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CURLOPT_SSL_OPTIONS(3)              libcurl             CURLOPT_SSL_OPTIONS(3)


NAME

       CURLOPT_SSL_OPTIONS - SSL behavior options


SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_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, NSS 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. (Added in 7.44.0)

       CURLSSLOPT_NO_PARTIALCHAIN
              Tells libcurl to not accept "partial" certificate chains, which
              it otherwise does by default. This option is only supported for
              OpenSSL and will fail the certificate verification if the chain
              ends with an intermediate certificate and not with a root cert.
              (Added in 7.68.0)

       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. Works only on Windows when built to
              use OpenSSL. If you set this option and also set a CA
              certificate file or directory then during verification those
              certificates are searched in addition to the native CA store.
              (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

       All TLS-based protocols


EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
         /* weaken TLS only for use with silly servers */
         curl_easy_setopt(curl, CURLOPT_SSL_OPTIONS, (long)CURLSSLOPT_ALLOW_BEAST |
                          CURLSSLOPT_NO_REVOKE);
         ret = curl_easy_perform(curl);
         curl_easy_cleanup(curl);
       }


AVAILABILITY

       Added in 7.25.0


RETURN VALUE

       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
       if not.


SEE ALSO

       CURLOPT_SSLVERSION(3), CURLOPT_SSL_CIPHER_LIST(3),

ibcurl 8.1.2                    April 26, 2023          CURLOPT_SSL_OPTIONS(3)

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