[pro] Heartbleed?

[Steve Haflich]

On Thu, Apr 24, 2014 at 10:35 PM, Jean-Claude Beaudoin <
jean.claude.beaudoin at gmail.com> wrote:

>
> On Fri, Apr 25, 2014 at 12:31 AM, Scott L. Burson <Scott at sympoiesis.com>wrote:
>
>>
>> I've long thought that was an oversight, though now that you point it
>> out, I realize I must have been mistaken.
>>
>
"Oversight" might be the wrong way of thinking about this. X3J13 started
with the language defined by CLtL1 (the work of the infamous Gang of Five)
with the purpose of turning it into a powerful, useful, real-world
industrial-strength programming language.  Except for new subsystems
grabbed more-or-less intact from other sources (Waters' pretty printer, the
condition system (Pitman and others), and CLOS (a different gang inside
X3J13)) the specification started with the CLtL1 definitions to which
cleanups and accretions were made.  There were a lot of inconsistencies to
remove, and a lot of language cleanups, and a lot of incompatibilities as
modern features were added.  But a lot of culture from early era Lisps
(primarily MACSYMA) remain.  We changed what _needed_ to be changed,
cleaned up a lot of other inelegances, but there was not time or energy to
attempt a thorough job.  The subgroups for things like graphics and I18N
and networking realized the time was not yet ripe -- the world was changing
out from under them -- and the committee The process took almost 6 years,
and near the end time and funding was running out.  Eventually the
committee standardized _only_ the programming language, more or less, and
we were lucky to get it done.


> Still, it surprises me.  I don't know of any implementation that
>> doesn't bounds-check aref under normal speed/safety settings, and
>> clearly, users expect them to do so.
>>
>
> I am surprised too. I always understood it like you Scott but now that
> re-read
> the page on aref I see that it is exactly like Steve says, no mention of
> any
> exception and a statement that "subscripts" must be a list of valid array
> indices
> right from the start of the call to aref. Yet that leaves me even more
> curious
> to know which implementation has read the spec as strictly as Steve says
> it can be even under (safety 3)? Does anyone know any?
>

I don't know of any and there might not be any, at least among main-line
implementations.   I don't remember X3J13 considering aref (except for the
non-interaction with a fill pointer) but I also can't remember what I had
for breakfast this morning, so investigation of X3J13 records might reveal
differently.  The lack of exhaustive subtyping of cl:error was recognized
as something missing, but the condition system itself wasn't in the
original language, and no one had the time or energy to go through the
entire specification.  The sense was that a quality implementation could do
so itself, and maybe agre on details in the future.

But in your paragraph above I'm bothered by its hidden assumption: It
suggests that after the ANS was available sneaky implementors studied it
kabalistically to find places where annoying error checks could be removed.
 It was exactly the opposite!  Tired implementors slogged through the ANS
to find places where error checking was _required_ and found missing.  (Or
customers did it for them.)

I agree it would be a good thing if the ANS required aref bounds checking
in safe code.

To return to my important point, the language of the ANS wont let you read
or write from a socket.  At some point user application code will have to
call some non-ANS functions, and in the real world those functions (just
like C) will take a pointer into some overlarge buffer array along with a
length, and that memory location will be passed further down to some system
code (likely written in C) that has access to the entire user-space memory.
 Now, without the missing check on the length that allowed the Heartbleed
bug, such an error won't allow buffer overruns in either input or output,
but my point is that user C code and user CL code are little different in
this regard.
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