/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 *

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 *

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 *

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

/* ====================================================================

 * Copyright (c) 1998-2002 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 * ====================================================================

 *

 * This product includes cryptographic software written by Eric Young

 * (eay@cryptsoft.com).  This product includes software written by Tim

 * Hudson (tjh@cryptsoft.com). */

/* ====================================================================

 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.

 * ECC cipher suite support in OpenSSL originally developed by

 * SUN MICROSYSTEMS, INC., and contributed to the OpenSSL project. */

#include <openssl/ssl.h>

#include <assert.h>

#include <utility>

#include <openssl/rand.h>

#include "../crypto/internal.h"

#include "internal.h"

BSSL_NAMESPACE_BEGIN

SSL_HANDSHAKE::SSL_HANDSHAKE(SSL *ssl_arg)

    : ssl(ssl_arg),

      ech_is_inner(false),

      ech_authenticated_reject(false),

      scts_requested(false),

      handshake_finalized(false),

      accept_psk_mode(false),

      cert_request(false),

      certificate_status_expected(false),

      ocsp_stapling_requested(false),

      delegated_credential_requested(false),

      should_ack_sni(false),

      in_false_start(false),

      in_early_data(false),

      early_data_offered(false),

      can_early_read(false),

      can_early_write(false),

      next_proto_neg_seen(false),

      ticket_expected(false),

      extended_master_secret(false),

      pending_private_key_op(false),

      handback(false),

      hints_requested(false),

      cert_compression_negotiated(false),

      apply_jdk11_workaround(false),

      can_release_private_key(false),

      channel_id_negotiated(false) {

  assert(ssl);

  // Draw entropy for all GREASE values at once. This avoids calling

  // |RAND_bytes| repeatedly and makes the values consistent within a

  // connection. The latter is so the second ClientHello matches after

  // HelloRetryRequest and so supported_groups and key_shares are consistent.

  RAND_bytes(grease_seed, sizeof(grease_seed));

}

SSL_HANDSHAKE::~SSL_HANDSHAKE() {

  ssl->ctx->x509_method->hs_flush_cached_ca_names(this);

}

void SSL_HANDSHAKE::ResizeSecrets(size_t hash_len) {

  if (hash_len > SSL_MAX_MD_SIZE) {

    abort();

  }

  hash_len_ = hash_len;

}

bool SSL_HANDSHAKE::GetClientHello(SSLMessage *out_msg,

                                   SSL_CLIENT_HELLO *out_client_hello) {

  if (!ech_client_hello_buf.empty()) {

    // If the backing buffer is non-empty, the ClientHelloInner has been set.

    out_msg->is_v2_hello = false;

    out_msg->type = SSL3_MT_CLIENT_HELLO;

    out_msg->raw = CBS(ech_client_hello_buf);

    out_msg->body = MakeConstSpan(ech_client_hello_buf).subspan(4);

  } else if (!ssl->method->get_message(ssl, out_msg)) {

    // The message has already been read, so this cannot fail.

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return false;

  }

  if (!ssl_client_hello_init(ssl, out_client_hello, out_msg->body)) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);

    ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);

    return false;

  }

  return true;

}

UniquePtr<SSL_HANDSHAKE> ssl_handshake_new(SSL *ssl) {

  UniquePtr<SSL_HANDSHAKE> hs = MakeUnique<SSL_HANDSHAKE>(ssl);

  if (!hs || !hs->transcript.Init()) {

    return nullptr;

  }

  hs->config = ssl->config.get();

  if (!hs->config) {

    assert(hs->config);

    return nullptr;

  }

  return hs;

}

bool ssl_check_message_type(SSL *ssl, const SSLMessage &msg, int type) {

  if (msg.type != type) {

    ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);

    OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_MESSAGE);

    ERR_add_error_dataf("got type %d, wanted type %d", msg.type, type);

    return false;

  }

  return true;

}

bool ssl_add_message_cbb(SSL *ssl, CBB *cbb) {

  Array<uint8_t> msg;

  if (!ssl->method->finish_message(ssl, cbb, &msg) ||

      !ssl->method->add_message(ssl, std::move(msg))) {

    return false;

  }

  return true;

}

size_t ssl_max_handshake_message_len(const SSL *ssl) {

  // kMaxMessageLen is the default maximum message size for handshakes which do

  // not accept peer certificate chains.

  static const size_t kMaxMessageLen = 16384;

  if (SSL_in_init(ssl)) {

    SSL_CONFIG *config = ssl->config.get();  // SSL_in_init() implies not NULL.

    if ((!ssl->server || (config->verify_mode & SSL_VERIFY_PEER)) &&

        kMaxMessageLen < ssl->max_cert_list) {

      return ssl->max_cert_list;

    }

    return kMaxMessageLen;

  }

  if (ssl_protocol_version(ssl) < TLS1_3_VERSION) {

    // In TLS 1.2 and below, the largest acceptable post-handshake message is

    // a HelloRequest.

    return 0;

  }

  if (ssl->server) {

    // The largest acceptable post-handshake message for a server is a

    // KeyUpdate. We will never initiate post-handshake auth.

    return 1;

  }

  // Clients must accept NewSessionTicket, so allow the default size.

  return kMaxMessageLen;

}

bool ssl_hash_message(SSL_HANDSHAKE *hs, const SSLMessage &msg) {

  // V2ClientHello messages are pre-hashed.

  if (msg.is_v2_hello) {

    return true;

  }

  return hs->transcript.Update(msg.raw);

}

bool ssl_parse_extensions(const CBS *cbs, uint8_t *out_alert,

                          std::initializer_list<SSLExtension *> extensions,

                          bool ignore_unknown) {

  // Reset everything.

  for (SSLExtension *ext : extensions) {

    ext->present = false;

    CBS_init(&ext->data, nullptr, 0);

    if (!ext->allowed) {

      assert(!ignore_unknown);

    }

  }

  CBS copy = *cbs;

  while (CBS_len(&copy) != 0) {

    uint16_t type;

    CBS data;

    if (!CBS_get_u16(&copy, &type) ||

        !CBS_get_u16_length_prefixed(&copy, &data)) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_PARSE_TLSEXT);

      *out_alert = SSL_AD_DECODE_ERROR;

      return false;

    }

    SSLExtension *found = nullptr;

    for (SSLExtension *ext : extensions) {

      if (type == ext->type && ext->allowed) {

        found = ext;

        break;

      }

    }

    if (found == nullptr) {

      if (ignore_unknown) {

        continue;

      }

      OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_EXTENSION);

      *out_alert = SSL_AD_UNSUPPORTED_EXTENSION;

      return false;

    }

    // Duplicate ext_types are forbidden.

    if (found->present) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);

      *out_alert = SSL_AD_ILLEGAL_PARAMETER;

      return false;

    }

    found->present = true;

    found->data = data;

  }

  return true;

}

enum ssl_verify_result_t ssl_verify_peer_cert(SSL_HANDSHAKE *hs) {

  SSL *const ssl = hs->ssl;

  const SSL_SESSION *prev_session = ssl->s3->established_session.get();

  if (prev_session != NULL) {

    // If renegotiating, the server must not change the server certificate. See

    // https://mitls.org/pages/attacks/3SHAKE. We never resume on renegotiation,

    // so this check is sufficient to ensure the reported peer certificate never

    // changes on renegotiation.

    assert(!ssl->server);

    if (sk_CRYPTO_BUFFER_num(prev_session->certs.get()) !=

        sk_CRYPTO_BUFFER_num(hs->new_session->certs.get())) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_SERVER_CERT_CHANGED);

      ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);

      return ssl_verify_invalid;

    }

    for (size_t i = 0; i < sk_CRYPTO_BUFFER_num(hs->new_session->certs.get());

         i++) {

      const CRYPTO_BUFFER *old_cert =

          sk_CRYPTO_BUFFER_value(prev_session->certs.get(), i);

      const CRYPTO_BUFFER *new_cert =

          sk_CRYPTO_BUFFER_value(hs->new_session->certs.get(), i);

      if (CRYPTO_BUFFER_len(old_cert) != CRYPTO_BUFFER_len(new_cert) ||

          OPENSSL_memcmp(CRYPTO_BUFFER_data(old_cert),

                         CRYPTO_BUFFER_data(new_cert),

                         CRYPTO_BUFFER_len(old_cert)) != 0) {

        OPENSSL_PUT_ERROR(SSL, SSL_R_SERVER_CERT_CHANGED);

        ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);

        return ssl_verify_invalid;

      }

    }

    // The certificate is identical, so we may skip re-verifying the

    // certificate. Since we only authenticated the previous one, copy other

    // authentication from the established session and ignore what was newly

    // received.

    hs->new_session->ocsp_response = UpRef(prev_session->ocsp_response);

    hs->new_session->signed_cert_timestamp_list =

        UpRef(prev_session->signed_cert_timestamp_list);

    hs->new_session->verify_result = prev_session->verify_result;

    return ssl_verify_ok;

  }

  uint8_t alert = SSL_AD_CERTIFICATE_UNKNOWN;

  enum ssl_verify_result_t ret;

  if (hs->config->custom_verify_callback != nullptr) {

    ret = hs->config->custom_verify_callback(ssl, &alert);

    switch (ret) {

      case ssl_verify_ok:

        hs->new_session->verify_result = X509_V_OK;

        break;

      case ssl_verify_invalid:

        // If |SSL_VERIFY_NONE|, the error is non-fatal, but we keep the result.

        if (hs->config->verify_mode == SSL_VERIFY_NONE) {

          ERR_clear_error();

          ret = ssl_verify_ok;

        }

        hs->new_session->verify_result = X509_V_ERR_APPLICATION_VERIFICATION;

        break;

      case ssl_verify_retry:

        break;

    }

  } else {

    ret = ssl->ctx->x509_method->session_verify_cert_chain(

              hs->new_session.get(), hs, &alert)

              ? ssl_verify_ok

              : ssl_verify_invalid;

  }

  if (ret == ssl_verify_invalid) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_CERTIFICATE_VERIFY_FAILED);

    ssl_send_alert(ssl, SSL3_AL_FATAL, alert);

  }

  // Emulate OpenSSL's client OCSP callback. OpenSSL verifies certificates

  // before it receives the OCSP, so it needs a second callback for OCSP.

  if (ret == ssl_verify_ok && !ssl->server &&

      hs->config->ocsp_stapling_enabled &&

      ssl->ctx->legacy_ocsp_callback != nullptr) {

    int cb_ret =

        ssl->ctx->legacy_ocsp_callback(ssl, ssl->ctx->legacy_ocsp_callback_arg);

    if (cb_ret <= 0) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_OCSP_CB_ERROR);

      ssl_send_alert(ssl, SSL3_AL_FATAL,

                     cb_ret == 0 ? SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE

                                 : SSL_AD_INTERNAL_ERROR);

      ret = ssl_verify_invalid;

    }

  }

  return ret;

}

// Verifies a stored certificate when resuming a session. A few things are

// different from verify_peer_cert:

// 1. We can't be renegotiating if we're resuming a session.

// 2. The session is immutable, so we don't support verify_mode ==

// SSL_VERIFY_NONE

// 3. We don't call the OCSP callback.

// 4. We only support custom verify callbacks.

enum ssl_verify_result_t ssl_reverify_peer_cert(SSL_HANDSHAKE *hs,

                                                bool send_alert) {

  SSL *const ssl = hs->ssl;

  assert(ssl->s3->established_session == nullptr);

  assert(hs->config->verify_mode != SSL_VERIFY_NONE);

  uint8_t alert = SSL_AD_CERTIFICATE_UNKNOWN;

  enum ssl_verify_result_t ret = ssl_verify_invalid;

  if (hs->config->custom_verify_callback != nullptr) {

    ret = hs->config->custom_verify_callback(ssl, &alert);

  }

  if (ret == ssl_verify_invalid) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_CERTIFICATE_VERIFY_FAILED);

    if (send_alert) {

      ssl_send_alert(ssl, SSL3_AL_FATAL, alert);

    }

  }

  return ret;

}

static uint16_t grease_index_to_value(const SSL_HANDSHAKE *hs,

                                      enum ssl_grease_index_t index) {

  // This generates a random value of the form 0xωaωa, for all 0 ≤ ω < 16.

  uint16_t ret = hs->grease_seed[index];

  ret = (ret & 0xf0) | 0x0a;

  ret |= ret << 8;

  return ret;

}

uint16_t ssl_get_grease_value(const SSL_HANDSHAKE *hs,

                              enum ssl_grease_index_t index) {

  uint16_t ret = grease_index_to_value(hs, index);

  if (index == ssl_grease_extension2 &&

      ret == grease_index_to_value(hs, ssl_grease_extension1)) {

    // The two fake extensions must not have the same value. GREASE values are

    // of the form 0x1a1a, 0x2a2a, 0x3a3a, etc., so XOR to generate a different

    // one.

    ret ^= 0x1010;

  }

  return ret;

}

enum ssl_hs_wait_t ssl_get_finished(SSL_HANDSHAKE *hs) {

  SSL *const ssl = hs->ssl;

  SSLMessage msg;

  if (!ssl->method->get_message(ssl, &msg)) {

    return ssl_hs_read_message;

  }

  if (!ssl_check_message_type(ssl, msg, SSL3_MT_FINISHED)) {

    return ssl_hs_error;

  }

  // Snapshot the finished hash before incorporating the new message.

  uint8_t finished[EVP_MAX_MD_SIZE];

  size_t finished_len;

  if (!hs->transcript.GetFinishedMAC(finished, &finished_len,

                                     ssl_handshake_session(hs), !ssl->server) ||

      !ssl_hash_message(hs, msg)) {

    return ssl_hs_error;

  }

  int finished_ok = CBS_mem_equal(&msg.body, finished, finished_len);

#if defined(BORINGSSL_UNSAFE_FUZZER_MODE)

  finished_ok = 1;

#endif

  if (!finished_ok) {

    ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECRYPT_ERROR);

    OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED);

    return ssl_hs_error;

  }

  // Copy the Finished so we can use it for renegotiation checks.

  if (finished_len > sizeof(ssl->s3->previous_client_finished) ||

      finished_len > sizeof(ssl->s3->previous_server_finished)) {

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return ssl_hs_error;

  }

  if (ssl->server) {

    OPENSSL_memcpy(ssl->s3->previous_client_finished, finished, finished_len);

    ssl->s3->previous_client_finished_len = finished_len;

  } else {

    OPENSSL_memcpy(ssl->s3->previous_server_finished, finished, finished_len);

    ssl->s3->previous_server_finished_len = finished_len;

  }

  // The Finished message should be the end of a flight.

  if (ssl->method->has_unprocessed_handshake_data(ssl)) {

    ssl_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);

    OPENSSL_PUT_ERROR(SSL, SSL_R_EXCESS_HANDSHAKE_DATA);

    return ssl_hs_error;

  }

  ssl->method->next_message(ssl);

  return ssl_hs_ok;

}

bool ssl_send_finished(SSL_HANDSHAKE *hs) {

  SSL *const ssl = hs->ssl;

  const SSL_SESSION *session = ssl_handshake_session(hs);

  uint8_t finished[EVP_MAX_MD_SIZE];

  size_t finished_len;

  if (!hs->transcript.GetFinishedMAC(finished, &finished_len, session,

                                     ssl->server)) {

    return false;

  }

  // Log the master secret, if logging is enabled.

  if (!ssl_log_secret(ssl, "CLIENT_RANDOM",

                      MakeConstSpan(session->secret, session->secret_length))) {

    return false;

  }

  // Copy the Finished so we can use it for renegotiation checks.

  if (finished_len > sizeof(ssl->s3->previous_client_finished) ||

      finished_len > sizeof(ssl->s3->previous_server_finished)) {

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return false;

  }

  if (ssl->server) {

    OPENSSL_memcpy(ssl->s3->previous_server_finished, finished, finished_len);

    ssl->s3->previous_server_finished_len = finished_len;

  } else {

    OPENSSL_memcpy(ssl->s3->previous_client_finished, finished, finished_len);

    ssl->s3->previous_client_finished_len = finished_len;

  }

  ScopedCBB cbb;

  CBB body;

  if (!ssl->method->init_message(ssl, cbb.get(), &body, SSL3_MT_FINISHED) ||

      !CBB_add_bytes(&body, finished, finished_len) ||

      !ssl_add_message_cbb(ssl, cbb.get())) {

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return false;

  }

  return true;

}

bool ssl_output_cert_chain(SSL_HANDSHAKE *hs) {

  ScopedCBB cbb;

  CBB body;

  if (!hs->ssl->method->init_message(hs->ssl, cbb.get(), &body,

                                     SSL3_MT_CERTIFICATE) ||

      !ssl_add_cert_chain(hs, &body) ||

      !ssl_add_message_cbb(hs->ssl, cbb.get())) {

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return false;

  }

  return true;

}

const SSL_SESSION *ssl_handshake_session(const SSL_HANDSHAKE *hs) {

  if (hs->new_session) {

    return hs->new_session.get();

  }

  return hs->ssl->session.get();

}

int ssl_run_handshake(SSL_HANDSHAKE *hs, bool *out_early_return) {

  SSL *const ssl = hs->ssl;

  for (;;) {

    // Resolve the operation the handshake was waiting on. Each condition may

    // halt the handshake by returning, or continue executing if the handshake

    // may immediately proceed. Cases which halt the handshake can clear

    // |hs->wait| to re-enter the state machine on the next iteration, or leave

    // it set to keep the condition sticky.

    switch (hs->wait) {

      case ssl_hs_error:

        ERR_restore_state(hs->error.get());

        return -1;

      case ssl_hs_flush: {

        int ret = ssl->method->flush_flight(ssl);

        if (ret <= 0) {

          return ret;

        }

        break;

      }

      case ssl_hs_read_server_hello:

      case ssl_hs_read_message:

      case ssl_hs_read_change_cipher_spec: {

        if (ssl->quic_method) {

          // QUIC has no ChangeCipherSpec messages.

          assert(hs->wait != ssl_hs_read_change_cipher_spec);

          // The caller should call |SSL_provide_quic_data|. Clear |hs->wait| so

          // the handshake can check if there is sufficient data next iteration.

          ssl->s3->rwstate = SSL_ERROR_WANT_READ;

          hs->wait = ssl_hs_ok;

          return -1;

        }

        uint8_t alert = SSL_AD_DECODE_ERROR;

        size_t consumed = 0;

        ssl_open_record_t ret;

        if (hs->wait == ssl_hs_read_change_cipher_spec) {

          ret = ssl_open_change_cipher_spec(ssl, &consumed, &alert,

                                            ssl->s3->read_buffer.span());

        } else {

          ret = ssl_open_handshake(ssl, &consumed, &alert,

                                   ssl->s3->read_buffer.span());

        }

        if (ret == ssl_open_record_error &&

            hs->wait == ssl_hs_read_server_hello) {

          uint32_t err = ERR_peek_error();

          if (ERR_GET_LIB(err) == ERR_LIB_SSL &&

              ERR_GET_REASON(err) == SSL_R_SSLV3_ALERT_HANDSHAKE_FAILURE) {

            // Add a dedicated error code to the queue for a handshake_failure

            // alert in response to ClientHello. This matches NSS's client

            // behavior and gives a better error on a (probable) failure to

            // negotiate initial parameters. Note: this error code comes after

            // the original one.

            //

            // See https://crbug.com/446505.

            OPENSSL_PUT_ERROR(SSL, SSL_R_HANDSHAKE_FAILURE_ON_CLIENT_HELLO);

          }

        }

        bool retry;

        int bio_ret = ssl_handle_open_record(ssl, &retry, ret, consumed, alert);

        if (bio_ret <= 0) {

          return bio_ret;

        }

        if (retry) {

          continue;

        }

        ssl->s3->read_buffer.DiscardConsumed();

        break;

      }

      case ssl_hs_read_end_of_early_data: {

        if (ssl->s3->hs->can_early_read) {

          // While we are processing early data, the handshake returns early.

          *out_early_return = true;

          return 1;

        }

        hs->wait = ssl_hs_ok;

        break;

      }

      case ssl_hs_certificate_selection_pending:

        ssl->s3->rwstate = SSL_ERROR_PENDING_CERTIFICATE;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_handoff:

        ssl->s3->rwstate = SSL_ERROR_HANDOFF;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_handback: {

        int ret = ssl->method->flush_flight(ssl);

        if (ret <= 0) {

          return ret;

        }

        ssl->s3->rwstate = SSL_ERROR_HANDBACK;

        hs->wait = ssl_hs_handback;

        return -1;

      }

        // The following cases are associated with callback APIs which expect to

        // be called each time the state machine runs. Thus they set |hs->wait|

        // to |ssl_hs_ok| so that, next time, we re-enter the state machine and

        // call the callback again.

      case ssl_hs_x509_lookup:

        ssl->s3->rwstate = SSL_ERROR_WANT_X509_LOOKUP;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_private_key_operation:

        ssl->s3->rwstate = SSL_ERROR_WANT_PRIVATE_KEY_OPERATION;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_pending_session:

        ssl->s3->rwstate = SSL_ERROR_PENDING_SESSION;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_pending_ticket:

        ssl->s3->rwstate = SSL_ERROR_PENDING_TICKET;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_certificate_verify:

        ssl->s3->rwstate = SSL_ERROR_WANT_CERTIFICATE_VERIFY;

        hs->wait = ssl_hs_ok;

        return -1;

      case ssl_hs_early_data_rejected:

        assert(ssl->s3->early_data_reason != ssl_early_data_unknown);

        assert(!hs->can_early_write);

        ssl->s3->rwstate = SSL_ERROR_EARLY_DATA_REJECTED;

        return -1;

      case ssl_hs_early_return:

        if (!ssl->server) {

          // On ECH reject, the handshake should never complete.

          assert(ssl->s3->ech_status != ssl_ech_rejected);

        }

        *out_early_return = true;

        hs->wait = ssl_hs_ok;

        return 1;

      case ssl_hs_hints_ready:

        ssl->s3->rwstate = SSL_ERROR_HANDSHAKE_HINTS_READY;

        return -1;

      case ssl_hs_ok:

        break;

    }

    // Run the state machine again.

    hs->wait = ssl->do_handshake(hs);

    if (hs->wait == ssl_hs_error) {

      hs->error.reset(ERR_save_state());

      return -1;

    }

    if (hs->wait == ssl_hs_ok) {

      if (!ssl->server) {

        // On ECH reject, the handshake should never complete.

        assert(ssl->s3->ech_status != ssl_ech_rejected);

      }

      // The handshake has completed.

      *out_early_return = false;

      return 1;

    }

    // Otherwise, loop to the beginning and resolve what was blocking the

    // handshake.

  }

}

BSSL_NAMESPACE_END