SBOM attestation¶
Cosign supports generating and verifying in-toto attestations. This tool enables you to sign and verify SBOM attestation. And, Trivy can take an SBOM attestation as input and scan for vulnerabilities
Note
In the following examples, the cosign command will write an attestation to a target OCI registry, so you must have permission to write.
If you want to avoid writing an OCI registry and only want to see an attestation, add the --no-upload option to the cosign command.
Sign with a local key pair¶
Cosign can generate key pairs and use them for signing and verification. After you run the following command, you will get a public and private key pair. Read more about how to generate key pairs.
$ cosign generate-key-pair
In the following example, Trivy generates an SBOM in the CycloneDX format, and then Cosign attaches an attestation of the SBOM to a container image with a local key pair.
# The cyclonedx type is supported in Cosign v1.10.0 or later.
$ trivy image --format cyclonedx -o sbom.cdx.json <IMAGE>
$ cosign attest --key /path/to/cosign.key --type cyclonedx --predicate sbom.cdx.json <IMAGE>
Then, you can verify attestations on the image.
$ cosign verify-attestation --key /path/to/cosign.pub --type cyclonedx <IMAGE>
You can also create attestations of other formatted SBOM.
# spdx
$ trivy image --format spdx -o sbom.spdx <IMAGE>
$ cosign attest --key /path/to/cosign.key --type spdx --predicate sbom.spdx <IMAGE>
# spdx-json
$ trivy image --format spdx-json -o sbom.spdx.json <IMAGE>
$ cosign attest --key /path/to/cosign.key --type spdx --predicate sbom.spdx.json <IMAGE>
Keyless signing¶
You can use Cosign to sign without keys by authenticating with an OpenID Connect protocol supported by sigstore (Google, GitHub, or Microsoft).
# The cyclonedx type is supported in Cosign v1.10.0 or later.
$ trivy image --format cyclonedx -o sbom.cdx.json <IMAGE>
# The following command uploads SBOM attestation to the public Rekor instance.
$ COSIGN_EXPERIMENTAL=1 cosign attest --type cyclonedx --predicate sbom.cdx.json <IMAGE>
You can verify attestations.
$ COSIGN_EXPERIMENTAL=1 cosign verify-attestation --type cyclonedx <IMAGE>
Scanning¶
Trivy can take an SBOM attestation as input and scan for vulnerabilities. Currently, Trivy supports CycloneDX-type attestation.
In the following example, Cosign can get an CycloneDX-type attestation and trivy scan it. You must create CycloneDX-type attestation before trying the example. To learn more about how to create an CycloneDX-Type attestation and attach it to an image, see the Sign with a local key pair section.
$ cosign verify-attestation --key /path/to/cosign.pub --type cyclonedx <IMAGE> > sbom.cdx.intoto.jsonl
$ trivy sbom ./sbom.cdx.intoto.jsonl
sbom.cdx.intoto.jsonl (alpine 3.7.3)
=========================
Total: 2 (UNKNOWN: 0, LOW: 0, MEDIUM: 0, HIGH: 0, CRITICAL: 2)
┌────────────┬────────────────┬──────────┬───────────────────┬───────────────┬──────────────────────────────────────────────────────────┐
│ Library │ Vulnerability │ Severity │ Installed Version │ Fixed Version │ Title │
├────────────┼────────────────┼──────────┼───────────────────┼───────────────┼──────────────────────────────────────────────────────────┤
│ musl │ CVE-2019-14697 │ CRITICAL │ 1.1.18-r3 │ 1.1.18-r4 │ musl libc through 1.1.23 has an x87 floating-point stack │
│ │ │ │ │ │ adjustment im ...... │
│ │ │ │ │ │ https://avd.aquasec.com/nvd/cve-2019-14697 │
├────────────┤ │ │ │ │ │
│ musl-utils │ │ │ │ │ │
│ │ │ │ │ │ │
│ │ │ │ │ │ │
└────────────┴────────────────┴──────────┴───────────────────┴───────────────┴──────────────────────────────────────────────────────────┘