2019-08-31 17:27:30

by Dominick Grift

[permalink] [raw]
Subject: [RFC] ssh: remove unconfined_shell_domtrans(sshd_t)

This call allows sshd_t associated processes with run shell with an automatic domain transition to unconfined_t.
I was unable to make sense of the commit that added this:

https://github.com/SELinuxProject/refpolicy/commit/708aab13932bb8830a2d37850cc0a5c72a5d4df4

Debian's motd dynamic pam module makes sshd run a shell, we want this shell to run with sshd_t instead of unconfined_t

This patch will make the ssh_sysadm_login boolean apply to unconfined ssh logins.
To me this makes sense, as unconfined_t is targeted equivalent to the strict sysadm_t.
The boolean could however be renamed to the more generic ssh_priv_login name.

Signed-off-by: Dominick Grift <[email protected]>
---
policy/modules/services/ssh.te | 4 ----
1 file changed, 4 deletions(-)

diff --git a/policy/modules/services/ssh.te b/policy/modules/services/ssh.te
index 4e75b6e1..a99ad912 100644
--- a/policy/modules/services/ssh.te
+++ b/policy/modules/services/ssh.te
@@ -328,10 +328,6 @@ optional_policy(`
systemd_dbus_chat_logind(sshd_t)
')

-optional_policy(`
- unconfined_shell_domtrans(sshd_t)
-')
-
optional_policy(`
xserver_domtrans_xauth(sshd_t)
xserver_link_xdm_keys(sshd_t)
--
2.23.0


2019-08-31 20:55:09

by Chris PeBenito

[permalink] [raw]
Subject: Re: [RFC] ssh: remove unconfined_shell_domtrans(sshd_t)

On 8/31/19 1:27 PM, Dominick Grift wrote:
> This call allows sshd_t associated processes with run shell with an automatic domain transition to unconfined_t.
> I was unable to make sense of the commit that added this:
>
> https://github.com/SELinuxProject/refpolicy/commit/708aab13932bb8830a2d37850cc0a5c72a5d4df4
>
> Debian's motd dynamic pam module makes sshd run a shell, we want this shell to run with sshd_t instead of unconfined_t
>
> This patch will make the ssh_sysadm_login boolean apply to unconfined ssh logins.
> To me this makes sense, as unconfined_t is targeted equivalent to the strict sysadm_t.
> The boolean could however be renamed to the more generic ssh_priv_login name.
>
> Signed-off-by: Dominick Grift <[email protected]>
> ---
> policy/modules/services/ssh.te | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/policy/modules/services/ssh.te b/policy/modules/services/ssh.te
> index 4e75b6e1..a99ad912 100644
> --- a/policy/modules/services/ssh.te
> +++ b/policy/modules/services/ssh.te
> @@ -328,10 +328,6 @@ optional_policy(`
> systemd_dbus_chat_logind(sshd_t)
> ')
>
> -optional_policy(`
> - unconfined_shell_domtrans(sshd_t)
> -')
> -
> optional_policy(`
> xserver_domtrans_xauth(sshd_t)
> xserver_link_xdm_keys(sshd_t)

I don't have any objections to this.

--
Chris PeBenito

2019-09-01 11:20:29

by Nicolas Iooss

[permalink] [raw]
Subject: Re: [RFC] ssh: remove unconfined_shell_domtrans(sshd_t)

On Sat, Aug 31, 2019 at 10:54 PM Chris PeBenito <[email protected]> wrote:
>
> On 8/31/19 1:27 PM, Dominick Grift wrote:
> > This call allows sshd_t associated processes with run shell with an automatic domain transition to unconfined_t.
> > I was unable to make sense of the commit that added this:
> >
> > https://github.com/SELinuxProject/refpolicy/commit/708aab13932bb8830a2d37850cc0a5c72a5d4df4
> >
> > Debian's motd dynamic pam module makes sshd run a shell, we want this shell to run with sshd_t instead of unconfined_t
> >
> > This patch will make the ssh_sysadm_login boolean apply to unconfined ssh logins.
> > To me this makes sense, as unconfined_t is targeted equivalent to the strict sysadm_t.
> > The boolean could however be renamed to the more generic ssh_priv_login name.
> >
> > Signed-off-by: Dominick Grift <[email protected]>
> > ---
> > policy/modules/services/ssh.te | 4 ----
> > 1 file changed, 4 deletions(-)
> >
> > diff --git a/policy/modules/services/ssh.te b/policy/modules/services/ssh.te
> > index 4e75b6e1..a99ad912 100644
> > --- a/policy/modules/services/ssh.te
> > +++ b/policy/modules/services/ssh.te
> > @@ -328,10 +328,6 @@ optional_policy(`
> > systemd_dbus_chat_logind(sshd_t)
> > ')
> >
> > -optional_policy(`
> > - unconfined_shell_domtrans(sshd_t)
> > -')
> > -
> > optional_policy(`
> > xserver_domtrans_xauth(sshd_t)
> > xserver_link_xdm_keys(sshd_t)
>
> I don't have any objections to this.

Would it be possible to extend this patch to other callers of
unconfined_shell_domtrans, like the patch below? It will help fix
issues with Debian's PAM module that generates the MOTD (Message Of
The Day) in a dynamic way, using shell commands (cf.
https://wiki.debian.org/motd for more information: calling system()
triggers a transition to system_u:system_r:unconfined_t because of
unconfined_shell_domtrans).

diff --git a/policy/modules/services/remotelogin.te
b/policy/modules/services/remotelogin.te
index bc2292e37892..c7c9c5646785 100644
--- a/policy/modules/services/remotelogin.te
+++ b/policy/modules/services/remotelogin.te
@@ -91,10 +91,6 @@ optional_policy(`
telnet_use_ptys(remote_login_t)
')

-optional_policy(`
- unconfined_shell_domtrans(remote_login_t)
-')
-
optional_policy(`
usermanage_read_crack_db(remote_login_t)
')
diff --git a/policy/modules/services/rshd.te b/policy/modules/services/rshd.te
index 0f4caffc4f33..196ed2848e4b 100644
--- a/policy/modules/services/rshd.te
+++ b/policy/modules/services/rshd.te
@@ -74,6 +74,5 @@ optional_policy(`
')

optional_policy(`
- unconfined_shell_domtrans(rshd_t)
unconfined_signal(rshd_t)
')
diff --git a/policy/modules/system/locallogin.te
b/policy/modules/system/locallogin.te
index a56f3d1fbe16..632d2542972d 100644
--- a/policy/modules/system/locallogin.te
+++ b/policy/modules/system/locallogin.te
@@ -200,10 +200,6 @@ optional_policy(`
systemd_write_inherited_logind_sessions_pipes(local_login_t)
')

-optional_policy(`
- unconfined_shell_domtrans(local_login_t)
-')
-
optional_policy(`
usermanage_read_crack_db(local_login_t)
')

2019-09-01 11:38:08

by Dominick Grift

[permalink] [raw]
Subject: Re: [RFC] ssh: remove unconfined_shell_domtrans(sshd_t)

On Sun, Sep 01, 2019 at 01:19:56PM +0200, Nicolas Iooss wrote:
> On Sat, Aug 31, 2019 at 10:54 PM Chris PeBenito <[email protected]> wrote:
> >
> > On 8/31/19 1:27 PM, Dominick Grift wrote:
> > > This call allows sshd_t associated processes with run shell with an automatic domain transition to unconfined_t.
> > > I was unable to make sense of the commit that added this:
> > >
> > > https://github.com/SELinuxProject/refpolicy/commit/708aab13932bb8830a2d37850cc0a5c72a5d4df4
> > >
> > > Debian's motd dynamic pam module makes sshd run a shell, we want this shell to run with sshd_t instead of unconfined_t
> > >
> > > This patch will make the ssh_sysadm_login boolean apply to unconfined ssh logins.
> > > To me this makes sense, as unconfined_t is targeted equivalent to the strict sysadm_t.
> > > The boolean could however be renamed to the more generic ssh_priv_login name.
> > >
> > > Signed-off-by: Dominick Grift <[email protected]>
> > > ---
> > > policy/modules/services/ssh.te | 4 ----
> > > 1 file changed, 4 deletions(-)
> > >
> > > diff --git a/policy/modules/services/ssh.te b/policy/modules/services/ssh.te
> > > index 4e75b6e1..a99ad912 100644
> > > --- a/policy/modules/services/ssh.te
> > > +++ b/policy/modules/services/ssh.te
> > > @@ -328,10 +328,6 @@ optional_policy(`
> > > systemd_dbus_chat_logind(sshd_t)
> > > ')
> > >
> > > -optional_policy(`
> > > - unconfined_shell_domtrans(sshd_t)
> > > -')
> > > -
> > > optional_policy(`
> > > xserver_domtrans_xauth(sshd_t)
> > > xserver_link_xdm_keys(sshd_t)
> >
> > I don't have any objections to this.
>
> Would it be possible to extend this patch to other callers of
> unconfined_shell_domtrans, like the patch below? It will help fix
> issues with Debian's PAM module that generates the MOTD (Message Of
> The Day) in a dynamic way, using shell commands (cf.
> https://wiki.debian.org/motd for more information: calling system()
> triggers a transition to system_u:system_r:unconfined_t because of
> unconfined_shell_domtrans).

Not sure about remotelogin and rshd (are people still using this?), but I do believe one should be able to remove it from local_login_t.

>
> diff --git a/policy/modules/services/remotelogin.te
> b/policy/modules/services/remotelogin.te
> index bc2292e37892..c7c9c5646785 100644
> --- a/policy/modules/services/remotelogin.te
> +++ b/policy/modules/services/remotelogin.te
> @@ -91,10 +91,6 @@ optional_policy(`
> telnet_use_ptys(remote_login_t)
> ')
>
> -optional_policy(`
> - unconfined_shell_domtrans(remote_login_t)
> -')
> -
> optional_policy(`
> usermanage_read_crack_db(remote_login_t)
> ')
> diff --git a/policy/modules/services/rshd.te b/policy/modules/services/rshd.te
> index 0f4caffc4f33..196ed2848e4b 100644
> --- a/policy/modules/services/rshd.te
> +++ b/policy/modules/services/rshd.te
> @@ -74,6 +74,5 @@ optional_policy(`
> ')
>
> optional_policy(`
> - unconfined_shell_domtrans(rshd_t)
> unconfined_signal(rshd_t)
> ')
> diff --git a/policy/modules/system/locallogin.te
> b/policy/modules/system/locallogin.te
> index a56f3d1fbe16..632d2542972d 100644
> --- a/policy/modules/system/locallogin.te
> +++ b/policy/modules/system/locallogin.te
> @@ -200,10 +200,6 @@ optional_policy(`
> systemd_write_inherited_logind_sessions_pipes(local_login_t)
> ')
>
> -optional_policy(`
> - unconfined_shell_domtrans(local_login_t)
> -')
> -
> optional_policy(`
> usermanage_read_crack_db(local_login_t)
> ')
>

--
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Dominick Grift


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