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Subject[PATCH v6 13/18] wireless/lib80211: Convert from ahash to shash
Date
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@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
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