Am Dienstag, 17. März 2015, 22:23:50 schrieb Herbert Xu:
Hi Herbert,
>On Fri, Mar 13, 2015 at 10:09:21PM +0100, Stephan Mueller wrote:
>> +struct crypto_tfm *__crypto_alloc_tfm_safe(struct crypto_alg *alg,
>> u32 type, + u32 mask)
>> +{
>> + /*
>> + * Prevent all ciphers from being loaded which have a
cra_priority
>> + * of 0. Those cipher implementations are helper ciphers and
>> + * are not intended for general consumption.
>> + *
>> + * The only exceptions are the compression algorithms which
>> + * have no priority.
>> + */
>> + if (!alg->cra_priority &&
>> + ((alg->cra_flags & CRYPTO_ALG_TYPE_MASK) !=
>> + CRYPTO_ALG_TYPE_PCOMPRESS) &&
>> + ((alg->cra_flags & CRYPTO_ALG_TYPE_MASK) !=
>> + CRYPTO_ALG_TYPE_COMPRESS))
>> + return ERR_PTR(-ENOENT);
>
>How about adding a flag to all these internal algorithms and then
>change crypto_alg_mod_lookup to disable that flag by default?
The issue with flags is the following: first we have to think about
whether we want a black list or white list approach. Your suggestion
implies a black list. Black lists for ensuring security is not good IMHO
as it has a tendency to miss cases. This especially applies to this area
where we have already an indicator for internal ciphers: the prio is so
low that it will never ever be selected based on the name. Now, adding a
flag means that we mark such an internal cipher twice.
Therefore, I would not opt for such a flag (at least for a black list)
and stay with the prio approach.
Ciao
Stephan
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