Announce: OpenSSH 7.5 released

Corinna Vinschen
2017-03-24T12:00:06Z

Hi,

I got a report on the Cygwin mailing list in terms of deprecating the
privsep option.  It seems one consequence is that you can't run sshd
under a non-privileged account for personal use anymore:

----- Forwarded message from Lionel Fourquaux -----
> * This release deprecates the sshd_config UsePrivilegeSeparation
>   option, thereby making privilege separation mandatory.

This has (probably not wholly intended) consequences when running sshd in
single user (non root) mode:

$ /usr/sbin/sshd -D -f ~/.ssh/sshd_config
Privilege separation user sshd does not exist

The problem is not limited to Cygwin, but is unlikely to happen in a typical
Unix, since ssh is probably installed globally.

If Cygwin was installed without administrative privileges, creating a
dedicated sshd user would be impossible (and makes little sense if sshd runs
in single user mode, anyway).  I guess it would be possible to add a fake
user account in /etc/passwd.

Since user sshd and chroot /var/empty are not used in single user mode, it
might be better to remove the check in this case:

=== cut after ==diff --git a/sshd.c b/sshd.c
index 010a2c3..4f9b2c8 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1641,7 +1641,8 @@ main(int ac, char **av)

	/* Store privilege separation user for later use if required. */
	if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
-		if (use_privsep || options.kerberos_authentication)
+		if ((use_privsep || options.kerberos_authentication)
+		    && (getuid() == 0 || geteuid() == 0))
			fatal("Privilege separation user %s does not exist",
			    SSH_PRIVSEP_USER);
	} else {
@@ -1767,7 +1768,7 @@ main(int ac, char **av)
		    key_type(key));
	}

-	if (use_privsep) {
+	if (use_privsep && (getuid() == 0 || geteuid() == 0)) {
		struct stat st;

		if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
=== cut before ==
Best regards,

		-- Lionel
----- End forwarded message -----

Is there a chance this could be reenabled again?


Thanks,
Corinna

--
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat
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