xref: /openbmc/bmcweb/http/http_connection.hpp (revision f165deef) 
1 #pragma once
2 #include "bmcweb_config.h"
3 
4 #include "authentication.hpp"
5 #include "http_response.hpp"
6 #include "http_utility.hpp"
7 #include "logging.hpp"
8 #include "utility.hpp"
9 
10 #include <boost/algorithm/string/predicate.hpp>
11 #include <boost/asio/io_context.hpp>
12 #include <boost/asio/ip/tcp.hpp>
13 #include <boost/asio/ssl/stream.hpp>
14 #include <boost/asio/steady_timer.hpp>
15 #include <boost/beast/core/flat_static_buffer.hpp>
16 #include <boost/beast/http/parser.hpp>
17 #include <boost/beast/http/read.hpp>
18 #include <boost/beast/http/serializer.hpp>
19 #include <boost/beast/http/write.hpp>
20 #include <boost/beast/ssl/ssl_stream.hpp>
21 #include <boost/beast/websocket.hpp>
22 #include <boost/url/url_view.hpp>
23 #include <json_html_serializer.hpp>
24 #include <security_headers.hpp>
25 #include <ssl_key_handler.hpp>
26 
27 #include <atomic>
28 #include <chrono>
29 #include <vector>
30 
31 namespace crow
32 {
33 
34 inline void prettyPrintJson(crow::Response& res)
35 {
36     json_html_util::dumpHtml(res.body(), res.jsonValue);
37 
38     res.addHeader(boost::beast::http::field::content_type,
39                   "text/html;charset=UTF-8");
40 }
41 
42 static int connectionCount = 0;
43 
44 // request body limit size set by the bmcwebHttpReqBodyLimitMb option
45 constexpr uint64_t httpReqBodyLimit =
46     1024UL * 1024UL * bmcwebHttpReqBodyLimitMb;
47 
48 constexpr uint64_t loggedOutPostBodyLimit = 4096;
49 
50 constexpr uint32_t httpHeaderLimit = 8192;
51 
52 template <typename Adaptor, typename Handler>
53 class Connection :
54     public std::enable_shared_from_this<Connection<Adaptor, Handler>>
55 {
56   public:
57     Connection(Handler* handlerIn, boost::asio::steady_timer&& timerIn,
58                std::function<std::string()>& getCachedDateStrF,
59                Adaptor adaptorIn) :
60         adaptor(std::move(adaptorIn)),
61         handler(handlerIn), timer(std::move(timerIn)),
62         getCachedDateStr(getCachedDateStrF)
63     {
64         parser.emplace(std::piecewise_construct, std::make_tuple());
65         parser->body_limit(httpReqBodyLimit);
66         parser->header_limit(httpHeaderLimit);
67 
68 #ifdef BMCWEB_ENABLE_MUTUAL_TLS_AUTHENTICATION
69         prepareMutualTls();
70 #endif // BMCWEB_ENABLE_MUTUAL_TLS_AUTHENTICATION
71 
72         connectionCount++;
73 
74         BMCWEB_LOG_DEBUG << this << " Connection open, total "
75                          << connectionCount;
76     }
77 
78     ~Connection()
79     {
80         res.setCompleteRequestHandler(nullptr);
81         cancelDeadlineTimer();
82 
83         connectionCount--;
84         BMCWEB_LOG_DEBUG << this << " Connection closed, total "
85                          << connectionCount;
86     }
87 
88     Connection(const Connection&) = delete;
89     Connection(Connection&&) = delete;
90     Connection& operator=(const Connection&) = delete;
91     Connection& operator=(Connection&&) = delete;
92 
93     void prepareMutualTls()
94     {
95         std::error_code error;
96         std::filesystem::path caPath(ensuressl::trustStorePath);
97         auto caAvailable = !std::filesystem::is_empty(caPath, error);
98         caAvailable = caAvailable && !error;
99         if (caAvailable && persistent_data::SessionStore::getInstance()
100                                .getAuthMethodsConfig()
101                                .tls)
102         {
103             adaptor.set_verify_mode(boost::asio::ssl::verify_peer);
104             std::string id = "bmcweb";
105 
106             const char* cStr = id.c_str();
107             // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
108             const auto* idC = reinterpret_cast<const unsigned char*>(cStr);
109             int ret = SSL_set_session_id_context(
110                 adaptor.native_handle(), idC,
111                 static_cast<unsigned int>(id.length()));
112             if (ret == 0)
113             {
114                 BMCWEB_LOG_ERROR << this << " failed to set SSL id";
115             }
116         }
117 
118         adaptor.set_verify_callback(
119             [this](bool preverified, boost::asio::ssl::verify_context& ctx) {
120             // do nothing if TLS is disabled
121             if (!persistent_data::SessionStore::getInstance()
122                      .getAuthMethodsConfig()
123                      .tls)
124             {
125                 BMCWEB_LOG_DEBUG << this << " TLS auth_config is disabled";
126                 return true;
127             }
128 
129             // We always return true to allow full auth flow
130             if (!preverified)
131             {
132                 BMCWEB_LOG_DEBUG << this << " TLS preverification failed.";
133                 return true;
134             }
135 
136             X509_STORE_CTX* cts = ctx.native_handle();
137             if (cts == nullptr)
138             {
139                 BMCWEB_LOG_DEBUG << this << " Cannot get native TLS handle.";
140                 return true;
141             }
142 
143             // Get certificate
144             X509* peerCert =
145                 X509_STORE_CTX_get_current_cert(ctx.native_handle());
146             if (peerCert == nullptr)
147             {
148                 BMCWEB_LOG_DEBUG << this
149                                  << " Cannot get current TLS certificate.";
150                 return true;
151             }
152 
153             // Check if certificate is OK
154             int ctxError = X509_STORE_CTX_get_error(cts);
155             if (ctxError != X509_V_OK)
156             {
157                 BMCWEB_LOG_INFO << this << " Last TLS error is: " << ctxError;
158                 return true;
159             }
160             // Check that we have reached final certificate in chain
161             int32_t depth = X509_STORE_CTX_get_error_depth(cts);
162             if (depth != 0)
163 
164             {
165                 BMCWEB_LOG_DEBUG
166                     << this << " Certificate verification in progress (depth "
167                     << depth << "), waiting to reach final depth";
168                 return true;
169             }
170 
171             BMCWEB_LOG_DEBUG << this
172                              << " Certificate verification of final depth";
173 
174             // Verify KeyUsage
175             bool isKeyUsageDigitalSignature = false;
176             bool isKeyUsageKeyAgreement = false;
177 
178             ASN1_BIT_STRING* usage = static_cast<ASN1_BIT_STRING*>(
179                 X509_get_ext_d2i(peerCert, NID_key_usage, nullptr, nullptr));
180 
181             if (usage == nullptr)
182             {
183                 BMCWEB_LOG_DEBUG << this << " TLS usage is null";
184                 return true;
185             }
186 
187             for (int i = 0; i < usage->length; i++)
188             {
189                 // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
190                 unsigned char usageChar = usage->data[i];
191                 if (KU_DIGITAL_SIGNATURE & usageChar)
192                 {
193                     isKeyUsageDigitalSignature = true;
194                 }
195                 if (KU_KEY_AGREEMENT & usageChar)
196                 {
197                     isKeyUsageKeyAgreement = true;
198                 }
199             }
200             ASN1_BIT_STRING_free(usage);
201 
202             if (!isKeyUsageDigitalSignature || !isKeyUsageKeyAgreement)
203             {
204                 BMCWEB_LOG_DEBUG << this
205                                  << " Certificate ExtendedKeyUsage does "
206                                     "not allow provided certificate to "
207                                     "be used for user authentication";
208                 return true;
209             }
210 
211             // Determine that ExtendedKeyUsage includes Client Auth
212 
213             stack_st_ASN1_OBJECT* extUsage =
214                 static_cast<stack_st_ASN1_OBJECT*>(X509_get_ext_d2i(
215                     peerCert, NID_ext_key_usage, nullptr, nullptr));
216 
217             if (extUsage == nullptr)
218             {
219                 BMCWEB_LOG_DEBUG << this << " TLS extUsage is null";
220                 return true;
221             }
222 
223             bool isExKeyUsageClientAuth = false;
224             for (int i = 0; i < sk_ASN1_OBJECT_num(extUsage); i++)
225             {
226                 // NOLINTNEXTLINE(cppcoreguidelines-pro-type-cstyle-cast)
227                 int nid = OBJ_obj2nid(sk_ASN1_OBJECT_value(extUsage, i));
228                 if (NID_client_auth == nid)
229                 {
230                     isExKeyUsageClientAuth = true;
231                     break;
232                 }
233             }
234             sk_ASN1_OBJECT_free(extUsage);
235 
236             // Certificate has to have proper key usages set
237             if (!isExKeyUsageClientAuth)
238             {
239                 BMCWEB_LOG_DEBUG << this
240                                  << " Certificate ExtendedKeyUsage does "
241                                     "not allow provided certificate to "
242                                     "be used for user authentication";
243                 return true;
244             }
245             std::string sslUser;
246             // Extract username contained in CommonName
247             sslUser.resize(256, '\0');
248 
249             int status = X509_NAME_get_text_by_NID(
250                 X509_get_subject_name(peerCert), NID_commonName, sslUser.data(),
251                 static_cast<int>(sslUser.size()));
252 
253             if (status == -1)
254             {
255                 BMCWEB_LOG_DEBUG
256                     << this << " TLS cannot get username to create session";
257                 return true;
258             }
259 
260             size_t lastChar = sslUser.find('\0');
261             if (lastChar == std::string::npos || lastChar == 0)
262             {
263                 BMCWEB_LOG_DEBUG << this << " Invalid TLS user name";
264                 return true;
265             }
266             sslUser.resize(lastChar);
267             sessionIsFromTransport = true;
268             userSession = persistent_data::SessionStore::getInstance()
269                               .generateUserSession(
270                                   sslUser, req->ipAddress, std::nullopt,
271                                   persistent_data::PersistenceType::TIMEOUT);
272             if (userSession != nullptr)
273             {
274                 BMCWEB_LOG_DEBUG
275                     << this
276                     << " Generating TLS session: " << userSession->uniqueId;
277             }
278             return true;
279         });
280     }
281 
282     Adaptor& socket()
283     {
284         return adaptor;
285     }
286 
287     void start()
288     {
289         if (connectionCount >= 100)
290         {
291             BMCWEB_LOG_CRITICAL << this << "Max connection count exceeded.";
292             return;
293         }
294 
295         startDeadline();
296 
297         // TODO(ed) Abstract this to a more clever class with the idea of an
298         // asynchronous "start"
299         if constexpr (std::is_same_v<Adaptor,
300                                      boost::beast::ssl_stream<
301                                          boost::asio::ip::tcp::socket>>)
302         {
303             adaptor.async_handshake(boost::asio::ssl::stream_base::server,
304                                     [this, self(shared_from_this())](
305                                         const boost::system::error_code& ec) {
306                 if (ec)
307                 {
308                     return;
309                 }
310                 doReadHeaders();
311             });
312         }
313         else
314         {
315             doReadHeaders();
316         }
317     }
318 
319     void handle()
320     {
321         std::error_code reqEc;
322         crow::Request& thisReq = req.emplace(parser->release(), reqEc);
323         if (reqEc)
324         {
325             BMCWEB_LOG_DEBUG << "Request failed to construct" << reqEc;
326             return;
327         }
328         thisReq.session = userSession;
329 
330         // Fetch the client IP address
331         readClientIp();
332 
333         // Check for HTTP version 1.1.
334         if (thisReq.version() == 11)
335         {
336             if (thisReq.getHeaderValue(boost::beast::http::field::host).empty())
337             {
338                 res.result(boost::beast::http::status::bad_request);
339                 completeRequest(res);
340                 return;
341             }
342         }
343 
344         BMCWEB_LOG_INFO << "Request: "
345                         << " " << this << " HTTP/" << thisReq.version() / 10
346                         << "." << thisReq.version() % 10 << ' '
347                         << thisReq.methodString() << " " << thisReq.target()
348                         << " " << thisReq.ipAddress.to_string();
349 
350         res.isAliveHelper = [this]() -> bool { return isAlive(); };
351 
352         thisReq.ioService = static_cast<decltype(thisReq.ioService)>(
353             &adaptor.get_executor().context());
354 
355         if (res.completed)
356         {
357             completeRequest(res);
358             return;
359         }
360 #ifndef BMCWEB_INSECURE_DISABLE_AUTHX
361         if (!crow::authentication::isOnAllowlist(req->url, req->method()) &&
362             thisReq.session == nullptr)
363         {
364             BMCWEB_LOG_WARNING << "Authentication failed";
365             forward_unauthorized::sendUnauthorized(
366                 req->url, req->getHeaderValue("X-Requested-With"),
367                 req->getHeaderValue("Accept"), res);
368             completeRequest(res);
369             return;
370         }
371 #endif // BMCWEB_INSECURE_DISABLE_AUTHX
372         auto asyncResp = std::make_shared<bmcweb::AsyncResp>();
373         BMCWEB_LOG_DEBUG << "Setting completion handler";
374         asyncResp->res.setCompleteRequestHandler(
375             [self(shared_from_this())](crow::Response& thisRes) {
376             self->completeRequest(thisRes);
377         });
378 
379         if (thisReq.isUpgrade() &&
380             boost::iequals(
381                 thisReq.getHeaderValue(boost::beast::http::field::upgrade),
382                 "websocket"))
383         {
384             handler->handleUpgrade(thisReq, res, std::move(adaptor));
385             // delete lambda with self shared_ptr
386             // to enable connection destruction
387             asyncResp->res.setCompleteRequestHandler(nullptr);
388             return;
389         }
390         handler->handle(thisReq, asyncResp);
391     }
392 
393     bool isAlive()
394     {
395         if constexpr (std::is_same_v<Adaptor,
396                                      boost::beast::ssl_stream<
397                                          boost::asio::ip::tcp::socket>>)
398         {
399             return adaptor.next_layer().is_open();
400         }
401         else
402         {
403             return adaptor.is_open();
404         }
405     }
406     void close()
407     {
408         if constexpr (std::is_same_v<Adaptor,
409                                      boost::beast::ssl_stream<
410                                          boost::asio::ip::tcp::socket>>)
411         {
412             adaptor.next_layer().close();
413             if (sessionIsFromTransport && userSession != nullptr)
414             {
415                 BMCWEB_LOG_DEBUG
416                     << this
417                     << " Removing TLS session: " << userSession->uniqueId;
418                 persistent_data::SessionStore::getInstance().removeSession(
419                     userSession);
420             }
421         }
422         else
423         {
424             adaptor.close();
425         }
426     }
427 
428     void completeRequest(crow::Response& thisRes)
429     {
430         if (!req)
431         {
432             return;
433         }
434         res = std::move(thisRes);
435         BMCWEB_LOG_INFO << "Response: " << this << ' ' << req->url << ' '
436                         << res.resultInt() << " keepalive=" << req->keepAlive();
437 
438         addSecurityHeaders(*req, res);
439 
440         crow::authentication::cleanupTempSession(*req);
441 
442         if (!isAlive())
443         {
444             // BMCWEB_LOG_DEBUG << this << " delete (socket is closed) " <<
445             // isReading
446             // << ' ' << isWriting;
447             // delete this;
448 
449             // delete lambda with self shared_ptr
450             // to enable connection destruction
451             res.setCompleteRequestHandler(nullptr);
452             return;
453         }
454         if (res.body().empty() && !res.jsonValue.empty())
455         {
456             using http_helpers::ContentType;
457             std::array<ContentType, 2> allowed{ContentType::JSON,
458                                                ContentType::HTML};
459             ContentType prefered =
460                 getPreferedContentType(req->getHeaderValue("Accept"), allowed);
461 
462             if (prefered == ContentType::HTML)
463             {
464                 prettyPrintJson(res);
465             }
466             else
467             {
468                 // Technically prefered could also be NoMatch here, but we'd
469                 // like to default to something rather than return 400 for
470                 // backward compatibility.
471                 res.addHeader(boost::beast::http::field::content_type,
472                               "application/json");
473                 res.body() = res.jsonValue.dump(
474                     2, ' ', true, nlohmann::json::error_handler_t::replace);
475             }
476         }
477 
478         if (res.resultInt() >= 400 && res.body().empty())
479         {
480             res.body() = std::string(res.reason());
481         }
482 
483         if (res.result() == boost::beast::http::status::no_content)
484         {
485             // Boost beast throws if content is provided on a no-content
486             // response.  Ideally, this would never happen, but in the case that
487             // it does, we don't want to throw.
488             BMCWEB_LOG_CRITICAL
489                 << this << " Response content provided but code was no-content";
490             res.body().clear();
491         }
492 
493         res.addHeader(boost::beast::http::field::date, getCachedDateStr());
494 
495         res.keepAlive(req->keepAlive());
496 
497         doWrite(res);
498 
499         // delete lambda with self shared_ptr
500         // to enable connection destruction
501         res.setCompleteRequestHandler(nullptr);
502     }
503 
504     void readClientIp()
505     {
506         boost::asio::ip::address ip;
507         boost::system::error_code ec = getClientIp(ip);
508         if (ec)
509         {
510             return;
511         }
512         req->ipAddress = ip;
513     }
514 
515     boost::system::error_code getClientIp(boost::asio::ip::address& ip)
516     {
517         boost::system::error_code ec;
518         BMCWEB_LOG_DEBUG << "Fetch the client IP address";
519         boost::asio::ip::tcp::endpoint endpoint =
520             boost::beast::get_lowest_layer(adaptor).remote_endpoint(ec);
521 
522         if (ec)
523         {
524             // If remote endpoint fails keep going. "ClientOriginIPAddress"
525             // will be empty.
526             BMCWEB_LOG_ERROR << "Failed to get the client's IP Address. ec : "
527                              << ec;
528             return ec;
529         }
530         ip = endpoint.address();
531         return ec;
532     }
533 
534   private:
535     void doReadHeaders()
536     {
537         BMCWEB_LOG_DEBUG << this << " doReadHeaders";
538 
539         // Clean up any previous Connection.
540         boost::beast::http::async_read_header(
541             adaptor, buffer, *parser,
542             [this,
543              self(shared_from_this())](const boost::system::error_code& ec,
544                                        std::size_t bytesTransferred) {
545             BMCWEB_LOG_DEBUG << this << " async_read_header "
546                              << bytesTransferred << " Bytes";
547             bool errorWhileReading = false;
548             if (ec)
549             {
550                 errorWhileReading = true;
551                 if (ec == boost::asio::error::eof)
552                 {
553                     BMCWEB_LOG_WARNING
554                         << this << " Error while reading: " << ec.message();
555                 }
556                 else
557                 {
558                     BMCWEB_LOG_ERROR
559                         << this << " Error while reading: " << ec.message();
560                 }
561             }
562             else
563             {
564                 // if the adaptor isn't open anymore, and wasn't handed to a
565                 // websocket, treat as an error
566                 if (!isAlive() &&
567                     !boost::beast::websocket::is_upgrade(parser->get()))
568                 {
569                     errorWhileReading = true;
570                 }
571             }
572 
573             cancelDeadlineTimer();
574 
575             if (errorWhileReading)
576             {
577                 close();
578                 BMCWEB_LOG_DEBUG << this << " from read(1)";
579                 return;
580             }
581 
582             readClientIp();
583 
584             boost::asio::ip::address ip;
585             if (getClientIp(ip))
586             {
587                 BMCWEB_LOG_DEBUG << "Unable to get client IP";
588             }
589             sessionIsFromTransport = false;
590 #ifndef BMCWEB_INSECURE_DISABLE_AUTHX
591             boost::beast::http::verb method = parser->get().method();
592             userSession = crow::authentication::authenticate(
593                 ip, res, method, parser->get().base(), userSession);
594 
595             bool loggedIn = userSession != nullptr;
596             if (!loggedIn)
597             {
598                 const boost::optional<uint64_t> contentLength =
599                     parser->content_length();
600                 if (contentLength && *contentLength > loggedOutPostBodyLimit)
601                 {
602                     BMCWEB_LOG_DEBUG << "Content length greater than limit "
603                                      << *contentLength;
604                     close();
605                     return;
606                 }
607 
608                 BMCWEB_LOG_DEBUG << "Starting quick deadline";
609             }
610 #endif // BMCWEB_INSECURE_DISABLE_AUTHX
611 
612             doRead();
613             });
614     }
615 
616     void doRead()
617     {
618         BMCWEB_LOG_DEBUG << this << " doRead";
619         startDeadline();
620         boost::beast::http::async_read(adaptor, buffer, *parser,
621                                        [this, self(shared_from_this())](
622                                            const boost::system::error_code& ec,
623                                            std::size_t bytesTransferred) {
624             BMCWEB_LOG_DEBUG << this << " async_read " << bytesTransferred
625                              << " Bytes";
626             cancelDeadlineTimer();
627             if (ec)
628             {
629                 BMCWEB_LOG_ERROR << this
630                                  << " Error while reading: " << ec.message();
631                 close();
632                 BMCWEB_LOG_DEBUG << this << " from read(1)";
633                 return;
634             }
635             handle();
636         });
637     }
638 
639     void doWrite(crow::Response& thisRes)
640     {
641         BMCWEB_LOG_DEBUG << this << " doWrite";
642         thisRes.preparePayload();
643         serializer.emplace(*thisRes.stringResponse);
644         startDeadline();
645         boost::beast::http::async_write(adaptor, *serializer,
646                                         [this, self(shared_from_this())](
647                                             const boost::system::error_code& ec,
648                                             std::size_t bytesTransferred) {
649             BMCWEB_LOG_DEBUG << this << " async_write " << bytesTransferred
650                              << " bytes";
651 
652             cancelDeadlineTimer();
653 
654             if (ec)
655             {
656                 BMCWEB_LOG_DEBUG << this << " from write(2)";
657                 return;
658             }
659             if (!res.keepAlive())
660             {
661                 close();
662                 BMCWEB_LOG_DEBUG << this << " from write(1)";
663                 return;
664             }
665 
666             serializer.reset();
667             BMCWEB_LOG_DEBUG << this << " Clearing response";
668             res.clear();
669             parser.emplace(std::piecewise_construct, std::make_tuple());
670             parser->body_limit(httpReqBodyLimit); // reset body limit for
671                                                   // newly created parser
672             buffer.consume(buffer.size());
673 
674             // If the session was built from the transport, we don't need to
675             // clear it.  All other sessions are generated per request.
676             if (!sessionIsFromTransport)
677             {
678                 userSession = nullptr;
679             }
680 
681             // Destroy the Request via the std::optional
682             req.reset();
683             doReadHeaders();
684         });
685     }
686 
687     void cancelDeadlineTimer()
688     {
689         timer.cancel();
690     }
691 
692     void startDeadline()
693     {
694         cancelDeadlineTimer();
695 
696         std::chrono::seconds timeout(15);
697         // allow slow uploads for logged in users
698         bool loggedIn = userSession != nullptr;
699         if (loggedIn)
700         {
701             timeout = std::chrono::seconds(60);
702             return;
703         }
704 
705         std::weak_ptr<Connection<Adaptor, Handler>> weakSelf = weak_from_this();
706         timer.expires_after(timeout);
707         timer.async_wait([weakSelf](const boost::system::error_code ec) {
708             // Note, we are ignoring other types of errors here;  If the timer
709             // failed for any reason, we should still close the connection
710 
711             std::shared_ptr<Connection<Adaptor, Handler>> self =
712                 weakSelf.lock();
713             if (!self)
714             {
715                 BMCWEB_LOG_CRITICAL << self << " Failed to capture connection";
716                 return;
717             }
718             if (ec == boost::asio::error::operation_aborted)
719             {
720                 // Canceled wait means the path succeeeded.
721                 return;
722             }
723             if (ec)
724             {
725                 BMCWEB_LOG_CRITICAL << self << " timer failed " << ec;
726             }
727 
728             BMCWEB_LOG_WARNING << self << "Connection timed out, closing";
729 
730             self->close();
731         });
732 
733         BMCWEB_LOG_DEBUG << this << " timer started";
734     }
735 
736     Adaptor adaptor;
737     Handler* handler;
738     // Making this a std::optional allows it to be efficiently destroyed and
739     // re-created on Connection reset
740     std::optional<
741         boost::beast::http::request_parser<boost::beast::http::string_body>>
742         parser;
743 
744     boost::beast::flat_static_buffer<8192> buffer;
745 
746     std::optional<boost::beast::http::response_serializer<
747         boost::beast::http::string_body>>
748         serializer;
749 
750     std::optional<crow::Request> req;
751     crow::Response res;
752 
753     bool sessionIsFromTransport = false;
754     std::shared_ptr<persistent_data::UserSession> userSession;
755 
756     boost::asio::steady_timer timer;
757 
758     std::function<std::string()>& getCachedDateStr;
759 
760     using std::enable_shared_from_this<
761         Connection<Adaptor, Handler>>::shared_from_this;
762 
763     using std::enable_shared_from_this<
764         Connection<Adaptor, Handler>>::weak_from_this;
765 };
766 } // namespace crow
767