Re: [ANNOUNCEMENT] Updated: OpenSSH-7.5p1-1

[Corinna Vinschen]

Hi Lionel,

On Mar 22 02:34, Lionel Fourquaux wrote:
> > * 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

Thanks for the report.  However, since this is an upstream issue, and
Cygwin not being the only affected system, I think it would be better to
discuss this in the upstream developer mailing list

  openssh-unix-dev AT mindrot DOT org

Shall I forward your message or would you like to report it yourself?


Thanks,
Corinna

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

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