On Aug 7 22:11, Shaddy Baddah via Cygwin wrote: > Hi, > > For the current OpenSSH server (9.3p2), AllowStreamLocalForwarding > defaults on. That means both local and remote unix socket port > portforwarding are possible. > > For Cygwin, it appears the remote form of this is not possible. The > following message is seen on the client-side, regardless of whether > sshd_config explicitly defines AllowStreamLocalForwarding "on", or > "all": > > |Forwarding port. > |debug1: Remote: Server has disabled streamlocal forwarding. > > Finding the code around this, and a three(?) component conditional > expression that "fails" into that message, I discovered that the > reason it is not allowed is the following conditional: > > | (pw->pw_uid != 0 && !use_privsep)) { > > and to my surprise, after compiling a debug version of sshd to discover > this conditional, it turns out that use_privsep is set to zero (0). > > I've been around the Cygwin community for many years, and I remember > the time when ssh-host-config prompted for priv sep, and the creation > of the "sshd" local user. > > I remember the transition when that prompt was removed, and reading that > priv sep was now "on permanently". > > I think there is a misunderstanding here though, though I'm not 100% > sure of my reading of the situation. It appears that though priv sep is > on by default, for Cygwin, it is effectively off, as it cannot be > implemented???
Privilege separation in OpenSSH consists of two independent parts, both of which require AF_UNIX sockets. The first part is transmission of peer credentials per the SO_PEERCRED socket option. This was relatively easy to implement. The other part of privilege separation requires AF_UNIX sockets to allow sending and receiving open file descriptors via the SCM_RIGHTS ancillary data feature. This does not work in Cygwin. > DISABLE_FD_PASS is always set by autoconf for Cygwin. And my reading is > that not having that capability effectively means whatever the other > criteria, the executing process doesn't have sufficient "separation" of > privilege to be treated in the same manner. Yes, the parts of OpenSSH requiring descriptor passing are disabled in OpenSSH. > Otherwise, what's the solution? Solution for what? What is it you want to do? Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple