[v2,7/7] ima: Support platform keyring for kernel appraisal
diff mbox series

Message ID 20181208202705.18673-8-nayna@linux.ibm.com
State New
Headers show
Series
  • add platform/firmware keys support for kernel verification by IMA
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Commit Message

Nayna Jain Dec. 8, 2018, 8:27 p.m. UTC
On secure boot enabled systems, the bootloader verifies the kernel
image and possibly the initramfs signatures based on a set of keys. A
soft reboot(kexec) of the system, with the same kernel image and
initramfs, requires access to the original keys to verify the
signatures.

This patch allows IMA-appraisal access to those original keys, now
loaded on the platform keyring, needed for verifying the kernel image
and initramfs signatures.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
- replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
with INTEGRITY_KEYRING_IMA for readability
Suggested-by: Serge Hallyn <serge@hallyn.com>
---
Changelog:

v2:
- replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
with INTEGRITY_KEYRING_IMA for readability

 security/integrity/ima/ima_appraise.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Comments

James Morris Dec. 11, 2018, 6:53 p.m. UTC | #1
On Sun, 9 Dec 2018, Nayna Jain wrote:

> On secure boot enabled systems, the bootloader verifies the kernel
> image and possibly the initramfs signatures based on a set of keys. A
> soft reboot(kexec) of the system, with the same kernel image and
> initramfs, requires access to the original keys to verify the
> signatures.
> 
> This patch allows IMA-appraisal access to those original keys, now
> loaded on the platform keyring, needed for verifying the kernel image
> and initramfs signatures.
> 
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> - replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
> with INTEGRITY_KEYRING_IMA for readability
> Suggested-by: Serge Hallyn <serge@hallyn.com>


Reviewed-by: James Morris <james.morris@microsoft.com>
Thiago Jung Bauermann Dec. 12, 2018, 6:14 p.m. UTC | #2
Hello,

Nayna Jain <nayna@linux.ibm.com> writes:

> On secure boot enabled systems, the bootloader verifies the kernel
> image and possibly the initramfs signatures based on a set of keys. A
> soft reboot(kexec) of the system, with the same kernel image and
> initramfs, requires access to the original keys to verify the
> signatures.
>
> This patch allows IMA-appraisal access to those original keys, now
> loaded on the platform keyring, needed for verifying the kernel image
> and initramfs signatures.
>
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> - replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
> with INTEGRITY_KEYRING_IMA for readability
> Suggested-by: Serge Hallyn <serge@hallyn.com>
> ---
> Changelog:
>
> v2:
> - replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
> with INTEGRITY_KEYRING_IMA for readability
>
>  security/integrity/ima/ima_appraise.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index deec1804a00a..e8f520450895 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -289,12 +289,21 @@ int ima_appraise_measurement(enum ima_hooks func,
>  	case EVM_IMA_XATTR_DIGSIG:
>  		set_bit(IMA_DIGSIG, &iint->atomic_flags);
>  		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
> -					     (const char *)xattr_value, rc,
> +					     (const char *)xattr_value,
> +					     xattr_len,
>  					     iint->ima_hash->digest,
>  					     iint->ima_hash->length);
>  		if (rc == -EOPNOTSUPP) {
>  			status = INTEGRITY_UNKNOWN;
> -		} else if (rc) {
> +			break;
> +		}
> +		if (rc && func == KEXEC_KERNEL_CHECK)
> +			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
> +						     (const char *)xattr_value,
> +						     xattr_len,
> +						     iint->ima_hash->digest,
> +						     iint->ima_hash->length);

If CONFIG_INTEGRITY_PLATFORM_KEYRING=n the second call to
integrity_digsig_verify() above will always fail, and the audit message
of failed signature verifications for KEXEC_KERNEL will always log the
same rc value, which is whatever request_key() returns when asked to
look for an inexistent keyring.

Here is a patch which only performs the second try if the platform
keyring is enabled.


From d5fb94ab9eb13f6294f8dc44d1344cb85dfa41b8 Mon Sep 17 00:00:00 2001
From: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Date: Wed, 12 Dec 2018 16:02:09 -0200
Subject: [PATCH] ima: Only use the platform keyring if it's enabled

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
 security/integrity/ima/ima_appraise.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index e8f520450895..f6ac405daabb 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -297,7 +297,8 @@ int ima_appraise_measurement(enum ima_hooks func,
 			status = INTEGRITY_UNKNOWN;
 			break;
 		}
-		if (rc && func == KEXEC_KERNEL_CHECK)
+		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
+		    func == KEXEC_KERNEL_CHECK)
 			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
 						     (const char *)xattr_value,
 						     xattr_len,
Mimi Zohar Dec. 13, 2018, 12:18 a.m. UTC | #3
On Wed, 2018-12-12 at 16:14 -0200, Thiago Jung Bauermann wrote:
[snip]

> Subject: [PATCH] ima: Only use the platform keyring if it's enabled
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

Good catch!  Thanks.

Mimi

> ---
>  security/integrity/ima/ima_appraise.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index e8f520450895..f6ac405daabb 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -297,7 +297,8 @@ int ima_appraise_measurement(enum ima_hooks func,
>  			status = INTEGRITY_UNKNOWN;
>  			break;
>  		}
> -		if (rc && func == KEXEC_KERNEL_CHECK)
> +		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
> +		    func == KEXEC_KERNEL_CHECK)
>  			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
>  						     (const char *)xattr_value,
>  						     xattr_len,
Thiago Jung Bauermann Dec. 13, 2018, 12:19 a.m. UTC | #4
Nayna Jain <nayna@linux.ibm.com> writes:

> On secure boot enabled systems, the bootloader verifies the kernel
> image and possibly the initramfs signatures based on a set of keys. A
> soft reboot(kexec) of the system, with the same kernel image and
> initramfs, requires access to the original keys to verify the
> signatures.
>
> This patch allows IMA-appraisal access to those original keys, now
> loaded on the platform keyring, needed for verifying the kernel image
> and initramfs signatures.
>
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> - replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
> with INTEGRITY_KEYRING_IMA for readability
> Suggested-by: Serge Hallyn <serge@hallyn.com>
> ---
> Changelog:
>
> v2:
> - replace 'rc' with 'xattr_len' when calling integrity_digsig_verify()
> with INTEGRITY_KEYRING_IMA for readability
>
>  security/integrity/ima/ima_appraise.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)

With the change to only access the platform keyring when it is enabled:

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

--
Thiago Jung Bauermann
IBM Linux Technology Center

Patch
diff mbox series

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index deec1804a00a..e8f520450895 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -289,12 +289,21 @@  int ima_appraise_measurement(enum ima_hooks func,
 	case EVM_IMA_XATTR_DIGSIG:
 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
 		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
-					     (const char *)xattr_value, rc,
+					     (const char *)xattr_value,
+					     xattr_len,
 					     iint->ima_hash->digest,
 					     iint->ima_hash->length);
 		if (rc == -EOPNOTSUPP) {
 			status = INTEGRITY_UNKNOWN;
-		} else if (rc) {
+			break;
+		}
+		if (rc && func == KEXEC_KERNEL_CHECK)
+			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
+						     (const char *)xattr_value,
+						     xattr_len,
+						     iint->ima_hash->digest,
+						     iint->ima_hash->length);
+		if (rc) {
 			cause = "invalid-signature";
 			status = INTEGRITY_FAIL;
 		} else {