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SubjectRe: [PATCH 14/14] x86/crypto: aesni: Update aesni-intel_glue to use scatter/gather
On 02/13/18 08:42 AM, Stephan Mueller wrote:
> > +static int gcmaes_encrypt_sg(struct aead_request *req, unsigned int
> > assoclen, + u8 *hash_subkey, u8 *iv, void *aes_ctx)
> > +{
> > + struct crypto_aead *tfm = crypto_aead_reqtfm(req);
> > + unsigned long auth_tag_len = crypto_aead_authsize(tfm);
> > + struct gcm_context_data data AESNI_ALIGN_ATTR;
> > + struct scatter_walk dst_sg_walk = {};
> > + unsigned long left = req->cryptlen;
> > + unsigned long len, srclen, dstlen;
> > + struct scatter_walk src_sg_walk;
> > + struct scatterlist src_start[2];
> > + struct scatterlist dst_start[2];
> > + struct scatterlist *src_sg;
> > + struct scatterlist *dst_sg;
> > + u8 *src, *dst, *assoc;
> > + u8 authTag[16];
> > +
> > + assoc = kmalloc(assoclen, GFP_ATOMIC);
> > + if (unlikely(!assoc))
> > + return -ENOMEM;
> > + scatterwalk_map_and_copy(assoc, req->src, 0, assoclen, 0);
>
> Have you tested that this code does not barf when assoclen is 0?
>
> Maybe it is worth while to finally add a test vector to testmgr.h which
> validates such scenario. If you would like, here is a vector you could add to
> testmgr:
>
> https://github.com/smuellerDD/libkcapi/blob/master/test/test.sh#L315

I tested assoclen and cryptlen being 0 and it works, yes. Both
kmalloc and scatterwalk_map_and_copy work correctly with 0 assoclen.

> This is a decryption of gcm(aes) with no message, no AAD and just a tag. The
> result should be EBADMSG.
> > +
> > + src_sg = scatterwalk_ffwd(src_start, req->src, req->assoclen);
>
> Why do you use assoclen in the map_and_copy, and req->assoclen in the ffwd?

If I understand correctly, rfc4106 appends extra data after the assoc.
assoclen is the real assoc length, req->assoclen is assoclen + the
extra data length. So we ffwd by req->assoclen in the scatterlist,
but use assoclen when memcpy and testing.

> >
> > +static int gcmaes_decrypt_sg(struct aead_request *req, unsigned int
> > assoclen, + u8 *hash_subkey, u8 *iv, void *aes_ctx)
> > +{
>
> This is a lot of code duplication.

I will merge them and send a V2.

> Ciao
> Stephan
>
>

Thanks!

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