net/cert/cert_verify_proc_nss.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/cert/cert_verify_proc_nss.h"

#include <string>
#include <vector>

#include <cert.h>
#include <nss.h>
#include <prerror.h>
#include <secerr.h>
#include <sechash.h>
#include <sslerr.h>

#include "base/logging.h"
#include "crypto/nss_util.h"
#include "crypto/scoped_nss_types.h"
#include "crypto/sha2.h"
#include "net/base/net_errors.h"
#include "net/cert/asn1_util.h"
#include "net/cert/cert_status_flags.h"
#include "net/cert/cert_verifier.h"
#include "net/cert/cert_verify_result.h"
#include "net/cert/crl_set.h"
#include "net/cert/ev_root_ca_metadata.h"
#include "net/cert/x509_certificate.h"
#include "net/cert/x509_util_nss.h"

#if defined(OS_IOS)
#include <CommonCrypto/CommonDigest.h>
#include "net/cert/x509_util_ios.h"
#endif  // defined(OS_IOS)

#define NSS_VERSION_NUM (NSS_VMAJOR * 10000 + NSS_VMINOR * 100 + NSS_VPATCH)
#if NSS_VERSION_NUM < 31305
// Added in NSS 3.13.5.
#define SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED -8016
#endif

#if NSS_VERSION_NUM < 31402
// Added in NSS 3.14.2.
#define cert_pi_useOnlyTrustAnchors static_cast<CERTValParamInType>(14)
#endif

namespace net {

namespace {

typedef scoped_ptr_malloc<
    CERTCertificatePolicies,
    crypto::NSSDestroyer<CERTCertificatePolicies,
                         CERT_DestroyCertificatePoliciesExtension> >
    ScopedCERTCertificatePolicies;

typedef scoped_ptr_malloc<
    CERTCertList,
    crypto::NSSDestroyer<CERTCertList, CERT_DestroyCertList> >
    ScopedCERTCertList;

// ScopedCERTValOutParam manages destruction of values in the CERTValOutParam
// array that cvout points to.  cvout must be initialized as passed to
// CERT_PKIXVerifyCert, so that the array must be terminated with
// cert_po_end type.
// When it goes out of scope, it destroys values of cert_po_trustAnchor
// and cert_po_certList types, but doesn't release the array itself.
class ScopedCERTValOutParam {
 public:
  explicit ScopedCERTValOutParam(CERTValOutParam* cvout)
      : cvout_(cvout) {}

  ~ScopedCERTValOutParam() {
    if (cvout_ == NULL)
      return;
    for (CERTValOutParam *p = cvout_; p->type != cert_po_end; p++) {
      switch (p->type) {
        case cert_po_trustAnchor:
          if (p->value.pointer.cert) {
            CERT_DestroyCertificate(p->value.pointer.cert);
            p->value.pointer.cert = NULL;
          }
          break;
        case cert_po_certList:
          if (p->value.pointer.chain) {
            CERT_DestroyCertList(p->value.pointer.chain);
            p->value.pointer.chain = NULL;
          }
          break;
        default:
          break;
      }
    }
  }

 private:
  CERTValOutParam* cvout_;

  DISALLOW_COPY_AND_ASSIGN(ScopedCERTValOutParam);
};

// Map PORT_GetError() return values to our network error codes.
int MapSecurityError(int err) {
  switch (err) {
    case PR_DIRECTORY_LOOKUP_ERROR:  // DNS lookup error.
      return ERR_NAME_NOT_RESOLVED;
    case SEC_ERROR_INVALID_ARGS:
      return ERR_INVALID_ARGUMENT;
    case SSL_ERROR_BAD_CERT_DOMAIN:
      return ERR_CERT_COMMON_NAME_INVALID;
    case SEC_ERROR_INVALID_TIME:
    case SEC_ERROR_EXPIRED_CERTIFICATE:
    case SEC_ERROR_EXPIRED_ISSUER_CERTIFICATE:
      return ERR_CERT_DATE_INVALID;
    case SEC_ERROR_UNKNOWN_ISSUER:
    case SEC_ERROR_UNTRUSTED_ISSUER:
    case SEC_ERROR_CA_CERT_INVALID:
      return ERR_CERT_AUTHORITY_INVALID;
    // TODO(port): map ERR_CERT_NO_REVOCATION_MECHANISM.
    case SEC_ERROR_OCSP_BAD_HTTP_RESPONSE:
    case SEC_ERROR_OCSP_SERVER_ERROR:
      return ERR_CERT_UNABLE_TO_CHECK_REVOCATION;
    case SEC_ERROR_REVOKED_CERTIFICATE:
    case SEC_ERROR_UNTRUSTED_CERT:  // Treat as revoked.
      return ERR_CERT_REVOKED;
    case SEC_ERROR_BAD_DER:
    case SEC_ERROR_BAD_SIGNATURE:
    case SEC_ERROR_CERT_NOT_VALID:
    // TODO(port): add an ERR_CERT_WRONG_USAGE error code.
    case SEC_ERROR_CERT_USAGES_INVALID:
    case SEC_ERROR_INADEQUATE_KEY_USAGE:  // Key usage.
    case SEC_ERROR_INADEQUATE_CERT_TYPE:  // Extended key usage and whether
                                          // the certificate is a CA.
    case SEC_ERROR_POLICY_VALIDATION_FAILED:
    case SEC_ERROR_CERT_NOT_IN_NAME_SPACE:
    case SEC_ERROR_PATH_LEN_CONSTRAINT_INVALID:
    case SEC_ERROR_UNKNOWN_CRITICAL_EXTENSION:
    case SEC_ERROR_EXTENSION_VALUE_INVALID:
      return ERR_CERT_INVALID;
    case SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED:
      return ERR_CERT_WEAK_SIGNATURE_ALGORITHM;
    default:
      LOG(WARNING) << "Unknown error " << err << " mapped to net::ERR_FAILED";
      return ERR_FAILED;
  }
}

// Map PORT_GetError() return values to our cert status flags.
CertStatus MapCertErrorToCertStatus(int err) {
  int net_error = MapSecurityError(err);
  return MapNetErrorToCertStatus(net_error);
}

// Saves some information about the certificate chain cert_list in
// *verify_result.  The caller MUST initialize *verify_result before calling
// this function.
// Note that cert_list[0] is the end entity certificate.
void GetCertChainInfo(CERTCertList* cert_list,
                      CERTCertificate* root_cert,
                      CertVerifyResult* verify_result) {
  // NOTE: Using a NSS library before 3.12.3.1 will crash below.  To see the
  // NSS version currently in use:
  // 1. use ldd on the chrome executable for NSS's location (ie. libnss3.so*)
  // 2. use ident libnss3.so* for the library's version
  DCHECK(cert_list);

  CERTCertificate* verified_cert = NULL;
  std::vector<CERTCertificate*> verified_chain;
  int i = 0;
  for (CERTCertListNode* node = CERT_LIST_HEAD(cert_list);
       !CERT_LIST_END(node, cert_list);
       node = CERT_LIST_NEXT(node), ++i) {
    if (i == 0) {
      verified_cert = node->cert;
    } else {
      // Because of an NSS bug, CERT_PKIXVerifyCert may chain a self-signed
      // certificate of a root CA to another certificate of the same root CA
      // key.  Detect that error and ignore the root CA certificate.
      // See https://bugzilla.mozilla.org/show_bug.cgi?id=721288.
      if (node->cert->isRoot) {
        // NOTE: isRoot doesn't mean the certificate is a trust anchor.  It
        // means the certificate is self-signed.  Here we assume isRoot only
        // implies the certificate is self-issued.
        CERTCertListNode* next_node = CERT_LIST_NEXT(node);
        CERTCertificate* next_cert;
        if (!CERT_LIST_END(next_node, cert_list)) {
          next_cert = next_node->cert;
        } else {
          next_cert = root_cert;
        }
        // Test that |node->cert| is actually a self-signed certificate
        // whose key is equal to |next_cert|, and not a self-issued
        // certificate signed by another key of the same CA.
        if (next_cert && SECITEM_ItemsAreEqual(&node->cert->derPublicKey,
                                               &next_cert->derPublicKey)) {
          continue;
        }
      }
      verified_chain.push_back(node->cert);
    }

    SECAlgorithmID& signature = node->cert->signature;
    SECOidTag oid_tag = SECOID_FindOIDTag(&signature.algorithm);
    switch (oid_tag) {
      case SEC_OID_PKCS1_MD5_WITH_RSA_ENCRYPTION:
        verify_result->has_md5 = true;
        if (i != 0)
          verify_result->has_md5_ca = true;
        break;
      case SEC_OID_PKCS1_MD2_WITH_RSA_ENCRYPTION:
        verify_result->has_md2 = true;
        if (i != 0)
          verify_result->has_md2_ca = true;
        break;
      case SEC_OID_PKCS1_MD4_WITH_RSA_ENCRYPTION:
        verify_result->has_md4 = true;
        break;
      default:
        break;
    }
  }

  if (root_cert)
    verified_chain.push_back(root_cert);
#if defined(OS_IOS)
  verify_result->verified_cert =
      x509_util_ios::CreateCertFromNSSHandles(verified_cert, verified_chain);
#else
  verify_result->verified_cert =
      X509Certificate::CreateFromHandle(verified_cert, verified_chain);
#endif  // defined(OS_IOS)
}

// IsKnownRoot returns true if the given certificate is one that we believe
// is a standard (as opposed to user-installed) root.
bool IsKnownRoot(CERTCertificate* root) {
  if (!root || !root->slot)
    return false;

  // This magic name is taken from
  // http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/security/nss/lib/ckfw/builtins/constants.c&rev=1.13&mark=86,89#79
  return 0 == strcmp(PK11_GetSlotName(root->slot),
                     "NSS Builtin Objects");
}

// Returns true if the given certificate is one of the additional trust anchors.
bool IsAdditionalTrustAnchor(CERTCertList* additional_trust_anchors,
                             CERTCertificate* root) {
  if (!additional_trust_anchors || !root)
    return false;
  for (CERTCertListNode* node = CERT_LIST_HEAD(additional_trust_anchors);
       !CERT_LIST_END(node, additional_trust_anchors);
       node = CERT_LIST_NEXT(node)) {
    if (CERT_CompareCerts(node->cert, root))
      return true;
  }
  return false;
}

enum CRLSetResult {
  kCRLSetRevoked,
  kCRLSetOk,
  kCRLSetError,
};

// CheckRevocationWithCRLSet attempts to check each element of |cert_list|
// against |crl_set|. It returns:
//   kCRLSetRevoked: if any element of the chain is known to have been revoked.
//   kCRLSetError: if an error occurs in processing.
//   kCRLSetOk: if no element in the chain is known to have been revoked.
CRLSetResult CheckRevocationWithCRLSet(CERTCertList* cert_list,
                                       CERTCertificate* root,
                                       CRLSet* crl_set) {
  std::vector<CERTCertificate*> certs;

  if (cert_list) {
    for (CERTCertListNode* node = CERT_LIST_HEAD(cert_list);
         !CERT_LIST_END(node, cert_list);
         node = CERT_LIST_NEXT(node)) {
      certs.push_back(node->cert);
    }
  }
  if (root)
    certs.push_back(root);

  // We iterate from the root certificate down to the leaf, keeping track of
  // the issuer's SPKI at each step.
  std::string issuer_spki_hash;
  for (std::vector<CERTCertificate*>::reverse_iterator i = certs.rbegin();
       i != certs.rend(); ++i) {
    CERTCertificate* cert = *i;

    base::StringPiece der(reinterpret_cast<char*>(cert->derCert.data),
                          cert->derCert.len);

    base::StringPiece spki;
    if (!asn1::ExtractSPKIFromDERCert(der, &spki)) {
      NOTREACHED();
      return kCRLSetError;
    }
    const std::string spki_hash = crypto::SHA256HashString(spki);

    base::StringPiece serial_number = base::StringPiece(
        reinterpret_cast<char*>(cert->serialNumber.data),
        cert->serialNumber.len);

    CRLSet::Result result = crl_set->CheckSPKI(spki_hash);

    if (result != CRLSet::REVOKED && !issuer_spki_hash.empty())
      result = crl_set->CheckSerial(serial_number, issuer_spki_hash);

    issuer_spki_hash = spki_hash;

    switch (result) {
      case CRLSet::REVOKED:
        return kCRLSetRevoked;
      case CRLSet::UNKNOWN:
      case CRLSet::GOOD:
        continue;
      default:
        NOTREACHED();
        return kCRLSetError;
    }
  }

  return kCRLSetOk;
}

// Forward declarations.
SECStatus RetryPKIXVerifyCertWithWorkarounds(
    CERTCertificate* cert_handle, int num_policy_oids,
    bool cert_io_enabled, std::vector<CERTValInParam>* cvin,
    CERTValOutParam* cvout);
SECOidTag GetFirstCertPolicy(CERTCertificate* cert_handle);

// Call CERT_PKIXVerifyCert for the cert_handle.
// Verification results are stored in an array of CERTValOutParam.
// If policy_oids is not NULL and num_policy_oids is positive, policies
// are also checked.
// additional_trust_anchors is an optional list of certificates that can be
// trusted as anchors when building a certificate chain.
// Caller must initialize cvout before calling this function.
SECStatus PKIXVerifyCert(CERTCertificate* cert_handle,
                         bool check_revocation,
                         bool cert_io_enabled,
                         const SECOidTag* policy_oids,
                         int num_policy_oids,
                         CERTCertList* additional_trust_anchors,
                         CERTValOutParam* cvout) {
  bool use_crl = check_revocation;
  bool use_ocsp = check_revocation;

  // These CAs have multiple keys, which trigger two bugs in NSS's CRL code.
  // 1. NSS may use one key to verify a CRL signed with another key,
  //    incorrectly concluding that the CRL's signature is invalid.
  //    Hopefully this bug will be fixed in NSS 3.12.9.
  // 2. NSS considers all certificates issued by the CA as revoked when it
  //    receives a CRL with an invalid signature.  This overly strict policy
  //    has been relaxed in NSS 3.12.7.  See
  //    https://bugzilla.mozilla.org/show_bug.cgi?id=562542.
  // So we have to turn off CRL checking for these CAs.  See
  // http://crbug.com/55695.
  static const char* const kMultipleKeyCA[] = {
    "CN=Microsoft Secure Server Authority,"
    "DC=redmond,DC=corp,DC=microsoft,DC=com",
    "CN=Microsoft Secure Server Authority",
  };

  if (!NSS_VersionCheck("3.12.7")) {
    for (size_t i = 0; i < arraysize(kMultipleKeyCA); ++i) {
      if (strcmp(cert_handle->issuerName, kMultipleKeyCA[i]) == 0) {
        use_crl = false;
        break;
      }
    }
  }

  PRUint64 revocation_method_flags =
      CERT_REV_M_DO_NOT_TEST_USING_THIS_METHOD |
      CERT_REV_M_ALLOW_NETWORK_FETCHING |
      CERT_REV_M_IGNORE_IMPLICIT_DEFAULT_SOURCE |
      CERT_REV_M_IGNORE_MISSING_FRESH_INFO |
      CERT_REV_M_STOP_TESTING_ON_FRESH_INFO;
  PRUint64 revocation_method_independent_flags =
      CERT_REV_MI_TEST_ALL_LOCAL_INFORMATION_FIRST;
  if (check_revocation && policy_oids && num_policy_oids > 0) {
    // EV verification requires revocation checking.  Consider the certificate
    // revoked if we don't have revocation info.
    // TODO(wtc): Add a bool parameter to expressly specify we're doing EV
    // verification or we want strict revocation flags.
    revocation_method_flags |= CERT_REV_M_REQUIRE_INFO_ON_MISSING_SOURCE;
    revocation_method_independent_flags |=
        CERT_REV_MI_REQUIRE_SOME_FRESH_INFO_AVAILABLE;
  } else {
    revocation_method_flags |= CERT_REV_M_SKIP_TEST_ON_MISSING_SOURCE;
    revocation_method_independent_flags |=
        CERT_REV_MI_NO_OVERALL_INFO_REQUIREMENT;
  }
  PRUint64 method_flags[2];
  method_flags[cert_revocation_method_crl] = revocation_method_flags;
  method_flags[cert_revocation_method_ocsp] = revocation_method_flags;

  if (use_crl) {
    method_flags[cert_revocation_method_crl] |=
        CERT_REV_M_TEST_USING_THIS_METHOD;
  }
  if (use_ocsp) {
    method_flags[cert_revocation_method_ocsp] |=
        CERT_REV_M_TEST_USING_THIS_METHOD;
  }

  CERTRevocationMethodIndex preferred_revocation_methods[1];
  if (use_ocsp) {
    preferred_revocation_methods[0] = cert_revocation_method_ocsp;
  } else {
    preferred_revocation_methods[0] = cert_revocation_method_crl;
  }

  CERTRevocationFlags revocation_flags;
  revocation_flags.leafTests.number_of_defined_methods =
      arraysize(method_flags);
  revocation_flags.leafTests.cert_rev_flags_per_method = method_flags;
  revocation_flags.leafTests.number_of_preferred_methods =
      arraysize(preferred_revocation_methods);
  revocation_flags.leafTests.preferred_methods = preferred_revocation_methods;
  revocation_flags.leafTests.cert_rev_method_independent_flags =
      revocation_method_independent_flags;

  revocation_flags.chainTests.number_of_defined_methods =
      arraysize(method_flags);
  revocation_flags.chainTests.cert_rev_flags_per_method = method_flags;
  revocation_flags.chainTests.number_of_preferred_methods =
      arraysize(preferred_revocation_methods);
  revocation_flags.chainTests.preferred_methods = preferred_revocation_methods;
  revocation_flags.chainTests.cert_rev_method_independent_flags =
      revocation_method_independent_flags;


  std::vector<CERTValInParam> cvin;
  cvin.reserve(7);
  CERTValInParam in_param;
  in_param.type = cert_pi_revocationFlags;
  in_param.value.pointer.revocation = &revocation_flags;
  cvin.push_back(in_param);
  if (policy_oids && num_policy_oids > 0) {
    in_param.type = cert_pi_policyOID;
    in_param.value.arraySize = num_policy_oids;
    in_param.value.array.oids = policy_oids;
    cvin.push_back(in_param);
  }
  if (additional_trust_anchors) {
    in_param.type = cert_pi_trustAnchors;
    in_param.value.pointer.chain = additional_trust_anchors;
    cvin.push_back(in_param);
    in_param.type = cert_pi_useOnlyTrustAnchors;
    in_param.value.scalar.b = PR_FALSE;
    cvin.push_back(in_param);
  }
  in_param.type = cert_pi_end;
  cvin.push_back(in_param);

  SECStatus rv = CERT_PKIXVerifyCert(cert_handle, certificateUsageSSLServer,
                                     &cvin[0], cvout, NULL);
  if (rv != SECSuccess) {
    rv = RetryPKIXVerifyCertWithWorkarounds(cert_handle, num_policy_oids,
                                            cert_io_enabled, &cvin, cvout);
  }
  return rv;
}

// PKIXVerifyCert calls this function to work around some bugs in
// CERT_PKIXVerifyCert.  All the arguments of this function are either the
// arguments or local variables of PKIXVerifyCert.
SECStatus RetryPKIXVerifyCertWithWorkarounds(
    CERTCertificate* cert_handle, int num_policy_oids,
    bool cert_io_enabled, std::vector<CERTValInParam>* cvin,
    CERTValOutParam* cvout) {
  // We call this function when the first CERT_PKIXVerifyCert call in
  // PKIXVerifyCert failed,  so we initialize |rv| to SECFailure.
  SECStatus rv = SECFailure;
  int nss_error = PORT_GetError();
  CERTValInParam in_param;

  // If we get SEC_ERROR_UNKNOWN_ISSUER, we may be missing an intermediate
  // CA certificate, so we retry with cert_pi_useAIACertFetch.
  // cert_pi_useAIACertFetch has several bugs in its error handling and
  // error reporting (NSS bug 528743), so we don't use it by default.
  // Note: When building a certificate chain, CERT_PKIXVerifyCert may
  // incorrectly pick a CA certificate with the same subject name as the
  // missing intermediate CA certificate, and  fail with the
  // SEC_ERROR_BAD_SIGNATURE error (NSS bug 524013), so we also retry with
  // cert_pi_useAIACertFetch on SEC_ERROR_BAD_SIGNATURE.
  if (cert_io_enabled &&
      (nss_error == SEC_ERROR_UNKNOWN_ISSUER ||
       nss_error == SEC_ERROR_BAD_SIGNATURE)) {
    DCHECK_EQ(cvin->back().type,  cert_pi_end);
    cvin->pop_back();
    in_param.type = cert_pi_useAIACertFetch;
    in_param.value.scalar.b = PR_TRUE;
    cvin->push_back(in_param);
    in_param.type = cert_pi_end;
    cvin->push_back(in_param);
    rv = CERT_PKIXVerifyCert(cert_handle, certificateUsageSSLServer,
                             &(*cvin)[0], cvout, NULL);
    if (rv == SECSuccess)
      return rv;
    int new_nss_error = PORT_GetError();
    if (new_nss_error == SEC_ERROR_INVALID_ARGS ||
        new_nss_error == SEC_ERROR_UNKNOWN_AIA_LOCATION_TYPE ||
        new_nss_error == SEC_ERROR_BAD_INFO_ACCESS_LOCATION ||
        new_nss_error == SEC_ERROR_BAD_HTTP_RESPONSE ||
        new_nss_error == SEC_ERROR_BAD_LDAP_RESPONSE ||
        !IS_SEC_ERROR(new_nss_error)) {
      // Use the original error code because of cert_pi_useAIACertFetch's
      // bad error reporting.
      PORT_SetError(nss_error);
      return rv;
    }
    nss_error = new_nss_error;
  }

  // If an intermediate CA certificate has requireExplicitPolicy in its
  // policyConstraints extension, CERT_PKIXVerifyCert fails with
  // SEC_ERROR_POLICY_VALIDATION_FAILED because we didn't specify any
  // certificate policy (NSS bug 552775).  So we retry with the certificate
  // policy found in the server certificate.
  if (nss_error == SEC_ERROR_POLICY_VALIDATION_FAILED &&
      num_policy_oids == 0) {
    SECOidTag policy = GetFirstCertPolicy(cert_handle);
    if (policy != SEC_OID_UNKNOWN) {
      DCHECK_EQ(cvin->back().type,  cert_pi_end);
      cvin->pop_back();
      in_param.type = cert_pi_policyOID;
      in_param.value.arraySize = 1;
      in_param.value.array.oids = &policy;
      cvin->push_back(in_param);
      in_param.type = cert_pi_end;
      cvin->push_back(in_param);
      rv = CERT_PKIXVerifyCert(cert_handle, certificateUsageSSLServer,
                               &(*cvin)[0], cvout, NULL);
      if (rv != SECSuccess) {
        // Use the original error code.
        PORT_SetError(nss_error);
      }
    }
  }

  return rv;
}

// Decodes the certificatePolicies extension of the certificate.  Returns
// NULL if the certificate doesn't have the extension or the extension can't
// be decoded.  The returned value must be freed with a
// CERT_DestroyCertificatePoliciesExtension call.
CERTCertificatePolicies* DecodeCertPolicies(
    CERTCertificate* cert_handle) {
  SECItem policy_ext;
  SECStatus rv = CERT_FindCertExtension(cert_handle,
                                        SEC_OID_X509_CERTIFICATE_POLICIES,
                                        &policy_ext);
  if (rv != SECSuccess)
    return NULL;
  CERTCertificatePolicies* policies =
      CERT_DecodeCertificatePoliciesExtension(&policy_ext);
  SECITEM_FreeItem(&policy_ext, PR_FALSE);
  return policies;
}

// Returns the OID tag for the first certificate policy in the certificate's
// certificatePolicies extension.  Returns SEC_OID_UNKNOWN if the certificate
// has no certificate policy.
SECOidTag GetFirstCertPolicy(CERTCertificate* cert_handle) {
  ScopedCERTCertificatePolicies policies(DecodeCertPolicies(cert_handle));
  if (!policies.get())
    return SEC_OID_UNKNOWN;

  CERTPolicyInfo* policy_info = policies->policyInfos[0];
  if (!policy_info)
    return SEC_OID_UNKNOWN;
  if (policy_info->oid != SEC_OID_UNKNOWN)
    return policy_info->oid;

  // The certificate policy is unknown to NSS.  We need to create a dynamic
  // OID tag for the policy.
  SECOidData od;
  od.oid.len = policy_info->policyID.len;
  od.oid.data = policy_info->policyID.data;
  od.offset = SEC_OID_UNKNOWN;
  // NSS doesn't allow us to pass an empty description, so I use a hardcoded,
  // default description here.  The description doesn't need to be unique for
  // each OID.
  od.desc = "a certificate policy";
  od.mechanism = CKM_INVALID_MECHANISM;
  od.supportedExtension = INVALID_CERT_EXTENSION;
  return SECOID_AddEntry(&od);
}

HashValue CertPublicKeyHashSHA1(CERTCertificate* cert) {
  HashValue hash(HASH_VALUE_SHA1);
#if defined(OS_IOS)
  CC_SHA1(cert->derPublicKey.data, cert->derPublicKey.len, hash.data());
#else
  SECStatus rv = HASH_HashBuf(HASH_AlgSHA1, hash.data(),
                              cert->derPublicKey.data, cert->derPublicKey.len);
  DCHECK_EQ(SECSuccess, rv);
#endif
  return hash;
}

HashValue CertPublicKeyHashSHA256(CERTCertificate* cert) {
  HashValue hash(HASH_VALUE_SHA256);
#if defined(OS_IOS)
  CC_SHA256(cert->derPublicKey.data, cert->derPublicKey.len, hash.data());
#else
  SECStatus rv = HASH_HashBuf(HASH_AlgSHA256, hash.data(),
                              cert->derPublicKey.data, cert->derPublicKey.len);
  DCHECK_EQ(rv, SECSuccess);
#endif
  return hash;
}

void AppendPublicKeyHashes(CERTCertList* cert_list,
                           CERTCertificate* root_cert,
                           HashValueVector* hashes) {
  for (CERTCertListNode* node = CERT_LIST_HEAD(cert_list);
       !CERT_LIST_END(node, cert_list);
       node = CERT_LIST_NEXT(node)) {
    hashes->push_back(CertPublicKeyHashSHA1(node->cert));
    hashes->push_back(CertPublicKeyHashSHA256(node->cert));
  }
  if (root_cert) {
    hashes->push_back(CertPublicKeyHashSHA1(root_cert));
    hashes->push_back(CertPublicKeyHashSHA256(root_cert));
  }
}

// Returns true if |cert_handle| contains a policy OID that is an EV policy
// OID according to |metadata|, storing the resulting policy OID in
// |*ev_policy_oid|. A true return is not sufficient to establish that a
// certificate is EV, but a false return is sufficient to establish the
// certificate cannot be EV.
bool IsEVCandidate(EVRootCAMetadata* metadata,
                   CERTCertificate* cert_handle,
                   SECOidTag* ev_policy_oid) {
  DCHECK(cert_handle);
  ScopedCERTCertificatePolicies policies(DecodeCertPolicies(cert_handle));
  if (!policies.get())
    return false;

  CERTPolicyInfo** policy_infos = policies->policyInfos;
  while (*policy_infos != NULL) {
    CERTPolicyInfo* policy_info = *policy_infos++;
    // If the Policy OID is unknown, that implicitly means it has not been
    // registered as an EV policy.
    if (policy_info->oid == SEC_OID_UNKNOWN)
      continue;
    if (metadata->IsEVPolicyOID(policy_info->oid)) {
      *ev_policy_oid = policy_info->oid;
      return true;
    }
  }

  return false;
}

// Studied Mozilla's code (esp. security/manager/ssl/src/nsIdentityChecking.cpp
// and nsNSSCertHelper.cpp) to learn how to verify EV certificate.
// TODO(wtc): A possible optimization is that we get the trust anchor from
// the first PKIXVerifyCert call.  We look up the EV policy for the trust
// anchor.  If the trust anchor has no EV policy, we know the cert isn't EV.
// Otherwise, we pass just that EV policy (as opposed to all the EV policies)
// to the second PKIXVerifyCert call.
bool VerifyEV(CERTCertificate* cert_handle,
              int flags,
              CRLSet* crl_set,
              EVRootCAMetadata* metadata,
              SECOidTag ev_policy_oid,
              CERTCertList* additional_trust_anchors) {
  CERTValOutParam cvout[3];
  int cvout_index = 0;
  cvout[cvout_index].type = cert_po_certList;
  cvout[cvout_index].value.pointer.chain = NULL;
  int cvout_cert_list_index = cvout_index;
  cvout_index++;
  cvout[cvout_index].type = cert_po_trustAnchor;
  cvout[cvout_index].value.pointer.cert = NULL;
  int cvout_trust_anchor_index = cvout_index;
  cvout_index++;
  cvout[cvout_index].type = cert_po_end;
  ScopedCERTValOutParam scoped_cvout(cvout);

  bool rev_checking_enabled =
      (flags & CertVerifier::VERIFY_REV_CHECKING_ENABLED) ||
      (flags & CertVerifier::VERIFY_REV_CHECKING_ENABLED_EV_ONLY);

  SECStatus status = PKIXVerifyCert(
      cert_handle,
      rev_checking_enabled,
      flags & CertVerifier::VERIFY_CERT_IO_ENABLED,
      &ev_policy_oid,
      1,
      additional_trust_anchors,
      cvout);
  if (status != SECSuccess)
    return false;

  CERTCertificate* root_ca =
      cvout[cvout_trust_anchor_index].value.pointer.cert;
  if (root_ca == NULL)
    return false;

  // This second PKIXVerifyCert call could have found a different certification
  // path and one or more of the certificates on this new path, that weren't on
  // the old path, might have been revoked.
  if (crl_set) {
    CRLSetResult crl_set_result = CheckRevocationWithCRLSet(
        cvout[cvout_cert_list_index].value.pointer.chain,
        cvout[cvout_trust_anchor_index].value.pointer.cert,
        crl_set);
    if (crl_set_result == kCRLSetRevoked)
      return false;
  }

#if defined(OS_IOS)
  SHA1HashValue fingerprint = x509_util_ios::CalculateFingerprintNSS(root_ca);
#else
  SHA1HashValue fingerprint =
      X509Certificate::CalculateFingerprint(root_ca);
#endif
  return metadata->HasEVPolicyOID(fingerprint, ev_policy_oid);
}

CERTCertList* CertificateListToCERTCertList(const CertificateList& list) {
  CERTCertList* result = CERT_NewCertList();
  for (size_t i = 0; i < list.size(); ++i) {
#if defined(OS_IOS)
    // X509Certificate::os_cert_handle() on iOS is a SecCertificateRef; convert
    // it to an NSS CERTCertificate.
    CERTCertificate* cert = x509_util_ios::CreateNSSCertHandleFromOSHandle(
        list[i]->os_cert_handle());
#else
    CERTCertificate* cert = list[i]->os_cert_handle();
#endif
    CERT_AddCertToListTail(result, CERT_DupCertificate(cert));
  }
  return result;
}

}  // namespace

CertVerifyProcNSS::CertVerifyProcNSS() {}

CertVerifyProcNSS::~CertVerifyProcNSS() {}

bool CertVerifyProcNSS::SupportsAdditionalTrustAnchors() const {
  // This requires APIs introduced in 3.14.2.
  return NSS_VersionCheck("3.14.2");
}

int CertVerifyProcNSS::VerifyInternal(
    X509Certificate* cert,
    const std::string& hostname,
    int flags,
    CRLSet* crl_set,
    const CertificateList& additional_trust_anchors,
    CertVerifyResult* verify_result) {
#if defined(OS_IOS)
  // For iOS, the entire chain must be loaded into NSS's in-memory certificate
  // store.
  x509_util_ios::NSSCertChain scoped_chain(cert);
  CERTCertificate* cert_handle = scoped_chain.cert_handle();
#else
  CERTCertificate* cert_handle = cert->os_cert_handle();
#endif  // defined(OS_IOS)

  // Make sure that the hostname matches with the common name of the cert.
  SECStatus status = CERT_VerifyCertName(cert_handle, hostname.c_str());
  if (status != SECSuccess)
    verify_result->cert_status |= CERT_STATUS_COMMON_NAME_INVALID;

  // Make sure that the cert is valid now.
  SECCertTimeValidity validity = CERT_CheckCertValidTimes(
      cert_handle, PR_Now(), PR_TRUE);
  if (validity != secCertTimeValid)
    verify_result->cert_status |= CERT_STATUS_DATE_INVALID;

  CERTValOutParam cvout[3];
  int cvout_index = 0;
  cvout[cvout_index].type = cert_po_certList;
  cvout[cvout_index].value.pointer.chain = NULL;
  int cvout_cert_list_index = cvout_index;
  cvout_index++;
  cvout[cvout_index].type = cert_po_trustAnchor;
  cvout[cvout_index].value.pointer.cert = NULL;
  int cvout_trust_anchor_index = cvout_index;
  cvout_index++;
  cvout[cvout_index].type = cert_po_end;
  ScopedCERTValOutParam scoped_cvout(cvout);

  EVRootCAMetadata* metadata = EVRootCAMetadata::GetInstance();
  SECOidTag ev_policy_oid = SEC_OID_UNKNOWN;
  bool is_ev_candidate =
      (flags & CertVerifier::VERIFY_EV_CERT) &&
      IsEVCandidate(metadata, cert_handle, &ev_policy_oid);
  bool cert_io_enabled = flags & CertVerifier::VERIFY_CERT_IO_ENABLED;
  bool check_revocation =
      cert_io_enabled &&
      ((flags & CertVerifier::VERIFY_REV_CHECKING_ENABLED) ||
       ((flags & CertVerifier::VERIFY_REV_CHECKING_ENABLED_EV_ONLY) &&
        is_ev_candidate));
  if (check_revocation)
    verify_result->cert_status |= CERT_STATUS_REV_CHECKING_ENABLED;

  ScopedCERTCertList trust_anchors;
  if (SupportsAdditionalTrustAnchors() && !additional_trust_anchors.empty()) {
    trust_anchors.reset(
        CertificateListToCERTCertList(additional_trust_anchors));
  }

  status = PKIXVerifyCert(cert_handle, check_revocation, cert_io_enabled,
                          NULL, 0, trust_anchors.get(), cvout);

  if (status == SECSuccess) {
    AppendPublicKeyHashes(cvout[cvout_cert_list_index].value.pointer.chain,
                          cvout[cvout_trust_anchor_index].value.pointer.cert,
                          &verify_result->public_key_hashes);

    verify_result->is_issued_by_known_root =
        IsKnownRoot(cvout[cvout_trust_anchor_index].value.pointer.cert);
    verify_result->is_issued_by_additional_trust_anchor =
        IsAdditionalTrustAnchor(
            trust_anchors.get(),
            cvout[cvout_trust_anchor_index].value.pointer.cert);

    GetCertChainInfo(cvout[cvout_cert_list_index].value.pointer.chain,
                     cvout[cvout_trust_anchor_index].value.pointer.cert,
                     verify_result);
  }

  if (crl_set) {
    CRLSetResult crl_set_result = CheckRevocationWithCRLSet(
        cvout[cvout_cert_list_index].value.pointer.chain,
        cvout[cvout_trust_anchor_index].value.pointer.cert,
        crl_set);
    if (crl_set_result == kCRLSetRevoked) {
      PORT_SetError(SEC_ERROR_REVOKED_CERTIFICATE);
      status = SECFailure;
    }
  }

  if (status != SECSuccess) {
    int err = PORT_GetError();
    LOG(ERROR) << "CERT_PKIXVerifyCert for " << hostname
               << " failed err=" << err;
    // CERT_PKIXVerifyCert rerports the wrong error code for
    // expired certificates (NSS bug 491174)
    if (err == SEC_ERROR_CERT_NOT_VALID &&
        (verify_result->cert_status & CERT_STATUS_DATE_INVALID))
      err = SEC_ERROR_EXPIRED_CERTIFICATE;
    CertStatus cert_status = MapCertErrorToCertStatus(err);
    if (cert_status) {
      verify_result->cert_status |= cert_status;
      return MapCertStatusToNetError(verify_result->cert_status);
    }
    // |err| is not a certificate error.
    return MapSecurityError(err);
  }

  if (IsCertStatusError(verify_result->cert_status))
    return MapCertStatusToNetError(verify_result->cert_status);

  if ((flags & CertVerifier::VERIFY_EV_CERT) && is_ev_candidate &&
      VerifyEV(cert_handle, flags, crl_set, metadata, ev_policy_oid,
               trust_anchors.get())) {
    verify_result->cert_status |= CERT_STATUS_IS_EV;
  }

  return OK;
}

}  // namespace net