CURLOPT_SSH_KEYFUNCTION(3)				     curl_easy_setopt options					CURLOPT_SSH_KEYFUNCTION(3)

NAME

       CURLOPT_SSH_KEYFUNCTION - callback for known host matching logic

SYNOPSIS

       #include <curl/curl.h>

       enum curl_khstat {
	 CURLKHSTAT_FINE_ADD_TO_FILE,
	 CURLKHSTAT_FINE,
	 CURLKHSTAT_REJECT, /* reject the connection, return an error */
	 CURLKHSTAT_DEFER,  /* do not accept it, but we can't answer right
			       now so this causes a CURLE_DEFER error but
			       otherwise the connection will be left intact
			       etc */
       };

       enum curl_khmatch {
	 CURLKHMATCH_OK,       /* match */
	 CURLKHMATCH_MISMATCH, /* host found, key mismatch! */
	 CURLKHMATCH_MISSING,  /* no matching host/key found */
       };

       struct curl_khkey {
	 const char *key; /* points to a zero-terminated string encoded with
			     base64 if len is zero, otherwise to the "raw"
			     data */
	 size_t len;
	 enum curl_khtype keytype;
       };

       int ssh_keycallback(CURL *easy,
			   const struct curl_khkey *knownkey,
			   const struct curl_khkey *foundkey,
			   enum curl_khmatch,
			   void *clientp);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_KEYFUNCTION,
				 ssh_keycallback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       It gets called when the known_host matching has been done, to allow the application to act and decide for libcurl how to proceed. The call-
       back will only be called if CURLOPT_SSH_KNOWNHOSTS(3) is also set.

       This callback function gets passed the CURL handle, the key from the known_hosts file knownkey, the key from the remote site foundkey, info
       from  libcurl  on  the  matching  status and a custom pointer (set with CURLOPT_SSH_KEYDATA(3)). It MUST return one of the following return
       codes to tell libcurl how to act:

       CURLKHSTAT_FINE_ADD_TO_FILE
	      The host+key is accepted and libcurl will append it to the known_hosts file before continuing with the connection.  This	will  also
	      add  the	host+key combo to the known_host pool kept in memory if it wasn't already present there. The adding of data to the file is
	      done by completely replacing the file with a new copy, so the permissions of the file must allow this.

       CURLKHSTAT_FINE
	      The host+key is accepted libcurl will continue with the connection. This will also add the host+key combo  to  the  known_host  pool
	      kept in memory if it wasn't already present there.

       CURLKHSTAT_REJECT
	      The host+key is rejected. libcurl will deny the connection to continue and it will be closed.

       CURLKHSTAT_DEFER
	      The  host+key is rejected, but the SSH connection is asked to be kept alive.  This feature could be used when the app wants to some-
	      how return back and act on the host+key situation and then retry without needing the overhead of setting it up from scratch again.

DEFAULT

       NULL

PROTOCOLS

       SFTP and SCP

EXAMPLE

       TODO

AVAILABILITY

       Added in 7.19.6

RETURN VALUE

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

SEE ALSO

       CURLOPT_SSH_KEYDATA(3), CURLOPT_SSH_KNOWNHOSTS(3),

libcurl 7.54.0							 February 03, 2016					CURLOPT_SSH_KEYFUNCTION(3)