CVE-2016-5161

CVE: CVE-2016-5161
CWE:
- 229
- 704
bugs:
- 622420
repo: 
vccs:
- note: Fixed a different issue with merging styles.
  commit: 3404893f208a8fe55d2f137d240ea3901b951757
- note: Changed around the architecture to make it more modularized.
  commit: 43ebfe1051df6ec676c14c68011d24f8fd356619
fixes:
- note: ''
  commit: aadb63893e4c1358d1e5139aa29552eb190682c8
bounty:
  date: 
  amount: 
  references: []
lessons:
  yagni:
    note: 
    applies: false
  question: |
    Are there any common lessons we have learned from class that apply to this
    vulnerability? In other words, could this vulnerability serve as an example
    of one of those lessons?

    Leave "applies" blank or put false if you did not see that lesson (you do
    not need to put a reason). Put "true" if you feel the lesson applies and put
    a quick explanation of how it applies.

    Don't feel the need to claim that ALL of these apply, but it's pretty likely
    that one or two of them apply.

    If you think of another lesson we covered in class that applies here, feel
    free to give it a small name and add one in the same format as these.
  serial_killer:
    note: 
    applies: false
  complex_inputs:
    note: |
      There was some CSS that they hadn't considered with custom properties,
      and that broke their code.
    applies: true
  distrust_input:
    note: |
      Their issue wasn't completely related to this because it should
      have been able to understand the CSS, but they had failed to consider
      a specific type of input.
    applies: true
  least_privilege:
    note: 
    applies: false
  native_wrappers:
    note: 
    applies: false
  defense_in_depth:
    note: 
    applies: false
  secure_by_default:
    note: 
    applies: false
  environment_variables:
    note: 
    applies: false
  security_by_obscurity:
    note: 
    applies: false
  frameworks_are_optional:
    note: 
    applies: false
reviews:
- 2103043004
- 2245573002
upvotes: 3
mistakes:
  answer: |
    It was a design mistake. They failed to consider a certain type of input,
    which when entered had the potential to break their system. They should
    have considered CSS properties with custom values when desiging the
    merging functionality. They should have had people who are experts in CSS
    looking over the code to make sure that their implementation conforms to
    the standards, the stakes are high for a project like this and google
    definitely has the resources. They also could have written tests for all
    of the different types of CSS inputs to make sure the merging worked as
    expected for a variety of inputs.
  question: |
    In your opinion, after all of this research, what mistakes were made that
    led to this vulnerability? Coding mistakes? Design mistakes?
    Maintainability? Requirements? Miscommunications?

    Look at the CWE entry for this vulnerability and examine the mitigations
    they have written there. Are they doing those? Does the fix look proper?

    Use those questions to inspire your answer. Don't feel obligated to answer
    every one. Write a thoughtful entry here that those ing the software
    engineering industry would find interesting.
announced: '2016-09-11 06:59:17.817000000 -04:00'
subsystem:
  name: 'WebKit

    '
  answer: 'It was in the third party library WebKit.

    '
  question: |
    What subsystems was the mistake in?

    Look at the path of the source code files code that were fixed to get
    directory names. Look at comments in the code. Look at the bug reports how
    the bug report was tagged. Examples: "clipboard", "gpu", "ssl", "speech", "renderer"
discovered:
  date: '2016-06-22'
  answer: "It was discovered someone working at Trend Micro's Zero Day Initiative.
    It \nwas reported on the bug site by zdi-disc...@hp.com and it looks like either
    \nthe ... is part of the email or there's an issue with the site. Trend Micro\nis
    an organization that rewards researchers for reporting bugs to vendors\ninstead
    of trying to sell them or something to people with malicious \nintentions.\n"
  google: false
  contest: true
  question: |
    How was this vulnerability discovered?

    Go to the bug report and read the conversation to find out how this was
    originally found. Answer in longform below in "answer", fill in the date in
    YYYY-MM-DD, and then determine if the vulnerability was found by a Google
    employee (you can tell from their email address). If it's clear that the
    vulenrability was discovered by a contest, fill in the name there.

    The "automated" flag can be true, false, or nil.
    The "google" flag can be true, false, or nil.

    If there is no evidence as to how this vulnerability was found, then you may
    leave the entries blank except for "answer". Write down where you looked in "answer".
  automated: false
description: "In Google Chrome there was an issue with merging certain CSS styles
  together.\nTheir old implementation serialized the CSS property value and then reparsed
  \nit which didn't preserve the name of the custom property. In their test example
  \nthe CSS that was causing the issue was '--A:var(---B)' and 'float:var(--C)' \nwhen
  applied to two spans.  When these styles were merged it would create a \ncase where
  the system could end up reading memory that wasn't allocated which \ncould result
  in a segmentation fault, which could be a denial of service.\n"
unit_tested:
  fix: true
  code: true
  answer: true
  question: |
    Were automated unit tests involved in this vulnerability?
    Was the original code unit tested, or not unit tested? Did the fix involve
    improving the automated tests?

    For the "code" answer below, look not only at the fix but the surrounding
    code near the fix and determine if and was there were unit tests involved
    for this module.

    For the "fix" answer below, check if the fix for the vulnerability involves
    adding or improving an automated test to ensure this doesn't happen again.
major_events:
  answer: |
    I saw in one of the commits that in WebCore they were trying to only
    expose the CSSOM API in CSSStyleDeclaration, they said they want "to split
    the CSSOM API from the internal implementation."
  events:
  - date: '2012-01-30'
    name: Trying split CSSOM API
  - date: 
    name: 
  question: |
    Please record any major events you found in the history of this
    vulnerability. Was the code rewritten at some point? Was a nearby subsystem
    changed? Did the team change?

    The event doesn't need to be directly related to this vulnerability, rather,
    we want to capture what the development team was dealing with at the time.
curation_level: 0
CWE_instructions: |
  Please go to cwe.mitre.org and find the most specific, appropriate CWE entry
  that describes your vulnerability. (Tip: this may not be a good one to start
  with - spend time understanding this vulnerability before making your choice!)
bounty_instructions: |
  If you came across any indications that a bounty was paid out for this
  vulnerability, fill it out here. Or correct it if the information already here
  was wrong. Otherwise, leave it blank.
interesting_commits:
  answer: 
  commits:
  - note: |
      Here they changed from using an iterator to using a for loop with an
      index. I think this is pretty interesting because in C++ there are so
      many different ways to do things at the language level and it's cool
      to see the conventions that big companies follow. It's odd that they
      changed something like this, maybe it was just the developer's
      preference.
    commit: d8055bceb97d14e28bdbce373062705ce080f014
  - note: 
    commit: 
  question: |
    Are there any interesting commits between your VCC(s) and fix(es)?

    Write a brief (under 100 words) description of why you think this commit was
    interesting in light of the lessons learned from this vulnerability. Any
    emerging themes?

    If there are no interesting commits, demonstrate that you completed this section by explaining what happened between the VCCs and the fix.
curated_instructions: |
  If you are manually editing this file, then you are "curating" it. Set the
  entry below to "true" as soon as you start. This will enable additional
  integrity checks on this file to make sure you fill everything out properly.
  If you are a student, we cannot accept your work as finished unless curated is
  set to true.
upvotes_instructions: |
  For the first round, ignore this upvotes number.

  For the second round of reviewing, you will be giving a certain amount of
  upvotes to each vulnerability you see. Your peers will tell you how
  interesting they think this vulnerability is, and you'll add that to the
  upvotes score on your branch.
announced_instructions: |
  Was there a date that this vulnerability was announced to the world? You can
  find this in changelogs, blogs, bug reports, or perhaps the CVE date. A good
  source for this is Chrome's Stable Release Channel
  (https://chromereleases.googleblog.com/).
  Please enter your date in YYYY-MM-DD format.
fixes_vcc_instructions: |
  Please put the commit hash in "commit" below (see my example in
  CVE-2011-3092.yml). Fixes and VCCs follow the same format.
description_instructions: |
  You can get an initial description from the CVE entry on cve.mitre.org. These
  descriptions are a fine start, but they can be kind of jargony.

  Rewrite this description in your own words. Make it interesting and easy to
  read to anyone with some programming experience. We can always pull up the NVD
  description later to get more technical.

  Try to still be specific in your description, but remove Chromium-specific
  stuff. Remove references to versions, specific filenames, and other jargon
  that outsiders to Chromium would not understand. Technology like "regular
  expressions" is fine, and security phrases like "invalid write" are fine to
  keep too.