[PATCH v2 13/13] crypto: mediatek - use AES library for GCM key derivation

[Ard Biesheuvel <ardb@kernel.org>]

The Mediatek accelerator driver calls into a dynamically allocated
skcipher of the ctr(aes) variety to perform GCM key derivation, which
involves AES encryption of a single block consisting of NUL bytes.

There is no point in using the skcipher API for this, so use the AES
library interface instead.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/crypto/Kconfig            |  3 +-
 drivers/crypto/mediatek/mtk-aes.c | 63 +++-----------------
 2 files changed, 9 insertions(+), 57 deletions(-)

diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 802b9ada4e9e..c8c3ebb248f8 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -756,10 +756,9 @@ config CRYPTO_DEV_ZYNQMP_AES
 config CRYPTO_DEV_MEDIATEK
 	tristate "MediaTek's EIP97 Cryptographic Engine driver"
 	depends on (ARM && ARCH_MEDIATEK) || COMPILE_TEST
-	select CRYPTO_AES
+	select CRYPTO_LIB_AES
 	select CRYPTO_AEAD
 	select CRYPTO_SKCIPHER
-	select CRYPTO_CTR
 	select CRYPTO_SHA1
 	select CRYPTO_SHA256
 	select CRYPTO_SHA512
diff --git a/drivers/crypto/mediatek/mtk-aes.c b/drivers/crypto/mediatek/mtk-aes.c
index 78d660d963e2..4ad3571ab6af 100644
--- a/drivers/crypto/mediatek/mtk-aes.c
+++ b/drivers/crypto/mediatek/mtk-aes.c
@@ -137,8 +137,6 @@ struct mtk_aes_gcm_ctx {
 
 	u32 authsize;
 	size_t textlen;
-
-	struct crypto_skcipher *ctr;
 };
 
 struct mtk_aes_drv {
@@ -996,17 +994,8 @@ static int mtk_aes_gcm_setkey(struct crypto_aead *aead, const u8 *key,
 			      u32 keylen)
 {
 	struct mtk_aes_base_ctx *ctx = crypto_aead_ctx(aead);
-	struct mtk_aes_gcm_ctx *gctx = mtk_aes_gcm_ctx_cast(ctx);
-	struct crypto_skcipher *ctr = gctx->ctr;
-	struct {
-		u32 hash[4];
-		u8 iv[8];
-
-		struct crypto_wait wait;
-
-		struct scatterlist sg[1];
-		struct skcipher_request req;
-	} *data;
+	u8 hash[AES_BLOCK_SIZE] __aligned(4) = {};
+	struct crypto_aes_ctx aes_ctx;
 	int err;
 
 	switch (keylen) {
@@ -1026,39 +1015,18 @@ static int mtk_aes_gcm_setkey(struct crypto_aead *aead, const u8 *key,
 
 	ctx->keylen = SIZE_IN_WORDS(keylen);
 
-	/* Same as crypto_gcm_setkey() from crypto/gcm.c */
-	crypto_skcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
-	crypto_skcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
-				  CRYPTO_TFM_REQ_MASK);
-	err = crypto_skcipher_setkey(ctr, key, keylen);
+	err = aes_expandkey(&aes_ctx, key, keylen);
 	if (err)
 		return err;
 
-	data = kzalloc(sizeof(*data) + crypto_skcipher_reqsize(ctr),
-		       GFP_KERNEL);
-	if (!data)
-		return -ENOMEM;
-
-	crypto_init_wait(&data->wait);
-	sg_init_one(data->sg, &data->hash, AES_BLOCK_SIZE);
-	skcipher_request_set_tfm(&data->req, ctr);
-	skcipher_request_set_callback(&data->req, CRYPTO_TFM_REQ_MAY_SLEEP |
-				      CRYPTO_TFM_REQ_MAY_BACKLOG,
-				      crypto_req_done, &data->wait);
-	skcipher_request_set_crypt(&data->req, data->sg, data->sg,
-				   AES_BLOCK_SIZE, data->iv);
-
-	err = crypto_wait_req(crypto_skcipher_encrypt(&data->req),
-			      &data->wait);
-	if (err)
-		goto out;
+	aes_encrypt(&aes_ctx, hash, hash);
+	memzero_explicit(&aes_ctx, sizeof(aes_ctx));
 
 	mtk_aes_write_state_le(ctx->key, (const u32 *)key, keylen);
-	mtk_aes_write_state_be(ctx->key + ctx->keylen, data->hash,
+	mtk_aes_write_state_be(ctx->key + ctx->keylen, (const u32 *)hash,
 			       AES_BLOCK_SIZE);
-out:
-	kzfree(data);
-	return err;
+
+	return 0;
 }
 
 static int mtk_aes_gcm_setauthsize(struct crypto_aead *aead,
@@ -1095,32 +1063,17 @@ static int mtk_aes_gcm_init(struct crypto_aead *aead)
 {
 	struct mtk_aes_gcm_ctx *ctx = crypto_aead_ctx(aead);
 
-	ctx->ctr = crypto_alloc_skcipher("ctr(aes)", 0,
-					 CRYPTO_ALG_ASYNC);
-	if (IS_ERR(ctx->ctr)) {
-		pr_err("Error allocating ctr(aes)\n");
-		return PTR_ERR(ctx->ctr);
-	}
-
 	crypto_aead_set_reqsize(aead, sizeof(struct mtk_aes_reqctx));
 	ctx->base.start = mtk_aes_gcm_start;
 	return 0;
 }
 
-static void mtk_aes_gcm_exit(struct crypto_aead *aead)
-{
-	struct mtk_aes_gcm_ctx *ctx = crypto_aead_ctx(aead);
-
-	crypto_free_skcipher(ctx->ctr);
-}
-
 static struct aead_alg aes_gcm_alg = {
 	.setkey		= mtk_aes_gcm_setkey,
 	.setauthsize	= mtk_aes_gcm_setauthsize,
 	.encrypt	= mtk_aes_gcm_encrypt,
 	.decrypt	= mtk_aes_gcm_decrypt,
 	.init		= mtk_aes_gcm_init,
-	.exit		= mtk_aes_gcm_exit,
 	.ivsize		= GCM_AES_IV_SIZE,
 	.maxauthsize	= AES_BLOCK_SIZE,
 
-- 
2.27.0