xmltooling/security/impl/AbstractPKIXTrustEngine.cpp

   1 /*
   2  *  Copyright 2001-2010 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  * AbstractPKIXTrustEngine.cpp
  19  *
  20  * A trust engine that uses X.509 trust anchors and CRLs associated with a KeyInfoSource
  21  * to perform PKIX validation of signatures and certificates.
  22  */
  23
  24 #include "internal.h"
  25 #include "logging.h"
  26 #include "security/AbstractPKIXTrustEngine.h"
  27 #include "signature/KeyInfo.h"
  28 #include "signature/Signature.h"
  29 #include "security/CredentialCriteria.h"
  30 #include "security/CredentialResolver.h"
  31 #include "security/KeyInfoResolver.h"
  32 #include "security/OpenSSLCryptoX509CRL.h"
  33 #include "security/X509Credential.h"
  34 #include "signature/SignatureValidator.h"
  35 #include "util/NDC.h"
  36
  37 #include <openssl/x509_vfy.h>
  38 #include <openssl/x509v3.h>
  39 #include <xercesc/util/XMLUniDefs.hpp>
  40 #include <xsec/enc/OpenSSL/OpenSSLCryptoX509.hpp>
  41
  42 using namespace xmlsignature;
  43 using namespace xmltooling::logging;
  44 using namespace xmltooling;
  45 using namespace std;
  46
  47
  48 namespace {
  49     static int XMLTOOL_DLLLOCAL error_callback(int ok, X509_STORE_CTX* ctx)
  50     {
  51         if (!ok)
  52             Category::getInstance("OpenSSL").error("path validation failure: %s", X509_verify_cert_error_string(ctx->error));
  53         return ok;
  54     }
  55
  56     static bool XMLTOOL_DLLLOCAL validate(
  57         X509* EE,
  58         STACK_OF(X509)* untrusted,
  59         AbstractPKIXTrustEngine::PKIXValidationInfoIterator* pkixInfo,
  60                 bool useCRL,
  61         bool fullCRLChain,
  62         const vector<XSECCryptoX509CRL*>* inlineCRLs=nullptr
  63         )
  64     {
  65         Category& log=Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine");
  66
  67         // First we build a stack of CA certs. These objects are all referenced in place.
  68         log.debug("supplying PKIX Validation information");
  69
  70         // We need this for CRL support.
  71         X509_STORE* store=X509_STORE_new();
  72         if (!store) {
  73             log_openssl();
  74             return false;
  75         }
  76
  77         STACK_OF(X509)* CAstack = sk_X509_new_null();
  78
  79         // This contains the state of the validate operation.
  80         int count=0;
  81         X509_STORE_CTX ctx;
  82
  83         const vector<XSECCryptoX509*>& CAcerts = pkixInfo->getTrustAnchors();
  84         for (vector<XSECCryptoX509*>::const_iterator i=CAcerts.begin(); i!=CAcerts.end(); ++i) {
  85             if ((*i)->getProviderName()==DSIGConstants::s_unicodeStrPROVOpenSSL) {
  86                 sk_X509_push(CAstack,static_cast<OpenSSLCryptoX509*>(*i)->getOpenSSLX509());
  87                 ++count;
  88             }
  89         }
  90
  91         log.debug("supplied (%d) CA certificate(s)", count);
  92
  93         if (useCRL) {
  94 #if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
  95             count=0;
  96             if (inlineCRLs) {
  97                 for (vector<XSECCryptoX509CRL*>::const_iterator j=inlineCRLs->begin(); j!=inlineCRLs->end(); ++j) {
  98                     if ((*j)->getProviderName()==DSIGConstants::s_unicodeStrPROVOpenSSL) {
  99                         // owned by store
 100                         X509_STORE_add_crl(store, X509_CRL_dup(static_cast<OpenSSLCryptoX509CRL*>(*j)->getOpenSSLX509CRL()));
 101                         ++count;
 102                     }
 103                 }
 104             }
 105             const vector<XSECCryptoX509CRL*>& crls = pkixInfo->getCRLs();
 106             for (vector<XSECCryptoX509CRL*>::const_iterator j=crls.begin(); j!=crls.end(); ++j) {
 107                 if ((*j)->getProviderName()==DSIGConstants::s_unicodeStrPROVOpenSSL) {
 108                     // owned by store
 109                     X509_STORE_add_crl(store, X509_CRL_dup(static_cast<OpenSSLCryptoX509CRL*>(*j)->getOpenSSLX509CRL()));
 110                     ++count;
 111                 }
 112             }
 113             log.debug("supplied (%d) CRL(s)", count);
 114             if (count > 0) {
 115                 X509_STORE_set_flags(store, fullCRLChain ? (X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL) : (X509_V_FLAG_CRL_CHECK));
 116                     }
 117                     else {
 118                             log.warn("CRL checking is enabled, but none were supplied");
 119                 sk_X509_free(CAstack);
 120                 X509_STORE_free(store);
 121                 return false;
 122                     }
 123 #else
 124                         log.warn("CRL checking is enabled, but OpenSSL version is too old");
 125             sk_X509_free(CAstack);
 126             X509_STORE_free(store);
 127             return false;
 128 #endif
 129         }
 130
 131         // AFAICT, EE and untrusted are passed in but not owned by the ctx.
 132 #if (OPENSSL_VERSION_NUMBER >= 0x00907000L)
 133         if (X509_STORE_CTX_init(&ctx,store,EE,untrusted)!=1) {
 134             log_openssl();
 135             log.error("unable to initialize X509_STORE_CTX");
 136             sk_X509_free(CAstack);
 137             X509_STORE_free(store);
 138             return false;
 139         }
 140 #else
 141         X509_STORE_CTX_init(&ctx,store,EE,untrusted);
 142 #endif
 143
 144         // Seems to be most efficient to just pass in the CA stack.
 145         X509_STORE_CTX_trusted_stack(&ctx,CAstack);
 146         X509_STORE_CTX_set_depth(&ctx,100);    // we check the depth down below
 147         X509_STORE_CTX_set_verify_cb(&ctx,error_callback);
 148
 149         int ret=X509_verify_cert(&ctx);
 150         if (ret==1) {
 151             // Now see if the depth was acceptable by counting the number of intermediates.
 152             int depth=sk_X509_num(ctx.chain)-2;
 153             if (pkixInfo->getVerificationDepth() < depth) {
 154                 log.error(
 155                     "certificate chain was too long (%d intermediates, only %d allowed)",
 156                     (depth==-1) ? 0 : depth,
 157                     pkixInfo->getVerificationDepth()
 158                     );
 159                 ret=0;
 160             }
 161         }
 162
 163         // Clean up...
 164         X509_STORE_CTX_cleanup(&ctx);
 165         X509_STORE_free(store);
 166         sk_X509_free(CAstack);
 167
 168         if (ret==1) {
 169             log.debug("successfully validated certificate chain");
 170             return true;
 171         }
 172
 173         return false;
 174     }
 175
 176     static XMLCh fullCRLChain[] =               UNICODE_LITERAL_12(f,u,l,l,C,R,L,C,h,a,i,n);
 177         static XMLCh checkRevocation[] =        UNICODE_LITERAL_15(c,h,e,c,k,R,e,v,o,c,a,t,i,o,n);
 178 };
 179
 180 AbstractPKIXTrustEngine::PKIXValidationInfoIterator::PKIXValidationInfoIterator()
 181 {
 182 }
 183
 184 AbstractPKIXTrustEngine::PKIXValidationInfoIterator::~PKIXValidationInfoIterator()
 185 {
 186 }
 187
 188 AbstractPKIXTrustEngine::AbstractPKIXTrustEngine(const xercesc::DOMElement* e)
 189         : TrustEngine(e),
 190                 m_fullCRLChain(XMLHelper::getAttrBool(e, false, fullCRLChain)),
 191                 m_checkRevocation(XMLHelper::getAttrString(e, nullptr, checkRevocation))
 192 {
 193     if (m_fullCRLChain) {
 194         Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX").warn(
 195             "fullCRLChain option is deprecated, setting checkRevocation to \"fullChain\""
 196             );
 197         m_checkRevocation = "fullChain";
 198     }
 199     else if (m_checkRevocation == "fullChain") {
 200         m_fullCRLChain = true; // in case anything's using this
 201     }
 202 }
 203
 204 AbstractPKIXTrustEngine::~AbstractPKIXTrustEngine()
 205 {
 206 }
 207
 208 bool AbstractPKIXTrustEngine::checkEntityNames(
 209     X509* certEE, const CredentialResolver& credResolver, const CredentialCriteria& criteria
 210     ) const
 211 {
 212     Category& log=Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX");
 213
 214     // We resolve to a set of trusted credentials.
 215     vector<const Credential*> creds;
 216     credResolver.resolve(creds,&criteria);
 217
 218     // Build a list of acceptable names.
 219     set<string> trustednames;
 220     trustednames.insert(criteria.getPeerName());
 221     for (vector<const Credential*>::const_iterator cred = creds.begin(); cred!=creds.end(); ++cred)
 222         trustednames.insert((*cred)->getKeyNames().begin(), (*cred)->getKeyNames().end());
 223
 224     X509_NAME* subject=X509_get_subject_name(certEE);
 225     if (subject) {
 226         // One way is a direct match to the subject DN.
 227         // Seems that the way to do the compare is to write the X509_NAME into a BIO.
 228         BIO* b = BIO_new(BIO_s_mem());
 229         BIO* b2 = BIO_new(BIO_s_mem());
 230         // The flags give us LDAP order instead of X.500, with a comma separator.
 231         X509_NAME_print_ex(b,subject,0,XN_FLAG_RFC2253);
 232         BIO_flush(b);
 233         // The flags give us LDAP order instead of X.500, with a comma plus space separator.
 234         X509_NAME_print_ex(b2,subject,0,XN_FLAG_RFC2253 + XN_FLAG_SEP_CPLUS_SPC - XN_FLAG_SEP_COMMA_PLUS);
 235         BIO_flush(b2);
 236
 237         BUF_MEM* bptr=nullptr;
 238         BUF_MEM* bptr2=nullptr;
 239         BIO_get_mem_ptr(b, &bptr);
 240         BIO_get_mem_ptr(b2, &bptr2);
 241
 242         if (bptr && bptr->length > 0 && log.isDebugEnabled()) {
 243             string subjectstr(bptr->data, bptr->length);
 244             log.debug("certificate subject: %s", subjectstr.c_str());
 245         }
 246
 247         // Check each keyname.
 248         for (set<string>::const_iterator n=trustednames.begin(); bptr && bptr2 && n!=trustednames.end(); n++) {
 249 #ifdef HAVE_STRCASECMP
 250             if ((n->length() == bptr->length && !strncasecmp(n->c_str(), bptr->data, bptr->length)) ||
 251                 (n->length() == bptr2->length && !strncasecmp(n->c_str(), bptr2->data, bptr2->length))) {
 252 #else
 253             if ((n->length() == bptr->length && !strnicmp(n->c_str(), bptr->data, bptr->length)) ||
 254                 (n->length() == bptr2->length && !strnicmp(n->c_str(), bptr2->data, bptr2->length))) {
 255 #endif
 256                 log.debug("matched full subject DN to a key name (%s)", n->c_str());
 257                 BIO_free(b);
 258                 BIO_free(b2);
 259                 return true;
 260             }
 261         }
 262         BIO_free(b);
 263         BIO_free(b2);
 264
 265         log.debug("unable to match DN, trying TLS subjectAltName match");
 266         STACK_OF(GENERAL_NAME)* altnames=(STACK_OF(GENERAL_NAME)*)X509_get_ext_d2i(certEE, NID_subject_alt_name, nullptr, nullptr);
 267         if (altnames) {
 268             int numalts = sk_GENERAL_NAME_num(altnames);
 269             for (int an=0; an<numalts; an++) {
 270                 const GENERAL_NAME* check = sk_GENERAL_NAME_value(altnames, an);
 271                 if (check->type==GEN_DNS || check->type==GEN_URI) {
 272                     const char* altptr = (char*)ASN1_STRING_data(check->d.ia5);
 273                     const int altlen = ASN1_STRING_length(check->d.ia5);
 274                     for (set<string>::const_iterator n=trustednames.begin(); n!=trustednames.end(); n++) {
 275 #ifdef HAVE_STRCASECMP
 276                         if ((check->type==GEN_DNS && n->length()==altlen && !strncasecmp(altptr,n->c_str(),altlen))
 277 #else
 278                         if ((check->type==GEN_DNS && n->length()==altlen && !strnicmp(altptr,n->c_str(),altlen))
 279 #endif
 280                                 || (check->type==GEN_URI && n->length()==altlen && !strncmp(altptr,n->c_str(),altlen))) {
 281                             log.debug("matched DNS/URI subjectAltName to a key name (%s)", n->c_str());
 282                             GENERAL_NAMES_free(altnames);
 283                             return true;
 284                         }
 285                     }
 286                 }
 287             }
 288         }
 289         GENERAL_NAMES_free(altnames);
 290
 291         log.debug("unable to match subjectAltName, trying TLS CN match");
 292
 293         // Fetch the last CN RDN.
 294         char* peer_CN = nullptr;
 295         int j,i = -1;
 296         while ((j=X509_NAME_get_index_by_NID(subject, NID_commonName, i)) >= 0)
 297             i = j;
 298         if (i >= 0) {
 299             ASN1_STRING* tmp = X509_NAME_ENTRY_get_data(X509_NAME_get_entry(subject, i));
 300             // Copied in from libcurl.
 301             /* In OpenSSL 0.9.7d and earlier, ASN1_STRING_to_UTF8 fails if the input
 302                is already UTF-8 encoded. We check for this case and copy the raw
 303                string manually to avoid the problem. */
 304             if(tmp && ASN1_STRING_type(tmp) == V_ASN1_UTF8STRING) {
 305                 j = ASN1_STRING_length(tmp);
 306                 if(j >= 0) {
 307                     peer_CN = (char*)OPENSSL_malloc(j + 1);
 308                     memcpy(peer_CN, ASN1_STRING_data(tmp), j);
 309                     peer_CN[j] = '\0';
 310                 }
 311             }
 312             else /* not a UTF8 name */ {
 313                 j = ASN1_STRING_to_UTF8(reinterpret_cast<unsigned char**>(&peer_CN), tmp);
 314             }
 315
 316             for (set<string>::const_iterator n=trustednames.begin(); n!=trustednames.end(); n++) {
 317 #ifdef HAVE_STRCASECMP
 318                 if (n->length() == j && !strncasecmp(peer_CN, n->c_str(), j)) {
 319 #else
 320                 if (n->length() == j && !strnicmp(peer_CN, n->c_str(), j)) {
 321 #endif
 322                     log.debug("matched subject CN to a key name (%s)", n->c_str());
 323                     if(peer_CN)
 324                         OPENSSL_free(peer_CN);
 325                     return true;
 326                 }
 327             }
 328             if(peer_CN)
 329                 OPENSSL_free(peer_CN);
 330         }
 331         else {
 332             log.warn("no common name in certificate subject");
 333         }
 334     }
 335     else {
 336         log.error("certificate has no subject?!");
 337     }
 338
 339     return false;
 340 }
 341
 342 bool AbstractPKIXTrustEngine::validateWithCRLs(
 343     X509* certEE,
 344     STACK_OF(X509)* certChain,
 345     const CredentialResolver& credResolver,
 346     CredentialCriteria* criteria,
 347     const std::vector<XSECCryptoX509CRL*>* inlineCRLs
 348     ) const
 349 {
 350 #ifdef _DEBUG
 351     NDC ndc("validateWithCRLs");
 352 #endif
 353     Category& log=Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX");
 354
 355     if (!certEE) {
 356         log.error("X.509 credential was NULL, unable to perform validation");
 357         return false;
 358     }
 359
 360     if (criteria && criteria->getPeerName() && *(criteria->getPeerName())) {
 361         log.debug("checking that the certificate name is acceptable");
 362         if (criteria->getUsage()==Credential::UNSPECIFIED_CREDENTIAL)
 363             criteria->setUsage(Credential::SIGNING_CREDENTIAL);
 364         if (!checkEntityNames(certEE,credResolver,*criteria)) {
 365             log.error("certificate name was not acceptable");
 366             return false;
 367         }
 368     }
 369
 370     log.debug("performing certificate path validation...");
 371
 372     auto_ptr<PKIXValidationInfoIterator> pkix(getPKIXValidationInfoIterator(credResolver, criteria));
 373     while (pkix->next()) {
 374         if (::validate(
 375                                 certEE,
 376                                 certChain,
 377                                 pkix.get(),
 378                                 (m_checkRevocation=="entityOnly" || m_checkRevocation=="fullChain"),
 379                                 (m_checkRevocation=="fullChain"),
 380                                 (m_checkRevocation=="entityOnly" || m_checkRevocation=="fullChain") ? inlineCRLs : nullptr
 381                                 )) {
 382             return true;
 383         }
 384     }
 385
 386     log.debug("failed to validate certificate chain using supplied PKIX information");
 387     return false;
 388 }
 389
 390 bool AbstractPKIXTrustEngine::validate(
 391     X509* certEE,
 392     STACK_OF(X509)* certChain,
 393     const CredentialResolver& credResolver,
 394     CredentialCriteria* criteria
 395     ) const
 396 {
 397     return validateWithCRLs(certEE,certChain,credResolver,criteria);
 398 }
 399
 400 bool AbstractPKIXTrustEngine::validate(
 401     XSECCryptoX509* certEE,
 402     const vector<XSECCryptoX509*>& certChain,
 403     const CredentialResolver& credResolver,
 404     CredentialCriteria* criteria
 405     ) const
 406 {
 407 #ifdef _DEBUG
 408         NDC ndc("validate");
 409 #endif
 410     if (!certEE) {
 411         Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX").error("X.509 credential was NULL, unable to perform validation");
 412         return false;
 413     }
 414     else if (certEE->getProviderName()!=DSIGConstants::s_unicodeStrPROVOpenSSL) {
 415         Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX").error("only the OpenSSL XSEC provider is supported");
 416         return false;
 417     }
 418
 419     STACK_OF(X509)* untrusted=sk_X509_new_null();
 420     for (vector<XSECCryptoX509*>::const_iterator i=certChain.begin(); i!=certChain.end(); ++i)
 421         sk_X509_push(untrusted,static_cast<OpenSSLCryptoX509*>(*i)->getOpenSSLX509());
 422
 423     bool ret = validate(static_cast<OpenSSLCryptoX509*>(certEE)->getOpenSSLX509(), untrusted, credResolver, criteria);
 424     sk_X509_free(untrusted);
 425     return ret;
 426 }
 427
 428 bool AbstractPKIXTrustEngine::validate(
 429     Signature& sig,
 430     const CredentialResolver& credResolver,
 431     CredentialCriteria* criteria
 432     ) const
 433 {
 434 #ifdef _DEBUG
 435     NDC ndc("validate");
 436 #endif
 437     Category& log=Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX");
 438
 439     const KeyInfoResolver* inlineResolver = m_keyInfoResolver;
 440     if (!inlineResolver)
 441         inlineResolver = XMLToolingConfig::getConfig().getKeyInfoResolver();
 442     if (!inlineResolver) {
 443         log.error("unable to perform PKIX validation, no KeyInfoResolver available");
 444         return false;
 445     }
 446
 447     // Pull the certificate chain out of the signature.
 448     X509Credential* x509cred;
 449     auto_ptr<Credential> cred(inlineResolver->resolve(&sig,X509Credential::RESOLVE_CERTS|X509Credential::RESOLVE_CRLS));
 450     if (!cred.get() || !(x509cred=dynamic_cast<X509Credential*>(cred.get()))) {
 451         log.error("unable to perform PKIX validation, signature does not contain any certificates");
 452         return false;
 453     }
 454     const vector<XSECCryptoX509*>& certs = x509cred->getEntityCertificateChain();
 455     if (certs.empty()) {
 456         log.error("unable to perform PKIX validation, signature does not contain any certificates");
 457         return false;
 458     }
 459
 460     log.debug("validating signature using certificate from within the signature");
 461
 462     // Find and save off a pointer to the certificate that unlocks the object.
 463     // Most of the time, this will be the first one anyway.
 464     XSECCryptoX509* certEE=nullptr;
 465     SignatureValidator keyValidator;
 466     for (vector<XSECCryptoX509*>::const_iterator i=certs.begin(); !certEE && i!=certs.end(); ++i) {
 467         try {
 468             auto_ptr<XSECCryptoKey> key((*i)->clonePublicKey());
 469             keyValidator.setKey(key.get());
 470             keyValidator.validate(&sig);
 471             log.debug("signature verified with key inside signature, attempting certificate validation...");
 472             certEE=(*i);
 473         }
 474         catch (ValidationException& ex) {
 475             log.debug(ex.what());
 476         }
 477     }
 478
 479     if (!certEE) {
 480         log.debug("failed to verify signature with embedded certificates");
 481         return false;
 482     }
 483     else if (certEE->getProviderName()!=DSIGConstants::s_unicodeStrPROVOpenSSL) {
 484         log.error("only the OpenSSL XSEC provider is supported");
 485         return false;
 486     }
 487
 488     STACK_OF(X509)* untrusted=sk_X509_new_null();
 489     for (vector<XSECCryptoX509*>::const_iterator i=certs.begin(); i!=certs.end(); ++i)
 490         sk_X509_push(untrusted,static_cast<OpenSSLCryptoX509*>(*i)->getOpenSSLX509());
 491     const vector<XSECCryptoX509CRL*>& crls = x509cred->getCRLs();
 492     bool ret = validateWithCRLs(static_cast<OpenSSLCryptoX509*>(certEE)->getOpenSSLX509(), untrusted, credResolver, criteria, &crls);
 493     sk_X509_free(untrusted);
 494     return ret;
 495 }
 496
 497 bool AbstractPKIXTrustEngine::validate(
 498     const XMLCh* sigAlgorithm,
 499     const char* sig,
 500     KeyInfo* keyInfo,
 501     const char* in,
 502     unsigned int in_len,
 503     const CredentialResolver& credResolver,
 504     CredentialCriteria* criteria
 505     ) const
 506 {
 507 #ifdef _DEBUG
 508     NDC ndc("validate");
 509 #endif
 510     Category& log=Category::getInstance(XMLTOOLING_LOGCAT".TrustEngine.PKIX");
 511
 512     if (!keyInfo) {
 513         log.error("unable to perform PKIX validation, KeyInfo not present");
 514         return false;
 515     }
 516
 517     const KeyInfoResolver* inlineResolver = m_keyInfoResolver;
 518     if (!inlineResolver)
 519         inlineResolver = XMLToolingConfig::getConfig().getKeyInfoResolver();
 520     if (!inlineResolver) {
 521         log.error("unable to perform PKIX validation, no KeyInfoResolver available");
 522         return false;
 523     }
 524
 525     // Pull the certificate chain out of the signature.
 526     X509Credential* x509cred;
 527     auto_ptr<Credential> cred(inlineResolver->resolve(keyInfo,X509Credential::RESOLVE_CERTS));
 528     if (!cred.get() || !(x509cred=dynamic_cast<X509Credential*>(cred.get()))) {
 529         log.error("unable to perform PKIX validation, KeyInfo does not contain any certificates");
 530         return false;
 531     }
 532     const vector<XSECCryptoX509*>& certs = x509cred->getEntityCertificateChain();
 533     if (certs.empty()) {
 534         log.error("unable to perform PKIX validation, KeyInfo does not contain any certificates");
 535         return false;
 536     }
 537
 538     log.debug("validating signature using certificate from within KeyInfo");
 539
 540     // Find and save off a pointer to the certificate that unlocks the object.
 541     // Most of the time, this will be the first one anyway.
 542     XSECCryptoX509* certEE=nullptr;
 543     for (vector<XSECCryptoX509*>::const_iterator i=certs.begin(); !certEE && i!=certs.end(); ++i) {
 544         try {
 545             auto_ptr<XSECCryptoKey> key((*i)->clonePublicKey());
 546             if (Signature::verifyRawSignature(key.get(), sigAlgorithm, sig, in, in_len)) {
 547                 log.debug("signature verified with key inside signature, attempting certificate validation...");
 548                 certEE=(*i);
 549             }
 550         }
 551         catch (SignatureException& ex) {
 552             log.debug(ex.what());
 553         }
 554     }
 555
 556     if (!certEE) {
 557         log.debug("failed to verify signature with embedded certificates");
 558         return false;
 559     }
 560     else if (certEE->getProviderName()!=DSIGConstants::s_unicodeStrPROVOpenSSL) {
 561         log.error("only the OpenSSL XSEC provider is supported");
 562         return false;
 563     }
 564
 565     STACK_OF(X509)* untrusted=sk_X509_new_null();
 566     for (vector<XSECCryptoX509*>::const_iterator i=certs.begin(); i!=certs.end(); ++i)
 567         sk_X509_push(untrusted,static_cast<OpenSSLCryptoX509*>(*i)->getOpenSSLX509());
 568     const vector<XSECCryptoX509CRL*>& crls = x509cred->getCRLs();
 569     bool ret = validateWithCRLs(static_cast<OpenSSLCryptoX509*>(certEE)->getOpenSSLX509(), untrusted, credResolver, criteria, &crls);
 570     sk_X509_free(untrusted);
 571     return ret;
 572 }