NAME¶

CURLOPT_USE_SSL - request using SSL / TLS for the transfer

SYNOPSIS¶

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

DESCRIPTION¶

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 fails. This level is insecure and should be avoided since it allows the connection to remain unprotected.

CURLUSESSL_CONTROL

Require SSL for the control connection or fail with CURLE_USE_SSL_FAILED. This level is partially insecure and should be avoided since it lets the data connection remain unprotected.

This level is meant for FTP, since that is the only protocol with separate connections for control and data. If used for IMAP, POP3 or SMTP it equals CURLUSESSL_ALL.

CURLUSESSL_ALL

Require SSL for all communication or fail with CURLE_USE_SSL_FAILED.

DEFAULT¶

CURLUSESSL_NONE

PROTOCOLS¶

This functionality affects ftp, imap, pop3 and smtp

EXAMPLE¶

int main(void)
{


  CURL *curl = curl_easy_init();


  if(curl) {


    CURLcode result;


    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, CURLUSESSL_ALL);


    /* Perform the request */


    result = curl_easy_perform(curl);


    curl_easy_cleanup(curl);


  }
}

HISTORY¶

This option was known as CURLOPT_FTP_SSL up to 7.16.4. Supported by LDAP since 7.81.0. Fully supported by the OpenLDAP backend only.

CURLUSESSL_* enums became long types in 8.13.0, prior to this version a long cast was necessary when passed to curl_easy_setopt(3).

AVAILABILITY¶

Added in curl 7.17.0

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).

SEE ALSO¶

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