linux-kernel - [PATCH 3/3] evm: audit integrity metadata failures

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Message-Id: <1366805441-12187-3-git-send-email-zohar@linux.vnet.ibm.com>
Date:	Wed, 24 Apr 2013 08:10:41 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	linux-security-module@...r.kernel.org
Cc:	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Hugh Dickins <hughd@...gle.com>,
	Eric Paris <eparis@...hat.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] evm: audit integrity metadata failures

Before modifying an EVM protected extended attribute or any other
metadata included in the HMAC calculation, the existing 'security.evm'
is verified.  This patch adds calls to integrity_audit_msg() to audit
integrity metadata failures.

Reported-by: Sven Vermeulen <sven.vermeulen@...hos.be>
Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
---
 security/integrity/evm/evm_main.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index cdbde17..0c4c6e7 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -16,6 +16,7 @@
 
 #include <linux/module.h>
 #include <linux/crypto.h>
+#include <linux/audit.h>
 #include <linux/xattr.h>
 #include <linux/integrity.h>
 #include <linux/evm.h>
@@ -24,6 +25,9 @@
 
 int evm_initialized;
 
+static char *integrity_status_msg[] = {
+	"pass", "fail", "no_label", "no_xattrs", "unknown"
+};
 char *evm_hmac = "hmac(sha1)";
 char *evm_hash = "sha1";
 int evm_hmac_version = CONFIG_EVM_HMAC_VERSION;
@@ -262,9 +266,15 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
 		if ((evm_status == INTEGRITY_PASS) ||
 		    (evm_status == INTEGRITY_NOXATTRS))
 			return 0;
-		return -EPERM;
+		goto out;
 	}
 	evm_status = evm_verify_current_integrity(dentry);
+out:
+	if (evm_status != INTEGRITY_PASS)
+		integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
+				    dentry->d_name.name, "appraise_metadata",
+				    integrity_status_msg[evm_status],
+				    -EPERM, 0);
 	return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
 }
 
@@ -357,6 +367,10 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
 	if ((evm_status == INTEGRITY_PASS) ||
 	    (evm_status == INTEGRITY_NOXATTRS))
 		return 0;
+	integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
+			    dentry->d_name.name, "appraise_metadata",
+			    integrity_status_msg[evm_status],
+			    -EPERM, 0);
 	return -EPERM;
 }
 
-- 
1.8.1.rc3

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