[v1] sefltest/ima: support appended signatures (modsig)

Commit Message

Mimi Zohar Aug. 28, 2019, 3:14 p.m. UTC

In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
image can be signed with an appended signature, using the same
scripts/sign-file tool that is used to sign kernel modules.

This patch adds support for detecting a kernel image signed with an
appended signature and updates the existing test messages
appropriately.

Reviewed-by: Petr Vorel <[e-mail]>
Signed-off-by: Mimi Zohar <[e-mail]>
---
 .../selftests/kexec/test_kexec_file_load.sh        | 38 +++++++++++++++++++---
 1 file changed, 34 insertions(+), 4 deletions(-)

Comments

Shuah Aug. 28, 2019, 3:53 p.m. UTC | #1

On 8/28/19 9:14 AM, Mimi Zohar wrote:
> In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
> image can be signed with an appended signature, using the same
> scripts/sign-file tool that is used to sign kernel modules.
> 
> This patch adds support for detecting a kernel image signed with an
> appended signature and updates the existing test messages
> appropriately.
> 
> Reviewed-by: Petr Vorel <[e-mail]>
> Signed-off-by: Mimi Zohar <[e-mail]>
> ---

Thanks Mimi. This commit log looks good. My Ack for the patch
to go through the IMA tree.

Acked-by: Shuah Khan <[e-mail]>

thanks,
-- Shuah

Mimi Zohar Aug. 28, 2019, 3:55 p.m. UTC | #2

On Wed, 2019-08-28 at 09:53 -0600, shuah wrote:
> On 8/28/19 9:14 AM, Mimi Zohar wrote:
> > In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
> > image can be signed with an appended signature, using the same
> > scripts/sign-file tool that is used to sign kernel modules.
> > 
> > This patch adds support for detecting a kernel image signed with an
> > appended signature and updates the existing test messages
> > appropriately.
> > 
> > Reviewed-by: Petr Vorel <[e-mail]>
> > Signed-off-by: Mimi Zohar <[e-mail]>
> > ---
> 
> Thanks Mimi. This commit log looks good. My Ack for the patch
> to go through the IMA tree.
> 
> Acked-by: Shuah Khan <[e-mail]>

Thanks!

Mimi

Thiago Jung Bauermann Aug. 28, 2019, 11:38 p.m. UTC | #3

Hello Mimi,

Mimi Zohar <[e-mail]> writes:

> In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
> image can be signed with an appended signature, using the same
> scripts/sign-file tool that is used to sign kernel modules.
>
> This patch adds support for detecting a kernel image signed with an
> appended signature and updates the existing test messages
> appropriately.
>
> Reviewed-by: Petr Vorel <[e-mail]>
> Signed-off-by: Mimi Zohar <[e-mail]>

Thanks for doing this!

Reviewed-by: Thiago Jung Bauermann <[e-mail]>

Mimi Zohar Aug. 29, 2019, 12:01 a.m. UTC | #4

On Wed, 2019-08-28 at 20:38 -0300, Thiago Jung Bauermann wrote:
> Hello Mimi,
> 
> Mimi Zohar <[e-mail]> writes:
> 
> > In addition to the PE/COFF and IMA xattr signatures, the kexec kernel
> > image can be signed with an appended signature, using the same
> > scripts/sign-file tool that is used to sign kernel modules.
> >
> > This patch adds support for detecting a kernel image signed with an
> > appended signature and updates the existing test messages
> > appropriately.
> >
> > Reviewed-by: Petr Vorel <[e-mail]>
> > Signed-off-by: Mimi Zohar <[e-mail]>
> 
> Thanks for doing this!

You're welcome.  This isn't in lieu of a proper regression test that
verifies the IMA measurement list template modsig and d-modsig data
fields.  That still needs to be written.

thanks,

Mimi

Patch

diff --git a/tools/testing/selftests/kexec/test_kexec_file_load.sh b/tools/testing/selftests/kexec/test_kexec_file_load.sh
index fa7c24e8eefb..2ff600388c30 100755
--- a/tools/testing/selftests/kexec/test_kexec_file_load.sh
+++ b/tools/testing/selftests/kexec/test_kexec_file_load.sh
@@ -37,11 +37,20 @@  is_ima_sig_required()
 	# sequentially.  As a result, a policy rule may be defined, but
 	# might not necessarily be used.  This test assumes if a policy
 	# rule is specified, that is the intent.
+
+	# First check for appended signature (modsig), then xattr
 	if [ $ima_read_policy -eq 1 ]; then
 		check_ima_policy "appraise" "func=KEXEC_KERNEL_CHECK" \
-			"appraise_type=imasig"
+			"appraise_type=imasig|modsig"
 		ret=$?
-		[ $ret -eq 1 ] && log_info "IMA signature required";
+		if [ $ret -eq 1 ]; then
+			log_info "IMA or appended(modsig) signature required"
+		else
+			check_ima_policy "appraise" "func=KEXEC_KERNEL_CHECK" \
+				"appraise_type=imasig"
+			ret=$?
+			[ $ret -eq 1 ] && log_info "IMA signature required";
+		fi
 	fi
 	return $ret
 }
@@ -84,6 +93,22 @@  check_for_imasig()
 	return $ret
 }
 
+# Return 1 for appended signature (modsig) found and 0 for not found.
+check_for_modsig()
+{
+	local module_sig_string="~Module signature appended~"
+	local sig="$(tail --bytes $((${#module_sig_string} + 1)) $KERNEL_IMAGE)"
+	local ret=0
+
+	if [ "$sig" == "$module_sig_string" ]; then
+		ret=1
+		log_info "kexec kernel image modsig signed"
+	else
+		log_info "kexec kernel image not modsig signed"
+	fi
+	return $ret
+}
+
 kexec_file_load_test()
 {
 	local succeed_msg="kexec_file_load succeeded"
@@ -98,7 +123,8 @@  kexec_file_load_test()
 		# In secureboot mode with an architecture  specific
 		# policy, make sure either an IMA or PE signature exists.
 		if [ $secureboot -eq 1 ] && [ $arch_policy -eq 1 ] && \
-			[ $ima_signed -eq 0 ] && [ $pe_signed -eq 0 ]; then
+			[ $ima_signed -eq 0 ] && [ $pe_signed -eq 0 ] \
+			  && [ $ima_modsig -eq 0 ]; then
 			log_fail "$succeed_msg (missing sig)"
 		fi
 
@@ -107,7 +133,8 @@  kexec_file_load_test()
 			log_fail "$succeed_msg (missing PE sig)"
 		fi
 
-		if [ $ima_sig_required -eq 1 ] && [ $ima_signed -eq 0 ]; then
+		if [ $ima_sig_required -eq 1 ] && [ $ima_signed -eq 0 ] \
+		     && [ $ima_modsig -eq 0 ]; then
 			log_fail "$succeed_msg (missing IMA sig)"
 		fi
 
@@ -204,5 +231,8 @@  pe_signed=$?
 check_for_imasig
 ima_signed=$?
 
+check_for_modsig
+ima_modsig=$?
+
 # Test loading the kernel image via kexec_file_load syscall
 kexec_file_load_test