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authorStefano Brivio <sbrivio@redhat.com>2023-08-16 07:20:30 +0200
committerStefano Brivio <sbrivio@redhat.com>2023-08-18 18:47:53 +0200
commit0af928eaa020c1062fdc91598dfdc533966e2afe (patch)
tree1025f3c7ce20c0ce2e10dccfbe875cec2a08afec
parent30817fdd4e98e762973a390e293130e4bd7f2396 (diff)
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selinux: Fix domain transitions for typical commands pasta might run2023_08_18.0af928e
...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@redhat.com>
-rw-r--r--contrib/selinux/pasta.te19
1 files changed, 18 insertions, 1 deletions
diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te
index ce9186f..ed70c5f 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 +78,12 @@ 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 netutils_t;
+ type ping_t;
type init_t;
class capability { sys_tty_config setuid setgid };
@@ -111,7 +118,12 @@ allow pasta_t self:user_namespace create;
allow pasta_t passwd_file_t:file read_file_perms;
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 +204,8 @@ 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 };