ssl/tls13_client.c

/* Copyright (c) 2016, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <openssl/ssl.h>

#include <assert.h>
#include <string.h>

#include <openssl/bytestring.h>
#include <openssl/digest.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/stack.h>
#include <openssl/x509.h>

#include "internal.h"


enum client_hs_state_t {
  state_process_hello_retry_request = 0,
  state_send_second_client_hello,
  state_flush_second_client_hello,
  state_process_server_hello,
  state_process_encrypted_extensions,
  state_process_certificate_request,
  state_process_server_certificate,
  state_process_server_certificate_verify,
  state_process_server_finished,
  state_certificate_callback,
  state_send_client_certificate,
  state_send_client_certificate_verify,
  state_complete_client_certificate_verify,
  state_send_channel_id,
  state_send_client_finished,
  state_flush,
  state_done,
};

static enum ssl_hs_wait_t do_process_hello_retry_request(SSL *ssl,
                                                         SSL_HANDSHAKE *hs) {
  if (ssl->s3->tmp.message_type != SSL3_MT_HELLO_RETRY_REQUEST) {
    hs->state = state_process_server_hello;
    return ssl_hs_ok;
  }

  CBS cbs, extensions;
  uint16_t server_wire_version;
  CBS_init(&cbs, ssl->init_msg, ssl->init_num);
  if (!CBS_get_u16(&cbs, &server_wire_version) ||
      !CBS_get_u16_length_prefixed(&cbs, &extensions) ||
      /* HelloRetryRequest may not be empty. */
      CBS_len(&extensions) == 0 ||
      CBS_len(&cbs) != 0) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    return ssl_hs_error;
  }

  while (CBS_len(&extensions) != 0) {
    uint16_t type;
    CBS extension;
    if (!CBS_get_u16(&extensions, &type) ||
        !CBS_get_u16_length_prefixed(&extensions, &extension)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }

    switch (type) {
      case TLSEXT_TYPE_cookie: {
        if (hs->cookie != NULL) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          return ssl_hs_error;
        }

        /* Cookies may be requested whether or not advertised, so no need to
         * check. */

        CBS cookie;
        if (!CBS_get_u16_length_prefixed(&extension, &cookie) ||
            CBS_len(&cookie) == 0 ||
            CBS_len(&extension) != 0) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
          return ssl_hs_error;
        }

        if (!CBS_stow(&cookie, &hs->cookie, &hs->cookie_len)) {
          return ssl_hs_error;
        }
        break;
      }

      case TLSEXT_TYPE_key_share: {
        if (hs->retry_group != 0) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          return ssl_hs_error;
        }

        /* key_share is always advertised, so no need to check. */

        uint16_t group_id;
        if (!CBS_get_u16(&extension, &group_id) ||
            CBS_len(&extension) != 0) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
          return ssl_hs_error;
        }

        /* The group must be supported. */
        const uint16_t *groups;
        size_t groups_len;
        tls1_get_grouplist(ssl, &groups, &groups_len);
        int found = 0;
        for (size_t i = 0; i < groups_len; i++) {
          if (groups[i] == group_id) {
            found = 1;
            break;
          }
        }

        if (!found) {
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_CURVE);
          return ssl_hs_error;
        }

        /* Check that the HelloRetryRequest does not request the key share that
         * was provided in the initial ClientHello. */
        if (SSL_ECDH_CTX_get_id(&hs->ecdh_ctx) == group_id) {
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_CURVE);
          return ssl_hs_error;
        }

        SSL_ECDH_CTX_cleanup(&hs->ecdh_ctx);
        hs->retry_group = group_id;
        break;
      }

      default:
        OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_EXTENSION);
        ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNSUPPORTED_EXTENSION);
        return ssl_hs_error;
    }
  }

  hs->received_hello_retry_request = 1;
  hs->state = state_send_second_client_hello;
  return ssl_hs_ok;
}

static enum ssl_hs_wait_t do_send_second_client_hello(SSL *ssl,
                                                      SSL_HANDSHAKE *hs) {
  CBB cbb, body;
  if (!ssl->method->init_message(ssl, &cbb, &body, SSL3_MT_CLIENT_HELLO) ||
      !ssl_add_client_hello_body(ssl, &body) ||
      !ssl->method->finish_message(ssl, &cbb)) {
    CBB_cleanup(&cbb);
    return ssl_hs_error;
  }

  hs->state = state_flush_second_client_hello;
  return ssl_hs_write_message;
}

static enum ssl_hs_wait_t do_flush_second_client_hello(SSL *ssl,
                                                       SSL_HANDSHAKE *hs) {
  hs->state = state_process_server_hello;
  return ssl_hs_flush_and_read_message;
}

static enum ssl_hs_wait_t do_process_server_hello(SSL *ssl, SSL_HANDSHAKE *hs) {
  if (!tls13_check_message_type(ssl, SSL3_MT_SERVER_HELLO)) {
    return ssl_hs_error;
  }

  CBS cbs, server_random, extensions;
  uint16_t server_wire_version;
  uint16_t cipher_suite;
  CBS_init(&cbs, ssl->init_msg, ssl->init_num);
  if (!CBS_get_u16(&cbs, &server_wire_version) ||
      !CBS_get_bytes(&cbs, &server_random, SSL3_RANDOM_SIZE) ||
      !CBS_get_u16(&cbs, &cipher_suite) ||
      !CBS_get_u16_length_prefixed(&cbs, &extensions) ||
      CBS_len(&cbs) != 0) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    return ssl_hs_error;
  }

  if (server_wire_version != ssl->version) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_VERSION_NUMBER);
    return ssl_hs_error;
  }

  assert(ssl->s3->have_version);
  memcpy(ssl->s3->server_random, CBS_data(&server_random), SSL3_RANDOM_SIZE);

  const SSL_CIPHER *cipher = SSL_get_cipher_by_value(cipher_suite);
  if (cipher == NULL) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_UNKNOWN_CIPHER_RETURNED);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
    return ssl_hs_error;
  }

  /* Check if the cipher is disabled. */
  if ((cipher->algorithm_mkey & ssl->cert->mask_k) ||
      (cipher->algorithm_auth & ssl->cert->mask_a) ||
      SSL_CIPHER_get_min_version(cipher) > ssl3_protocol_version(ssl) ||
      SSL_CIPHER_get_max_version(cipher) < ssl3_protocol_version(ssl) ||
      !sk_SSL_CIPHER_find(ssl_get_ciphers_by_id(ssl), NULL, cipher)) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_CIPHER_RETURNED);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
    return ssl_hs_error;
  }

  /* Parse out the extensions. */
  int have_key_share = 0, have_pre_shared_key = 0, have_sigalgs = 0;
  CBS key_share, pre_shared_key, sigalgs;
  while (CBS_len(&extensions) != 0) {
    uint16_t type;
    CBS extension;
    if (!CBS_get_u16(&extensions, &type) ||
        !CBS_get_u16_length_prefixed(&extensions, &extension)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_PARSE_TLSEXT);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }

    switch (type) {
      case TLSEXT_TYPE_key_share:
        if (have_key_share) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          return ssl_hs_error;
        }
        key_share = extension;
        have_key_share = 1;
        break;
      case TLSEXT_TYPE_pre_shared_key:
        if (have_pre_shared_key) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          return ssl_hs_error;
        }
        pre_shared_key = extension;
        have_pre_shared_key = 1;
        break;
      case TLSEXT_TYPE_signature_algorithms:
        if (have_sigalgs) {
          OPENSSL_PUT_ERROR(SSL, SSL_R_DUPLICATE_EXTENSION);
          ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
          return ssl_hs_error;
        }
        sigalgs = extension;
        have_sigalgs = 1;
        break;
      default:
        OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_EXTENSION);
        ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNSUPPORTED_EXTENSION);
        return ssl_hs_error;
    }
  }

  /* We only support PSK_AUTH and PSK_DHE_KE. */
  if (!have_key_share || have_sigalgs == have_pre_shared_key) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_EXTENSION);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
    return ssl_hs_error;
  }

  uint8_t alert = SSL_AD_DECODE_ERROR;
  if (have_pre_shared_key) {
    if (ssl->session == NULL) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_EXTENSION);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNSUPPORTED_EXTENSION);
      return ssl_hs_error;
    }

    if (!ssl_ext_pre_shared_key_parse_serverhello(ssl, &alert,
                                                  &pre_shared_key)) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
      return ssl_hs_error;
    }

    if (ssl->session->ssl_version != ssl->version) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_OLD_SESSION_VERSION_NOT_RETURNED);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
      return ssl_hs_error;
    }

    if (ssl->session->cipher != cipher) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_OLD_SESSION_CIPHER_NOT_RETURNED);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
      return ssl_hs_error;
    }

    if (!ssl_session_is_context_valid(ssl, ssl->session)) {
      /* This is actually a client application bug. */
      OPENSSL_PUT_ERROR(SSL,
                        SSL_R_ATTEMPT_TO_REUSE_SESSION_IN_DIFFERENT_CONTEXT);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
      return ssl_hs_error;
    }

    ssl->s3->session_reused = 1;
    /* Only authentication information carries over in TLS 1.3. */
    ssl->s3->new_session =
        SSL_SESSION_dup(ssl->session, SSL_SESSION_DUP_AUTH_ONLY);
    if (ssl->s3->new_session == NULL) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
      return ssl_hs_error;
    }
    ssl_set_session(ssl, NULL);
  } else if (!ssl_get_new_session(ssl, 0)) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
    return ssl_hs_error;
  }

  ssl->s3->new_session->cipher = cipher;
  ssl->s3->tmp.new_cipher = cipher;

  /* The PRF hash is now known. Set up the key schedule. */
  size_t hash_len =
      EVP_MD_size(ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)));

  /* Derive resumption material. */
  uint8_t resumption_ctx[EVP_MAX_MD_SIZE] = {0};
  uint8_t psk_secret[EVP_MAX_MD_SIZE] = {0};
  if (ssl->s3->session_reused) {
    if (!tls13_resumption_context(ssl, resumption_ctx, hash_len,
                                  ssl->s3->new_session) ||
        !tls13_resumption_psk(ssl, psk_secret, hash_len,
                              ssl->s3->new_session)) {
      return ssl_hs_error;
    }
  }

  /* Set up the key schedule, hash in the ClientHello, and incorporate the PSK
   * into the running secret. */
  if (!tls13_init_key_schedule(ssl, resumption_ctx, hash_len) ||
      !tls13_advance_key_schedule(ssl, psk_secret, hash_len)) {
    return ssl_hs_error;
  }

  /* Resolve ECDHE and incorporate it into the secret. */
  uint8_t *dhe_secret;
  size_t dhe_secret_len;
  if (!ssl_ext_key_share_parse_serverhello(ssl, &dhe_secret, &dhe_secret_len,
                                           &alert, &key_share)) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
    return ssl_hs_error;
  }

  if (!tls13_advance_key_schedule(ssl, dhe_secret, dhe_secret_len)) {
    OPENSSL_free(dhe_secret);
    return ssl_hs_error;
  }
  OPENSSL_free(dhe_secret);

  if (have_sigalgs &&
      CBS_len(&sigalgs) != 0) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    return ssl_hs_error;
  }

  /* If there was no HelloRetryRequest, the version negotiation logic has
   * already hashed the message. */
  if (hs->received_hello_retry_request &&
      !ssl->method->hash_current_message(ssl)) {
    return ssl_hs_error;
  }

  if (!tls13_set_handshake_traffic(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_process_encrypted_extensions;
  return ssl_hs_read_message;
}

static enum ssl_hs_wait_t do_process_encrypted_extensions(SSL *ssl,
                                                          SSL_HANDSHAKE *hs) {
  if (!tls13_check_message_type(ssl, SSL3_MT_ENCRYPTED_EXTENSIONS)) {
    return ssl_hs_error;
  }

  CBS cbs;
  CBS_init(&cbs, ssl->init_msg, ssl->init_num);
  if (!ssl_parse_serverhello_tlsext(ssl, &cbs)) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_PARSE_TLSEXT);
    return ssl_hs_error;
  }
  if (CBS_len(&cbs) != 0) {
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    return ssl_hs_error;
  }

  if (!ssl->method->hash_current_message(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_process_certificate_request;
  return ssl_hs_read_message;
}

static enum ssl_hs_wait_t do_process_certificate_request(SSL *ssl,
                                                         SSL_HANDSHAKE *hs) {
  /* CertificateRequest may only be sent in non-resumption handshakes. */
  if (ssl->s3->session_reused) {
    hs->state = state_process_server_finished;
    return ssl_hs_ok;
  }

  /* CertificateRequest is optional. */
  if (ssl->s3->tmp.message_type != SSL3_MT_CERTIFICATE_REQUEST) {
    hs->state = state_process_server_certificate;
    return ssl_hs_ok;
  }

  CBS cbs, context, supported_signature_algorithms;
  CBS_init(&cbs, ssl->init_msg, ssl->init_num);
  if (!CBS_get_u8_length_prefixed(&cbs, &context) ||
      /* The request context is always empty during the handshake. */
      CBS_len(&context) != 0 ||
      !CBS_get_u16_length_prefixed(&cbs, &supported_signature_algorithms) ||
      CBS_len(&supported_signature_algorithms) == 0 ||
      !tls1_parse_peer_sigalgs(ssl, &supported_signature_algorithms)) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    return ssl_hs_error;
  }

  uint8_t alert;
  STACK_OF(X509_NAME) *ca_sk = ssl_parse_client_CA_list(ssl, &alert, &cbs);
  if (ca_sk == NULL) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
    return ssl_hs_error;
  }

  /* Ignore extensions. */
  CBS extensions;
  if (!CBS_get_u16_length_prefixed(&cbs, &extensions) ||
      CBS_len(&cbs) != 0) {
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    sk_X509_NAME_pop_free(ca_sk, X509_NAME_free);
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    return ssl_hs_error;
  }

  ssl->s3->hs->cert_request = 1;
  sk_X509_NAME_pop_free(ssl->s3->hs->ca_names, X509_NAME_free);
  ssl->s3->hs->ca_names = ca_sk;

  if (!ssl->method->hash_current_message(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_process_server_certificate;
  return ssl_hs_read_message;
}

static enum ssl_hs_wait_t do_process_server_certificate(SSL *ssl,
                                                        SSL_HANDSHAKE *hs) {
  if (!tls13_check_message_type(ssl, SSL3_MT_CERTIFICATE) ||
      !tls13_process_certificate(ssl, 0 /* certificate required */) ||
      !ssl->method->hash_current_message(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_process_server_certificate_verify;
  return ssl_hs_read_message;
}

static enum ssl_hs_wait_t do_process_server_certificate_verify(
    SSL *ssl, SSL_HANDSHAKE *hs) {
  if (!tls13_check_message_type(ssl, SSL3_MT_CERTIFICATE_VERIFY) ||
      !tls13_process_certificate_verify(ssl) ||
      !ssl->method->hash_current_message(ssl)) {
    return 0;
  }

  hs->state = state_process_server_finished;
  return ssl_hs_read_message;
}

static enum ssl_hs_wait_t do_process_server_finished(SSL *ssl,
                                                     SSL_HANDSHAKE *hs) {
  static const uint8_t kZeroes[EVP_MAX_MD_SIZE] = {0};
  if (!tls13_check_message_type(ssl, SSL3_MT_FINISHED) ||
      !tls13_process_finished(ssl) ||
      !ssl->method->hash_current_message(ssl) ||
      /* Update the secret to the master secret and derive traffic keys. */
      !tls13_advance_key_schedule(ssl, kZeroes, hs->hash_len) ||
      !tls13_derive_traffic_secret_0(ssl)) {
    return ssl_hs_error;
  }

  ssl->method->received_flight(ssl);
  hs->state = state_certificate_callback;
  return ssl_hs_ok;
}

static enum ssl_hs_wait_t do_certificate_callback(SSL *ssl, SSL_HANDSHAKE *hs) {
  /* The peer didn't request a certificate. */
  if (!ssl->s3->hs->cert_request) {
    hs->state = state_send_channel_id;
    return ssl_hs_ok;
  }

  /* Call cert_cb to update the certificate. */
  if (ssl->cert->cert_cb != NULL) {
    int rv = ssl->cert->cert_cb(ssl, ssl->cert->cert_cb_arg);
    if (rv == 0) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
      OPENSSL_PUT_ERROR(SSL, SSL_R_CERT_CB_ERROR);
      return ssl_hs_error;
    }
    if (rv < 0) {
      hs->state = state_certificate_callback;
      return ssl_hs_x509_lookup;
    }
  }

  hs->state = state_send_client_certificate;
  return ssl_hs_ok;
}

static enum ssl_hs_wait_t do_send_client_certificate(SSL *ssl,
                                                     SSL_HANDSHAKE *hs) {
  /* Call client_cert_cb to update the certificate. */
  int should_retry;
  if (!ssl_do_client_cert_cb(ssl, &should_retry)) {
    if (should_retry) {
      hs->state = state_send_client_certificate;
      return ssl_hs_x509_lookup;
    }
    return ssl_hs_error;
  }

  if (!tls13_prepare_certificate(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_send_client_certificate_verify;
  return ssl_hs_write_message;
}

static enum ssl_hs_wait_t do_send_client_certificate_verify(SSL *ssl,
                                                            SSL_HANDSHAKE *hs,
                                                            int is_first_run) {
  /* Don't send CertificateVerify if there is no certificate. */
  if (!ssl_has_certificate(ssl)) {
    hs->state = state_send_channel_id;
    return ssl_hs_ok;
  }

  switch (tls13_prepare_certificate_verify(ssl, is_first_run)) {
    case ssl_private_key_success:
      hs->state = state_send_channel_id;
      return ssl_hs_write_message;

    case ssl_private_key_retry:
      hs->state = state_complete_client_certificate_verify;
      return ssl_hs_private_key_operation;

    case ssl_private_key_failure:
      return ssl_hs_error;
  }

  assert(0);
  return ssl_hs_error;
}

static enum ssl_hs_wait_t do_send_channel_id(SSL *ssl, SSL_HANDSHAKE *hs) {
  if (!ssl->s3->tlsext_channel_id_valid) {
    hs->state = state_send_client_finished;
    return ssl_hs_ok;
  }

  if (!ssl_do_channel_id_callback(ssl)) {
    return ssl_hs_error;
  }

  if (ssl->tlsext_channel_id_private == NULL) {
    return ssl_hs_channel_id_lookup;
  }

  CBB cbb, body;
  if (!ssl->method->init_message(ssl, &cbb, &body, SSL3_MT_CHANNEL_ID) ||
      !tls1_write_channel_id(ssl, &body) ||
      !ssl->method->finish_message(ssl, &cbb)) {
    CBB_cleanup(&cbb);
    return ssl_hs_error;
  }

  hs->state = state_send_client_finished;
  return ssl_hs_write_message;
}

static enum ssl_hs_wait_t do_send_client_finished(SSL *ssl, SSL_HANDSHAKE *hs) {
  if (!tls13_prepare_finished(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_flush;
  return ssl_hs_write_message;
}

static enum ssl_hs_wait_t do_flush(SSL *ssl, SSL_HANDSHAKE *hs) {
  if (!tls13_set_traffic_key(ssl, type_data, evp_aead_open,
                             hs->server_traffic_secret_0, hs->hash_len) ||
      !tls13_set_traffic_key(ssl, type_data, evp_aead_seal,
                             hs->client_traffic_secret_0, hs->hash_len) ||
      !tls13_finalize_keys(ssl)) {
    return ssl_hs_error;
  }

  hs->state = state_done;
  return ssl_hs_flush;
}

enum ssl_hs_wait_t tls13_client_handshake(SSL *ssl) {
  SSL_HANDSHAKE *hs = ssl->s3->hs;

  while (hs->state != state_done) {
    enum ssl_hs_wait_t ret = ssl_hs_error;
    enum client_hs_state_t state = hs->state;
    switch (state) {
      case state_process_hello_retry_request:
        ret = do_process_hello_retry_request(ssl, hs);
        break;
      case state_send_second_client_hello:
        ret = do_send_second_client_hello(ssl, hs);
        break;
      case state_flush_second_client_hello:
        ret = do_flush_second_client_hello(ssl, hs);
        break;
      case state_process_server_hello:
        ret = do_process_server_hello(ssl, hs);
        break;
      case state_process_encrypted_extensions:
        ret = do_process_encrypted_extensions(ssl, hs);
        break;
      case state_process_certificate_request:
        ret = do_process_certificate_request(ssl, hs);
        break;
      case state_process_server_certificate:
        ret = do_process_server_certificate(ssl, hs);
        break;
      case state_process_server_certificate_verify:
        ret = do_process_server_certificate_verify(ssl, hs);
        break;
      case state_process_server_finished:
        ret = do_process_server_finished(ssl, hs);
        break;
      case state_certificate_callback:
        ret = do_certificate_callback(ssl, hs);
        break;
      case state_send_client_certificate:
        ret = do_send_client_certificate(ssl, hs);
        break;
      case state_send_client_certificate_verify:
        ret = do_send_client_certificate_verify(ssl, hs, 1 /* first run */);
        break;
      case state_complete_client_certificate_verify:
        ret = do_send_client_certificate_verify(ssl, hs, 0 /* complete */);
        break;
      case state_send_channel_id:
        ret = do_send_channel_id(ssl, hs);
        break;
      case state_send_client_finished:
        ret = do_send_client_finished(ssl, hs);
        break;
      case state_flush:
        ret = do_flush(ssl, hs);
        break;
      case state_done:
        ret = ssl_hs_ok;
        break;
    }

    if (ret != ssl_hs_ok) {
      return ret;
    }
  }

  return ssl_hs_ok;
}

int tls13_process_new_session_ticket(SSL *ssl) {
  SSL_SESSION *session =
      SSL_SESSION_dup(ssl->s3->established_session,
                      SSL_SESSION_INCLUDE_NONAUTH);
  if (session == NULL) {
    return 0;
  }

  CBS cbs, ke_modes, auth_modes, ticket, extensions;
  CBS_init(&cbs, ssl->init_msg, ssl->init_num);
  if (!CBS_get_u32(&cbs, &session->tlsext_tick_lifetime_hint) ||
      !CBS_get_u8_length_prefixed(&cbs, &ke_modes) ||
      CBS_len(&ke_modes) == 0 ||
      !CBS_get_u8_length_prefixed(&cbs, &auth_modes) ||
      CBS_len(&auth_modes) == 0 ||
      !CBS_get_u16_length_prefixed(&cbs, &ticket) ||
      !CBS_stow(&ticket, &session->tlsext_tick, &session->tlsext_ticklen) ||
      !CBS_get_u16_length_prefixed(&cbs, &extensions) ||
      CBS_len(&cbs) != 0) {
    SSL_SESSION_free(session);
    ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
    return 0;
  }

  session->not_resumable = 0;

  /* Ignore the ticket unless the server preferences are compatible with us. */
  if (memchr(CBS_data(&ke_modes), SSL_PSK_DHE_KE, CBS_len(&ke_modes)) != NULL &&
      memchr(CBS_data(&auth_modes), SSL_PSK_AUTH, CBS_len(&auth_modes)) !=
          NULL &&
      ssl->ctx->new_session_cb != NULL &&
      ssl->ctx->new_session_cb(ssl, session)) {
    /* |new_session_cb|'s return value signals that it took ownership. */
    return 1;
  }

  SSL_SESSION_free(session);
  return 1;
}

void ssl_clear_tls13_state(SSL *ssl) {
  SSL_ECDH_CTX_cleanup(&ssl->s3->hs->ecdh_ctx);

  OPENSSL_free(ssl->s3->hs->key_share_bytes);
  ssl->s3->hs->key_share_bytes = NULL;
  ssl->s3->hs->key_share_bytes_len = 0;
}