evm: crypto hash replaced by shash

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.

Changelog v6:
- check for crypto_shash_setkey failure

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Author: Dmitry Kasatkin

security/integrity/evm/evm.h

@@ -19,6 +19,8 @@
 extern int evm_initialized;
 extern char *evm_hmac;
 
+extern struct crypto_shash *hmac_tfm;
+
 /* List of EVM protected security xattrs */
 extern char *evm_config_xattrnames[];
 

security/integrity/evm/evm_crypto.c

@@ -16,35 +16,51 @@
 #include <linux/module.h>
 #include <linux/crypto.h>
 #include <linux/xattr.h>
-#include <linux/scatterlist.h>
 #include <keys/encrypted-type.h>
+#include <crypto/hash.h>
 #include "evm.h"
 
 #define EVMKEY "evm-key"
 #define MAX_KEY_SIZE 128
 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;
-
-	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;
+	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->flags = 0;
-	rc = crypto_hash_setkey(desc->tfm, evmkey, evmkey_len);
+
+	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;
+
+	rc = crypto_shash_setkey(hmac_tfm, evmkey, evmkey_len);
 	if (rc)
 		goto out;
-	rc = crypto_hash_init(desc);
+	rc = crypto_shash_init(desc);
 out:
-	if (rc)
-		crypto_free_hash(desc->tfm);
-	return rc;
+	if (rc) {
+		kfree(desc);
+		return ERR_PTR(rc);
+	}
+	return desc;
 }
 
 /* Protect against 'cutting & pasting' security.evm xattr, include inode
@@ -53,7 +69,7 @@ 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 {
@@ -63,17 +79,15 @@ 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;
 	hmac_misc.generation = inode->i_generation;
 	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);
 }
 
 /*
@@ -88,8 +102,7 @@ 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;
@@ -98,17 +111,17 @@ 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,
@@ -122,13 +135,13 @@ 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;
 }
 
@@ -160,20 +173,17 @@ 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;
 }
 

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 @@ int evm_inode_init_security(struct inode *inode,
 }
 EXPORT_SYMBOL_GPL(evm_inode_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 @@ static int __init init_evm(void)
 static void __exit cleanup_evm(void)
 {
 	evm_cleanup_secfs();
-	crypto_free_hash(tfm_hmac);
+	if (hmac_tfm)
+		crypto_free_shash(hmac_tfm);
 }
 
 /*