CVE-2014-0095

aka Content Length 0 Hangs

CVE: CVE-2014-0095
CWE: 754
bugs: []
vccs:
- note: SVN rev 1519838, from the Tomcat website.
  commit: b7d9a0540a89d08f6f3682bdfa1de19584368186
fixes:
- note: SVN rev 1578392, from the Tomcat website.
  commit: 8884dae60ace77a87ed9385442ce429e98c3a479
bounty:
  amt: 
  url: 
  announced: 
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: 
    applies: 
  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: 
upvotes: 2
mistakes:
  answer: |
    As far as I can tell, this vulnerability is triggered by normal use of the
    system, not abuse or even misuse of it. It can simply manifest in normal
    use, and it happens to be an accidental DOS. Thus, better application of
    security checking would quite possibly not have prevented, discovered, or
    fixed the vulnerability.
    I can only see two mistakes here. The first is that the case of content
    length being zero was apparently not correctly checked in the VCC. The
    second, and in my opinion more interesting, mistake is that a unit test for
    that case was never made. While the first mistake is just a standard coding
    error that's mostly unavoidable, the second seems like it was an important
    detail that was overlooked. Perhaps a code review would have caught this
    mistake.
    There are two preemtive mitigations for the CWE that could have been
    helpful. If implemented, "ensure that the program fails gracefully" or "use
    system limits" would make the error more noticable while also making it not
    consume an entire thread. It would still result in a bug that would need to
    be fixed, but that bug would not be an exploitable DOS vulnerability.
  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.
nickname: Content Length 0 Hangs
reported: '2014-03-03'
announced: '2014-05-27'
subsystem:
  name: ajp
  answer: The AJP request processor
  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: '2014-03-03'
  answer: |
    A user happened across the bug during normal use of Tomcat. He then emailed
    the tomcat-users mailing list about it.
  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
    * If it's clear that the vulnerability was discovered by a contest,
      fill in the name there.
    * The "automated" 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", BUT please write down
    where you looked in "answer".
  automated: false
description: |
  If Content-Length is explicitly set to 0 in a particular type of request, the
  thread handling that request will hang.
unit_tested:
  fix: true
  code: true
  answer: |
    The original code was unit tested, but they did not catch the
    vulnerability. The commit that fixed the vulnerability also added new
    unit tests to verify that the vulnerability was resolved.
  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?
    Write the reasoning behind your answer in the "answer" field.
    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. Must be just "true" or "false".
    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.
    Must be just "true" or "false".
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!)
incomplete_fixes:
- note: 
  commit: 
- note: 
  commit: 
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: |
    No interesting commits. There were 1175 commits in total between the VCC
    and the fix, of which only 6 changed the relevant file. All 6 of them were
    before the vulnerability was reported, and they were unrelated to it.
  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: |
  Students: when initially writing this, ignore this upvotes number.
  Once this work is being reviewed, 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.
nickname_instructions: |
  Nickname is optional. Provide a useful, professional, and catchy nickname for
  this vulnerability. Ideally fewer than 30 characters. This will be shown
  alongside its CVE to make it more easily distinguished from the rest.
reported_instructions: |
  Was there a date that this vulnerability was reported to the team? You can
  find this in changelogs, blogs, bug reports, or perhaps the CVE data.
  Please enter your date in YYYY-MM-DD format.
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 data.
  Please enter your date in YYYY-MM-DD format.
fixes_vcc_instructions: |
  Please put the Git commit SHA in "commit" below, and any notes about how this
  was discovered in the "note" field.
  Refer to our instructions on how to find a Git SHA from an SVN revision.
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.
incomplete_fix_instructions: |
  Did the above "fixes" actually fix the vulnerability?
  Please list any fix commits for this vulnerability that had to be corrected
  at a later date.