[Drbd-dev] [PATCH v6 13/18] wireless/lib80211: Convert from ahash to shash

[Kees Cook]

In preparing to remove all stack VLA usage from the kernel[1], this
removes the discouraged use of AHASH_REQUEST_ON_STACK in favor of
the smaller SHASH_DESC_ON_STACK by converting from ahash-wrapped-shash
to direct shash. By removing a layer of indirection this both improves
performance and reduces stack usage. The stack allocation will be made
a fixed size in a later patch to the crypto subsystem.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook at chromium.org>
---
 net/wireless/lib80211_crypt_tkip.c | 58 +++++++++++++++---------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/net/wireless/lib80211_crypt_tkip.c b/net/wireless/lib80211_crypt_tkip.c
index ba0a1f398ce5..21040aba3a81 100644
--- a/net/wireless/lib80211_crypt_tkip.c
+++ b/net/wireless/lib80211_crypt_tkip.c
@@ -65,9 +65,9 @@ struct lib80211_tkip_data {
 	int key_idx;
 
 	struct crypto_skcipher *rx_tfm_arc4;
-	struct crypto_ahash *rx_tfm_michael;
+	struct crypto_shash *rx_tfm_michael;
 	struct crypto_skcipher *tx_tfm_arc4;
-	struct crypto_ahash *tx_tfm_michael;
+	struct crypto_shash *tx_tfm_michael;
 
 	/* scratch buffers for virt_to_page() (crypto API) */
 	u8 rx_hdr[16], tx_hdr[16];
@@ -106,8 +106,7 @@ static void *lib80211_tkip_init(int key_idx)
 		goto fail;
 	}
 
-	priv->tx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
-						  CRYPTO_ALG_ASYNC);
+	priv->tx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
 	if (IS_ERR(priv->tx_tfm_michael)) {
 		priv->tx_tfm_michael = NULL;
 		goto fail;
@@ -120,8 +119,7 @@ static void *lib80211_tkip_init(int key_idx)
 		goto fail;
 	}
 
-	priv->rx_tfm_michael = crypto_alloc_ahash("michael_mic", 0,
-						  CRYPTO_ALG_ASYNC);
+	priv->rx_tfm_michael = crypto_alloc_shash("michael_mic", 0, 0);
 	if (IS_ERR(priv->rx_tfm_michael)) {
 		priv->rx_tfm_michael = NULL;
 		goto fail;
@@ -131,9 +129,9 @@ static void *lib80211_tkip_init(int key_idx)
 
       fail:
 	if (priv) {
-		crypto_free_ahash(priv->tx_tfm_michael);
+		crypto_free_shash(priv->tx_tfm_michael);
 		crypto_free_skcipher(priv->tx_tfm_arc4);
-		crypto_free_ahash(priv->rx_tfm_michael);
+		crypto_free_shash(priv->rx_tfm_michael);
 		crypto_free_skcipher(priv->rx_tfm_arc4);
 		kfree(priv);
 	}
@@ -145,9 +143,9 @@ static void lib80211_tkip_deinit(void *priv)
 {
 	struct lib80211_tkip_data *_priv = priv;
 	if (_priv) {
-		crypto_free_ahash(_priv->tx_tfm_michael);
+		crypto_free_shash(_priv->tx_tfm_michael);
 		crypto_free_skcipher(_priv->tx_tfm_arc4);
-		crypto_free_ahash(_priv->rx_tfm_michael);
+		crypto_free_shash(_priv->rx_tfm_michael);
 		crypto_free_skcipher(_priv->rx_tfm_arc4);
 	}
 	kfree(priv);
@@ -510,29 +508,31 @@ static int lib80211_tkip_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 	return keyidx;
 }
 
-static int michael_mic(struct crypto_ahash *tfm_michael, u8 * key, u8 * hdr,
-		       u8 * data, size_t data_len, u8 * mic)
+static int michael_mic(struct crypto_shash *tfm_michael, u8 *key, u8 *hdr,
+		       u8 *data, size_t data_len, u8 *mic)
 {
-	AHASH_REQUEST_ON_STACK(req, tfm_michael);
-	struct scatterlist sg[2];
+	SHASH_DESC_ON_STACK(desc, tfm_michael);
 	int err;
 
-	if (tfm_michael == NULL) {
-		pr_warn("%s(): tfm_michael == NULL\n", __func__);
-		return -1;
-	}
-	sg_init_table(sg, 2);
-	sg_set_buf(&sg[0], hdr, 16);
-	sg_set_buf(&sg[1], data, data_len);
+	desc->tfm = tfm_michael;
+	desc->flags = 0;
 
-	if (crypto_ahash_setkey(tfm_michael, key, 8))
+	if (crypto_shash_setkey(tfm_michael, key, 8))
 		return -1;
 
-	ahash_request_set_tfm(req, tfm_michael);
-	ahash_request_set_callback(req, 0, NULL, NULL);
-	ahash_request_set_crypt(req, sg, mic, data_len + 16);
-	err = crypto_ahash_digest(req);
-	ahash_request_zero(req);
+	err = crypto_shash_init(desc);
+	if (err)
+		goto out;
+	err = crypto_shash_update(desc, hdr, 16);
+	if (err)
+		goto out;
+	err = crypto_shash_update(desc, data, data_len);
+	if (err)
+		goto out;
+	err = crypto_shash_final(desc, mic);
+
+out:
+	shash_desc_zero(desc);
 	return err;
 }
 
@@ -654,9 +654,9 @@ static int lib80211_tkip_set_key(void *key, int len, u8 * seq, void *priv)
 {
 	struct lib80211_tkip_data *tkey = priv;
 	int keyidx;
-	struct crypto_ahash *tfm = tkey->tx_tfm_michael;
+	struct crypto_shash *tfm = tkey->tx_tfm_michael;
 	struct crypto_skcipher *tfm2 = tkey->tx_tfm_arc4;
-	struct crypto_ahash *tfm3 = tkey->rx_tfm_michael;
+	struct crypto_shash *tfm3 = tkey->rx_tfm_michael;
 	struct crypto_skcipher *tfm4 = tkey->rx_tfm_arc4;
 
 	keyidx = tkey->key_idx;
-- 
2.17.1