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CURLOPT_SSH_HOSTKEYFUNCTION(3)                        Library Functions Manual


NAME

       CURLOPT_SSH_HOSTKEYFUNCTION - callback to check host key


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 host key 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 host key is accepted, the connection should continue.

       CURLKHMATCH_MISMATCH
              the host key is rejected, the connection is canceled.


DEFAULT

       NULL


PROTOCOLS

       This functionality affects scp and sftp


EXAMPLE

       struct mine {
         void *custom;
       };

       int hostkeycb(void *clientp,    /* passed with CURLOPT_SSH_HOSTKEYDATA */
                     int keytype,      /* CURLKHTYPE */
                     const char *key,  /* host key 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;
       }
       int main(void)
       {
         struct mine callback_data;
         CURL *curl = curl_easy_init();
         if(curl) {
           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);
         }
       }


NOTES

       Work only with the libssh2 backend.


AVAILABILITY

       Added in curl 7.84.0


RETURN VALUE

       curl_easy_setopt(3) returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK, non-zero means an error occurred,
       see libcurl-errors(3).


SEE ALSO

       CURLOPT_SSH_HOSTKEYDATA(3), CURLOPT_SSH_KNOWNHOSTS(3)

libcurl                           2025-02-08    CURLOPT_SSH_HOSTKEYFUNCTION(3)

curl 8.12.0 - Generated Tue Feb 18 18:50:04 CST 2025
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