crypto: dh - Don't permit 'key' or 'g' size longer than 'p'

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@vger.kernel.org> # v4.8+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index 788a9e5..24fdb2e 100644 (file)
--- 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
         */