From: Eric Biggers <ebigg...@google.com>

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 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: <sta...@vger.kernel.org> # v4.8+
Signed-off-by: Eric Biggers <ebigg...@google.com>
---
 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
         */
-- 
2.15.0.403.gc27cc4dac6-goog

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