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.
CC: stable@vger.kernel.org Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support") Reported by: Hadar Gat hadar.gat@arm.com Signed-off-by: Gilad Ben-Yossef gilad@benyossef.com --- 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);
Hi,
On Thu, Jun 7, 2018 at 11:58 AM, Gilad Ben-Yossef gilad@benyossef.com 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@vger.kernel.org Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support") Reported by: Hadar Gat hadar.gat@arm.com Signed-off-by: Gilad Ben-Yossef gilad@benyossef.com
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
On Thu, Jun 7, 2018 at 2:32 PM, Gilad Ben-Yossef gilad@benyossef.com wrote:
Hi,
On Thu, Jun 7, 2018 at 11:58 AM, Gilad Ben-Yossef gilad@benyossef.com 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.
Hi Gilad,
Requirement to copy IV back is different for various mode. You can check software template(cbc, ctr,...) for reference. Basic idea is Update IV such that user can use the same context to continue encryption.
e.g CBC mode uses last encrypted block as IV for current block. That why we have to copy last 16 byte to req->info
Note : For in-place decryption we save the last block(IV for next) in local buffer to avoid getting written by Plaintext.
for ctr mode: driver should increment counter(last 4 bytes of IV) based to no of block( 1 block implies 1 counter increment) processed
You can use following kcapi command to compare the results with sw crypto. "-s" switch will use the same context for "-d" No. of iterations
./kcapi -x 1 -e -s -d 4 -c "cbc(aes)" -k 8d7dd9b0170ce0b5f2f8e1aa768e01e91da8bfc67fd486d081b28254c99eb423 -i 7fbc02ebf5b93322329df9bfccb635af -p 48981da18e4bb9ef7e2e3162d16b1910
Any feedback is apreciated.
Thanks! Gilad
CC: stable@vger.kernel.org Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support") Reported by: Hadar Gat hadar.gat@arm.com Signed-off-by: Gilad Ben-Yossef gilad@benyossef.com
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);
Copy of last block is required for CBC mode only and CBC input buffer is always in multiple of 16(Block size). Above change not required for CBC and will not work with mode like ctr.
} 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
On Thu, Jun 07, 2018 at 12:02:04PM +0300, Gilad Ben-Yossef wrote:
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?
Which algorithm is this? In general we disallow requests which are not a multiple of a block for block ciphers. Obviously this doesn't apply to stream ciphers such as ctr(aes), but in that case it doesn't really matter as you cannot chain such a request.
Cheers,
linux-stable-mirror@lists.linaro.org
-
Gilad Ben-Yossef -
Harsh Jain -
Herbert Xu