On Sun, Jun 9, 2024 at 6:40 AM Jonathan Calmels jcalmels@3xx0.net wrote:
This patch allows modifying the various capabilities of the struct cred in BPF-LSM hooks. More specifically, the userns_create hook called prior to creating a new user namespace.
With the introduction of userns capabilities, this effectively provides a simple way for LSMs to control the capabilities granted to a user namespace and all its descendants.
Update the selftests accordingly by dropping CAP_SYS_ADMIN in namespaces and checking the resulting task's bounding set.
Signed-off-by: Jonathan Calmels jcalmels@3xx0.net
include/linux/lsm_hook_defs.h | 2 +- include/linux/security.h | 4 +- kernel/bpf/bpf_lsm.c | 55 +++++++++++++++++++ security/apparmor/lsm.c | 2 +- security/security.c | 6 +- security/selinux/hooks.c | 2 +- .../selftests/bpf/prog_tests/deny_namespace.c | 12 ++-- .../selftests/bpf/progs/test_deny_namespace.c | 7 ++- 8 files changed, 76 insertions(+), 14 deletions(-)
I'm not sure we want to go down the path of a LSM modifying the POSIX capabilities of a task, other than the capabilities/commoncap LSM. It sets a bad precedent and could further complicate issues around LSM ordering.
-- paul-moore.com