From 6be5cc5246f807fd8ede9f5f1bb2826f2c598658 Mon Sep 17 00:00:00 2001
From: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Date: Wed, 9 Mar 2011 14:28:20 -0500
Subject: [PATCH] evm: add support for different security.evm data types
EVM protects a file's security extended attributes(xattrs) against integrity
attacks. The current patchset maintains an HMAC-sha1 value across the security
xattrs, storing the value as the extended attribute 'security.evm'. We
anticipate other methods for protecting the security extended attributes.
This patch reserves the first byte of 'security.evm' as a place holder for
the type of method.
Changelog v6:
- move evm_ima_xattr_type definition to security/integrity/integrity.h
- defined a structure for the EVM xattr called evm_ima_xattr_data
(based on Serge Hallyn's suggestion)
- removed unnecessary memset
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
---
include/linux/integrity.h | 1 +
security/integrity/evm/evm_crypto.c | 11 +++++++----
security/integrity/evm/evm_main.c | 10 +++++-----
security/integrity/integrity.h | 11 +++++++++++
4 files changed, 24 insertions(+), 9 deletions(-)
diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index e715a2abcea23..9684433856787 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -19,6 +19,7 @@ enum integrity_status {
INTEGRITY_UNKNOWN,
};
+/* List of EVM protected security xattrs */
#ifdef CONFIG_INTEGRITY
extern int integrity_inode_alloc(struct inode *inode);
extern void integrity_inode_free(struct inode *inode);
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index d49bb002f3dad..c631b99bda954 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -141,14 +141,17 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
const char *xattr_value, size_t xattr_value_len)
{
struct inode *inode = dentry->d_inode;
- u8 hmac[SHA1_DIGEST_SIZE];
+ struct evm_ima_xattr_data xattr_data;
int rc = 0;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
- xattr_value_len, hmac);
- if (rc == 0)
+ xattr_value_len, xattr_data.digest);
+ if (rc == 0) {
+ xattr_data.type = EVM_XATTR_HMAC;
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
- hmac, SHA1_DIGEST_SIZE, 0);
+ &xattr_data,
+ sizeof(xattr_data), 0);
+ }
else if (rc == -ENODATA)
rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
return rc;
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index a8fa45fef8f1c..c0580dd15ec0f 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -51,20 +51,20 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
size_t xattr_value_len,
struct integrity_iint_cache *iint)
{
- char hmac_val[SHA1_DIGEST_SIZE];
+ struct evm_ima_xattr_data xattr_data;
int rc;
if (iint->hmac_status != INTEGRITY_UNKNOWN)
return iint->hmac_status;
- memset(hmac_val, 0, sizeof hmac_val);
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
- xattr_value_len, hmac_val);
+ xattr_value_len, xattr_data.digest);
if (rc < 0)
return INTEGRITY_UNKNOWN;
- rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, hmac_val, sizeof hmac_val,
- GFP_NOFS);
+ xattr_data.type = EVM_XATTR_HMAC;
+ rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
+ sizeof xattr_data, GFP_NOFS);
if (rc < 0)
goto err_out;
iint->hmac_status = INTEGRITY_PASS;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 397a46b3992fa..7efbf560b7d5a 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -18,6 +18,17 @@
/* iint cache flags */
#define IMA_MEASURED 0x01
+enum evm_ima_xattr_type {
+ IMA_XATTR_DIGEST = 0x01,
+ EVM_XATTR_HMAC,
+ EVM_IMA_XATTR_DIGSIG,
+};
+
+struct evm_ima_xattr_data {
+ u8 type;
+ u8 digest[SHA1_DIGEST_SIZE];
+} __attribute__((packed));
+
/* integrity data associated with an inode */
struct integrity_iint_cache {
struct rb_node rb_node; /* rooted in integrity_iint_tree */
--
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