NAME

curl_global_sslset - Select SSL backend to use with libcurl

SYNOPSIS

#include <curl/curl.h>
typedef struct {
  curl_sslbackend id;
  const char *name;
} curl_ssl_backend;
typedef enum {
  CURLSSLBACKEND_NONE = 0,
  CURLSSLBACKEND_OPENSSL = 1,
  CURLSSLBACKEND_GNUTLS = 2,
  CURLSSLBACKEND_NSS = 3,
  CURLSSLBACKEND_GSKIT = 5,
  CURLSSLBACKEND_POLARSSL = 6, /* deprecated */
  CURLSSLBACKEND_WOLFSSL = 7,
  CURLSSLBACKEND_SCHANNEL = 8,
  CURLSSLBACKEND_SECURETRANSPORT = 9,
  CURLSSLBACKEND_AXTLS = 10, /* deprecated */
  CURLSSLBACKEND_MBEDTLS = 11,
  CURLSSLBACKEND_MESALINK = 12,
  CURLSSLBACKEND_BEARSSL = 13
} curl_sslbackend;
CURLsslset curl_global_sslset(curl_sslbackend id,
                              const char *name,
                              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 -1 as id). If both id and name are specified, the name will be ignored.

If neither id nor name are specified, the function will fail 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 will always be 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 will result in a CURLSSLSET_TOO_LATE.

This function is not thread safe. You must not call it 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.

EXAMPLE

  /* choose a specific backend */
  curl_global_sslset(CURLSSLBACKEND_WOLFSSL, NULL, NULL);
  /* list the available ones */
  const curl_ssl_backend **list;
  curl_global_sslset((curl_sslbackend)-1, NULL, &list);
  for(i = 0; list[i]; i++)
    printf("SSL backend #%d: '%s' (ID: %d)\n",
           i, list[i]->name, list[i]->id);

AVAILABILITY

This function was added in libcurl 7.56.0. Before this version, there was no support for choosing SSL backends at runtime.

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.