CURLOPT_FTP_SSL_CCC(3) Library Functions Manual CURLOPT_FTP_SSL_CCC(3)

CURLOPT_FTP_SSL_CCC - switch off SSL again with FTP after auth

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

If enabled, this option makes libcurl use CCC (Clear Command Channel). It shuts down the SSL/TLS layer after authenticating. The rest of the control channel communication remains unencrypted. This allows NAT routers to follow the FTP transaction. Pass a long using one of the values below

do not attempt to use CCC.
Do not initiate the shutdown, but wait for the server to do it. Do not send a reply.
Initiate the shutdown and wait for a reply.

CURLFTPSSL_CCC_NONE

FTP

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
    curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_CONTROL);
    /* go back to clear-text FTP after authenticating */
    curl_easy_setopt(curl, CURLOPT_FTP_SSL_CCC, (long)CURLFTPSSL_CCC_ACTIVE);
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Added in 7.16.1

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

CURLOPT_FTPSSLAUTH(3), CURLOPT_PROTOCOLS_STR(3), CURLOPT_USE_SSL(3)

2024-05-22 libcurl