NAME

       CURLOPT_SSH_HOSTKEYFUNCTION - callback to check hostkey

SYNOPSIS

       #include <curl/curl.h>

       int keycallback(void *clientp,
                       int keytype,
                       const char *key,
                       size_t keylen);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_HOSTKEYFUNCTION,
                                 keycallback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above. It
       overrides CURLOPT_SSH_KNOWNHOSTS(3).

       This callback gets called when the verification of the SSH hostkey is needed.

       key is keylen bytes long and is the key to check. keytype says what type it is,  from  the
       CURLKHTYPE_* series in the curl_khtype enum.

       clientp is a custom pointer set with CURLOPT_SSH_HOSTKEYDATA(3).

       The callback MUST return one of the following return codes to tell libcurl how to act:

       CURLKHMATCH_OK
              The hostkey is accepted, the connection should continue.

       CURLKHMATCH_MISMATCH
              the hostkey is rejected, the connection is canceled.

DEFAULT

       NULL

PROTOCOLS

       SCP and SFTP

EXAMPLE

       int hostkeycb(void *clientp,    /* passed with CURLOPT_SSH_HOSTKEYDATA */
                     int keytype,      /* CURLKHTYPE */
                     const char * key, /*hostkey to check*/
                     size_t keylen);   /*length of the key*/
       {
         /* 'clientp' points to the callback_data struct */
         /* investigate the situation and return the correct value */
         return CURLKHMATCH_OK;
       }
       {
         curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/thisfile.txt");
         curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYFUNCTION, hostkeycb);
         curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYDATA, &callback_data);

         curl_easy_perform(curl);
       }

AVAILABILITY

       Added in 7.84.0 , work only with libssh2 backend.

RETURN VALUE

       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

SEE ALSO

       CURLOPT_SSH_HOSTKEYDATA(3), CURLOPT_SSH_KNOWNHOSTS(3),