Re: [PATCH v2 3/5] crypto: dh - Don't permit 'key' or 'g' size longer than 'p'

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On 11/06/2017 04:30 AM, Eric Biggers wrote:
From: Eric Biggers <ebiggers@xxxxxxxxxx>

The "qat-dh" DH implementation assumes that 'key' and 'g' can be copied
into a buffer with size 'p_size'.  However it was never checked that
that was actually the case, which most likely allowed users to cause a
buffer underflow via KEYCTL_DH_COMPUTE.

Fix this by updating crypto_dh_decode_key() to verify this precondition
for all DH implementations.

Fixes: c9839143ebbf ("crypto: qat - Add DH support")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.8+

Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
  crypto/dh_helper.c | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index 708ae20d2d3c..7f00c771fe8d 100644
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c
@@ -83,6 +83,14 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
  	if (secret.len != crypto_dh_key_len(params))
  		return -EINVAL;
+ /*
+	 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
+	 * some drivers assume otherwise.
+	 */
+	if (params->key_size > params->p_size ||
+	    params->g_size > params->p_size)
+		return -EINVAL;
+
  	/* Don't allocate memory. Set pointers to data within
  	 * the given buffer
  	 */




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