crypto: atmel-aes - Add fallback to XTS software implementation

XTS is supported just for input lengths with data units of 128-bit blocks.
Add a fallback to software implementation when the last block is shorter
than 128 bits.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/atmel-aes.c b/drivers/crypto/atmel-aes.c
index 9ec007b..e74fcaa 100644 (file)
--- a/drivers/crypto/atmel-aes.c
+++ b/drivers/crypto/atmel-aes.c
@@ -143,6 +143,7 @@ struct atmel_aes_xts_ctx {
        struct atmel_aes_base_ctx       base;
 
        u32                     key2[AES_KEYSIZE_256 / sizeof(u32)];
+       struct crypto_skcipher *fallback_tfm;
 };
 
 #if IS_ENABLED(CONFIG_CRYPTO_DEV_ATMEL_AUTHENC)
@@ -155,6 +156,7 @@ struct atmel_aes_authenc_ctx {
 struct atmel_aes_reqctx {
        unsigned long           mode;
        u8                      lastc[AES_BLOCK_SIZE];
+       struct skcipher_request fallback_req;
 };
 
 #if IS_ENABLED(CONFIG_CRYPTO_DEV_ATMEL_AUTHENC)
@@ -1083,6 +1085,22 @@ static int atmel_aes_ctr_start(struct atmel_aes_dev *dd)
        return atmel_aes_ctr_transfer(dd);
 }
 
+static int atmel_aes_xts_fallback(struct skcipher_request *req, bool enc)
+{
+       struct atmel_aes_reqctx *rctx = skcipher_request_ctx(req);
+       struct atmel_aes_xts_ctx *ctx = crypto_skcipher_ctx(
+                       crypto_skcipher_reqtfm(req));
+
+       skcipher_request_set_tfm(&rctx->fallback_req, ctx->fallback_tfm);
+       skcipher_request_set_callback(&rctx->fallback_req, req->base.flags,
+                                     req->base.complete, req->base.data);
+       skcipher_request_set_crypt(&rctx->fallback_req, req->src, req->dst,
+                                  req->cryptlen, req->iv);
+
+       return enc ? crypto_skcipher_encrypt(&rctx->fallback_req) :
+                    crypto_skcipher_decrypt(&rctx->fallback_req);
+}
+
 static int atmel_aes_crypt(struct skcipher_request *req, unsigned long mode)
 {
        struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
@@ -1091,8 +1109,14 @@ static int atmel_aes_crypt(struct skcipher_request *req, unsigned long mode)
        struct atmel_aes_dev *dd;
        u32 opmode = mode & AES_FLAGS_OPMODE_MASK;
 
-       if (opmode == AES_FLAGS_XTS && req->cryptlen < XTS_BLOCK_SIZE)
-               return -EINVAL;
+       if (opmode == AES_FLAGS_XTS) {
+               if (req->cryptlen < XTS_BLOCK_SIZE)
+                       return -EINVAL;
+
+               if (!IS_ALIGNED(req->cryptlen, XTS_BLOCK_SIZE))
+                       return atmel_aes_xts_fallback(req,
+                                                     mode & AES_FLAGS_ENCRYPT);
+       }
 
        /*
         * ECB, CBC, CFB, OFB or CTR mode require the plaintext and ciphertext
@@ -1864,6 +1888,13 @@ static int atmel_aes_xts_setkey(struct crypto_skcipher *tfm, const u8 *key,
        if (err)
                return err;
 
+       crypto_skcipher_clear_flags(ctx->fallback_tfm, CRYPTO_TFM_REQ_MASK);
+       crypto_skcipher_set_flags(ctx->fallback_tfm, tfm->base.crt_flags &
+                                 CRYPTO_TFM_REQ_MASK);
+       err = crypto_skcipher_setkey(ctx->fallback_tfm, key, keylen);
+       if (err)
+               return err;
+
        memcpy(ctx->base.key, key, keylen/2);
        memcpy(ctx->key2, key + keylen/2, keylen/2);
        ctx->base.keylen = keylen/2;
@@ -1884,18 +1915,33 @@ static int atmel_aes_xts_decrypt(struct skcipher_request *req)
 static int atmel_aes_xts_init_tfm(struct crypto_skcipher *tfm)
 {
        struct atmel_aes_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
+       const char *tfm_name = crypto_tfm_alg_name(&tfm->base);
 
-       crypto_skcipher_set_reqsize(tfm, sizeof(struct atmel_aes_reqctx));
+       ctx->fallback_tfm = crypto_alloc_skcipher(tfm_name, 0,
+                                                 CRYPTO_ALG_NEED_FALLBACK);
+       if (IS_ERR(ctx->fallback_tfm))
+               return PTR_ERR(ctx->fallback_tfm);
+
+       crypto_skcipher_set_reqsize(tfm, sizeof(struct atmel_aes_reqctx) +
+                                   crypto_skcipher_reqsize(ctx->fallback_tfm));
        ctx->base.start = atmel_aes_xts_start;
 
        return 0;
 }
 
+static void atmel_aes_xts_exit_tfm(struct crypto_skcipher *tfm)
+{
+       struct atmel_aes_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+       crypto_free_skcipher(ctx->fallback_tfm);
+}
+
 static struct skcipher_alg aes_xts_alg = {
        .base.cra_name          = "xts(aes)",
        .base.cra_driver_name   = "atmel-xts-aes",
        .base.cra_blocksize     = AES_BLOCK_SIZE,
        .base.cra_ctxsize       = sizeof(struct atmel_aes_xts_ctx),
+       .base.cra_flags         = CRYPTO_ALG_NEED_FALLBACK,
 
        .min_keysize            = 2 * AES_MIN_KEY_SIZE,
        .max_keysize            = 2 * AES_MAX_KEY_SIZE,
@@ -1904,6 +1950,7 @@ static struct skcipher_alg aes_xts_alg = {
        .encrypt                = atmel_aes_xts_encrypt,
        .decrypt                = atmel_aes_xts_decrypt,
        .init                   = atmel_aes_xts_init_tfm,
+       .exit                   = atmel_aes_xts_exit_tfm,
 };
 
 #if IS_ENABLED(CONFIG_CRYPTO_DEV_ATMEL_AUTHENC)
@@ -2373,7 +2420,7 @@ static void atmel_aes_unregister_algs(struct atmel_aes_dev *dd)
 
 static void atmel_aes_crypto_alg_init(struct crypto_alg *alg)
 {
-       alg->cra_flags = CRYPTO_ALG_ASYNC;
+       alg->cra_flags |= CRYPTO_ALG_ASYNC;
        alg->cra_alignmask = 0xf;
        alg->cra_priority = ATMEL_AES_PRIORITY;
        alg->cra_module = THIS_MODULE;