On Fri, 15 Mar 2019 14:42:47, Corinna Vinschen wrote: > On Mar 15 14:06, Houder wrote:
> > One is forced to create the exact same environment (system) as the > > person who is complaining, fire up the debugger (like sticking > > a thermometer in a patient's rear end) in order to find out where > > the code failed ... > > > > Meaning, within the context of the recent sshd problems, possibly only ^^^^ > > you know where the error ERROR_FILE_INVALID (resulting in the error ^^^ strace, yes. But only if one has the exact same "network" at one's disposal as the one where the problem occurred (like you have at your place; while I only have one simple computer) ... That is decisive. > > message "No such device or address") was generated ... (and by which > > Windows function). > > The only interface an application has is by checking the POSIX > errno value. This is what Cygwin is about :) > > If you need more details what's going on under the hood, you have > to use strace. > > > Oh well, this cannot be helped ... > > Well, there *is* a solution by using strace. And hey, we now know what > ENXIO returned from seteuid means, don't we? It's not all bad :) You do! I do not :-) (as I do not have the machinery at my disposal that is required to provoke this error). A simple STC to emphasize my statement (i.e. a problem that I can strace on my computer). int main() { errno = 0; if (seteuid( (uid_t)1004) != 0) { // 1004, not being me :-) printf("seteuid: errno = %d, errstr = %s\n", errno, strerror(errno) ); // seteuid: errno = 13, errstr = Permission denied => EACCES // ... while only EPERM en EINVAL are documented ... } else printf("1004, OK\n"); } 64-@@ ./seteuid seteuid: errno = 13, errstr = Permission denied ... huh? On Linux this simple "Simple Test Case" will result in: seteuid: errno = 1, errstr = Operation not permitted ... Got it! Fortunately, I have now have the strace output at my disposal: ... studying the strace output and the source code, I am now able to tell what is going on ... see below: seteuid (syscalls.cc) .lsaprivkeyauth (sec_auth.cc) <==== fails; as result NULL (token) is returned by lsaprivkeyauth ... ...lsa_open_policy (sec_auth.cc) <==== fails; as result NULL (lsa) is returned by lsa_open_policy ... # errno, set by lsa_open_policy, is ignored # seteuid() chooses NOT to bail out, but # to attempt "Service For User Logon" (s4u) ... .s4uauth (sec_auth.cc) <==== fails (because LsaRegisterLogonProcess fails), returning the status (0xC0000041) to seteuid() # /usr/include/w32api/ntstatus.h: # defines STATUS_PORT_CONNECTION_REFUSED ((NTSTATUS)0xC0000041) # now seteuid chooses to bail out (i.e. setuid() fails) Q: errno? s4uauth calls __seterrno_from_nt_status (0xC0000041), which in turn calls RtlNtStatusToDosError(0xC0000041), which in turn calls geterrno_from_win_error(5,...): 0xC0000041 is mapped to 5, which in turn is mapped to 13 (EACCES). Henri -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple