RE: [PATCH v3 1/2] staging: rtl8188eu: Replace a custom function with crc32_le()

David Laight
2021-07-22T15:30:18Z

From: Fabio M. De Francesco
> Sent: 21 July 2021 12:01
>
> Use crc32_le() in place of the custom getcrc32().
>
...
> @@ -609,14 +595,15 @@ u32 rtw_tkip_encrypt(struct adapter *padapter, struct xmit_frame
> *pxmitframe)
>
> if ((curfragnum + 1) == pattrib->nr_frags) { /* 4 the last fragment */
> length = pattrib->last_txcmdsz - pattrib->hdrlen - pattrib->iv_len -
> pattrib->icv_len;
> - *((__le32 *)crc) = getcrc32(payload, length);/* modified by Amy*/
> + *((__le32 *)crc) = cpu_to_le32(~crc32_le(~0, payload, length));
>
> arcfour_init(&mycontext, rc4key, 16);
> arcfour_encrypt(&mycontext, payload, payload, length);
> arcfour_encrypt(&mycontext, payload + length, crc, 4);
> } else {
> length = pxmitpriv->frag_len - pattrib->hdrlen - pattrib->iv_len -
> pattrib->icv_len;
> - *((__le32 *)crc) = getcrc32(payload, length);/* modified by Amy*/
> + *((__le32 *)crc) = cpu_to_le32(~crc32_le(~0, payload, length));
> +
> arcfour_init(&mycontext, rc4key, 16);
> arcfour_encrypt(&mycontext, payload, payload, length);
> arcfour_encrypt(&mycontext, payload + length, crc, 4);

Change crc to be __le32, kill the casts and pass &crc in the last call.

> @@ -682,7 +669,7 @@ u32 rtw_tkip_decrypt(struct adapter *padapter, struct recv_frame *precvframe)
> arcfour_init(&mycontext, rc4key, 16);
> arcfour_encrypt(&mycontext, payload, payload, length);
>
> - *((__le32 *)crc) = getcrc32(payload, length - 4);
> + *((__le32 *)crc) = cpu_to_le32(~crc32_le(~0, payload, length - 4));
>
> if (crc[3] != payload[length - 1] ||
> crc[2] != payload[length - 2] ||

You could to the same here, or make crc u32, remove the cpu_to_le32()
and use get_unaligned_u32(payload + length - 4) (or whatever it is called).

But it is much better to do:
crc = crc32_le(~0, payload, length);
if (crc != VALID_CRC32)
res = _FAIL;

You can lookup VALID_CRC32, but it is crc32_le(0, "\xff\xff\xff\xff", 4);

David

-
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