);
+
+  std::unique_ptr<Network::TransportSocket> socket = socket_factory.createTransportSocket(nullptr);
+
+  SSL_CTX* ssl_ctx = extractSslCtx(socket.get());
+
+  // Compare to the next test, where our custom `sslctxcb` reaches in and sets
+  // this option.
+  EXPECT_FALSE(SSL_CTX_get_options(ssl_ctx) & SSL_OP_NO_TLSv1);
+}
+
+TEST_F(HandshakerFactoryTest, SetSpecificSslCtxOption) {
+  CustomProcessObjectForTest custom_process_object_for_test(
+      /*cb=*/[](SSL_CTX* ssl_ctx) { SSL_CTX_set_options(ssl_ctx, SSL_OP_NO_TLSv1); });
+  auto process_context_impl = std::make_unique<Envoy::ProcessContextImpl>(
+      static_cast<Envoy::ProcessObject&>(custom_process_object_for_test));
+
+  NiceMock<Server::Configuration::MockTransportSocketFactoryContext> mock_factory_ctx;
+  EXPECT_CALL(mock_factory_ctx.api_, processContext())
+      .WillRepeatedly(
+          testing::Return(std::reference_wrapper<Envoy::ProcessContext>(*process_context_impl)));
+
+  Extensions::TransportSockets::Tls::ClientSslSocketFactory socket_factory(
+      /*config=*/
+      std::make_unique<Extensions::TransportSockets::Tls::ClientContextConfigImpl>(
+          tls_context_, "", mock_factory_ctx),
+      *context_manager_, stats_store_);
+
+  std::unique_ptr<Network::TransportSocket> socket = socket_factory.createTransportSocket(nullptr);
+
+  SSL_CTX* ssl_ctx = extractSslCtx(socket.get());
+
+  // Compare to the previous test, where our mock `sslctxcb` is called, but does
+  // not set this option.
+  EXPECT_TRUE(SSL_CTX_get_options(ssl_ctx) & SSL_OP_NO_TLSv1);
+}
+
+} // namespace
+} // namespace Tls
+} // namespace TransportSockets
+} // namespace Extensions
+} // namespace Envoy

test/mocks/ssl/mocks.h

@@ -92,6 +92,7 @@ class MockClientContextConfig : public ClientContextConfig {
 
   MOCK_METHOD(Ssl::HandshakerFactoryCb, createHandshaker, (), (const, override));
   MOCK_METHOD(Ssl::HandshakerCapabilities, capabilities, (), (const, override));
+  MOCK_METHOD(Ssl::SslCtxCb, sslctxCb, (), (const, override));
 
   MOCK_METHOD(const std::string&, serverNameIndication, (), (const));
   MOCK_METHOD(bool, allowRenegotiation, (), (const));
@@ -118,6 +119,7 @@ class MockServerContextConfig : public ServerContextConfig {
 
   MOCK_METHOD(Ssl::HandshakerFactoryCb, createHandshaker, (), (const, override));
   MOCK_METHOD(Ssl::HandshakerCapabilities, capabilities, (), (const, override));
+  MOCK_METHOD(Ssl::SslCtxCb, sslctxCb, (), (const, override));
 
   MOCK_METHOD(bool, requireClientCertificate, (), (const));
   MOCK_METHOD(OcspStaplePolicy, ocspStaplePolicy, (), (const));