net/cert/x509_certificate.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/x509_certificate.h"

#include <limits.h>
#include <stdlib.h>

#include <memory>
#include <string>
#include <vector>

#include "base/base64.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/numerics/safe_conversions.h"
#include "base/pickle.h"
#include "base/stl_util.h"
#include "base/strings/string_piece.h"
#include "base/strings/string_util.h"
#include "base/time/time.h"
#include "base/trace_event/trace_event.h"
#include "build/build_config.h"
#include "crypto/openssl_util.h"
#include "net/base/ip_address.h"
#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
#include "net/base/url_util.h"
#include "net/cert/asn1_util.h"
#include "net/cert/internal/cert_errors.h"
#include "net/cert/internal/name_constraints.h"
#include "net/cert/internal/parsed_certificate.h"
#include "net/cert/internal/signature_algorithm.h"
#include "net/cert/internal/verify_name_match.h"
#include "net/cert/internal/verify_signed_data.h"
#include "net/cert/pem.h"
#include "net/cert/x509_util.h"
#include "net/der/encode_values.h"
#include "net/der/parser.h"
#include "net/dns/dns_util.h"
#include "third_party/boringssl/src/include/openssl/evp.h"
#include "third_party/boringssl/src/include/openssl/pkcs7.h"
#include "third_party/boringssl/src/include/openssl/pool.h"
#include "third_party/boringssl/src/include/openssl/sha.h"
#include "url/url_canon.h"

namespace net {

namespace {

// Indicates the order to use when trying to decode binary data, which is
// based on (speculation) as to what will be most common -> least common
const X509Certificate::Format kFormatDecodePriority[] = {
  X509Certificate::FORMAT_SINGLE_CERTIFICATE,
  X509Certificate::FORMAT_PKCS7
};

// The PEM block header used for DER certificates
const char kCertificateHeader[] = "CERTIFICATE";
// The PEM block header used for PKCS#7 data
const char kPKCS7Header[] = "PKCS7";

// Utility to split |src| on the first occurrence of |c|, if any. |right| will
// either be empty if |c| was not found, or will contain the remainder of the
// string including the split character itself.
void SplitOnChar(const base::StringPiece& src,
                 char c,
                 base::StringPiece* left,
                 base::StringPiece* right) {
  size_t pos = src.find(c);
  if (pos == base::StringPiece::npos) {
    *left = src;
    *right = base::StringPiece();
  } else {
    *left = src.substr(0, pos);
    *right = src.substr(pos);
  }
}

// Sets |value| to the Value from a DER Sequence Tag-Length-Value and return
// true, or return false if the TLV was not a valid DER Sequence.
WARN_UNUSED_RESULT bool ParseSequenceValue(const der::Input& tlv,
                                           der::Input* value) {
  der::Parser parser(tlv);
  return parser.ReadTag(der::kSequence, value) && !parser.HasMore();
}

// Normalize |cert|'s Issuer and store it in |out_normalized_issuer|, returning
// true on success or false if there was a parsing error.
bool GetNormalizedCertIssuer(CRYPTO_BUFFER* cert,
                             std::string* out_normalized_issuer) {
  der::Input tbs_certificate_tlv;
  der::Input signature_algorithm_tlv;
  der::BitString signature_value;
  if (!ParseCertificate(
          der::Input(CRYPTO_BUFFER_data(cert), CRYPTO_BUFFER_len(cert)),
          &tbs_certificate_tlv, &signature_algorithm_tlv, &signature_value,
          nullptr)) {
    return false;
  }
  ParsedTbsCertificate tbs;
  if (!ParseTbsCertificate(tbs_certificate_tlv,
                           x509_util::DefaultParseCertificateOptions(), &tbs,
                           nullptr))
    return false;

  der::Input issuer_value;
  if (!ParseSequenceValue(tbs.issuer_tlv, &issuer_value))
    return false;

  CertErrors errors;
  return NormalizeName(issuer_value, out_normalized_issuer, &errors);
}

// Parses certificates from a PKCS#7 SignedData structure, appending them to
// |handles|.
void CreateCertBuffersFromPKCS7Bytes(
    const char* data,
    size_t length,
    std::vector<bssl::UniquePtr<CRYPTO_BUFFER>>* handles) {
  crypto::EnsureOpenSSLInit();
  crypto::OpenSSLErrStackTracer err_cleaner(FROM_HERE);

  CBS der_data;
  CBS_init(&der_data, reinterpret_cast<const uint8_t*>(data), length);
  STACK_OF(CRYPTO_BUFFER)* certs = sk_CRYPTO_BUFFER_new_null();

  if (PKCS7_get_raw_certificates(certs, &der_data,
                                 x509_util::GetBufferPool())) {
    for (size_t i = 0; i < sk_CRYPTO_BUFFER_num(certs); ++i) {
      handles->push_back(
          bssl::UniquePtr<CRYPTO_BUFFER>(sk_CRYPTO_BUFFER_value(certs, i)));
    }
  }
  // |handles| took ownership of the individual buffers, so only free the list
  // itself.
  sk_CRYPTO_BUFFER_free(certs);
}

}  // namespace

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromBuffer(
    bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer,
    std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediates) {
  DCHECK(cert_buffer);
  scoped_refptr<X509Certificate> cert(
      new X509Certificate(std::move(cert_buffer), std::move(intermediates)));
  if (!cert->cert_buffer())
    return nullptr;  // Initialize() failed.
  return cert;
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromBufferUnsafeOptions(
    bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer,
    std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediates,
    UnsafeCreateOptions options) {
  DCHECK(cert_buffer);
  scoped_refptr<X509Certificate> cert(new X509Certificate(
      std::move(cert_buffer), std::move(intermediates), options));
  if (!cert->cert_buffer())
    return nullptr;  // Initialize() failed.
  return cert;
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromDERCertChain(
    const std::vector<base::StringPiece>& der_certs) {
  return CreateFromDERCertChainUnsafeOptions(der_certs, {});
}

// static
scoped_refptr<X509Certificate>
X509Certificate::CreateFromDERCertChainUnsafeOptions(
    const std::vector<base::StringPiece>& der_certs,
    UnsafeCreateOptions options) {
  TRACE_EVENT0("io", "X509Certificate::CreateFromDERCertChain");
  if (der_certs.empty())
    return nullptr;

  std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediate_ca_certs;
  intermediate_ca_certs.reserve(der_certs.size() - 1);
  for (size_t i = 1; i < der_certs.size(); i++) {
    bssl::UniquePtr<CRYPTO_BUFFER> handle = CreateCertBufferFromBytes(
        const_cast<char*>(der_certs[i].data()), der_certs[i].size());
    if (!handle)
      break;
    intermediate_ca_certs.push_back(std::move(handle));
  }

  // Return NULL if we failed to parse any of the certs.
  if (der_certs.size() - 1 != intermediate_ca_certs.size())
    return nullptr;

  bssl::UniquePtr<CRYPTO_BUFFER> handle = CreateCertBufferFromBytes(
      const_cast<char*>(der_certs[0].data()), der_certs[0].size());
  if (!handle)
    return nullptr;

  return CreateFromBufferUnsafeOptions(
      std::move(handle), std::move(intermediate_ca_certs), options);
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromBytes(
    const char* data,
    size_t length) {
  return CreateFromBytesUnsafeOptions(data, length, {});
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromBytesUnsafeOptions(
    const char* data,
    size_t length,
    UnsafeCreateOptions options) {
  bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer =
      CreateCertBufferFromBytes(data, length);
  if (!cert_buffer)
    return nullptr;

  scoped_refptr<X509Certificate> cert =
      CreateFromBufferUnsafeOptions(std::move(cert_buffer), {}, options);
  return cert;
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromPickle(
    base::PickleIterator* pickle_iter) {
  return CreateFromPickleUnsafeOptions(pickle_iter, {});
}

// static
scoped_refptr<X509Certificate> X509Certificate::CreateFromPickleUnsafeOptions(
    base::PickleIterator* pickle_iter,
    UnsafeCreateOptions options) {
  int chain_length = 0;
  if (!pickle_iter->ReadLength(&chain_length))
    return nullptr;

  std::vector<base::StringPiece> cert_chain;
  const char* data = nullptr;
  int data_length = 0;
  for (int i = 0; i < chain_length; ++i) {
    if (!pickle_iter->ReadData(&data, &data_length))
      return nullptr;
    cert_chain.push_back(base::StringPiece(data, data_length));
  }
  return CreateFromDERCertChainUnsafeOptions(cert_chain, options);
}

// static
CertificateList X509Certificate::CreateCertificateListFromBytes(
    const char* data,
    size_t length,
    int format) {
  std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> certificates;

  // Check to see if it is in a PEM-encoded form. This check is performed
  // first, as both OS X and NSS will both try to convert if they detect
  // PEM encoding, except they don't do it consistently between the two.
  base::StringPiece data_string(data, length);
  std::vector<std::string> pem_headers;

  // To maintain compatibility with NSS/Firefox, CERTIFICATE is a universally
  // valid PEM block header for any format.
  pem_headers.push_back(kCertificateHeader);
  if (format & FORMAT_PKCS7)
    pem_headers.push_back(kPKCS7Header);

  PEMTokenizer pem_tokenizer(data_string, pem_headers);
  while (pem_tokenizer.GetNext()) {
    std::string decoded(pem_tokenizer.data());

    bssl::UniquePtr<CRYPTO_BUFFER> handle;
    if (format & FORMAT_PEM_CERT_SEQUENCE)
      handle = CreateCertBufferFromBytes(decoded.c_str(), decoded.size());
    if (handle) {
      // Parsed a DER encoded certificate. All PEM blocks that follow must
      // also be DER encoded certificates wrapped inside of PEM blocks.
      format = FORMAT_PEM_CERT_SEQUENCE;
      certificates.push_back(std::move(handle));
      continue;
    }

    // If the first block failed to parse as a DER certificate, and
    // formats other than PEM are acceptable, check to see if the decoded
    // data is one of the accepted formats.
    if (format & ~FORMAT_PEM_CERT_SEQUENCE) {
      for (size_t i = 0;
           certificates.empty() && i < base::size(kFormatDecodePriority); ++i) {
        if (format & kFormatDecodePriority[i]) {
          certificates = CreateCertBuffersFromBytes(
              decoded.c_str(), decoded.size(), kFormatDecodePriority[i]);
        }
      }
    }

    // Stop parsing after the first block for any format but a sequence of
    // PEM-encoded DER certificates. The case of FORMAT_PEM_CERT_SEQUENCE
    // is handled above, and continues processing until a certificate fails
    // to parse.
    break;
  }

  // Try each of the formats, in order of parse preference, to see if |data|
  // contains the binary representation of a Format, if it failed to parse
  // as a PEM certificate/chain.
  for (size_t i = 0;
       certificates.empty() && i < base::size(kFormatDecodePriority); ++i) {
    if (format & kFormatDecodePriority[i])
      certificates =
          CreateCertBuffersFromBytes(data, length, kFormatDecodePriority[i]);
  }

  CertificateList results;
  // No certificates parsed.
  if (certificates.empty())
    return results;

  for (auto& it : certificates) {
    scoped_refptr<X509Certificate> cert = CreateFromBuffer(std::move(it), {});
    if (cert)
      results.push_back(std::move(cert));
  }

  return results;
}

void X509Certificate::Persist(base::Pickle* pickle) const {
  DCHECK(cert_buffer_);
  // This would be an absolutely insane number of intermediates.
  if (intermediate_ca_certs_.size() > static_cast<size_t>(INT_MAX) - 1) {
    NOTREACHED();
    return;
  }
  pickle->WriteInt(static_cast<int>(intermediate_ca_certs_.size() + 1));
  pickle->WriteString(x509_util::CryptoBufferAsStringPiece(cert_buffer_.get()));
  for (const auto& intermediate : intermediate_ca_certs_) {
    pickle->WriteString(
        x509_util::CryptoBufferAsStringPiece(intermediate.get()));
  }
}

bool X509Certificate::GetSubjectAltName(
    std::vector<std::string>* dns_names,
    std::vector<std::string>* ip_addrs) const {
  if (dns_names)
    dns_names->clear();
  if (ip_addrs)
    ip_addrs->clear();

  der::Input tbs_certificate_tlv;
  der::Input signature_algorithm_tlv;
  der::BitString signature_value;
  if (!ParseCertificate(der::Input(CRYPTO_BUFFER_data(cert_buffer_.get()),
                                   CRYPTO_BUFFER_len(cert_buffer_.get())),
                        &tbs_certificate_tlv, &signature_algorithm_tlv,
                        &signature_value, nullptr)) {
    return false;
  }

  ParsedTbsCertificate tbs;
  if (!ParseTbsCertificate(tbs_certificate_tlv,
                           x509_util::DefaultParseCertificateOptions(), &tbs,
                           nullptr))
    return false;
  if (!tbs.has_extensions)
    return false;

  std::map<der::Input, ParsedExtension> extensions;
  if (!ParseExtensions(tbs.extensions_tlv, &extensions))
    return false;

  ParsedExtension subject_alt_names_extension;
  if (!ConsumeExtension(SubjectAltNameOid(), &extensions,
                        &subject_alt_names_extension)) {
    return false;
  }

  CertErrors errors;
  std::unique_ptr<GeneralNames> subject_alt_names =
      GeneralNames::Create(subject_alt_names_extension.value, &errors);
  if (!subject_alt_names)
    return false;

  if (dns_names) {
    for (const auto& dns_name : subject_alt_names->dns_names)
      dns_names->push_back(dns_name.as_string());
  }
  if (ip_addrs) {
    for (const IPAddress& addr : subject_alt_names->ip_addresses) {
      ip_addrs->push_back(
          std::string(reinterpret_cast<const char*>(addr.bytes().data()),
                      addr.bytes().size()));
    }
  }

  return !subject_alt_names->dns_names.empty() ||
         !subject_alt_names->ip_addresses.empty();
}

bool X509Certificate::HasExpired() const {
  return base::Time::Now() > valid_expiry();
}

bool X509Certificate::EqualsExcludingChain(const X509Certificate* other) const {
  return x509_util::CryptoBufferEqual(cert_buffer_.get(),
                                      other->cert_buffer_.get());
}

bool X509Certificate::EqualsIncludingChain(const X509Certificate* other) const {
  if (intermediate_ca_certs_.size() != other->intermediate_ca_certs_.size() ||
      !EqualsExcludingChain(other)) {
    return false;
  }
  for (size_t i = 0; i < intermediate_ca_certs_.size(); ++i) {
    if (!x509_util::CryptoBufferEqual(intermediate_ca_certs_[i].get(),
                                      other->intermediate_ca_certs_[i].get())) {
      return false;
    }
  }
  return true;
}

bool X509Certificate::IsIssuedByEncoded(
    const std::vector<std::string>& valid_issuers) const {
  std::vector<std::string> normalized_issuers;
  CertErrors errors;
  for (const auto& raw_issuer : valid_issuers) {
    der::Input issuer_value;
    std::string normalized_issuer;
    if (!ParseSequenceValue(der::Input(&raw_issuer), &issuer_value) ||
        !NormalizeName(issuer_value, &normalized_issuer, &errors)) {
      continue;
    }
    normalized_issuers.push_back(std::move(normalized_issuer));
  }

  std::string normalized_cert_issuer;
  if (!GetNormalizedCertIssuer(cert_buffer_.get(), &normalized_cert_issuer))
    return false;
  if (base::Contains(normalized_issuers, normalized_cert_issuer))
    return true;

  for (const auto& intermediate : intermediate_ca_certs_) {
    if (!GetNormalizedCertIssuer(intermediate.get(), &normalized_cert_issuer))
      return false;
    if (base::Contains(normalized_issuers, normalized_cert_issuer))
      return true;
  }
  return false;
}

// static
bool X509Certificate::VerifyHostname(
    const std::string& hostname,
    const std::vector<std::string>& cert_san_dns_names,
    const std::vector<std::string>& cert_san_ip_addrs) {
  DCHECK(!hostname.empty());

  if (cert_san_dns_names.empty() && cert_san_ip_addrs.empty()) {
    // Either a dNSName or iPAddress subjectAltName MUST be present in order
    // to match, so fail quickly if not.
    return false;
  }

  // Perform name verification following http://tools.ietf.org/html/rfc6125.
  // The terminology used in this method is as per that RFC:-
  // Reference identifier == the host the local user/agent is intending to
  //                         access, i.e. the thing displayed in the URL bar.
  // Presented identifier(s) == name(s) the server knows itself as, in its cert.

  // CanonicalizeHost requires surrounding brackets to parse an IPv6 address.
  const std::string host_or_ip = hostname.find(':') != std::string::npos ?
      "[" + hostname + "]" : hostname;
  url::CanonHostInfo host_info;
  std::string reference_name = CanonicalizeHost(host_or_ip, &host_info);

  // If the host cannot be canonicalized, fail fast.
  if (reference_name.empty())
    return false;

  // Fully handle all cases where |hostname| contains an IP address.
  if (host_info.IsIPAddress()) {
    base::StringPiece ip_addr_string(
        reinterpret_cast<const char*>(host_info.address),
        host_info.AddressLength());
    return base::Contains(cert_san_ip_addrs, ip_addr_string);
  }

  // The host portion of a URL may support a variety of name resolution formats
  // and services. However, the only supported name types in this code are IP
  // addresses, which have been handled above via iPAddress subjectAltNames,
  // and DNS names, via dNSName subjectAltNames.
  // Validate that the host conforms to the DNS preferred name syntax, in
  // either relative or absolute form, and exclude the "root" label for DNS.
  if (reference_name == "." || !IsValidDNSDomain(reference_name))
    return false;

  // CanonicalizeHost does not normalize absolute vs relative DNS names. If
  // the input name was absolute (included trailing .), normalize it as if it
  // was relative.
  if (reference_name.back() == '.')
    reference_name.pop_back();

  // |reference_domain| is the remainder of |host| after the leading host
  // component is stripped off, but includes the leading dot e.g.
  // "www.f.com" -> ".f.com".
  // If there is no meaningful domain part to |host| (e.g. it contains no dots)
  // then |reference_domain| will be empty.
  base::StringPiece reference_host, reference_domain;
  SplitOnChar(reference_name, '.', &reference_host, &reference_domain);
  bool allow_wildcards = false;
  if (!reference_domain.empty()) {
    DCHECK(reference_domain.starts_with("."));

    // Do not allow wildcards for public/ICANN registry controlled domains -
    // that is, prevent *.com or *.co.uk as valid presented names, but do not
    // prevent *.appspot.com (a private registry controlled domain).
    // In addition, unknown top-level domains (such as 'intranet' domains or
    // new TLDs/gTLDs not yet added to the registry controlled domain dataset)
    // are also implicitly prevented.
    // Because |reference_domain| must contain at least one name component that
    // is not registry controlled, this ensures that all reference domains
    // contain at least three domain components when using wildcards.
    size_t registry_length =
        registry_controlled_domains::GetCanonicalHostRegistryLength(
            reference_name,
            registry_controlled_domains::INCLUDE_UNKNOWN_REGISTRIES,
            registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES);

    // Because |reference_name| was already canonicalized, the following
    // should never happen.
    CHECK_NE(std::string::npos, registry_length);

    // Account for the leading dot in |reference_domain|.
    bool is_registry_controlled =
        registry_length != 0 &&
        registry_length == (reference_domain.size() - 1);

    // Additionally, do not attempt wildcard matching for purely numeric
    // hostnames.
    allow_wildcards =
        !is_registry_controlled &&
        reference_name.find_first_not_of("0123456789.") != std::string::npos;
  }

  // Now step through the DNS names doing wild card comparison (if necessary)
  // on each against the reference name.
  for (const auto& cert_san_dns_name : cert_san_dns_names) {
    // Catch badly corrupt cert names up front.
    if (cert_san_dns_name.empty() ||
        cert_san_dns_name.find('\0') != std::string::npos) {
      DVLOG(1) << "Bad name in cert: " << cert_san_dns_name;
      continue;
    }
    std::string presented_name(base::ToLowerASCII(cert_san_dns_name));

    // Remove trailing dot, if any.
    if (*presented_name.rbegin() == '.')
      presented_name.resize(presented_name.length() - 1);

    // The hostname must be at least as long as the cert name it is matching,
    // as we require the wildcard (if present) to match at least one character.
    if (presented_name.length() > reference_name.length())
      continue;

    base::StringPiece presented_host, presented_domain;
    SplitOnChar(presented_name, '.', &presented_host, &presented_domain);

    if (presented_domain != reference_domain)
      continue;

    if (presented_host != "*") {
      if (presented_host == reference_host)
        return true;
      continue;
    }

    if (!allow_wildcards)
      continue;

    return true;
  }
  return false;
}

bool X509Certificate::VerifyNameMatch(const std::string& hostname) const {
  std::vector<std::string> dns_names, ip_addrs;
  GetSubjectAltName(&dns_names, &ip_addrs);
  return VerifyHostname(hostname, dns_names, ip_addrs);
}

// static
bool X509Certificate::GetPEMEncodedFromDER(base::StringPiece der_encoded,
                                           std::string* pem_encoded) {
  if (der_encoded.empty())
    return false;

  *pem_encoded = PEMEncode(der_encoded, "CERTIFICATE");
  return true;
}

// static
bool X509Certificate::GetPEMEncoded(const CRYPTO_BUFFER* cert_buffer,
                                    std::string* pem_encoded) {
  return GetPEMEncodedFromDER(x509_util::CryptoBufferAsStringPiece(cert_buffer),
                              pem_encoded);
}

bool X509Certificate::GetPEMEncodedChain(
    std::vector<std::string>* pem_encoded) const {
  std::vector<std::string> encoded_chain;
  std::string pem_data;
  if (!GetPEMEncoded(cert_buffer(), &pem_data))
    return false;
  encoded_chain.push_back(pem_data);
  for (size_t i = 0; i < intermediate_ca_certs_.size(); ++i) {
    if (!GetPEMEncoded(intermediate_ca_certs_[i].get(), &pem_data))
      return false;
    encoded_chain.push_back(pem_data);
  }
  pem_encoded->swap(encoded_chain);
  return true;
}

// static
void X509Certificate::GetPublicKeyInfo(const CRYPTO_BUFFER* cert_buffer,
                                       size_t* size_bits,
                                       PublicKeyType* type) {
  *type = kPublicKeyTypeUnknown;
  *size_bits = 0;

  base::StringPiece spki;
  if (!asn1::ExtractSPKIFromDERCert(
          base::StringPiece(
              reinterpret_cast<const char*>(CRYPTO_BUFFER_data(cert_buffer)),
              CRYPTO_BUFFER_len(cert_buffer)),
          &spki)) {
    return;
  }

  bssl::UniquePtr<EVP_PKEY> pkey;
  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  CBS cbs;
  CBS_init(&cbs, reinterpret_cast<const uint8_t*>(spki.data()), spki.size());
  pkey.reset(EVP_parse_public_key(&cbs));
  if (!pkey)
    return;

  switch (pkey->type) {
    case EVP_PKEY_RSA:
      *type = kPublicKeyTypeRSA;
      break;
    case EVP_PKEY_DSA:
      *type = kPublicKeyTypeDSA;
      break;
    case EVP_PKEY_EC:
      *type = kPublicKeyTypeECDSA;
      break;
    case EVP_PKEY_DH:
      *type = kPublicKeyTypeDH;
      break;
  }
  *size_bits = base::saturated_cast<size_t>(EVP_PKEY_bits(pkey.get()));
}

// static
bssl::UniquePtr<CRYPTO_BUFFER> X509Certificate::CreateCertBufferFromBytes(
    const char* data,
    size_t length) {
  der::Input tbs_certificate_tlv;
  der::Input signature_algorithm_tlv;
  der::BitString signature_value;
  // Do a bare minimum of DER parsing here to make sure the input is not
  // completely crazy. (This is required for at least
  // CreateCertificateListFromBytes with FORMAT_AUTO, if not more.)
  if (!ParseCertificate(
          der::Input(reinterpret_cast<const uint8_t*>(data), length),
          &tbs_certificate_tlv, &signature_algorithm_tlv, &signature_value,
          nullptr)) {
    return nullptr;
  }

  return x509_util::CreateCryptoBuffer(reinterpret_cast<const uint8_t*>(data),
                                       length);
}

// static
std::vector<bssl::UniquePtr<CRYPTO_BUFFER>>
X509Certificate::CreateCertBuffersFromBytes(const char* data,
                                            size_t length,
                                            Format format) {
  std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> results;

  switch (format) {
    case FORMAT_SINGLE_CERTIFICATE: {
      bssl::UniquePtr<CRYPTO_BUFFER> handle =
          CreateCertBufferFromBytes(data, length);
      if (handle)
        results.push_back(std::move(handle));
      break;
    }
    case FORMAT_PKCS7: {
      CreateCertBuffersFromPKCS7Bytes(data, length, &results);
      break;
    }
    default: {
      NOTREACHED() << "Certificate format " << format << " unimplemented";
      break;
    }
  }

  return results;
}

// static
SHA256HashValue X509Certificate::CalculateFingerprint256(
    const CRYPTO_BUFFER* cert) {
  SHA256HashValue sha256;

  SHA256(CRYPTO_BUFFER_data(cert), CRYPTO_BUFFER_len(cert), sha256.data);
  return sha256;
}

SHA256HashValue X509Certificate::CalculateChainFingerprint256() const {
  SHA256HashValue sha256;
  memset(sha256.data, 0, sizeof(sha256.data));

  SHA256_CTX sha256_ctx;
  SHA256_Init(&sha256_ctx);
  SHA256_Update(&sha256_ctx, CRYPTO_BUFFER_data(cert_buffer_.get()),
                CRYPTO_BUFFER_len(cert_buffer_.get()));
  for (const auto& cert : intermediate_ca_certs_) {
    SHA256_Update(&sha256_ctx, CRYPTO_BUFFER_data(cert.get()),
                  CRYPTO_BUFFER_len(cert.get()));
  }
  SHA256_Final(sha256.data, &sha256_ctx);

  return sha256;
}

// static
bool X509Certificate::IsSelfSigned(const CRYPTO_BUFFER* cert_buffer) {
  der::Input tbs_certificate_tlv;
  der::Input signature_algorithm_tlv;
  der::BitString signature_value;
  if (!ParseCertificate(der::Input(CRYPTO_BUFFER_data(cert_buffer),
                                   CRYPTO_BUFFER_len(cert_buffer)),
                        &tbs_certificate_tlv, &signature_algorithm_tlv,
                        &signature_value, nullptr)) {
    return false;
  }
  ParsedTbsCertificate tbs;
  if (!ParseTbsCertificate(tbs_certificate_tlv,
                           x509_util::DefaultParseCertificateOptions(), &tbs,
                           nullptr)) {
    return false;
  }

  der::Input subject_value;
  CertErrors errors;
  std::string normalized_subject;
  if (!ParseSequenceValue(tbs.subject_tlv, &subject_value) ||
      !NormalizeName(subject_value, &normalized_subject, &errors)) {
    return false;
  }
  der::Input issuer_value;
  std::string normalized_issuer;
  if (!ParseSequenceValue(tbs.issuer_tlv, &issuer_value) ||
      !NormalizeName(issuer_value, &normalized_issuer, &errors)) {
    return false;
  }

  if (normalized_subject != normalized_issuer)
    return false;

  std::unique_ptr<SignatureAlgorithm> signature_algorithm =
      SignatureAlgorithm::Create(signature_algorithm_tlv, nullptr /* errors */);
  if (!signature_algorithm)
    return false;

  // Don't enforce any minimum key size or restrict the algorithm, since when
  // self signed not very relevant.
  return VerifySignedData(*signature_algorithm, tbs_certificate_tlv,
                          signature_value, tbs.spki_tlv);
}

X509Certificate::X509Certificate(
    bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer,
    std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediates)
    : X509Certificate(std::move(cert_buffer), std::move(intermediates), {}) {}

X509Certificate::X509Certificate(
    bssl::UniquePtr<CRYPTO_BUFFER> cert_buffer,
    std::vector<bssl::UniquePtr<CRYPTO_BUFFER>> intermediates,
    UnsafeCreateOptions options)
    : cert_buffer_(std::move(cert_buffer)),
      intermediate_ca_certs_(std::move(intermediates)) {
  // Platform-specific initialization.
  if (!Initialize(options) && cert_buffer_) {
    // Signal initialization failure by clearing cert_buffer_.
    cert_buffer_.reset();
  }
}

X509Certificate::~X509Certificate() = default;

bool X509Certificate::Initialize(UnsafeCreateOptions options) {
  der::Input tbs_certificate_tlv;
  der::Input signature_algorithm_tlv;
  der::BitString signature_value;

  if (!ParseCertificate(der::Input(CRYPTO_BUFFER_data(cert_buffer_.get()),
                                   CRYPTO_BUFFER_len(cert_buffer_.get())),
                        &tbs_certificate_tlv, &signature_algorithm_tlv,
                        &signature_value, nullptr)) {
    return false;
  }

  ParsedTbsCertificate tbs;
  if (!ParseTbsCertificate(tbs_certificate_tlv,
                           x509_util::DefaultParseCertificateOptions(), &tbs,
                           nullptr))
    return false;

  CertPrincipal::PrintableStringHandling printable_string_handling =
      options.printable_string_is_utf8
          ? CertPrincipal::PrintableStringHandling::kAsUTF8Hack
          : CertPrincipal::PrintableStringHandling::kDefault;
  if (!subject_.ParseDistinguishedName(tbs.subject_tlv.UnsafeData(),
                                       tbs.subject_tlv.Length(),
                                       printable_string_handling) ||
      !issuer_.ParseDistinguishedName(tbs.issuer_tlv.UnsafeData(),
                                      tbs.issuer_tlv.Length(),
                                      printable_string_handling)) {
    return false;
  }

  if (!der::GeneralizedTimeToTime(tbs.validity_not_before, &valid_start_) ||
      !der::GeneralizedTimeToTime(tbs.validity_not_after, &valid_expiry_)) {
    return false;
  }
  serial_number_ = tbs.serial_number.AsString();
  return true;
}

}  // namespace net