linux-kernel - Re: [PATCH v2 6/7] crypto: omap-aes: Add support for GCM mode

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Date:	Wed, 8 Jul 2015 12:18:38 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Lokesh Vutla <lokeshvutla@...com>
Cc:	linux-crypto@...r.kernel.org, davem@...emloft.net,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	t-kristo@...com, nsekhar@...com
Subject: Re: [PATCH v2 6/7] crypto: omap-aes: Add support for GCM mode

On Tue, Jul 07, 2015 at 09:01:48PM +0530, Lokesh Vutla wrote:
>
> +static int omap_aes_gcm_copy_buffers(struct omap_aes_dev *dd,
> +				     struct aead_request *req)
> +{
> +	void *buf_in;
> +	int pages, alen, clen, cryptlen, nsg;
> +	struct crypto_aead *aead = crypto_aead_reqtfm(req);
> +	unsigned int authlen = crypto_aead_authsize(aead);
> +	u32 dec = !(dd->flags & FLAGS_ENCRYPT);
> +	struct scatterlist *input, *assoc, tmp[2];
> +
> +	alen = ALIGN(req->assoclen, AES_BLOCK_SIZE);
> +	cryptlen = req->cryptlen - (dec * authlen);
> +	clen = ALIGN(cryptlen, AES_BLOCK_SIZE);
> +
> +	dd->sgs_copied = 0;
> +
> +	nsg = !!(req->assoclen && req->cryptlen);
> +
> +	assoc = &req->src[0];
> +	sg_init_table(dd->in_sgl, nsg + 1);
> +	if (req->assoclen) {
> +		if (omap_aes_check_aligned(assoc, req->assoclen)) {
> +			dd->sgs_copied |= AES_ASSOC_DATA_COPIED;
> +			pages = get_order(alen);
> +			buf_in = (void *)__get_free_pages(GFP_ATOMIC, pages);
> +			if (!buf_in) {
> +				pr_err("Couldn't allocate for unaligncases.\n");
> +				return -1;
> +			}
> +
> +			scatterwalk_map_and_copy(buf_in, assoc, 0,
> +						 req->assoclen, 0);
> +			memset(buf_in + req->assoclen, 0, alen - req->assoclen);
> +		} else {
> +			buf_in = sg_virt(req->assoc);

req->assoc is now obsolete. Did you test this code?

> +static int do_encrypt_iv(struct aead_request *req, u32 *tag)
> +{
> +	struct scatterlist iv_sg;
> +	struct ablkcipher_request *ablk_req;
> +	struct crypto_ablkcipher *tfm;
> +	struct tcrypt_result result;
> +	struct omap_aes_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
> +	int ret = 0;
> +
> +	tfm = crypto_alloc_ablkcipher("ctr(aes)", 0, 0);

Ugh, you cannot allocate crypto transforms in the data path.  You
should allocate it in init instead.  Also using ctr(aes) is overkill.
Just use aes and do the xor by hand.

> +static int omap_aes_gcm_crypt(struct aead_request *req, unsigned long mode)
> +{
> +	struct omap_aes_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
> +	struct omap_aes_reqctx *rctx = aead_request_ctx(req);
> +	struct crypto_aead *aead = crypto_aead_reqtfm(req);
> +	unsigned int authlen = crypto_aead_authsize(aead);
> +	struct omap_aes_dev *dd;
> +	__be32 counter = cpu_to_be32(1);
> +	int err;
> +
> +	memset(ctx->auth_tag, 0, sizeof(ctx->auth_tag));

The ctx is shared memory and you must not write to it as multiple
requests can be called on the same tfm.  Use rctx instead.

> +	memcpy(req->iv + 12, &counter, 4);

The IV is only 12 bytes long so you're corrupting memory here.
You should use rctx here too.

> +	if (req->assoclen + req->cryptlen == 0) {
> +		scatterwalk_map_and_copy(ctx->auth_tag, req->dst, 0, authlen,
> +					 1);
> +		return 0;
> +	}

How can this be right? Did you enable the selftest?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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