Hi,
On Thu, Jun 7, 2018 at 11:58 AM, Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> wrote:
> We are copying our last cipher block into the request for use as IV as
> required by the Crypto API but we failed to handle correctly the case the
> buffer we are working on is smaller than a block. Fix it by calculating
> how much we need to copy based on buffer size.
>
I'd be really happy to get a review on this patch - not so much what
it is doing but
rather the rational behind it - how is a tfm provider supposed to
handle copying the
last block of ciphertext into the request structure if the ciphertext
size is less than a
block?
I opted for simply copying whatever ciphertext was available and
zeroing the rest
but frankly I'm not sure this is the right thing.
Any feedback is apreciated.
Thanks!
Gilad
> CC: stable@xxxxxxxxxxxxxxx
> Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support")
> Reported by: Hadar Gat <hadar.gat@xxxxxxx>
> Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
> ---
> drivers/crypto/ccree/cc_cipher.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/crypto/ccree/cc_cipher.c b/drivers/crypto/ccree/cc_cipher.c
> index d2810c1..a07547f 100644
> --- a/drivers/crypto/ccree/cc_cipher.c
> +++ b/drivers/crypto/ccree/cc_cipher.c
> @@ -616,9 +616,18 @@ static void cc_cipher_complete(struct device *dev, void *cc_req, int err)
> memcpy(req->iv, req_ctx->backup_info, ivsize);
> kzfree(req_ctx->backup_info);
> } else if (!err) {
> - scatterwalk_map_and_copy(req->iv, req->dst,
> - (req->cryptlen - ivsize),
> - ivsize, 0);
> + unsigned int len;
> +
> + if (req->cryptlen > ivsize) {
> + len = req->cryptlen - ivsize;
> + } else {
> + memset(req->iv, 0, ivsize);
> + len = 0;
> + ivsize = req->cryptlen;
> +
> + }
> +
> + scatterwalk_map_and_copy(req->iv, req->dst, len, ivsize, 0);
> }
>
> skcipher_request_complete(req, err);
> @@ -755,17 +764,26 @@ static int cc_cipher_decrypt(struct skcipher_request *req)
> struct cipher_req_ctx *req_ctx = skcipher_request_ctx(req);
> unsigned int ivsize = crypto_skcipher_ivsize(sk_tfm);
> gfp_t flags = cc_gfp_flags(&req->base);
> + unsigned int len;
>
> /*
> * Allocate and save the last IV sized bytes of the source, which will
> * be lost in case of in-place decryption and might be needed for CTS.
> */
> - req_ctx->backup_info = kmalloc(ivsize, flags);
> + req_ctx->backup_info = kzalloc(ivsize, flags);
> if (!req_ctx->backup_info)
> return -ENOMEM;
>
> - scatterwalk_map_and_copy(req_ctx->backup_info, req->src,
> - (req->cryptlen - ivsize), ivsize, 0);
> +
> + if (req->cryptlen > ivsize) {
> + len = req->cryptlen - ivsize;
> + } else {
> + len = 0;
> + ivsize = req->cryptlen;
> + }
> +
> + scatterwalk_map_and_copy(req_ctx->backup_info, req->src, len, ivsize,
> + 0);
> req_ctx->is_giv = false;
>
> return cc_cipher_process(req, DRV_CRYPTO_DIRECTION_DECRYPT);
> --
> 2.7.4
>
--
Gilad Ben-Yossef
Chief Coffee Drinker
"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
-- Jean-Baptiste Queru
