Maximally minimal stack trace standardization

Mark S. Miller erights at google.com
Wed Mar 11 19:03:53 UTC 2015


I don't understand. Could you show example code? Thanks.



On Wed, Mar 11, 2015 at 12:00 PM, John Lenz <concavelenz at gmail.com> wrote:

>
>
> On Tue, Mar 10, 2015 at 9:10 PM, Mark S. Miller <erights at google.com>
> wrote:
>
>> On Tue, Mar 10, 2015 at 9:02 PM, Domenic Denicola <d at domenic.me> wrote:
>>
>>>  I don’t see how any of this follows. SES can censor/remove/etc. either
>>> the .stack getter or the .getStack function. They are isomorphic.
>>>
>>
>> I can selectively provide or deny a given getStack function to different
>> code in the same realm.
>>
>
> Can't you do the same by hiding "Error" in the same way that "window" is
> hidden?  Through a proxy or subclass?
>
>
>>
>>
>>>
>>>
>>> .stack already has very close to de-facto standard behavior.
>>>
>>
>> Have you looked at the case analysis I go through in debug.js to parse
>> the variety of stack formats we currently have?
>>
>>
>>
>>> We should be attempting to converge it to a standard, and not leaving it
>>> a non-interoperable mess while adding a second API.
>>>
>>>
>>>
>>> I also don’t see why .stack cannot map backward through different source
>>> maps. Again, a getter and a function are isomorphic in this regard.
>>>
>>
>> In a given realm, there can only be one Error.prototype.stack. But what
>> getStack function is in scope can differ per scope as well as per loader.
>>
>>
>>
>>>
>>>
>>> *From:* Mark S. Miller [mailto:erights at google.com]
>>> *Sent:* Wednesday, March 11, 2015 12:12
>>> *To:* Domenic Denicola
>>> *Cc:* John Lenz; es-discuss; Erik Arvidsson
>>>
>>> *Subject:* Re: Maximally minimal stack trace standardization
>>>
>>>
>>>
>>> No, that makes the std SES API non-conformant to the std API, making
>>> porting more difficult, and making it harder to write code that works in
>>> both environments.
>>>
>>>
>>>
>>> Also, if you make it look like err.stack, then no matter what you
>>> stdize, it will conflict with existing err.stack behavior, since they
>>> conflict with each other. This makes the transition more difficult. If the
>>> new std behavior looks like getStack(err), then it can be rolled out
>>> without creating a transition conflict.
>>>
>>>
>>>
>>> As so often happens, the better security is the better modularity. If
>>> you make it err.stack, then you have to make visible one canonical mapping
>>> to source positions. If you make it getStack(err), then different getStack
>>> functions might map backwards through different sourcemaps.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Mar 10, 2015 at 7:45 PM, Domenic Denicola <d at domenic.me> wrote:
>>>
>>>  Can’t we just have Error.prototype.stack be a getter that SES is
>>> allowed to delete and hide away for its own purposes later?
>>>
>>>
>>>
>>> *From:* es-discuss [mailto:es-discuss-bounces at mozilla.org] *On Behalf
>>> Of *John Lenz
>>> *Sent:* Wednesday, March 11, 2015 08:35
>>> *To:* Mark S. Miller
>>> *Cc:* es-discuss; Erik Arvidsson
>>> *Subject:* Re: Maximally minimal stack trace standardization
>>>
>>>
>>>
>>>  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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> --
>>>
>>>     Cheers,
>>>     --MarkM
>>>
>>
>>
>>
>> --
>>     Cheers,
>>     --MarkM
>>
>
>


-- 
    Cheers,
    --MarkM
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