text: /* 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/rand.h>
  #include <openssl/stack.h>
  
  #include "internal.h"
  
  
  enum server_hs_state_t {
    state_process_client_hello = 0,
    state_send_hello_retry_request,
    state_flush_hello_retry_request,
    state_process_second_client_hello,
    state_send_server_hello,
    state_send_encrypted_extensions,
    state_send_certificate_request,
    state_send_server_certificate,
    state_send_server_certificate_verify,
    state_complete_server_certificate_verify,
    state_send_server_finished,
    state_flush,
    state_process_client_certificate,
    state_process_client_certificate_verify,
    state_process_client_finished,
    state_done,
  };
  
  static const uint8_t kZeroes[EVP_MAX_MD_SIZE] = {0};
  
  static int resolve_psk_secret(SSL *ssl) {
    SSL_HANDSHAKE *hs = ssl->s3->hs;
  
    if (ssl->s3->tmp.new_cipher->algorithm_auth != SSL_aPSK) {
      return tls13_advance_key_schedule(ssl, kZeroes, hs->hash_len);
    }
  
    /* TODO(davidben): Support PSK. */
    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
    return 0;
  }
  
  static int resolve_ecdhe_secret(SSL *ssl, int *out_need_retry,
                                  struct ssl_early_callback_ctx *early_ctx) {
    *out_need_retry = 0;
    SSL_HANDSHAKE *hs = ssl->s3->hs;
  
    if (ssl->s3->tmp.new_cipher->algorithm_mkey != SSL_kECDHE) {
      return tls13_advance_key_schedule(ssl, kZeroes, hs->hash_len);
    }
  
    const uint8_t *key_share_buf = NULL;
    size_t key_share_len = 0;
    CBS key_share;
    if (!SSL_early_callback_ctx_extension_get(early_ctx, TLSEXT_TYPE_key_share,
                                              &key_share_buf, &key_share_len)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_MISSING_KEY_SHARE);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_MISSING_EXTENSION);
      return ssl_hs_error;
    }
  
    CBS_init(&key_share, key_share_buf, key_share_len);
    int found_key_share;
    uint8_t *dhe_secret;
    size_t dhe_secret_len;
    uint8_t alert;
    if (!ext_key_share_parse_clienthello(ssl, &found_key_share, &dhe_secret,
                                         &dhe_secret_len, &alert, &key_share)) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, alert);
      return 0;
    }
  
    if (!found_key_share) {
      *out_need_retry = 1;
      return 0;
    }
  
    int ok = tls13_advance_key_schedule(ssl, dhe_secret, dhe_secret_len);
    OPENSSL_free(dhe_secret);
    return ok;
  }
  
  static enum ssl_hs_wait_t do_process_client_hello(SSL *ssl, SSL_HANDSHAKE *hs) {
    if (!tls13_check_message_type(ssl, SSL3_MT_CLIENT_HELLO)) {
      return ssl_hs_error;
    }
  
    struct ssl_early_callback_ctx early_ctx;
    if (!ssl_early_callback_init(ssl, &early_ctx, ssl->init_msg,
                                 ssl->init_num)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }
  
    CBS cbs, client_random, session_id, cipher_suites, compression_methods;
    uint16_t client_wire_version;
    CBS_init(&cbs, ssl->init_msg, ssl->init_num);
    if (!CBS_get_u16(&cbs, &client_wire_version) ||
        !CBS_get_bytes(&cbs, &client_random, SSL3_RANDOM_SIZE) ||
        !CBS_get_u8_length_prefixed(&cbs, &session_id) ||
        CBS_len(&session_id) > SSL_MAX_SSL_SESSION_ID_LENGTH) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }
  
    uint16_t min_version, max_version;
    if (!ssl_get_version_range(ssl, &min_version, &max_version)) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
      return ssl_hs_error;
    }
  
    assert(ssl->s3->have_version);
  
    /* Load the client random. */
    memcpy(ssl->s3->client_random, CBS_data(&client_random), SSL3_RANDOM_SIZE);
  
    ssl->hit = 0;
    if (!ssl_get_new_session(ssl, 1 /* server */)) {
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
      return ssl_hs_error;
    }
  
    if (ssl->ctx->dos_protection_cb != NULL &&
        ssl->ctx->dos_protection_cb(&early_ctx) == 0) {
      /* Connection rejected for DOS reasons. */
      OPENSSL_PUT_ERROR(SSL, SSL_R_CONNECTION_REJECTED);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ACCESS_DENIED);
      return ssl_hs_error;
    }
  
    if (!CBS_get_u16_length_prefixed(&cbs, &cipher_suites) ||
        CBS_len(&cipher_suites) == 0 ||
        CBS_len(&cipher_suites) % 2 != 0 ||
        !CBS_get_u8_length_prefixed(&cbs, &compression_methods) ||
        CBS_len(&compression_methods) == 0) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }
  
    /* TLS 1.3 requires the peer only advertise the null compression. */
    if (CBS_len(&compression_methods) != 1 ||
        CBS_data(&compression_methods)[0] != 0) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_INVALID_COMPRESSION_LIST);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
      return ssl_hs_error;
    }
  
    /* TLS extensions. */
    if (!ssl_parse_clienthello_tlsext(ssl, &cbs)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_PARSE_TLSEXT);
      return ssl_hs_error;
    }
  
    /* There should be nothing left over in the message. */
    if (CBS_len(&cbs) != 0) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_PACKET_LENGTH);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }
  
    /* Let cert callback update server certificates if required.
     *
     * TODO(davidben): Can this get run earlier? */
    if (ssl->cert->cert_cb != NULL) {
      int rv = ssl->cert->cert_cb(ssl, ssl->cert->cert_cb_arg);
      if (rv == 0) {
        OPENSSL_PUT_ERROR(SSL, SSL_R_CERT_CB_ERROR);
        ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_INTERNAL_ERROR);
        return ssl_hs_error;
      }
      if (rv < 0) {
        hs->state = state_process_client_hello;
        return ssl_hs_x509_lookup;
      }
    }
  
    STACK_OF(SSL_CIPHER) *ciphers =
        ssl_bytes_to_cipher_list(ssl, &cipher_suites, max_version);
    if (ciphers == NULL) {
      return ssl_hs_error;
    }
  
    const SSL_CIPHER *cipher =
        ssl3_choose_cipher(ssl, ciphers, ssl_get_cipher_preferences(ssl));
    sk_SSL_CIPHER_free(ciphers);
    if (cipher == NULL) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_NO_SHARED_CIPHER);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
      return ssl_hs_error;
    }
  
    ssl->session->cipher = cipher;
    ssl->s3->tmp.new_cipher = cipher;
  
    /* The PRF hash is now known. Set up the key schedule and hash the
     * ClientHello. */
    size_t hash_len =
        EVP_MD_size(ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)));
    if (!tls13_init_key_schedule(ssl, kZeroes, hash_len)) {
      return ssl_hs_error;
    }
  
    /* Resolve PSK and incorporate it into the secret. */
    if (!resolve_psk_secret(ssl)) {
      return ssl_hs_error;
    }
  
    /* Resolve ECDHE and incorporate it into the secret. */
    int need_retry;
    if (!resolve_ecdhe_secret(ssl, &need_retry, &early_ctx)) {
      if (need_retry) {
        hs->state = state_send_hello_retry_request;
        return ssl_hs_ok;
      }
      return ssl_hs_error;
    }
  
    hs->state = state_send_server_hello;
    return ssl_hs_ok;
  }
  
  static enum ssl_hs_wait_t do_send_hello_retry_request(SSL *ssl,
                                                        SSL_HANDSHAKE *hs) {
    CBB cbb, body, extensions;
    uint16_t group_id;
    if (!ssl->method->init_message(ssl, &cbb, &body,
                                   SSL3_MT_HELLO_RETRY_REQUEST) ||
        !CBB_add_u16(&body, ssl->version) ||
        !CBB_add_u16(&body, ssl_cipher_get_value(ssl->s3->tmp.new_cipher)) ||
        !tls1_get_shared_group(ssl, &group_id) ||
        !CBB_add_u16(&body, group_id) ||
        !CBB_add_u16_length_prefixed(&body, &extensions) ||
        !ssl->method->finish_message(ssl, &cbb)) {
      CBB_cleanup(&cbb);
      return ssl_hs_error;
    }
  
    hs->state = state_flush_hello_retry_request;
    return ssl_hs_write_message;
  }
  
  static enum ssl_hs_wait_t do_flush_hello_retry_request(SSL *ssl,
                                                         SSL_HANDSHAKE *hs) {
    hs->state = state_process_second_client_hello;
    return ssl_hs_flush_and_read_message;
  }
  
  static enum ssl_hs_wait_t do_process_second_client_hello(SSL *ssl,
                                                        SSL_HANDSHAKE *hs) {
    if (!tls13_check_message_type(ssl, SSL3_MT_CLIENT_HELLO)) {
      return ssl_hs_error;
    }
  
    struct ssl_early_callback_ctx early_ctx;
    if (!ssl_early_callback_init(ssl, &early_ctx, ssl->init_msg,
                                 ssl->init_num)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_CLIENTHELLO_PARSE_FAILED);
      ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
      return ssl_hs_error;
    }
  
    int need_retry;
    if (!resolve_ecdhe_secret(ssl, &need_retry, &early_ctx)) {
      if (need_retry) {
        /* Only send one HelloRetryRequest. */
        ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
        OPENSSL_PUT_ERROR(SSL, SSL_R_WRONG_CURVE);
      }
      return ssl_hs_error;
    }
  
    if (!ssl->method->hash_current_message(ssl)) {
      return ssl_hs_error;
    }
  
    hs->state = state_send_server_hello;
    return ssl_hs_ok;
  }
  
  static enum ssl_hs_wait_t do_send_server_hello(SSL *ssl, SSL_HANDSHAKE *hs) {
    CBB cbb, body, extensions;
    if (!ssl->method->init_message(ssl, &cbb, &body, SSL3_MT_SERVER_HELLO) ||
        !CBB_add_u16(&body, ssl->version) ||
        !RAND_bytes(ssl->s3->server_random, sizeof(ssl->s3->server_random)) ||
        !CBB_add_bytes(&body, ssl->s3->server_random, SSL3_RANDOM_SIZE) ||
        !CBB_add_u16(&body, ssl_cipher_get_value(ssl->s3->tmp.new_cipher)) ||
        !CBB_add_u16_length_prefixed(&body, &extensions) ||
        !ext_key_share_add_serverhello(ssl, &extensions) ||
        !ssl->method->finish_message(ssl, &cbb)) {
      CBB_cleanup(&cbb);
      return ssl_hs_error;
    }
  
    hs->state = state_send_encrypted_extensions;
    return ssl_hs_write_message;
  }
  
  static enum ssl_hs_wait_t do_send_encrypted_extensions(SSL *ssl,
                                                         SSL_HANDSHAKE *hs) {
    if (!tls13_set_handshake_traffic(ssl)) {
      return ssl_hs_error;
    }
  
    CBB cbb, body;
    if (!ssl->method->init_message(ssl, &cbb, &body,
                                   SSL3_MT_ENCRYPTED_EXTENSIONS) ||
        !ssl_add_serverhello_tlsext(ssl, &body) ||
        !ssl->method->finish_message(ssl, &cbb)) {
      CBB_cleanup(&cbb);
      return ssl_hs_error;
    }
  
    hs->state = state_send_certificate_request;
    return ssl_hs_write_message;
  }
  
  static enum ssl_hs_wait_t do_send_certificate_request(SSL *ssl,
                                                        SSL_HANDSHAKE *hs) {
    /* Determine whether to request a client certificate. */
    ssl->s3->tmp.cert_request = !!(ssl->verify_mode & SSL_VERIFY_PEER);
    /* CertificateRequest may only be sent in certificate-based ciphers. */
    if (!ssl_cipher_uses_certificate_auth(ssl->s3->tmp.new_cipher)) {
      ssl->s3->tmp.cert_request = 0;
    }
  
    if (!ssl->s3->tmp.cert_request) {
      /* Skip this state. */
      hs->state = state_send_server_certificate;
      return ssl_hs_ok;
    }
  
    CBB cbb, body, sigalgs_cbb;
    if (!ssl->method->init_message(ssl, &cbb, &body,
                                   SSL3_MT_CERTIFICATE_REQUEST) ||
        !CBB_add_u8(&body, 0 /* no certificate_request_context. */)) {
      goto err;
    }
  
    const uint16_t *sigalgs;
    size_t sigalgs_len = tls12_get_psigalgs(ssl, &sigalgs);
    if (!CBB_add_u16_length_prefixed(&body, &sigalgs_cbb)) {
      goto err;
    }
  
    for (size_t i = 0; i < sigalgs_len; i++) {
      if (!CBB_add_u16(&sigalgs_cbb, sigalgs[i])) {
        goto err;
      }
    }
  
    if (!ssl_add_client_CA_list(ssl, &body) ||
        !CBB_add_u16(&body, 0 /* empty certificate_extensions. */) ||
        !ssl->method->finish_message(ssl, &cbb)) {
      goto err;
    }
  
    hs->state = state_send_server_certificate;
    return ssl_hs_write_message;
  
  err:
    CBB_cleanup(&cbb);
    return ssl_hs_error;
  }
  
  static enum ssl_hs_wait_t do_send_server_certificate(SSL *ssl,
                                                       SSL_HANDSHAKE *hs) {
    if (!ssl_cipher_uses_certificate_auth(ssl->s3->tmp.new_cipher)) {
      hs->state = state_send_server_finished;
      return ssl_hs_ok;
    }
  
    if (!ssl_has_certificate(ssl)) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_NO_CERTIFICATE_SET);
      return ssl_hs_error;
    }
  
    if (!tls13_prepare_certificate(ssl)) {
      return ssl_hs_error;
    }
  
    hs->state = state_send_server_certificate_verify;
    return ssl_hs_write_message;
  }
  
  static enum ssl_hs_wait_t do_send_server_certificate_verify(SSL *ssl,
                                                              SSL_HANDSHAKE *hs,
                                                              int is_first_run) {
    switch (tls13_prepare_certificate_verify(ssl, is_first_run)) {
      case ssl_private_key_success:
        hs->state = state_send_server_finished;
        return ssl_hs_write_message;
  
      case ssl_private_key_retry:
        hs->state = state_complete_server_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_server_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) {
    /* Update the secret to the master secret and derive traffic keys. */
    if (!tls13_advance_key_schedule(ssl, kZeroes, hs->hash_len) ||
        !tls13_derive_traffic_secret_0(ssl) ||
        !tls13_set_traffic_key(ssl, type_data, evp_aead_seal,
                               hs->traffic_secret_0, hs->hash_len)) {
      return ssl_hs_error;
    }
  
    hs->state = state_process_client_certificate;
    return ssl_hs_flush_and_read_message;
  }
  
  static enum ssl_hs_wait_t do_process_client_certificate(SSL *ssl,
                                                          SSL_HANDSHAKE *hs) {
    if (!ssl->s3->tmp.cert_request) {
      /* Skip this state. */
      hs->state = state_process_client_certificate_verify;
      return ssl_hs_ok;
    }
  
    if (!tls13_check_message_type(ssl, SSL3_MT_CERTIFICATE) ||
        !tls13_process_certificate(ssl) ||
        !ssl->method->hash_current_message(ssl)) {
      return ssl_hs_error;
    }
  
    hs->state = state_process_client_certificate_verify;
    return ssl_hs_read_message;
  }
  
  static enum ssl_hs_wait_t do_process_client_certificate_verify(
      SSL *ssl, SSL_HANDSHAKE *hs) {
    if (ssl->session->peer == NULL) {
      /* Skip this state. */
      hs->state = state_process_client_finished;
      return ssl_hs_ok;
    }
  
    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_client_finished;
    return ssl_hs_read_message;
  }
  
  static enum ssl_hs_wait_t do_process_client_finished(SSL *ssl,
                                                       SSL_HANDSHAKE *hs) {
    if (!tls13_check_message_type(ssl, SSL3_MT_FINISHED) ||
        !tls13_process_finished(ssl) ||
        !ssl->method->hash_current_message(ssl) ||
        /* evp_aead_seal keys have already been switched. */
        !tls13_set_traffic_key(ssl, type_data, evp_aead_open,
                               hs->traffic_secret_0, hs->hash_len) ||
        !tls13_finalize_keys(ssl)) {
      return ssl_hs_error;
    }
  
    hs->state = state_done;
    return ssl_hs_ok;
  }
  
  enum ssl_hs_wait_t tls13_server_handshake(SSL *ssl) {
    SSL_HANDSHAKE *hs = ssl->s3->hs;
  
    while (hs->state != state_done) {
      enum ssl_hs_wait_t ret = ssl_hs_error;
      enum server_hs_state_t state = hs->state;
      switch (state) {
        case state_process_client_hello:
          ret = do_process_client_hello(ssl, hs);
          break;
        case state_send_hello_retry_request:
          ret = do_send_hello_retry_request(ssl, hs);
          break;
        case state_flush_hello_retry_request:
          ret = do_flush_hello_retry_request(ssl, hs);
          break;
        case state_process_second_client_hello:
          ret = do_process_second_client_hello(ssl, hs);
          break;
        case state_send_server_hello:
          ret = do_send_server_hello(ssl, hs);
          break;
        case state_send_encrypted_extensions:
          ret = do_send_encrypted_extensions(ssl, hs);
          break;
        case state_send_certificate_request:
          ret = do_send_certificate_request(ssl, hs);
          break;
        case state_send_server_certificate:
          ret = do_send_server_certificate(ssl, hs);
          break;
        case state_send_server_certificate_verify:
          ret = do_send_server_certificate_verify(ssl, hs, 1 /* first run */);
        break;
        case state_complete_server_certificate_verify:
          ret = do_send_server_certificate_verify(ssl, hs, 0 /* complete */);
        break;
        case state_send_server_finished:
          ret = do_send_server_finished(ssl, hs);
          break;
        case state_flush:
          ret = do_flush(ssl, hs);
          break;
        case state_process_client_certificate:
          ret = do_process_client_certificate(ssl, hs);
          break;
        case state_process_client_certificate_verify:
          ret = do_process_client_certificate_verify(ssl, hs);
          break;
        case state_process_client_finished:
          ret = do_process_client_finished(ssl, hs);
          break;
        case state_done:
          ret = ssl_hs_ok;
          break;
      }
  
      if (ret != ssl_hs_ok) {
        return ret;
      }
    }
  
    return ssl_hs_ok;
  }
  