much more finegrained bpf selinux privs for networking mainline
Goal is to gain a better handle on who has access to which maps
and to allow (with bpfloader changes to create in one directory
and move into the target directory) per-map selection of
selinux context, while still having reasonable defaults for stuff
pinned directly into the target location.
BPFFS (ie. /sys/fs/bpf) labelling is as follows:
subdirectory selinux context mainline usecase / usable by
/ fs_bpf no (*) core operating system (ie. platform)
/net_private fs_bpf_net_private yes, T+ network_stack
/net_shared fs_bpf_net_shared yes, T+ network_stack & system_server
/netd_readonly fs_bpf_netd_readonly yes, T+ network_stack & system_server & r/o to netd
/netd_shared fs_bpf_netd_shared yes, T+ network_stack & system_server & netd [**]
/tethering fs_bpf_tethering yes, S+ network_stack
/vendor fs_bpf_vendor no, T+ vendor
* initial support for bpf was added back in P,
but things worked differently back then with no bpfloader,
and instead netd doing stuff by hand,
bpfloader with pinning into /sys/fs/bpf was (I believe) added in Q
(and was definitely there in R)
** additionally bpf programs are accesible to netutils_wrapper
for use by iptables xt_bpf extensions
'mainline yes' currently means shipped by the com.android.tethering apex,
but this is really another case of bad naming, as it's really
the 'networking/connectivity/tethering' apex / mainline module.
Long term the plan is to merge a few other networking mainline modules
into it (and maybe give it a saner name...).
The reason for splitting net_private vs tethering is that:
S+ must support 4.9+ kernels and S era bpfloader v0.2+
T+ must support 4.14+ kernels and T beta3 era bpfloader v0.13+
The kernel affects the intelligence of the in-kernel bpf verifier
and the available bpf helper functions. Older kernels have
a tendency to reject programs that newer kernels allow.
/ && /vendor are not shipped via mainline, so only need to work
with the bpfloader that's part of the core os.
Bug: 218408035
Test: TreeHugger, manually on cuttlefish
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I674866ebe32aca4fc851818c1ffcbec12ac4f7d4
(cherry picked from commit 15715aea32b85c933778b97a46de6ccab42ca7fb)
diff --git a/private/network_stack.te b/private/network_stack.te
index 24d2c66..3cdf884 100644
--- a/private/network_stack.te
+++ b/private/network_stack.te
@@ -60,8 +60,8 @@
allow network_stack self:netlink_netfilter_socket create_socket_perms_no_ioctl;
allow network_stack network_stack_service:service_manager find;
# allow Tethering(network_stack process) to run/update/read the eBPF maps to offload tethering traffic by eBPF.
-allow network_stack { fs_bpf fs_bpf_tethering }:dir search;
-allow network_stack { fs_bpf fs_bpf_tethering }:file { read write };
+allow network_stack { fs_bpf_net_private fs_bpf_net_shared fs_bpf_netd_readonly fs_bpf_netd_shared fs_bpf_tethering }:dir search;
+allow network_stack { fs_bpf_net_private fs_bpf_net_shared fs_bpf_netd_readonly fs_bpf_netd_shared fs_bpf_tethering }:file { read write };
allow network_stack bpfloader:bpf { map_read map_write prog_run };
# Use XFRM (IPsec) netlink sockets
@@ -71,8 +71,46 @@
allow network_stack tun_device:chr_file rw_file_perms;
allowxperm network_stack tun_device:chr_file ioctl { TUNGETIFF TUNSETIFF TUNSETLINK TUNSETCARRIER };
-# Only the bpfloader and the network_stack should ever touch 'fs_bpf_tethering' programs/maps.
+############### NEVER ALLOW RULES
+# This place is as good as any for these rules,
+# and it is probably the most appropriate because
+# network_stack itself is entirely mainline code.
+#
# Unfortunately init/vendor_init have all sorts of extra privs
+
+# T+: Only the bpfloader and the network_stack should ever touch 'fs_bpf_net_private' programs/maps.
+neverallow { domain -bpfloader -init -network_stack -vendor_init } fs_bpf_net_private:dir ~getattr;
+neverallow { domain -bpfloader -init -network_stack -vendor_init } fs_bpf_net_private:file *;
+
+neverallow { domain -bpfloader -network_stack } fs_bpf_net_private:dir ~{ getattr open read search setattr };
+neverallow { domain -bpfloader -network_stack } fs_bpf_net_private:file ~{ map open read setattr };
+
+# T+: Only the bpfloader, network_stack and system_server should ever touch 'fs_bpf_net_shared' programs/maps.
+neverallow { domain -bpfloader -init -network_stack -system_server -vendor_init } fs_bpf_net_shared:dir ~getattr;
+neverallow { domain -bpfloader -init -network_stack -system_server -vendor_init } fs_bpf_net_shared:file *;
+
+neverallow { domain -bpfloader -network_stack -system_server } fs_bpf_net_shared:dir ~{ getattr open read search setattr };
+neverallow { domain -bpfloader -network_stack -system_server } fs_bpf_net_shared:file ~{ map open read setattr };
+
+# T+: Only the bpfloader, netd, network_stack and system_server should ever touch 'fs_bpf_netd_readonly' programs/maps.
+# netd's access should be readonly
+neverallow { domain -bpfloader -init -netd -network_stack -system_server -vendor_init } fs_bpf_netd_readonly:dir ~getattr;
+neverallow { domain -bpfloader -init -netd -network_stack -system_server -vendor_init } fs_bpf_netd_readonly:file *;
+neverallow netd fs_bpf_netd_readonly:file write;
+
+neverallow { domain -bpfloader -netd -network_stack -system_server } fs_bpf_netd_readonly:dir ~{ getattr open read search setattr };
+neverallow { domain -bpfloader -netd -network_stack -system_server } fs_bpf_netd_readonly:file ~{ map open read setattr };
+
+# T+: Only the bpfloader, netd, netutils_wrapper, network_stack and system_server should ever touch 'fs_bpf_netd_shared' programs/maps.
+# netutils_wrapper requires access to be able to run iptables and only needs readonly access
+neverallow { domain -bpfloader -init -netd -netutils_wrapper -network_stack -system_server -vendor_init } fs_bpf_netd_shared:dir ~getattr;
+neverallow { domain -bpfloader -init -netd -netutils_wrapper -network_stack -system_server -vendor_init } fs_bpf_netd_shared:file *;
+neverallow netutils_wrapper fs_bpf_netd_shared:file write;
+
+neverallow { domain -bpfloader -netd -netutils_wrapper -network_stack -system_server } fs_bpf_netd_shared:dir ~{ getattr open read search setattr };
+neverallow { domain -bpfloader -netd -netutils_wrapper -network_stack -system_server } fs_bpf_netd_shared:file ~{ map open read setattr };
+
+# S+: Only the bpfloader and the network_stack should ever touch 'fs_bpf_tethering' programs/maps.
neverallow { domain -bpfloader -init -network_stack -vendor_init } fs_bpf_tethering:dir ~getattr;
neverallow { domain -bpfloader -init -network_stack -vendor_init } fs_bpf_tethering:file *;