A kernel builder may not enable KEXEC_SIG and some architectures like
ppc64 simply don't have KEXEC_SIG. In these cases, unless both
IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
unsigned kernel image from being kexec'ed via the kexec_file_load
syscall whereas it could prevent one via the kexec_load syscall. Mandate
signature verification for those cases.
Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
Cc: Matthew Garrett <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: David Howells <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Coiby Xu <[email protected]>
---
kernel/kexec_file.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 45637511e0de..04d56b6e6459 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -125,6 +125,20 @@ void kimage_file_post_load_cleanup(struct kimage *image)
image->image_loader_data = NULL;
}
+static int mandate_signatute_verification(void)
+{
+ /*
+ * If IMA is guaranteed to appraise a signature on the kexec
+ * image, permit it even if the kernel is otherwise locked
+ * down.
+ */
+ if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
+ security_locked_down(LOCKDOWN_KEXEC))
+ return -EPERM;
+
+ return 0;
+}
+
#ifdef CONFIG_KEXEC_SIG
#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
@@ -168,14 +182,9 @@ kimage_validate_signature(struct kimage *image)
return ret;
}
- /*
- * If IMA is guaranteed to appraise a signature on the kexec
- * image, permit it even if the kernel is otherwise locked
- * down.
- */
- if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
- security_locked_down(LOCKDOWN_KEXEC))
- return -EPERM;
+ ret = mandate_signatute_verification();
+ if (ret)
+ return ret;
pr_debug("kernel signature verification failed (%d).\n", ret);
}
@@ -211,10 +220,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
#ifdef CONFIG_KEXEC_SIG
ret = kimage_validate_signature(image);
-
+#else
+ ret = mandate_signatute_verification();
+#endif
if (ret)
goto out;
-#endif
+
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
--
2.38.1
Hi Coiby,
On Mon, 2022-11-21 at 15:29 +0800, Coiby Xu wrote:
> A kernel builder may not enable KEXEC_SIG and some architectures like
> ppc64 simply don't have KEXEC_SIG. In these cases, unless both
> IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
> unsigned kernel image from being kexec'ed via the kexec_file_load
> syscall whereas it could prevent one via the kexec_load syscall. Mandate
> signature verification for those cases.
>
> Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
> Cc: Matthew Garrett <[email protected]>
> Cc: Jiri Bohac <[email protected]>
> Cc: David Howells <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Coiby Xu <[email protected]>
Other than correcting the function name to mandate_signature_verificati
on(),
Reviewed-by: Mimi Zohar <[email protected]>
Hi Mimi,
On Mon, Nov 21, 2022 at 01:23:57PM -0500, Mimi Zohar wrote:
>Hi Coiby,
>
>On Mon, 2022-11-21 at 15:29 +0800, Coiby Xu wrote:
>> A kernel builder may not enable KEXEC_SIG and some architectures like
>> ppc64 simply don't have KEXEC_SIG. In these cases, unless both
>> IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
>> unsigned kernel image from being kexec'ed via the kexec_file_load
>> syscall whereas it could prevent one via the kexec_load syscall. Mandate
>> signature verification for those cases.
>>
>> Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
>> Cc: Matthew Garrett <[email protected]>
>> Cc: Jiri Bohac <[email protected]>
>> Cc: David Howells <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Signed-off-by: Coiby Xu <[email protected]>
>
>Other than correcting the function name to mandate_signature_verificati
>on(),
Applied to v2, thanks for correcting me! Btw, I realize I overwrote the
return code of kexec_image_verify_sig with
mandate_signature_verification's. v2 has fixed this issue as well.
>
>Reviewed-by: Mimi Zohar <[email protected]>
And thanks for the review!
--
Best regards,
Coiby
--
Best regards,
Coiby
A kernel builder may not enable KEXEC_SIG and some architectures like
ppc64 simply don't have KEXEC_SIG. In these cases, unless both
IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
unsigned kernel image from being kexec'ed via the kexec_file_load
syscall whereas it could prevent one via the kexec_load syscall. Mandate
signature verification for those cases.
Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
Cc: Matthew Garrett <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: David Howells <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Coiby Xu <[email protected]>
Reviewed-by: Mimi Zohar <[email protected]>
---
v2
- collect reviewed-by tag from Mimi
- s/mandate_signatute_verification/mandate_signature_verification [Mimi]
- return the status of kexec_image_verify_sig correctly when signature
verification is not mandated
---
kernel/kexec_file.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 45637511e0de..dcde7a50fbeb 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -125,6 +125,17 @@ void kimage_file_post_load_cleanup(struct kimage *image)
image->image_loader_data = NULL;
}
+static bool mandate_signature_verification(void)
+{
+ /*
+ * If IMA is guaranteed to appraise a signature on the kexec
+ * image, permit it even if the kernel is otherwise locked
+ * down.
+ */
+ return !ima_appraise_signature(READING_KEXEC_IMAGE) &&
+ security_locked_down(LOCKDOWN_KEXEC);
+}
+
#ifdef CONFIG_KEXEC_SIG
#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
@@ -168,13 +179,7 @@ kimage_validate_signature(struct kimage *image)
return ret;
}
- /*
- * If IMA is guaranteed to appraise a signature on the kexec
- * image, permit it even if the kernel is otherwise locked
- * down.
- */
- if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
- security_locked_down(LOCKDOWN_KEXEC))
+ if (mandate_signature_verification())
return -EPERM;
pr_debug("kernel signature verification failed (%d).\n", ret);
@@ -211,10 +216,13 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
#ifdef CONFIG_KEXEC_SIG
ret = kimage_validate_signature(image);
-
+#else
+ if (mandate_signature_verification())
+ ret = -EPERM;
+#endif
if (ret)
goto out;
-#endif
+
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
--
2.38.1
On Tue, 2022-11-22 at 10:36 +0800, Coiby Xu wrote:
> Hi Mimi,
>
> On Mon, Nov 21, 2022 at 01:23:57PM -0500, Mimi Zohar wrote:
> >Hi Coiby,
> >
> >On Mon, 2022-11-21 at 15:29 +0800, Coiby Xu wrote:
> >> A kernel builder may not enable KEXEC_SIG and some architectures like
> >> ppc64 simply don't have KEXEC_SIG. In these cases, unless both
> >> IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
> >> unsigned kernel image from being kexec'ed via the kexec_file_load
> >> syscall whereas it could prevent one via the kexec_load syscall. Mandate
> >> signature verification for those cases.
> >>
> >> Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
> >> Cc: Matthew Garrett <[email protected]>
> >> Cc: Jiri Bohac <[email protected]>
> >> Cc: David Howells <[email protected]>
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> Signed-off-by: Coiby Xu <[email protected]>
> >
> >Other than correcting the function name to mandate_signature_verificati
> >on(),
>
> Applied to v2, thanks for correcting me! Btw, I realize I overwrote the
> return code of kexec_image_verify_sig with
> mandate_signature_verification's. v2 has fixed this issue as well.
>
> >
> >Reviewed-by: Mimi Zohar <[email protected]>
>
> And thanks for the review!
You're welcome.
Without either IMA_ARCH or KEXEC_SIG enabled, the kexec selftest
test_kexec_file_load.sh properly failed with "kexec_file_load failed
[PASS]", but from the informational messages output, it isn't clear why
it failed. This should be corrected.
--
thanks,
Mimi
On Mon, Nov 28, 2022 at 12:16:08PM -0500, Mimi Zohar wrote:
>On Tue, 2022-11-22 at 10:36 +0800, Coiby Xu wrote:
>> Hi Mimi,
>>
>> On Mon, Nov 21, 2022 at 01:23:57PM -0500, Mimi Zohar wrote:
>> >Hi Coiby,
>> >
>> >On Mon, 2022-11-21 at 15:29 +0800, Coiby Xu wrote:
>> >> A kernel builder may not enable KEXEC_SIG and some architectures like
>> >> ppc64 simply don't have KEXEC_SIG. In these cases, unless both
>> >> IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
>> >> unsigned kernel image from being kexec'ed via the kexec_file_load
>> >> syscall whereas it could prevent one via the kexec_load syscall. Mandate
>> >> signature verification for those cases.
>> >>
>> >> Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
>> >> Cc: Matthew Garrett <[email protected]>
>> >> Cc: Jiri Bohac <[email protected]>
>> >> Cc: David Howells <[email protected]>
>> >> Cc: [email protected]
>> >> Cc: [email protected]
>> >> Signed-off-by: Coiby Xu <[email protected]>
>> >
>> >Other than correcting the function name to mandate_signature_verificati
>> >on(),
>>
>> Applied to v2, thanks for correcting me! Btw, I realize I overwrote the
>> return code of kexec_image_verify_sig with
>> mandate_signature_verification's. v2 has fixed this issue as well.
>>
>> >
>> >Reviewed-by: Mimi Zohar <[email protected]>
>>
>> And thanks for the review!
>
>You're welcome.
>
>Without either IMA_ARCH or KEXEC_SIG enabled, the kexec selftest
>test_kexec_file_load.sh properly failed with "kexec_file_load failed
>[PASS]", but from the informational messages output, it isn't clear why
>it failed. This should be corrected.
Thanks for the suggestion! I've added some tests in v3 and now the
message is "# kexec_file_load failed (missing IMA sig) [PASS]".
>
>--
>thanks,
>
>Mimi
>
--
Best regards,
Coiby