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Verifying Assets

Inspektor Gadget container image and release assets are signed using cosign. In this guide, we will see how you can verify them with this tool. Note that, You would need to have cosign v2.0 installed.

Verify the container image manually​

Verifying the container image is pretty straightforward:

$ RELEASE='v0.27.0'
$ cosign verify --key https://raw.githubusercontent.com/inspektor-gadget/inspektor-gadget/${RELEASE}/inspektor-gadget.pub ghcr.io/inspektor-gadget/inspektor-gadget:${RELEASE}
The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - Existence of the claims in the transparency log was verified offline
  - The signatures were verified against the specified public key

[{"critical":{"identity":{"docker-reference":"ghcr.io/inspektor-gadget/inspektor-gadget"}, ...
]

Getting the above output followed by a JSON array of payloads, ensures you the container image was signed using our private key.

Verify the container Source Code Bill Of Materials (SBOMs)​

A Software Bill of Materials (SBOM) is a detailed list of all the components of a software. It facilitates security and license compliance assessments. The Inspektor Gadget project publishes SBOMs in the CycloneDX format for all our container images and CLI tools:

  • SBOMs for container images are attached to the corresponding image and can be found in our registry.
  • SBOMs for CLI tools are available as release assets.

In this section, we will see how you can verify and inspect the SBOMs attached to our container images. To do so, you will need cosign, oras and Inspektor Gadget public key.

# We will demo this for amd64, but it works the same for arm64.
$ arch=amd64
$ oras discover --platform linux/${arch} --artifact-type example/sbom ghcr.io/inspektor-gadget/inspektor-gadget:latest
Discovered 1 artifact referencing latest
Digest: sha256:...

Artifact Type   Digest
example/sbom    sha256:hash_of_sbom_manifest
# As we include SBOMs in our multi architecture container image, they are also
# signed.
# So, let's check the SBOM is signed with our private key:
$ cosign verify --key inspektor-gadget.pub ghcr.io/inspektor-gadget/inspektor-gadget@sha256:hash_of_sbom_manifest

Verification for ghcr.io/inspektor-gadget/inspektor-gadget@sha256:hash_of_sbom_manifest
The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - Existence of the claims in the transparency log was verified offline
  - The signatures were verified against the specified public key

[{"critical":{"identity":{"docker-reference":"ghcr.io/inspektor-gadget/inspektor-gadget"}, ...
]
# Let's download the SBOM and look at it:
$ oras pull --allow-path-traversal ghcr.io/inspektor-gadget/inspektor-gadget@sha256:hash_of_sbom_manifest
Downloading 1d479bb51392 /tmp/gadget-container-image-linux-amd64/sbom_cyclonedx.json
Downloaded  1d479bb51392 /tmp/gadget-container-image-linux-amd64/sbom_cyclonedx.json
Pulled [registry] ghcr.io/eiffel-fl/inspektor-gadget@sha256:hash_of_sbom_manifest
Digest: sha256:hash_of_sbom_manifest
$ jq '' /tmp/gadget-container-image-linux-amd64/sbom_cyclonedx.json
{
  "$schema": "http://cyclonedx.org/schema/bom-1.5.schema.json",
  "bomFormat": "CycloneDX",
  "specVersion": "1.5",
  "serialNumber": "urn:uuid:cf132c3d-5960-4536-9c03-9724babd76e9",
  "version": 1,
  "metadata": {
    "timestamp": "2024-03-21T17:22:38Z",
    "tools": {
      "components": [
        {
          "type": "application",
          "author": "anchore",
          "name": "syft",
          "version": "1.0.1"
        }
      ]
    },
    "component": {
      "bom-ref": "af63bd4c8601b7f1",
      "type": "file",
      "name": "."
    }
  },
  "components": [
    {
      "bom-ref": "pkg:deb/debian/[email protected]+deb12u5?arch=amd64&distro=debian-12&package-id=854ccee33785ad46",
      "type": "library",
      "publisher": "Santiago Vila <[email protected]>",
      "name": "base-files",
...
}

As the SBOM was signed with our private key, you can now inspect it to track down every dependencies we use to build our container image.

Verify the gadget-builder image​

We also sign the gadget-builder image which is used to build gadgets. You can verify it using the following command:

$ cosign verify --key inspektor-gadget.pub ghcr.io/inspektor-gadget/gadget-builder:latest

We highly recommend you to verify by digest and specify the digest when building. This helps to protect against TOCTOU issue, as the image tag that got verified could have been manipulated to point to another malicious image after the check.

$ DIGEST='sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522'
$ cosign verify --key inspektor-gadget.pub ghcr.io/inspektor-gadget/gadget-builder@$DIGEST

Verification for ghcr.io/inspektor-gadget/gadget-builder@sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522 --
The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - Existence of the claims in the transparency log was verified offline
  - The signatures were verified against the specified public key

[{"critical":{"identity":{"docker-reference":"ghcr.io/inspektor-gadget/gadget-builder"}, ...
]
$ sudo ig image build -t trace_exec:build-verified -f gadgets/trace_exec/gadget.yaml --builder-image ghcr.io/inspektor-gadget/gadget-builder@$DIGEST gadgets/trace_exec
Pulling builder image ghcr.io/inspektor-gadget/gadget-builder@sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522
ghcr.io/inspektor-gadget/gadget-builder@sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522: Pulling from inspektor-gadget/gadget-builder
...
Digest: sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522
Status: Downloaded newer image for ghcr.io/inspektor-gadget/gadget-builder@sha256:4967ad1a11a9ed32867dc0d63e137dc2196c560db4b3644c7c0c97fccea7c522
Successfully built ghcr.io/inspektor-gadget/gadget/trace_exec:build-verified@sha256:c85eac1e4615a08c74883402f73c5f8667b64597bd51f9e46275dfdbb0a04703

Verify an asset​

Rather than signing all the assets, we only sign the checksums file. So, by verifying this file, you can then verify the assets themselves by checking their checksums.

Verifying the checksums file​

The following snippet show you how to verify the checksums file:

$ RELEASE='v0.19.0'
$ ASSET="SHA256SUMS"
$ URL="https://github.com/inspektor-gadget/inspektor-gadget/releases/download/${RELEASE}"
# We need to get the asset itself, its signature file and the corresponding bundle:
$ for i in $URL/$ASSET $URL/$ASSET.sig $URL/$ASSET.bundle; do
	wget $i
done
...
# We need to get the public key too.
$ wget $URL/inspektor-gadget.pub
...
$ cosign verify-blob $ASSET --bundle ${ASSET}.bundle --signature ${ASSET}.sig --key inspektor-gadget.pub --offline
Verified OK

As you can see, the checksum file was correctly verified which means this file was indeed signed by us. So, you can use this file to verify other release assets.

Verify an asset​

Once you verified the checksums file, you can now verify the integrity of an asset using such checksums file:

$ RELEASE='v0.19.0'
$ ASSET="inspektor-gadget-${RELEASE}.yaml"
$ URL="https://github.com/inspektor-gadget/inspektor-gadget/releases/download/${RELEASE}"
$ wget $URL/$ASSET
$ grep $ASSET SHA256SUMS | shasum -a 256 -c -s || echo "Error: ${ASSET} didn't pass the checksum verification. You must not use it!"