What is Known and Unknown about your Software Supply Chain

Dinosaur Meme

The software supply chain is like a rabbit hole that can be very deep and hold many twists and turns. It’s hard to track where the different tunnels may lead. With SBOMs, SLSA attestations, scorecards, VEX, and other in-toto ITE-6 attestations, the list of metadata associated with an artifact is growing. You may wonder:

Where do I store my SBOMs, SLSA attestations, and other metadata documents? Can I find these documents quickly? What do I know (and not know) about my supply chain?

GUAC has the ability to ingest and link these documents together into a complete picture of your software supply chain. With GUAC you can easily determine your:

known, knowns
known, unknowns
unknown, unknowns

In the “Expanding your view of the software supply chain” demo, we went through the process of ingesting an SBOM and letting GUAC expand our horizons on what we know about our environment autonomously. In this demo, we’ll take that information and use it to determine what we know and don’t know about the artifacts.

Requirements

A fresh copy of the GUAC service infrastructure through Docker Compose. Including the guacone binary in your path and demo data extracted to guac-data-main.
Completion of the Expanding your view of the software supply chain demo

Understanding the data

GUAC, at the time of the beta release, can store various metadata about an artifact. In the context of query CLI that we will be using, the evidence nodes have the following definitions:

Evidence Nodes	Description
`hashEquals`	When two artifacts are equal
`scorecards`	The OpenSSF scorecard associated with the source repo
`occurrences`	A package is associated with an artifact (digest) (or vice-versa)
`hasSrcAt`	A package has a source repo at the following location
`hasSBOMs`	A package/artifact has an SBOM stored in a downloadable location
`hasSLSAs`	The artifact has an SLSA attestation stored in a downloadable location
`certifyVulns`	The package has been scanned (currently via OSV) and the results of the scan
`vexLinks`	A VEX document associated with the Vulnerability
`badLinks`	List of CertifyBad associated with the package, source or artifact
`goodLinks`	List of CertifyGood associated with the package, source or artifact
`pkgEquals`	Two packages (with different purls) are equal

For more information on these, refer to the GraphQL documentation and ontology definitions.

Run the query to find the knowns and unknowns

Utilizing the CLI and GUAC Visualizer, we can determine:

The location of SBOMs, SLSA attestations, and scorecard information
What information we are missing

We will utilize the “query known” CLI. This CLI has the ability to search a package via pURL, source URL following the definition of VCS uri from the SPDX documentation <vcs_tool>+<transport>://<host_name>[/<path_to_repository>][@<revision_tag_or_branch>][#<sub_path>]) and a artifact (algorithm:digest).

Look at if a package (vault) to see if it has an SBOM associated with and where it can be found:

guacone query known package "pkg:guac/cdx/docker.io/library/vault@sha256:d9fdd0e93cdd325b144aed2c68d53999875c907c5a37b2d1a9456c8a45886158?tag=latest"

The output will look similar to this:

 +------------------------------------------------+
 | Package Name Nodes                             |
 +-----------+-----------+------------------------+
 | NODE TYPE | NODE ID # | ADDITIONAL INFORMATION |
 +-----------+-----------+------------------------+
 +-----------+-----------+------------------------+
 Visualizer url: http://localhost:3000/?path=4861,30,29
 +----------------------------------------------------------------------------------------------------------------------------------------+
 | Package Version Nodes                                                                                                                  |
 +-----------+-----------+----------------------------------------------------------------------------------------------------------------+
 | NODE TYPE | NODE ID # | ADDITIONAL INFORMATION                                                                                         |
 +-----------+-----------+----------------------------------------------------------------------------------------------------------------+
 | hasSBOM   | 5433      | SBOM Download Location: file:///../guac-data/docs/cyclonedx/syft-cyclonedx-docker.io-library-vault.latest.json |
 +-----------+-----------+----------------------------------------------------------------------------------------------------------------+
 Visualizer url: http://localhost:3000/?path=4862,4861,30,29,5433

The output has two separate tables: one for the “package name level” and the other at the “package version level”. Evidence/metadata nodes at the “package name level” apply to all the versions that come below it. “Package version level”, on the other hand, only applies to the version specified. By default, if a version is not specified during ingestion, it defaults to an empty version string.

The “package name level” does not have any nodes associated with it, but the “package version level” does have the “hasSBOM” node associated with it. This shows us that this package has an SBOM associated with it and can be downloaded at the following location. Future plans for GUAC are to have an evidence store with GUAC to store SBOM and SLSA attestations for quick access. For now, we can quickly locate the SBOM. We also learned that we are missing hasSLSA attestations for this package.

Determine if an artifact has an SLSA attestation associated with it

Along the same lines, we have the hash of an executable binary that was generated. We can ask the question, “Is there an SLSA attestation associated?” with it. If so, where is it located and is there a package associated with this particular hash?

This time, we will change query for known artifact rather than package:

guacone query known artifact "sha256:625fe537a4c1657bd613be44f7882a8883c13c3b72919cfdbd02d2eb4dbf677b"

The output should look similar to the following:

+------------+-----------+-----------------------------------------------------------------------------------------------------------------+
| NODE TYPE  | NODE ID   | ADDITIONAL INFORMATION                                                                                          |
+------------+-----------+-----------------------------------------------------------------------------------------------------------------+
| occurrence | 5477      | Occurrence for Package: pkg:guac/generic/gs%3A/kubernetes-release/release/v1.24.1/bin/windows/arm64/kubectl.exe |
+------------+-----------+-----------------------------------------------------------------------------------------------------------------+
| hasSLSA    | 6364      | SLSA Attestation Location: file:///../guac-data/docs/slsa/kube-slsa-v1.24.1.json                                |
+------------+-----------+-----------------------------------------------------------------------------------------------------------------+
Visualizer url: http://localhost:3000/?path=5476,5477,6364

From the output, we know that there is a SLSA attestation associated with this particular artifact and its location. We also see from the output, that the digest is associated with the Windows ARM64 version of the kubectl!

Note: Currently, the package “purl” is guessed based on heuristics. This will improve as future versions of SLSA adopt ResourceDescriptor field type.

For more information on the SLSA attestation, we can look up the SLSA attestation via the Node ID in the GraphQL playground that is shown in the output. Be sure to replace the ID with the one you received from the output.

query SLSAQ3 {
  HasSLSA(hasSLSASpec: { id: "6364" }) {
    id
    subject {
      id
      algorithm
      digest
    }
    slsa {
      builtFrom {
        id
        algorithm
        digest
      }
      builtBy {
        id
        uri
      }
      buildType
      slsaPredicate {
        key
        value
      }
      slsaVersion
      startedOn
      finishedOn
      origin
      collector
    }
  }
}

To view the output:

{
 "data": {
   "HasSLSA": [
     {
       "id": "6364",
       "subject": {
         "id": "5476",
         "algorithm": "sha256",
         "digest": "625fe537a4c1657bd613be44f7882a8883c13c3b72919cfdbd02d2eb4dbf677b"
       },
       "slsa": {
         "builtFrom": [
           {
             "id": "6354",
             "algorithm": "sha1",
             "digest": "aaf024b5e8dc5e08e4414583203968ca0a5ec043"
           }
         ],
         "builtBy": {
           "id": "6356",
           "uri": "https://git.k8s.io/release/docs/krel"
         },
         "buildType": "https://cloudbuild.googleapis.com/CloudBuildYaml@v1",
         "slsaPredicate": [
           {
             "key": "slsa.buildType",
             "value": "https://cloudbuild.googleapis.com/CloudBuildYaml@v1"
           },
           {
             "key": "slsa.builder.id",
             "value": "https://git.k8s.io/release/docs/krel"
           },
           {
             "key": "slsa.invocation.configSource.entryPoint",
             "value": "https://git.k8s.io/release/gcb/stage/cloudbuild.yaml"
           },
           {
             "key": "slsa.invocation.parameters.branch",
             "value": "release-1.24"
           },
           {
             "key": "slsa.invocation.parameters.build-version",
             "value": "v1.24.1-rc.0.29+1868a3a2eb9945"
           },
           {
             "key": "slsa.invocation.parameters.nomock",
             "value": "true"
           },
           {
             "key": "slsa.invocation.parameters.type",
             "value": "official"
           },
           {
             "key": "slsa.materials.0.digest.sha1",
             "value": "'aaf024b5e8dc5e08e4414583203968ca0a5ec043'"
           },
           {
             "key": "slsa.materials.0.uri",
             "value": "git+https://github.com/kubernetes/kubernetes"
           },
           {
             "key": "slsa.metadata.buildFinishedOn",
             "value": "2022-05-24T13:27:46.145159431Z"
           },
           {
             "key": "slsa.metadata.buildInvocationID",
             "value": "b6186090-c8ff-4f91-97cf-7a3b47699e57"
           },
           {
             "key": "slsa.metadata.buildStartedOn",
             "value": "2022-05-24T12:13:35.054695403Z"
           },
           {
             "key": "slsa.metadata.completeness.environment",
             "value": "false"
           },
           {
             "key": "slsa.metadata.completeness.materials",
             "value": "true"
           },
           {
             "key": "slsa.metadata.completeness.parameters",
             "value": "true"
           },
           {
             "key": "slsa.metadata.reproducible",
             "value": "false"
           }
         ],
         "slsaVersion": "https://slsa.dev/provenance/v0.2",
         "startedOn": "2022-05-24T12:13:35.054695403Z",
         "finishedOn": "2022-05-24T12:13:35.054695403Z",
         "origin": "file:///../guac-data/docs/slsa/kube-slsa-v1.24.1.json",
         "collector": "FileCollector"
       }
     }
   ]
 }
}

Run the query on the Prometheus package we were working on within the workflow demo:
```
guacone query known package "pkg:golang/github.com/prometheus/client_golang@v1.11.1"
```
The output should be similar to this:
```
+---------------------------------------------------------------------------------+
| Package Name Nodes                                                              |
+-----------+-----------+---------------------------------------------------------+
| NODE TYPE | NODE ID   | ADDITIONAL INFORMATION                                  |
+-----------+-----------+---------------------------------------------------------+
| hasSrcAt  | 7647      | Source: git+https://github.com/prometheus/client_golang |
+-----------+-----------+---------------------------------------------------------+
Visualizer url: http://localhost:3000/?path=578,327,6,7647
+----------------------------------------------------+
| Package Version Nodes                              |
+-------------+-----------+--------------------------+
| NODE TYPE   | NODE ID   | ADDITIONAL INFORMATION   |
+-------------+-----------+--------------------------+
| certifyVuln | 13469     | vulnerability ID: NoVuln |
+-------------+-----------+--------------------------+
Visualizer url: http://localhost:3000/?path=579,578,327,6,13469
```
In this example, the “package name level” has the “hasSrcAt” node that shows us that the “prometheus/client_golang” source repo is located at “https://github.com/prometheus/client_golang”.

The “Package Version Nodes” shows us that the specific package with the purl pkg:golang/github.com/prometheus/client_golang@v1.11.1 was scanned and did not contain any vulnerabilities associated with it.

NOTE: This is just the vulnerability associated with this specific package (not taking into account dependencies). For a full in-depth vulnerability search please follow the Query Vulnerability demo.

We also see that in this case, we did not get a hasSBOM associated with it. Meaning that we do not have any SBOM information related to this package. We also see there are no nodes for the SLSA attestations, but we could query the source for more information about it and its scorecard information.

But before we do that, we will look at another version of the “prometheus/client_golang” package with the purl “pkg:golang/github.com/prometheus/client_golang@v1.4.0”. Note the version is now v1.4.0.

Use the CLI to query the other version:

guacone query known package "pkg:golang/github.com/prometheus/client_golang@v1.4.0"

+---------------------------------------------------------------------------------+
| Package Name Nodes                                                              |
+-----------+-----------+---------------------------------------------------------+
| NODE TYPE | NODE ID   | ADDITIONAL INFORMATION                                  |
+-----------+-----------+---------------------------------------------------------+
| hasSrcAt  | 7647      | Source: git+https://github.com/prometheus/client_golang |
+-----------+-----------+---------------------------------------------------------+
Visualizer url: http://localhost:3000/?path=578,327,6,7647
+-----------------------------------------------------------------+
| Package Version Nodes                                           |
+-------------+-----------+---------------------------------------+
| NODE TYPE   | NODE ID   | ADDITIONAL INFORMATION                |
+-------------+-----------+---------------------------------------+
| certifyVuln | 13471     | vulnerability ID: ghsa-cg3q-j54f-5p7p |
| certifyVuln | 13473     | vulnerability ID: go-2022-0322        |
+-------------+-----------+---------------------------------------+
Visualizer url: http://localhost:3000/?path=7600,578,327,6,13471,13473

We once again see that at the “package name level” we have the same source repo associated with it. But at the “package version level” (at v1.4.0) there are some vulnerabilities that are associated with it! The newer version of the same “prometheus/client_golang” did not have these vulnerabilities. We could do further investigation via the GUAC visualizer (and other upcoming tools) to determine which packages are dependent on these and need to be updated to a newer version. For example, from the workflow demo, we know that github.com/armon/go-metrics version 0.3.10 depends on this package and should be immediately updated!

     {
        "id": "7624",
        "justification": "dependency data collected via deps.dev",
        "package": {
          "id": "6",
          "type": "golang",
          "namespaces": [
            {
              "id": "279",
              "namespace": "github.com/armon",
              "names": [
                {
                  "id": "280",
                  "name": "go-metrics",
                  "versions": [
                    {
                      "id": "281",
                      "version": "v0.3.10",
                      "qualifiers": [],
                      "subpath": ""
                    }
                  ]
                }
              ]
            }
          ]
        },
        "dependencyPackage": {
          "id": "6",
          "type": "golang",
          "namespaces": [
            {
              "id": "396",
              "namespace": "github.com/prometheus",
              "names": [
                {
                  "id": "397",
                  "name": "client_golang",
                  "versions": []
                }
              ]
            }
          ]
        },
        "versionRange": "v1.4.0",
        "origin": "deps.dev",
        "collector": "deps.dev"
      }

Let’s take a closer look at the source repo for the prometheus/client_golang package: We can run the query:

Note: source is specified to indicate we are querying a source repo.

guacone query known source "git+https://github.com/prometheus/client_golang"

+-----------+-----------+--------------------------------------------------------------------+
| NODE TYPE | NODE ID   | ADDITIONAL INFORMATION                                             |
+-----------+-----------+--------------------------------------------------------------------+
| hasSrcAt  | 7647      | Source for Package: pkg:golang/github.com/prometheus/client_golang |
+-----------+-----------+--------------------------------------------------------------------+
| scorecard | 7583      | Overall Score: 6.600000                                            |
+-----------+-----------+--------------------------------------------------------------------+
Visualizer url: http://localhost:3000/?path=7582,7581,6965,7647,7583

From this output, we see the reverse of what we saw when we queried the package. This time, we see that this source is related to the prometheus/client_golang package we queried for above but also we see that there is an OpenSSF scorecard associated.

Finally, let’s query for another source repo:

guacone query known source "git+https://github.com/googleapis/google-cloud-go"

The output should be similar to:

+-----------+-----------+---------------------------------------------------------------------+
| NODE TYPE | NODE ID   | ADDITIONAL INFORMATION                                              |
+-----------+-----------+---------------------------------------------------------------------+
| hasSrcAt  | 7074      | Source for Package: pkg:golang/cloud.google.com/go                  |
| hasSrcAt  | 7075      | Source for Package: pkg:golang/cloud.google.com/go/storage          |
| hasSrcAt  | 7156      | Source for Package: pkg:golang/cloud.google.com/go/spanner          |
| hasSrcAt  | 8948      | Source for Package: pkg:golang/cloud.google.com/go/compute/metadata |
| hasSrcAt  | 8949      | Source for Package: pkg:golang/cloud.google.com/go/logging          |
| hasSrcAt  | 8950      | Source for Package: pkg:golang/cloud.google.com/go/longrunning      |
+-----------+-----------+---------------------------------------------------------------------+
| scorecard | 6968      | Overall Score: 8.300000                                             |
+-----------+-----------+---------------------------------------------------------------------+
Visualizer url: http://localhost:3000/?path=6967,6966,6965,7074,7075,7156,8948,8949,8950,6968

Here we see that this specific source repo is associated with various different packages (go, storage, spanner…etc), and again we see that it does have a scorecard associated with a score of 8.3

Knowing the unknown

Based on the information gathered above:

We know what we have about the various artifacts (either ingested or determine by the services of GUAC).
We can quickly locate an SBOM, an SLSA attestation (other ITE-6 attestations), OpenSSF scorecard information, and other metadata quickly.
We determined what we don’t know. For example, some packages did not have an SBOM or SLSA attestation associated. There may have been source repositories that weren’t scanned by OpenSSF Scorecard.
We found information that we didn’t even know that we needed to know. For example, the vulnerable version of prometheus/client_golang (the older version) is used in our software supply chain and needs to be updated immediately. Knowing the unknown is the first key step in securing the supply chain. If the security teams and developers have no knowledge of these, how can we keep shifting left effectively?

Now that you know something about your software supply chain, let’s look at what you probably want to know about right away: vulnerabilties.