Re: [PATCH 1/9] crypto: add zbufsize() interface

Kees Cook
2018-08-07T18:10:17Z

On Tue, Aug 7, 2018 at 2:45 AM, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Thu, Aug 02, 2018 at 02:51:10PM -0700, Kees Cook wrote:
>> When pstore was refactored to use the crypto compress API in:
>>
>> commit cb3bee0369bc ("pstore: Use crypto compress API")
>>
>> nearly all the pstore-specific compression routines were replaced with
>> the existing crypto compression API. One case remained: calculating the
>> "worst case" compression sizes ahead of time so it could have a buffer
>> preallocated for doing compression (which was called "zbufsize").
>>
>> To make pstore fully algorithm-agnostic, the compression API needs to
>> grow this functionality. This adds the interface to support querying the
>> "worst case" estimate, with a new "zbufsize" routine that each compressor
>> can implement. The per-compressor implementations come in later commits.
>>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>> crypto/compress.c | 9 +++++++++
>> include/crypto/internal/scompress.h | 11 +++++++++++
>> include/linux/crypto.h | 12 ++++++++++++
>> 3 files changed, 32 insertions(+)
>>
>> diff --git a/crypto/compress.c b/crypto/compress.c
>> index f2d522924a07..29a80bb3b9d3 100644
>> --- a/crypto/compress.c
>> +++ b/crypto/compress.c
>> @@ -33,12 +33,21 @@ static int crypto_decompress(struct crypto_tfm *tfm,
>> dlen);
>> }
>>
>> +static int crypto_zbufsize(struct crypto_tfm *tfm,
>> + unsigned int slen, unsigned int *dlen)
>> +{
>> + if (!tfm->__crt_alg->cra_compress.coa_zbufsize)
>> + return -ENOTSUPP;
>> + return tfm->__crt_alg->cra_compress.coa_zbufsize(tfm, slen, dlen);
>> +}
>
> Please don't add new features to the old compress interface. Any
> new improvements should be added to scomp/acomp only. Users who
> need new features should be converted.

So, keep crypto_scomp_zbufsize() and drop crypto_comp_zbufsize() and
crypto_zbufsize()? Should I add crypto_acomp_zbufsize()?

-Kees

--
Kees Cook
Pixel Security