On 9/14/23 07:27, Alessandro Carminati (Red Hat) wrote:
This patch sets up a new feature to the Linux kernel to have the ability,
while module signature checking is enabled, to delay the moment where
these signatures are effectively checked. The feature is structure into
two main key points, the feature can be enabled by a new command line
kernel argument, while in delay mode, the kernel waits until the
userspace communicates to start checking signature modules.
This operation can be done by writing a value in a securityfs file,
which works the same as /sys/kernel/security/lockdown.
Patch 1/2: Modules: Introduce boot-time module signature flexibility
The first patch in this set fundamentally alters the kernel's behavior
at boot time by implementing a delayed module signature verification
mechanism. It introduces a new boot-time kernel argument that allows
users to request this delay. By doing so, we aim to capitalize on the
cryptographic checks already performed on the kernel and initrd images
during the secure boot process. As a result, we can significantly
improve the boot speed without compromising system security.
Patch 2/2: docs: Update kernel-parameters.txt for signature verification
enhancement
The second patch is just to update the kernel parameters list
documentation.
Background and Motivation
In certain contexts, boot speed becomes crucial. This patch follows the
recognition that security checks can at times be redundant. Therefore,
it proves valuable to skip those checks that have already been validated.
In a typical Secure Boot startup with an initrd, the bootloader is
responsible for verifying artifacts before relinquishing control. In a
verified initrd image, it is reasonable to assume that its content is
also secure. Consequently, verifying module signatures may be deemed
unnecessary.
This patch introduces a feature to skip signature verification during
the initrd boot phase.
I think this is fine to do. There is some risk for users who may use
this without realizing what they're actually doing and then would end up
creating a security hole. But there are far worse ways you can do that
with access to kernel paramaters.
P.
Alessandro Carminati (Red Hat) (2):
Modules: Introduce boot-time module signature flexibility
docs: Update kernel-parameters.txt for signature verification
enhancement
.../admin-guide/kernel-parameters.txt | 9 +++
include/linux/module.h | 4 ++
kernel/module/main.c | 14 +++--
kernel/module/signing.c | 56 +++++++++++++++++++
4 files changed, 77 insertions(+), 6 deletions(-)
