| eba77359 | 09-Dec-2022 |
Kees Cook <keescook@chromium.org> |
LoadPin: Allow filesystem switch when not enforcing
For LoadPin to be used at all in a classic distro environment, it needs
to allow for switching filesystems (from the initramfs to the "real"
root
LoadPin: Allow filesystem switch when not enforcing
For LoadPin to be used at all in a classic distro environment, it needs
to allow for switching filesystems (from the initramfs to the "real"
root filesystem). To allow for this, if the "enforce" mode is not set at
boot, reset the pinned filesystem tracking when the pinned filesystem
gets unmounted instead of invalidating further loads. Once enforcement
is set, it cannot be unset, and the pinning will stick.
This means that distros can build with CONFIG_SECURITY_LOADPIN=y, but with
CONFIG_SECURITY_LOADPIN_ENFORCE disabled, but after boot is running,
the system can enable enforcement:
$ sysctl -w kernel.loadpin.enforced=1
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Link: https://lore.kernel.org/r/20221209195746.1366607-4-keescook@chromium.org
show more ...
|
| 2cfaa84e | 09-Dec-2022 |
Kees Cook <keescook@chromium.org> |
LoadPin: Move pin reporting cleanly out of locking
Refactor the pin reporting to be more cleanly outside the locking. It
was already, but moving it around helps clear the path for the root to
switch
LoadPin: Move pin reporting cleanly out of locking
Refactor the pin reporting to be more cleanly outside the locking. It
was already, but moving it around helps clear the path for the root to
switch when not enforcing.
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Link: https://lore.kernel.org/r/20221209195746.1366607-3-keescook@chromium.org
show more ...
|
| 60ba1028 | 09-Dec-2022 |
Kees Cook <keescook@chromium.org> |
LoadPin: Refactor sysctl initialization
In preparation for shifting root mount when not enforcing, split sysctl
logic out into a separate helper, and unconditionally register the
sysctl, but only ma
LoadPin: Refactor sysctl initialization
In preparation for shifting root mount when not enforcing, split sysctl
logic out into a separate helper, and unconditionally register the
sysctl, but only make it writable when the device is writable.
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Link: https://lore.kernel.org/r/20221209195746.1366607-2-keescook@chromium.org
show more ...
|
| 6e42aec7 | 06-Sep-2022 |
Matthias Kaehlcke <mka@chromium.org> |
LoadPin: Require file with verity root digests to have a header
LoadPin expects the file with trusted verity root digests to be
an ASCII file with one digest (hex value) per line. A pinned
root coul
LoadPin: Require file with verity root digests to have a header
LoadPin expects the file with trusted verity root digests to be
an ASCII file with one digest (hex value) per line. A pinned
root could contain files that meet these format requirements,
even though the hex values don't represent trusted root
digests.
Add a new requirement to the file format which consists in
the first line containing a fixed string. This prevents
attackers from feeding files with an otherwise valid format
to LoadPin.
Suggested-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220906181725.1.I3f51d1bb0014e5a5951be4ad3c5ad7c7ca1dfc32@changeid
show more ...
|
| 2039bda1 | 02-Oct-2020 |
Kees Cook <keescook@chromium.org> |
LSM: Add "contents" flag to kernel_read_file hook
As with the kernel_load_data LSM hook, add a "contents" flag to the
kernel_read_file LSM hook that indicates whether the LSM can expect
a matching c
LSM: Add "contents" flag to kernel_read_file hook
As with the kernel_load_data LSM hook, add a "contents" flag to the
kernel_read_file LSM hook that indicates whether the LSM can expect
a matching call to the kernel_post_read_file LSM hook with the full
contents of the file. With the coming addition of partial file read
support for kernel_read_file*() API, the LSM will no longer be able
to always see the entire contents of a file during the read calls.
For cases where the LSM must read examine the complete file contents,
it will need to do so on its own every time the kernel_read_file
hook is called with contents=false (or reject such cases). Adjust all
existing LSMs to retain existing behavior.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-12-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
show more ...
|
| b64fcae7 | 02-Oct-2020 |
Kees Cook <keescook@chromium.org> |
LSM: Introduce kernel_post_load_data() hook
There are a few places in the kernel where LSMs would like to have
visibility into the contents of a kernel buffer that has been loaded or
read. While sec
LSM: Introduce kernel_post_load_data() hook
There are a few places in the kernel where LSMs would like to have
visibility into the contents of a kernel buffer that has been loaded or
read. While security_kernel_post_read_file() (which includes the
buffer) exists as a pairing for security_kernel_read_file(), no such
hook exists to pair with security_kernel_load_data().
Earlier proposals for just using security_kernel_post_read_file() with a
NULL file argument were rejected (i.e. "file" should always be valid for
the security_..._file hooks, but it appears at least one case was
left in the kernel during earlier refactoring. (This will be fixed in
a subsequent patch.)
Since not all cases of security_kernel_load_data() can have a single
contiguous buffer made available to the LSM hook (e.g. kexec image
segments are separately loaded), there needs to be a way for the LSM to
reason about its expectations of the hook coverage. In order to handle
this, add a "contents" argument to the "kernel_load_data" hook that
indicates if the newly added "kernel_post_load_data" hook will be called
with the full contents once loaded. That way, LSMs requiring full contents
can choose to unilaterally reject "kernel_load_data" with contents=false
(which is effectively the existing hook coverage), but when contents=true
they can allow it and later evaluate the "kernel_post_load_data" hook
once the buffer is loaded.
With this change, LSMs can gain coverage over non-file-backed data loads
(e.g. init_module(2) and firmware userspace helper), which will happen
in subsequent patches.
Additionally prepare IMA to start processing these cases.
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-9-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
show more ...
|
| 13523bef | 24-Sep-2018 |
Kees Cook <keescook@chromium.org> |
LoadPin: Rename boot param "enabled" to "enforce"
LoadPin's "enabled" setting is really about enforcement, not whether
or not the LSM is using LSM hooks. Instead, split this out so that LSM
enabling
LoadPin: Rename boot param "enabled" to "enforce"
LoadPin's "enabled" setting is really about enforcement, not whether
or not the LSM is using LSM hooks. Instead, split this out so that LSM
enabling can be logically distinct from whether enforcement is happening
(for example, the pinning happens when the LSM is enabled, but the pin
is only checked when "enforce" is set). This allows LoadPin to continue
to operate sanely in test environments once LSM enable/disable is
centrally handled (i.e. we want LoadPin to be enabled separately from
its enforcement).
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
show more ...
|