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CURLOPT_PROXY_TLS13_CIPHERS - ciphers suites for proxy TLS 1.3 #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_TLS13_CIPHERS, char *list); Pass a char *, pointing to a null-terminated string holding the list of cipher suites to use for the TLS 1.3 connection to a proxy. The list must be syntactically correct, it consists of one or more cipher suite strings separated by colons. You'll find more details about cipher lists on this URL: https://curl.haxx.se/docs/ssl-ciphers.html This option is currently used only when curl is built to use OpenSSL 1.1.1 or later. If you are using a different SSL backend you can try setting TLS 1.3 cipher suites by using the CURLOPT_PROXY_SSL_CIPHER_LIST option. The application does not have to keep the string around after setting this option. NULL, use internal default All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

CURL *curl = curl_easy_init();
if(curl) {
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
 curl_easy_setopt(curl, CURLOPT_PROXY_TLS13_CIPHERS,
 "TLS13-CHACHA20-POLY1305-SHA256");
 ret = curl_easy_perform(curl);
 curl_easy_cleanup(curl);
}

Added in 7.61.0. Available when built with OpenSSL >= 1.1.1. Returns CURLE_OK if supported, CURLE_NOT_BUILT_IN otherwise. CURLOPT_PROXY_SSL_CIPHER_LIST "(3), " CURLOPT_PROXY_SSLVERSION "(3), " CURLOPT_SSL_CIPHER_LIST "(3), " CURLOPT_TLS13_CIPHERS "(3), " CURLOPT_SSLVERSION "(3), "