NAME

       CURLOPT_PROXY_SSL_OPTIONS - HTTPS proxy SSL behavior options

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_SSL_OPTIONS,
                                 long bitmask);

DESCRIPTION

       Pass a long with a bitmask to tell libcurl about specific SSL behaviors. Available bits:

       CURLSSLOPT_ALLOW_BEAST
              Tells  libcurl  to  not  attempt to use any workarounds for a security flaw in the SSL3 and TLS1.0
              protocols. If this option is not used or this bit is set to 0, the SSL layer libcurl uses may  use
              a  work-around  for  this flaw although it might cause interoperability problems with some (older)
              SSL implementations.  WARNING: avoiding this work-around lessens the security, and by setting this
              option to 1 you ask for exactly that. This option is  only  supported  for  Secure  Transport  and
              OpenSSL.

       CURLSSLOPT_NO_REVOKE
              Tells  libcurl to disable certificate revocation checks for those SSL backends where such behavior
              is present. This option is only supported for Schannel (the native Windows SSL library),  with  an
              exception  in  the  case  of  Windows'  Untrusted  Publishers  block list which it seems cannot be
              bypassed.

       CURLSSLOPT_NO_PARTIALCHAIN
              Tells libcurl to not accept "partial" certificate chains, which it otherwise does by default. This
              option fails the certificate verification if the chain ends with an intermediate  certificate  and
              not with a root cert.

              Works with OpenSSL and its forks (LibreSSL, BoringSSL, etc). (Added in 7.68.0)

              Works with Schannel if the user specified certificates to verify the peer.  (Added in 8.15.0)

       CURLSSLOPT_REVOKE_BEST_EFFORT
              Tells  libcurl  to ignore certificate revocation checks in case of missing or offline distribution
              points for those SSL backends where such behavior is present. This option is  only  supported  for
              Schannel (the native Windows SSL library). If combined with CURLSSLOPT_NO_REVOKE, the latter takes
              precedence. (Added in 7.70.0)

       CURLSSLOPT_NATIVE_CA
              Tell  libcurl  to  use  the  operating system's native CA store for certificate verification. This
              option is independent of other CA certificate locations set at  run  time  or  build  time.  Those
              locations are searched in addition to the native CA store.

              Works  with  wolfSSL  on Windows, Linux (Debian, Ubuntu, Gentoo, Fedora, RHEL), macOS, Android and
              iOS (added in 8.3.0); with GnuTLS (added in 8.5.0) and  with  OpenSSL  and  its  forks  (LibreSSL,
              BoringSSL, etc) on Windows (Added in 7.71.0).

       CURLSSLOPT_AUTO_CLIENT_CERT
              Tell  libcurl  to  automatically  locate  and  use  a  client certificate for authentication, when
              requested by the server. This option is only  supported  for  Schannel  (the  native  Windows  SSL
              library). Prior to 7.77.0 this was the default behavior in libcurl with Schannel. Since the server
              can  request  any  certificate  that supports client authentication in the OS certificate store it
              could be a privacy violation and unexpected.  (Added in 7.77.0)

DEFAULT

       0

PROTOCOLS

       This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

       All TLS backends support this option.

EXAMPLE

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode res;
           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
           curl_easy_setopt(curl, CURLOPT_PROXY, "https://proxy");
           /* weaken TLS only for use with silly proxies */
           curl_easy_setopt(curl, CURLOPT_PROXY_SSL_OPTIONS,
                            CURLSSLOPT_ALLOW_BEAST | CURLSSLOPT_NO_REVOKE);
           res = curl_easy_perform(curl);
           curl_easy_cleanup(curl);
         }
       }

HISTORY

       CURLSSLOPT_* macros became long types in 8.15.0, prior to this version a long  cast  was  necessary  when
       passed to curl_easy_setopt(3).

AVAILABILITY

       Added in curl 7.52.0

RETURN VALUE

       curl_easy_setopt(3) returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

SEE ALSO

       CURLOPT_PROXY_SSLVERSION(3),           CURLOPT_PROXY_SSL_CIPHER_LIST(3),           CURLOPT_SSLVERSION(3),
       CURLOPT_SSL_CIPHER_LIST(3)

libcurl                                            2025-11-07                       CURLOPT_PROXY_SSL_OPTIONS(3)