Hi Mimi,
Thank you for reviewing.
On Mon, Oct 23, 2017 at 11:54:43AM -0400, Mimi Zohar wrote:
> On Thu, 2017-10-19 at 15:51 +0100, David Howells wrote:
> > From: Chun-Yi Lee <[email protected]>
> >
> > When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image
> > through kexec_file systemcall if securelevel has been set.
>
> The patch title and description needs to be updated to refer to
> lockdown, not securelevel.
>
> As previously mentioned the last time these patches were posted, this
> leaves out testing to see if the integrity subsystem is enabled.
>
> Commit 503ceaef8e2e "ima: define a set of appraisal rules requiring
> file signatures" was upstreamed. �An additional patch could force
> these rules to be added to the custom policy, if lockdown is enabled.
> �This and other patches in this series could then check to see if
> is_ima_appraise_enabled() is true.
>
> Mimi
>
I have updated the patch title and description, and I also added
is_ima_appraise_enabled() as the following. Is it good to you?
On the other hand, I am not good on IMA. I have traced the code path
in kimage_file_prepare_segments(). Looks that the READING_KEXEC_IMAGE
doesn't show in selinux_kernel_read_file(). Where is the exact code
in IMA for checking the signature when loading crash kernel file?
Thanks a lot!
Joey Lee
---
>From 274a2125132ba5aff49e4ccd167f52982732361f Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <[email protected]>
Date: Thu, 26 Oct 2017 15:24:50 +0800
Subject: [PATCH] kexec_file: The integrity must be checked when the kernel is
locked down
When KEXEC_VERIFY_SIG and IMA appraise are not enabled, kernel should
not allow that the image to be loaded by kexec_file systemcall when the
kernel is locked down.
The original code was showed in Matthew's patch but not in the later
patch set:
https://lkml.org/lkml/2015/3/13/778
Signed-off-by: "Lee, Chun-Yi" <[email protected]>
---
kernel/kexec_file.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 9f48f44..b6dc218 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -255,6 +255,14 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
return -EPERM;
+ /* Don't permit images to be loaded into trusted kernels if we're not
+ * going to check the integrity on them
+ */
+ if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) &&
+ !is_ima_appraise_enabled() &&
+ kernel_is_locked_down("kexec of unsigned images"))
+ return -EPERM;
+
/* Make sure we have a legal set of flags */
if (flags != (flags & KEXEC_FILE_FLAGS))
return -EINVAL;
--
2.6.2
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