CURLOPT_USE_SSL(3) Library Functions Manual CURLOPT_USE_SSL(3)

CURLOPT_USE_SSL - request using SSL / TLS for the transfer

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USE_SSL, long level);

Pass a long using one of the values from below, to make libcurl use your desired level of SSL for the transfer.

These are all protocols that start out plain text and get "upgraded" to SSL using the STARTTLS command.

This is for enabling SSL/TLS when you use FTP, SMTP, POP3, IMAP etc.

do not attempt to use SSL.
Try using SSL, proceed as normal otherwise. Note that server may close the connection if the negotiation does not succeed.
Require SSL for the control connection or fail with CURLE_USE_SSL_FAILED.
Require SSL for all communication or fail with CURLE_USE_SSL_FAILED.

CURLUSESSL_NONE

FTP, IMAP, POP3 and SMTP

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/dir/file.ext");
    /* require use of SSL for this, or fail */
    curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
    /* Perform the request */
    curl_easy_perform(curl);
  }
}

Added in 7.11.0. This option was known as CURLOPT_FTP_SSL up to 7.16.4, and the constants were known as CURLFTPSSL_* Handled by LDAP since 7.81.0. Fully supported by the OpenLDAP backend only.

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

CURLOPT_PROXY_SSLVERSION(3), CURLOPT_SSLVERSION(3), CURLOPT_SSL_OPTIONS(3)

April 26 2024 libcurl