KEYS: encrypted: Use SHA-256 library instead of crypto_shash

Instead of the "sha256" crypto_shash, just use sha256().  Similarly,
instead of the "hmac(sha256)" crypto_shash, just use
hmac_sha256_usingrawkey().  This is simpler and faster.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

Author: Eric Biggers

security/keys/Kconfig

@@ -87,10 +87,9 @@ config ENCRYPTED_KEYS
 	tristate "ENCRYPTED KEYS"
 	depends on KEYS
 	select CRYPTO
-	select CRYPTO_HMAC
 	select CRYPTO_AES
 	select CRYPTO_CBC
-	select CRYPTO_SHA256
+	select CRYPTO_LIB_SHA256
 	select CRYPTO_RNG
 	help
 	  This option provides support for create/encrypting/decrypting keys

security/keys/encrypted-keys/encrypted.c

@@ -27,7 +27,6 @@
 #include <linux/scatterlist.h>
 #include <linux/ctype.h>
 #include <crypto/aes.h>
-#include <crypto/hash.h>
 #include <crypto/sha2.h>
 #include <crypto/skcipher.h>
 #include <crypto/utils.h>
@@ -37,8 +36,6 @@
 
 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
 static const char KEY_USER_PREFIX[] = "user:";
-static const char hash_alg[] = "sha256";
-static const char hmac_alg[] = "hmac(sha256)";
 static const char blkcipher_alg[] = "cbc(aes)";
 static const char key_format_default[] = "default";
 static const char key_format_ecryptfs[] = "ecryptfs";
@@ -54,8 +51,6 @@ static int blksize;
 #define MIN_DATA_SIZE  20
 #define KEY_ENC32_PAYLOAD_LEN 32
 
-static struct crypto_shash *hash_tfm;
-
 enum {
 	Opt_new, Opt_load, Opt_update, Opt_err
 };
@@ -329,26 +324,6 @@ static struct key *request_user_key(const char *master_desc, const u8 **master_k
 	return ukey;
 }
 
-static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
-		     const u8 *buf, unsigned int buflen)
-{
-	struct crypto_shash *tfm;
-	int err;
-
-	tfm = crypto_alloc_shash(hmac_alg, 0, 0);
-	if (IS_ERR(tfm)) {
-		pr_err("encrypted_key: can't alloc %s transform: %ld\n",
-		       hmac_alg, PTR_ERR(tfm));
-		return PTR_ERR(tfm);
-	}
-
-	err = crypto_shash_setkey(tfm, key, keylen);
-	if (!err)
-		err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
-	crypto_free_shash(tfm);
-	return err;
-}
-
 enum derived_key_type { ENC_KEY, AUTH_KEY };
 
 /* Derive authentication/encryption key from trusted key */
@@ -357,7 +332,6 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 {
 	u8 *derived_buf;
 	unsigned int derived_buf_len;
-	int ret;
 
 	derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 	if (derived_buf_len < HASH_SIZE)
@@ -374,10 +348,9 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 
 	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 	       master_keylen);
-	ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
-				      derived_key);
+	sha256(derived_buf, derived_buf_len, derived_key);
 	kfree_sensitive(derived_buf);
-	return ret;
+	return 0;
 }
 
 static struct skcipher_request *init_skcipher_req(const u8 *key,
@@ -503,10 +476,10 @@ static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 		goto out;
 
 	digest = epayload->format + epayload->datablob_len;
-	ret = calc_hmac(digest, derived_key, sizeof derived_key,
-			epayload->format, epayload->datablob_len);
-	if (!ret)
-		dump_hmac(NULL, digest, HASH_SIZE);
+	hmac_sha256_usingrawkey(derived_key, sizeof(derived_key),
+				epayload->format, epayload->datablob_len,
+				digest);
+	dump_hmac(NULL, digest, HASH_SIZE);
 out:
 	memzero_explicit(derived_key, sizeof(derived_key));
 	return ret;
@@ -534,9 +507,8 @@ static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 	} else
 		p = epayload->format;
 
-	ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
-	if (ret < 0)
-		goto out;
+	hmac_sha256_usingrawkey(derived_key, sizeof(derived_key), p, len,
+				digest);
 	ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
 			    sizeof(digest));
 	if (ret) {
@@ -1011,29 +983,14 @@ static int __init init_encrypted(void)
 {
 	int ret;
 
-	hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
-	if (IS_ERR(hash_tfm)) {
-		pr_err("encrypted_key: can't allocate %s transform: %ld\n",
-		       hash_alg, PTR_ERR(hash_tfm));
-		return PTR_ERR(hash_tfm);
-	}
-
 	ret = aes_get_sizes();
 	if (ret < 0)
-		goto out;
-	ret = register_key_type(&key_type_encrypted);
-	if (ret < 0)
-		goto out;
-	return 0;
-out:
-	crypto_free_shash(hash_tfm);
-	return ret;
-
+		return ret;
+	return register_key_type(&key_type_encrypted);
 }
 
 static void __exit cleanup_encrypted(void)
 {
-	crypto_free_shash(hash_tfm);
 	unregister_key_type(&key_type_encrypted);
 }