NAME

       curl_global_sslset - select SSL backend to use

SYNOPSIS

       #include <curl/curl.h>

       CURLsslset curl_global_sslset(curl_sslbackend id,
                                     const char *name,
                                     const curl_ssl_backend ***avail);

DESCRIPTION

       This  function  configures at runtime which SSL backend to use with libcurl. This function
       can only  be  used  to  select  an  SSL  backend  once,  and  it  must  be  called  before
       curl_global_init(3).

       The  backend  can  be  identified by the id (e.g. CURLSSLBACKEND_OPENSSL). The backend can
       also  be  specified  via  the  name  parameter  for  a  case  insensitive  match  (passing
       CURLSSLBACKEND_NONE as id). If both id and name are specified, the name is ignored.

       If  neither  id nor name are specified, the function fails with CURLSSLSET_UNKNOWN_BACKEND
       and set the avail pointer to the NULL-terminated list of available backends. The available
       backends are those that this particular build of libcurl supports.

       Since  libcurl  7.60.0,  the  avail  pointer  is always set to the list of alternatives if
       non-NULL.

       Upon success, the function returns CURLSSLSET_OK.

       If   the   specified   SSL   backend   is   not   available,    the    function    returns
       CURLSSLSET_UNKNOWN_BACKEND  and  sets  the  avail  pointer  to  a  NULL-terminated list of
       available SSL backends. In this case, you may call the function again to try to  select  a
       different backend.

       The  SSL backend can be set only once. If it has already been set, a subsequent attempt to
       change it results in a CURLSSLSET_TOO_LATE getting returned.

       This function  is  thread-safe  since  libcurl  7.84.0  if  curl_version_info(3)  has  the
       CURL_VERSION_THREADSAFE feature bit set (most platforms).

       If  this  is not thread-safe, you must not call this function when any other thread in the
       program (i.e. a thread sharing the same memory) is running.  This does not  just  mean  no
       other thread that is using libcurl.

OpenSSL

       The name "OpenSSL" is used for all versions of OpenSSL and its associated forks/flavors in
       this function. OpenSSL, BoringSSL, LibreSSL, quictls  and  AmiSSL  are  all  supported  by
       libcurl,  but  in  the eyes of curl_global_sslset(3) they are all just "OpenSSL". They all
       mostly provide the same API.

       curl_version_info(3) can return more specific info about  the  exact  OpenSSL  flavor  and
       version number is use.

struct

       typedef struct {
         curl_sslbackend id;
         const char *name;
       } curl_ssl_backend;

       typedef enum {
         CURLSSLBACKEND_NONE = 0,
         CURLSSLBACKEND_OPENSSL = 1, /* or one of its forks */
         CURLSSLBACKEND_GNUTLS = 2,
         CURLSSLBACKEND_NSS = 3,
         CURLSSLBACKEND_GSKIT = 5, /* deprecated */
         CURLSSLBACKEND_POLARSSL = 6, /* deprecated */
         CURLSSLBACKEND_WOLFSSL = 7,
         CURLSSLBACKEND_SCHANNEL = 8,
         CURLSSLBACKEND_SECURETRANSPORT = 9,
         CURLSSLBACKEND_AXTLS = 10, /* deprecated */
         CURLSSLBACKEND_MBEDTLS = 11,
         CURLSSLBACKEND_MESALINK = 12, /* deprecated */
         CURLSSLBACKEND_BEARSSL = 13,
         CURLSSLBACKEND_RUSTLS = 14
       } curl_sslbackend;

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       int main(void)
       {
         int i;
         /* choose a specific backend */
         curl_global_sslset(CURLSSLBACKEND_WOLFSSL, NULL, NULL);

         /* list the available ones */
         const curl_ssl_backend **list;
         curl_global_sslset(CURLSSLBACKEND_NONE, NULL, &list);

         for(i = 0; list[i]; i++)
           printf("SSL backend #%d: '%s' (ID: %d)\n",
                  i, list[i]->name, list[i]->id);
       }

AVAILABILITY

       Added in curl 7.56.0

RETURN VALUE

       If this function returns CURLSSLSET_OK, the backend was successfully selected.

       If  the chosen backend is unknown (or support for the chosen backend has not been compiled
       into libcurl), the function returns CURLSSLSET_UNKNOWN_BACKEND.

       If the backend had been configured previously, or if curl_global_init(3) has already  been
       called, the function returns CURLSSLSET_TOO_LATE.

       If  this  libcurl  was built completely without SSL support, with no backends at all, this
       function returns CURLSSLSET_NO_BACKENDS.

SEE ALSO

       curl_global_init(3), libcurl(3)