CVE-2017-17855

CVE: CVE-2017-17855
CWE:
- 119
ipc:
  note: |
    BPF programs when loaded into the Linux kernel do not make use of IPC.
    They are loaded in memory and executed to filter/analyze network traffic.
  answer: false
  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.
CVSS: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
bugs: []
i18n:
  note: |
    The BPF verifier only checks to verify whether or not a BPF program is following
    proper memory allocation principles and is safe for the kernel to execute. It is
    not a feature about internationalization.
  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: |
    Vulnerability introduced with this commit on August 7, 2017.
    The verifier treats the pointer as an unknown scalar instead of stopping execution.
    Author Edward Cree made this behavior change because he thought that something
    might be able to be concluded about the result of the pointer.
  commit: f1174f77b50c94eecaa658fdc56fa69b421de4b8
- note: "This commit added the tracking of unsigned and signed min/max values to the
    verifier.\nIt is not a direct introduction of the vulnerability, but may have
    contributed to\nthe severity of it.\n \n \n"
  commit: b03c9f9fdc37dab81ea04d5dacdc5995d4c224c2
fixes:
- note: |
    Manually confirmed. This commit made it so that when a pointer is detected instead
    of a scalar, the method returns false (essentially saying that the program is not
    managing memory correctly).
  commit: 179d1c5602997fef5a940c6ddcf31212cbfebd14
vouch:
  note: |
    The actual commit that fixed the vulnerability was signed off by 2 other people besides the author:
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
  answer: true
  question: |
    Was there any part of the fix that involved one person vouching for
    another's work?

    This can include:
      * signing off on a commit message
      * mentioning a discussion with a colleague checking the work
      * upvoting a solution on a pull request

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of what your answer was.
bounty:
  amt: 
  url: 
  announced: 
lessons:
  yagni:
    note: |
      The commit that introduced this vulnerability was caused by a developer that thought something
      could be concluded still about a pointer's value when treated as a unknown scalar.
    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.
  serial_killer:
    note: 
    applies: false
  complex_inputs:
    note: 'The attacker can essential make use of complex inputs to access arbitrary
      memory locations.

      '
    applies: true
  distrust_input:
    note: |
      The BPF verifier receives input from the user indirectly. It has to verify user-created
      BPF programs. If the program makes use of pointers in areas where it should make use of
      scalars, it could result in this vulnerability.
    applies: true
  least_privilege:
    note: 
    applies: false
  native_wrappers:
    note: 
    applies: false
  defense_in_depth:
    note: 
    applies: false
  secure_by_default:
    note: 
    applies: false
  environment_variables:
    note: 
    applies: false
  security_by_obscurity:
    note: 
    applies: false
  frameworks_are_optional:
    note: 
    applies: false
reviews: []
sandbox:
  note: |
    The vulnerability did not result in a circumventing of any sandboxing or permissions.
    Consider https://www.cvedetails.com/cve/CVE-2017-17855/ which shows that authentication
    is not even required in order to exploit the vulnerability.
  answer: false
  question: |
    Did this vulnerability violate a sandboxing feature that the system
    provides?

    A sandboxing feature is one that allows files, users, or other features
    limited access. Vulnerabilities that violate sandboxes are usually based on
    access control, checking privileges incorrectly, path traversal, and the
    like.

    Answer should be true or false
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
upvotes: 6
CWE_note: |
  CWE as registered in the NVD. If you are curating, check that this
  is correct and replace this comment with "Manually confirmed".
mistakes:
  answer: |
    Vulnerability CVE-2017-17855 was the result of a planning error which led to a coding mistake.
    The developer who adjusted the BPF verifier so that it would accept and treat pointers as unknown
    scalars did not consider the full effects of his actions. He was too focused on the possibility
    of the BPF verifier gaining more knowledge about the pointer.
  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?

    There can, and usually are, many mistakes behind a vulnerability.

    Remember that mistakes can come in many forms:
    * slip: failing to complete a properly planned step due to inattention
              e.g. wrong key in the ignition
              e.g. using < instead of <=
    * lapse: failing to complete a properly planned step due to memory failure
              e.g. forgetting to put car in reverse before backing up
              e.g. forgetting to check null
    * planning error: error that occurs when the plan is inadequate
              e.g. getting stuck in traffic because you didn't consider the
                   impact of the bridge closing
              e.g. calling the wrong method
              e.g. using a poor design

    These are grey areas, of course. But do your best to analyze the mistakes
    according to this framework.

    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?

    Write a thoughtful entry here that people in the software engineering
    industry would find interesting.
nickname: 
subsystem:
  name: net
  note: |
    The BPF subsystem is used for packet filtering/analysis and loading custom BPF programs into the kernel.
    This explains why it is placed in the net subsystem.
  question: |
    What subsystems was the mistake in? These are WITHIN linux kernel

    Determining the subsystem is a subjective task. This is to help us group
     similar vulnerabilities, so choose a subsystem that other vulnerabilities would be in. Y

    Some areas to look for pertinent information:
      - Bug labels
      - Directory names
      - How developers refer to an area of the system in comments,
        commit messages, etc.

    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.

    Example linux kernel subsystems are:
      * drivers
      * crypto
      * fs
      * net
      * lib

    Name should be:
      * all lowercase English letters
      * NOT a specific file
      * can have digits, and _-@/

    Can be multiple subsystems involved, in which case you can make it an array
    e.g.
        name: ["subsystemA", "subsystemB"] # ok
        name: subsystemA # also ok
discovered:
  answer: |
    There is very little evidence of how this vulnerability was discovered.
    It is highly likely that a related vulnerability lead the developers to
    discover this vulnerability. This is considering
    https://bugs.chromium.org/p/project-zero/issues/detail?id=1454 which was linked
    to in the mailing list for the vulnerability. The link refers
    to a bug in the range tracking of the BPF system (the same system for which
    this vulnerability was found).
  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: true
discussion:
  note: |
    The following link is to the mailing list where comments added in the actual source code
    show what the programmer's thinking was behind the resolution to the vulnerability.
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=179d1c5602997fef5a940c6ddcf31212cbfebd14
  question: |
    Was there any discussion surrounding this?

    A discussion can include debates, disputes, or polite talk about how to
    resolve uncertainty.

    Example include:
      * Is this out of our scope?
      * Is this a security?
      * How should we fix this?

    Just because you see multiple comments doesn't mean it's a discussion.
    For example:
      * "Fix line 10". "Ok" is not what we call a discussion
      * "Ping" (reminding people)

    Check the bugs reports, pull requests, and mailing lists archives.

    These answers should be boolean.
      discussed_as_security: true or false
      any_discussion: true or false

    Put any links to disagreements you found in the notes section, or any other
    comment you want to make.
  any_discussion: true
  discussed_as_security: false
stacktrace:
  note: |
    I checked inside of the mailing list in the PoC section: https://www.openwall.com/lists/oss-security/2017/12/21/2
    I checked inside of nvd listing and its additional links: https://nvd.nist.gov/vuln/detail/CVE-2017-17855
  question: |
    Are there any stacktraces in the bug reports?

    Secondly, if there is a stacktrace, is the fix in the same file that the
    stacktrace points to?

    If there are no stacktraces, then both of these are false - but be sure to
    mention where you checked in the note.

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
  any_stacktraces: false
  stacktrace_with_fix: false
description: |
  A file inside the Linux kernel verifies whether or not a program is allowed to run.
  The file allows the program to make use of pointers in places where it
  should have been using scalars instead. This can lead to pointer leaks (which is when the
  reference to a place in memory is lost and thus cannot be freed or changed)
  and arbitrary code execution. Scalars aren't as prone to this issue because they are usually controlled
  and stored in a fixed memory location. Since pointers point to a specific address in memory and have
  direct access to memory addresses, they can be manipulated to change data outside of
  their intended memory boundaries.
unit_tested:
  fix: true
  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: |
    The mailing list for this vulnerability mentioned that there were added BPF
    selftests to trigger and test this vulnerability.
  code_answer: |
    Since the mailing list mentions added BPF selftests, there were no tests or
    insufficient tests to discover this vulnerability.
reported_date: 
specification:
  note: |
    There is no mention of a certain specification being violated throughout all major records
    of this vulnerability. CWE 119 was violated but isn't a specification.
  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
      * mailing lists
      * anything else

    The answer field should be boolean. In answer_note, please explain
    why you come to that conclusion.
announced_date: '2017-12-27'
curation_level: 2
published_date: '2017-12-27'
forgotten_check:
  note: |
    The fix for the vulnerability did not add any extra checks. Both the old code and the new code
    checked to see if a pointer was set for the value in the registery provided. However, the new code
    changed what happened when a pointer was found.
  answer: false
  question: |
    Does the fix for the vulnerability involve adding a forgotten check?

    A "forgotten check" can mean many things. It often manifests as the fix
    inserting an entire if-statement or a conditional to an existing
    if-statement. Or a call to a method that checks something.

    Example of checks can include:
      * null pointer checks
      * check the current role, e.g. root
      * boundary checks for a number
      * consult file permissions
      * check a return value

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
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: |
    I am saying true for this because the vulnerability is related to how the BPF verifier
    is tracking values when checking that a user-supplied BPF program runs safely/correctly.
    A fuzzer would just have to provide the BPF verifier with a BPF program that incorrectly
    uses pointers instead of scalars, resulting in a denial of service via pointer leaks.
  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.

  These are found by our tools by traversing the Git Blame history, where we
  determine which commit(s) introduced the functionality.

  Look up these VCC commits and verify that they are not simple refactorings,
  and that they are, in fact introducing the vulnerability into the system.
  Often, introducing the file or function is where the VCC is, but VCCs can be
  anything.

  Place any notes you would like to make in the notes field.
bugs_instructions: |
  What bugs are involved in this vulnerability?

  Please list bug IDs to https://bugzilla.kernel.org/

  Bug ID's can appear in several places:
    * Mentioned in commit messages
    * Mentioned in mailing list discussions
    * References from NVD entry
    * Various other places
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 required, but appreciated.
fixes_instructions: |
  Please put the commit hash in "commit" below.

  This must be a git commit hash from the systemd source repo, a  40-character
  hexademical string/

  Place any notes you would like to make in the notes field.
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: |
      I find it interesting that the values the BPF verifier could handle was expanded to include both
      signed and unsigned values at around the same time that the commit that caused the vulnerability was made.
      It may signal to yagni. Expanding capability of the BPF verifier and thus what types of BPF programs are
      approved to execute without considering the security implications.
    commit: b03c9f9fdc37dab81ea04d5dacdc5995d4c224c2
  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.

    Example interesting commits:
      * Mentioned as a problematic commit in the past
        e.g. "This fixes regression in commit xys"
      * A significant rewrite in the git history
      * Other commits that fixed a similar issue as this vulnerability
      * Anything else you find interesting.
order_of_operations:
  note: |
    I looked directly at the code for the fix and did not find any change in order of operations.
    The value of what the function returned was changed.
  answer: false
  question: |
    Does the fix for the vulnerability involve correcting an order of
    operations?

    This means the fix involves moving code around or changing the order of
    how things are done.

    Answer must be true or false.
    Write a note about how you came to the conclusions you did, regardless of
    what your answer was.
curated_instructions: |
  If you are manually editing this file, then you are "curating" it.

  Set the version number that you were given in your instructions.

  This will enable additional editorial 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 properly updated.
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