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CURLOPT_SSL_CTX_DATA(3)             libcurl            CURLOPT_SSL_CTX_DATA(3)

NAME
       CURLOPT_SSL_CTX_DATA - pointer passed to SSL context callback

SYNOPSIS
       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void *pointer);

DESCRIPTION
       Data pointer to pass to the ssl context callback set by the option
       CURLOPT_SSL_CTX_FUNCTION(3), this is the pointer you will get as third
       parameter.

DEFAULT
       NULL

PROTOCOLS
       All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

EXAMPLE
       /* OpenSSL specific */

       #include <openssl/ssl.h>
       #include <curl/curl.h>
       #include <stdio.h>

       static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
       {
         X509_STORE *store;
         X509 *cert = NULL;
         BIO *bio;
         char *mypem = parm;
         /* get a BIO */
         bio = BIO_new_mem_buf(mypem, -1);
         /* use it to read the PEM formatted certificate from memory into an
          * X509 structure that SSL can use
          */
         PEM_read_bio_X509(bio, &cert, 0, NULL);
         if(cert == NULL)
           printf("PEM_read_bio_X509 failed...\n");

         /* get a pointer to the X509 certificate store (which may be empty) */
         store = SSL_CTX_get_cert_store((SSL_CTX *)sslctx);

         /* add our certificate to this store */
         if(X509_STORE_add_cert(store, cert) == 0)
           printf("error adding certificate\n");

         /* decrease reference counts */
         X509_free(cert);
         BIO_free(bio);

         /* all set to go */
         return CURLE_OK;
       }

       int main(void)
       {
         CURL * ch;
         CURLcode rv;
         char *mypem = /* example CA cert PEM - shortened */
           "-----BEGIN CERTIFICATE-----\n"
           "MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290\n"
           "IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNB\n"
           "IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRA\n"
           "Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAO\n"
           "GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzk\n"
           "zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmW\n"
           "omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVD\n"
           "-----END CERTIFICATE-----\n";

         curl_global_init(CURL_GLOBAL_ALL);
         ch = curl_easy_init();

         curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
         curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
         curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");

         /* Retrieve page using cacerts' certificate -> will succeed
          * load the certificate by installing a function doing the necessary
          * "modifications" to the SSL CONTEXT just before link init
          */
         curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
         curl_easy_setopt(ch, CURLOPT_SSL_CTX_DATA, mypem);
         rv = curl_easy_perform(ch);
         if(!rv)
           printf("*** transfer succeeded ***\n");
         else
           printf("*** transfer failed ***\n");

         curl_easy_cleanup(ch);
         curl_global_cleanup();
         return rv;
       }

AVAILABILITY
       Added in 7.11.0 for OpenSSL, in 7.42.0 for wolfSSL, in 7.54.0 for
       mbedTLS, in 7.83.0 in BearSSL. Other SSL backends are not supported.

RETURN VALUE
       CURLE_OK if supported; or an error such as:

       CURLE_NOT_BUILT_IN - Not supported by the SSL backend

       CURLE_UNKNOWN_OPTION

SEE ALSO
       CURLOPT_SSL_CTX_FUNCTION(3), CURLOPT_SSLVERSION(3),

ibcurl 8.1.2                    April 26, 2023         CURLOPT_SSL_CTX_DATA(3)