[Toybox] [PATCH] readelf: harden against invalid input.

[Rob Landley]

On 11/17/20 6:29 PM, enh via Toybox wrote:
> On Thu, Nov 12, 2020 at 4:03 PM enh <enh at google.com> wrote:
>>
>> I also promised to fix readelf. Where in file(1) I made no attempt to
>> say what was bad (or even to change `goto bad` to explicitly say that
>> *anything* was bad), I believe that readelf is much more likely to be
>> shown invalid ELF files, and that it would be useful to have some clue
>> as to what's wrong. Relatedly, this patch removes all existing
>> error_exit() calls in case it's being used on multiple files.
>>
>> Again, this survived ~24hrs of AFL++ trying to blow its house down.
> 
> actually, because i forgot to kill AFL++ and just lost the window in
> my stack, this has now survived nearly a week of continuous fuzzing
> :-)

Your work environment is SO different from mine.

My (often battery-powered) laptop has the xfce cpu meter with 4 vertical bar
graphs and a horizontal line graph and when a chrome tab persistently uses CPU I
find it with "top" and kill the "renderer" instance. (Which on modern chrome
will sometimes make the locking unhappy so a tab doesn't acknowledge input even
to scroll up and down, the fix to which is ctrl-w ctrl-shift-t to kill and
reopen it...)

I'll leave it doing something cpu intensive (such as an AOSP build or rebuilding
the musl-cross-make toolchains) overnight, but if it's not done in the morning
it gets suspended or killed...

(Hey, this laptop is almost twice as expensive as my netbook was. The Dell e6230
was hot stuff in 2012, and when I got it last year I upgraded the memory as far
as it would go and broke down and got a 2tb ssd.)

>> Test: ~/AFLplusplus/afl-fuzz -i tests/files/elf -o fuzz-out -- ./readelf -a @@

Uh-huh:

  https://github.com/AFLplusplus/AFLplusplus#how-to-fuzz-with-afl

Alas, bit too much domain expertise required for me to go down that rathole on
any other commands just now. Couple interesting youtube videos on it though...

Rob