---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_SSL_SIGNATURE_ALGORITHMS
Section: 3
Source: libcurl
See-also:
  - CURLOPT_SSL_CIPHER_LIST (3)
  - CURLOPT_SSL_EC_CURVES (3)
  - CURLOPT_SSLVERSION (3)
  - CURLOPT_USE_SSL (3)
Protocol:
  - TLS
TLS-backend:
  - OpenSSL
Added-in: 8.14.0
---

# NAME

CURLOPT_SSL_SIGNATURE_ALGORITHMS - signature algorithms to use for TLS

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_SIGNATURE_ALGORITHMS, char *list);
~~~

# DESCRIPTION

Pass a char pointer, pointing to a null-terminated string holding the list of
signature algorithms to use for the TLS connection. The list must be syntactically
correct, it consists of one or more signature algorithm strings separated by colons.

A valid example of a signature algorithms list with OpenSSL is:
~~~
"DSA+SHA256:rsa_pss_pss_sha256"
~~~

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.

Works with OpenSSL and its BoringSSL fork (added in 8.14.0).

# DEFAULT

NULL, use built-in list

# %PROTOCOLS%

# EXAMPLE

~~~c
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_SIGNATURE_ALGORITHMS,
                     "DSA+SHA256:rsa_pss_pss_sha256");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
~~~

# HISTORY

OpenSSL support added in 8.14.0.

# %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).