Daniel Stenberg e694c8284a

docs/libcurl/opts: clarify the return values

Expand a little.

- mention the type name of the return code
- avoid stating which exact return codes that might be returned, as that
  varies over time, builds and conditions
- avoid stating some always return OK
- refer to the manpage documenting all the return codes

Closes #15900

2025-01-02 17:13:33 +01:00

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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

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).

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