[PATCH v2 3/6] crypto: ccree: fix iv handling

[Gilad Ben-Yossef]

We were copying our last cipher block into the request for use as IV for
all modes of operations. Fix this by discerning the behaviour based on
the mode of operation used: copy ciphertext for CBC, update counter for
CTR.

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 | 111 +++++++++++++++++++++++++++++----------
 1 file changed, 84 insertions(+), 27 deletions(-)

diff --git a/drivers/crypto/ccree/cc_cipher.c b/drivers/crypto/ccree/cc_cipher.c
index d2810c1..958ced3 100644
--- a/drivers/crypto/ccree/cc_cipher.c
+++ b/drivers/crypto/ccree/cc_cipher.c
@@ -593,34 +593,82 @@ static void cc_setup_cipher_data(struct crypto_tfm *tfm,
 	}
 }
 
+/*
+ * Update a CTR-AES 128 bit counter
+ */
+static void cc_update_ctr(u8 *ctr, unsigned int increment)
+{
+	if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
+	    IS_ALIGNED((unsigned long)ctr, 8)) {
+
+		__be64 *high_be = (__be64 *)ctr;
+		__be64 *low_be = high_be + 1;
+		u64 orig_low = __be64_to_cpu(*low_be);
+		u64 new_low = orig_low + (u64)increment;
+
+		*low_be = __cpu_to_be64(new_low);
+
+		if (new_low < orig_low)
+			*high_be = __cpu_to_be64(__be64_to_cpu(*high_be) + 1);
+	} else {
+		u8 *pos = (ctr + AES_BLOCK_SIZE);
+		u8 val;
+		unsigned int size;
+
+		for (; increment; increment--)
+			for (size = AES_BLOCK_SIZE; size; size--) {
+				val = *--pos + 1;
+				*pos = val;
+				if (val)
+					break;
+			}
+	}
+}
+
 static void cc_cipher_complete(struct device *dev, void *cc_req, int err)
 {
 	struct skcipher_request *req = (struct skcipher_request *)cc_req;
 	struct scatterlist *dst = req->dst;
 	struct scatterlist *src = req->src;
 	struct cipher_req_ctx *req_ctx = skcipher_request_ctx(req);
-	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
-	unsigned int ivsize = crypto_skcipher_ivsize(tfm);
+	struct crypto_skcipher *sk_tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(sk_tfm);
+	struct cc_cipher_ctx *ctx_p = crypto_tfm_ctx(tfm);
+	unsigned int ivsize = crypto_skcipher_ivsize(sk_tfm);
+	unsigned int len;
 
-	cc_unmap_cipher_request(dev, req_ctx, ivsize, src, dst);
-	kzfree(req_ctx->iv);
+	switch (ctx_p->cipher_mode) {
+	case DRV_CIPHER_CBC:
+		/*
+		 * The crypto API expects us to set the req->iv to the last
+		 * ciphertext block. For encrypt, simply copy from the result.
+		 * For decrypt, we must copy from a saved buffer since this
+		 * could be an in-place decryption operation and the src is
+		 * lost by this point.
+		 */
+		if (req_ctx->gen_ctx.op_type == DRV_CRYPTO_DIRECTION_DECRYPT)  {
+			memcpy(req->iv, req_ctx->backup_info, ivsize);
+			kzfree(req_ctx->backup_info);
+		} else if (!err) {
+			len = req->cryptlen - ivsize;
+			scatterwalk_map_and_copy(req->iv, req->dst, len,
+						 ivsize, 0);
+		}
+		break;
 
-	/*
-	 * The crypto API expects us to set the req->iv to the last
-	 * ciphertext block. For encrypt, simply copy from the result.
-	 * For decrypt, we must copy from a saved buffer since this
-	 * could be an in-place decryption operation and the src is
-	 * lost by this point.
-	 */
-	if (req_ctx->gen_ctx.op_type == DRV_CRYPTO_DIRECTION_DECRYPT)  {
-		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);
+	case DRV_CIPHER_CTR:
+		/* Compute the counter of the last block */
+		len = ALIGN(req->cryptlen, AES_BLOCK_SIZE) / AES_BLOCK_SIZE;
+		cc_update_ctr((u8 *)req->iv, len);
+		break;
+
+	default:
+		break;
 	}
 
+	cc_unmap_cipher_request(dev, req_ctx, ivsize, src, dst);
+	kzfree(req_ctx->iv);
+
 	skcipher_request_complete(req, err);
 }
 
@@ -752,20 +800,29 @@ static int cc_cipher_encrypt(struct skcipher_request *req)
 static int cc_cipher_decrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *sk_tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(sk_tfm);
+	struct cc_cipher_ctx *ctx_p = crypto_tfm_ctx(tfm);
 	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);
-	if (!req_ctx->backup_info)
-		return -ENOMEM;
+	if (ctx_p->cipher_mode == DRV_CIPHER_CBC) {
+
+		/* Allocate and save the last IV sized bytes of the source,
+		 * which will be lost in case of in-place decryption.
+		 */
+		req_ctx->backup_info = kzalloc(ivsize, flags);
+		if (!req_ctx->backup_info)
+			return -ENOMEM;
+
+		len = req->cryptlen - ivsize;
+		scatterwalk_map_and_copy(req_ctx->backup_info, req->src, len,
+					 ivsize, 0);
+	} else {
+		req_ctx->backup_info = NULL;
+	}
 
-	scatterwalk_map_and_copy(req_ctx->backup_info, req->src,
-				 (req->cryptlen - ivsize), ivsize, 0);
 	req_ctx->is_giv = false;
 
 	return cc_cipher_process(req, DRV_CRYPTO_DIRECTION_DECRYPT);
-- 
2.7.4