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

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

[Mimi Zohar]

Detect and allow appended signatures.

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 .../selftests/kexec/test_kexec_file_load.sh        | 38 +++++++++++++++++++---
 1 file changed, 34 insertions(+), 4 deletions(-)

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
-- 
2.7.5

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

[Petr Vorel]

Hi Mimi,

> Detect and allow appended signatures.

> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

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

[shuah]

Hi Mimi,

On 8/28/19 6:39 AM, Mimi Zohar wrote:
> Detect and allow appended signatures.
> 

Can you please add a couple of more sentences on the feature
and what happens without it? I know this is a test for the
feature, however, it will be useful for users and testers to
know more about this test and the feature it is testing.

Also, are there test skip conditions to be concerned about?

Is there a dependency on another tree or would like me to take
this through kselftest tree?

> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>   .../selftests/kexec/test_kexec_file_load.sh        | 38 +++++++++++++++++++---
>   1 file changed, 34 insertions(+), 4 deletions(-)
> 
> 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
> 

thanks,
-- Shuah

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

[Mimi Zohar]

On Wed, 2019-08-28 at 08:45 -0600, shuah wrote:
> Hi Mimi,
> 
> On 8/28/19 6:39 AM, Mimi Zohar wrote:
> > Detect and allow appended signatures.
> > 
> 
> Can you please add a couple of more sentences on the feature
> and what happens without it? I know this is a test for the
> feature, however, it will be useful for users and testers to
> know more about this test and the feature it is testing.

I've updated the patch description as requested.  

> Also, are there test skip conditions to be concerned about?

The kexec selftests tests the coordination of the different methods of
verifying the kexec kernel image.  As the appended signature support
is part of IMA, there is no new skip conditions.

> Is there a dependency on another tree or would like me to take
> this through kselftest tree?

I would prefer upstreaming this test with the rest of IMA support for
appended signatures.

thanks,

Mimi

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

[Jordan Hand]

On 8/28/19 5:39 AM, Mimi Zohar wrote:
> Detect and allow appended signatures.

Ran the tests successfully on x86_64 QEMU

Reviewed-by: Jordan Hand <jorhand@linux.microsoft.com>
Tested-by: Jordan Hand <jorhand@linux.microsoft.com>