Ubuntu Manpage: CURLOPT_SSL_CIPHER_LIST

NAME

       CURLOPT_SSL_CIPHER_LIST - ciphers to use for TLS

SYNOPSIS

       #include <curl/curl.h>

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

DESCRIPTION

Pass a char *, pointing to a null-terminated string holding the list of ciphers to use for
the SSL connection. The list must be syntactically correct, it consists of one or more
cipher strings separated by colons. Commas or spaces are also acceptable separators but
colons are normally used, !, - and + can be used as operators.

For OpenSSL and GnuTLS valid examples of cipher lists include RC4-SHA, SHA1+DES, TLSv1 and
DEFAULT. The default list is normally set when you compile OpenSSL.

For NSS, valid examples of cipher lists include rsa_rc4_128_md5, rsa_aes_128_sha, etc.
With NSS you do not add/remove ciphers. If one uses this option then all known ciphers are
disabled and only those passed in are enabled.

For WolfSSL, valid examples of cipher lists include ECDHE-RSA-RC4-SHA,
AES256-SHA:AES256-SHA256, etc.

For BearSSL, valid examples of cipher lists include ECDHE-RSA-CHACHA20-POLY1305:ECDHE-RSA-
AES128-GCM-SHA256, or when using IANA names
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256:TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, etc.
With BearSSL you do not add/remove ciphers. If one uses this option then all known ciphers
are disabled and only those passed in are enabled.

you will 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.

DEFAULT

       NULL, use internal default

PROTOCOLS

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

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
         curl_easy_setopt(curl, CURLOPT_SSL_CIPHER_LIST, "TLSv1");
         ret = curl_easy_perform(curl);
         curl_easy_cleanup(curl);
       }

AVAILABILITY

       Added in 7.9, in 7.83.0 for BearSSL

       If built TLS enabled.

RETURN VALUE

       Returns CURLE_OK if TLS is supported, CURLE_UNKNOWN_OPTION if not, or  CURLE_OUT_OF_MEMORY
       if there was insufficient heap space.