[Webkit-unassigned] [Bug 210540] Fix an integer overflow in WebCrypto AES-CTR Mac implementation, which may detect a false loop

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=210540

--- Comment #7 from Tomoki Imai <tomoki.imai at sony.com> ---
(In reply to Jiewen Tan from comment #5)
> Comment on attachment 396514 [details]
> patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=396514&action=review
> 
> >>> Source/WebCore/crypto/mac/CryptoAlgorithmAES_CTRMac.cpp:48
> >>> +    if (counterLength < sizeof(size_t) * 8 && numberOfBlocks > ((size_t)1 << counterLength))
> >> 
> >> ((size_t)1 => 1ull
> > 
> > I used ((size_t) 1) rather than 1ull, because I thought using size_t type makes more sense than "unsigned long long".
> > - "counterLength < sizeof(size_t) * 8" checks whether size_t has enough size to store (1 << counterLength)
> > - In 32-bit environment, 1ull, which is 64-bit or larger, is a bit overkill, because counterLength < 31 in 32-bit environment.
> > 
> > How do you think about it?
> > Of course, 1ull should work fine both on 32-bit and 64-bit environment, so I'm fine to change it to 1ull.
> 
> I was not aware we are still supporting 32 bit machines. Doing a C style
> cast is not appropriate in WebKit, please change it to
> static_cast<size_t>(1).

I changed it to static_cast<size_t>(1).
I don't know about Mac implementation, but the other code seems to try to support 32-bit by using size_t.

> 
> > Source/WebCore/ChangeLog:6
> > +        (1 << counterLength) causes an integer overflow, and the undefined behavior.
> 
> Maybe you could reference here:
> https://en.cppreference.com/w/cpp/language/integer_literal.

I added 
- https://en.cppreference.com/w/cpp/language/integer_literal and 
- https://en.cppreference.com/w/cpp/language/operator_arithmetic#Bitwise_shift_operators 
as references.

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