linux-kernel - Re: [PATCH 17/23] pefile: Strip the wrapper off of the cert data block

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Message-ID: <23196.1351645419@warthog.procyon.org.uk>
Date:	Wed, 31 Oct 2012 01:03:39 +0000
From:	David Howells <dhowells@...hat.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	dhowells@...hat.com, rusty@...tcorp.com.au, pjones@...hat.com,
	jwboyer@...hat.com, mjg@...hat.com, dmitry.kasatkin@...el.com,
	zohar@...ux.vnet.ibm.com, keyrings@...ux-nfs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 17/23] pefile: Strip the wrapper off of the cert data block

Kees Cook <keescook@...omium.org> wrote:

> > +       memcpy(&wrapper, prep->data + ctx->sig_offset, 8);
> 
> Instead of the literal 8, sizeof(wrapper)?

Reasonable.  It was originally an array of bytes until I found out that it had
structure.  Even so, I should probably have used sizeof() then.

> > +               if (pkcs7[1] == 0x82 &&
> > +                   pkcs7[2] == (((ctx->sig_len - 4) >> 8) & 0xff) &&
> > +                   pkcs7[3] ==  ((ctx->sig_len - 4)       & 0xff))
> > +                       return 0;
> > +               if (pkcs7[1] == 0x80)
> > +                       return 0;
> > +               if (pkcs7[1] > 0x82)
> > +                       return -EMSGSIZE;
>
> Can these literals be replaced with something more meaningful?

Certainly the 0x80 can.  I have a patch to define ASN1_INDEFINITE_LENGTH.  The
question is how to define the 0x82 since it's a flag plus a value.  Maybe by
using something like:

	#define ASN1_LONG_LENGTH(x) (0x80 | (x))

Anyway, thanks for the reviews!

David
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