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Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs

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On Wed, Dec 14, 2016 at 12:37 AM, David Howells <dhowells@redhat.com> wrote:
> Andy Lutomirski <luto@amacapital.net> wrote:
>
>> > -       sg_set_buf(&sg_out[1], pad, sizeof pad);
>> > +       sg_set_buf(&sg_out[1], empty_zero_page, 16);
>>
>> My fix here is obviously bogus (I meant to use ZERO_PAGE(0)), but what
>> exactly is the code trying to do?  The old code makes no sense.  It's
>> setting the *output* buffer to zeroed padding.
>
> Padding goes into the encrypt function and is going to come out of the decrypt
> function.  Possibly derived_key_decrypt() should be checking that the padding
> that comes out is actually a bunch of zeros.  Maybe we don't actually need to
> get the padding out, but I'm not sure whether the crypto layer will
> malfunction if we don't give it a buffer for the padding.

It was the memset that threw me for a loop.

David, are these encrypted keys ever exported anywhere?  If not, could
the code use a mode that doesn't need padding?

--Andy

>
> David



-- 
Andy Lutomirski
AMA Capital Management, LLC

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[PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Andy Lutomirski <luto@kernel.org> - 2016-12-14 03:50 +0100
  Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Andy Lutomirski <luto@amacapital.net> - 2016-12-14 04:10 +0100
    Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-14 06:10 +0100
      Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Eric Biggers <ebiggers3@gmail.com> - 2016-12-14 09:20 +0100
    Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs David Howells <dhowells@redhat.com> - 2016-12-14 09:40 +0100
      Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs Andy Lutomirski <luto@amacapital.net> - 2016-12-14 17:30 +0100
        Re: [PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs David Howells <dhowells@redhat.com> - 2016-12-14 18:10 +0100

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