Nix(OS) vulnerability scanner

This is a utility that validates a Nix store for any packages that are reachable from live paths and likely to be affected by vulnerabilities listed in the NVD.

It implements a CLI utility to inspect the current status and a monitoring integration for Sensu.

Example output

2 derivations with active advisories

------------------------------------------------------------------------
binutils-2.31.1

/nix/store/zc1lbkaf9l9hlsp1jdiq3si56nsglymh-binutils-2.31.1.drv
CVE                                                CVSSv3
https://nvd.nist.gov/vuln/detail/CVE-2018-1000876  7.8
https://nvd.nist.gov/vuln/detail/CVE-2018-20657    7.5
https://nvd.nist.gov/vuln/detail/CVE-2018-20712    6.5

------------------------------------------------------------------------
libssh2-1.9.0

/nix/store/mfpfclry68r4sv4mcc9hb88z0lb9jk1c-libssh2-1.9.0.drv
CVE                                                CVSSv3
https://nvd.nist.gov/vuln/detail/CVE-2019-17498    8.1

Theory of operation

vulnix pulls all published CVEs from NIST and caches them locally. It matches name and version of all derivations referenced from the command line against known CVE entries. A whitelist is used to filter out unwanted results.

Matching Nix package names to NVD products is currently done via a coarse heuristic. First, a direct match is tried. If no product can be found, variations with lower case and underscore instead of hyphen are tried. It is clear that this mapping is too simplistic and needs to be improved in future versions.

System requirements

• Depends on common Nix tools like nix-store. These are expected to be in $PATH.
• Depends on being able to interact with the Nix store database (/nix/var/nix/db). This means that it must either run as the same user that owns the Nix store database or nix-daemon must be active.
• Parses *.drv files directly. Tested with Nix >=1.10 and 2.x.
• It refuses to work without some locale environment settings. Try export LANG=C.UTF-8 if you see encoding errors.

Usage Example

• What vulnerabilities are listed for my current system

vulnix --system

• Check nix-build output together with its transitive closure

vulnix result/

• Check all passed derivations, but don't determine requisites

vulnix -R /nix/store/*.drv

• JSON output for machine post-processing

vulnix --json /nix/store/my-derivation.drv

See vulnix --help for a list of all options.

Whitelisting

vulnix output may contain false positives, unfixable packages or stuff which is known to be addressed. The whitelist feature allows to exclude packages matching certain criteria.

Usage

Load whitelists from either local files or HTTP servers

vulnix -w /path/to/whitelist.toml \
       -w https://example.org/published-whitelist.toml

Syntax

Whitelists are TOML files which contain the package to be filtered as section headers, followed by further per-package options.

Section headings - package selection

Exclude a package at a specific version

["openjpeg-2.3.0"]

Exclude a package regardless of version (additional CVE filters may apply, see below)

["openjpeg"]

Exclude all packages (see below for CVE filters, again)

["*"]

Options

cve

List of CVE identifiers to match. The whitelist rule is valid as long as the detected CVEs are a subset of the CVEs listed here. If additional CVEs are detected, this whitelist rule is not effective anymore.

until

Date in the form "YYYY-MM-DD" which confines this rule's lifetime. On the specified date and later, this whitelist rule is not effective anymore.

issue_url

URL or list of URLs that point to any issue tracker. Informational only.

comment

String or list of strings containing free text. Informational only.

Examples

Create a ticket on your favourite issue tracker. Estimate the time to get the vulnerable package fixed. Create whitelist entry:

["ffmpeg-3.4.2"]
cve = ["CVE-2018-6912", "CVE-2018-7557"]
until = "2018-05-01"
issue_url = "https://issues.example.com/29952"
comment = "need to backport patch"

This particular version of ffmpeg will be left out from reports until either another CVE gets published or the specified date is reached.

CVE patch auto-detection

vulnix will inspect derivations for patches which supposedly fix specific CVEs. When a patch filename contains one or more CVE identifiers, these will not reported anymore. Example Nix code:

{
  patches = [ ./CVE-2018-6951.patch ];
}

Patches which fix multiple CVEs should name them all with a non-numeric separator, e.g. CVE-2017-14159+CVE-2017-17740.patch.

Auto-detection even works when patches are pulled via fetchpatch and friends as long as there is a CVE identifier in the name. Example:

{
  patches = [
    (fetchpatch {
      name = "CVE-2018-9055.patch";
      url = http://paste.opensuse.org/view/raw/330751ce;
      sha256 = "0m798m6c4v9yyhql7x684j5kppcm6884n1rrb9ljz8p9aqq2jqnm";
    })
  ];
}