From: Roberto Sassu <roberto.sassu@huawei.com>
To: <zohar@linux.ibm.com>, <mjg59@google.com>
Cc: <linux-integrity@vger.kernel.org>,
<linux-security-module@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
Roberto Sassu <roberto.sassu@huawei.com>,
<stable@vger.kernel.org>
Subject: [PATCH 03/11] evm: Refuse EVM_ALLOW_METADATA_WRITES only if the HMAC key is loaded
Date: Thu, 18 Jun 2020 18:01:25 +0200 [thread overview]
Message-ID: <20200618160133.937-3-roberto.sassu@huawei.com> (raw)
In-Reply-To: <20200618160133.937-1-roberto.sassu@huawei.com>
Granting metadata write is safe if the HMAC key is not loaded, as it won't
let an attacker obtain a valid HMAC from corrupted xattrs. evm_write_key()
however does not allow it if any key is loaded, including a public key,
which should not be a problem.
This patch allows setting EVM_ALLOW_METADATA_WRITES if the EVM_INIT_HMAC
flag is not set.
Cc: stable@vger.kernel.org # 4.16.x
Fixes: ae1ba1676b88e ("EVM: Allow userland to permit modification of EVM-protected metadata")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/evm/evm_secfs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index cfc3075769bb..92fe26ace797 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -84,7 +84,7 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
* keys are loaded.
*/
if ((i & EVM_ALLOW_METADATA_WRITES) &&
- ((evm_initialized & EVM_KEY_MASK) != 0) &&
+ ((evm_initialized & EVM_INIT_HMAC) != 0) &&
!(evm_initialized & EVM_ALLOW_METADATA_WRITES))
return -EPERM;
--
2.17.1
next prev parent reply other threads:[~2020-06-18 16:04 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 16:01 [PATCH 01/11] evm: Execute evm_inode_init_security() only when the HMAC key is loaded Roberto Sassu
2020-06-18 16:01 ` [PATCH 02/11] evm: Load EVM key in ima_load_x509() to avoid appraisal Roberto Sassu
2020-08-21 18:45 ` Mimi Zohar
2020-08-31 9:44 ` Roberto Sassu
2020-08-31 19:26 ` Mimi Zohar
2020-06-18 16:01 ` Roberto Sassu [this message]
2020-08-21 20:14 ` [PATCH 03/11] evm: Refuse EVM_ALLOW_METADATA_WRITES only if the HMAC key is loaded Mimi Zohar
2020-08-31 8:24 ` Roberto Sassu
2020-08-31 21:31 ` Mimi Zohar
2020-06-18 16:01 ` [PATCH 04/11] evm: Check size of security.evm before using it Roberto Sassu
2020-08-24 12:14 ` Mimi Zohar
2020-06-18 16:01 ` [PATCH 05/11] evm: Allow xattr/attr operations for portable signatures if check fails Roberto Sassu
2020-08-24 12:16 ` Mimi Zohar
2020-08-21 18:30 ` [PATCH 01/11] evm: Execute evm_inode_init_security() only when the HMAC key is loaded Mimi Zohar
2020-08-24 17:45 ` Mimi Zohar
2020-09-02 11:42 ` Roberto Sassu
2020-09-02 13:40 ` Mimi Zohar
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