Daniel Stenberg c4ab33370a

CURLOPT_*-docs: provide additional details

Went through CURLOPTTYPE_STRINGPOINT and CURLOPTTYPE_SLISTPOINT options
and clarified:

- what happens when setting the option *again*

- setting to NULL disables/restores to default

- libcurl does not copy the slist for options using a such

Closes #14846

2024-09-10 13:48:42 +02:00

2.4 KiB

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SPDX-License-Identifier

Title

Section

Source

See-also

Protocol

TLS-backend

Added-in

curl

CURLOPT_SSL_CIPHER_LIST

libcurl

CURLOPT_PROXY_SSL_CIPHER_LIST (3)

CURLOPT_PROXY_TLS13_CIPHERS (3)

CURLOPT_SSLVERSION (3)

CURLOPT_TLS13_CIPHERS (3)

CURLOPT_USE_SSL (3)

TLS

OpenSSL

BearSSL

Schannel

Secure Transport

wolfSSL

mbedTLS

rustls

7.9

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%

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%

RETURN VALUE

Returns CURLE_OK if supported, CURLE_NOT_BUILT_IN otherwise.

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