xref: /openbmc/bmcweb/http/http_connection.hpp (revision 74ab83c5) 
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             std::string unsupportedClientId;
268             sessionIsFromTransport = true;
269             userSession = persistent_data::SessionStore::getInstance()
270                               .generateUserSession(
271                                   sslUser, req->ipAddress, unsupportedClientId,
272                                   persistent_data::PersistenceType::TIMEOUT);
273             if (userSession != nullptr)
274             {
275                 BMCWEB_LOG_DEBUG
276                     << this
277                     << " Generating TLS session: " << userSession->uniqueId;
278             }
279             return true;
280         });
281     }
282 
283     Adaptor& socket()
284     {
285         return adaptor;
286     }
287 
288     void start()
289     {
290         if (connectionCount >= 100)
291         {
292             BMCWEB_LOG_CRITICAL << this << "Max connection count exceeded.";
293             return;
294         }
295 
296         startDeadline();
297 
298         // TODO(ed) Abstract this to a more clever class with the idea of an
299         // asynchronous "start"
300         if constexpr (std::is_same_v<Adaptor,
301                                      boost::beast::ssl_stream<
302                                          boost::asio::ip::tcp::socket>>)
303         {
304             adaptor.async_handshake(boost::asio::ssl::stream_base::server,
305                                     [this, self(shared_from_this())](
306                                         const boost::system::error_code& ec) {
307                 if (ec)
308                 {
309                     return;
310                 }
311                 doReadHeaders();
312             });
313         }
314         else
315         {
316             doReadHeaders();
317         }
318     }
319 
320     void handle()
321     {
322         std::error_code reqEc;
323         crow::Request& thisReq = req.emplace(parser->release(), reqEc);
324         if (reqEc)
325         {
326             BMCWEB_LOG_DEBUG << "Request failed to construct" << reqEc;
327             return;
328         }
329         thisReq.session = userSession;
330 
331         // Fetch the client IP address
332         readClientIp();
333 
334         // Check for HTTP version 1.1.
335         if (thisReq.version() == 11)
336         {
337             if (thisReq.getHeaderValue(boost::beast::http::field::host).empty())
338             {
339                 res.result(boost::beast::http::status::bad_request);
340                 completeRequest(res);
341                 return;
342             }
343         }
344 
345         BMCWEB_LOG_INFO << "Request: "
346                         << " " << this << " HTTP/" << thisReq.version() / 10
347                         << "." << thisReq.version() % 10 << ' '
348                         << thisReq.methodString() << " " << thisReq.target()
349                         << " " << thisReq.ipAddress.to_string();
350 
351         res.isAliveHelper = [this]() -> bool { return isAlive(); };
352 
353         thisReq.ioService = static_cast<decltype(thisReq.ioService)>(
354             &adaptor.get_executor().context());
355 
356         if (res.completed)
357         {
358             completeRequest(res);
359             return;
360         }
361 #ifndef BMCWEB_INSECURE_DISABLE_AUTHX
362         if (!crow::authentication::isOnAllowlist(req->url, req->method()) &&
363             thisReq.session == nullptr)
364         {
365             BMCWEB_LOG_WARNING << "Authentication failed";
366             forward_unauthorized::sendUnauthorized(
367                 req->url, req->getHeaderValue("X-Requested-With"),
368                 req->getHeaderValue("Accept"), res);
369             completeRequest(res);
370             return;
371         }
372 #endif // BMCWEB_INSECURE_DISABLE_AUTHX
373         auto asyncResp = std::make_shared<bmcweb::AsyncResp>();
374         BMCWEB_LOG_DEBUG << "Setting completion handler";
375         asyncResp->res.setCompleteRequestHandler(
376             [self(shared_from_this())](crow::Response& thisRes) {
377             self->completeRequest(thisRes);
378         });
379 
380         if (thisReq.isUpgrade() &&
381             boost::iequals(
382                 thisReq.getHeaderValue(boost::beast::http::field::upgrade),
383                 "websocket"))
384         {
385             handler->handleUpgrade(thisReq, res, std::move(adaptor));
386             // delete lambda with self shared_ptr
387             // to enable connection destruction
388             asyncResp->res.setCompleteRequestHandler(nullptr);
389             return;
390         }
391         handler->handle(thisReq, asyncResp);
392     }
393 
394     bool isAlive()
395     {
396         if constexpr (std::is_same_v<Adaptor,
397                                      boost::beast::ssl_stream<
398                                          boost::asio::ip::tcp::socket>>)
399         {
400             return adaptor.next_layer().is_open();
401         }
402         else
403         {
404             return adaptor.is_open();
405         }
406     }
407     void close()
408     {
409         if constexpr (std::is_same_v<Adaptor,
410                                      boost::beast::ssl_stream<
411                                          boost::asio::ip::tcp::socket>>)
412         {
413             adaptor.next_layer().close();
414             if (sessionIsFromTransport && userSession != nullptr)
415             {
416                 BMCWEB_LOG_DEBUG
417                     << this
418                     << " Removing TLS session: " << userSession->uniqueId;
419                 persistent_data::SessionStore::getInstance().removeSession(
420                     userSession);
421             }
422         }
423         else
424         {
425             adaptor.close();
426         }
427     }
428 
429     void completeRequest(crow::Response& thisRes)
430     {
431         if (!req)
432         {
433             return;
434         }
435         res = std::move(thisRes);
436         BMCWEB_LOG_INFO << "Response: " << this << ' ' << req->url << ' '
437                         << res.resultInt() << " keepalive=" << req->keepAlive();
438 
439         addSecurityHeaders(*req, res);
440 
441         crow::authentication::cleanupTempSession(*req);
442 
443         if (!isAlive())
444         {
445             // BMCWEB_LOG_DEBUG << this << " delete (socket is closed) " <<
446             // isReading
447             // << ' ' << isWriting;
448             // delete this;
449 
450             // delete lambda with self shared_ptr
451             // to enable connection destruction
452             res.setCompleteRequestHandler(nullptr);
453             return;
454         }
455         if (res.body().empty() && !res.jsonValue.empty())
456         {
457             if (http_helpers::requestPrefersHtml(req->getHeaderValue("Accept")))
458             {
459                 prettyPrintJson(res);
460             }
461             else
462             {
463                 res.addHeader(boost::beast::http::field::content_type,
464                               "application/json");
465                 res.body() = res.jsonValue.dump(
466                     2, ' ', true, nlohmann::json::error_handler_t::replace);
467             }
468         }
469 
470         if (res.resultInt() >= 400 && res.body().empty())
471         {
472             res.body() = std::string(res.reason());
473         }
474 
475         if (res.result() == boost::beast::http::status::no_content)
476         {
477             // Boost beast throws if content is provided on a no-content
478             // response.  Ideally, this would never happen, but in the case that
479             // it does, we don't want to throw.
480             BMCWEB_LOG_CRITICAL
481                 << this << " Response content provided but code was no-content";
482             res.body().clear();
483         }
484 
485         res.addHeader(boost::beast::http::field::date, getCachedDateStr());
486 
487         res.keepAlive(req->keepAlive());
488 
489         doWrite(res);
490 
491         // delete lambda with self shared_ptr
492         // to enable connection destruction
493         res.setCompleteRequestHandler(nullptr);
494     }
495 
496     void readClientIp()
497     {
498         boost::asio::ip::address ip;
499         boost::system::error_code ec = getClientIp(ip);
500         if (ec)
501         {
502             return;
503         }
504         req->ipAddress = ip;
505     }
506 
507     boost::system::error_code getClientIp(boost::asio::ip::address& ip)
508     {
509         boost::system::error_code ec;
510         BMCWEB_LOG_DEBUG << "Fetch the client IP address";
511         boost::asio::ip::tcp::endpoint endpoint =
512             boost::beast::get_lowest_layer(adaptor).remote_endpoint(ec);
513 
514         if (ec)
515         {
516             // If remote endpoint fails keep going. "ClientOriginIPAddress"
517             // will be empty.
518             BMCWEB_LOG_ERROR << "Failed to get the client's IP Address. ec : "
519                              << ec;
520             return ec;
521         }
522         ip = endpoint.address();
523         return ec;
524     }
525 
526   private:
527     void doReadHeaders()
528     {
529         BMCWEB_LOG_DEBUG << this << " doReadHeaders";
530 
531         // Clean up any previous Connection.
532         boost::beast::http::async_read_header(
533             adaptor, buffer, *parser,
534             [this,
535              self(shared_from_this())](const boost::system::error_code& ec,
536                                        std::size_t bytesTransferred) {
537             BMCWEB_LOG_DEBUG << this << " async_read_header "
538                              << bytesTransferred << " Bytes";
539             bool errorWhileReading = false;
540             if (ec)
541             {
542                 errorWhileReading = true;
543                 if (ec == boost::asio::error::eof)
544                 {
545                     BMCWEB_LOG_WARNING
546                         << this << " Error while reading: " << ec.message();
547                 }
548                 else
549                 {
550                     BMCWEB_LOG_ERROR
551                         << this << " Error while reading: " << ec.message();
552                 }
553             }
554             else
555             {
556                 // if the adaptor isn't open anymore, and wasn't handed to a
557                 // websocket, treat as an error
558                 if (!isAlive() &&
559                     !boost::beast::websocket::is_upgrade(parser->get()))
560                 {
561                     errorWhileReading = true;
562                 }
563             }
564 
565             cancelDeadlineTimer();
566 
567             if (errorWhileReading)
568             {
569                 close();
570                 BMCWEB_LOG_DEBUG << this << " from read(1)";
571                 return;
572             }
573 
574             readClientIp();
575 
576             boost::asio::ip::address ip;
577             if (getClientIp(ip))
578             {
579                 BMCWEB_LOG_DEBUG << "Unable to get client IP";
580             }
581             sessionIsFromTransport = false;
582 #ifndef BMCWEB_INSECURE_DISABLE_AUTHX
583             boost::beast::http::verb method = parser->get().method();
584             userSession = crow::authentication::authenticate(
585                 ip, res, method, parser->get().base(), userSession);
586 
587             bool loggedIn = userSession != nullptr;
588             if (!loggedIn)
589             {
590                 const boost::optional<uint64_t> contentLength =
591                     parser->content_length();
592                 if (contentLength && *contentLength > loggedOutPostBodyLimit)
593                 {
594                     BMCWEB_LOG_DEBUG << "Content length greater than limit "
595                                      << *contentLength;
596                     close();
597                     return;
598                 }
599 
600                 BMCWEB_LOG_DEBUG << "Starting quick deadline";
601             }
602 #endif // BMCWEB_INSECURE_DISABLE_AUTHX
603 
604             doRead();
605             });
606     }
607 
608     void doRead()
609     {
610         BMCWEB_LOG_DEBUG << this << " doRead";
611         startDeadline();
612         boost::beast::http::async_read(adaptor, buffer, *parser,
613                                        [this, self(shared_from_this())](
614                                            const boost::system::error_code& ec,
615                                            std::size_t bytesTransferred) {
616             BMCWEB_LOG_DEBUG << this << " async_read " << bytesTransferred
617                              << " Bytes";
618             cancelDeadlineTimer();
619             if (ec)
620             {
621                 BMCWEB_LOG_ERROR << this
622                                  << " Error while reading: " << ec.message();
623                 close();
624                 BMCWEB_LOG_DEBUG << this << " from read(1)";
625                 return;
626             }
627             handle();
628         });
629     }
630 
631     void doWrite(crow::Response& thisRes)
632     {
633         BMCWEB_LOG_DEBUG << this << " doWrite";
634         thisRes.preparePayload();
635         serializer.emplace(*thisRes.stringResponse);
636         startDeadline();
637         boost::beast::http::async_write(adaptor, *serializer,
638                                         [this, self(shared_from_this())](
639                                             const boost::system::error_code& ec,
640                                             std::size_t bytesTransferred) {
641             BMCWEB_LOG_DEBUG << this << " async_write " << bytesTransferred
642                              << " bytes";
643 
644             cancelDeadlineTimer();
645 
646             if (ec)
647             {
648                 BMCWEB_LOG_DEBUG << this << " from write(2)";
649                 return;
650             }
651             if (!res.keepAlive())
652             {
653                 close();
654                 BMCWEB_LOG_DEBUG << this << " from write(1)";
655                 return;
656             }
657 
658             serializer.reset();
659             BMCWEB_LOG_DEBUG << this << " Clearing response";
660             res.clear();
661             parser.emplace(std::piecewise_construct, std::make_tuple());
662             parser->body_limit(httpReqBodyLimit); // reset body limit for
663                                                   // newly created parser
664             buffer.consume(buffer.size());
665 
666             // If the session was built from the transport, we don't need to
667             // clear it.  All other sessions are generated per request.
668             if (!sessionIsFromTransport)
669             {
670                 userSession = nullptr;
671             }
672 
673             // Destroy the Request via the std::optional
674             req.reset();
675             doReadHeaders();
676         });
677     }
678 
679     void cancelDeadlineTimer()
680     {
681         timer.cancel();
682     }
683 
684     void startDeadline()
685     {
686         cancelDeadlineTimer();
687 
688         std::chrono::seconds timeout(15);
689         // allow slow uploads for logged in users
690         bool loggedIn = userSession != nullptr;
691         if (loggedIn)
692         {
693             timeout = std::chrono::seconds(60);
694             return;
695         }
696 
697         std::weak_ptr<Connection<Adaptor, Handler>> weakSelf = weak_from_this();
698         timer.expires_after(timeout);
699         timer.async_wait([weakSelf](const boost::system::error_code ec) {
700             // Note, we are ignoring other types of errors here;  If the timer
701             // failed for any reason, we should still close the connection
702 
703             std::shared_ptr<Connection<Adaptor, Handler>> self =
704                 weakSelf.lock();
705             if (!self)
706             {
707                 BMCWEB_LOG_CRITICAL << self << " Failed to capture connection";
708                 return;
709             }
710             if (ec == boost::asio::error::operation_aborted)
711             {
712                 // Canceled wait means the path succeeeded.
713                 return;
714             }
715             if (ec)
716             {
717                 BMCWEB_LOG_CRITICAL << self << " timer failed " << ec;
718             }
719 
720             BMCWEB_LOG_WARNING << self << "Connection timed out, closing";
721 
722             self->close();
723         });
724 
725         BMCWEB_LOG_DEBUG << this << " timer started";
726     }
727 
728     Adaptor adaptor;
729     Handler* handler;
730     // Making this a std::optional allows it to be efficiently destroyed and
731     // re-created on Connection reset
732     std::optional<
733         boost::beast::http::request_parser<boost::beast::http::string_body>>
734         parser;
735 
736     boost::beast::flat_static_buffer<8192> buffer;
737 
738     std::optional<boost::beast::http::response_serializer<
739         boost::beast::http::string_body>>
740         serializer;
741 
742     std::optional<crow::Request> req;
743     crow::Response res;
744 
745     bool sessionIsFromTransport = false;
746     std::shared_ptr<persistent_data::UserSession> userSession;
747 
748     boost::asio::steady_timer timer;
749 
750     std::function<std::string()>& getCachedDateStr;
751 
752     using std::enable_shared_from_this<
753         Connection<Adaptor, Handler>>::shared_from_this;
754 
755     using std::enable_shared_from_this<
756         Connection<Adaptor, Handler>>::weak_from_this;
757 };
758 } // namespace crow
759