openssl.c

    if(data->set.verbose) {
#ifdef HAVE_SSL_GET_SHUTDOWN
      switch(SSL_get_shutdown(connssl->handle)) {
      case SSL_SENT_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_SENT_SHUTDOWN\n");
        break;
      case SSL_RECEIVED_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_RECEIVED_SHUTDOWN\n");
        break;
      case SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_SENT_SHUTDOWN|"
              "SSL_RECEIVED__SHUTDOWN\n");
        break;
      }
#endif
    }

    SSL_free (connssl->handle);
    connssl->handle = NULL;
  }
  return retval;
}

void Curl_ossl_session_free(void *ptr)
{
  /* free the ID */
  SSL_SESSION_free(ptr);
}

/*
 * This function is called when the 'data' struct is going away. Close
 * down everything and free all resources!
 */
void Curl_ossl_close_all(struct SessionHandle *data)
{
#ifdef HAVE_OPENSSL_ENGINE_H
  if(data->state.engine) {
    ENGINE_finish(data->state.engine);
    ENGINE_free(data->state.engine);
    data->state.engine = NULL;
  }
#else
  (void)data;
#endif
}

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


/* Quote from RFC2818 section 3.1 "Server Identity"

   If a subjectAltName extension of type dNSName is present, that MUST
   be used as the identity. Otherwise, the (most specific) Common Name
   field in the Subject field of the certificate MUST be used. Although
   the use of the Common Name is existing practice, it is deprecated and
   Certification Authorities are encouraged to use the dNSName instead.

   Matching is performed using the matching rules specified by
   [RFC2459].  If more than one identity of a given type is present in
   the certificate (e.g., more than one dNSName name, a match in any one
   of the set is considered acceptable.) Names may contain the wildcard
   character * which is considered to match any single domain name
   component or component fragment. E.g., *.a.com matches foo.a.com but
   not bar.foo.a.com. f*.com matches foo.com but not bar.com.

   In some cases, the URI is specified as an IP address rather than a
   hostname. In this case, the iPAddress subjectAltName must be present
   in the certificate and must exactly match the IP in the URI.

*/
static CURLcode verifyhost(struct connectdata *conn, X509 *server_cert)
{
  bool matched = FALSE;
  int target = GEN_DNS; /* target type, GEN_DNS or GEN_IPADD */
  size_t addrlen = 0;
  struct SessionHandle *data = conn->data;
  STACK_OF(GENERAL_NAME) *altnames;
#ifdef ENABLE_IPV6
  struct in6_addr addr;
#else
  struct in_addr addr;
#endif
  CURLcode result = CURLE_OK;
  bool dNSName = FALSE; /* if a dNSName field exists in the cert */

#ifdef ENABLE_IPV6
  if(conn->bits.ipv6_ip &&
     Curl_inet_pton(AF_INET6, conn->host.name, &addr)) {
    target = GEN_IPADD;
    addrlen = sizeof(struct in6_addr);
  }
  else
#endif
    if(Curl_inet_pton(AF_INET, conn->host.name, &addr)) {
      target = GEN_IPADD;
      addrlen = sizeof(struct in_addr);
    }

  /* get a "list" of alternative names */
  altnames = X509_get_ext_d2i(server_cert, NID_subject_alt_name, NULL, NULL);

  if(altnames) {
    int numalts;
    int i;
    bool dnsmatched = FALSE;
    bool ipmatched = FALSE;

    /* get amount of alternatives, RFC2459 claims there MUST be at least
       one, but we don't depend on it... */
    numalts = sk_GENERAL_NAME_num(altnames);

    /* loop through all alternatives - until a dnsmatch */
    for(i=0; (i < numalts) && !dnsmatched; i++) {
      /* get a handle to alternative name number i */
      const GENERAL_NAME *check = sk_GENERAL_NAME_value(altnames, i);

      /* If a subjectAltName extension of type dNSName is present, that MUST
         be used as the identity. / RFC2818 section 3.1 */
      if(check->type == GEN_DNS)
        dNSName = TRUE;

      /* only check alternatives of the same type the target is */
      if(check->type == target) {
        /* get data and length */
        const char *altptr = (char *)ASN1_STRING_data(check->d.ia5);
        size_t altlen = (size_t) ASN1_STRING_length(check->d.ia5);

        switch(target) {
        case GEN_DNS: /* name/pattern comparison */
          /* The OpenSSL man page explicitly says: "In general it cannot be
             assumed that the data returned by ASN1_STRING_data() is null
             terminated or does not contain embedded nulls." But also that
             "The actual format of the data will depend on the actual string
             type itself: for example for and IA5String the data will be ASCII"

             Gisle researched the OpenSSL sources:
             "I checked the 0.9.6 and 0.9.8 sources before my patch and
             it always 0-terminates an IA5String."
          */
          if((altlen == strlen(altptr)) &&
             /* if this isn't true, there was an embedded zero in the name
                string and we cannot match it. */
             Curl_cert_hostcheck(altptr, conn->host.name)) {
            dnsmatched = TRUE;
            infof(data,
                  " subjectAltName: host \"%s\" matched cert's \"%s\"\n",
                  conn->host.dispname, altptr);
          }
          break;

        case GEN_IPADD: /* IP address comparison */
          /* compare alternative IP address if the data chunk is the same size
             our server IP address is */
          if((altlen == addrlen) && !memcmp(altptr, &addr, altlen)) {
            ipmatched = TRUE;
            infof(data,
                  " subjectAltName: host \"%s\" matched cert's IP address!\n",
                  conn->host.dispname);
          }
          break;
        }
      }
    }
    GENERAL_NAMES_free(altnames);

    if(dnsmatched || (!dNSName && ipmatched)) {
      /* count as a match if the dnsname matched or if there was no dnsname
         fields at all AND there was an IP field match */
      matched = TRUE;
    }
  }

  if(matched)
    /* an alternative name matched */
    ;
  else if(dNSName) {
    /* an dNSName field existed, but didn't match and then we MUST fail */
    infof(data, " subjectAltName does not match %s\n", conn->host.dispname);
    failf(data, "SSL: no alternative certificate subject name matches "
          "target host name '%s'", conn->host.dispname);
    result = CURLE_PEER_FAILED_VERIFICATION;
  }
  else {
    /* we have to look to the last occurrence of a commonName in the
       distinguished one to get the most significant one. */
    int j, i=-1;

    /* The following is done because of a bug in 0.9.6b */

    unsigned char *nulstr = (unsigned char *)"";
    unsigned char *peer_CN = nulstr;

    X509_NAME *name = X509_get_subject_name(server_cert);
    if(name)
      while((j = X509_NAME_get_index_by_NID(name, NID_commonName, i))>=0)
        i=j;

    /* we have the name entry and we will now convert this to a string
       that we can use for comparison. Doing this we support BMPstring,
       UTF8 etc. */

    if(i>=0) {
      ASN1_STRING *tmp =
        X509_NAME_ENTRY_get_data(X509_NAME_get_entry(name, i));

      /* In OpenSSL 0.9.7d and earlier, ASN1_STRING_to_UTF8 fails if the input
         is already UTF-8 encoded. We check for this case and copy the raw
         string manually to avoid the problem. This code can be made
         conditional in the future when OpenSSL has been fixed. Work-around
         brought by Alexis S. L. Carvalho. */
      if(tmp) {
        if(ASN1_STRING_type(tmp) == V_ASN1_UTF8STRING) {
          j = ASN1_STRING_length(tmp);
          if(j >= 0) {
            peer_CN = OPENSSL_malloc(j+1);
            if(peer_CN) {
              memcpy(peer_CN, ASN1_STRING_data(tmp), j);
              peer_CN[j] = '\0';
            }
          }
        }
        else /* not a UTF8 name */
          j = ASN1_STRING_to_UTF8(&peer_CN, tmp);

        if(peer_CN && (curlx_uztosi(strlen((char *)peer_CN)) != j)) {
          /* there was a terminating zero before the end of string, this
             cannot match and we return failure! */
          failf(data, "SSL: illegal cert name field");
          result = CURLE_PEER_FAILED_VERIFICATION;
        }
      }
    }

    if(peer_CN == nulstr)
       peer_CN = NULL;
    else {
      /* convert peer_CN from UTF8 */
      CURLcode rc = Curl_convert_from_utf8(data, peer_CN, strlen(peer_CN));
      /* Curl_convert_from_utf8 calls failf if unsuccessful */
      if(rc) {
        OPENSSL_free(peer_CN);
        return rc;
      }
    }

    if(result)
      /* error already detected, pass through */
      ;
    else if(!peer_CN) {
      failf(data,
            "SSL: unable to obtain common name from peer certificate");
      result = CURLE_PEER_FAILED_VERIFICATION;
    }
    else if(!Curl_cert_hostcheck((const char *)peer_CN, conn->host.name)) {
      failf(data, "SSL: certificate subject name '%s' does not match "
            "target host name '%s'", peer_CN, conn->host.dispname);
      result = CURLE_PEER_FAILED_VERIFICATION;
    }
    else {
      infof(data, " common name: %s (matched)\n", peer_CN);
    }
    if(peer_CN)
      OPENSSL_free(peer_CN);
  }

  return result;
}

#if (OPENSSL_VERSION_NUMBER >= 0x0090808fL) && !defined(OPENSSL_NO_TLSEXT) && \
    !defined(OPENSSL_NO_OCSP)
static CURLcode verifystatus(struct connectdata *conn,
                             struct ssl_connect_data *connssl)
{
  int i, ocsp_status;
  const unsigned char *p;
  CURLcode result = CURLE_OK;
  struct SessionHandle *data = conn->data;

  OCSP_RESPONSE *rsp = NULL;
  OCSP_BASICRESP *br = NULL;
  X509_STORE     *st = NULL;
  STACK_OF(X509) *ch = NULL;

  long len = SSL_get_tlsext_status_ocsp_resp(connssl->handle, &p);

  if(!p) {
    failf(data, "No OCSP response received");
    result = CURLE_SSL_INVALIDCERTSTATUS;
    goto end;
  }

  rsp = d2i_OCSP_RESPONSE(NULL, &p, len);
  if(!rsp) {
    failf(data, "Invalid OCSP response");
    result = CURLE_SSL_INVALIDCERTSTATUS;
    goto end;
  }

  ocsp_status = OCSP_response_status(rsp);
  if(ocsp_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
    failf(data, "Invalid OCSP response status: %s (%d)",
          OCSP_response_status_str(ocsp_status), ocsp_status);
    result = CURLE_SSL_INVALIDCERTSTATUS;
    goto end;
  }

  br = OCSP_response_get1_basic(rsp);
  if(!br) {
    failf(data, "Invalid OCSP response");
    result = CURLE_SSL_INVALIDCERTSTATUS;
    goto end;
  }

  ch = SSL_get_peer_cert_chain(connssl->handle);
  st = SSL_CTX_get_cert_store(connssl->ctx);

#if ((OPENSSL_VERSION_NUMBER <= 0x1000201fL) /* Fixed after 1.0.2a */ || \
     defined(LIBRESSL_VERSION_NUMBER))
  /* The authorized responder cert in the OCSP response MUST be signed by the
     peer cert's issuer (see RFC6960 section 4.2.2.2). If that's a root cert,
     no problem, but if it's an intermediate cert OpenSSL has a bug where it
     expects this issuer to be present in the chain embedded in the OCSP
     response. So we add it if necessary. */

  /* First make sure the peer cert chain includes both a peer and an issuer,
     and the OCSP response contains a responder cert. */
  if(sk_X509_num(ch) >= 2 && sk_X509_num(br->certs) >= 1) {
    X509 *responder = sk_X509_value(br->certs, sk_X509_num(br->certs) - 1);

    /* Find issuer of responder cert and add it to the OCSP response chain */
    for(i = 0; i < sk_X509_num(ch); i++) {
      X509 *issuer = sk_X509_value(ch, i);
      if(X509_check_issued(issuer, responder) == X509_V_OK) {
        if(!OCSP_basic_add1_cert(br, issuer)) {
          failf(data, "Could not add issuer cert to OCSP response");
          result = CURLE_SSL_INVALIDCERTSTATUS;
          goto end;
        }
      }
    }
  }
#endif

  if(OCSP_basic_verify(br, ch, st, 0) <= 0) {
    failf(data, "OCSP response verification failed");
    result = CURLE_SSL_INVALIDCERTSTATUS;
    goto end;
  }

  for(i = 0; i < OCSP_resp_count(br); i++) {
    int cert_status, crl_reason;
    OCSP_SINGLERESP *single = NULL;

    ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd;

    single = OCSP_resp_get0(br, i);
    if(!single)
      continue;

    cert_status = OCSP_single_get0_status(single, &crl_reason, &rev,
                                          &thisupd, &nextupd);

    if(!OCSP_check_validity(thisupd, nextupd, 300L, -1L)) {
      failf(data, "OCSP response has expired");
      result = CURLE_SSL_INVALIDCERTSTATUS;
      goto end;
    }

    infof(data, "SSL certificate status: %s (%d)\n",
          OCSP_cert_status_str(cert_status), cert_status);

    switch(cert_status) {
      case V_OCSP_CERTSTATUS_GOOD:
        break;

      case V_OCSP_CERTSTATUS_REVOKED:
        result = CURLE_SSL_INVALIDCERTSTATUS;

        failf(data, "SSL certificate revocation reason: %s (%d)",
              OCSP_crl_reason_str(crl_reason), crl_reason);
        goto end;

      case V_OCSP_CERTSTATUS_UNKNOWN:
        result = CURLE_SSL_INVALIDCERTSTATUS;
        goto end;
    }
  }

end:
  if(br) OCSP_BASICRESP_free(br);
  OCSP_RESPONSE_free(rsp);

  return result;
}
#endif

#endif /* USE_OPENSSL */

/* The SSL_CTRL_SET_MSG_CALLBACK doesn't exist in ancient OpenSSL versions
   and thus this cannot be done there. */
#ifdef SSL_CTRL_SET_MSG_CALLBACK

static const char *ssl_msg_type(int ssl_ver, int msg)
{
#ifdef SSL2_VERSION_MAJOR
  if(ssl_ver == SSL2_VERSION_MAJOR) {
    switch (msg) {
      case SSL2_MT_ERROR:
        return "Error";
      case SSL2_MT_CLIENT_HELLO:
        return "Client hello";
      case SSL2_MT_CLIENT_MASTER_KEY:
        return "Client key";
      case SSL2_MT_CLIENT_FINISHED:
        return "Client finished";
      case SSL2_MT_SERVER_HELLO:
        return "Server hello";
      case SSL2_MT_SERVER_VERIFY:
        return "Server verify";
      case SSL2_MT_SERVER_FINISHED:
        return "Server finished";
      case SSL2_MT_REQUEST_CERTIFICATE:
        return "Request CERT";
      case SSL2_MT_CLIENT_CERTIFICATE:
        return "Client CERT";
    }
  }
  else
#endif
  if(ssl_ver == SSL3_VERSION_MAJOR) {
    switch (msg) {
      case SSL3_MT_HELLO_REQUEST:
        return "Hello request";
      case SSL3_MT_CLIENT_HELLO:
        return "Client hello";
      case SSL3_MT_SERVER_HELLO:
        return "Server hello";
#ifdef SSL3_MT_NEWSESSION_TICKET
      case SSL3_MT_NEWSESSION_TICKET:
        return "Newsession Ticket";
#endif
      case SSL3_MT_CERTIFICATE:
        return "Certificate";
      case SSL3_MT_SERVER_KEY_EXCHANGE:
        return "Server key exchange";
      case SSL3_MT_CLIENT_KEY_EXCHANGE:
        return "Client key exchange";
      case SSL3_MT_CERTIFICATE_REQUEST:
        return "Request CERT";
      case SSL3_MT_SERVER_DONE:
        return "Server finished";
      case SSL3_MT_CERTIFICATE_VERIFY:
        return "CERT verify";
      case SSL3_MT_FINISHED:
        return "Finished";
#ifdef SSL3_MT_CERTIFICATE_STATUS
      case SSL3_MT_CERTIFICATE_STATUS:
        return "Certificate Status";
#endif
    }
  }
  return "Unknown";
}

static const char *tls_rt_type(int type)
{
  switch(type) {
#ifdef SSL3_RT_HEADER
  case SSL3_RT_HEADER:
    return "TLS header";
#endif
  case SSL3_RT_CHANGE_CIPHER_SPEC:
    return "TLS change cipher";
  case SSL3_RT_ALERT:
    return "TLS alert";
  case SSL3_RT_HANDSHAKE:
    return "TLS handshake";
  case SSL3_RT_APPLICATION_DATA:
    return "TLS app data";
  default:
    return "TLS Unknown";
  }
}


/*
 * Our callback from the SSL/TLS layers.
 */
static void ssl_tls_trace(int direction, int ssl_ver, int content_type,
                          const void *buf, size_t len, SSL *ssl,
                          void *userp)
{
  struct SessionHandle *data;
  const char *msg_name, *tls_rt_name;
  char ssl_buf[1024];
  char unknown[32];
  int msg_type, txt_len;
  const char *verstr = NULL;
  struct connectdata *conn = userp;

  if(!conn || !conn->data || !conn->data->set.fdebug ||
     (direction != 0 && direction != 1))
    return;

  data = conn->data;

  switch(ssl_ver) {
#ifdef SSL2_VERSION /* removed in recent versions */
  case SSL2_VERSION:
    verstr = "SSLv2";
    break;
#endif
#ifdef SSL3_VERSION
  case SSL3_VERSION:
    verstr = "SSLv3";
    break;
#endif
  case TLS1_VERSION:
    verstr = "TLSv1.0";
    break;
#ifdef TLS1_1_VERSION
  case TLS1_1_VERSION:
    verstr = "TLSv1.1";
    break;
#endif
#ifdef TLS1_2_VERSION
  case TLS1_2_VERSION:
    verstr = "TLSv1.2";
    break;
#endif
  case 0:
    break;
  default:
    snprintf(unknown, sizeof(unknown), "(%x)", ssl_ver);
    verstr = unknown;
    break;
  }

  if(ssl_ver) {
    /* the info given when the version is zero is not that useful for us */

    ssl_ver >>= 8; /* check the upper 8 bits only below */

    /* SSLv2 doesn't seem to have TLS record-type headers, so OpenSSL
     * always pass-up content-type as 0. But the interesting message-type
     * is at 'buf[0]'.
     */
    if(ssl_ver == SSL3_VERSION_MAJOR && content_type)
      tls_rt_name = tls_rt_type(content_type);
    else
      tls_rt_name = "";

    msg_type = *(char*)buf;
    msg_name = ssl_msg_type(ssl_ver, msg_type);

    txt_len = snprintf(ssl_buf, sizeof(ssl_buf), "%s (%s), %s, %s (%d):\n",
                       verstr, direction?"OUT":"IN",
                       tls_rt_name, msg_name, msg_type);
    Curl_debug(data, CURLINFO_TEXT, ssl_buf, (size_t)txt_len, NULL);
  }

  Curl_debug(data, (direction == 1) ? CURLINFO_SSL_DATA_OUT :
             CURLINFO_SSL_DATA_IN, (char *)buf, len, NULL);
  (void) ssl;
}
#endif

#ifdef USE_OPENSSL
/* ====================================================== */

#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
#  define use_sni(x)  sni = (x)
#else
#  define use_sni(x)  Curl_nop_stmt
#endif

/* Check for OpenSSL 1.0.2 which has ALPN support. */
#undef HAS_ALPN
#if OPENSSL_VERSION_NUMBER >= 0x10002000L \
    && !defined(OPENSSL_NO_TLSEXT)
#  define HAS_ALPN 1
#endif

/* Check for OpenSSL 1.0.1 which has NPN support. */
#undef HAS_NPN
#if OPENSSL_VERSION_NUMBER >= 0x10001000L \
    && !defined(OPENSSL_NO_TLSEXT) \
    && !defined(OPENSSL_NO_NEXTPROTONEG)
#  define HAS_NPN 1
#endif

#ifdef HAS_NPN

/*
 * in is a list of lenght prefixed strings. this function has to select
 * the protocol we want to use from the list and write its string into out.
 */

static int
select_next_protocol(unsigned char **out, unsigned char *outlen,
                     const unsigned char *in, unsigned int inlen,
                     const char *key, unsigned int keylen)
{
  unsigned int i;
  for(i = 0; i + keylen <= inlen; i += in[i] + 1) {
    if(memcmp(&in[i + 1], key, keylen) == 0) {
      *out = (unsigned char *) &in[i + 1];
      *outlen = in[i];
      return 0;
    }
  }
  return -1;
}

static int
select_next_proto_cb(SSL *ssl,
                     unsigned char **out, unsigned char *outlen,
                     const unsigned char *in, unsigned int inlen,
                     void *arg)
{
  struct connectdata *conn = (struct connectdata*) arg;

  (void)ssl;

#ifdef USE_NGHTTP2
  if(conn->data->set.httpversion >= CURL_HTTP_VERSION_2 &&
     !select_next_protocol(out, outlen, in, inlen, NGHTTP2_PROTO_VERSION_ID,
                           NGHTTP2_PROTO_VERSION_ID_LEN)) {
    infof(conn->data, "NPN, negotiated HTTP2 (%s)\n",
          NGHTTP2_PROTO_VERSION_ID);
    conn->negnpn = CURL_HTTP_VERSION_2;
    return SSL_TLSEXT_ERR_OK;
  }
#endif

  if(!select_next_protocol(out, outlen, in, inlen, ALPN_HTTP_1_1,
                           ALPN_HTTP_1_1_LENGTH)) {
    infof(conn->data, "NPN, negotiated HTTP1.1\n");
    conn->negnpn = CURL_HTTP_VERSION_1_1;
    return SSL_TLSEXT_ERR_OK;
  }

  infof(conn->data, "NPN, no overlap, use HTTP1.1\n");
  *out = (unsigned char *)ALPN_HTTP_1_1;
  *outlen = ALPN_HTTP_1_1_LENGTH;
  conn->negnpn = CURL_HTTP_VERSION_1_1;

  return SSL_TLSEXT_ERR_OK;
}
#endif /* HAS_NPN */

static const char *
get_ssl_version_txt(SSL *ssl)
{
  if(!ssl)
    return "";

  switch(SSL_version(ssl)) {
#if OPENSSL_VERSION_NUMBER >= 0x1000100FL
  case TLS1_2_VERSION:
    return "TLSv1.2";
  case TLS1_1_VERSION:
    return "TLSv1.1";
#endif
  case TLS1_VERSION:
    return "TLSv1.0";
  case SSL3_VERSION:
    return "SSLv3";
  case SSL2_VERSION:
    return "SSLv2";
  }
  return "unknown";
}

static CURLcode ossl_connect_step1(struct connectdata *conn, int sockindex)
{
  CURLcode result = CURLE_OK;
  char *ciphers;
  struct SessionHandle *data = conn->data;
  SSL_METHOD_QUAL SSL_METHOD *req_method = NULL;
  void *ssl_sessionid = NULL;
  X509_LOOKUP *lookup = NULL;
  curl_socket_t sockfd = conn->sock[sockindex];
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  long ctx_options;
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
  bool sni;
#ifdef ENABLE_IPV6
  struct in6_addr addr;
#else
  struct in_addr addr;
#endif
#endif

  DEBUGASSERT(ssl_connect_1 == connssl->connecting_state);

  /* Make funny stuff to get random input */
  Curl_ossl_seed(data);

  data->set.ssl.certverifyresult = !X509_V_OK;

  /* check to see if we've been told to use an explicit SSL/TLS version */

  switch(data->set.ssl.version) {
  default:
  case CURL_SSLVERSION_DEFAULT:
  case CURL_SSLVERSION_TLSv1:
  case CURL_SSLVERSION_TLSv1_0:
  case CURL_SSLVERSION_TLSv1_1:
  case CURL_SSLVERSION_TLSv1_2:
    /* it will be handled later with the context options */
#if (OPENSSL_VERSION_NUMBER >= 0x10100000L) && \
    !defined(LIBRESSL_VERSION_NUMBER)
    req_method = TLS_client_method();
#else
    req_method = SSLv23_client_method();
#endif
    use_sni(TRUE);
    break;
  case CURL_SSLVERSION_SSLv2:
#ifdef OPENSSL_NO_SSL2
    failf(data, OSSL_PACKAGE " was built without SSLv2 support");
    return CURLE_NOT_BUILT_IN;
#else
#ifdef USE_TLS_SRP
    if(data->set.ssl.authtype == CURL_TLSAUTH_SRP)
      return CURLE_SSL_CONNECT_ERROR;
#endif
    req_method = SSLv2_client_method();
    use_sni(FALSE);
    break;
#endif
  case CURL_SSLVERSION_SSLv3:
#ifdef OPENSSL_NO_SSL3_METHOD
    failf(data, OSSL_PACKAGE " was built without SSLv3 support");
    return CURLE_NOT_BUILT_IN;
#else
#ifdef USE_TLS_SRP
    if(data->set.ssl.authtype == CURL_TLSAUTH_SRP)
      return CURLE_SSL_CONNECT_ERROR;
#endif
    req_method = SSLv3_client_method();
    use_sni(FALSE);
    break;
#endif
  }

  if(connssl->ctx)
    SSL_CTX_free(connssl->ctx);
  connssl->ctx = SSL_CTX_new(req_method);

  if(!connssl->ctx) {
    failf(data, "SSL: couldn't create a context: %s",
          ERR_error_string(ERR_peek_error(), NULL));
    return CURLE_OUT_OF_MEMORY;
  }

#ifdef SSL_MODE_RELEASE_BUFFERS
  SSL_CTX_set_mode(connssl->ctx, SSL_MODE_RELEASE_BUFFERS);
#endif

#ifdef SSL_CTRL_SET_MSG_CALLBACK
  if(data->set.fdebug && data->set.verbose) {
    /* the SSL trace callback is only used for verbose logging */
    SSL_CTX_set_msg_callback(connssl->ctx, ssl_tls_trace);
    SSL_CTX_set_msg_callback_arg(connssl->ctx, conn);
  }
#endif

  /* OpenSSL contains code to work-around lots of bugs and flaws in various
     SSL-implementations. SSL_CTX_set_options() is used to enabled those
     work-arounds. The man page for this option states that SSL_OP_ALL enables
     all the work-arounds and that "It is usually safe to use SSL_OP_ALL to
     enable the bug workaround options if compatibility with somewhat broken
     implementations is desired."

     The "-no_ticket" option was introduced in Openssl0.9.8j. It's a flag to
     disable "rfc4507bis session ticket support".  rfc4507bis was later turned
     into the proper RFC5077 it seems: https://tools.ietf.org/html/rfc5077

     The enabled extension concerns the session management. I wonder how often
     libcurl stops a connection and then resumes a TLS session. also, sending
     the session data is some overhead. .I suggest that you just use your
     proposed patch (which explicitly disables TICKET).

     If someone writes an application with libcurl and openssl who wants to
     enable the feature, one can do this in the SSL callback.

     SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG option enabling allowed proper
     interoperability with web server Netscape Enterprise Server 2.0.1 which
     was released back in 1996.

     Due to CVE-2010-4180, option SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG has
     become ineffective as of OpenSSL 0.9.8q and 1.0.0c. In order to mitigate
     CVE-2010-4180 when using previous OpenSSL versions we no longer enable
     this option regardless of OpenSSL version and SSL_OP_ALL definition.

     OpenSSL added a work-around for a SSL 3.0/TLS 1.0 CBC vulnerability
     (https://www.openssl.org/~bodo/tls-cbc.txt). In 0.9.6e they added a bit to
     SSL_OP_ALL that _disables_ that work-around despite the fact that
     SSL_OP_ALL is documented to do "rather harmless" workarounds. In order to
     keep the secure work-around, the SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS bit
     must not be set.
  */

  ctx_options = SSL_OP_ALL;

#ifdef SSL_OP_NO_TICKET
  ctx_options |= SSL_OP_NO_TICKET;
#endif

#ifdef SSL_OP_NO_COMPRESSION
  ctx_options |= SSL_OP_NO_COMPRESSION;
#endif

#ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG
  /* mitigate CVE-2010-4180 */
  ctx_options &= ~SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG;
#endif

#ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
  /* unless the user explicitly ask to allow the protocol vulnerability we
     use the work-around */
  if(!conn->data->set.ssl_enable_beast)
    ctx_options &= ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
#endif

  switch(data->set.ssl.version) {
  case CURL_SSLVERSION_SSLv3:
#ifdef USE_TLS_SRP
    if(data->set.ssl.authtype == CURL_TLSAUTH_SRP) {
      infof(data, "Set version TLSv1.x for SRP authorisation\n");
    }
#endif
    ctx_options |= SSL_OP_NO_SSLv2;
    ctx_options |= SSL_OP_NO_TLSv1;
#if OPENSSL_VERSION_NUMBER >= 0x1000100FL
    ctx_options |= SSL_OP_NO_TLSv1_1;
    ctx_options |= SSL_OP_NO_TLSv1_2;
#endif
    break;

  case CURL_SSLVERSION_DEFAULT:
  case CURL_SSLVERSION_TLSv1:
    ctx_options |= SSL_OP_NO_SSLv2;
    ctx_options |= SSL_OP_NO_SSLv3;
    break;

  case CURL_SSLVERSION_TLSv1_0:
    ctx_options |= SSL_OP_NO_SSLv2;
    ctx_options |= SSL_OP_NO_SSLv3;
#if OPENSSL_VERSION_NUMBER >= 0x1000100FL
    ctx_options |= SSL_OP_NO_TLSv1_1;
    ctx_options |= SSL_OP_NO_TLSv1_2;
#endif
    break;

#if OPENSSL_VERSION_NUMBER >= 0x1000100FL
  case CURL_SSLVERSION_TLSv1_1:
    ctx_options |= SSL_OP_NO_SSLv2;
    ctx_options |= SSL_OP_NO_SSLv3;
    ctx_options |= SSL_OP_NO_TLSv1;
    ctx_options |= SSL_OP_NO_TLSv1_2;
    break;

  case CURL_SSLVERSION_TLSv1_2:
    ctx_options |= SSL_OP_NO_SSLv2;
    ctx_options |= SSL_OP_NO_SSLv3;
    ctx_options |= SSL_OP_NO_TLSv1;
    ctx_options |= SSL_OP_NO_TLSv1_1;
    break;
#endif

#ifndef OPENSSL_NO_SSL2
  case CURL_SSLVERSION_SSLv2:
    ctx_options |= SSL_OP_NO_SSLv3;
    ctx_options |= SSL_OP_NO_TLSv1;
#if OPENSSL_VERSION_NUMBER >= 0x1000100FL
    ctx_options |= SSL_OP_NO_TLSv1_1;
    ctx_options |= SSL_OP_NO_TLSv1_2;
#endif
    break;
#endif

  default:
    failf(data, "Unsupported SSL protocol version");
    return CURLE_SSL_CONNECT_ERROR;
  }

  SSL_CTX_set_options(connssl->ctx, ctx_options);

#ifdef HAS_NPN
  if(conn->bits.tls_enable_npn)
    SSL_CTX_set_next_proto_select_cb(connssl->ctx, select_next_proto_cb, conn);
#endif

#ifdef HAS_ALPN
  if(conn->bits.tls_enable_alpn) {
    int cur = 0;
    unsigned char protocols[128];

#ifdef USE_NGHTTP2
    if(data->set.httpversion >= CURL_HTTP_VERSION_2) {
      protocols[cur++] = NGHTTP2_PROTO_VERSION_ID_LEN;

      memcpy(&protocols[cur], NGHTTP2_PROTO_VERSION_ID,
          NGHTTP2_PROTO_VERSION_ID_LEN);
      cur += NGHTTP2_PROTO_VERSION_ID_LEN;
      infof(data, "ALPN, offering %s\n", NGHTTP2_PROTO_VERSION_ID);
    }
#endif

    protocols[cur++] = ALPN_HTTP_1_1_LENGTH;
    memcpy(&protocols[cur], ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH);
    cur += ALPN_HTTP_1_1_LENGTH;
    infof(data, "ALPN, offering %s\n", ALPN_HTTP_1_1);

    /* expects length prefixed preference ordered list of protocols in wire
     * format
     */
    SSL_CTX_set_alpn_protos(connssl->ctx, protocols, cur);
  }
#endif

  if(data->set.str[STRING_CERT] || data->set.str[STRING_CERT_TYPE]) {
    if(!cert_stuff(conn,
                   connssl->ctx,
                   data->set.str[STRING_CERT],
                   data->set.str[STRING_CERT_TYPE],
                   data->set.str[STRING_KEY],
                   data->set.str[STRING_KEY_TYPE])) {
      /* failf() is already done in cert_stuff() */
      return CURLE_SSL_CERTPROBLEM;
    }
  }

  ciphers = data->set.str[STRING_SSL_CIPHER_LIST];
  if(!ciphers)
    ciphers = (char *)DEFAULT_CIPHER_SELECTION;
  if(!SSL_CTX_set_cipher_list(connssl->ctx, ciphers)) {
    failf(data, "failed setting cipher list: %s", ciphers);
    return CURLE_SSL_CIPHER;
  }
  infof(data, "Cipher selection: %s\n", ciphers);

#ifdef USE_TLS_SRP
  if(data->set.ssl.authtype == CURL_TLSAUTH_SRP) {
    infof(data, "Using TLS-SRP username: %s\n", data->set.ssl.username);

    if(!SSL_CTX_set_srp_username(connssl->ctx, data->set.ssl.username)) {
      failf(data, "Unable to set SRP user name");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
    if(!SSL_CTX_set_srp_password(connssl->ctx, data->set.ssl.password)) {
      failf(data, "failed setting SRP password");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
    if(!data->set.str[STRING_SSL_CIPHER_LIST]) {
      infof(data, "Setting cipher list SRP\n");

      if(!SSL_CTX_set_cipher_list(connssl->ctx, "SRP")) {
        failf(data, "failed setting SRP cipher list");
        return CURLE_SSL_CIPHER;
      }
    }
  }
#endif
  if(data->set.str[STRING_SSL_CAFILE] || data->set.str[STRING_SSL_CAPATH]) {
    /* tell SSL where to find CA certificates that are used to verify
       the servers certificate. */
    if(!SSL_CTX_load_verify_locations(connssl->ctx,
                                       data->set.str[STRING_SSL_CAFILE],
                                       data->set.str[STRING_SSL_CAPATH])) {
      if(data->set.ssl.verifypeer) {
        /* Fail if we insist on successfully verifying the server. */
        failf(data, "error setting certificate verify locations:\n"
              "  CAfile: %s\n  CApath: %s",
              data->set.str[STRING_SSL_CAFILE]?
              data->set.str[STRING_SSL_CAFILE]: "none",
              data->set.str[STRING_SSL_CAPATH]?
              data->set.str[STRING_SSL_CAPATH] : "none");
        return CURLE_SSL_CACERT_BADFILE;
      }
      else {
        /* Just continue with a warning if no strict  certificate verification
           is required. */
        infof(data, "error setting certificate verify locations,"
              " continuing anyway:\n");
      }
    }
    else {
      /* Everything is fine. */
      infof(data, "successfully set certificate verify locations:\n");
    }
    infof(data,
          "  CAfile: %s\n"
          "  CApath: %s\n",
          data->set.str[STRING_SSL_CAFILE] ? data->set.str[STRING_SSL_CAFILE]:
          "none",