CVE-2015-1282

CVE: CVE-2015-1282
CWE:
- 415
bugs:
- 487928
repo: https://chromium.googlesource.com/chromium/
vccs:
- note: |
    This bug has existed longer than Google's PDFium was open source.
    This is the initial commit for PDFium. A pointer is Document::DofieldDelay
    was not being deleted safely and would cause AddressSanitizer to go off.
  commit: 
fixes:
- note: |
    This is the actual fix. Previously some revisions related to updating version
    numberes were incorrectly flagged. The code review was made private by the submitter.
    Bouty was $3000 for the find and $1337 for the fix. The fix envolves delaying the
    freeing of pointer by copying them into an array to prevent use-after-free issues.
  commit: 
bounty:
  date: '2015-08-17'
  amount: 4337.0
  references:
  - https://bugs.chromium.org/p/chromium/issues/detail?id=487928#c36
lessons:
  yagni:
    note: See comments in least privilege section.
    applies: true
  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.
  fail_securely:
    note: "The interesting tidbit is that this vulnerability was actually exploiting
      code designed to\nfail securely. When free() was called twice in Chromium, the
      application would automatically\nterminate to prevent memory errors (ie. failing
      securely). However, what the developers\ndid not consider was that purposely
      invoking free() consecutively would allow arbitrary code\nto crash the browser.
      \n"
    applies: true
  serial_killer:
    note: 
    applies: 
  complex_inputs:
    note: 
    applies: 
  distrust_input:
    note: "Vulnerability is only exploitable by PDF files. PDFs should be considered\nuntrusted
      input, since their contents are unverified until they are opened.\n\nAllowing
      Javascript in PDF's is an inherent vulnerability in and of itself. \nOne good
      coding principal is to sandbox any executing Javascript as much as possible,
      \ndue to the high probability that a userwill open a malicious PDF.\n"
    applies: true
  least_privilege:
    note: "Reducing the capabilites of the JavaScript API in PDF's as much as possible
      is a \nmitigation that should be considered. This could fall in line with YAGNI
      - \nAdobe (the makers of the PDF standard) should look at how much of the JS
      API is \nactually needed for a good average user experience.\n"
    applies: true
  native_wrappers:
    note: |
      Crash could be caused in JavaScript by exploiting Chrome's PDF engine
      by causing a memory problem only present in unmanaged languages.
    applies: true
  defense_in_depth:
    note: Chrome's AddressSanitizer caught a bad memory operation and forced the application
      to crash before any damage could be done.
    applies: true
  secure_by_default:
    note: 
    applies: 
  environment_variables:
    note: 
    applies: 
  security_by_obscurity:
    note: 
    applies: 
  frameworks_are_optional:
    note: 
    applies: 
reviews:
- 1159433007
- 1223163004
- 1162103004
upvotes: 
mistakes:
  answer: "The mistake was a design mistake and a coding mistake. One thing the developers
    did well was\nthat they followed the fail securely principal. Freeing a pointer
    twice could cause undeterministic\noutcomes - as a result it is best to terminate
    when such an error occurs. However, most people\ndo not consider a vulnerability
    fix or good coding practice to also something that can be exploited\nfor malicious
    purposes. That was the case in this scenario. Knowing a foolproof mechanism to\ncrash
    the browser lead to malicious PDF's that could simply invoke that failsafe over
    and over - \nwriting a PDF that forced the browser to free a pointer twice, intentionally
    crashing it.\n\nOne potential solution that could be considered is to forbid Javascript
    in PDF's entirely - JS\nin PDF's is an enormous security risk by itself that there
    should be debate whether or not the benefit\nof having a Javascript API is worth
    the security headaches. A mitigation is to restrict the JS API \nin Acrobat API
    to prevent attacks as much as possible. The difficulty in this approach is the
    need\nto maintain security while not reducing the API so much that it is no longer
    useful to users.\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: '2015-07-22'
subsystem:
  name: pdf
  answer: PDFium (Internals>Plugins>PDF)
  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: '2015-05-14'
  answer: "This vulnerability was discovered by a user. That same user also submitted
    the fix\nfor the vulnerability. No information was available on the user's profile.
    The user\ndid not provide a name. \n\nThe user had an example PDF (attached in
    the bug report) which exploited the vulnerability, \nand tested the fix by using
    the same PDF. Example PDFs are blank PDF documents with\nJavaScript code embedded
    within them.\n\nThe code review for the bug was private.\n"
  google: false
  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: false
description: "In Chromium, PDF's are handled by an open sourced library called PDFium.
  PDFium\nwas developed along with Chromium, however the library remained closed source
  until 2014.\nThis vulnerability was discovered in 2015.\n\nAdobe (the creators of
  the PDF standards) includes a Javascript API that can allow\nPDF's to embed and
  execute JavaScript code in order to enhance a PDF's functionality. For ex,\nPDF's
  that include buttons are typically written with Javascript code. \n\nThis vulnerability
  allows a \"crafted\" PDF (term taken from Chromium bug report) that \ncontains specific
  Javascript code to crash the browser. Javascript code can cause\nthe delay() and
  doFieldDelay() functions in Document.cpp to call free() twice. This vulnerability
  \nis caused by javascript causing the PDFium (PDF) engine to enter a method, multiple
  times by \ncausing document level and field level JavaScript to interact using the
  field.delay property.\nThis would free a previously freed pointer. This results
  in a denial of service attack, \nsince Chromium defaults to crashing if it detects
  a use-after-free bug. \n"
unit_tested:
  fix: true
  code: true
  answer: |
    New vulnerability specific unit tests were added to test the vulnerability
    after it had been discovered. The code in question had been a part of a unit
    test, but the unit tests did not catch the vulnerability. The improvements included
    two new test pdf files that targeted this vulnerability specifically.
  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: 
  events:
  - date: '2015-07-27'
    name: Stagefright Discovery
  - 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 appears that this vulnerability had existed in PDFium within Chromium for a significant period of
    time. PDFium started off as a closed source project before being open-sourced in June 2014. This vulnerability
    was discovered approximately 13 months later in July 2015. According to git blame, the code in question was written
    before PDFium was open-sourced, making it impossible to trace the origins of the vulnerability. There were no changes
    to the lines of code in question during the 13 months between open source and discovery. Therefore, there are no remarkable
    commits to note.
  commits:
  - note: 
    commit: 
  - 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.