Tribblix: manual page: CURLOPT_SSL_CIPHER

CURLOPT_SSL_CIPHER_LIST(3) Introduction to Library Functions

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 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.

DEFAULT

NULL, use built-in list

PROTOCOLS

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

EXAMPLE

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);
}
}

HISTORY

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.

AVAILABILITY

Added in curl 7.9

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).