linux-kernel - [PATCH v2 05/12] evm: Load EVM key in ima_load

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Date:   Fri, 4 Sep 2020 11:26:36 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <zohar@...ux.ibm.com>, <mjg59@...gle.com>
CC:     <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v2 05/12] evm: Load EVM key in ima_load_x509() to avoid appraisal

Public keys do not need to be appraised by IMA as the restriction on the
IMA/EVM keyrings ensures that a key is loaded only if it is signed with a
key in the primary or secondary keyring.

However, when evm_load_x509() is loaded, appraisal is already enabled and
a valid IMA signature must be added to the EVM key to pass verification.

Since the restriction is applied on both IMA and EVM keyrings, it is safe
to disable appraisal also when the EVM key is loaded. This patch calls
evm_load_x509() inside ima_load_x509() if CONFIG_IMA_LOAD_X509 is defined.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
---
 security/integrity/iint.c         | 2 ++
 security/integrity/ima/ima_init.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index 1d20003243c3..7d08c31c612f 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -200,7 +200,9 @@ int integrity_kernel_read(struct file *file, loff_t offset,
 void __init integrity_load_keys(void)
 {
 	ima_load_x509();
+#ifndef CONFIG_IMA_LOAD_X509
 	evm_load_x509();
+#endif
 }
 
 static int __init integrity_fs_init(void)
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 4902fe7bd570..9d29a1680da8 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -106,6 +106,10 @@ void __init ima_load_x509(void)
 
 	ima_policy_flag &= ~unset_flags;
 	integrity_load_x509(INTEGRITY_KEYRING_IMA, CONFIG_IMA_X509_PATH);
+
+	/* load also EVM key to avoid appraisal */
+	evm_load_x509();
+
 	ima_policy_flag |= unset_flags;
 }
 #endif
-- 
2.27.GIT