This patchset ensure that IMA's modules checking policy:
measure func=MODULE_CHECK uid=0
rely on the correct value of CONFIG_MODULE_SIG_FORCE, since the way it
is today the code completely ignores the module.sig_enforce cmdline
param, which behaves in a OR logic with the CONFIG value
(CONFIG_MODULE_SIG_FORCE || module.sig_enforce). That said, everytime a
module would load, in the current checking code, when the kernel was not
compiled with the CONFIG set the call to init_module syscall fails with
-EACCES:
# strace -f -v modprobe <any-module> | grep init_module
init_module(0x55b9bcc9bba0, 17763, "") = -1 EACCES (Permission denied)
With this patchset the result would rely on the module.sig_enforce
cmdline as well. Once the CONFIG is not set, but the param is, the
result would be 'success', as it should be:
# strace -f -v modprobe <any-module> | grep init_module
init_module(0x7f9602d6e010, 386646, "") = 0
The patchset was tested in two different kernels: 4.13.6 (Fedora 27) and
4.14.0-rc4 (integrity-next tree)
Bruno E. O. Meneguele (2):
module: export module signature enforcement status
ima: check signature enforcement against cmdline param instead of
CONFIG
include/linux/module.h | 2 ++
kernel/module.c | 8 ++++++++
security/integrity/ima/ima_main.c | 6 +++---
3 files changed, 13 insertions(+), 3 deletions(-)
--
2.13.6
