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

#include "net/socket/ssl_server_socket_impl.h"

#include <cstdint>
#include <memory>
#include <optional>
#include <string_view>
#include <utility>
#include <vector>

#include "base/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/logging.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/notimplemented.h"
#include "base/strings/string_util.h"
#include "crypto/openssl_util.h"
#include "net/base/completion_once_callback.h"
#include "net/base/net_errors.h"
#include "net/cert/cert_verify_result.h"
#include "net/cert/client_cert_verifier.h"
#include "net/cert/x509_util.h"
#include "net/log/net_log_event_type.h"
#include "net/log/net_log_with_source.h"
#include "net/socket/socket_bio_adapter.h"
#include "net/ssl/openssl_ssl_util.h"
#include "net/ssl/ssl_connection_status_flags.h"
#include "net/ssl/ssl_info.h"
#include "net/traffic_annotation/network_traffic_annotation.h"
#include "third_party/boringssl/src/include/openssl/bytestring.h"
#include "third_party/boringssl/src/include/openssl/err.h"
#include "third_party/boringssl/src/include/openssl/pool.h"
#include "third_party/boringssl/src/include/openssl/ssl.h"

#define GotoState(s) next_handshake_state_ = s

namespace net {

class SSLServerContextImpl::SocketImpl : public SSLServerSocket,
                                         public SocketBIOAdapter::Delegate {
 public:
  SocketImpl(SSLServerContextImpl* context,
             std::unique_ptr<StreamSocket> socket);

  SocketImpl(const SocketImpl&) = delete;
  SocketImpl& operator=(const SocketImpl&) = delete;

  ~SocketImpl() override;

  // SSLServerSocket interface.
  int Handshake(CompletionOnceCallback callback) override;

  // SSLSocket interface.
  int ExportKeyingMaterial(std::string_view label,
                           std::optional<base::span<const uint8_t>> context,
                           base::span<uint8_t> out) override;

  // Socket interface (via StreamSocket).
  int Read(IOBuffer* buf,
           int buf_len,
           CompletionOnceCallback callback) override;
  int ReadIfReady(IOBuffer* buf,
                  int buf_len,
                  CompletionOnceCallback callback) override;
  int CancelReadIfReady() override;
  int Write(IOBuffer* buf,
            int buf_len,
            CompletionOnceCallback callback,
            const NetworkTrafficAnnotationTag& traffic_annotation) override;
  int SetReceiveBufferSize(int32_t size) override;
  int SetSendBufferSize(int32_t size) override;

  // StreamSocket implementation.
  int Connect(CompletionOnceCallback callback) override;
  void Disconnect() override;
  bool IsConnected() const override;
  bool IsConnectedAndIdle() const override;
  int GetPeerAddress(IPEndPoint* address) const override;
  int GetLocalAddress(IPEndPoint* address) const override;
  const NetLogWithSource& NetLog() const override;
  bool WasEverUsed() const override;
  NextProto GetNegotiatedProtocol() const override;
  std::optional<std::string_view> GetPeerApplicationSettings() const override;
  bool GetSSLInfo(SSLInfo* ssl_info) override;
  int64_t GetTotalReceivedBytes() const override;
  void ApplySocketTag(const SocketTag& tag) override;

  static SocketImpl* FromSSL(SSL* ssl);

  static ssl_verify_result_t CertVerifyCallback(SSL* ssl, uint8_t* out_alert);
  ssl_verify_result_t CertVerifyCallbackImpl(uint8_t* out_alert);

  static int ALPNSelectCallback(SSL* ssl,
                                const uint8_t** out,
                                uint8_t* out_len,
                                const uint8_t* in,
                                unsigned in_len,
                                void* arg);

  static ssl_select_cert_result_t SelectCertificateCallback(
      const SSL_CLIENT_HELLO* client_hello);

  // SocketBIOAdapter::Delegate implementation.
  void OnReadReady() override;
  void OnWriteReady() override;

 private:
  enum State {
    STATE_NONE,
    STATE_HANDSHAKE,
  };

  void OnHandshakeIOComplete(int result);

  [[nodiscard]] int DoPayloadRead(IOBuffer* buf, int buf_len);
  [[nodiscard]] int DoPayloadWrite();

  [[nodiscard]] int DoHandshakeLoop(int last_io_result);
  [[nodiscard]] int DoHandshake();
  void DoHandshakeCallback(int result);
  void DoReadCallback(int result);
  void DoWriteCallback(int result);

  [[nodiscard]] int Init();
  void ExtractClientCert();

  raw_ptr<SSLServerContextImpl> context_;

  NetLogWithSource net_log_;

  CompletionOnceCallback user_handshake_callback_;
  CompletionOnceCallback user_read_callback_;
  CompletionOnceCallback user_write_callback_;

  // Used by Read function.
  scoped_refptr<IOBuffer> user_read_buf_;
  int user_read_buf_len_ = 0;

  // Used by Write function.
  scoped_refptr<IOBuffer> user_write_buf_;
  int user_write_buf_len_ = 0;

  // OpenSSL stuff
  bssl::UniquePtr<SSL> ssl_;

  // Whether we received any data in early data.
  bool early_data_received_ = false;

  // StreamSocket for sending and receiving data.
  std::unique_ptr<StreamSocket> transport_socket_;
  std::unique_ptr<SocketBIOAdapter> transport_adapter_;

  // Certificate for the client.
  scoped_refptr<X509Certificate> client_cert_;

  State next_handshake_state_ = STATE_NONE;
  bool completed_handshake_ = false;

  NextProto negotiated_protocol_ = NextProto::kProtoUnknown;

  base::WeakPtrFactory<SocketImpl> weak_factory_{this};
};

SSLServerContextImpl::SocketImpl::SocketImpl(
    SSLServerContextImpl* context,
    std::unique_ptr<StreamSocket> transport_socket)
    : context_(context), transport_socket_(std::move(transport_socket)) {}

SSLServerContextImpl::SocketImpl::~SocketImpl() {
  if (ssl_) {
    // Calling SSL_shutdown prevents the session from being marked as
    // unresumable.
    SSL_shutdown(ssl_.get());
    ssl_.reset();
  }
}

// static
int SSLServerContextImpl::SocketImpl::ALPNSelectCallback(SSL* ssl,
                                                         const uint8_t** out,
                                                         uint8_t* out_len,
                                                         const uint8_t* in,
                                                         unsigned in_len,
                                                         void* arg) {
  SSLServerContextImpl::SocketImpl* socket = FromSSL(ssl);

  // Iterate over the server protocols in preference order.
  for (NextProto server_proto :
       socket->context_->ssl_server_config_.alpn_protos) {
    const char* server_proto_str = NextProtoToString(server_proto);

    // See if the client advertised the corresponding protocol.
    CBS cbs;
    CBS_init(&cbs, in, in_len);
    while (CBS_len(&cbs) != 0) {
      CBS client_proto;
      if (!CBS_get_u8_length_prefixed(&cbs, &client_proto)) {
        return SSL_TLSEXT_ERR_NOACK;
      }
      if (std::string_view(
              reinterpret_cast<const char*>(CBS_data(&client_proto)),
              CBS_len(&client_proto)) == server_proto_str) {
        *out = CBS_data(&client_proto);
        *out_len = CBS_len(&client_proto);

        const auto& application_settings =
            socket->context_->ssl_server_config_.application_settings;
        auto it = application_settings.find(server_proto);
        if (it != application_settings.end()) {
          const std::vector<uint8_t>& data = it->second;
          SSL_add_application_settings(ssl, CBS_data(&client_proto),
                                       CBS_len(&client_proto), data.data(),
                                       data.size());
        }
        return SSL_TLSEXT_ERR_OK;
      }
    }
  }
  return SSL_TLSEXT_ERR_NOACK;
}

ssl_select_cert_result_t
SSLServerContextImpl::SocketImpl::SelectCertificateCallback(
    const SSL_CLIENT_HELLO* client_hello) {
  SSLServerContextImpl::SocketImpl* socket = FromSSL(client_hello->ssl);
  const SSLServerConfig& config = socket->context_->ssl_server_config_;
  if (!config.client_hello_callback_for_testing.is_null() &&
      !config.client_hello_callback_for_testing.Run(client_hello)) {
    return ssl_select_cert_error;
  }
  return ssl_select_cert_success;
}

int SSLServerContextImpl::SocketImpl::Handshake(
    CompletionOnceCallback callback) {
  net_log_.BeginEvent(NetLogEventType::SSL_SERVER_HANDSHAKE);

  // Set up new ssl object.
  int rv = Init();
  if (rv != OK) {
    LOG(ERROR) << "Failed to initialize OpenSSL: rv=" << rv;
    net_log_.EndEventWithNetErrorCode(NetLogEventType::SSL_SERVER_HANDSHAKE,
                                      rv);
    return rv;
  }

  // Set SSL to server mode. Handshake happens in the loop below.
  SSL_set_accept_state(ssl_.get());

  GotoState(STATE_HANDSHAKE);
  rv = DoHandshakeLoop(OK);
  if (rv == ERR_IO_PENDING) {
    user_handshake_callback_ = std::move(callback);
  } else {
    net_log_.EndEventWithNetErrorCode(NetLogEventType::SSL_SERVER_HANDSHAKE,
                                      rv);
  }

  return rv > OK ? OK : rv;
}

int SSLServerContextImpl::SocketImpl::ExportKeyingMaterial(
    std::string_view label,
    std::optional<base::span<const uint8_t>> context,
    base::span<uint8_t> out) {
  DCHECK(base::IsStringASCII(label));
  if (!IsConnected())
    return ERR_SOCKET_NOT_CONNECTED;

  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);

  int rv = SSL_export_keying_material(
      ssl_.get(), out.data(), out.size(), label.data(), label.size(),
      context.has_value() ? context->data() : nullptr,
      context.has_value() ? context->size() : 0, context.has_value());

  if (rv != 1) {
    int ssl_error = SSL_get_error(ssl_.get(), rv);
    LOG(ERROR) << "Failed to export keying material;"
               << " returned " << rv << ", SSL error code " << ssl_error;
    return MapOpenSSLError(ssl_error, err_tracer);
  }
  return OK;
}

int SSLServerContextImpl::SocketImpl::Read(IOBuffer* buf,
                                           int buf_len,
                                           CompletionOnceCallback callback) {
  int rv = ReadIfReady(buf, buf_len, std::move(callback));
  if (rv == ERR_IO_PENDING) {
    user_read_buf_ = buf;
    user_read_buf_len_ = buf_len;
  }
  return rv;
}

int SSLServerContextImpl::SocketImpl::ReadIfReady(
    IOBuffer* buf,
    int buf_len,
    CompletionOnceCallback callback) {
  DCHECK(user_read_callback_.is_null());
  DCHECK(user_handshake_callback_.is_null());
  DCHECK(!user_read_buf_);
  DCHECK(!callback.is_null());
  DCHECK(completed_handshake_);

  int rv = DoPayloadRead(buf, buf_len);

  if (rv == ERR_IO_PENDING) {
    user_read_callback_ = std::move(callback);
  }

  return rv;
}

int SSLServerContextImpl::SocketImpl::CancelReadIfReady() {
  DCHECK(user_read_callback_);
  DCHECK(!user_read_buf_);

  // Cancel |user_read_callback_|, because caller does not expect the callback
  // to be invoked after they have canceled the ReadIfReady.
  //
  // We do not pass the signal on to |stream_socket_| or |transport_adapter_|.
  // When it completes, it will signal OnReadReady(), which will notice there is
  // no read operation to progress and skip it. Unlike with SSLClientSocket,
  // SSL and transport reads are more aligned, but this avoids making
  // assumptions or breaking the SocketBIOAdapter's state.
  user_read_callback_.Reset();
  return OK;
}

int SSLServerContextImpl::SocketImpl::Write(
    IOBuffer* buf,
    int buf_len,
    CompletionOnceCallback callback,
    const NetworkTrafficAnnotationTag& traffic_annotation) {
  DCHECK(user_write_callback_.is_null());
  DCHECK(!user_write_buf_);
  DCHECK(!callback.is_null());

  user_write_buf_ = buf;
  user_write_buf_len_ = buf_len;

  int rv = DoPayloadWrite();

  if (rv == ERR_IO_PENDING) {
    user_write_callback_ = std::move(callback);
  } else {
    user_write_buf_ = nullptr;
    user_write_buf_len_ = 0;
  }
  return rv;
}

int SSLServerContextImpl::SocketImpl::SetReceiveBufferSize(int32_t size) {
  return transport_socket_->SetReceiveBufferSize(size);
}

int SSLServerContextImpl::SocketImpl::SetSendBufferSize(int32_t size) {
  return transport_socket_->SetSendBufferSize(size);
}

int SSLServerContextImpl::SocketImpl::Connect(CompletionOnceCallback callback) {
  NOTIMPLEMENTED();
  return ERR_NOT_IMPLEMENTED;
}

void SSLServerContextImpl::SocketImpl::Disconnect() {
  transport_socket_->Disconnect();
}

bool SSLServerContextImpl::SocketImpl::IsConnected() const {
  // TODO(wtc): Find out if we should check transport_socket_->IsConnected()
  // as well.
  return completed_handshake_;
}

bool SSLServerContextImpl::SocketImpl::IsConnectedAndIdle() const {
  return completed_handshake_ && transport_socket_->IsConnectedAndIdle();
}

int SSLServerContextImpl::SocketImpl::GetPeerAddress(
    IPEndPoint* address) const {
  if (!IsConnected())
    return ERR_SOCKET_NOT_CONNECTED;
  return transport_socket_->GetPeerAddress(address);
}

int SSLServerContextImpl::SocketImpl::GetLocalAddress(
    IPEndPoint* address) const {
  if (!IsConnected())
    return ERR_SOCKET_NOT_CONNECTED;
  return transport_socket_->GetLocalAddress(address);
}

const NetLogWithSource& SSLServerContextImpl::SocketImpl::NetLog() const {
  return net_log_;
}

bool SSLServerContextImpl::SocketImpl::WasEverUsed() const {
  return transport_socket_->WasEverUsed();
}

NextProto SSLServerContextImpl::SocketImpl::GetNegotiatedProtocol() const {
  return negotiated_protocol_;
}

std::optional<std::string_view>
SSLServerContextImpl::SocketImpl::GetPeerApplicationSettings() const {
  if (!SSL_has_application_settings(ssl_.get())) {
    return std::nullopt;
  }

  const uint8_t* out_data;
  size_t out_len;
  SSL_get0_peer_application_settings(ssl_.get(), &out_data, &out_len);
  return std::string_view{reinterpret_cast<const char*>(out_data), out_len};
}

bool SSLServerContextImpl::SocketImpl::GetSSLInfo(SSLInfo* ssl_info) {
  *ssl_info = SSLInfo();
  if (!completed_handshake_)
    return false;

  ssl_info->cert = client_cert_;

  const SSL_CIPHER* cipher = SSL_get_current_cipher(ssl_.get());
  CHECK(cipher);

  SSLConnectionStatusSetCipherSuite(SSL_CIPHER_get_protocol_id(cipher),
                                    &ssl_info->connection_status);
  SSLConnectionStatusSetVersion(GetNetSSLVersion(ssl_.get()),
                                &ssl_info->connection_status);

  ssl_info->early_data_received = early_data_received_;
  ssl_info->early_data_accepted = SSL_early_data_accepted(ssl_.get());
  ssl_info->encrypted_client_hello = SSL_ech_accepted(ssl_.get());
  ssl_info->handshake_type = SSL_session_reused(ssl_.get())
                                 ? SSLInfo::HANDSHAKE_RESUME
                                 : SSLInfo::HANDSHAKE_FULL;
  ssl_info->peer_signature_algorithm =
      SSL_get_peer_signature_algorithm(ssl_.get());

  return true;
}

int64_t SSLServerContextImpl::SocketImpl::GetTotalReceivedBytes() const {
  return transport_socket_->GetTotalReceivedBytes();
}

void SSLServerContextImpl::SocketImpl::ApplySocketTag(const SocketTag& tag) {
  NOTIMPLEMENTED();
}

void SSLServerContextImpl::SocketImpl::OnReadReady() {
  if (next_handshake_state_ == STATE_HANDSHAKE) {
    // In handshake phase. The parameter to OnHandshakeIOComplete is unused.
    OnHandshakeIOComplete(OK);
    return;
  }

  // BoringSSL does not support renegotiation as a server, so the only other
  // operation blocked on Read is DoPayloadRead.
  if (!user_read_buf_) {
    if (!user_read_callback_.is_null()) {
      DoReadCallback(OK);
    }
    return;
  }

  int rv = DoPayloadRead(user_read_buf_.get(), user_read_buf_len_);
  if (rv != ERR_IO_PENDING)
    DoReadCallback(rv);
}

void SSLServerContextImpl::SocketImpl::OnWriteReady() {
  if (next_handshake_state_ == STATE_HANDSHAKE) {
    // In handshake phase. The parameter to OnHandshakeIOComplete is unused.
    OnHandshakeIOComplete(OK);
    return;
  }

  // BoringSSL does not support renegotiation as a server, so the only other
  // operation blocked on Read is DoPayloadWrite.
  if (!user_write_buf_)
    return;

  int rv = DoPayloadWrite();
  if (rv != ERR_IO_PENDING)
    DoWriteCallback(rv);
}

void SSLServerContextImpl::SocketImpl::OnHandshakeIOComplete(int result) {
  int rv = DoHandshakeLoop(result);
  if (rv == ERR_IO_PENDING)
    return;

  net_log_.EndEventWithNetErrorCode(NetLogEventType::SSL_SERVER_HANDSHAKE, rv);
  if (!user_handshake_callback_.is_null())
    DoHandshakeCallback(rv);
}

int SSLServerContextImpl::SocketImpl::DoPayloadRead(IOBuffer* buf,
                                                    int buf_len) {
  DCHECK(completed_handshake_);
  DCHECK_EQ(STATE_NONE, next_handshake_state_);
  DCHECK(buf);
  DCHECK_GT(buf_len, 0);

  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  int rv = SSL_read(ssl_.get(), buf->data(), buf_len);
  if (rv >= 0) {
    if (SSL_in_early_data(ssl_.get()))
      early_data_received_ = true;
    return rv;
  }
  int ssl_error = SSL_get_error(ssl_.get(), rv);
  OpenSSLErrorInfo error_info;
  int net_error =
      MapOpenSSLErrorWithDetails(ssl_error, err_tracer, &error_info);
  if (net_error != ERR_IO_PENDING) {
    NetLogOpenSSLError(net_log_, NetLogEventType::SSL_READ_ERROR, net_error,
                       ssl_error, error_info);
  }
  return net_error;
}

int SSLServerContextImpl::SocketImpl::DoPayloadWrite() {
  DCHECK(completed_handshake_);
  DCHECK_EQ(STATE_NONE, next_handshake_state_);
  DCHECK(user_write_buf_);

  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  int rv = SSL_write(ssl_.get(), user_write_buf_->data(), user_write_buf_len_);
  if (rv >= 0)
    return rv;
  int ssl_error = SSL_get_error(ssl_.get(), rv);
  OpenSSLErrorInfo error_info;
  int net_error =
      MapOpenSSLErrorWithDetails(ssl_error, err_tracer, &error_info);
  if (net_error != ERR_IO_PENDING) {
    NetLogOpenSSLError(net_log_, NetLogEventType::SSL_WRITE_ERROR, net_error,
                       ssl_error, error_info);
  }
  return net_error;
}

int SSLServerContextImpl::SocketImpl::DoHandshakeLoop(int last_io_result) {
  int rv = last_io_result;
  do {
    // Default to STATE_NONE for next state.
    // (This is a quirk carried over from the windows
    // implementation.  It makes reading the logs a bit harder.)
    // State handlers can and often do call GotoState just
    // to stay in the current state.
    State state = next_handshake_state_;
    GotoState(STATE_NONE);
    switch (state) {
      case STATE_HANDSHAKE:
        rv = DoHandshake();
        break;
      case STATE_NONE:
      default:
        rv = ERR_UNEXPECTED;
        LOG(DFATAL) << "unexpected state " << state;
        break;
    }
  } while (rv != ERR_IO_PENDING && next_handshake_state_ != STATE_NONE);
  return rv;
}

int SSLServerContextImpl::SocketImpl::DoHandshake() {
  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  int net_error = OK;
  int rv = SSL_do_handshake(ssl_.get());
  if (rv == 1) {
    const STACK_OF(CRYPTO_BUFFER)* certs =
        SSL_get0_peer_certificates(ssl_.get());
    if (certs) {
      client_cert_ = x509_util::CreateX509CertificateFromBuffers(certs);
      if (!client_cert_)
        return ERR_SSL_CLIENT_AUTH_CERT_BAD_FORMAT;
    }

    const uint8_t* alpn_proto = nullptr;
    unsigned alpn_len = 0;
    SSL_get0_alpn_selected(ssl_.get(), &alpn_proto, &alpn_len);
    if (alpn_len > 0) {
      std::string_view proto(reinterpret_cast<const char*>(alpn_proto),
                             alpn_len);
      negotiated_protocol_ = NextProtoFromString(proto);
    }

    if (context_->ssl_server_config_.alert_after_handshake_for_testing) {
      SSL_send_fatal_alert(ssl_.get(),
                           context_->ssl_server_config_
                               .alert_after_handshake_for_testing.value());
      return ERR_FAILED;
    }

    completed_handshake_ = true;
  } else {
    int ssl_error = SSL_get_error(ssl_.get(), rv);

    OpenSSLErrorInfo error_info;
    net_error = MapOpenSSLErrorWithDetails(ssl_error, err_tracer, &error_info);

    // SSL_R_CERTIFICATE_VERIFY_FAILED's mapping is different between client and
    // server.
    if (ERR_GET_LIB(error_info.error_code) == ERR_LIB_SSL &&
        ERR_GET_REASON(error_info.error_code) ==
            SSL_R_CERTIFICATE_VERIFY_FAILED) {
      net_error = ERR_BAD_SSL_CLIENT_AUTH_CERT;
    }

    // If not done, stay in this state
    if (net_error == ERR_IO_PENDING) {
      GotoState(STATE_HANDSHAKE);
    } else {
      LOG(ERROR) << "handshake failed; returned " << rv << ", SSL error code "
                 << ssl_error << ", net_error " << net_error;
      NetLogOpenSSLError(net_log_, NetLogEventType::SSL_HANDSHAKE_ERROR,
                         net_error, ssl_error, error_info);
    }
  }
  return net_error;
}

void SSLServerContextImpl::SocketImpl::DoHandshakeCallback(int rv) {
  DCHECK_NE(rv, ERR_IO_PENDING);
  std::move(user_handshake_callback_).Run(rv > OK ? OK : rv);
}

void SSLServerContextImpl::SocketImpl::DoReadCallback(int rv) {
  DCHECK(rv != ERR_IO_PENDING);
  DCHECK(!user_read_callback_.is_null());

  user_read_buf_ = nullptr;
  user_read_buf_len_ = 0;
  std::move(user_read_callback_).Run(rv);
}

void SSLServerContextImpl::SocketImpl::DoWriteCallback(int rv) {
  DCHECK(rv != ERR_IO_PENDING);
  DCHECK(!user_write_callback_.is_null());

  user_write_buf_ = nullptr;
  user_write_buf_len_ = 0;
  std::move(user_write_callback_).Run(rv);
}

int SSLServerContextImpl::SocketImpl::Init() {
  static const int kBufferSize = 17 * 1024;

  crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);

  ssl_.reset(SSL_new(context_->ssl_ctx_.get()));
  if (!ssl_ || !SSL_set_app_data(ssl_.get(), this)) {
    return ERR_UNEXPECTED;
  }

  SSL_set_shed_handshake_config(ssl_.get(), 1);

  for (const SSLServerCredential& credential : context_->credentials_) {
    std::vector<uint16_t> signing_algorithm_prefs;
    if (credential.signature_algorithm_for_testing.has_value()) {
      signing_algorithm_prefs.emplace_back(
          *credential.signature_algorithm_for_testing);
    }
    std::vector<CRYPTO_BUFFER*> chain_raw =
        GetCertChainRawVector(credential.cert_chain);
    ConfigureSSLCredentialParams params{
        .cert_chain = chain_raw,
        .private_key = credential.pkey.get(),
        .signing_algorithm_prefs = signing_algorithm_prefs,
        .ocsp_response = credential.ocsp_response,
        .signed_cert_timestamp_list = credential.signed_cert_timestamp_list,
        .trust_anchor_id = credential.trust_anchor_id,
    };

    if (!ConfigureSSLCredential(ssl_.get(), params)) {
      return ERR_UNEXPECTED;
    }
  }

  const std::vector<int>& curves =
      context_->ssl_server_config_.curves_for_testing;
  if (!curves.empty()) {
    CHECK(SSL_set1_curves(ssl_.get(), curves.data(), curves.size()));
  }

  transport_adapter_ = std::make_unique<SocketBIOAdapter>(
      transport_socket_.get(), kBufferSize, kBufferSize, this);
  BIO* transport_bio = transport_adapter_->bio();

  BIO_up_ref(transport_bio);  // SSL_set0_rbio takes ownership.
  SSL_set0_rbio(ssl_.get(), transport_bio);

  BIO_up_ref(transport_bio);  // SSL_set0_wbio takes ownership.
  SSL_set0_wbio(ssl_.get(), transport_bio);

  return OK;
}

SSLServerContextImpl::SocketImpl* SSLServerContextImpl::SocketImpl::FromSSL(
    SSL* ssl) {
  SocketImpl* socket = reinterpret_cast<SocketImpl*>(SSL_get_app_data(ssl));
  DCHECK(socket);
  return socket;
}

// static
ssl_verify_result_t SSLServerContextImpl::SocketImpl::CertVerifyCallback(
    SSL* ssl,
    uint8_t* out_alert) {
  return FromSSL(ssl)->CertVerifyCallbackImpl(out_alert);
}

ssl_verify_result_t SSLServerContextImpl::SocketImpl::CertVerifyCallbackImpl(
    uint8_t* out_alert) {
  ClientCertVerifier* verifier =
      context_->ssl_server_config_.client_cert_verifier;
  // If a verifier was not supplied, all certificates are accepted.
  if (!verifier)
    return ssl_verify_ok;

  scoped_refptr<X509Certificate> client_cert =
      x509_util::CreateX509CertificateFromBuffers(
          SSL_get0_peer_certificates(ssl_.get()));
  if (!client_cert) {
    *out_alert = SSL_AD_BAD_CERTIFICATE;
    return ssl_verify_invalid;
  }

  // TODO(davidben): Support asynchronous verifiers. http://crbug.com/347402
  std::unique_ptr<ClientCertVerifier::Request> ignore_async;
  int res = verifier->Verify(client_cert.get(), CompletionOnceCallback(),
                             &ignore_async);
  DCHECK_NE(res, ERR_IO_PENDING);

  if (res != OK) {
    // TODO(davidben): Map from certificate verification failure to alert.
    *out_alert = SSL_AD_CERTIFICATE_UNKNOWN;
    return ssl_verify_invalid;
  }
  return ssl_verify_ok;
}

std::unique_ptr<SSLServerContext> CreateSSLServerContext(
    X509Certificate* certificate,
    EVP_PKEY* pkey,
    const SSLServerConfig& ssl_server_config) {
  SSLServerCredential credential;
  credential.cert_chain = certificate->CopyCertBuffers();
  credential.pkey = bssl::UpRef(pkey);
  std::vector<SSLServerCredential> credentials;
  credentials.push_back(std::move(credential));
  return std::make_unique<SSLServerContextImpl>(std::move(credentials),
                                                ssl_server_config);
}

NET_EXPORT std::unique_ptr<SSLServerContext> CreateSSLServerContext(
    std::vector<SSLServerCredential> credentials,
    const SSLServerConfig& ssl_config) {
  return std::make_unique<SSLServerContextImpl>(std::move(credentials),
                                                ssl_config);
}

SSLServerContextImpl::SSLServerContextImpl(
    std::vector<SSLServerCredential> credentials,
    const SSLServerConfig& ssl_server_config)
    : ssl_server_config_(ssl_server_config),
      credentials_(std::move(credentials)) {
  CHECK(!credentials_.empty());
  Init();
}

void SSLServerContextImpl::Init() {
  ssl_ctx_.reset(SSL_CTX_new(TLS_with_buffers_method()));
  SSL_CTX_set_session_cache_mode(ssl_ctx_.get(), SSL_SESS_CACHE_SERVER);
  uint8_t session_ctx_id = 0;
  SSL_CTX_set_session_id_context(ssl_ctx_.get(), &session_ctx_id,
                                 sizeof(session_ctx_id));
  // Deduplicate all certificates minted from the SSL_CTX in memory.
  SSL_CTX_set0_buffer_pool(ssl_ctx_.get(), x509_util::GetBufferPool());

  int verify_mode = 0;
  switch (ssl_server_config_.client_cert_type) {
    case SSLServerConfig::ClientCertType::REQUIRE_CLIENT_CERT:
      verify_mode |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
      [[fallthrough]];
    case SSLServerConfig::ClientCertType::OPTIONAL_CLIENT_CERT:
      verify_mode |= SSL_VERIFY_PEER;
      SSL_CTX_set_custom_verify(ssl_ctx_.get(), verify_mode,
                                SocketImpl::CertVerifyCallback);
      break;
    case SSLServerConfig::ClientCertType::NO_CLIENT_CERT:
      break;
  }

  SSL_CTX_set_early_data_enabled(ssl_ctx_.get(),
                                 ssl_server_config_.early_data_enabled);
  // TLS versions before TLS 1.2 are no longer supported.
  CHECK_LE(TLS1_2_VERSION, ssl_server_config_.version_min);
  CHECK_LE(TLS1_2_VERSION, ssl_server_config_.version_max);
  CHECK(SSL_CTX_set_min_proto_version(ssl_ctx_.get(),
                                      ssl_server_config_.version_min));
  CHECK(SSL_CTX_set_max_proto_version(ssl_ctx_.get(),
                                      ssl_server_config_.version_max));

  if (ssl_server_config_.cipher_suite_for_testing.has_value()) {
    const SSL_CIPHER* cipher =
        SSL_get_cipher_by_value(*ssl_server_config_.cipher_suite_for_testing);
    CHECK(cipher);
    CHECK(SSL_CTX_set_strict_cipher_list(ssl_ctx_.get(),
                                         SSL_CIPHER_get_name(cipher)));
  } else {
    // Use BoringSSL defaults, but disable 3DES and HMAC-SHA1 ciphers in ECDSA.
    // These are the remaining CBC-mode ECDSA ciphers.
    std::string command("ALL:!aPSK:!ECDSA+SHA1:!3DES");

    if (ssl_server_config_.require_ecdhe) {
      command.append(":!kRSA");
    }

    // Remove any disabled ciphers.
    for (uint16_t id : ssl_server_config_.disabled_cipher_suites) {
      const SSL_CIPHER* cipher = SSL_get_cipher_by_value(id);
      if (cipher) {
        command.append(":!");
        command.append(SSL_CIPHER_get_name(cipher));
      }
    }

    CHECK(SSL_CTX_set_strict_cipher_list(ssl_ctx_.get(), command.c_str()));
  }

  if (ssl_server_config_.client_cert_type !=
      SSLServerConfig::ClientCertType::NO_CLIENT_CERT) {
    if (!ssl_server_config_.cert_authorities.empty()) {
      bssl::UniquePtr<STACK_OF(CRYPTO_BUFFER)> stack(
          sk_CRYPTO_BUFFER_new_null());
      for (const auto& authority : ssl_server_config_.cert_authorities) {
        sk_CRYPTO_BUFFER_push(
            stack.get(), x509_util::CreateCryptoBuffer(authority).release());
      }
      SSL_CTX_set0_client_CAs(ssl_ctx_.get(), stack.release());
    }

    if (!ssl_server_config_.client_cert_signature_algorithms.empty()) {
      CHECK(SSL_CTX_set_verify_algorithm_prefs(
          ssl_ctx_.get(),
          ssl_server_config_.client_cert_signature_algorithms.data(),
          ssl_server_config_.client_cert_signature_algorithms.size()));
    }
  }

  SSL_CTX_set_alpn_select_cb(ssl_ctx_.get(), &SocketImpl::ALPNSelectCallback,
                             nullptr);

  if (ssl_server_config_.ech_keys) {
    CHECK(SSL_CTX_set1_ech_keys(ssl_ctx_.get(),
                                ssl_server_config_.ech_keys.get()));
  }

  SSL_CTX_set_select_certificate_cb(ssl_ctx_.get(),
                                    &SocketImpl::SelectCertificateCallback);
}

SSLServerContextImpl::~SSLServerContextImpl() = default;

std::unique_ptr<SSLServerSocket> SSLServerContextImpl::CreateSSLServerSocket(
    std::unique_ptr<StreamSocket> socket) {
  return std::make_unique<SocketImpl>(this, std::move(socket));
}

}  // namespace net