xmltooling/soap/impl/CURLSOAPTransport.cpp

   1 /*
   2  *  Copyright 2001-2007 Internet2
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /**
  18  * CURLSOAPTransport.cpp
  19  *
  20  * libcurl-based SOAPTransport implementation
  21  */
  22
  23 #include "internal.h"
  24 #include "exceptions.h"
  25 #include "security/CredentialCriteria.h"
  26 #include "security/OpenSSLTrustEngine.h"
  27 #include "security/OpenSSLCredential.h"
  28 #include "soap/HTTPSOAPTransport.h"
  29 #include "soap/OpenSSLSOAPTransport.h"
  30 #include "util/NDC.h"
  31 #include "util/Threads.h"
  32
  33 #include <list>
  34 #include <curl/curl.h>
  35 #include <log4cpp/Category.hh>
  36 #include <openssl/x509_vfy.h>
  37
  38 using namespace xmltooling;
  39 using namespace log4cpp;
  40 using namespace std;
  41
  42 namespace xmltooling {
  43
  44     // Manages cache of socket connections via CURL handles.
  45     class XMLTOOL_DLLLOCAL CURLPool
  46     {
  47     public:
  48         CURLPool() : m_size(0), m_lock(Mutex::create()),
  49             m_log(Category::getInstance(XMLTOOLING_LOGCAT".SOAPTransport.CURLPool")) {}
  50         ~CURLPool();
  51
  52         CURL* get(const char* to, const char* endpoint);
  53         void put(const char* to, const char* endpoint, CURL* handle);
  54
  55     private:
  56         typedef map<string,vector<CURL*> > poolmap_t;
  57         poolmap_t m_bindingMap;
  58         list< vector<CURL*>* > m_pools;
  59         long m_size;
  60         Mutex* m_lock;
  61         Category& m_log;
  62     };
  63
  64     static XMLTOOL_DLLLOCAL CURLPool* g_CURLPool = NULL;
  65
  66     class XMLTOOL_DLLLOCAL CURLSOAPTransport : public HTTPSOAPTransport, public OpenSSLSOAPTransport
  67     {
  68     public:
  69         CURLSOAPTransport(const char* peerName, const char* endpoint)
  70                 : m_peerName(peerName ? peerName : ""), m_endpoint(endpoint), m_handle(NULL), m_headers(NULL),
  71 #ifndef XMLTOOLING_NO_XMLSEC
  72                     m_cred(NULL), m_trustEngine(NULL), m_peerResolver(NULL), m_mandatory(false),
  73 #endif
  74                     m_ssl_callback(NULL), m_ssl_userptr(NULL), m_chunked(true), m_secure(false) {
  75             m_handle = g_CURLPool->get(peerName, endpoint);
  76             curl_easy_setopt(m_handle,CURLOPT_URL,endpoint);
  77             curl_easy_setopt(m_handle,CURLOPT_CONNECTTIMEOUT,15);
  78             curl_easy_setopt(m_handle,CURLOPT_TIMEOUT,30);
  79             curl_easy_setopt(m_handle,CURLOPT_HTTPAUTH,0);
  80             curl_easy_setopt(m_handle,CURLOPT_USERPWD,NULL);
  81             curl_easy_setopt(m_handle,CURLOPT_HEADERDATA,this);
  82             m_headers=curl_slist_append(m_headers,"Content-Type: text/xml");
  83         }
  84
  85         virtual ~CURLSOAPTransport() {
  86             curl_slist_free_all(m_headers);
  87             curl_easy_setopt(m_handle,CURLOPT_ERRORBUFFER,NULL);
  88             curl_easy_setopt(m_handle,CURLOPT_PRIVATE,m_secure ? "secure" : NULL); // Save off security "state".
  89             g_CURLPool->put(m_peerName.c_str(), m_endpoint.c_str(), m_handle);
  90         }
  91
  92         bool isConfidential() const {
  93             return m_endpoint.find("https")==0;
  94         }
  95
  96         bool setConnectTimeout(long timeout) {
  97             return (curl_easy_setopt(m_handle,CURLOPT_CONNECTTIMEOUT,timeout)==CURLE_OK);
  98         }
  99
 100         bool setTimeout(long timeout) {
 101             return (curl_easy_setopt(m_handle,CURLOPT_TIMEOUT,timeout)==CURLE_OK);
 102         }
 103
 104         bool setAuth(transport_auth_t authType, const char* username=NULL, const char* password=NULL);
 105
 106 #ifndef XMLTOOLING_NO_XMLSEC
 107         bool setCredential(const Credential* cred=NULL) {
 108             const OpenSSLCredential* down = dynamic_cast<const OpenSSLCredential*>(cred);
 109             if (!down) {
 110                 m_cred = NULL;
 111                 return (cred==NULL);
 112             }
 113             m_cred = down;
 114             return true;
 115         }
 116
 117         bool setTrustEngine(
 118             const X509TrustEngine* trustEngine=NULL,
 119             const CredentialResolver* peerResolver=NULL,
 120             CredentialCriteria* criteria=NULL,
 121             bool mandatory=true
 122             ) {
 123             const OpenSSLTrustEngine* down = dynamic_cast<const OpenSSLTrustEngine*>(trustEngine);
 124             if (!down) {
 125                 m_trustEngine = NULL;
 126                 m_peerResolver = NULL;
 127                 m_criteria = NULL;
 128                 return (trustEngine==NULL);
 129             }
 130             m_trustEngine = down;
 131             m_peerResolver = peerResolver;
 132             m_criteria = criteria;
 133             m_mandatory = mandatory;
 134             return true;
 135         }
 136
 137 #endif
 138
 139         bool useChunkedEncoding(bool chunked=true) {
 140             m_chunked = chunked;
 141             return true;
 142         }
 143
 144         void send(istream& in);
 145
 146         istream& receive() {
 147             return m_stream;
 148         }
 149
 150         bool isSecure() const {
 151             return m_secure;
 152         }
 153
 154         void setSecure(bool secure) {
 155             m_secure = secure;
 156         }
 157
 158         string getContentType() const;
 159
 160         bool setRequestHeader(const char* name, const char* val) {
 161             string temp(name);
 162             temp=temp + ": " + val;
 163             m_headers=curl_slist_append(m_headers,temp.c_str());
 164             return true;
 165         }
 166
 167         const vector<string>& getResponseHeader(const char* val) const;
 168
 169         bool setSSLCallback(ssl_ctx_callback_fn fn, void* userptr=NULL) {
 170             m_ssl_callback=fn;
 171             m_ssl_userptr=userptr;
 172             return true;
 173         }
 174
 175     private:
 176         // per-call state
 177         string m_peerName,m_endpoint;
 178         CURL* m_handle;
 179         stringstream m_stream;
 180         struct curl_slist* m_headers;
 181         map<string,vector<string> > m_response_headers;
 182 #ifndef XMLTOOLING_NO_XMLSEC
 183         const OpenSSLCredential* m_cred;
 184         const OpenSSLTrustEngine* m_trustEngine;
 185         const CredentialResolver* m_peerResolver;
 186         CredentialCriteria* m_criteria;
 187         bool m_mandatory;
 188 #endif
 189         ssl_ctx_callback_fn m_ssl_callback;
 190         void* m_ssl_userptr;
 191         bool m_chunked;
 192         bool m_secure;
 193
 194         friend size_t XMLTOOL_DLLLOCAL curl_header_hook(void* ptr, size_t size, size_t nmemb, void* stream);
 195         friend CURLcode XMLTOOL_DLLLOCAL xml_ssl_ctx_callback(CURL* curl, SSL_CTX* ssl_ctx, void* userptr);
 196         friend int XMLTOOL_DLLLOCAL verify_callback(X509_STORE_CTX* x509_ctx, void* arg);
 197     };
 198
 199     // libcurl callback functions
 200     size_t XMLTOOL_DLLLOCAL curl_header_hook(void* ptr, size_t size, size_t nmemb, void* stream);
 201     size_t XMLTOOL_DLLLOCAL curl_write_hook(void* ptr, size_t size, size_t nmemb, void* stream);
 202     size_t XMLTOOL_DLLLOCAL curl_read_hook( void *ptr, size_t size, size_t nmemb, void *stream);
 203     int XMLTOOL_DLLLOCAL curl_debug_hook(CURL* handle, curl_infotype type, char* data, size_t len, void* ptr);
 204     CURLcode XMLTOOL_DLLLOCAL xml_ssl_ctx_callback(CURL* curl, SSL_CTX* ssl_ctx, void* userptr);
 205 #ifndef XMLTOOLING_NO_XMLSEC
 206     int XMLTOOL_DLLLOCAL verify_callback(X509_STORE_CTX* x509_ctx, void* arg);
 207 #endif
 208
 209     SOAPTransport* CURLSOAPTransportFactory(const pair<const char*,const char*>& dest)
 210     {
 211         return new CURLSOAPTransport(dest.first, dest.second);
 212     }
 213 };
 214
 215 void xmltooling::registerSOAPTransports()
 216 {
 217     XMLToolingConfig& conf=XMLToolingConfig::getConfig();
 218     conf.SOAPTransportManager.registerFactory("http", CURLSOAPTransportFactory);
 219     conf.SOAPTransportManager.registerFactory("https", CURLSOAPTransportFactory);
 220 }
 221
 222 void xmltooling::initSOAPTransports()
 223 {
 224     g_CURLPool=new CURLPool();
 225 }
 226
 227 void xmltooling::termSOAPTransports()
 228 {
 229     delete g_CURLPool;
 230     g_CURLPool = NULL;
 231 }
 232
 233 CURLPool::~CURLPool()
 234 {
 235     for (poolmap_t::iterator i=m_bindingMap.begin(); i!=m_bindingMap.end(); i++) {
 236         for (vector<CURL*>::iterator j=i->second.begin(); j!=i->second.end(); j++)
 237             curl_easy_cleanup(*j);
 238     }
 239     delete m_lock;
 240 }
 241
 242 CURL* CURLPool::get(const char* to, const char* endpoint)
 243 {
 244 #ifdef _DEBUG
 245     xmltooling::NDC("get");
 246 #endif
 247     m_log.debug("getting connection handle to %s", endpoint);
 248     m_lock->lock();
 249     poolmap_t::iterator i=m_bindingMap.find(string(to) + "|" + endpoint);
 250
 251     if (i!=m_bindingMap.end()) {
 252         // Move this pool to the front of the list.
 253         m_pools.remove(&(i->second));
 254         m_pools.push_front(&(i->second));
 255
 256         // If a free connection exists, return it.
 257         if (!(i->second.empty())) {
 258             CURL* handle=i->second.back();
 259             i->second.pop_back();
 260             m_size--;
 261             m_lock->unlock();
 262             m_log.debug("returning existing connection handle from pool");
 263             return handle;
 264         }
 265     }
 266
 267     m_lock->unlock();
 268     m_log.debug("nothing free in pool, returning new connection handle");
 269
 270     // Create a new connection and set non-varying options.
 271     CURL* handle=curl_easy_init();
 272     if (!handle)
 273         return NULL;
 274     curl_easy_setopt(handle,CURLOPT_NOPROGRESS,1);
 275     curl_easy_setopt(handle,CURLOPT_NOSIGNAL,1);
 276     curl_easy_setopt(handle,CURLOPT_FAILONERROR,1);
 277     curl_easy_setopt(handle,CURLOPT_SSLVERSION,3);
 278     // Verification of the peer is via TrustEngine only.
 279     curl_easy_setopt(handle,CURLOPT_SSL_VERIFYPEER,0);
 280     curl_easy_setopt(handle,CURLOPT_SSL_VERIFYHOST,2);
 281     curl_easy_setopt(handle,CURLOPT_HEADERFUNCTION,&curl_header_hook);
 282     curl_easy_setopt(handle,CURLOPT_WRITEFUNCTION,&curl_write_hook);
 283     curl_easy_setopt(handle,CURLOPT_DEBUGFUNCTION,&curl_debug_hook);
 284
 285     return handle;
 286 }
 287
 288 void CURLPool::put(const char* to, const char* endpoint, CURL* handle)
 289 {
 290     string key = string(to) + "|" + endpoint;
 291     m_lock->lock();
 292     poolmap_t::iterator i=m_bindingMap.find(key);
 293     if (i==m_bindingMap.end())
 294         m_pools.push_front(&(m_bindingMap.insert(poolmap_t::value_type(key,vector<CURL*>(1,handle))).first->second));
 295     else
 296         i->second.push_back(handle);
 297
 298     CURL* killit=NULL;
 299     if (++m_size > 256) {
 300         // Kick a handle out from the back of the bus.
 301         while (true) {
 302             vector<CURL*>* corpse=m_pools.back();
 303             if (!corpse->empty()) {
 304                 killit=corpse->back();
 305                 corpse->pop_back();
 306                 m_size--;
 307                 break;
 308             }
 309
 310             // Move an empty pool up to the front so we don't keep hitting it.
 311             m_pools.pop_back();
 312             m_pools.push_front(corpse);
 313         }
 314     }
 315     m_lock->unlock();
 316     if (killit) {
 317         curl_easy_cleanup(killit);
 318 #ifdef _DEBUG
 319         xmltooling::NDC("put");
 320 #endif
 321         m_log.info("conn_pool_max limit reached, dropping an old connection");
 322     }
 323 }
 324
 325 bool CURLSOAPTransport::setAuth(transport_auth_t authType, const char* username, const char* password)
 326 {
 327     if (authType==transport_auth_none) {
 328         if (curl_easy_setopt(m_handle,CURLOPT_HTTPAUTH,0)!=CURLE_OK)
 329             return false;
 330         return (curl_easy_setopt(m_handle,CURLOPT_USERPWD,NULL)==CURLE_OK);
 331     }
 332     long flag=0;
 333     switch (authType) {
 334         case transport_auth_basic:    flag = CURLAUTH_BASIC; break;
 335         case transport_auth_digest:   flag = CURLAUTH_DIGEST; break;
 336         case transport_auth_ntlm:     flag = CURLAUTH_NTLM; break;
 337         case transport_auth_gss:      flag = CURLAUTH_GSSNEGOTIATE; break;
 338         default:            return false;
 339     }
 340     if (curl_easy_setopt(m_handle,CURLOPT_HTTPAUTH,flag)!=CURLE_OK)
 341         return false;
 342     string creds = string(username ? username : "") + ':' + (password ? password : "");
 343     return (curl_easy_setopt(m_handle,CURLOPT_USERPWD,creds.c_str())==CURLE_OK);
 344 }
 345
 346 const vector<string>& CURLSOAPTransport::getResponseHeader(const char* name) const
 347 {
 348     static vector<string> emptyVector;
 349
 350     map<string,vector<string> >::const_iterator i=m_response_headers.find(name);
 351     if (i!=m_response_headers.end())
 352         return i->second;
 353
 354     for (map<string,vector<string> >::const_iterator j=m_response_headers.begin(); j!=m_response_headers.end(); j++) {
 355 #ifdef HAVE_STRCASECMP
 356         if (!strcasecmp(j->first.c_str(), name))
 357 #else
 358         if (!stricmp(j->first.c_str(), name))
 359 #endif
 360             return j->second;
 361     }
 362
 363     return emptyVector;
 364 }
 365
 366 string CURLSOAPTransport::getContentType() const
 367 {
 368     char* content_type=NULL;
 369     curl_easy_getinfo(m_handle,CURLINFO_CONTENT_TYPE,&content_type);
 370     return content_type ? content_type : "";
 371 }
 372
 373 void CURLSOAPTransport::send(istream& in)
 374 {
 375 #ifdef _DEBUG
 376     xmltooling::NDC ndc("send");
 377 #endif
 378     Category& log=Category::getInstance(XMLTOOLING_LOGCAT".SOAPTransport");
 379     Category& log_curl=Category::getInstance(XMLTOOLING_LOGCAT".libcurl");
 380
 381     string msg;
 382
 383     // By this time, the handle has been prepared with the URL to use and the
 384     // caller should have executed any set functions to manipulate it.
 385
 386     // Setup standard per-call curl properties.
 387     curl_easy_setopt(m_handle,CURLOPT_DEBUGDATA,&log_curl);
 388     curl_easy_setopt(m_handle,CURLOPT_FILE,&m_stream);
 389     curl_easy_setopt(m_handle,CURLOPT_POST,1);
 390     if (m_chunked) {
 391         m_headers=curl_slist_append(m_headers,"Transfer-Encoding: chunked");
 392         curl_easy_setopt(m_handle,CURLOPT_READFUNCTION,&curl_read_hook);
 393         curl_easy_setopt(m_handle,CURLOPT_READDATA,&in);
 394     }
 395     else {
 396         char buf[1024];
 397         while (in) {
 398             in.read(buf,1024);
 399             msg.append(buf,in.gcount());
 400         }
 401         curl_easy_setopt(m_handle,CURLOPT_READFUNCTION,NULL);
 402         curl_easy_setopt(m_handle,CURLOPT_POSTFIELDS,msg.c_str());
 403         curl_easy_setopt(m_handle,CURLOPT_POSTFIELDSIZE,msg.length());
 404     }
 405
 406     char curl_errorbuf[CURL_ERROR_SIZE];
 407     curl_errorbuf[0]=0;
 408     curl_easy_setopt(m_handle,CURLOPT_ERRORBUFFER,curl_errorbuf);
 409     if (log_curl.isDebugEnabled())
 410         curl_easy_setopt(m_handle,CURLOPT_VERBOSE,1);
 411
 412     // Set request headers.
 413     curl_easy_setopt(m_handle,CURLOPT_HTTPHEADER,m_headers);
 414
 415     if (m_ssl_callback || m_cred || m_trustEngine) {
 416         curl_easy_setopt(m_handle,CURLOPT_SSL_CTX_FUNCTION,xml_ssl_ctx_callback);
 417         curl_easy_setopt(m_handle,CURLOPT_SSL_CTX_DATA,this);
 418
 419         // Restore security "state". Necessary because the callback only runs
 420         // when handshakes occur. Even new TCP connections won't execute it.
 421         char* priv=NULL;
 422         curl_easy_getinfo(m_handle,CURLINFO_PRIVATE,&priv);
 423         if (priv)
 424             m_secure=true;
 425     }
 426     else {
 427         curl_easy_setopt(m_handle,CURLOPT_SSL_CTX_FUNCTION,NULL);
 428         curl_easy_setopt(m_handle,CURLOPT_SSL_CTX_DATA,NULL);
 429     }
 430
 431     // Make the call.
 432     log.debug("sending SOAP message to %s", m_endpoint.c_str());
 433     if (curl_easy_perform(m_handle) != CURLE_OK) {
 434         throw IOException(
 435             string("CURLSOAPTransport failed while contacting SOAP responder: ") +
 436                 (curl_errorbuf[0] ? curl_errorbuf : "no further information available"));
 437     }
 438 }
 439
 440 // callback to buffer headers from server
 441 size_t xmltooling::curl_header_hook(void* ptr, size_t size, size_t nmemb, void* stream)
 442 {
 443     // only handle single-byte data
 444     if (size!=1)
 445         return 0;
 446     CURLSOAPTransport* ctx = reinterpret_cast<CURLSOAPTransport*>(stream);
 447     char* buf = (char*)malloc(nmemb + 1);
 448     if (buf) {
 449         memset(buf,0,nmemb + 1);
 450         memcpy(buf,ptr,nmemb);
 451         char* sep=(char*)strchr(buf,':');
 452         if (sep) {
 453             *(sep++)=0;
 454             while (*sep==' ')
 455                 *(sep++)=0;
 456             char* white=buf+nmemb-1;
 457             while (isspace(*white))
 458                 *(white--)=0;
 459             ctx->m_response_headers[buf].push_back(sep);
 460         }
 461         free(buf);
 462         return nmemb;
 463     }
 464     return 0;
 465 }
 466
 467 // callback to send data to server
 468 size_t xmltooling::curl_read_hook(void* ptr, size_t size, size_t nmemb, void* stream)
 469 {
 470     // *stream is actually an istream object
 471     istream& buf=*(reinterpret_cast<istream*>(stream));
 472     buf.read(reinterpret_cast<char*>(ptr),size*nmemb);
 473     return buf.gcount();
 474 }
 475
 476 // callback to buffer data from server
 477 size_t xmltooling::curl_write_hook(void* ptr, size_t size, size_t nmemb, void* stream)
 478 {
 479     size_t len = size*nmemb;
 480     reinterpret_cast<stringstream*>(stream)->write(reinterpret_cast<const char*>(ptr),len);
 481     return len;
 482 }
 483
 484 // callback for curl debug data
 485 int xmltooling::curl_debug_hook(CURL* handle, curl_infotype type, char* data, size_t len, void* ptr)
 486 {
 487     // *ptr is actually a logging object
 488     if (!ptr) return 0;
 489     CategoryStream log=reinterpret_cast<Category*>(ptr)->debugStream();
 490     for (char* ch=data; len && (isprint(*ch) || isspace(*ch)); len--)
 491         log << *ch++;
 492     log << CategoryStream::ENDLINE;
 493     return 0;
 494 }
 495
 496 #ifndef XMLTOOLING_NO_XMLSEC
 497 int xmltooling::verify_callback(X509_STORE_CTX* x509_ctx, void* arg)
 498 {
 499     Category& log = Category::getInstance("OpenSSL");
 500     log.debug("invoking X509 verify callback");
 501 #if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
 502     CURLSOAPTransport* ctx = reinterpret_cast<CURLSOAPTransport*>(arg);
 503 #else
 504     // Yes, this sucks. I'd use TLS, but there's no really obvious spot to put the thread key
 505     // and global variables suck too. We can't access the X509_STORE_CTX depth directly because
 506     // OpenSSL only copies it into the context if it's >=0, and the unsigned pointer may be
 507     // negative in the SSL structure's int member.
 508     CURLSOAPTransport* ctx = reinterpret_cast<CURLSOAPTransport*>(
 509         SSL_get_verify_depth(
 510             reinterpret_cast<SSL*>(X509_STORE_CTX_get_ex_data(x509_ctx,SSL_get_ex_data_X509_STORE_CTX_idx()))
 511             )
 512         );
 513 #endif
 514
 515     bool success=false;
 516     if (ctx->m_criteria) {
 517         ctx->m_criteria->setUsage(CredentialCriteria::TLS_CREDENTIAL);
 518         // Bypass name check (handled for us by curl).
 519         ctx->m_criteria->setPeerName(NULL);
 520         success = ctx->m_trustEngine->validate(x509_ctx->cert,x509_ctx->untrusted,*(ctx->m_peerResolver),ctx->m_criteria);
 521     }
 522     else {
 523         // Bypass name check (handled for us by curl).
 524         CredentialCriteria cc;
 525         cc.setUsage(CredentialCriteria::TLS_CREDENTIAL);
 526         success = ctx->m_trustEngine->validate(x509_ctx->cert,x509_ctx->untrusted,*(ctx->m_peerResolver),&cc);
 527     }
 528
 529     if (!success) {
 530         log.error("supplied TrustEngine failed to validate SSL/TLS server certificate");
 531         x509_ctx->error=X509_V_ERR_APPLICATION_VERIFICATION;     // generic error, check log for plugin specifics
 532         ctx->setSecure(false);
 533         return ctx->m_mandatory ? 0 : 1;
 534     }
 535
 536     // Signal success. Hopefully it doesn't matter what's actually in the structure now.
 537     ctx->setSecure(true);
 538     return 1;
 539 }
 540 #endif
 541
 542 // callback to invoke a caller-defined SSL callback
 543 CURLcode xmltooling::xml_ssl_ctx_callback(CURL* curl, SSL_CTX* ssl_ctx, void* userptr)
 544 {
 545     CURLSOAPTransport* conf = reinterpret_cast<CURLSOAPTransport*>(userptr);
 546
 547 #ifndef XMLTOOLING_NO_XMLSEC
 548     if (conf->m_cred)
 549         conf->m_cred->attach(ssl_ctx);
 550
 551     if (conf->m_trustEngine) {
 552         SSL_CTX_set_verify(ssl_ctx,SSL_VERIFY_PEER,NULL);
 553 #if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
 554         // With 0.9.7, we can pass a callback argument directly.
 555         SSL_CTX_set_cert_verify_callback(ssl_ctx,verify_callback,userptr);
 556 #else
 557         // With 0.9.6, there's no argument, so we're going to use a really embarrassing hack and
 558         // stuff the argument in the depth property where it will get copied to the context object
 559         // that's handed to the callback.
 560         SSL_CTX_set_cert_verify_callback(ssl_ctx,reinterpret_cast<int (*)()>(verify_callback),NULL);
 561         SSL_CTX_set_verify_depth(ssl_ctx,reinterpret_cast<int>(userptr));
 562 #endif
 563     }
 564 #endif
 565
 566     if (conf->m_ssl_callback && !conf->m_ssl_callback(conf, ssl_ctx, conf->m_ssl_userptr))
 567         return CURLE_SSL_CERTPROBLEM;
 568
 569     return CURLE_OK;
 570 }