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Date: Fri, 15 Jan 2016 13:56:33 +0100
From: Yann Droneaud <ydroneaud@...eya.com>
To: oss-security@...ts.openwall.com
Subject: Re: Qualys Security Advisory - Roaming through the
 OpenSSH client: CVE-2016-0777 and CVE-2016-0778

Hi,

Le vendredi 15 janvier 2016 à 12:06 +0100, Florian Weimer a écrit :
> On 01/14/2016 06:13 PM, Qualys Security Advisory wrote:
> > Internal stdio buffering is the most severe of the three problems
> > discussed in this section, although GNU/Linux is not affected
> > because the glibc mmap()s and munmap()s (and therefore cleanses)
> > stdio buffers.
> 
> This will change in glibc 2.23, stdio will use regular malloc and
> free for its buffers.  I did not expect this change to have security
> implications.  Considering that the actual bug lies elsewhere, and
> stdio usage is based on copying out of the buffer (so leaks can still
> happen elsewhere), I do not wish to revert this change.
> 

Would setvbuf(stream, NULL, _IONBF, 0); be used to disable buffer
before reading/writting sensible data to a stream ?

What about a buffering flag (_IOSBF) that would enable "secure" 
handling of the buffer, that is, on fclose() and fflush(), write
back and cleanse buffer on output stream, cleanse buffer on input
stream ?

Regards.

-- 
Yann Droneaud
OPTEYA

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