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Message-Id: <1307017423-15093-18-git-send-email-zohar@linux.vnet.ibm.com>
Date: Thu, 2 Jun 2011 08:23:40 -0400
From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
To: linux-security-module@...r.kernel.org
Cc: Dmitry Kasatkin <dmitry.kasatkin@...ia.com>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
James Morris <jmorris@...ei.org>,
David Safford <safford@...son.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg KH <greg@...ah.com>,
Dmitry Kasatkin <dmitry.s.kasatkin@...il.com>,
Mimi Zohar <zohar@...ibm.com>
Subject: [PATCH v6 17/20] evm: evm_verify_hmac must not return INTEGRITY_UNKNOWN
From: Dmitry Kasatkin <dmitry.kasatkin@...ia.com>
If EVM is not supported or enabled, evm_verify_hmac() returns
INTEGRITY_UNKNOWN, which ima_appraise_measurement() ignores and sets
the appraisal status based solely on the security.ima verification.
evm_verify_hmac() also returns INTEGRITY_UNKNOWN for other failures, such
as temporary failures like -ENOMEM, resulting in possible attack vectors.
This patch changes the default return code for temporary/unexpected
failures, like -ENOMEM, from INTEGRITY_UNKNOWN to INTEGRITY_FAIL, making
evm_verify_hmac() fail safe.
As a result, failures need to be re-evaluated in order to catch both
temporary errors, such as the -ENOMEM, as well as errors that have been
resolved in fix mode.
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@...ia.com>
Signed-off-by: Mimi Zohar <zohar@...ibm.com>
---
security/integrity/evm/evm_main.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 14fbd38..9abe75b 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -56,13 +56,15 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
struct evm_ima_xattr_data xattr_data;
int rc;
- if (iint->hmac_status != INTEGRITY_UNKNOWN)
+ if (iint->hmac_status == INTEGRITY_PASS)
return iint->hmac_status;
+ /* if status is not PASS, try to check again - against -ENOMEM */
+
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, xattr_data.digest);
if (rc < 0)
- return INTEGRITY_UNKNOWN;
+ goto err_out;
xattr_data.type = EVM_XATTR_HMAC;
rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
@@ -77,11 +79,8 @@ err_out:
case -ENODATA: /* file not labelled */
iint->hmac_status = INTEGRITY_NOLABEL;
break;
- case -EINVAL:
- iint->hmac_status = INTEGRITY_FAIL;
- break;
default:
- iint->hmac_status = INTEGRITY_UNKNOWN;
+ iint->hmac_status = INTEGRITY_FAIL;
}
return iint->hmac_status;
}
--
1.7.3.4
--
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