Open vSwitch’s Security Process¶
This is a proposed security vulnerability reporting and handling process for Open vSwitch. It is based on the OpenStack vulnerability management process described at https://wiki.openstack.org/wiki/Vulnerability_Management.
The OVS security team coordinates vulnerability management using the ovs-security mailing list. Membership in the security team and subscription to its mailing list consists of a small number of trustworthy people, as determined by rough consensus of the Open vSwitch committers on the ovs-committers mailing list. The Open vSwitch security team should include Open vSwitch committers, to ensure prompt and accurate vulnerability assessments and patch review.
We encourage everyone involved in the security process to GPG-sign their emails. We additionally encourage GPG-encrypting one-on-one conversations as part of the security process.
What is a vulnerability?¶
All vulnerabilities are bugs, but not every bug is a vulnerability. Vulnerabilities compromise one or more of:
- Confidentiality (personal or corporate confidential data).
- Integrity (trustworthiness and correctness).
- Availability (uptime and service).
Here are some examples of vulnerabilities to which one would expect to apply this process:
- A crafted packet that causes a kernel or userspace crash (Availability).
- A flow translation bug that misforwards traffic in a way likely to hop over security boundaries (Integrity).
- An OpenFlow protocol bug that allows a controller to read arbitrary files from the file system (Confidentiality).
- Misuse of the OpenSSL library that allows bypassing certificate checks (Integrity).
- A bug (memory corruption, overflow, ...) that allows one to modify the behaviour of OVS through external configuration interfaces such as OVSDB (Integrity).
- Privileged information is exposed to unprivileged users (Confidentiality).
If in doubt, please do use the vulnerability management process. At worst, the response will be to report the bug through the usual channels.
Step 1: Reception¶
To report an Open vSwitch vulnerability, send an email to the ovs-security mailing list (see contact at the end of this document). A security team member should reply to the reporter acknowledging that the report has been received.
Consider reporting the information mentioned in Reporting Bugs in Open vSwitch, where relevant.
Reporters may ask for a GPG key while initiating contact with the security team to deliver more sensitive reports.
The Linux kernel has its own vulnerability management process. Handling of vulnerabilities that affect both the Open vSwitch tree and the upstream Linux kernel should be reported through both processes. Send your report as a single email to both the kernel and OVS security teams to allow those teams to most easily coordinate among themselves.
Step 2: Assessment¶
The security team should discuss the vulnerability. The reporter should be included in the discussion (via “CC”) to an appropriate degree.
The assessment should determine which Open vSwitch versions are affected (e.g. every version, only the latest release, only unreleased versions), the privilege required to take advantage of the vulnerability (e.g. any network user, any local L2 network user, any local system user, connected OpenFlow controllers), the severity of the vulnerability, and how the vulnerability may be mitigated (e.g. by disabling a feature).
The treatment of the vulnerability could end here if the team determines that it is not a realistic vulnerability.
Step 3a: Document¶
The security team develops a security advisory document. The security team may, at its discretion, include the reporter (via “CC”) in developing the security advisory document, but in any case should accept feedback from the reporter before finalizing the document. When the document is final, the security team should obtain a CVE for the vulnerability from a CNA (https://cve.mitre.org/cve/cna.html).
The document credits the reporter and describes the vulnerability, including all of the relevant information from the assessment in step 2. Suitable sections for the document include:
* Title: The CVE identifier, a short description of the vulnerability. The title should mention Open vSwitch. In email, the title becomes the subject. Pre-release advisories are often passed around in encrypted email, which have plaintext subjects, so the title should not be too specific. * Description: A few paragraphs describing the general characteristics of the vulnerability, including the versions of Open vSwitch that are vulnerable, the kind of attack that exposes the vulnerability, and potential consequences of the attack. The description should re-state the CVE identifier, in case the subject is lost when an advisory is sent over email. * Mitigation: How an Open vSwitch administrator can minimize the potential for exploitation of the vulnerability, before applying a fix. If no mitigation is possible or recommended, explain why, to reduce the chance that at-risk users believe they are not at risk. * Fix: Describe how to fix the vulnerability, perhaps in terms of applying a source patch. The patch or patches themselves, if included in the email, should be at the very end of the advisory to reduce the risk that a reader would stop reading at this point. * Recommendation: A concise description of the security team's recommendation to users. * Acknowledgments: Thank the reporters. * Vulnerability Check: A step-by-step procedure by which a user can determine whether an installed copy of Open vSwitch is vulnerable. The procedure should clearly describe how to interpret the results, including expected results in vulnerable and not-vulnerable cases. Thus, procedures that produce clear and easily distinguished results are preferred. The procedure should assume as little understanding of Open vSwitch as possible, to make it more likely that a competent administrator who does not specialize in Open vSwitch can perform it successfully. The procedure should have minimal dependencies on tools that are not widely installed. Given a choice, the procedure should be one that takes at least some work to turn into a useful exploit. For example, a procedure based on "ovs-appctl" commands, which require local administrator access, is preferred to one that sends test packets to a machine, which only requires network connectivity. The section should say which operating systems it is designed for. If the procedure is likely to be specific to particular architectures (e.g. x86-64, i386), it should state on which ones it has been tested. This section should state the risks of the procedure. For example, if it can crash Open vSwitch or disrupt packet forwarding, say so. It is more useful to explain how to check an installed and running Open vSwitch than one built locally from source, but if it is easy to use the procedure from a sandbox environment, it can be helpful to explain how to do so. * Patch: If a patch or patches are available, and it is practical to include them in the email, put them at the end. Format them as described in :doc:`contributing/submitting-patches`, that is, as output by "git format-patch". The patch subjects should include the version for which they are suited, e.g. "[PATCH branch-2.3]" for a patch against Open vSwitch 2.3.x. If there are multiple patches for multiple versions of Open vSwitch, put them in separate sections with clear titles. Multiple patches for a single version of Open vSwitch, that must be stacked on top of each other to fix a single vulnerability, are undesirable because users are less likely to apply all of them correctly and in the correct order. Each patch should include a Vulnerability tag with the CVE identifier, a Reported-by tag or tags to credit the reporters, and a Signed-off-by tag to acknowledge the Developer's Certificate of Origin. It should also include other appropriate tags, such as Acked-by tags obtained during review.
CVE-2016-2074 is an example advisory document.
Step 3b: Fix¶
Steps 3a and 3b may proceed in parallel.
The security team develops and obtains (private) reviews for patches that fix the vulnerability. If necessary, the security team pulls in additional developers, who must agree to maintain confidentiality.
Step 4: Embargoed Disclosure¶
The security advisory and patches are sent to downstream stakeholders, with an embargo date and time set from the time sent. Downstream stakeholders are expected not to deploy or disclose patches until the embargo is passed.
A disclosure date is negotiated by the security team working with the bug submitter as well as vendors. However, the Open vSwitch security team holds the final say when setting a disclosure date. The timeframe for disclosure is from immediate (esp. if it’s already publicly known) to a few weeks. As a basic default policy, we expect report date to disclosure date to be 10 to 15 business days.
Operating system vendors are obvious downstream stakeholders. It may not be necessary to be too choosy about who to include: any major Open vSwitch user who is interested and can be considered trustworthy enough could be included. To become a downstream stakeholder, email the ovs-security mailing list.
If the vulnerability is already public, skip this step.
Step 5: Public Disclosure¶
When the embargo expires, push the (reviewed) patches to appropriate branches, post the patches to the ovs-dev mailing list (noting that they have already been reviewed and applied), post the security advisory to appropriate mailing lists (ovs-announce, ovs-discuss), and post the security advisory on the Open vSwitch webpage.
When the patch is applied to LTS (long-term support) branches, a new version should be released.
The security advisory should be GPG-signed by a security team member with a key that is in a public web of trust.