libssh2_userauth_publickey

#include <libssh2.h>
int
libssh2_userauth_publickey(LIBSSH2_SESSION *session,
                           const char *user,
                           const unsigned char *pubkeydata,
                           size_t pubkeydata_len,
                           sign_callback,
                           void **abstract);

Authenticate with the sign_callback callback that matches the prototype below

int name(LIBSSH2_SESSION *session, unsigned char **sig, size_t *sig_len,
         const unsigned char *data, size_t data_len, void **abstract);

This function gets called...

Return 0 on success or negative on failure.

libssh2_userauth_publickey_fromfile_ex(3)