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Message-ID: <20140519153130.GA519@muslin>
Date: Mon, 19 May 2014 08:31:31 -0700
From: Isaac Dunham <ibid.ag@...il.com>
To: musl@...ts.openwall.com
Subject: thoughts on reallocarray, explicit_bzero?
Having read up on the LibreSSL fork of OpenSSL and also recently
backported a nuber of libXfont CVE fixes for integer overflows,
I've seen the risk posed by malloc(n*sizeof(x)) and realloc(ptr,
n*sizeof(x)).
calloc(n, sizeof(x)) can be used in place of malloc(n * sizeof(x)),
but there's no standard function that does overflow checking for
realloc(). OpenBSD has provided the extension reallocarray(), which
provides for bounds checking like calloc() does.
Additionally, there are times when a compiler will optimize away calls
to bzero() on areas that are not used before free(); this can result in
passwords getting left in memory. OpenBSD uses a wrapper function called
explicit_bzero() to keep this from happening, thugh it seems to be possible
to use some ugliness with volatile to stop it.
Should musl provide reallocarray()?
And what's the best way to ensure that memory gets zeroed out?
Thanks,
Isaac Dunham
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