Google patches second Chrome zero-day in two weeks

https://www.zdnet.com/article/google-patches-second-chrome-zero-day-in-two-weeks/

by LinuxBender • 6 years ago

114 43 6 years ago

zdnet.com

marketingPro• 6 years ago

Shouldn't Chrome force restart because of this exploit?

I'm not sure what's better, keeping data in tabs but at risk, or involuntarily losing data to protect users.

hoten• 6 years ago

An option to do this would be interesting and useful, especially for security-minded organizations. I personally wouldn't enable it myself.

pizza234• 6 years ago

CVE-2020-16009 and CVE-2020-15999 are described are "heap corruption". Are those two¹ bugs possible only in memory unsafe programming languages (in other words, they don't happen with safe programming languages and practices)?

¹=edit: clarified I was referring to the specific bugs

roblabla• 6 years ago

It's hard to make sweeping claims without knowing what this exact bug looked like (and the associated chromium issue isn't public yet, I believe). Generally speaking, memory-safe programming languages (Java, Safe Rust, Python...) shouldn't have any heap corruption bugs (modulo bugs in their implementation, of course). Memory-safe generally means that memory corruption of all kinds are impossible. But Heap Corruption is a very broad category.

metajack• 6 years ago

Diane wrote an analysis of how many bugs would have been avoided had the Servo style system been in Gecko all along: https://hacks.mozilla.org/2019/02/rewriting-a-browser-compon...

"There’s a significant overlap between memory vulnerabilities and severe security problems. Of the 34 critical/high bugs, 32 were memory-related."

Rust doesn't fix everything, and this result won't hold for code that is itself security logic (ie, crypto implementation) as logic errors are also very bad. But fixing memory safety does address almost all the high and critical severity issues.

Microsoft published similar research: https://msrc-blog.microsoft.com/2019/07/18/we-need-a-safer-s...

Keep in mind that the Gecko style system has had two decades of work before the Rust code came along, and was written by some excellent programmers. It was extensively fuzzed for years. And still, Rust has enormous potential to solve these security issues.

Only time will tell if the next decade with Rust will pan out as the data seem to predict, but I am quite hopeful.

im3w1l2• 6 years ago

One question I have, since the JVM, Flash VM, and also Javascript VM seems to have occasional security issues - how confident are we that rustc bugs wont undermine the security of correctly written rust programs?

muizelaar• 6 years ago

CVE-2020-15999 was described as:

"A vulnerability exists in the function `Load_SBit_Png`, which processes PNG images embedded into fonts. This function:

1) Obtains the image width and height from the header as 32-bit integers.

2) Truncates the obtained values to 16 bit and stores them in a `TT_SBit_Metrics` structure.

3) Uses the truncated values to calculate the bitmap size.

4) Allocates the backing store of that size.

5) Passes `png_struct` and the backing store to a libpng function.

The issue is that libpng uses the original 32-bit values, which are saved in `png_struct`. Therefore, if the original width and/or height are greater than 65535, the allocated buffer won't be able to fit the bitmap."

This one could only happen in an memory unsafe programming language. Having bounds checks on the destination buffer would have avoided the problem.

im3w1l2• 6 years ago

The issue is in the bindings, which necessarily call libpng in an unsafe way. But if you use known-good bindings it should be prevented. Or if you use a native memory safe library for that matter.

jeffbee6• 6 years ago

FreeType is an endless shitshow of security vulnerabilities going back 25 years now. There's really no excuse in 2020 for writing libraries to decode file formats in unsafe languages. Yes, there are performance-sensitive aspects to image decoding, but opening the file and reading two integers is not one of those.

pjmlp6• 6 years ago

As Hoare would put it in 1981,

"The first principle was security: The principle that every syntactically incorrect program should be rejected by the compiler and that every syntactically correct program should give a result or an error message that was predictable and comprehensible in terms of the source language program itself. Thus no core dumps should ever be necessary. It was logically impossible for any source language program to cause the computer to run wild, either at compile time or at run time. A consequence of this principle is that every occurrence of every subscript of every subscripted variable was on every occasion checked at run time against both the upper and the lower declared bounds of the array. Many years later we asked our customers whether they wished us to provide an option to switch off these checks in the interests of efficiency on production runs. Unanimously, they urged us not to--they already knew how frequently subscript errors occur on production runs where failure to detect them could be disastrous. I note with fear and horror that even in 1980, language designers and users have not learned this lesson. In any respectable branch of engineering, failure to observe such elementary pre- cautions would have long been against the law."

https://www.cs.fsu.edu/~engelen/courses/COP4610/hoare.pdf

I guess in IT one needs a couple of decades to be proven right.

MauranKilom• 6 years ago

Having bounds checks on the destination buffer would have avoided the problem.

Since the access to the buffer happens inside libpng, this means libpng should have bounds checks compiled in according to your argument. (Hoping that the compiler can elide them by seeing through the library interface is but wishful thinking.)

Would you rather have a slower version of libpng that defends against screwups of the calling code, or a faster version that assumes the calling code is sane? Not an obvious choice to me.

kentonv• 6 years ago

Are those two¹ bugs possible only in memory unsafe programming languages

CVE-2020-16009 is a bug in V8 (Chrome's implementation of JavaScript).

You could write a JavaScript implementation in Rust. However, to achieve acceptable performance, you would almost certainly need to use a lot of "unsafe" code. A performant JavaScript implementation has to be able to generate raw machine code, after all, and then execute it. And the garbage collector probably isn't going to manage memory in a way that the Rust compiler can verify for correctness.

So no, "use a memory-safe language" isn't a simple answer to this kind of bug. Using Rust could reduce the attack surface somewhat but certainly would not completely prevent bugs.

st1x7• 6 years ago

Can anyone explain what a zero-day vulnerability is? What's the difference between zero-day and non-zero-day vulnerabilities? I'm not getting much out of wikipedia.

NietTim• 6 years ago

The way I understand it a zero-day vulnerability is actively being abused, thus you have zero days to fix it. But I can be wrong

thelean12• 6 years ago

It doesn't need to be actively used. It just needs to have the potential to be actively used, and still need to fix it right away in case it is.

saagarjha2• 6 years ago

A zero day vulnerability is one the manufacturer doesn’t know about or has had zero days of notice on (“zero days to fix”). An n-day vulnerability means the manufacturer has had that much time to deal with it before it goes public.

jturpin• 6 years ago

I believe this is the correct usage of the term, but it seems that articles now use it to mean any vulnerability of any kind regardless of disclosure/patch turnaround, which can add a lot of confusion when reading.

kerng• 6 years ago

Wow, Chrome's security seems more and more like IE.. the number of bugs is just astonishing.

nyanpasu64• 6 years ago

On October 20, Google also released a security update for Chrome to patch CVE-2020-15999, a zero-day in Chrome's FreeType font rendering library.
As Google revealed last week on Friday, this Chrome zero-day was utilized together with a Windows zero-day (CVE-2020-17087).

I thought Chrome only used DirectWrite font rendering on Windows, and only used dynamically linked system FreeType on Linux-like platforms. https://bugs.chromium.org/p/chromium/issues/detail?id=670480 shows that some people were discussing using FreeType on Windows, but it doesn't seem to have resulted in any actions.

Google patches second Chrome zero-day in two weeks

Related Stories