[PATCH] crypto: atmel-aes - properly set IV after {en,de}crypt

[Romain Izard]

Certain cipher modes like CTS expect the IV (req->info) of
ablkcipher_request (or equivalently req->iv of skcipher_request) to
contain the last ciphertext block when the {en,de}crypt operation is done.

Fix this issue for the Atmel AES hardware engine. The tcrypt test
case for cts(cbc(aes)) is now correctly passed.

To handle the case of in-place decryption, copy the ciphertext in an
intermediate buffer before decryption.

Signed-off-by: Romain Izard <romain.izard....@gmail.com>
---
 drivers/crypto/atmel-aes.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/crypto/atmel-aes.c b/drivers/crypto/atmel-aes.c
index 29e20c37f3a6..f22300babb45 100644
--- a/drivers/crypto/atmel-aes.c
+++ b/drivers/crypto/atmel-aes.c
@@ -156,6 +156,7 @@ struct atmel_aes_authenc_ctx {
 
 struct atmel_aes_reqctx {
        unsigned long           mode;
+       u8                      *backup_info;
 };
 
 #ifdef CONFIG_CRYPTO_DEV_ATMEL_AUTHENC
@@ -496,6 +497,12 @@ static void atmel_aes_authenc_complete(struct 
atmel_aes_dev *dd, int err);
 
 static inline int atmel_aes_complete(struct atmel_aes_dev *dd, int err)
 {
+       struct ablkcipher_request *req = ablkcipher_request_cast(dd->areq);
+       struct crypto_ablkcipher *ablkcipher = crypto_ablkcipher_reqtfm(req);
+       struct atmel_aes_reqctx *rctx = ablkcipher_request_ctx(req);
+       int ivsize = crypto_ablkcipher_ivsize(ablkcipher);
+       bool enc = atmel_aes_is_encrypt(dd);
+
 #ifdef CONFIG_CRYPTO_DEV_ATMEL_AUTHENC
        atmel_aes_authenc_complete(dd, err);
 #endif
@@ -503,6 +510,15 @@ static inline int atmel_aes_complete(struct atmel_aes_dev 
*dd, int err)
        clk_disable(dd->iclk);
        dd->flags &= ~AES_FLAGS_BUSY;
 
+       if (enc) {
+               scatterwalk_map_and_copy(req->info, req->dst,
+                                        req->nbytes - ivsize, ivsize, 0);
+       } else if (rctx->backup_info) {
+               memcpy(req->info, rctx->backup_info, ivsize);
+               kfree(rctx->backup_info);
+               rctx->backup_info = NULL;
+       }
+
        if (dd->is_async)
                dd->areq->complete(dd->areq, err);
 
@@ -959,13 +975,25 @@ static int atmel_aes_transfer_complete(struct 
atmel_aes_dev *dd)
 static int atmel_aes_start(struct atmel_aes_dev *dd)
 {
        struct ablkcipher_request *req = ablkcipher_request_cast(dd->areq);
+       struct crypto_ablkcipher *ablkcipher = crypto_ablkcipher_reqtfm(req);
        struct atmel_aes_reqctx *rctx = ablkcipher_request_ctx(req);
+       int ivsize = crypto_ablkcipher_ivsize(ablkcipher);
+       bool enc = atmel_aes_is_encrypt(dd);
        bool use_dma = (req->nbytes >= ATMEL_AES_DMA_THRESHOLD ||
                        dd->ctx->block_size != AES_BLOCK_SIZE);
        int err;
 
        atmel_aes_set_mode(dd, rctx);
 
+       if (!enc) {
+               rctx->backup_info = kzalloc(ivsize, GFP_KERNEL);
+               if (rctx->backup_info == NULL)
+                       return atmel_aes_complete(dd, -ENOMEM);
+
+               scatterwalk_map_and_copy(rctx->backup_info, req->src,
+                                (req->nbytes - ivsize), ivsize, 0);
+       }
+
        err = atmel_aes_hw_init(dd);
        if (err)
                return atmel_aes_complete(dd, err);
-- 
2.11.0