On Fri, Jan 20, 2017 at 9:22 AM, Dirk-Willem van Gulik
<di...@webweaving.org> wrote:
>
> As to the selection of the hash - I can see three strategies
>
> A) current approach (we do this I think only for sha256):
>
> apr_crypto_hash_t * ctx = apr_crypto_sha256_new(pool);
>
> followed by a hash neutral/generic
>
> apr_hash(sha256_ctx, &buf, &len, plain, plainlen, pool);
Probably apr_crypto_hash() since apr_hash() is non-crypto hashtable in APR.
Would be nice to have init/update/finish versions too.
>
> and then create the the corresponding
>
> apr_crypto_md4_new(apr_pool_t *);
> apr_crypto_md5_new(apr_pool_t *);
> apr_crypto_sha1_new(apr_pool_t *);
> apr_crypto_sha256_new(apr_pool_t *);
>
> and create new ones (eg. SHA512 etc, etc) as we go along.
I like C) more since you propose ;)
>
> B) more of the ENUM approach as used elsewhere in APR:
>
> enum {
> APR_CRYPTO_SANE_DEFAULT = APR_CRYPTO_SHA256, //
> whatever the report of Ecrypt/NIST recommended in the year of the release.
> APR_CRYPTO_MD4,
> APR_CRYPTO_MD5,
> ....
>
> apr_crypto_hash_t * ctx = apr_crypto_hash_new(pool,
> APR_CRYPTO_MD4);
>
> with the goal of deprectating the apr_crypto_sha256_new soon. Which
> has
> the downside that this ultimately means numbers rather than symbols
> and limiting what you can spot at link time.
Quite the same as A) from an evolutivity perspective, with the
mentioned downside.
>
> C) something more akin to what I use now (as the code I am trying
> to get under long term maintenance control fudges things a bit
> to deal with hardware base crypto (network HSMs and cheap
> USB chipcards/SIMS):
>
> #define APR_CRYPTO_MD4 "MD4"
> apr_crypto_hash_t * ctx = apr_crypto_hash_new(pool,
> APR_CRYPTO_MD4);
>
> where the strings are picked so that they work with the existing
> char* based pickers of openssl and nss (EVP_get_digestbyname et.al.).
I like it, quite agile wrt APR release cycle.
Maybe return an apr_status_t somehow for things like APR_ENOTIMPL.
>
> Does anyone have any strong opinions ?
Not strong, but C) if no objection raises.
Anyway, thanks for this work, authenticated encryption (AES-GCM,
Chacha20-poly, caesar upcoming portfolio, ...) would be nice too.
Regards,
Yann.
