[PATCH v2] crypto: caam: Drop leading zero from input buffer

[Fabio Estevam]

From: Fabio Estevam <fabio.este...@nxp.com>

imx6ul and imx7 report the following error:

caam_jr 2142000.jr1: 40000789: DECO: desc idx 7:
Protocol Size Error - A protocol has seen an error in size. When
running RSA, pdb size N < (size of F) when no formatting is used; or
pdb size N < (F + 11) when formatting is used.

------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at crypto/asymmetric_keys/public_key.c:148
public_key_verify_signature+0x27c/0x2b0

This error happens because the signature contains 257 bytes, including
a leading zero as the first element.

Fix the problem by stripping off the leading zero from input data
before feeding it to the CAAM accelerator.

Fixes: 8c419778ab57e497b5 ("crypto: caam - add support for RSA algorithm")
Cc: <sta...@vger.kernel.org>
Reported-by: Martin Townsend <mtownsend1...@gmail.com>
Signed-off-by: Fabio Estevam <fabio.este...@nxp.com>
---
Changes since v1:
- Use a temp pointer
- Assign len to req->src_len , so that more than one leading zero
can be taken into account

 drivers/crypto/caam/caampkc.c | 45 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 8 deletions(-)

diff --git a/drivers/crypto/caam/caampkc.c b/drivers/crypto/caam/caampkc.c
index 7a897209..5f3e627 100644
--- a/drivers/crypto/caam/caampkc.c
+++ b/drivers/crypto/caam/caampkc.c
@@ -166,6 +166,14 @@ static void rsa_priv_f3_done(struct device *dev, u32 
*desc, u32 err,
        akcipher_request_complete(req, err);
 }
 
+static void caam_rsa_drop_leading_zeros(const u8 **ptr, size_t *nbytes)
+{
+       while (!**ptr && *nbytes) {
+               (*ptr)++;
+               (*nbytes)--;
+       }
+}
+
 static struct rsa_edesc *rsa_edesc_alloc(struct akcipher_request *req,
                                         size_t desclen)
 {
@@ -178,7 +186,36 @@ static struct rsa_edesc *rsa_edesc_alloc(struct 
akcipher_request *req,
        int sgc;
        int sec4_sg_index, sec4_sg_len = 0, sec4_sg_bytes;
        int src_nents, dst_nents;
+       const u8 *temp;
+       void *buffer;
+       size_t len;
+
+       buffer = kzalloc(req->src_len, GFP_ATOMIC);
+       if (!buffer)
+               return ERR_PTR(-ENOMEM);
+
+       sg_copy_to_buffer(req->src, sg_nents(req->src),
+                         buffer, req->src_len);
+       temp = (u8 *)buffer;
+       len = req->src_len;
 
+       /*
+        * Check if the buffer contains leading zeros and if
+        * it does, drop the leading zeros
+        */
+       if (temp[0] == 0) {
+               caam_rsa_drop_leading_zeros(&temp, &len);
+               if (!temp) {
+                       kfree(buffer);
+                       return ERR_PTR(-ENOMEM);
+               }
+
+               req->src_len = len;
+               sg_copy_from_buffer(req->src, sg_nents(req->src),
+                                   (void *)temp, req->src_len);
+       }
+
+       kfree(buffer);
        src_nents = sg_nents_for_len(req->src, req->src_len);
        dst_nents = sg_nents_for_len(req->dst, req->dst_len);
 
@@ -683,14 +720,6 @@ static void caam_rsa_free_key(struct caam_rsa_key *key)
        memset(key, 0, sizeof(*key));
 }
 
-static void caam_rsa_drop_leading_zeros(const u8 **ptr, size_t *nbytes)
-{
-       while (!**ptr && *nbytes) {
-               (*ptr)++;
-               (*nbytes)--;
-       }
-}
-
 /**
  * caam_read_rsa_crt - Used for reading dP, dQ, qInv CRT members.
  * dP, dQ and qInv could decode to less than corresponding p, q length, as the
-- 
2.7.4