From 1374fac8de85fe1ac877096f18b60a1561dfc96f Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sat, 11 Apr 2020 15:58:01 +0200
Subject: Replace SSL_CTX_set_tlsext_servername_callback with
 SSL_client_hello_get0_ext

---
 https.cpp | 62 ++++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 48 insertions(+), 14 deletions(-)

(limited to 'https.cpp')

diff --git a/https.cpp b/https.cpp
index a263a54..5230d60 100644
--- a/https.cpp
+++ b/https.cpp
@@ -6,6 +6,7 @@
 #include "response.h"
 
 #include <openssl/ssl.h>
+#include <openssl/crypto.h>
 
 #include <boost/asio/buffer.hpp>
 #include <boost/beast/core.hpp>
@@ -566,25 +567,62 @@ void load_server_certificate(boost::asio::ssl::context& ctx, fs::path cert_path,
         boost::asio::buffer(dh.data(), dh.size()));
 }
 
+int ServerNameError(SSL *s, HTTPS::Server::ctx_type& ctx_map)
+{
+ std::shared_ptr<ssl::context> ctx{ctx_map.at("")};
+ SSL_set_SSL_CTX(s, ctx->native_handle());
+ return SSL_CLIENT_HELLO_SUCCESS; // OK for now
+}
+
 int servername_callback(SSL *s, int *al, void *arg)
 {
- int type {SSL_get_servername_type(s)};
- std::string server_name {SSL_get_servername(s, type)};
+ HTTPS::Server::ctx_type& ctx_map = *(HTTPS::Server::ctx_type*)arg;
+
+ if (0) { // not really necessary
+  int* numbers;
+  size_t numbers_size;
+  if (SSL_client_hello_get1_extensions_present(s, &numbers, &numbers_size) != 1) {
+   std::cout << "Error on SSL_client_hello_get1_extensions_present" << std::endl;
+   return ServerNameError(s, ctx_map);
+  }
+  bool server_name_available {false};
+  for (size_t i = 0; i < numbers_size; i++)
+   if (numbers[i] == 0)
+    server_name_available = true;
+
+  OPENSSL_free(numbers);
+
+  if (!server_name_available) {
+   std::cout << "Error: No server_name available at SSL_client_hello_get1_extensions_present" << std::endl;
+   return ServerNameError(s, ctx_map);
+  }
+ }
+
+ const unsigned char* data;
+ size_t data_size;
+ // 0 is server_name
+ if (SSL_client_hello_get0_ext(s, 0, &data, &data_size) != 1) {
+  std::cout << "Warning: Error on SSL_client_hello_get0_ext: servername not available. Using dummy ctx." << std::endl;
+  return ServerNameError(s, ctx_map);
+ }
 
- HTTPS::Server::ctx_type* ctx_map = (HTTPS::Server::ctx_type*)arg;
+ // SNI Server Name, See https://tools.ietf.org/html/rfc6066 (TODO: why are there 5 bytes header?)
+ std::string server_name {std::string((const char*)data, (size_t)data_size)};
+ if (server_name.size() >= 5 && server_name[0] == '\0')
+  server_name = server_name.substr(5);
 
- auto it {ctx_map->find(server_name)};
+ auto it {ctx_map.find(server_name)};
  std::shared_ptr<ssl::context> ctx{};
- if (it != ctx_map->end()) {
+ if (it != ctx_map.end()) {
   ctx = it->second;
  } else {
-  std::cout << "Warning: server_name " << server_name << " not found in list of prepared contexts. Using dummy ctx." << std::endl;
-  ctx = ctx_map->at("");
+  std::cout << "Warning: server_name " << server_name << " (" << server_name.size() << ") not found in list of prepared contexts. Using dummy ctx." << std::endl;
+  return ServerNameError(s, ctx_map);
  }
 
  SSL_set_SSL_CTX(s, ctx->native_handle());
  
- return SSL_TLSEXT_ERR_OK;
+ return SSL_CLIENT_HELLO_SUCCESS;
 }
 
 } // anonymous namespace
@@ -598,9 +636,7 @@ Server::Server(Config& config, boost::asio::io_context& ioc, const Socket& socke
  // initial dummy, before we can add specific ctx w/ certificate
  std::shared_ptr<ssl::context> ctx_dummy{std::make_shared<ssl::context>(tls_method)};
  load_server_certificate(*ctx_dummy, "", "");
- //SSL_CTX_set_client_hello_cb(ctx_dummy->native_handle(), servername_callback, &m_ctx);
- SSL_CTX_set_tlsext_servername_callback(ctx_dummy->native_handle(), servername_callback);
- SSL_CTX_set_tlsext_servername_arg(ctx_dummy->native_handle(), &m_ctx);
+ SSL_CTX_set_client_hello_cb(ctx_dummy->native_handle(), servername_callback, &m_ctx);
  m_ctx.emplace("", ctx_dummy);
 
  // import the real certificates
@@ -612,9 +648,7 @@ Server::Server(Config& config, boost::asio::io_context& ioc, const Socket& socke
     std::cout << "Creating SSL context/cert for site " << serve_site << " on port " << socket.port << std::endl;
 
     load_server_certificate(*ctx, site.cert_path, site.key_path);
-    //SSL_CTX_set_client_hello_cb(ctx->native_handle(), servername_callback, &m_ctx);
-    SSL_CTX_set_tlsext_servername_callback(ctx->native_handle(), servername_callback);
-    SSL_CTX_set_tlsext_servername_arg(ctx->native_handle(), &m_ctx);
+    SSL_CTX_set_client_hello_cb(ctx->native_handle(), servername_callback, &m_ctx);
 
     for (const auto& host: site.hosts) {
      std::cout << "  Adding Host " << host << std::endl;
-- 
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