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curl_global_sslset(3)               libcurl              curl_global_sslset(3)

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, /* or one of its forks */
         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, /* deprecated */
         CURLSSLBACKEND_BEARSSL = 13,
         CURLSSLBACKEND_RUSTLS = 14
       } 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 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.

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.

       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)

libcurl 8.1.2                   April 26, 2023           curl_global_sslset(3)