CURLOPT_SSL_CIPHER_LIST - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CIPHER_LIST, char *list);

Pass a char pointer, pointing to a null-terminated string holding the list of cipher suites to use for the TLS 1.2 (1.1, 1.0) connection. The list must be syntactically correct, it consists of one or more cipher suite strings separated by colons.

For setting TLS 1.3 ciphers see CURLOPT_TLS13_CIPHERS(3).

A valid example of a cipher list is:

"ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:"
"ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305"

For Schannel, you can use this option to set algorithms but not specific cipher suites. Refer to the ciphers lists document for algorithms.

Find more details about cipher lists on this URL:

https://curl.se/docs/ssl-ciphers.html

The application does not have to keep the string around after setting this option.

Using this option multiple times makes the last set string override the previous ones. Set it to NULL to disable its use again.

NULL, use built-in list

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

This option works only with the following TLS backends: BearSSL, OpenSSL, Schannel, Secure Transport, mbedTLS, rustls and wolfSSL

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_SSL_CIPHER_LIST,
                     "ECDHE-ECDSA-CHACHA20-POLY1305:"
                     "ECDHE-RSA-CHACHA20-POLY1305");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

OpenSSL support added in 7.9. wolfSSL support added in 7.53.0. Schannel support added in 7.61.0. Secure Transport support added in 7.77.0. BearSSL support added in 7.83.0. mbedTLS support added in 8.8.0. Rustls support added in 8.10.0.

Since curl 8.10.0 returns CURLE_NOT_BUILT_IN when not supported.

Added in curl 7.9

Returns CURLE_OK if supported, CURLE_NOT_BUILT_IN otherwise.

CURLOPT_PROXY_SSL_CIPHER_LIST(3), CURLOPT_PROXY_TLS13_CIPHERS(3), CURLOPT_SSLVERSION(3), CURLOPT_TLS13_CIPHERS(3), CURLOPT_USE_SSL(3)

curl_easy_setopt(3), CURLOPT_PROXY_SSL_CIPHER_LIST(3), CURLOPT_PROXY_SSL_OPTIONS(3), CURLOPT_PROXY_TLS13_CIPHERS(3), CURLOPT_SSL_EC_CURVES(3), CURLOPT_SSL_OPTIONS(3), CURLOPT_TLS13_CIPHERS(3), libcurl-symbols(3), nbdkit-curl-plugin(1).