cygwin_logon_user(const struct passwd *passwd_entry, const char *password
Given a pointer to a passwd entry of a user and a cleartext password,
returns a HANDLE to an impersonation token for this user which can be used
in a subsequent call to
to impersonate that user. This function can only be called from a process
which has the required NT user rights to perform a logon.
See also the chapter Switching the user context in the Cygwin User's guide.
See also cygwin_set_impersonation_token