nghttpx: Support ECDHE and DHE cipher suites

Use --dh-param-file option to specify a file including DH parameters
in PEM format.

For example, you can create DH parameters with 1024 bit key using
following command:

$ openssl dhparam -outform PEM -out dhparam.pem 1024

src/shrpx.cc

@@ -529,6 +529,10 @@ void print_help(std::ostream& out)
       << "                       Explicitly set the content of the TLS SNI\n"
       << "                       extension.  This will default to the backend\n"
       << "                       HOST name.\n"
+      << "    --dh-param-file=<PATH>\n"
+      << "                       Path to file that contains DH parameters in\n"
+      << "                       PEM format. Without this option, DHE cipher\n"
+      << "                       suites are not available."
       << "\n"
       << "  HTTP/2.0 and SPDY:\n"
       << "    -c, --spdy-max-concurrent-streams=<NUM>\n"
@@ -660,6 +664,7 @@ int main(int argc, char **argv)
       {"frontend-no-tls", no_argument, &flag, 29},
       {"backend-tls-sni-field", required_argument, &flag, 31},
       {"honor-cipher-order", no_argument, &flag, 32},
+      {"dh-param-file", required_argument, &flag, 33},
       {nullptr, 0, nullptr, 0 }
     };
     int option_index = 0;
@@ -839,7 +844,10 @@ int main(int argc, char **argv)
         cmdcfgs.push_back(std::make_pair(SHRPX_OPT_HONOR_CIPHER_ORDER,
                                          "yes"));
         break;
-
+      case 33:
+        // --dh-param-file
+        cmdcfgs.push_back(std::make_pair(SHRPX_OPT_DH_PARAM_FILE, optarg));
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -53,6 +53,7 @@ namespace shrpx {
 const char SHRPX_OPT_PRIVATE_KEY_FILE[] = "private-key-file";
 const char SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE[] = "private-key-passwd-file";
 const char SHRPX_OPT_CERTIFICATE_FILE[] = "certificate-file";
+const char SHRPX_OPT_DH_PARAM_FILE[] = "dh-param-file";
 const char SHRPX_OPT_SUBCERT[] = "subcert";
 
 const char SHRPX_OPT_BACKEND[] = "backend";
@@ -296,6 +297,8 @@ int parse_config(const char *opt, const char *optarg)
     set_config_str(&mod_config()->private_key_passwd, passwd.c_str());
   } else if(util::strieq(opt, SHRPX_OPT_CERTIFICATE_FILE)) {
     set_config_str(&mod_config()->cert_file, optarg);
+  } else if(util::strieq(opt, SHRPX_OPT_DH_PARAM_FILE)) {
+    set_config_str(&mod_config()->dh_param_file, optarg);
   } else if(util::strieq(opt, SHRPX_OPT_SUBCERT)) {
     // Private Key file and certificate file separated by ':'.
     const char *sp = strchr(optarg, ':');

src/shrpx_config.h

@@ -47,6 +47,7 @@ struct CertLookupTree;
 extern const char SHRPX_OPT_PRIVATE_KEY_FILE[];
 extern const char SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE[];
 extern const char SHRPX_OPT_CERTIFICATE_FILE[];
+extern const char SHRPX_OPT_DH_PARAM_FILE[];
 extern const char SHRPX_OPT_SUBCERT[];
 extern const char SHRPX_OPT_BACKEND[];
 extern const char SHRPX_OPT_FRONTEND[];
@@ -105,6 +106,7 @@ struct Config {
   char *private_key_file;
   char *private_key_passwd;
   char *cert_file;
+  char *dh_param_file;
   SSL_CTX *default_ssl_ctx;
   ssl::CertLookupTree *cert_tree;
   bool verify_client;

src/shrpx_ssl.cc

@@ -138,7 +138,9 @@ SSL_CTX* create_ssl_context(const char *private_key_file,
   }
   SSL_CTX_set_options(ssl_ctx,
                       SSL_OP_ALL | SSL_OP_NO_SSLv2 | SSL_OP_NO_COMPRESSION |
-                      SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION);
+                      SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION |
+                      SSL_OP_SINGLE_ECDH_USE | SSL_OP_SINGLE_DH_USE |
+                      SSL_OP_NO_TICKET);
 
   const unsigned char sid_ctx[] = "shrpx";
   SSL_CTX_set_session_id_context(ssl_ctx, sid_ctx, sizeof(sid_ctx)-1);
@@ -155,6 +157,36 @@ SSL_CTX* create_ssl_context(const char *private_key_file,
     }
   }
 
+  // Use P-256, which is sufficiently secure at the time of this
+  // writing.
+  auto ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
+  if(ecdh == nullptr) {
+    LOG(FATAL) << "EC_KEY_new_by_curv_name failed: "
+               << ERR_error_string(ERR_get_error(), nullptr);
+    DIE();
+  }
+  SSL_CTX_set_tmp_ecdh(ssl_ctx, ecdh);
+  EC_KEY_free(ecdh);
+
+  if(get_config()->dh_param_file) {
+    // Read DH parameters from file
+    auto bio = BIO_new_file(get_config()->dh_param_file, "r");
+    if(bio == nullptr) {
+      LOG(FATAL) << "BIO_new_file() failed: "
+                 << ERR_error_string(ERR_get_error(), nullptr);
+      DIE();
+    }
+    auto dh = PEM_read_bio_DHparams(bio, nullptr, nullptr, nullptr);
+    if(dh == nullptr) {
+      LOG(FATAL) << "PEM_read_bio_DHparams() failed: "
+                 << ERR_error_string(ERR_get_error(), nullptr);
+      DIE();
+    }
+    SSL_CTX_set_tmp_dh(ssl_ctx, dh);
+    DH_free(dh);
+    BIO_free(bio);
+  }
+
   SSL_CTX_set_mode(ssl_ctx, SSL_MODE_ENABLE_PARTIAL_WRITE);
   SSL_CTX_set_mode(ssl_ctx, SSL_MODE_AUTO_RETRY);
   SSL_CTX_set_mode(ssl_ctx, SSL_MODE_RELEASE_BUFFERS);