...now it gets ugly. If we use pasta without an existing target
namespace, and run commands directly or spawn a shell, and keep
the pasta_t domain when we do, they won't be able to do much: a
shell might even start, but it's not going to be usable, or to
even display a prompt.
Ideally, pasta should behave like a shell when it spawns a command:
start as unconfined_t and automatically transition to whatever
domain is associated in the specific policy for that command. But
we can't run as unconfined_t, of course.
It would seem natural to switch to unconfined_t "just before", so
that the default transitions happen. But transitions can only happen
when we execvp(), and that's one single transition -- not two.
That is, this approach would work for:
pasta -- sh -c 'ip address show'
but not for:
pasta -- ip address show
If we configure a transition to unconfined_t when we run ip(8), we'll
really try to start that as unconfined_t -- but unconfined_t isn't
allowed as entrypoint for ip(8) itself, and execvp() will fail.
However, there aren't many different types of binaries pasta might
commonly run -- for example, we're unlikely to see pasta used to run
a mount(8) command.
Explicitly set up domain transition for common stuff -- switching to
unconfined_t for bin_t and shells works just fine, ip(8), ping(8),
arping(8) and similar need a different treatment.
While at it, allow commands we spawn to inherit resource limits and
signal masks, because that's what happens by default, and don't
require AT_SECURE sanitisation of the environment (because that
won't happen by default). Slightly unrelated: we also need to
explicitly allow pasta_t to use TTYs, not just PTYs, otherwise
we can't keep stdin and stdout open for shells.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
contrib/selinux/pasta.te | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te
index 31e82dc..c37a847 100644
--- a/contrib/selinux/pasta.te
+++ b/contrib/selinux/pasta.te
@@ -51,6 +51,7 @@ require {
type tun_tap_device_t;
type sysctl_net_t;
class tun_socket create;
+ type user_tty_device_t;
attribute port_type;
type port_t;
@@ -77,6 +78,11 @@ require {
type kernel_t;
class process setpgid;
type shell_exec_t;
+ type ifconfig_exec_t;
+ type netutils_exec_t;
+ type ping_exec_t;
+ type ifconfig_t;
+ type ping_t;
type init_t;
class capability { sys_tty_config setuid setgid };
@@ -111,7 +117,12 @@ allow pasta_t self:user_namespace create;
auth_read_passwd_file(pasta_t)
sssd_search_lib(pasta_t)
-allow pasta_t bin_t:file { execute execute_no_trans map };
+domain_auto_trans(pasta_t, bin_t, unconfined_t);
+domain_auto_trans(pasta_t, shell_exec_t, unconfined_t);
+domain_auto_trans(pasta_t, ifconfig_exec_t, ifconfig_t);
+domain_auto_trans(pasta_t, netutils_exec_t, netutils_t);
+domain_auto_trans(pasta_t, ping_exec_t, ping_t);
+
allow pasta_t nsfs_t:file { open read };
allow pasta_t user_home_t:dir getattr;
@@ -192,3 +203,8 @@ allow pasta_t nsfs_t:file read;
allow pasta_t net_conf_t:lnk_file read;
allow pasta_t proc_net_t:lnk_file read;
+allow pasta_t unconfined_t:process { noatsecure rlimitinh siginh };
+allow pasta_t ifconfig_t:process { noatsecure rlimitinh siginh };
+allow pasta_t netutils_t:process { noatsecure rlimitinh siginh };
+allow pasta_t ping_t:process { noatsecure rlimitinh siginh };
+allow pasta_t user_tty_device_t:chr_file { append read write };
--
2.39.2