I have problems using the option CURLOPT_FTP_SSL. I set the option to
CURLFTPSSL_CONTROL and noticed that data and control channel are
encrypted. So there is no difference between the options
CURLFTPSSL_CONTROL and CURLFTPSSL_ALL.

Both are using the FTP command "PROT P". Option CURLFTPSSL_CONTROL
should use "PROT C" and open an unencrypted data channel. I noticed the
problem while the CPU usage did increase dramaticaly on connections which
should encrpyt the control channel only (for password encryption).

Here is the example program I used:

  #include <stdio.h>

  #include <curl/curl.h>
  #include <curl/types.h>
  #include <curl/easy.h>

  int main(void)
  {
    CURL *curl;
    CURLcode res;

    curl_global_init(CURL_GLOBAL_DEFAULT);

    curl = curl_easy_init();
    if(curl) {
      /*
       * Get curl 7.9.2 from sunet.se's FTP site. curl 7.9.2 is most
likely not
       * present there by the time you read this, so you'd better replace
the
       * URL with one that works!
       */
      curl_easy_setopt(curl, CURLOPT_URL,
                       "ftp://10.0.0.100/");
      /* Define our callback to get called when there's data to be written
*/
      /* Set a pointer to our struct to pass to the callback */

      /* Switch on full protocol/debug output */
      curl_easy_setopt(curl, CURLOPT_VERBOSE, TRUE);
      curl_easy_setopt(curl, CURLOPT_FTP_SSL, CURLFTPSSL_CONTROL);
      curl_easy_setopt(curl, CURLOPT_FTPSSLAUTH,CURLFTPAUTH_TLS);
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, FALSE );
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, FALSE);

      res = curl_easy_perform(curl);

      /* always cleanup */
      curl_easy_cleanup(curl);

      if(CURLE_OK != res) {
        /* we failed */
        fprintf(stderr, "curl told us %d\n", res);
      }
    }

    curl_global_cleanup();

    return 0;
  }

And here relevant part of the output:
> PBSZ 0
< 200 PBSZ 0 successful
> PROT P
< 200 Protection set to Private
> PWD
< 257 "/" is current directory.
* Entry path is '/'
> EPSV

I'm using libcurl 7.15.1 on AIX 5.3

Best regards

Peter Heuchert
Received on 2006-03-06