Re: [PATCH v2 1/1] selinux: Transition to pasta_t in containers

[Paul Holzinger <pholzing@redhat.com>]

Hi, podman maintainer here.

On 16/05/2025 07:11, Max Chernoff wrote:
> Currently, pasta runs in the container_runtime_exec_t context when
> running in a container. This is not ideal since it means that pasta runs
> with more privileges than strictly necessary. This commit updates the
> SELinux policy to have pasta transition to the pasta_t context when
> started from the container_runtime_t context, adds the appropriate
> labels to $XDG_RUNTIME_DIR/netns and
> $XDG_RUNTIME_DIR/containers/networks/rootless-netns, and grants the
> necessary permissions to the pasta_t context.
>
> Link: https://bugs.passt.top/show_bug.cgi?id=81
> Link: https://github.com/containers/podman/discussions/26100#discussioncomment-13088518
> Signed-off-by: Max Chernoff <git@maxchernoff.ca>
> ---
>   contrib/selinux/pasta.fc | 10 ++++++----
>   contrib/selinux/pasta.te | 37 ++++++++++++++++++++++++++++++++++++-
>   2 files changed, 42 insertions(+), 5 deletions(-)

So I did test this patch with podman's system and e2e test on podman 
v5.5.0 on fedora rawhide and I noticed one problem that caused some 
failures:

podman build is broken with this policy. And I assume that means buildah 
would not work as well. The difference is that in the build case we do 
not pass a bind mounted namespace path under /run but rather 
/proc/$pid/ns/net as path to pasta. We get this error:

pasta failed with exit code 1:
Couldn't open network namespace /proc/360143/ns/net: Permission denied

Logged avc:
denied  { search } for  pid=360144 comm="pasta.avx2" name="360143" 
dev="proc" ino=2030208 
scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 
tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 
tclass=dir permissive=0

The good news is that this the only problem I found.

>
> diff --git a/contrib/selinux/pasta.fc b/contrib/selinux/pasta.fc
> index 41ee46d..e4aefc4 100644
> --- a/contrib/selinux/pasta.fc
> +++ b/contrib/selinux/pasta.fc
> @@ -8,7 +8,9 @@
>   # Copyright (c) 2022 Red Hat GmbH
>   # Author: Stefano Brivio <sbrivio@redhat.com>
>   
> -/usr/bin/pasta			system_u:object_r:pasta_exec_t:s0
> -/usr/bin/pasta.avx2		system_u:object_r:pasta_exec_t:s0
> -/tmp/pasta\.pcap		system_u:object_r:pasta_log_t:s0
> -/var/run/pasta\.pid		system_u:object_r:pasta_pid_t:s0
> +/usr/bin/pasta						system_u:object_r:pasta_exec_t:s0
> +/usr/bin/pasta.avx2					system_u:object_r:pasta_exec_t:s0
> +/tmp/pasta\.pcap					system_u:object_r:pasta_log_t:s0
> +/var/run/pasta\.pid					system_u:object_r:pasta_pid_t:s0
> +/run/user/%{USERID}/netns				system_u:object_r:ifconfig_var_run_t:s0
> +/run/user/%{USERID}/containers/networks/rootless-netns	system_u:object_r:ifconfig_var_run_t:s0
> diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te
> index 89c8043..7bcb451 100644
> --- a/contrib/selinux/pasta.te
> +++ b/contrib/selinux/pasta.te
> @@ -89,6 +89,13 @@ require {
>   	class capability { sys_tty_config setuid setgid };
>   	class cap_userns { setpcap sys_admin sys_ptrace net_bind_service net_admin };
>   	class user_namespace create;
> +
> +	# Container requires
> +	attribute_role usernetctl_roles;
> +	role container_user_r;
> +	role staff_r;
> +	role user_r;
> +	type container_runtime_t;
>   }
>   
>   type pasta_t;
> @@ -113,6 +120,9 @@ init_daemon_domain(pasta_t, pasta_exec_t)
>   
>   allow pasta_t self:capability { setpcap net_bind_service sys_tty_config dac_read_search net_admin sys_resource setuid setgid };
>   allow pasta_t self:cap_userns { setpcap sys_admin sys_ptrace net_admin net_bind_service };
> +# pasta only calls setuid and setgid with the current UID and GID, so this
> +# denial is harmless. See https://bugzilla.redhat.com/show_bug.cgi?id=2330512#c10
> +dontaudit pasta_t self:cap_userns { setgid setuid };
>   allow pasta_t self:user_namespace create;
>   
>   auth_read_passwd(pasta_t)
> @@ -130,7 +140,7 @@ allow pasta_t user_home_t:file { open read getattr setattr execute execute_no_tr
>   allow pasta_t user_home_dir_t:dir { search getattr open add_name read write };
>   allow pasta_t user_home_dir_t:file { create open read write };
>   allow pasta_t tmp_t:dir { add_name mounton remove_name write };
> -allow pasta_t tmpfs_t:filesystem mount;
> +allow pasta_t tmpfs_t:filesystem { getattr mount };
>   allow pasta_t fs_t:filesystem unmount;
>   allow pasta_t root_t:dir mounton;
>   manage_files_pattern(pasta_t, pasta_pid_t, pasta_pid_t)
> @@ -156,6 +166,7 @@ allow pasta_t tmp_t:sock_file { create unlink write };
>   allow pasta_t self:tcp_socket create_stream_socket_perms;
>   corenet_tcp_sendrecv_generic_node(pasta_t)
>   corenet_tcp_bind_generic_node(pasta_t)
> +allow pasta_t container_runtime_t:fifo_file { getattr write };
>   allow pasta_t pasta_port_t:tcp_socket { name_bind name_connect };
>   allow pasta_t pasta_port_t:udp_socket { name_bind };
>   allow pasta_t http_port_t:tcp_socket { name_bind name_connect };
> @@ -213,3 +224,27 @@ 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 };
>   allow pasta_t user_devpts_t:chr_file { append read write };
> +
> +# Allow network administration commands for non-privileged users
> +roleattribute container_user_r usernetctl_roles;
> +roleattribute staff_r usernetctl_roles;
> +roleattribute user_r usernetctl_roles;
> +role usernetctl_roles types pasta_t;
> +
> +# Make pasta in a container run under the pasta_t context
> +type_transition container_runtime_t pasta_exec_t : process pasta_t;
> +allow container_runtime_t pasta_t:process transition;
> +
> +# Label the user network namespace files
> +type_transition container_runtime_t user_tmp_t : dir ifconfig_var_run_t "netns";
> +type_transition container_runtime_t user_tmp_t : dir ifconfig_var_run_t "rootless-netns";
> +allow pasta_t ifconfig_var_run_t:dir { add_name open rmdir write };
> +allow pasta_t ifconfig_var_run_t:file { create open write };
> +
> +# Allow pasta to bind to any port
> +bool pasta_bind_all_ports true;
> +if (pasta_bind_all_ports) {
I am not familiar with the selinux stuff but if this is a boolean that 
users can configure should this be documented in the man page here?
> +	allow pasta_t port_type:icmp_socket { accept getopt name_bind };
> +	allow pasta_t port_type:tcp_socket { accept getopt name_bind name_connect };
> +	allow pasta_t port_type:udp_socket { accept getopt name_bind };
> +}

-- 
Paul Holzinger