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| .TH CURLOPT_SSL_CTX_FUNCTION 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options" |
| .SH NAME |
| CURLOPT_SSL_CTX_FUNCTION \- SSL context callback for OpenSSL, wolfSSL or mbedTLS |
| .SH SYNOPSIS |
| .nf |
| #include <curl/curl.h> |
| |
| CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr); |
| |
| CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION, |
| ssl_ctx_callback); |
| .SH DESCRIPTION |
| This option only works for libcurl powered by OpenSSL, wolfSSL or mbedTLS. If |
| libcurl was built against another SSL library this functionality is absent. |
| |
| Pass a pointer to your callback function, which should match the prototype |
| shown above. |
| |
| This callback function gets called by libcurl just before the initialization |
| of an SSL connection after having processed all other SSL related options to |
| give a last chance to an application to modify the behavior of the SSL |
| initialization. The \fIssl_ctx\fP parameter is actually a pointer to the SSL |
| library's \fISSL_CTX\fP for OpenSSL or wolfSSL, and a pointer to |
| \fImbedtls_ssl_config\fP for mbedTLS. If an error is returned from the |
| callback no attempt to establish a connection is made and the perform |
| operation will return the callback's error code. Set the \fIuserptr\fP |
| argument with the \fICURLOPT_SSL_CTX_DATA(3)\fP option. |
| |
| This function will get called on all new connections made to a server, during |
| the SSL negotiation. The \fIssl_ctx\fP will point to a newly initialized object |
| each time, but note the pointer may be the same as from a prior call. |
| |
| To use this properly, a non-trivial amount of knowledge of your SSL library is |
| necessary. For example, you can use this function to call library-specific |
| callbacks to add additional validation code for certificates, and even to |
| change the actual URI of an HTTPS request. |
| |
| WARNING: The \fICURLOPT_SSL_CTX_FUNCTION(3)\fP callback allows the application |
| to reach in and modify SSL details in the connection without libcurl itself |
| knowing anything about it, which then subsequently can lead to libcurl |
| unknowingly reusing SSL connections with different properties. To remedy this |
| you may set \fICURLOPT_FORBID_REUSE(3)\fP from the callback function. |
| .SH DEFAULT |
| NULL |
| .SH PROTOCOLS |
| All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. |
| .SH EXAMPLE |
| See cacertinmem.c in docs/examples directory for usage example. |
| |
| https://curl.haxx.se/libcurl/c/cacertinmem.html |
| .SH AVAILABILITY |
| Added in 7.11.0 for OpenSSL, in 7.42.0 for wolfSSL and in 7.54.0 for |
| mbedTLS. Other SSL backends are not supported. |
| .SH RETURN VALUE |
| CURLE_OK if supported; or an error such as: |
| |
| CURLE_NOT_BUILT_IN - Not supported by the SSL backend |
| |
| CURLE_UNKNOWN_OPTION |
| .SH "SEE ALSO" |
| .BR CURLOPT_SSL_CTX_DATA "(3), " CURLOPT_SSL_VERIFYPEER "(3), " |
