Re: [PATCH 3/3] crypto: ccp - protect RSA implementation from too large input data

[Gary R Hook]

On 02/24/2018 10:03 AM, Maciej S. Szmigiero wrote:

CCP RSA implementation uses a hardware input buffer which size depends only
on the current RSA key length. Key modulus and a message to be processed
is then copied to this buffer based on their own lengths.

Since the price for providing too long input data is a buffer overflow and
there already has been a case when this has happened let's better reject
such oversized input data and log an error message in this case so we know
what is going on.

Signed-off-by: Maciej S. Szmigiero 
---
  drivers/crypto/ccp/ccp-ops.c | 24 
  1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
index 406b95329b3d..517aeee30abf 100644
--- a/drivers/crypto/ccp/ccp-ops.c
+++ b/drivers/crypto/ccp/ccp-ops.c
@@ -1770,10 +1770,6 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, 
struct ccp_cmd *cmd)
if (!rsa->exp || !rsa->mod || !rsa->src || !rsa->dst)
return -EINVAL;
  
-	memset(, 0, sizeof(op));

-   op.cmd_q = cmd_q;
-   op.jobid = CCP_NEW_JOBID(cmd_q->ccp);
-
/* The RSA modulus must precede the message being acted upon, so
 * it must be copied to a DMA area where the message and the
 * modulus can be concatenated.  Therefore the input buffer
@@ -1785,6 +1781,26 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, 
struct ccp_cmd *cmd)
o_len = 32 * ((rsa->key_size + 255) / 256);
i_len = o_len * 2;
  
+	if (rsa->mod_len > o_len) {

+   dev_err(cmd_q->ccp->dev,
+   "RSA modulus of %u bytes too large for key size of %u 
bits\n",
+   (unsigned int)rsa->mod_len,
+   (unsigned int)rsa->key_size);
+   return -EINVAL;
+   }
+
+   if (rsa->src_len > o_len) {
+   dev_err(cmd_q->ccp->dev,
+   "RSA data of %u bytes too large for key size of %u 
bits\n",
+   (unsigned int)rsa->src_len,
+   (unsigned int)rsa->key_size);
+   return -EINVAL;
+   }


We've talked about this, and we believe that a more central fix is 
warranted. I intend to post another patch tomorrow that should address

this problem.


+
+   memset(, 0, sizeof(op));
+   op.cmd_q = cmd_q;
+   op.jobid = CCP_NEW_JOBID(cmd_q->ccp);
+
sb_count = 0;
if (cmd_q->ccp->vdata->version < CCP_VERSION(5, 0)) {
/* sb_count is the number of storage block slots required

[PATCH 3/3] crypto: ccp - protect RSA implementation from too large input data

[Maciej S. Szmigiero]

CCP RSA implementation uses a hardware input buffer which size depends only
on the current RSA key length. Key modulus and a message to be processed
is then copied to this buffer based on their own lengths.

Since the price for providing too long input data is a buffer overflow and
there already has been a case when this has happened let's better reject
such oversized input data and log an error message in this case so we know
what is going on.

Signed-off-by: Maciej S. Szmigiero 
---
 drivers/crypto/ccp/ccp-ops.c | 24 
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/ccp/ccp-ops.c b/drivers/crypto/ccp/ccp-ops.c
index 406b95329b3d..517aeee30abf 100644
--- a/drivers/crypto/ccp/ccp-ops.c
+++ b/drivers/crypto/ccp/ccp-ops.c
@@ -1770,10 +1770,6 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, 
struct ccp_cmd *cmd)
if (!rsa->exp || !rsa->mod || !rsa->src || !rsa->dst)
return -EINVAL;
 
-   memset(, 0, sizeof(op));
-   op.cmd_q = cmd_q;
-   op.jobid = CCP_NEW_JOBID(cmd_q->ccp);
-
/* The RSA modulus must precede the message being acted upon, so
 * it must be copied to a DMA area where the message and the
 * modulus can be concatenated.  Therefore the input buffer
@@ -1785,6 +1781,26 @@ static int ccp_run_rsa_cmd(struct ccp_cmd_queue *cmd_q, 
struct ccp_cmd *cmd)
o_len = 32 * ((rsa->key_size + 255) / 256);
i_len = o_len * 2;
 
+   if (rsa->mod_len > o_len) {
+   dev_err(cmd_q->ccp->dev,
+   "RSA modulus of %u bytes too large for key size of %u 
bits\n",
+   (unsigned int)rsa->mod_len,
+   (unsigned int)rsa->key_size);
+   return -EINVAL;
+   }
+
+   if (rsa->src_len > o_len) {
+   dev_err(cmd_q->ccp->dev,
+   "RSA data of %u bytes too large for key size of %u 
bits\n",
+   (unsigned int)rsa->src_len,
+   (unsigned int)rsa->key_size);
+   return -EINVAL;
+   }
+
+   memset(, 0, sizeof(op));
+   op.cmd_q = cmd_q;
+   op.jobid = CCP_NEW_JOBID(cmd_q->ccp);
+
sb_count = 0;
if (cmd_q->ccp->vdata->version < CCP_VERSION(5, 0)) {
/* sb_count is the number of storage block slots required