CVE-2018-20839

aka Flashing the goods

CVE: CVE-2018-20839
CWE: 372
ipc:
  note: "While this vulnerability was not caused by an issue with IPC, it \ndoes involve
    a system call to change the keyboard mode which was\nmismanaged\n"
  answer: true
  question: |
    Did the feature that this vulnerability affected use inter-process
    communication? IPC includes OS signals, pipes, stdin/stdout, message
    passing, and clipboard. Writing to files that another program in this
    software system reads is another form of IPC.

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
bugs:
- https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1803993
- https://github.com/systemd/systemd/pull/12378
i18n:
  note: This issue had to do with the incorrect checking of the keyboard mode, not
    i18n
  answer: false
  question: |
    Was the feature impacted by this vulnerability about internationalization
    (i18n)?

    An internationalization feature is one that enables people from all
    over the world to use the system. This includes translations, locales,
    typography, unicode, or various other features.

    Answer should be true or false
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
vccs:
- note: Discovered automatically by archeogit.
  commit: c83f349c5fd04c469e8227117b9cde6931c80ba5
- note: Discovered automatically by archeogit.
  commit: 042d7f5065c9c19b3f96804f9403b14d910e46d1
fixes:
- note: Discussion and git diff can be found here https://github.com/systemd/systemd/commit/9725f1a10f80f5e0ae7d9b60547458622aeb322f
  commit: 9725f1a10f80f5e0ae7d9b60547458622aeb322f
- note: 
  commit: 
vouch:
  note: "The pull request involved one developer checking over another's work \nand
    approving the changes after making tweaks/suggestions.\n"
  answer: true
  question: "Was there any part of the fix that involved one person vouching for \nanother's
    work?\n\nThis can include:\n  * signing off on a commit message\n  * mentioning
    a discussion with a colleague checking the work\n  * upvoting a solution on a
    pull request\n\nAnswer must be true or false.\nWrite a note about how you came
    to the conclusions you did, regardless of what your answer was.\n"
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: 
  verifying_state:
    note: |
      In class we have talked about verifying the state of the resource
      you are accessing, such as in the case of TOCTOU. While this issue
      was not an example of TOCTOU, the principle of verifying the resource
      still applies to this situation.
    applies: true
  defense_in_depth:
    note: 
    applies: 
  secure_by_default:
    note: 
    applies: 
  plain_text_passwords:
    note: "It is a very poor practice to store/manipulate passwords in plain text\nanywhere
      in a system. In this situation the developers were banking on\nthe fact that
      the virtual terminal should never be accessible by the \nuser, and when that
      fell through it created a gaping security hole.\n"
    applies: true
  environment_variables:
    note: 
    applies: 
  security_by_obscurity:
    note: 
    applies: 
  frameworks_are_optional:
    note: 
    applies: 
reviews: []
sandbox:
  note: This vulnerability concerns leaking sensitive data, not privileges or access
    control
  answer: false
  question: "Did this vulnerability violate a sandboxing feature that the system\nprovides?
    \n\nA sandboxing feature is one that allows files, users, or other features \nlimited
    access. Vulnerabilities that violate sandboxes are usually based on \naccess control,
    checking privileges incorrectly, path traversal, and the \nlike.\n\nAnswer should
    be true or false\nWrite a note about how you came to the conclusions you did,
    regardless of\nwhat your answer was.\n"
upvotes: 15
CWE_note: 
mistakes:
  answer: "I would categorize this vulnerability as a planning error associated with
    \ndesign. It was not fully considered what states the keyboard could be in \nthat
    could be compromised by blindly resetting/changing the mode.\n"
  question: "In your opinion, after all of this research, what mistakes were made
    that\nled to this vulnerability? Coding mistakes? Design mistakes?\nMaintainability?
    Requirements? Miscommunications?\n\nThere can, and usually are, many mistakes
    behind a vulnerability.\n\nRemember that mistakes can come in many forms:\n* slip:
    failing to complete a properly planned step due to inattention\n          e.g.
    wrong key in the ignition\n          e.g. using < instead of <=\n* lapse: failing
    to complete a properly planned step due to memory failure\n          e.g. forgetting
    to put car in reverse before backing up\n          e.g. forgetting to check null\n*
    planning error: error that occurs when the plan is inadequate\n          e.g.
    getting stuck in traffic because you didn’t consider the \n               impact
    of the bridge closing\n          e.g. calling the wrong method\n          e.g.
    using a poor design\n\nThese are grey areas, of course. But do your best to analyze
    the mistakes \naccording to this framework.\n\nLook at the CWE entry for this
    vulnerability and examine the mitigations\nthey have written there. Are they doing
    those? Does the fix look proper?\n\nWrite a thoughtful entry here that people
    in the software engineering\nindustry would find interesting.\n"
nickname: Flashing the goods
subsystem:
  name:
  - basic
  - vconsole
  note: Basic does not appear to be a specific subsystem, but rather a collection
    of basic utilities.
  question: "What subsystems was the mistake in? These are subsystems WITHIN systemd\n\nTwo
    areas to look:\n  - Bug labels\n  - Directory names\n\nLook at the path of the
    source code files code that were fixed to get\ndirectory names. Look at comments
    in the code. Look at the bug reports how\nthe bug report was tagged. \n\nExample
    systemd subsystems are:\n  * fsck\n  * apparmor\n  * fstab\n  * sd-daemon\n\nName
    should be:\n  * all lowercase English letters\n  * NOT a specific file\n  * can
    have digits, and _-@/\n\nCan be multiple subsystems involved, in which case you
    can make it an array\ne.g.\n    name: [\"subsystemA\", \"subsystemB\"] # ok\n
    \   name: subsystemA # also ok\n"
discovered:
  answer: |
    This was found on 2018-11-19. It does not appear that the person that
    discovered the vulnerability was a developer, but rather a Ubuntu user.
  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, contest, and developer flags can be true, false, or nil.

    If there is no evidence as to how this vulnerability was found, then please
    explain where you looked.
  automated: false
  developer: false
discussion:
  note: "In the original bug report once the vulnerability's existence was confirmed
    it \nwas marked as high importance. While security wasn't explicitly mentioned,
    it was referred\nto as a large issue for \"obvious reasons\" so it's fair to say
    that the discussion\nsurrounding this vulnerability was focused on restoring the
    security of user's\npasswords.\n\nAdditionally, in the pull request for the fix
    to this vulnerability there was some \ndiscussion about where exactly the checks
    to verify the keyboard mode should be placed\nto make the most sense from a design
    perspective.\n"
  question: "Was there any discussion surrounding this?\n\nA discussion can include
    debates, disputes, or polite talk about how to \nresolve uncertainty.\n\nExample
    include:\n  * Is this out of our scope?\n  * Is this a security?\n  * How should
    we fix this?\n\nJust because you see multiple comments doesn't mean it's a discussion.
    \nFor example:\n  * \"Fix line 10\". \"Ok\" is not what we call a discussion\n
    \ * \"Ping\" (reminding people)\n\nCheck the bugs reports, pull requests, and
    mailing lists archives.\n\nThese answers should be boolean.\n  discussed_as_security:
    true or false\n  any_discussion: true or false\n\nPut any links to disagreements
    you found in the notes section, or any other\ncomment you want to make.\n"
  any_discussion: true
  discussed_as_security: true
stacktrace:
  note: |
    There were no stacktraces provided as this vulnerability did not result in
    errors being thrown at any stage in the process.

    In the bug report there was output showing the status of the keyboard mode,
    which helped identify the issue, but this is not technically a stacktrace.
  question: "Are there any stacktraces in the bug reports? \n\nSecondly, if there
    is a stacktrace, is the fix in the same file that the \nstacktrace points to?
    \n\nIf there are no stacktraces, then both of these are false - but be sure to\nmention
    where you checked in the note.\n\nAnswer must be true or false.\nWrite a note
    about how you came to the conclusions you did, regardless of\nwhat your answer
    was.\n"
  any_stacktraces: false
  stacktrace_with_fix: false
description: "Systemd mishandled the check to the current keyboard mode which resulted
  in \nthe mode of the virtual terminal being changed when a user logged out. \n\nThis
  would allow a user with any level of privilege to briefly \nview passwords in cleartext
  displayed on the terminal console under \nspecific circumstances such as watching
  a shutdown or switching back and\nforth between the first console and a terminal
  window (easily achievable\nwith the keyboard shortcuts Ctrl-Alt-F1 and Ctrl-Alt-F2).\n\nThe
  fix for this vulnerability involved verifying the current keyboard\nmode before
  changing it.\n"
unit_tested:
  fix: false
  code: false
  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 code: and fix: - your answer should be boolean.

    For the code_answer below, look not only at the fix but the surrounding
    code near the fix in related directories and determine if and was there were
    unit tests involved for this subsystem.

    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.
  fix_answer: Looked at commits around that time
  code_answer: |
    Looked at the directory at the time of the commit and there were unit tests,
    but it does not appear that this issue was tested for. Additionally, a new
    test was not added with the fix.
reported_date: '2018-11-19'
specification:
  note: No mentioned specifications in any of the above resources
  answer: false
  instructions: |
    Is there mention of a violation of a specification? For example, the POSIX
    spec, an RFC spec, a network protocol spec, or some other requirements
    specification.

    Be sure to check the following artifacts for this:
      * bug reports
      * security advisories
      * commit message
      * pull request
      * mailing lists
      * anything else

    The answer field should be boolean. In answer_note, please explain
    why you come to that conclusion.
announced_date: '2019-05-16'
curation_level: 1
published_date: '2019-05-17'
forgotten_check:
  note: This vulnerability is centered around a mishandled check to the keyboard mode.
  answer: true
  question: "Does the fix for the vulnerability involve adding a forgotten check?\n\nA
    \"forgotten check\" can mean many things. It often manifests as the fix \ninserting
    an entire if-statement or a conditional to an existing \nif-statement. Or a call
    to a method that checks something.\n\nExample of checks can include:\n  * null
    pointer checks\n  * check the current role, e.g. root\n  * boundary checks for
    a number\n  * consult file permissions\n  * check a return value\n\nAnswer must
    be true or false.\nWrite a note about how you came to the conclusions you did,
    regardless of\nwhat your answer was.\n"
CWE_instructions: |
  Please go to http://cwe.mitre.org and find the most specific, appropriate CWE
  entry that describes your vulnerability. We recommend going to
  https://cwe.mitre.org/data/definitions/699.html for the Software Development
  view of the vulnerabilities. We also recommend the tool
  http://www.cwevis.org/viz to help see how the classifications work.

  If you have anything to note about why you classified it this way, write
  something in CWE_note. This field is optional.

  Just the number here is fine. No need for name or CWE prefix. If more than one
  apply here, then place them in an array like this
    CWE: ["123", "456"] # this is ok
    CWE: [123, 456]     # also ok
    CWE: 123            # also ok
autodiscoverable:
  note: "While unlikely, since there are no special permissions required, \nit is
    possible that a fuzzer running with a basic user account could\nperform the actions
    required to experience this vulnerability \nand check to see that sensitive data
    was leaked.\n"
  answer: true
  instructions: |
    Is it plausible that a fully automated tool could have discovered
    this? These are tools that require little knowledge of the domain,
     e.g. automatic static analysis, compiler warnings, fuzzers.

    Examples for true answers: SQL injection, XSS, buffer overflow

    In systemd, the actually use OZZ Fuzz. If there's a link to it, add it here.

    Examples for false: RFC violations, permissions issues, anything
    that requires the tool to be "aware" of the project's
    domain-specific requirements.

    The answer field should be boolean. In answer_note, please explain
    why you come to that conclusion.
vcc_instructions: "The vulnerability-contributing commits.\n\nThese are found by our
  tools by traversing the Git Blame history, where we \ndetermine which commit(s)
  introduced the functionality. \n\nLook up these VCC commits and verify that they
  are not simple refactorings, \nand that they are, in fact introducing the vulnerability
  into the system. \nOften, introducing the file or function is where the VCC is,
  but VCCs can be \nanything. \n\nPlace any notes you would like to make in the notes
  field.\n"
bugs_instructions: "What bugs and/or pull requests are involved in this vulnerability?
  \n\nFor systemd, this is typically their GitHub issues, but could also include \nbugs
  from other databases. Put a URL instead of a single number.\n"
yaml_instructions: |
  =================
  ===YAML Primer===
  =================
  This is a dictionary data structure, akin to JSON.
  Everything before a colon is a key, and the values here are usually strings
  For one-line strings, you can just use quotes after the colon
  For multi-line strings, as we do for our instructions, you put a | and then
  indent by two spaces

  For readability, we hard-wrap multi-line strings at 80 characters. This is
  not absolutely required, but appreciated.
fixes_instructions: "Please put the commit hash in \"commit\" below.\n\nThis must
  be a git commit hash from the systemd source repo, a  40-character \nhexademical
  string/\n\nPlace any notes you would like to make in the notes field.\n"
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:
  commits:
  - note: 
    commit: 
  - note: 
    commit: 
  question: |
    Are there any interesting commits between your VCC(s) and fix(es)?

    Use this to specify any commits you think are notable in some way, and
    explain why in the note.
order_of_operations:
  note: This vulnerability concerned correcting the check, not performing operations
    in a different order.
  answer: false
  question: "Does the fix for the vulnerability involve correcting an order of \noperations?\n\nThis
    means the fix involves moving code around or changing the order of \nhow things
    are done. \n\nAnswer must be true or false.\nWrite a note about how you came to
    the conclusions you did, regardless of\nwhat your answer was.\n"
curated_instructions: "If you are manually editing this file, then you are \"curating\"
  it. \n\nSet the version number that you were given in the instructions. \n \nThis
  will enable additional editorial checks on this file to make sure you \nfill everything
  out properly. If you are a student, we cannot accept your work\nas finished unless
  curated is properly updated. \n"
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.
nickname_instructions: |
  A catchy name for this vulnerability that would draw attention it.
  If the report mentions a nickname, use that.
  Must be under 30 characters. Optional.
reported_instructions: |
  What date was the vulnerability reported to the security team? Look at the
  security bulletins and bug reports. It is not necessarily the same day that
  the CVE was created.  Leave blank if no date is given.

  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 date.

  This is not the same as published date in the NVD - that is below.

  Please enter your date in YYYY-MM-DD format.
published_instructions: |
  Is there a published fix or patch date for this vulnerability?
  Please enter your date in YYYY-MM-DD 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 project-specific
  stuff. Remove references to versions, specific filenames, and other jargon
  that outsiders to this project would not understand. Technology like "regular
  expressions" is fine, and security phrases like "invalid write" are fine to
  keep too.

  Your target audience is people just like you before you took any course in
  security