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

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-130... Signed-off-by: Max Chernoff --- 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

-/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