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Subject[PATCH v4 11/11] evm: crypto hash replaced by shash
Date
From: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>

Using shash is more efficient, because the algorithm is allocated only
once. Only the descriptor to store the hash state needs to be allocated
for every operation.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
security/integrity/evm/evm.h | 2 +
security/integrity/evm/evm_crypto.c | 94 ++++++++++++++++++++---------------
security/integrity/evm/evm_main.c | 6 +-
3 files changed, 58 insertions(+), 44 deletions(-)
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index 65ab9db..08b0a84 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -20,6 +20,8 @@ extern int evm_initialized;
extern char *evm_hmac;
extern int evm_hmac_size;

+extern struct crypto_shash *hmac_tfm;
+
/* List of EVM protected security xattrs */
extern char *evm_config_xattrnames[];

diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index e029a37..4b2d040 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -17,7 +17,7 @@
#include <linux/crypto.h>
#include <linux/xattr.h>
#include <keys/encrypted-type.h>
-#include <linux/scatterlist.h>
+#include <crypto/hash.h>
#include "evm.h"

#define EVMKEY "evm-key"
@@ -25,23 +25,41 @@
static unsigned char evmkey[MAX_KEY_SIZE];
static int evmkey_len = MAX_KEY_SIZE;

-static int init_desc(struct hash_desc *desc)
+struct crypto_shash *hmac_tfm;
+
+static struct shash_desc *init_desc(void)
{
int rc;
+ struct shash_desc *desc;
+
+ if (hmac_tfm == NULL) {
+ hmac_tfm = crypto_alloc_shash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(hmac_tfm)) {
+ pr_err("Can not allocate %s (reason: %ld)\n",
+ evm_hmac, PTR_ERR(hmac_tfm));
+ rc = PTR_ERR(hmac_tfm);
+ hmac_tfm = NULL;
+ return ERR_PTR(rc);
+ }
+ }
+
+ desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac_tfm),
+ GFP_KERNEL);
+ if (!desc)
+ return ERR_PTR(-ENOMEM);
+
+ desc->tfm = hmac_tfm;
+ desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+ crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);

- desc->tfm = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(desc->tfm)) {
- pr_info("Can not allocate %s (reason: %ld)\n",
- evm_hmac, PTR_ERR(desc->tfm));
- rc = PTR_ERR(desc->tfm);
- return rc;
+ rc = crypto_shash_init(desc);
+ if (rc) {
+ kfree(desc);
+ return ERR_PTR(rc);
}
- desc->flags = 0;
- crypto_hash_setkey(desc->tfm, evmkey, evmkey_len);
- rc = crypto_hash_init(desc);
- if (rc)
- crypto_free_hash(desc->tfm);
- return rc;
+
+ return desc;
}

/* Protect against 'cutting & pasting' security.evm xattr, include inode
@@ -50,7 +68,7 @@ static int init_desc(struct hash_desc *desc)
* (Additional directory/file metadata needs to be added for more complete
* protection.)
*/
-static void hmac_add_misc(struct hash_desc *desc, struct inode *inode,
+static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
char *digest)
{
struct h_misc {
@@ -60,7 +78,6 @@ static void hmac_add_misc(struct hash_desc *desc, struct inode *inode,
gid_t gid;
umode_t mode;
} hmac_misc;
- struct scatterlist sg[1];

memset(&hmac_misc, 0, sizeof hmac_misc);
hmac_misc.ino = inode->i_ino;
@@ -68,9 +85,8 @@ static void hmac_add_misc(struct hash_desc *desc, struct inode *inode,
hmac_misc.uid = inode->i_uid;
hmac_misc.gid = inode->i_gid;
hmac_misc.mode = inode->i_mode;
- sg_init_one(sg, &hmac_misc, sizeof hmac_misc);
- crypto_hash_update(desc, sg, sizeof hmac_misc);
- crypto_hash_final(desc, digest);
+ crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof hmac_misc);
+ crypto_shash_final(desc, digest);
}

/*
@@ -85,8 +101,7 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
char *digest)
{
struct inode *inode = dentry->d_inode;
- struct hash_desc desc;
- struct scatterlist sg[1];
+ struct shash_desc *desc;
char **xattrname;
size_t xattr_size = 0;
char *xattr_value = NULL;
@@ -95,17 +110,17 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,

if (!inode->i_op || !inode->i_op->getxattr)
return -EOPNOTSUPP;
- error = init_desc(&desc);
- if (error)
- return error;
+ desc = init_desc();
+ if (IS_ERR(desc))
+ return PTR_ERR(desc);

error = -ENODATA;
for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
if ((req_xattr_name && req_xattr_value)
&& !strcmp(*xattrname, req_xattr_name)) {
error = 0;
- sg_init_one(sg, req_xattr_value, req_xattr_value_len);
- crypto_hash_update(&desc, sg, req_xattr_value_len);
+ crypto_shash_update(desc, (const u8 *)req_xattr_value,
+ req_xattr_value_len);
continue;
}
size = vfs_getxattr_alloc(dentry, *xattrname,
@@ -119,13 +134,13 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,

error = 0;
xattr_size = size;
- sg_init_one(sg, xattr_value, xattr_size);
- crypto_hash_update(&desc, sg, xattr_size);
+ crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
}
- hmac_add_misc(&desc, inode, digest);
- kfree(xattr_value);
+ hmac_add_misc(desc, inode, digest);
+
out:
- crypto_free_hash(desc.tfm);
+ kfree(xattr_value);
+ kfree(desc);
return error;
}

@@ -156,20 +171,17 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
char *hmac_val)
{
- struct hash_desc desc;
- struct scatterlist sg[1];
- int error;
+ struct shash_desc *desc;

- error = init_desc(&desc);
- if (error != 0) {
+ desc = init_desc();
+ if (IS_ERR(desc)) {
printk(KERN_INFO "init_desc failed\n");
- return error;
+ return PTR_ERR(desc);
}

- sg_init_one(sg, lsm_xattr->value, lsm_xattr->value_len);
- crypto_hash_update(&desc, sg, lsm_xattr->value_len);
- hmac_add_misc(&desc, inode, hmac_val);
- crypto_free_hash(desc.tfm);
+ crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
+ hmac_add_misc(desc, inode, hmac_val);
+ kfree(desc);
return 0;
}

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 98941ab..af1bc6a 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -19,6 +19,7 @@
#include <linux/xattr.h>
#include <linux/integrity.h>
#include <linux/evm.h>
+#include <crypto/hash.h>
#include "evm.h"

int evm_initialized;
@@ -283,12 +284,10 @@ out:
}
EXPORT_SYMBOL_GPL(evm_inode_post_init_security);

-static struct crypto_hash *tfm_hmac; /* preload crypto alg */
static int __init init_evm(void)
{
int error;

- tfm_hmac = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
error = evm_init_secfs();
if (error < 0) {
printk(KERN_INFO "EVM: Error registering secfs\n");
@@ -301,7 +300,8 @@ err:
static void __exit cleanup_evm(void)
{
evm_cleanup_secfs();
- crypto_free_hash(tfm_hmac);
+ if (hmac_tfm)
+ crypto_free_shash(hmac_tfm);
}

/*
--
1.7.3.4


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