text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 2012 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
   * Copyright (C) 2010 - 2011, Hoi-Ho Chan, <hoiho.chan@gmail.com>
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  
  /*
   * Source file for all mbedTLS-specific code for the TLS/SSL layer. No code
   * but vtls.c should ever call or use these functions.
   *
   */
  
  #include "curl_setup.h"
  
  #ifdef USE_MBEDTLS
  
  /* Define this to enable lots of debugging for mbedTLS */
  /* #define MBEDTLS_DEBUG */
  
  #include <mbedtls/version.h>
  #if MBEDTLS_VERSION_NUMBER >= 0x02040000
  #include <mbedtls/net_sockets.h>
  #else
  #include <mbedtls/net.h>
  #endif
  #include <mbedtls/ssl.h>
  #if MBEDTLS_VERSION_NUMBER < 0x03000000
  #include <mbedtls/certs.h>
  #endif
  #include <mbedtls/x509.h>
  
  #include <mbedtls/error.h>
  #include <mbedtls/entropy.h>
  #include <mbedtls/ctr_drbg.h>
  #include <mbedtls/sha256.h>
  
  #if MBEDTLS_VERSION_MAJOR >= 2
  #  ifdef MBEDTLS_DEBUG
  #    include <mbedtls/debug.h>
  #  endif
  #endif
  
  #include "urldata.h"
  #include "sendf.h"
  #include "inet_pton.h"
  #include "mbedtls.h"
  #include "vtls.h"
  #include "parsedate.h"
  #include "connect.h" /* for the connect timeout */
  #include "select.h"
  #include "multiif.h"
  #include "mbedtls_threadlock.h"
  
  /* The last 3 #include files should be in this order */
  #include "curl_printf.h"
  #include "curl_memory.h"
  #include "memdebug.h"
  
  struct ssl_backend_data {
    mbedtls_ctr_drbg_context ctr_drbg;
    mbedtls_entropy_context entropy;
    mbedtls_ssl_context ssl;
    int server_fd;
    mbedtls_x509_crt cacert;
    mbedtls_x509_crt clicert;
    mbedtls_x509_crl crl;
    mbedtls_pk_context pk;
    mbedtls_ssl_config config;
    const char *protocols[3];
  };
  
  /* apply threading? */
  #if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
  #define THREADING_SUPPORT
  #endif
  
  #ifndef MBEDTLS_ERROR_C
  #define mbedtls_strerror(a,b,c) b[0] = 0
  #endif
  
  #if defined(THREADING_SUPPORT)
  static mbedtls_entropy_context ts_entropy;
  
  static int entropy_init_initialized = 0;
  
  /* start of entropy_init_mutex() */
  static void entropy_init_mutex(mbedtls_entropy_context *ctx)
  {
    /* lock 0 = entropy_init_mutex() */
    Curl_mbedtlsthreadlock_lock_function(0);
    if(entropy_init_initialized == 0) {
      mbedtls_entropy_init(ctx);
      entropy_init_initialized = 1;
    }
    Curl_mbedtlsthreadlock_unlock_function(0);
  }
  /* end of entropy_init_mutex() */
  
  /* start of entropy_func_mutex() */
  static int entropy_func_mutex(void *data, unsigned char *output, size_t len)
  {
    int ret;
    /* lock 1 = entropy_func_mutex() */
    Curl_mbedtlsthreadlock_lock_function(1);
    ret = mbedtls_entropy_func(data, output, len);
    Curl_mbedtlsthreadlock_unlock_function(1);
  
    return ret;
  }
  /* end of entropy_func_mutex() */
  
  #endif /* THREADING_SUPPORT */
  
  #ifdef MBEDTLS_DEBUG
  static void mbed_debug(void *context, int level, const char *f_name,
                         int line_nb, const char *line)
  {
    struct Curl_easy *data = NULL;
  
    if(!context)
      return;
  
    data = (struct Curl_easy *)context;
  
    infof(data, "%s", line);
    (void) level;
  }
  #else
  #endif
  
  /* ALPN for http2? */
  #ifdef USE_NGHTTP2
  #  undef HAS_ALPN
  #  ifdef MBEDTLS_SSL_ALPN
  #    define HAS_ALPN
  #  endif
  #endif
  
  
  /*
   *  profile
   */
  static const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_fr =
  {
    /* Hashes from SHA-1 and above */
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_SHA1) |
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_RIPEMD160) |
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_SHA224) |
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_SHA256) |
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_SHA384) |
    MBEDTLS_X509_ID_FLAG(MBEDTLS_MD_SHA512),
    0xFFFFFFF, /* Any PK alg    */
    0xFFFFFFF, /* Any curve     */
    1024,      /* RSA min key len */
  };
  
  /* See https://tls.mbed.org/discussions/generic/
     howto-determine-exact-buffer-len-for-mbedtls_pk_write_pubkey_der
  */
  #define RSA_PUB_DER_MAX_BYTES   (38 + 2 * MBEDTLS_MPI_MAX_SIZE)
  #define ECP_PUB_DER_MAX_BYTES   (30 + 2 * MBEDTLS_ECP_MAX_BYTES)
  
  #define PUB_DER_MAX_BYTES   (RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
                               RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES)
  
  static Curl_recv mbed_recv;
  static Curl_send mbed_send;
  
  static CURLcode mbedtls_version_from_curl(int *mbedver, long version)
  {
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
    switch(version) {
      case CURL_SSLVERSION_TLSv1_0:
      case CURL_SSLVERSION_TLSv1_1:
      case CURL_SSLVERSION_TLSv1_2:
        *mbedver = MBEDTLS_SSL_MINOR_VERSION_3;
        return CURLE_OK;
      case CURL_SSLVERSION_TLSv1_3:
        break;
    }
  #else
    switch(version) {
      case CURL_SSLVERSION_TLSv1_0:
        *mbedver = MBEDTLS_SSL_MINOR_VERSION_1;
        return CURLE_OK;
      case CURL_SSLVERSION_TLSv1_1:
        *mbedver = MBEDTLS_SSL_MINOR_VERSION_2;
        return CURLE_OK;
      case CURL_SSLVERSION_TLSv1_2:
        *mbedver = MBEDTLS_SSL_MINOR_VERSION_3;
        return CURLE_OK;
      case CURL_SSLVERSION_TLSv1_3:
        break;
    }
  #endif
  
    return CURLE_SSL_CONNECT_ERROR;
  }
  
  static CURLcode
  set_ssl_version_min_max(struct Curl_easy *data, struct connectdata *conn,
                          int sockindex)
  {
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
    int mbedtls_ver_min = MBEDTLS_SSL_MINOR_VERSION_3;
    int mbedtls_ver_max = MBEDTLS_SSL_MINOR_VERSION_3;
  #else
    int mbedtls_ver_min = MBEDTLS_SSL_MINOR_VERSION_1;
    int mbedtls_ver_max = MBEDTLS_SSL_MINOR_VERSION_1;
  #endif
    long ssl_version = SSL_CONN_CONFIG(version);
    long ssl_version_max = SSL_CONN_CONFIG(version_max);
    CURLcode result = CURLE_OK;
  
    switch(ssl_version) {
      case CURL_SSLVERSION_DEFAULT:
      case CURL_SSLVERSION_TLSv1:
        ssl_version = CURL_SSLVERSION_TLSv1_0;
        break;
    }
  
    switch(ssl_version_max) {
      case CURL_SSLVERSION_MAX_NONE:
      case CURL_SSLVERSION_MAX_DEFAULT:
        ssl_version_max = CURL_SSLVERSION_MAX_TLSv1_2;
        break;
    }
  
    result = mbedtls_version_from_curl(&mbedtls_ver_min, ssl_version);
    if(result) {
      failf(data, "unsupported min version passed via CURLOPT_SSLVERSION");
      return result;
    }
    result = mbedtls_version_from_curl(&mbedtls_ver_max, ssl_version_max >> 16);
    if(result) {
      failf(data, "unsupported max version passed via CURLOPT_SSLVERSION");
      return result;
    }
  
    mbedtls_ssl_conf_min_version(&backend->config, MBEDTLS_SSL_MAJOR_VERSION_3,
                                 mbedtls_ver_min);
    mbedtls_ssl_conf_max_version(&backend->config, MBEDTLS_SSL_MAJOR_VERSION_3,
                                 mbedtls_ver_max);
  
    return result;
  }
  
  static CURLcode
  mbed_connect_step1(struct Curl_easy *data, struct connectdata *conn,
                     int sockindex)
  {
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
    const char * const ssl_cafile = SSL_CONN_CONFIG(CAfile);
    const bool verifypeer = SSL_CONN_CONFIG(verifypeer);
    const char * const ssl_capath = SSL_CONN_CONFIG(CApath);
    char * const ssl_cert = SSL_SET_OPTION(primary.clientcert);
    const struct curl_blob *ssl_cert_blob = SSL_SET_OPTION(primary.cert_blob);
    const char * const ssl_crlfile = SSL_SET_OPTION(CRLfile);
    const char * const hostname = SSL_HOST_NAME();
  #ifndef CURL_DISABLE_VERBOSE_STRINGS
    const long int port = SSL_HOST_PORT();
  #endif
    int ret = -1;
    char errorbuf[128];
  
    if((SSL_CONN_CONFIG(version) == CURL_SSLVERSION_SSLv2) ||
       (SSL_CONN_CONFIG(version) == CURL_SSLVERSION_SSLv3)) {
      failf(data, "Not supported SSL version");
      return CURLE_NOT_BUILT_IN;
    }
  
  #ifdef THREADING_SUPPORT
    entropy_init_mutex(&ts_entropy);
    mbedtls_ctr_drbg_init(&backend->ctr_drbg);
  
    ret = mbedtls_ctr_drbg_seed(&backend->ctr_drbg, entropy_func_mutex,
                                &ts_entropy, NULL, 0);
    if(ret) {
      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
      failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
            -ret, errorbuf);
    }
  #else
    mbedtls_entropy_init(&backend->entropy);
    mbedtls_ctr_drbg_init(&backend->ctr_drbg);
  
    ret = mbedtls_ctr_drbg_seed(&backend->ctr_drbg, mbedtls_entropy_func,
                                &backend->entropy, NULL, 0);
    if(ret) {
      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
      failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
            -ret, errorbuf);
    }
  #endif /* THREADING_SUPPORT */
  
    /* Load the trusted CA */
    mbedtls_x509_crt_init(&backend->cacert);
  
    if(ssl_cafile) {
      ret = mbedtls_x509_crt_parse_file(&backend->cacert, ssl_cafile);
  
      if(ret<0) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "Error reading ca cert file %s - mbedTLS: (-0x%04X) %s",
              ssl_cafile, -ret, errorbuf);
  
        if(verifypeer)
          return CURLE_SSL_CACERT_BADFILE;
      }
    }
  
    if(ssl_capath) {
      ret = mbedtls_x509_crt_parse_path(&backend->cacert, ssl_capath);
  
      if(ret<0) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "Error reading ca cert path %s - mbedTLS: (-0x%04X) %s",
              ssl_capath, -ret, errorbuf);
  
        if(verifypeer)
          return CURLE_SSL_CACERT_BADFILE;
      }
    }
  
    /* Load the client certificate */
    mbedtls_x509_crt_init(&backend->clicert);
  
    if(ssl_cert) {
      ret = mbedtls_x509_crt_parse_file(&backend->clicert, ssl_cert);
  
      if(ret) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "Error reading client cert file %s - mbedTLS: (-0x%04X) %s",
              ssl_cert, -ret, errorbuf);
  
        return CURLE_SSL_CERTPROBLEM;
      }
    }
  
    if(ssl_cert_blob) {
      const unsigned char *blob_data =
        (const unsigned char *)ssl_cert_blob->data;
      ret = mbedtls_x509_crt_parse(&backend->clicert, blob_data,
                                   ssl_cert_blob->len);
  
      if(ret) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "Error reading private key %s - mbedTLS: (-0x%04X) %s",
              SSL_SET_OPTION(key), -ret, errorbuf);
        return CURLE_SSL_CERTPROBLEM;
      }
    }
  
    /* Load the client private key */
    mbedtls_pk_init(&backend->pk);
  
    if(SSL_SET_OPTION(key) || SSL_SET_OPTION(key_blob)) {
      if(SSL_SET_OPTION(key)) {
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
        ret = mbedtls_pk_parse_keyfile(&backend->pk, SSL_SET_OPTION(key),
                                       SSL_SET_OPTION(key_passwd),
                                       mbedtls_ctr_drbg_random,
                                       &backend->ctr_drbg);
  #else
        ret = mbedtls_pk_parse_keyfile(&backend->pk, SSL_SET_OPTION(key),
                                       SSL_SET_OPTION(key_passwd));
  #endif
  
        if(ret) {
          mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
          failf(data, "Error reading private key %s - mbedTLS: (-0x%04X) %s",
                SSL_SET_OPTION(key), -ret, errorbuf);
          return CURLE_SSL_CERTPROBLEM;
        }
      }
      else {
        const struct curl_blob *ssl_key_blob = SSL_SET_OPTION(key_blob);
        const unsigned char *key_data =
          (const unsigned char *)ssl_key_blob->data;
        const char *passwd = SSL_SET_OPTION(key_passwd);
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
        ret = mbedtls_pk_parse_key(&backend->pk, key_data, ssl_key_blob->len,
                                   (const unsigned char *)passwd,
                                   passwd ? strlen(passwd) : 0,
                                   mbedtls_ctr_drbg_random,
                                   &backend->ctr_drbg);
  #else
        ret = mbedtls_pk_parse_key(&backend->pk, key_data, ssl_key_blob->len,
                                   (const unsigned char *)passwd,
                                   passwd ? strlen(passwd) : 0);
  #endif
  
        if(ret) {
          mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
          failf(data, "Error parsing private key - mbedTLS: (-0x%04X) %s",
                -ret, errorbuf);
          return CURLE_SSL_CERTPROBLEM;
        }
      }
  
      if(ret == 0 && !(mbedtls_pk_can_do(&backend->pk, MBEDTLS_PK_RSA) ||
                       mbedtls_pk_can_do(&backend->pk, MBEDTLS_PK_ECKEY)))
        ret = MBEDTLS_ERR_PK_TYPE_MISMATCH;
    }
  
    /* Load the CRL */
    mbedtls_x509_crl_init(&backend->crl);
  
    if(ssl_crlfile) {
      ret = mbedtls_x509_crl_parse_file(&backend->crl, ssl_crlfile);
  
      if(ret) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "Error reading CRL file %s - mbedTLS: (-0x%04X) %s",
              ssl_crlfile, -ret, errorbuf);
  
        return CURLE_SSL_CRL_BADFILE;
      }
    }
  
    infof(data, "mbedTLS: Connecting to %s:%ld", hostname, port);
  
    mbedtls_ssl_config_init(&backend->config);
  
    mbedtls_ssl_init(&backend->ssl);
    if(mbedtls_ssl_setup(&backend->ssl, &backend->config)) {
      failf(data, "mbedTLS: ssl_init failed");
      return CURLE_SSL_CONNECT_ERROR;
    }
    ret = mbedtls_ssl_config_defaults(&backend->config,
                                      MBEDTLS_SSL_IS_CLIENT,
                                      MBEDTLS_SSL_TRANSPORT_STREAM,
                                      MBEDTLS_SSL_PRESET_DEFAULT);
    if(ret) {
      failf(data, "mbedTLS: ssl_config failed");
      return CURLE_SSL_CONNECT_ERROR;
    }
  
    /* new profile with RSA min key len = 1024 ... */
    mbedtls_ssl_conf_cert_profile(&backend->config,
                                  &mbedtls_x509_crt_profile_fr);
  
    switch(SSL_CONN_CONFIG(version)) {
    case CURL_SSLVERSION_DEFAULT:
    case CURL_SSLVERSION_TLSv1:
  #if MBEDTLS_VERSION_NUMBER < 0x03000000
      mbedtls_ssl_conf_min_version(&backend->config, MBEDTLS_SSL_MAJOR_VERSION_3,
                                   MBEDTLS_SSL_MINOR_VERSION_1);
      infof(data, "mbedTLS: Set min SSL version to TLS 1.0");
      break;
  #endif
    case CURL_SSLVERSION_TLSv1_0:
    case CURL_SSLVERSION_TLSv1_1:
    case CURL_SSLVERSION_TLSv1_2:
    case CURL_SSLVERSION_TLSv1_3:
      {
        CURLcode result = set_ssl_version_min_max(data, conn, sockindex);
        if(result != CURLE_OK)
          return result;
        break;
      }
    default:
      failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
      return CURLE_SSL_CONNECT_ERROR;
    }
  
    mbedtls_ssl_conf_authmode(&backend->config, MBEDTLS_SSL_VERIFY_OPTIONAL);
  
    mbedtls_ssl_conf_rng(&backend->config, mbedtls_ctr_drbg_random,
                         &backend->ctr_drbg);
    mbedtls_ssl_set_bio(&backend->ssl, &conn->sock[sockindex],
                        mbedtls_net_send,
                        mbedtls_net_recv,
                        NULL /*  rev_timeout() */);
  
    mbedtls_ssl_conf_ciphersuites(&backend->config,
                                  mbedtls_ssl_list_ciphersuites());
  
  #if defined(MBEDTLS_SSL_RENEGOTIATION)
    mbedtls_ssl_conf_renegotiation(&backend->config,
                                   MBEDTLS_SSL_RENEGOTIATION_ENABLED);
  #endif
  
  #if defined(MBEDTLS_SSL_SESSION_TICKETS)
    mbedtls_ssl_conf_session_tickets(&backend->config,
                                     MBEDTLS_SSL_SESSION_TICKETS_DISABLED);
  #endif
  
    /* Check if there's a cached ID we can/should use here! */
    if(SSL_SET_OPTION(primary.sessionid)) {
      void *old_session = NULL;
  
      Curl_ssl_sessionid_lock(data);
      if(!Curl_ssl_getsessionid(data, conn,
                                SSL_IS_PROXY() ? TRUE : FALSE,
                                &old_session, NULL, sockindex)) {
        ret = mbedtls_ssl_set_session(&backend->ssl, old_session);
        if(ret) {
          Curl_ssl_sessionid_unlock(data);
          failf(data, "mbedtls_ssl_set_session returned -0x%x", -ret);
          return CURLE_SSL_CONNECT_ERROR;
        }
        infof(data, "mbedTLS re-using session");
      }
      Curl_ssl_sessionid_unlock(data);
    }
  
    mbedtls_ssl_conf_ca_chain(&backend->config,
                              &backend->cacert,
                              &backend->crl);
  
    if(SSL_SET_OPTION(key) || SSL_SET_OPTION(key_blob)) {
      mbedtls_ssl_conf_own_cert(&backend->config,
                                &backend->clicert, &backend->pk);
    }
    if(mbedtls_ssl_set_hostname(&backend->ssl, hostname)) {
      /* mbedtls_ssl_set_hostname() sets the name to use in CN/SAN checks *and*
         the name to set in the SNI extension. So even if curl connects to a
         host specified as an IP address, this function must be used. */
      failf(data, "couldn't set hostname in mbedTLS");
      return CURLE_SSL_CONNECT_ERROR;
    }
  
  #ifdef HAS_ALPN
    if(conn->bits.tls_enable_alpn) {
      const char **p = &backend->protocols[0];
  #ifdef USE_NGHTTP2
      if(data->state.httpwant >= CURL_HTTP_VERSION_2)
        *p++ = NGHTTP2_PROTO_VERSION_ID;
  #endif
      *p++ = ALPN_HTTP_1_1;
      *p = NULL;
      /* this function doesn't clone the protocols array, which is why we need
         to keep it around */
      if(mbedtls_ssl_conf_alpn_protocols(&backend->config,
                                         &backend->protocols[0])) {
        failf(data, "Failed setting ALPN protocols");
        return CURLE_SSL_CONNECT_ERROR;
      }
      for(p = &backend->protocols[0]; *p; ++p)
        infof(data, "ALPN, offering %s", *p);
    }
  #endif
  
  #ifdef MBEDTLS_DEBUG
    /* In order to make that work in mbedtls MBEDTLS_DEBUG_C must be defined. */
    mbedtls_ssl_conf_dbg(&backend->config, mbed_debug, data);
    /* - 0 No debug
     * - 1 Error
     * - 2 State change
     * - 3 Informational
     * - 4 Verbose
     */
    mbedtls_debug_set_threshold(4);
  #endif
  
    /* give application a chance to interfere with mbedTLS set up. */
    if(data->set.ssl.fsslctx) {
      ret = (*data->set.ssl.fsslctx)(data, &backend->config,
                                     data->set.ssl.fsslctxp);
      if(ret) {
        failf(data, "error signaled by ssl ctx callback");
        return ret;
      }
    }
  
    connssl->connecting_state = ssl_connect_2;
  
    return CURLE_OK;
  }
  
  static CURLcode
  mbed_connect_step2(struct Curl_easy *data, struct connectdata *conn,
                     int sockindex)
  {
    int ret;
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
    const mbedtls_x509_crt *peercert;
    const char * const pinnedpubkey = SSL_PINNED_PUB_KEY();
  
    conn->recv[sockindex] = mbed_recv;
    conn->send[sockindex] = mbed_send;
  
    ret = mbedtls_ssl_handshake(&backend->ssl);
  
    if(ret == MBEDTLS_ERR_SSL_WANT_READ) {
      connssl->connecting_state = ssl_connect_2_reading;
      return CURLE_OK;
    }
    else if(ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
      connssl->connecting_state = ssl_connect_2_writing;
      return CURLE_OK;
    }
    else if(ret) {
      char errorbuf[128];
      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
      failf(data, "ssl_handshake returned - mbedTLS: (-0x%04X) %s",
            -ret, errorbuf);
      return CURLE_SSL_CONNECT_ERROR;
    }
  
    infof(data, "mbedTLS: Handshake complete, cipher is %s",
          mbedtls_ssl_get_ciphersuite(&backend->ssl));
  
    ret = mbedtls_ssl_get_verify_result(&backend->ssl);
  
    if(!SSL_CONN_CONFIG(verifyhost))
      /* Ignore hostname errors if verifyhost is disabled */
      ret &= ~MBEDTLS_X509_BADCERT_CN_MISMATCH;
  
    if(ret && SSL_CONN_CONFIG(verifypeer)) {
      if(ret & MBEDTLS_X509_BADCERT_EXPIRED)
        failf(data, "Cert verify failed: BADCERT_EXPIRED");
  
      else if(ret & MBEDTLS_X509_BADCERT_REVOKED)
        failf(data, "Cert verify failed: BADCERT_REVOKED");
  
      else if(ret & MBEDTLS_X509_BADCERT_CN_MISMATCH)
        failf(data, "Cert verify failed: BADCERT_CN_MISMATCH");
  
      else if(ret & MBEDTLS_X509_BADCERT_NOT_TRUSTED)
        failf(data, "Cert verify failed: BADCERT_NOT_TRUSTED");
  
      else if(ret & MBEDTLS_X509_BADCERT_FUTURE)
        failf(data, "Cert verify failed: BADCERT_FUTURE");
  
      return CURLE_PEER_FAILED_VERIFICATION;
    }
  
    peercert = mbedtls_ssl_get_peer_cert(&backend->ssl);
  
    if(peercert && data->set.verbose) {
      const size_t bufsize = 16384;
      char *buffer = malloc(bufsize);
  
      if(!buffer)
        return CURLE_OUT_OF_MEMORY;
  
      if(mbedtls_x509_crt_info(buffer, bufsize, "* ", peercert) > 0)
        infof(data, "Dumping cert info: %s", buffer);
      else
        infof(data, "Unable to dump certificate information");
  
      free(buffer);
    }
  
    if(pinnedpubkey) {
      int size;
      CURLcode result;
      mbedtls_x509_crt *p = NULL;
      unsigned char *pubkey = NULL;
  
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
      if(!peercert || !peercert->MBEDTLS_PRIVATE(raw).MBEDTLS_PRIVATE(p) ||
         !peercert->MBEDTLS_PRIVATE(raw).MBEDTLS_PRIVATE(len)) {
  #else
      if(!peercert || !peercert->raw.p || !peercert->raw.len) {
  #endif
        failf(data, "Failed due to missing peer certificate");
        return CURLE_SSL_PINNEDPUBKEYNOTMATCH;
      }
  
      p = calloc(1, sizeof(*p));
  
      if(!p)
        return CURLE_OUT_OF_MEMORY;
  
      pubkey = malloc(PUB_DER_MAX_BYTES);
  
      if(!pubkey) {
        result = CURLE_OUT_OF_MEMORY;
        goto pinnedpubkey_error;
      }
  
      mbedtls_x509_crt_init(p);
  
      /* Make a copy of our const peercert because mbedtls_pk_write_pubkey_der
         needs a non-const key, for now.
         https://github.com/ARMmbed/mbedtls/issues/396 */
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
      if(mbedtls_x509_crt_parse_der(p,
                          peercert->MBEDTLS_PRIVATE(raw).MBEDTLS_PRIVATE(p),
                          peercert->MBEDTLS_PRIVATE(raw).MBEDTLS_PRIVATE(len))) {
  #else
      if(mbedtls_x509_crt_parse_der(p, peercert->raw.p, peercert->raw.len)) {
  #endif
        failf(data, "Failed copying peer certificate");
        result = CURLE_SSL_PINNEDPUBKEYNOTMATCH;
        goto pinnedpubkey_error;
      }
  
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
      size = mbedtls_pk_write_pubkey_der(&p->MBEDTLS_PRIVATE(pk), pubkey,
                                         PUB_DER_MAX_BYTES);
  #else
      size = mbedtls_pk_write_pubkey_der(&p->pk, pubkey, PUB_DER_MAX_BYTES);
  #endif
  
      if(size <= 0) {
        failf(data, "Failed copying public key from peer certificate");
        result = CURLE_SSL_PINNEDPUBKEYNOTMATCH;
        goto pinnedpubkey_error;
      }
  
      /* mbedtls_pk_write_pubkey_der writes data at the end of the buffer. */
      result = Curl_pin_peer_pubkey(data,
                                    pinnedpubkey,
                                    &pubkey[PUB_DER_MAX_BYTES - size], size);
      pinnedpubkey_error:
      mbedtls_x509_crt_free(p);
      free(p);
      free(pubkey);
      if(result) {
        return result;
      }
    }
  
  #ifdef HAS_ALPN
    if(conn->bits.tls_enable_alpn) {
      const char *next_protocol = mbedtls_ssl_get_alpn_protocol(&backend->ssl);
  
      if(next_protocol) {
        infof(data, "ALPN, server accepted to use %s", next_protocol);
  #ifdef USE_NGHTTP2
        if(!strncmp(next_protocol, NGHTTP2_PROTO_VERSION_ID,
                    NGHTTP2_PROTO_VERSION_ID_LEN) &&
           !next_protocol[NGHTTP2_PROTO_VERSION_ID_LEN]) {
          conn->negnpn = CURL_HTTP_VERSION_2;
        }
        else
  #endif
          if(!strncmp(next_protocol, ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH) &&
             !next_protocol[ALPN_HTTP_1_1_LENGTH]) {
            conn->negnpn = CURL_HTTP_VERSION_1_1;
          }
      }
      else {
        infof(data, "ALPN, server did not agree to a protocol");
      }
      Curl_multiuse_state(data, conn->negnpn == CURL_HTTP_VERSION_2 ?
                          BUNDLE_MULTIPLEX : BUNDLE_NO_MULTIUSE);
    }
  #endif
  
    connssl->connecting_state = ssl_connect_3;
    infof(data, "SSL connected");
  
    return CURLE_OK;
  }
  
  static CURLcode
  mbed_connect_step3(struct Curl_easy *data, struct connectdata *conn,
                     int sockindex)
  {
    CURLcode retcode = CURLE_OK;
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
  
    DEBUGASSERT(ssl_connect_3 == connssl->connecting_state);
  
    if(SSL_SET_OPTION(primary.sessionid)) {
      int ret;
      mbedtls_ssl_session *our_ssl_sessionid;
      void *old_ssl_sessionid = NULL;
      bool isproxy = SSL_IS_PROXY() ? TRUE : FALSE;
  
      our_ssl_sessionid = malloc(sizeof(mbedtls_ssl_session));
      if(!our_ssl_sessionid)
        return CURLE_OUT_OF_MEMORY;
  
      mbedtls_ssl_session_init(our_ssl_sessionid);
  
      ret = mbedtls_ssl_get_session(&backend->ssl, our_ssl_sessionid);
      if(ret) {
        if(ret != MBEDTLS_ERR_SSL_ALLOC_FAILED)
          mbedtls_ssl_session_free(our_ssl_sessionid);
        free(our_ssl_sessionid);
        failf(data, "mbedtls_ssl_get_session returned -0x%x", -ret);
        return CURLE_SSL_CONNECT_ERROR;
      }
  
      /* If there's already a matching session in the cache, delete it */
      Curl_ssl_sessionid_lock(data);
      if(!Curl_ssl_getsessionid(data, conn, isproxy, &old_ssl_sessionid, NULL,
                                sockindex))
        Curl_ssl_delsessionid(data, old_ssl_sessionid);
  
      retcode = Curl_ssl_addsessionid(data, conn, isproxy, our_ssl_sessionid,
                                      0, sockindex);
      Curl_ssl_sessionid_unlock(data);
      if(retcode) {
        mbedtls_ssl_session_free(our_ssl_sessionid);
        free(our_ssl_sessionid);
        failf(data, "failed to store ssl session");
        return retcode;
      }
    }
  
    connssl->connecting_state = ssl_connect_done;
  
    return CURLE_OK;
  }
  
  static ssize_t mbed_send(struct Curl_easy *data, int sockindex,
                           const void *mem, size_t len,
                           CURLcode *curlcode)
  {
    struct connectdata *conn = data->conn;
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
    int ret = -1;
  
    ret = mbedtls_ssl_write(&backend->ssl, (unsigned char *)mem, len);
  
    if(ret < 0) {
      *curlcode = (ret == MBEDTLS_ERR_SSL_WANT_WRITE) ?
        CURLE_AGAIN : CURLE_SEND_ERROR;
      ret = -1;
    }
  
    return ret;
  }
  
  static void mbedtls_close_all(struct Curl_easy *data)
  {
    (void)data;
  }
  
  static void mbedtls_close(struct Curl_easy *data,
                            struct connectdata *conn, int sockindex)
  {
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
    char buf[32];
    (void) data;
  
    /* Maybe the server has already sent a close notify alert.
       Read it to avoid an RST on the TCP connection. */
    (void)mbedtls_ssl_read(&backend->ssl, (unsigned char *)buf, sizeof(buf));
  
    mbedtls_pk_free(&backend->pk);
    mbedtls_x509_crt_free(&backend->clicert);
    mbedtls_x509_crt_free(&backend->cacert);
    mbedtls_x509_crl_free(&backend->crl);
    mbedtls_ssl_config_free(&backend->config);
    mbedtls_ssl_free(&backend->ssl);
    mbedtls_ctr_drbg_free(&backend->ctr_drbg);
  #ifndef THREADING_SUPPORT
    mbedtls_entropy_free(&backend->entropy);
  #endif /* THREADING_SUPPORT */
  }
  
  static ssize_t mbed_recv(struct Curl_easy *data, int num,
                           char *buf, size_t buffersize,
                           CURLcode *curlcode)
  {
    struct connectdata *conn = data->conn;
    struct ssl_connect_data *connssl = &conn->ssl[num];
    struct ssl_backend_data *backend = connssl->backend;
    int ret = -1;
    ssize_t len = -1;
  
    ret = mbedtls_ssl_read(&backend->ssl, (unsigned char *)buf,
                           buffersize);
  
    if(ret <= 0) {
      if(ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY)
        return 0;
  
      *curlcode = (ret == MBEDTLS_ERR_SSL_WANT_READ) ?
        CURLE_AGAIN : CURLE_RECV_ERROR;
      return -1;
    }
  
    len = ret;
  
    return len;
  }
  
  static void mbedtls_session_free(void *ptr)
  {
    mbedtls_ssl_session_free(ptr);
    free(ptr);
  }
  
  static size_t mbedtls_version(char *buffer, size_t size)
  {
  #ifdef MBEDTLS_VERSION_C
    /* if mbedtls_version_get_number() is available it is better */
    unsigned int version = mbedtls_version_get_number();
    return msnprintf(buffer, size, "mbedTLS/%u.%u.%u", version>>24,
                     (version>>16)&0xff, (version>>8)&0xff);
  #else
    return msnprintf(buffer, size, "mbedTLS/%s", MBEDTLS_VERSION_STRING);
  #endif
  }
  
  static CURLcode mbedtls_random(struct Curl_easy *data,
                                 unsigned char *entropy, size_t length)
  {
  #if defined(MBEDTLS_CTR_DRBG_C)
    int ret = -1;
    char errorbuf[128];
    mbedtls_entropy_context ctr_entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    mbedtls_entropy_init(&ctr_entropy);
    mbedtls_ctr_drbg_init(&ctr_drbg);
  
    ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func,
                                &ctr_entropy, NULL, 0);
  
    if(ret) {
      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
      failf(data, "Failed - mbedTLS: ctr_drbg_seed returned (-0x%04X) %s",
            -ret, errorbuf);
    }
    else {
      ret = mbedtls_ctr_drbg_random(&ctr_drbg, entropy, length);
  
      if(ret) {
        mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
        failf(data, "mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
              -ret, errorbuf);
      }
    }
  
    mbedtls_ctr_drbg_free(&ctr_drbg);
    mbedtls_entropy_free(&ctr_entropy);
  
    return ret == 0 ? CURLE_OK : CURLE_FAILED_INIT;
  #elif defined(MBEDTLS_HAVEGE_C)
    mbedtls_havege_state hs;
    mbedtls_havege_init(&hs);
    mbedtls_havege_random(&hs, entropy, length);
    mbedtls_havege_free(&hs);
    return CURLE_OK;
  #else
    return CURLE_NOT_BUILT_IN;
  #endif
  }
  
  static CURLcode
  mbed_connect_common(struct Curl_easy *data,
                      struct connectdata *conn,
                      int sockindex,
                      bool nonblocking,
                      bool *done)
  {
    CURLcode retcode;
    struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    curl_socket_t sockfd = conn->sock[sockindex];
    timediff_t timeout_ms;
    int what;
  
    /* check if the connection has already been established */
    if(ssl_connection_complete == connssl->state) {
      *done = TRUE;
      return CURLE_OK;
    }
  
    if(ssl_connect_1 == connssl->connecting_state) {
      /* Find out how much more time we're allowed */
      timeout_ms = Curl_timeleft(data, NULL, TRUE);
  
      if(timeout_ms < 0) {
        /* no need to continue if time already is up */
        failf(data, "SSL connection timeout");
        return CURLE_OPERATION_TIMEDOUT;
      }
      retcode = mbed_connect_step1(data, conn, sockindex);
      if(retcode)
        return retcode;
    }
  
    while(ssl_connect_2 == connssl->connecting_state ||
          ssl_connect_2_reading == connssl->connecting_state ||
          ssl_connect_2_writing == connssl->connecting_state) {
  
      /* check allowed time left */
      timeout_ms = Curl_timeleft(data, NULL, TRUE);
  
      if(timeout_ms < 0) {
        /* no need to continue if time already is up */
        failf(data, "SSL connection timeout");
        return CURLE_OPERATION_TIMEDOUT;
      }
  
      /* if ssl is expecting something, check if it's available. */
      if(connssl->connecting_state == ssl_connect_2_reading
         || connssl->connecting_state == ssl_connect_2_writing) {
  
        curl_socket_t writefd = ssl_connect_2_writing ==
          connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
        curl_socket_t readfd = ssl_connect_2_reading ==
          connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
  
        what = Curl_socket_check(readfd, CURL_SOCKET_BAD, writefd,
                                 nonblocking ? 0 : timeout_ms);
        if(what < 0) {
          /* fatal error */
          failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
          return CURLE_SSL_CONNECT_ERROR;
        }
        else if(0 == what) {
          if(nonblocking) {
            *done = FALSE;
            return CURLE_OK;
          }
          else {
            /* timeout */
            failf(data, "SSL connection timeout");
            return CURLE_OPERATION_TIMEDOUT;
          }
        }
        /* socket is readable or writable */
      }
  
      /* Run transaction, and return to the caller if it failed or if
       * this connection is part of a multi handle and this loop would
       * execute again. This permits the owner of a multi handle to
       * abort a connection attempt before step2 has completed while
       * ensuring that a client using select() or epoll() will always
       * have a valid fdset to wait on.
       */
      retcode = mbed_connect_step2(data, conn, sockindex);
      if(retcode || (nonblocking &&
                     (ssl_connect_2 == connssl->connecting_state ||
                      ssl_connect_2_reading == connssl->connecting_state ||
                      ssl_connect_2_writing == connssl->connecting_state)))
        return retcode;
  
    } /* repeat step2 until all transactions are done. */
  
    if(ssl_connect_3 == connssl->connecting_state) {
      retcode = mbed_connect_step3(data, conn, sockindex);
      if(retcode)
        return retcode;
    }
  
    if(ssl_connect_done == connssl->connecting_state) {
      connssl->state = ssl_connection_complete;
      conn->recv[sockindex] = mbed_recv;
      conn->send[sockindex] = mbed_send;
      *done = TRUE;
    }
    else
      *done = FALSE;
  
    /* Reset our connect state machine */
    connssl->connecting_state = ssl_connect_1;
  
    return CURLE_OK;
  }
  
  static CURLcode mbedtls_connect_nonblocking(struct Curl_easy *data,
                                              struct connectdata *conn,
                                              int sockindex, bool *done)
  {
    return mbed_connect_common(data, conn, sockindex, TRUE, done);
  }
  
  
  static CURLcode mbedtls_connect(struct Curl_easy *data,
                                  struct connectdata *conn, int sockindex)
  {
    CURLcode retcode;
    bool done = FALSE;
  
    retcode = mbed_connect_common(data, conn, sockindex, FALSE, &done);
    if(retcode)
      return retcode;
  
    DEBUGASSERT(done);
  
    return CURLE_OK;
  }
  
  /*
   * return 0 error initializing SSL
   * return 1 SSL initialized successfully
   */
  static int mbedtls_init(void)
  {
    return Curl_mbedtlsthreadlock_thread_setup();
  }
  
  static void mbedtls_cleanup(void)
  {
    (void)Curl_mbedtlsthreadlock_thread_cleanup();
  }
  
  static bool mbedtls_data_pending(const struct connectdata *conn,
                                   int sockindex)
  {
    const struct ssl_connect_data *connssl = &conn->ssl[sockindex];
    struct ssl_backend_data *backend = connssl->backend;
    return mbedtls_ssl_get_bytes_avail(&backend->ssl) != 0;
  }
  
  static CURLcode mbedtls_sha256sum(const unsigned char *input,
                                    size_t inputlen,
                                    unsigned char *sha256sum,
                                    size_t sha256len UNUSED_PARAM)
  {
    /* TODO: explain this for different mbedtls 2.x vs 3 version */
    (void)sha256len;
  #if MBEDTLS_VERSION_NUMBER < 0x02070000
    mbedtls_sha256(input, inputlen, sha256sum, 0);
  #else
    /* returns 0 on success, otherwise failure */
  #if MBEDTLS_VERSION_NUMBER >= 0x03000000
    if(mbedtls_sha256(input, inputlen, sha256sum, 0) != 0)
  #else
    if(mbedtls_sha256_ret(input, inputlen, sha256sum, 0) != 0)
  #endif
      return CURLE_BAD_FUNCTION_ARGUMENT;
  #endif
    return CURLE_OK;
  }
  
  static void *mbedtls_get_internals(struct ssl_connect_data *connssl,
                                     CURLINFO info UNUSED_PARAM)
  {
    struct ssl_backend_data *backend = connssl->backend;
    (void)info;
    return &backend->ssl;
  }
  
  const struct Curl_ssl Curl_ssl_mbedtls = {
    { CURLSSLBACKEND_MBEDTLS, "mbedtls" }, /* info */
  
    SSLSUPP_CA_PATH |
    SSLSUPP_PINNEDPUBKEY |
    SSLSUPP_SSL_CTX,
  
    sizeof(struct ssl_backend_data),
  
    mbedtls_init,                     /* init */
    mbedtls_cleanup,                  /* cleanup */
    mbedtls_version,                  /* version */
    Curl_none_check_cxn,              /* check_cxn */
    Curl_none_shutdown,               /* shutdown */
    mbedtls_data_pending,             /* data_pending */
    mbedtls_random,                   /* random */
    Curl_none_cert_status_request,    /* cert_status_request */
    mbedtls_connect,                  /* connect */
    mbedtls_connect_nonblocking,      /* connect_nonblocking */
    Curl_ssl_getsock,                 /* getsock */
    mbedtls_get_internals,            /* get_internals */
    mbedtls_close,                    /* close_one */
    mbedtls_close_all,                /* close_all */
    mbedtls_session_free,             /* session_free */
    Curl_none_set_engine,             /* set_engine */
    Curl_none_set_engine_default,     /* set_engine_default */
    Curl_none_engines_list,           /* engines_list */
    Curl_none_false_start,            /* false_start */
    mbedtls_sha256sum,                /* sha256sum */
    NULL,                             /* associate_connection */
    NULL                              /* disassociate_connection */
  };
  
  #endif /* USE_MBEDTLS */
  