Re: Group Permissions on root folders problem (Windows 10 TP build 10061)

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

Hi Takashi,

On Sep 11 19:04, Takashi Yano wrote:
> Hi Corinna,
> 
> Regarding the first problem:
> > > a) Group permissions on root folders
> 
> On Sun, 6 Sep 2015 13:44:44 +0200
> Corinna Vinschen wrote:
> > The group permission problem is easy (and I'm wondering if it really was
> > such a bright idea to let user SID == group SID slip through in Cygwin,
> > rather tnan  sticking to the former idea to change the group SID to
> > "Users" in this case).  csih needs a patch to not check for the group
> > x bit if user SID == group SID.
> 
> Do you intend a patch like this? I have confirmed that sshd
> is successfully installed and works nicely with this patch
> under a Microsoft Account.
> 
> --- cygwin-service-installation-helper.sh.orig	2015-02-24 04:57:56.000000000 +0900
> +++ cygwin-service-installation-helper.sh	2015-09-11 18:41:56.870882800 +0900
> @@ -2442,6 +2442,8 @@
>  # ======================================================================
>  _csih_setup()
>  {
> +  local perms="d..x..x..[xt]"
> +
>    csih_stacktrace "${@}"
>    $_csih_trace
>    if [ "$_csih_setup_already_called" -eq 0 ]
> @@ -2462,7 +2464,13 @@
>        csih_error "Problem with LocalSystem or Adminstrator IDs"
>      fi
>  
> -    if ! csih_check_dir_perms "${LOCALSTATEDIR}" "d..x..x..[xt]"
> +    if [ `/usr/bin/stat -c '%g' ${LOCALSTATEDIR}` -eq \
> +	 `/usr/bin/stat -c '%u' ${LOCALSTATEDIR}` ]
> +    then
> +      perms="d..x.....[xt]"
> +    fi
> +
> +    if ! csih_check_dir_perms "${LOCALSTATEDIR}" "${perms}"
>      then
>        csih_error "Problem with ${LOCALSTATEDIR} directory. Exiting."
>      fi

In theory, yes.  The problem is just that checking the uid/gid equality
is not safe, given that you can easily create that via passwd/group
files.  What I was thinking of is to convert the uid/gid values into
SIDs using the `getent' tool and to compare those, along the lines of

  uid=$(/usr/bin/stat -c '%u')
  user_sid=$(getent passwd -w $uid | awk -F: '{print $4}')
  gid=$(/usr/bin/stat -c '%g')
  grp_sid=$(getent group -w $gid | awk -F: '{print $4}')
  if [ "${user_sid}" = "${grp_sid}" ]
    ...

Can you check if that works in your env and perhaps create a new patch
using the SIDs?


Thanks a lot,
Corinna

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

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