Received-SPF: pass (google.com: best guess record for domain of linux-crypto-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Ard Biesheuvel <ard.biesheuvel@linaro.org>
To:     linux-crypto@vger.kernel.org
Cc:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Eric Biggers <ebiggers@google.com>
Subject: [RFC PATCH 2/3] dm crypt: switch to essiv shash
Date:   Fri, 14 Jun 2019 10:34:03 +0200
Message-Id: <20190614083404.20514-3-ard.biesheuvel@linaro.org>
In-Reply-To: <20190614083404.20514-1-ard.biesheuvel@linaro.org>
References: <20190614083404.20514-1-ard.biesheuvel@linaro.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-crypto-owner@vger.kernel.org
Precedence: bulk

Replace the open coded ESSIV handling with invocations into the new
ESSIV shash, created specifically for this purpose. Using this more
abstract interface allows the crypto subsystem to refactor the way
ciphers are used, and to provide better testing coverage.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/md/Kconfig    |   1 +
 drivers/md/dm-crypt.c | 137 ++++----------------
 2 files changed, 24 insertions(+), 114 deletions(-)

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 45254b3ef715..30ca87cf25db 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -271,6 +271,7 @@ config DM_CRYPT
 	depends on BLK_DEV_DM
 	select CRYPTO
 	select CRYPTO_CBC
+	select CRYPTO_ESSIV
 	---help---
 	  This device-mapper target allows you to create a device that
 	  transparently encrypts the data on it. You'll need to activate
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 1b16d34bb785..b66ef3de835a 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -98,11 +98,6 @@ struct crypt_iv_operations {
 		    struct dm_crypt_request *dmreq);
 };
 
-struct iv_essiv_private {
-	struct crypto_shash *hash_tfm;
-	u8 *salt;
-};
-
 struct iv_benbi_private {
 	int shift;
 };
@@ -155,7 +150,6 @@ struct crypt_config {
 
 	const struct crypt_iv_operations *iv_gen_ops;
 	union {
-		struct iv_essiv_private essiv;
 		struct iv_benbi_private benbi;
 		struct iv_lmk_private lmk;
 		struct iv_tcw_private tcw;
@@ -165,7 +159,7 @@ struct crypt_config {
 	unsigned short int sector_size;
 	unsigned char sector_shift;
 
-	/* ESSIV: struct crypto_cipher *essiv_tfm */
+	/* ESSIV: struct crypto_shash *essiv_tfm */
 	void *iv_private;
 	union {
 		struct crypto_skcipher **tfms;
@@ -326,94 +320,27 @@ static int crypt_iv_plain64be_gen(struct crypt_config *cc, u8 *iv,
 /* Initialise ESSIV - compute salt but no local memory allocations */
 static int crypt_iv_essiv_init(struct crypt_config *cc)
 {
-	struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
-	SHASH_DESC_ON_STACK(desc, essiv->hash_tfm);
-	struct crypto_cipher *essiv_tfm;
-	int err;
-
-	desc->tfm = essiv->hash_tfm;
-
-	err = crypto_shash_digest(desc, cc->key, cc->key_size, essiv->salt);
-	shash_desc_zero(desc);
-	if (err)
-		return err;
-
-	essiv_tfm = cc->iv_private;
+	struct crypto_shash *essiv_tfm = cc->iv_private;
 
-	err = crypto_cipher_setkey(essiv_tfm, essiv->salt,
-			    crypto_shash_digestsize(essiv->hash_tfm));
-	if (err)
-		return err;
-
-	return 0;
+	return crypto_shash_setkey(essiv_tfm, cc->key, cc->key_size);
 }
 
 /* Wipe salt and reset key derived from volume key */
 static int crypt_iv_essiv_wipe(struct crypt_config *cc)
 {
-	struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
-	unsigned salt_size = crypto_shash_digestsize(essiv->hash_tfm);
-	struct crypto_cipher *essiv_tfm;
-	int r, err = 0;
-
-	memset(essiv->salt, 0, salt_size);
+	struct crypto_shash *essiv_tfm;
 
 	essiv_tfm = cc->iv_private;
-	r = crypto_cipher_setkey(essiv_tfm, essiv->salt, salt_size);
-	if (r)
-		err = r;
-
-	return err;
-}
-
-/* Allocate the cipher for ESSIV */
-static struct crypto_cipher *alloc_essiv_cipher(struct crypt_config *cc,
-						struct dm_target *ti,
-						const u8 *salt,
-						unsigned int saltsize)
-{
-	struct crypto_cipher *essiv_tfm;
-	int err;
-
-	/* Setup the essiv_tfm with the given salt */
-	essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, 0);
-	if (IS_ERR(essiv_tfm)) {
-		ti->error = "Error allocating crypto tfm for ESSIV";
-		return essiv_tfm;
-	}
-
-	if (crypto_cipher_blocksize(essiv_tfm) != cc->iv_size) {
-		ti->error = "Block size of ESSIV cipher does "
-			    "not match IV size of block cipher";
-		crypto_free_cipher(essiv_tfm);
-		return ERR_PTR(-EINVAL);
-	}
-
-	err = crypto_cipher_setkey(essiv_tfm, salt, saltsize);
-	if (err) {
-		ti->error = "Failed to set key for ESSIV cipher";
-		crypto_free_cipher(essiv_tfm);
-		return ERR_PTR(err);
-	}
-
-	return essiv_tfm;
+	return crypto_shash_setkey(essiv_tfm, NULL, 0);
 }
 
 static void crypt_iv_essiv_dtr(struct crypt_config *cc)
 {
-	struct crypto_cipher *essiv_tfm;
-	struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
-
-	crypto_free_shash(essiv->hash_tfm);
-	essiv->hash_tfm = NULL;
-
-	kzfree(essiv->salt);
-	essiv->salt = NULL;
+	struct crypto_shash *essiv_tfm;
 
 	essiv_tfm = cc->iv_private;
-
 	if (essiv_tfm)
-		crypto_free_cipher(essiv_tfm);
+		crypto_free_shash(essiv_tfm);
 
 	cc->iv_private = NULL;
 }
@@ -421,9 +348,8 @@ static void crypt_iv_essiv_dtr(struct crypt_config *cc)
 static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
 			      const char *opts)
 {
-	struct crypto_cipher *essiv_tfm = NULL;
-	struct crypto_shash *hash_tfm = NULL;
-	u8 *salt = NULL;
+	struct crypto_shash *essiv_tfm = NULL;
+	u8 name[CRYPTO_MAX_ALG_NAME];
 	int err;
 
 	if (!opts) {
@@ -431,51 +357,34 @@ static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
 		return -EINVAL;
 	}
 
-	/* Allocate hash algorithm */
-	hash_tfm = crypto_alloc_shash(opts, 0, 0);
-	if (IS_ERR(hash_tfm)) {
-		ti->error = "Error initializing ESSIV hash";
-		err = PTR_ERR(hash_tfm);
-		goto bad;
-	}
-
-	salt = kzalloc(crypto_shash_digestsize(hash_tfm), GFP_KERNEL);
-	if (!salt) {
-		ti->error = "Error kmallocing salt storage in ESSIV";
-		err = -ENOMEM;
-		goto bad;
-	}
-
-	cc->iv_gen_private.essiv.salt = salt;
-	cc->iv_gen_private.essiv.hash_tfm = hash_tfm;
+	snprintf(name, CRYPTO_MAX_ALG_NAME, "essiv(%s,%s)", cc->cipher, opts);
 
-	essiv_tfm = alloc_essiv_cipher(cc, ti, salt,
-				       crypto_shash_digestsize(hash_tfm));
-	if (IS_ERR(essiv_tfm)) {
-		crypt_iv_essiv_dtr(cc);
+	essiv_tfm = crypto_alloc_shash(name, 0, 0);
+	if (IS_ERR(essiv_tfm))
 		return PTR_ERR(essiv_tfm);
+
+	err = crypto_shash_setkey(essiv_tfm, cc->key, cc->key_size);
+	if (err) {
+		ti->error = "Failed to set key for ESSIV cipher";
+		crypto_free_shash(essiv_tfm);
+		return err;
 	}
+
 	cc->iv_private = essiv_tfm;
 
 	return 0;
-
-bad:
-	if (hash_tfm && !IS_ERR(hash_tfm))
-		crypto_free_shash(hash_tfm);
-	kfree(salt);
-	return err;
 }
 
 static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv,
 			      struct dm_crypt_request *dmreq)
 {
-	struct crypto_cipher *essiv_tfm = cc->iv_private;
+	struct crypto_shash *essiv_tfm = cc->iv_private;
+	SHASH_DESC_ON_STACK(desc, essiv_tfm);
 
 	memset(iv, 0, cc->iv_size);
 	*(__le64 *)iv = cpu_to_le64(dmreq->iv_sector);
-	crypto_cipher_encrypt_one(essiv_tfm, iv, iv);
-
-	return 0;
+	desc->tfm = essiv_tfm;
+	return crypto_shash_digest(desc, iv, sizeof(__le64), iv);
 }
 
 static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
-- 
2.20.1