Maximally minimal stack trace standardization

John Lenz concavelenz at gmail.com
Tue Mar 10 23:34:50 UTC 2015


 Ok, as long as we are clear there is an existing information leak on
non-v8 engines.


On Tue, Mar 10, 2015 at 1:48 PM, Mark S. Miller <erights at google.com> wrote:

> On Chrome and Opera (v8), <
> https://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/debug.js>
> hides the stack. It is important that we not lose this.
>
> Regarding the rest, as previously discussed, there are enough differences
> between browsers that there is no legacy we must codify because of web-wide
> agreement. Take a look at the extensive efforts <
> https://code.google.com/p/google-caja/source/browse/trunk/src/com/google/caja/ses/debug.js>
> makes to parse despite these differences in stack format. As long as we're
> standardizing something not compat with web-wide legacy, as we must, we
> might as well also fix this security leak in the process.
>
>
>
>
> On Tue, Mar 10, 2015 at 1:24 PM, John Lenz <concavelenz at gmail.com> wrote:
>
>>
>>
>> On Mon, Mar 9, 2015 at 5:45 PM, Mark S. Miller <erights at google.com>
>> wrote:
>>
>>> On Mon, Mar 9, 2015 at 5:02 PM, John Lenz <concavelenz at gmail.com> wrote:
>>>
>>>>
>>>>
>>>> On Mon, Mar 9, 2015 at 12:15 PM, Mark S. Miller <erights at google.com>
>>>> wrote:
>>>>
>>>>> On Sat, Mar 7, 2015 at 2:55 PM, John Lenz <concavelenz at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> I wanted to ping this thread and see how we could get "max-min stack
>>>>>> traces" to the next step?
>>>>>>
>>>>>
>>>>> Hi John, the best way to take this to the next step is to read <
>>>>> https://docs.google.com/document/d/1QbEE0BsO4lvl7NFTn5WXWeiEIBfaVUF7Dk0hpPpPDzU/edit>
>>>>> and submit a proposal to <https://github.com/tc39/ecma262>.
>>>>>
>>>>> "If you are a TC39 member representative, just submit a pull request
>>>>> for your proposal."
>>>>>
>>>>> Since you are at a member organization, attend and participate
>>>>> actively at TC39 meetings to advance your proposal through the process.
>>>>>
>>>>> Please keep in mind that the stack trace information should not be
>>>>> available simply from the error object by itself, as that is a bad
>>>>> information leak.
>>>>>
>>>>
>>>> The threads I dug up, simply state what you state here.  That there is
>>>> an "information leak".  Are filename and function names considered
>>>> sensitive?  In what way?
>>>>
>>>
>>> They reveal details of the callee's computation to the caller that the
>>> callee should have been able to assume were private. See starting at middle
>>> of 2nd paragraph of <
>>> http://combex.com/papers/darpa-review/security-review.html#UniversalScope
>>> >.
>>>
>>>
>>> the depth of the execution stack is visible, which could pose a risk in
>>> certain scenarios: for instance, consider trusted code containing a
>>> recursive function whose level of recursion depends on some sensitive data
>>> (e.g., a secret cryptographic key), and suppose the recursive function is
>>> called with arguments that induce it to hit an error condition and throw an
>>> exception from deep within the recursion.  In such a case, the caller might
>>> be able to learn something about the callee’s secrets by catching the
>>> exception, examining the resulting stack trace, and recovering the stack
>>> depth.  These scenarios do not occur in the DarpaBrowser, but have been
>>> used in exploits on other systems.  Accordingly, though the risk for
>>> DarpaBrowser is small, it should probably be repaired (Fixing this was
>>> determined not to be hard).
>>>
>>>
>>>     --David Wagner and E. Dean Tribble,
>>>         "A Security Review of the Combex DarpaBrowser Architecture"
>>>
>>>
>>> Likewise, the risk here -- of only a stack of function names and source
>>> positions -- is small. But it violates the normal privacy assumptions
>>> between caller and callee; and fixing it is again not hard -- via getStack.
>>>
>>>
>>>
>>>
>>>> I did not intend to promote a "rich stack inspection API" such as V8
>>>> has.
>>>>
>>>
>>> That's good, but there is one thing I really like about the rich
>>> inspection API that it would be a shame to lose: The user doesn't have to
>>> do their own adhoc parsing of yet another ad hoc textual format. Since this
>>> format contains function names, we would then even need to worry about
>>> maliciously chosen function names, intended to get this stack format
>>> parsing code to misparse. If the stack is a stack of, for example, JSON
>>> strings, then we avoid this hazard.
>>>
>>>
>> Sure, but I feel like that is independent, I mostly want to codify what
>> already exists and standardize throw/rethrow behavior.   That is why I ask
>> about the information leak.  Error objects already have "stack" properties
>> on all the major browsers. If "stack" leaks information then they already
>> do and the rectification should be there. (It makes no sense to add a
>> "leak-free" API when a "leaky" one already exists).
>>
>>
>>>
>>> --
>>>     Cheers,
>>>     --MarkM
>>>
>>
>>
>
>
> --
>     Cheers,
>     --MarkM
>
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