text: // 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_tokenizer.h"
  #include "net/cert/x509_util.h"
  #include "net/der/parser.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->clear();
    } else {
      *left = src.substr(0, pos);
      *right = src.substr(pos);
    }
  }
  
  // Converts a GeneralizedTime struct to a base::Time, returning true on success
  // or false if |generalized| was invalid or cannot be represented by
  // base::Time.
  bool GeneralizedTimeToBaseTime(const der::GeneralizedTime& generalized,
                                 base::Time* result) {
    base::Time::Exploded exploded = {0};
    exploded.year = generalized.year;
    exploded.month = generalized.month;
    exploded.day_of_month = generalized.day;
    exploded.hour = generalized.hours;
    exploded.minute = generalized.minutes;
    exploded.second = generalized.seconds;
  
    if (base::Time::FromUTCExploded(exploded, result))
      return true;
  
    // Fail on obviously bad dates.
    if (!exploded.HasValidValues())
      return false;
  
    // TODO(mattm): consider consolidating this with
    // SaturatedTimeFromUTCExploded from cookie_util.cc
    if (static_cast<int>(generalized.year) > base::Time::kExplodedMaxYear) {
      *result = base::Time::Max();
      return true;
    }
    if (static_cast<int>(generalized.year) < base::Time::kExplodedMinYear) {
      *result = base::Time::Min();
      return true;
    }
    return false;
  }
  
  // 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 GetSequenceValue(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 (!GetSequenceValue(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 NULL;
  
    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) {
    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) {
    std::vector<std::string> normalized_issuers;
    CertErrors errors;
    for (const auto& raw_issuer : valid_issuers) {
      der::Input issuer_value;
      std::string normalized_issuer;
      if (!GetSequenceValue(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::ContainsValue(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::ContainsValue(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);
    // 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.empty() && *reference_name.rbegin() == '.')
      reference_name.resize(reference_name.size() - 1);
    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::ContainsValue(cert_san_ip_addrs, ip_addr_string);
    }
  
    // |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.
    std::vector<std::string> common_name_as_vector;
    const std::vector<std::string>* presented_names = &cert_san_dns_names;
    for (std::vector<std::string>::const_iterator it =
             presented_names->begin();
         it != presented_names->end(); ++it) {
      // Catch badly corrupt cert names up front.
      if (it->empty() || it->find('\0') != std::string::npos) {
        DVLOG(1) << "Bad name in cert: " << *it;
        continue;
      }
      std::string presented_name(base::ToLowerASCII(*it));
  
      // 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;
    std::string b64_encoded;
    base::Base64Encode(der_encoded, &b64_encoded);
    *pem_encoded = "-----BEGIN CERTIFICATE-----\n";
  
    // Divide the Base-64 encoded data into 64-character chunks, as per
    // 4.3.2.4 of RFC 1421.
    static const size_t kChunkSize = 64;
    size_t chunks = (b64_encoded.size() + (kChunkSize - 1)) / kChunkSize;
    for (size_t i = 0, chunk_offset = 0; i < chunks;
         ++i, chunk_offset += kChunkSize) {
      pem_encoded->append(b64_encoded, chunk_offset, kChunkSize);
      pem_encoded->append("\n");
    }
    pem_encoded->append("-----END CERTIFICATE-----\n");
    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 (!GetSequenceValue(tbs.subject_tlv, &subject_value) ||
        !NormalizeName(subject_value, &normalized_subject, &errors)) {
      return false;
    }
    der::Input issuer_value;
    std::string normalized_issuer;
    if (!GetSequenceValue(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 (!GeneralizedTimeToBaseTime(tbs.validity_not_before, &valid_start_) ||
        !GeneralizedTimeToBaseTime(tbs.validity_not_after, &valid_expiry_)) {
      return false;
    }
    serial_number_ = tbs.serial_number.AsString();
    return true;
  }
  
  }  // namespace net
  