CVE-2011-2850

CVE: CVE-2011-2850
CWE:
- 125
bugs:
- 90134
repo: 
vccs:
- note: The fix occurs in a patch file so the best vcc I can find is that same patch
    file .
  commit: fd367aa0ef3e542ad63e6bb46d0c997b46e27a74
fixes:
- note: Google added a conditional to see if the characters are correctly being converted
    in a patch for Harfbuzz.
  commit: 7763a6a02fcd4479111530b64b9f6e00899aad2d
bounty:
  date: 
  amount: 
  references: []
lessons:
  yagni:
    note: 
    applies: 
  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: 
  complex_inputs:
    note: "This entire vulnerability had to do with the handling of Khmer characters,
      which is the official \nlanguage of Cambodia. Khmer characters are made of very
      unique symbols. This was able to be reproduced by exactly one \ncharacter which,
      when rendered using Harfbuzz, was rendered by two or more glyphs. '&#6068' was
      an \nexample character that would break Harfbuzz.\n"
    applies: true
  distrust_input:
    note: 
    applies: 
  least_privilege:
    note: 
    applies: 
  native_wrappers:
    note: 
    applies: 
  defense_in_depth:
    note: 
    applies: 
  secure_by_default:
    note: 
    applies: 
  environment_variables:
    note: 
    applies: 
  security_by_obscurity:
    note: 
    applies: 
  frameworks_are_optional:
    note: 
    applies: 
reviews:
- 7465036
- 7693034
upvotes: 15
mistakes:
  answer: "This seems like an issue that could have been caught earlier with improved
    testing. Harfbuzz itself \ncontains tests against a list of languages, Khmer originally
    not being one of them. Additionally, while \nit was eventually caught by their
    fuzzer, it existed for almost a year before a person or the fuzzer \ncaught this.
    With properly bounding unit tests they could have discovered the ease for OOB
    errors much \nearlier, especially when they can be caused by just a single character
    in Khmer or Tibetan.\n"
  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: '2011-09-19 08:02:56.060000000 -04:00'
subsystem:
  name: Harfbuzz
  answer: The subsystem I found is based on the components in the issue.
  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: 07-22-2011
  answer: 'The bug was found first by a google employee in Harfbuzz, and they also
    had a fuzzer which ''caught up'' and found the error as well.

    '
  google: true
  contest: false
  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: true
description: "Khmer characters were causing an out of bound error when being read.
  This out of bound \nerror was even being caused by a file made up of just one Khmer
  character. Khmer is not \na technical for certain characters, Khmer is actually
  the official language of Cambodia.\n\nAn attack taking advantage of this vulnerability
  would have remote attackers utilizing unspecified vectors \nto upload Khmer characters
  that would cause an out of bound error leading to denial of service.\n\nThe issue
  itself cropped up in the library they were using from Harfbuzz. Harfbuzz is used
  to convert unicode text to glyphs.\n"
unit_tested:
  fix: true
  code: false
  answer: 'The code was not obviously tested, but it had a new test case added to
    cover the added functionality for the fix.

    '
  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: 'There were no major events that seemed to be going on at the time, nothing
    too big or that seemed too complicated.

    '
  events:
  - date: 
    name: 
  - 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: 1
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: 'It seems that a similar thing happened again when reading Tibetan syllables
    a couple months later.

    '
  commits:
  - note: This is where they first notice the OOB caused by tibetan syllables.
    commit: b103b5975f6ac1b1b491510b8246091f160d9013
  - 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.