// 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.h"

#include "base/metrics/histogram.h"
#include "base/sha1.h"
#include "base/strings/stringprintf.h"
#include "build/build_config.h"
#include "net/base/net_errors.h"
#include "net/base/net_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/x509_certificate.h"

#if defined(USE_NSS) || defined(OS_IOS)
#include "net/cert/cert_verify_proc_nss.h"
#elif defined(USE_OPENSSL) && !defined(OS_ANDROID)
#include "net/cert/cert_verify_proc_openssl.h"
#elif defined(OS_ANDROID)
#include "net/cert/cert_verify_proc_android.h"
#elif defined(OS_MACOSX)
#include "net/cert/cert_verify_proc_mac.h"
#elif defined(OS_WIN)
#include "net/cert/cert_verify_proc_win.h"
#else
#error Implement certificate verification.
#endif


namespace net {

namespace {

// Constants used to build histogram names
const char kLeafCert[] = "Leaf";
const char kIntermediateCert[] = "Intermediate";
const char kRootCert[] = "Root";
// Matches the order of X509Certificate::PublicKeyType
const char* const kCertTypeStrings[] = {
    "Unknown",
    "RSA",
    "DSA",
    "ECDSA",
    "DH",
    "ECDH"
};
// Histogram buckets for RSA/DSA/DH key sizes.
const int kRsaDsaKeySizes[] = {512, 768, 1024, 1536, 2048, 3072, 4096, 8192,
                               16384};
// Histogram buckets for ECDSA/ECDH key sizes. The list is based upon the FIPS
// 186-4 approved curves.
const int kEccKeySizes[] = {163, 192, 224, 233, 256, 283, 384, 409, 521, 571};

const char* CertTypeToString(int cert_type) {
  if (cert_type < 0 ||
      static_cast<size_t>(cert_type) >= arraysize(kCertTypeStrings)) {
    return "Unsupported";
  }
  return kCertTypeStrings[cert_type];
}

void RecordPublicKeyHistogram(const char* chain_position,
                              bool baseline_keysize_applies,
                              size_t size_bits,
                              X509Certificate::PublicKeyType cert_type) {
  std::string histogram_name =
      base::StringPrintf("CertificateType2.%s.%s.%s",
                         baseline_keysize_applies ? "BR" : "NonBR",
                         chain_position,
                         CertTypeToString(cert_type));
  // Do not use UMA_HISTOGRAM_... macros here, as it caches the Histogram
  // instance and thus only works if |histogram_name| is constant.
  base::HistogramBase* counter = NULL;

  // Histogram buckets are contingent upon the underlying algorithm being used.
  if (cert_type == X509Certificate::kPublicKeyTypeECDH ||
      cert_type == X509Certificate::kPublicKeyTypeECDSA) {
    // Typical key sizes match SECP/FIPS 186-3 recommendations for prime and
    // binary curves - which range from 163 bits to 571 bits.
    counter = base::CustomHistogram::FactoryGet(
        histogram_name,
        base::CustomHistogram::ArrayToCustomRanges(kEccKeySizes,
                                                   arraysize(kEccKeySizes)),
        base::HistogramBase::kUmaTargetedHistogramFlag);
  } else {
    // Key sizes < 1024 bits should cause errors, while key sizes > 16K are not
    // uniformly supported by the underlying cryptographic libraries.
    counter = base::CustomHistogram::FactoryGet(
        histogram_name,
        base::CustomHistogram::ArrayToCustomRanges(kRsaDsaKeySizes,
                                                   arraysize(kRsaDsaKeySizes)),
        base::HistogramBase::kUmaTargetedHistogramFlag);
  }
  counter->Add(size_bits);
}

// Returns true if |type| is |kPublicKeyTypeRSA| or |kPublicKeyTypeDSA|, and
// if |size_bits| is < 1024. Note that this means there may be false
// negatives: keys for other algorithms and which are weak will pass this
// test.
bool IsWeakKey(X509Certificate::PublicKeyType type, size_t size_bits) {
  switch (type) {
    case X509Certificate::kPublicKeyTypeRSA:
    case X509Certificate::kPublicKeyTypeDSA:
      return size_bits < 1024;
    default:
      return false;
  }
}

// Returns true if |cert| contains a known-weak key. Additionally, histograms
// the observed keys for future tightening of the definition of what
// constitutes a weak key.
bool ExaminePublicKeys(const scoped_refptr<X509Certificate>& cert,
                       bool should_histogram) {
  // The effective date of the CA/Browser Forum's Baseline Requirements -
  // 2012-07-01 00:00:00 UTC.
  const base::Time kBaselineEffectiveDate =
      base::Time::FromInternalValue(GG_INT64_C(12985574400000000));
  // The effective date of the key size requirements from Appendix A, v1.1.5
  // 2014-01-01 00:00:00 UTC.
  const base::Time kBaselineKeysizeEffectiveDate =
      base::Time::FromInternalValue(GG_INT64_C(13033008000000000));

  size_t size_bits = 0;
  X509Certificate::PublicKeyType type = X509Certificate::kPublicKeyTypeUnknown;
  bool weak_key = false;
  bool baseline_keysize_applies =
      cert->valid_start() >= kBaselineEffectiveDate &&
      cert->valid_expiry() >= kBaselineKeysizeEffectiveDate;

  X509Certificate::GetPublicKeyInfo(cert->os_cert_handle(), &size_bits, &type);
  if (should_histogram) {
    RecordPublicKeyHistogram(kLeafCert, baseline_keysize_applies, size_bits,
                             type);
  }
  if (IsWeakKey(type, size_bits))
    weak_key = true;

  const X509Certificate::OSCertHandles& intermediates =
      cert->GetIntermediateCertificates();
  for (size_t i = 0; i < intermediates.size(); ++i) {
    X509Certificate::GetPublicKeyInfo(intermediates[i], &size_bits, &type);
    if (should_histogram) {
      RecordPublicKeyHistogram(
          (i < intermediates.size() - 1) ? kIntermediateCert : kRootCert,
          baseline_keysize_applies,
          size_bits,
          type);
    }
    if (!weak_key && IsWeakKey(type, size_bits))
      weak_key = true;
  }

  return weak_key;
}

}  // namespace

// static
CertVerifyProc* CertVerifyProc::CreateDefault() {
#if defined(USE_NSS) || defined(OS_IOS)
  return new CertVerifyProcNSS();
#elif defined(USE_OPENSSL) && !defined(OS_ANDROID)
  return new CertVerifyProcOpenSSL();
#elif defined(OS_ANDROID)
  return new CertVerifyProcAndroid();
#elif defined(OS_MACOSX)
  return new CertVerifyProcMac();
#elif defined(OS_WIN)
  return new CertVerifyProcWin();
#else
  return NULL;
#endif
}

CertVerifyProc::CertVerifyProc() {}

CertVerifyProc::~CertVerifyProc() {}

int CertVerifyProc::Verify(X509Certificate* cert,
                           const std::string& hostname,
                           int flags,
                           CRLSet* crl_set,
                           const CertificateList& additional_trust_anchors,
                           CertVerifyResult* verify_result) {
  verify_result->Reset();
  verify_result->verified_cert = cert;

  if (IsBlacklisted(cert)) {
    verify_result->cert_status |= CERT_STATUS_REVOKED;
    return ERR_CERT_REVOKED;
  }

  // We do online revocation checking for EV certificates that aren't covered
  // by a fresh CRLSet.
  // TODO(rsleevi): http://crbug.com/142974 - Allow preferences to fully
  // disable revocation checking.
  if (flags & CertVerifier::VERIFY_EV_CERT)
    flags |= CertVerifier::VERIFY_REV_CHECKING_ENABLED_EV_ONLY;

  int rv = VerifyInternal(cert, hostname, flags, crl_set,
                          additional_trust_anchors, verify_result);

  // This check is done after VerifyInternal so that VerifyInternal can fill
  // in the list of public key hashes.
  if (IsPublicKeyBlacklisted(verify_result->public_key_hashes)) {
    verify_result->cert_status |= CERT_STATUS_REVOKED;
    rv = MapCertStatusToNetError(verify_result->cert_status);
  }

  // Check for weak keys in the entire verified chain.
  bool weak_key = ExaminePublicKeys(verify_result->verified_cert,
                                    verify_result->is_issued_by_known_root);

  if (weak_key) {
    verify_result->cert_status |= CERT_STATUS_WEAK_KEY;
    // Avoid replacing a more serious error, such as an OS/library failure,
    // by ensuring that if verification failed, it failed with a certificate
    // error.
    if (rv == OK || IsCertificateError(rv))
      rv = MapCertStatusToNetError(verify_result->cert_status);
  }

  // Treat certificates signed using broken signature algorithms as invalid.
  if (verify_result->has_md2 || verify_result->has_md4) {
    verify_result->cert_status |= CERT_STATUS_INVALID;
    rv = MapCertStatusToNetError(verify_result->cert_status);
  }

  // Flag certificates using weak signature algorithms.
  if (verify_result->has_md5) {
    verify_result->cert_status |= CERT_STATUS_WEAK_SIGNATURE_ALGORITHM;
    // Avoid replacing a more serious error, such as an OS/library failure,
    // by ensuring that if verification failed, it failed with a certificate
    // error.
    if (rv == OK || IsCertificateError(rv))
      rv = MapCertStatusToNetError(verify_result->cert_status);
  }

#if !defined(OS_ANDROID)
  // Flag certificates from publicly-trusted CAs that are issued to intranet
  // hosts. While the CA/Browser Forum Baseline Requirements (v1.1) permit
  // these to be issued until 1 November 2015, they represent a real risk for
  // the deployment of gTLDs and are being phased out ahead of the hard
  // deadline.
  //
  // TODO(ppi): is_issued_by_known_root is incorrect on Android. Once this is
  // fixed, re-enable this check for Android. crbug.com/116838
  if (verify_result->is_issued_by_known_root && IsHostnameNonUnique(hostname)) {
    verify_result->cert_status |= CERT_STATUS_NON_UNIQUE_NAME;
  }
#endif

  return rv;
}

// static
bool CertVerifyProc::IsBlacklisted(X509Certificate* cert) {
  static const unsigned kComodoSerialBytes = 16;
  static const uint8 kComodoSerials[][kComodoSerialBytes] = {
    // Not a real certificate. For testing only.
    {0x07,0x7a,0x59,0xbc,0xd5,0x34,0x59,0x60,0x1c,0xa6,0x90,0x72,0x67,0xa6,0xdd,0x1c},

    // The next nine certificates all expire on Fri Mar 14 23:59:59 2014.
    // Some serial numbers actually have a leading 0x00 byte required to
    // encode a positive integer in DER if the most significant bit is 0.
    // We omit the leading 0x00 bytes to make all serial numbers 16 bytes.

    // Subject: CN=mail.google.com
    // subjectAltName dNSName: mail.google.com, www.mail.google.com
    {0x04,0x7e,0xcb,0xe9,0xfc,0xa5,0x5f,0x7b,0xd0,0x9e,0xae,0x36,0xe1,0x0c,0xae,0x1e},
    // Subject: CN=global trustee
    // subjectAltName dNSName: global trustee
    // Note: not a CA certificate.
    {0xd8,0xf3,0x5f,0x4e,0xb7,0x87,0x2b,0x2d,0xab,0x06,0x92,0xe3,0x15,0x38,0x2f,0xb0},
    // Subject: CN=login.live.com
    // subjectAltName dNSName: login.live.com, www.login.live.com
    {0xb0,0xb7,0x13,0x3e,0xd0,0x96,0xf9,0xb5,0x6f,0xae,0x91,0xc8,0x74,0xbd,0x3a,0xc0},
    // Subject: CN=addons.mozilla.org
    // subjectAltName dNSName: addons.mozilla.org, www.addons.mozilla.org
    {0x92,0x39,0xd5,0x34,0x8f,0x40,0xd1,0x69,0x5a,0x74,0x54,0x70,0xe1,0xf2,0x3f,0x43},
    // Subject: CN=login.skype.com
    // subjectAltName dNSName: login.skype.com, www.login.skype.com
    {0xe9,0x02,0x8b,0x95,0x78,0xe4,0x15,0xdc,0x1a,0x71,0x0a,0x2b,0x88,0x15,0x44,0x47},
    // Subject: CN=login.yahoo.com
    // subjectAltName dNSName: login.yahoo.com, www.login.yahoo.com
    {0xd7,0x55,0x8f,0xda,0xf5,0xf1,0x10,0x5b,0xb2,0x13,0x28,0x2b,0x70,0x77,0x29,0xa3},
    // Subject: CN=www.google.com
    // subjectAltName dNSName: www.google.com, google.com
    {0xf5,0xc8,0x6a,0xf3,0x61,0x62,0xf1,0x3a,0x64,0xf5,0x4f,0x6d,0xc9,0x58,0x7c,0x06},
    // Subject: CN=login.yahoo.com
    // subjectAltName dNSName: login.yahoo.com
    {0x39,0x2a,0x43,0x4f,0x0e,0x07,0xdf,0x1f,0x8a,0xa3,0x05,0xde,0x34,0xe0,0xc2,0x29},
    // Subject: CN=login.yahoo.com
    // subjectAltName dNSName: login.yahoo.com
    {0x3e,0x75,0xce,0xd4,0x6b,0x69,0x30,0x21,0x21,0x88,0x30,0xae,0x86,0xa8,0x2a,0x71},
  };

  const std::string& serial_number = cert->serial_number();
  if (!serial_number.empty() && (serial_number[0] & 0x80) != 0) {
    // This is a negative serial number, which isn't technically allowed but
    // which probably happens. In order to avoid confusing a negative serial
    // number with a positive one once the leading zeros have been removed, we
    // disregard it.
    return false;
  }

  base::StringPiece serial(serial_number);
  // Remove leading zeros.
  while (serial.size() > 1 && serial[0] == 0)
    serial.remove_prefix(1);

  if (serial.size() == kComodoSerialBytes) {
    for (unsigned i = 0; i < arraysize(kComodoSerials); i++) {
      if (memcmp(kComodoSerials[i], serial.data(), kComodoSerialBytes) == 0) {
        UMA_HISTOGRAM_ENUMERATION("Net.SSLCertBlacklisted", i,
                                  arraysize(kComodoSerials) + 1);
        return true;
      }
    }
  }

  return false;
}

// static
// NOTE: This implementation assumes and enforces that the hashes are SHA1.
bool CertVerifyProc::IsPublicKeyBlacklisted(
    const HashValueVector& public_key_hashes) {
  static const unsigned kNumHashes = 10;
  static const uint8 kHashes[kNumHashes][base::kSHA1Length] = {
    // Subject: CN=DigiNotar Root CA
    // Issuer: CN=Entrust.net x2 and self-signed
    {0x41, 0x0f, 0x36, 0x36, 0x32, 0x58, 0xf3, 0x0b, 0x34, 0x7d,
     0x12, 0xce, 0x48, 0x63, 0xe4, 0x33, 0x43, 0x78, 0x06, 0xa8},
    // Subject: CN=DigiNotar Cyber CA
    // Issuer: CN=GTE CyberTrust Global Root
    {0xc4, 0xf9, 0x66, 0x37, 0x16, 0xcd, 0x5e, 0x71, 0xd6, 0x95,
     0x0b, 0x5f, 0x33, 0xce, 0x04, 0x1c, 0x95, 0xb4, 0x35, 0xd1},
    // Subject: CN=DigiNotar Services 1024 CA
    // Issuer: CN=Entrust.net
    {0xe2, 0x3b, 0x8d, 0x10, 0x5f, 0x87, 0x71, 0x0a, 0x68, 0xd9,
     0x24, 0x80, 0x50, 0xeb, 0xef, 0xc6, 0x27, 0xbe, 0x4c, 0xa6},
    // Subject: CN=DigiNotar PKIoverheid CA Organisatie - G2
    // Issuer: CN=Staat der Nederlanden Organisatie CA - G2
    {0x7b, 0x2e, 0x16, 0xbc, 0x39, 0xbc, 0xd7, 0x2b, 0x45, 0x6e,
     0x9f, 0x05, 0x5d, 0x1d, 0xe6, 0x15, 0xb7, 0x49, 0x45, 0xdb},
    // Subject: CN=DigiNotar PKIoverheid CA Overheid en Bedrijven
    // Issuer: CN=Staat der Nederlanden Overheid CA
    {0xe8, 0xf9, 0x12, 0x00, 0xc6, 0x5c, 0xee, 0x16, 0xe0, 0x39,
     0xb9, 0xf8, 0x83, 0x84, 0x16, 0x61, 0x63, 0x5f, 0x81, 0xc5},
    // Subject: O=Digicert Sdn. Bhd.
    // Issuer: CN=GTE CyberTrust Global Root
    // Expires: Jul 17 15:16:54 2012 GMT
    {0x01, 0x29, 0xbc, 0xd5, 0xb4, 0x48, 0xae, 0x8d, 0x24, 0x96,
     0xd1, 0xc3, 0xe1, 0x97, 0x23, 0x91, 0x90, 0x88, 0xe1, 0x52},
    // Subject: O=Digicert Sdn. Bhd.
    // Issuer: CN=Entrust.net Certification Authority (2048)
    // Expires: Jul 16 17:53:37 2015 GMT
    {0xd3, 0x3c, 0x5b, 0x41, 0xe4, 0x5c, 0xc4, 0xb3, 0xbe, 0x9a,
     0xd6, 0x95, 0x2c, 0x4e, 0xcc, 0x25, 0x28, 0x03, 0x29, 0x81},
    // Issuer: CN=Trustwave Organization Issuing CA, Level 2
    // Covers two certificates, the latter of which expires Apr 15 21:09:30
    // 2021 GMT.
    {0xe1, 0x2d, 0x89, 0xf5, 0x6d, 0x22, 0x76, 0xf8, 0x30, 0xe6,
     0xce, 0xaf, 0xa6, 0x6c, 0x72, 0x5c, 0x0b, 0x41, 0xa9, 0x32},
    // Cyberoam CA certificate. Private key leaked, but this certificate would
    // only have been installed by Cyberoam customers. The certificate expires
    // in 2036, but we can probably remove in a couple of years (2014).
    {0xd9, 0xf5, 0xc6, 0xce, 0x57, 0xff, 0xaa, 0x39, 0xcc, 0x7e,
     0xd1, 0x72, 0xbd, 0x53, 0xe0, 0xd3, 0x07, 0x83, 0x4b, 0xd1},
    // Win32/Sirefef.gen!C generates fake certifciates with this public key.
    {0xa4, 0xf5, 0x6e, 0x9e, 0x1d, 0x9a, 0x3b, 0x7b, 0x1a, 0xc3,
     0x31, 0xcf, 0x64, 0xfc, 0x76, 0x2c, 0xd0, 0x51, 0xfb, 0xa4},
  };

  for (unsigned i = 0; i < kNumHashes; i++) {
    for (HashValueVector::const_iterator j = public_key_hashes.begin();
         j != public_key_hashes.end(); ++j) {
      if (j->tag == HASH_VALUE_SHA1 &&
          memcmp(j->data(), kHashes[i], base::kSHA1Length) == 0) {
        return true;
      }
    }
  }

  return false;
}

}  // namespace net