CURLOPT_USE_SSL - Man Page

#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.

CURLUSESSL_NONE

do not attempt to use SSL.

CURLUSESSL_TRY

Try using SSL, proceed as normal otherwise. Note that server may close the connection if the negotiation does not succeed.

CURLUSESSL_CONTROL

Require SSL for the control connection or fail with CURLE_USE_SSL_FAILED.

CURLUSESSL_ALL

Require SSL for all communication or fail with CURLE_USE_SSL_FAILED.

CURLUSESSL_NONE

This functionality affects 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);
  }
}

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.

Added in curl 7.17.0

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)

curl_easy_setopt(3), CURLINFO_TLS_SSL_PTR(3), CURLOPT_FTPSSLAUTH(3), CURLOPT_FTP_SSL_CCC(3), CURLOPT_KRBLEVEL(3), CURLOPT_PROXY_SSLVERSION(3), CURLOPT_SSL_CIPHER_LIST(3), CURLOPT_SSLVERSION(3), CURLOPT_TLS13_CIPHERS(3), libcurl-security(3), libcurl-symbols(3).