CVE-2015-1224

CVE: CVE-2015-1224
CWE:
- 17
- 125
bugs:
- 449958
repo: 
vccs:
- note: 'This commit added functionality to support playback of VP8 Alpha Video Streams

    '
  commit: 6ac955b41814da1eebf56244a147f3fad00f5aa7
fixes:
- note: ''
  commit: c1a91a8a6a7132c47a174054f0fb56cc3dc8c069
bounty:
  date: '2015-03-03'
  amount: 2000.0
  references:
  - http://chromereleases.googleblog.com/2015/03/stable-channel-update.html
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: 
  complex_inputs:
    note: 
    applies: 
  distrust_input:
    note: 'The team didn''t look for the possibility that someone could try to stream
      a video with an alpha buffer that was larger than the image buffer.

      '
    applies: true
  least_privilege:
    note: 
    applies: 
  native_wrappers:
    note: 
    applies: 
  defense_in_depth:
    note: 
    applies: 
  secure_by_default:
    note: 
    applies: false
  environment_variables:
    note: 
    applies: false
  security_by_obscurity:
    note: 
    applies: false
  frameworks_are_optional:
    note: 
    applies: 
reviews:
- 858303002
- 881533002
upvotes: 5
mistakes:
  answer: |
    This vulnerability was a bit of a miscommunication and design mistake. Initially, they did have support for video streams with alpha buffers larger than the image buffer, but the library changed a year after the first implementation and introduced this vulnerability. They didn't account for that and this vulnerability was introduced.

    The code written to copy video data from the buffer assumed that the image and alpha plane had the same dimensions and stride (buffer width). According to the video format, the dimensions must be the same, so the writer of the code assumed valid input without doing a check. When a video plane's dimensions differed from the alpha plane, the stride was also different. The code to copy the alpha plane used the stride from the video plane, so the incorrect amount of data was read, causing the overflow. Interestingly, the strides of the video and alpha planes can differ even if they have the same dimensions. This means that a buffer reading issue may occur even with a valid VP8 video. The reviewers of the bug noticed this issue, and it was fixed along with the dimension check.

    To check for malformed VP8 data, they added a check that threw an error if the alpha plane dimensions were different than the image plane. This fix adds input validation, which is the primary mitigation listed on the CWE-125 page.
  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: '2015-03-08'
subsystem:
  name: VPx Video Decoder
  answer: Based off CVE report, bug blog, and commit messages
  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: '2015-01-19'
  answer: Credited to Aki Helin of OUSPG, which is an university secure programming
    group.
  google: false
  contest: 
  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: 'An image decoder does not ensure that alpha-plane dimensions are identical
  to image dimensions. This allows a remote attacker to cause a denial of service
  attack through an out-of-bounds read.

  '
unit_tested:
  fix: true
  code: true
  answer: |
    They had regression unit tests that checked this and surrounding code. They
    did not improve any existing tests to fix this, but they did create a new one
    to check 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 was one major event where the library used for decoding changed.  It
    resulted in a large insertion to the code
  events:
  - date: '2014-02-20'
    name: Library change
  - 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: 
  commits:
  - note: |
      It was a large addition of code to support a new feature, but it depended on
      a few changes in a library that hadn't been rolled out yet. It was reverted a
      day later re-committed five days later.
    commit: f5b70fe9d9e565895111999682ac11c8ae191318
  - 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.