Re: [BUGFIX PATCH] staging: ccree: save ciphertext for CTS IV

[Gilad Ben-Yossef]

On Wed, Aug 23, 2017 at 10:47 AM, Stephan Mueller  wrote:
> Am Mittwoch, 23. August 2017, 09:41:11 CEST schrieb Gilad Ben-Yossef:
>
> Hi Gilad,
>
>>
>>   if (areq) {
>> + /*
>> +  * The crypto API expects us to set the req->info 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->info, req_ctx->backup_info, ivsize);
>> + kfree(req_ctx->backup_info);
>> + } else {
>> + scatterwalk_map_and_copy(req->info, req->dst,
>> +  (req->nbytes - ivsize),
>> +  ivsize, 0);
>> + }
>> +
>>   ablkcipher_request_complete(areq, completion_error);
>>   return 0;
>>   }
>> @@ -858,7 +876,6 @@ static int ssi_ablkcipher_encrypt(struct
>> ablkcipher_request *req) struct blkcipher_req_ctx *req_ctx =
>> ablkcipher_request_ctx(req); unsigned int ivsize =
>> crypto_ablkcipher_ivsize(ablk_tfm);
>>
>> - req_ctx->backup_info = req->info;
>>   req_ctx->is_giv = false;
>>
>>   return ssi_blkcipher_process(tfm, req_ctx, req->dst, req->src,
>> req->nbytes, req->info, ivsize, (void *)req, DRV_CRYPTO_DIRECTION_ENCRYPT);
>> @@ -871,8 +888,18 @@ static int ssi_ablkcipher_decrypt(struct
>> ablkcipher_request *req) struct blkcipher_req_ctx *req_ctx =
>> ablkcipher_request_ctx(req); unsigned int ivsize =
>> crypto_ablkcipher_ivsize(ablk_tfm);
>>
>> - req_ctx->backup_info = req->info;
>> + /*
>> +  * 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, GFP_KERNEL);
>> + if (!req_ctx->backup_info)
>> + return -ENOMEM;
>
> Are you sure you do not add a memleak here? You seem to unconditionally
> allocate memory but conditionally free it.

You are right. I've missed freeing the memory on error code paths.
Thank you for catching that.
The code involved is badly need of a re-write but I wanted to get the
obvious bug fixed first.
I will send a revised patch

Thanks,
Gilad




-- 
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

Re: [BUGFIX PATCH] staging: ccree: save ciphertext for CTS IV

[Stephan Mueller]

Am Mittwoch, 23. August 2017, 09:41:11 CEST schrieb Gilad Ben-Yossef:

Hi Gilad,

> 
>   if (areq) {
> + /*
> +  * The crypto API expects us to set the req->info 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->info, req_ctx->backup_info, ivsize);
> + kfree(req_ctx->backup_info);
> + } else {
> + scatterwalk_map_and_copy(req->info, req->dst,
> +  (req->nbytes - ivsize),
> +  ivsize, 0);
> + }
> +
>   ablkcipher_request_complete(areq, completion_error);
>   return 0;
>   }
> @@ -858,7 +876,6 @@ static int ssi_ablkcipher_encrypt(struct
> ablkcipher_request *req) struct blkcipher_req_ctx *req_ctx =
> ablkcipher_request_ctx(req); unsigned int ivsize =
> crypto_ablkcipher_ivsize(ablk_tfm);
> 
> - req_ctx->backup_info = req->info;
>   req_ctx->is_giv = false;
> 
>   return ssi_blkcipher_process(tfm, req_ctx, req->dst, req->src,
> req->nbytes, req->info, ivsize, (void *)req, DRV_CRYPTO_DIRECTION_ENCRYPT);
> @@ -871,8 +888,18 @@ static int ssi_ablkcipher_decrypt(struct
> ablkcipher_request *req) struct blkcipher_req_ctx *req_ctx =
> ablkcipher_request_ctx(req); unsigned int ivsize =
> crypto_ablkcipher_ivsize(ablk_tfm);
> 
> - req_ctx->backup_info = req->info;
> + /*
> +  * 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, GFP_KERNEL);
> + if (!req_ctx->backup_info)
> + return -ENOMEM;

Are you sure you do not add a memleak here? You seem to unconditionally 
allocate memory but conditionally free it.

Ciao
Stephan

[BUGFIX PATCH] staging: ccree: save ciphertext for CTS IV

[Gilad Ben-Yossef]

The crypto API requires saving the last blocks of ciphertext
in req->info for use as IV for CTS mode. The ccree driver
was not doing this. This patch fixes that.

The bug was manifested with cts(cbc(aes)) mode in tcrypt tests.

Fixes: 302ef8ebb4b2 ("Add CryptoCell skcipher support")
Signed-off-by: Gilad Ben-Yossef 
---
 drivers/staging/ccree/ssi_cipher.c | 31 +--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/ccree/ssi_cipher.c 
b/drivers/staging/ccree/ssi_cipher.c
index af9afea..01011a2 100644
--- a/drivers/staging/ccree/ssi_cipher.c
+++ b/drivers/staging/ccree/ssi_cipher.c
@@ -24,6 +24,7 @@
 #include 
 #include 
 #include 
+#include 
 
 #include "ssi_config.h"
 #include "ssi_driver.h"
@@ -697,6 +698,7 @@ static int ssi_blkcipher_complete(struct device *dev,
 {
int completion_error = 0;
u32 inflight_counter;
+   struct ablkcipher_request *req = (struct ablkcipher_request *)areq;
 
ssi_buffer_mgr_unmap_blkcipher_request(dev, req_ctx, ivsize, src, dst);
 
@@ -707,6 +709,22 @@ static int ssi_blkcipher_complete(struct device *dev,
ctx_p->drvdata->inflight_counter--;
 
if (areq) {
+   /*
+* The crypto API expects us to set the req->info 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->info, req_ctx->backup_info, ivsize);
+   kfree(req_ctx->backup_info);
+   } else {
+   scatterwalk_map_and_copy(req->info, req->dst,
+(req->nbytes - ivsize),
+ivsize, 0);
+   }
+
ablkcipher_request_complete(areq, completion_error);
return 0;
}
@@ -858,7 +876,6 @@ static int ssi_ablkcipher_encrypt(struct ablkcipher_request 
*req)
struct blkcipher_req_ctx *req_ctx = ablkcipher_request_ctx(req);
unsigned int ivsize = crypto_ablkcipher_ivsize(ablk_tfm);
 
-   req_ctx->backup_info = req->info;
req_ctx->is_giv = false;
 
return ssi_blkcipher_process(tfm, req_ctx, req->dst, req->src, 
req->nbytes, req->info, ivsize, (void *)req, DRV_CRYPTO_DIRECTION_ENCRYPT);
@@ -871,8 +888,18 @@ static int ssi_ablkcipher_decrypt(struct 
ablkcipher_request *req)
struct blkcipher_req_ctx *req_ctx = ablkcipher_request_ctx(req);
unsigned int ivsize = crypto_ablkcipher_ivsize(ablk_tfm);
 
-   req_ctx->backup_info = req->info;
+   /*
+* 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, GFP_KERNEL);
+   if (!req_ctx->backup_info)
+   return -ENOMEM;
+
+   scatterwalk_map_and_copy(req_ctx->backup_info, req->src,
+(req->nbytes - ivsize), ivsize, 0);
req_ctx->is_giv = false;
+
return ssi_blkcipher_process(tfm, req_ctx, req->dst, req->src, 
req->nbytes, req->info, ivsize, (void *)req, DRV_CRYPTO_DIRECTION_DECRYPT);
 }
 
-- 
2.1.4