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docs: add security non-events

docs/security/non-events.md

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+<!--[metadata]>
++++
+title = "Docker Security Non-events"
+description = "Review of security vulnerabilities Docker mitigated"
+keywords = ["Docker, Docker documentation,  security, security non-events"]
+[menu.main]
+parent = "smn_secure_docker"
+weight =-99
++++
+<![end-metadata]-->
+
+# Docker Security Non-events
+
+This page lists security vulnerabilities which Docker mitigated, such that
+processes run in Docker containers were never vulnerable to the bug—even before
+it was fixed. This assumes containers are run without adding extra capabilities
+or not run as `--privileged`.
+
+The list below is not even remotely complete. Rather, it is a sample of the few
+bugs we've actually noticed to have attracted security review and publicly
+disclosed vulnerabilities. In all likelihood, the bugs that haven't been
+reported far outnumber those that have. Luckily, since Docker's approach to
+secure by default through apparmor, seccomp, and dropping capabilities, it
+likely mitigates unknown bugs just as well as it does known ones.
+
+Bugs mitigated:
+
+* [CVE-2013-1956](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1956),
+[1957](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1957),
+[1958](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1958),
+[1959](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1959),
+[1979](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1979),
+[CVE-2014-4014](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-4014),
+[5206](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-5206),
+[5207](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-5207),
+[7970](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-7970),
+[7975](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-7975),
+[CVE-2015-2925](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2925),
+[8543](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-8543),
+[CVE-2016-3134](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-3134),
+[3135](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-3135), etc.:
+The introduction of unprivileged user namespaces lead to a huge increase in the
+attack surface available to unprivileged users by giving such users legitimate
+access to previously root-only system calls like `mount()`. All of these CVEs
+are examples of security vulnerabilities due to introduction of user namespaces.
+Docker can use user namespaces to set up containers, but then disallows the
+process inside the container from creating its own nested namespaces through the
+default seccomp profile, rendering these vulnerabilities unexploitable.
+* [CVE-2014-0181](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0181),
+[CVE-2015-3339](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-3339):
+These are bugs that require the presence of a setuid binary. Docker disables
+setuid binaries inside containers via the `NO_NEW_PRIVS` process flag and
+other mechanisms.
+* [CVE-2014-4699](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-4699):
+A bug in `ptrace()` could allow privilege escalation. Docker disables `ptrace()`
+inside the container using apparmor, seccomp and by dropping `CAP_PTRACE`.
+Three times the layers of protection there!
+* [CVE-2014-9529](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-9529):
+A series of crafted `keyctl()` calls could cause kernel DoS / memory corruption.
+Docker disables `keyctl()` inside containers using seccomp.
+* [CVE-2015-3214](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-3214),
+[4036](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-4036): These are
+bugs in common virtualization drivers which could allow a guest OS user to
+execute code on the host OS. Exploiting them requires access to virtualization
+devices in the guest. Docker hides direct access to these devices when run
+without `--privileged`. Interestingly, these seem to be cases where containers
+are "more secure" than a VM, going against common wisdom that VMs are
+"more secure" than containers.
+* [CVE-2016-0728](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0728):
+Use-after-free caused by crafted `keyctl()` calls could lead to privilege
+escalation. Docker disables `keyctl()` inside containers using the default
+seccomp profile.
+* [CVE-2016-2383](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-2383):
+A bug in eBPF -- the special in-kernel DSL used to express things like seccomp
+filters -- allowed arbitrary reads of kernel memory. The `bpf()` system call
+is blocked inside Docker containers using (ironically) seccomp.
+
+Bugs *not* mitigated:
+
+* [CVE-2015-3290](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-3290),
+[5157](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-5157): Bugs in
+the kernel's non-maskable interrupt handling allowed privilege escalation.
+Can be exploited in Docker containers because the `modify_ldt()` system call is
+not currently blocked using seccomp.