ubi9-base-micro

ubi9-base-micro builds the root UBI 9 micro base for the NWarila base-image family. It produces two local-test image tags from one Dockerfile:

• base-micro: glibc plus RHEL CA trust, no shell, no package-manager executable, RPM database preserved at /var/lib/rpm, and USER 65532:65532.
• base-micro-dev: the same UBI 9 floor with a shell and a minimal native build toolchain for leaf build-time stages.

Why It Exists

The image is the smallest hardened floor in the platform base family. It keeps the rpmdb for truthful scanners, installs all runtime RPMs from direct Red Hat UBI CDN pins with raw rpm -Uvh, configures the Red Hat OpenSSL FIPS provider in approved mode, and removes runtime shell/package-manager entry points. The leaf image or application still owns app-specific minimization such as Java jdeps/jlink, Python stdlib pruning, and application dependency trimming.

Rebuilds use pinned direct-CDN RPMs for both the runtime transaction and the FIPS-verification OpenSSL closure, without consulting live repository metadata. They fail closed if a pinned blob is unavailable. Red Hat CDN retention is not guaranteed, so this is a bounded rebuild window rather than a claim that a commit reproduces forever; see TD-4.

Verify From a Clean Machine (No Auth)

Anyone can cryptographically verify the published ghcr.io/nwarila/ubi9-base-micro:base-micro image with no registry authentication. The prerequisites are cosign, crane, jq, and slsa-verifier.

Resolve the moving base-micro tag once, then anchor every child lookup to the resolved index so a concurrent publish cannot mix index and child generations:

IMAGE="ghcr.io/nwarila/ubi9-base-micro"
TAG="base-micro"
INDEX_DIGEST="$(crane digest "${IMAGE}:${TAG}")"
INDEX_REF="${IMAGE}@${INDEX_DIGEST}"
CHILD_DIGEST="$(crane digest --platform linux/amd64 "${INDEX_REF}")"
CHILD_REF="${IMAGE}@${CHILD_DIGEST}"
PUBLISH_REF="refs/heads/main"

Verify the index signature:

cosign verify "${INDEX_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

Verify the SPDX and CycloneDX attestations on the selected platform child:

cosign verify-attestation --type spdxjson "${CHILD_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

cosign verify-attestation --type cyclonedx "${CHILD_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

Check the verified SPDX predicate for the required glibc package:

cosign verify-attestation --type spdxjson "${CHILD_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \
  | jq -r '.payload | @base64d | fromjson | .predicate.packages[].name' | grep -q glibc

Verify the NIST SP 800-190 section 4.1 image-control predicate:

cosign verify-attestation --type https://nwarila.dev/attestations/nist-sp-800-190-image/v1 "${CHILD_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

Verify the tailored RHEL9 STIG ARF predicate:

cosign verify-attestation --type https://nwarila.dev/attestations/stig-arf/v1 "${CHILD_REF}" \
  --certificate-identity "https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-image.yaml@${PUBLISH_REF}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

Finally, verify the index-bound SLSA provenance with both verifiers:

cosign verify-attestation --type slsaprovenance "${INDEX_REF}" \
  --certificate-identity "https://github.com/slsa-framework/slsa-github-generator/.github/workflows/generator_container_slsa3.yml@refs/tags/v2.1.0" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com"

slsa-verifier verify-image "${INDEX_REF}" \
  --source-uri github.com/NWarila/ubi9-base-micro \
  --builder-id "https://github.com/slsa-framework/slsa-github-generator/.github/workflows/generator_container_slsa3.yml@refs/tags/v2.1.0"

docs/reference/verify.md is the authoritative full contract, including rationale and edge cases. See also the docs/how-to/verify-a-published-image.md task flow. gh attestation verify is not part of this repository's published-image contract.

Supply Chain Pipeline

flowchart TB
  subgraph dockerfile["Dockerfile stage DAG"]
    FIPS["fips-verify"] -->|"proof + binaries"| RPM["rpm-rootfs"]
    FIPS -->|"proof"| COMMON["runtime-common"]
    RPM -->|"/rootfs"| COMMON
    COMMON --> AMD["runtime-amd64"]
    COMMON --> ARM["runtime-arm64"]
    AMD --> TARGET["runtime-${TARGETARCH}"]
    ARM --> TARGET
    DEVROOT["dev-rootfs"] --> DEV["dev<br/>defined but NOT published<br/>(build target = runtime)"]
  end

  subgraph publish["publish — push to main/tag only"]
    BUILD["build + push by digest<br/>recursive cosign sign"] --> EVIDENCE["resolve children<br/>tailored STIG ARF + rpmdb SBOMs<br/>scanner freshness + fixable gates + JSON/SARIF reports<br/>secret scan + NIST"]
    EVIDENCE --> ATTEST["attest evidence per child"]
  end

  TARGET --> BUILD
  TAG["slsa-generator-tag-integrity"] --> BUILD
  ATTEST --> SLSA["slsa-provenance<br/>SLSA L3 on index<br/>push to main/tag only"]
  ATTEST --> REKOR["rekor-rollup<br/>full split evidence set<br/>push to main/tag only"]
  SLSA --> REKOR

Loading

Pull requests exercise the tag-integrity job but do not publish, attest, or run the Rekor roll-up.

Comparison at a Glance

Dimension	ubi9-base-micro	Stock ubi9/ubi-micro	Chainguard	Canonical rocks
Package inventory	Retained RPM rpmdb, rpmdb-derived SPDX and CycloneDX SBOMs, and a no-phantom-package guard.	Retained RPM rpmdb, matching the same UBI base ecosystem.	APK/Wolfi ecosystem with signed SBOMs and no RPM rpmdb.	dpkg/Chisel ecosystem with no RPM rpmdb; Chisel's manifest.wall supplies package, slice, and file metadata to scanners.
Signing, SBOM, provenance / SLSA	Cosign keyless signature, per-child SPDX and CycloneDX SBOMs, and index-bound SLSA L3 provenance.	Artifact-level signing, SBOM, and provenance evidence depends on the selected digest and publication channel.	Signed images and SBOMs with SLSA 3 provenance.	The OCI factory produces SBOMs and provenance; exact signing and SLSA mechanisms vary by rock and channel.
STIG evidence	Tailored RHEL9 STIG ARF, evaluated fail-closed and signed per platform child.	RHEL9 STIG content is available; artifact-specific ARF evidence depends on the selected digest and channel.	GPOS-SRG STIG profile and STIG-hardened images.	Ubuntu DISA-STIG material is available; per-rock evidence varies.
CMVP FIPS	RHEL OpenSSL provider #4857 in approved mode on amd64; arm64 runs the same provider and self-tests but is not a validated operational environment.	RHEL FIPS modules are available under Red Hat certificates; exact provider and configuration evidence is artifact-specific.	Approved-only FIPS images use other validated modules, including OpenSSL #4282.	Ubuntu FIPS modules and containers operate under Canonical certificates and their documented runtime conditions.
Byte reproducibility	Fail-closed two-build identity for both architectures, with exported-rootfs, contract-digest, and rpmdb assertions.	Artifact-level reproducibility evidence depends on the selected digest and publication pipeline.	Bit-for-bit reproduction from signed apko configuration.	Reproducibility varies by rock and build pipeline.
Footprint	22.74 MiB (23,840,723 B) for the amd64 regular-file rootfs, gated at 25 MiB.	21.93 MiB (22,995,384 B) by the same method, about 0.81 MiB smaller.	Varies by image and package set.	Varies by rock and slice selection.

Signing, SBOMs, SLSA, STIG hardening, FIPS, and reproducibility exist across these families; this table highlights this repository's specific, verifiable mechanisms: RPM rpmdb evidence, the #4857 approved-mode provider, a tailored RHEL9 STIG ARF attestation, and a fail-closed byte-for-byte digest gate.

Image Family

ubi9-base-micro is the root image. base-python has its own two-phase publication workflow. Its current and historical publication evidence is in the canonical publication evidence contract. base-java is configured to publish from images/java21/ on pushes to main that change it: a Cosign keyless signature only, identity https://github.com/NWarila/ubi9-base-micro/.github/workflows/publish-java21.yaml@refs/heads/main, alias base-java. The publisher is configured to produce none of the family evidence floor below (SBOMs, fixable-CVE gates, SLSA, NIST, STIG, reproducibility, trust contract), under the owner's first-publish exception in ADR-0010. The remaining language variants are planned as images/<variant>/ trees.

Image	Status	Base relationship	Runtime scope
base-micro	Current repository	Root image	glibc, CA trust, rpmdb, OpenSSL #4857 provider
base-python	Dedicated publisher	FROM base-micro@sha256:<digest>	CPython runtime on the micro floor
base-node	Planned	FROM base-micro@sha256:<digest>	Node.js runtime on the micro floor
base-java	Configured to publish, signature only	FROM base-micro@sha256:<digest>	OpenJDK 21 headless server JRE on the micro floor (declared omissions)

The common evidence floor is a cosign keyless signature, SLSA L3 provenance, rpmdb-derived SPDX and CycloneDX SBOMs, Trivy and Grype fixable-CVE gates, complete report-only JSON and SARIF findings, NIST SP 800-190 section 4.1 image evidence, tailored RHEL9 STIG ARF, and byte-for-byte reproducibility. Published signatures and attestations are Rekor-logged. A variant also requires an index-only trust-contract predicate binding its digest, package, tree, workflow, and commit; the merged base-python publisher implements that requirement. Planned variants must carry the applicable full evidence set under their images/<variant>/ trees before publication, each publishing through its own path-scoped workflow.

base-python additionally publishes absence-proof OpenVEX for SQLite and libuuid; those documents do not authorize or suppress scanner findings.

Responsibility boundary: the base family owns a standard hardened floor through RPM hygiene (install_weak_deps=0, --nodocs, locale/man stripping, shell removal, discarded builders) with the rpmdb preserved for truthful scanning. The leaf/user owns app-specific minimization such as Java jdeps/jlink, Python stdlib pruning, and application dependency trimming.

Quickstart

Build both local tags:

make build

Run the runtime hardening gate against base-micro:

make test

Run the repository lint and test hooks:

pre-commit run --all-files

The published root-image namespace is:

ghcr.io/nwarila/ubi9-base-micro

The Python publisher targets ghcr.io/nwarila/ubi9-base-python; see the canonical publication evidence contract.

Security and Compliance Posture

The runtime uses the Red Hat Enterprise Linux 9 OpenSSL FIPS Provider in approved mode through /etc/pki/tls/openssl-fips.cnf and OPENSSL_CONF/OPENSSL_MODULES. Both amd64 and arm64 hold openssl-fips-provider-so-3.0.7-8.el9 with fips.so version 3.0.7-395c1a240fbfffd8; the provider RPMs are fetched from Red Hat UBI CDN direct URLs, verified with Red Hat RPM signatures and pinned SHA-256 values, and installed locally to preserve rpm ownership. The amd64 image is the CMVP #4857 validated approved-mode configuration. The arm64 image ships the same module and passes approved-mode self-tests, but it is explicitly not a CMVP-validated configuration on that architecture because #4857 lists no arm64 OE. These are module-scoped and approved-mode-scoped statements, not host, OS, container, or application FIPS validation claims. The platform host remains non-FIPS. See docs/compliance/fips.md and docs/explanation/fips-mechanism.md.

The authoritative SBOM evidence is Syft rpmdb-derived SPDX and CycloneDX, attested per published platform child digest. BuildKit SBOM output is disabled so the published SPDX evidence has a single source. Vulnerability scanners, fixable-CVE gates, complete report-only JSON/SARIF, NIST SP 800-190 section 4.1 image evidence, and the tailored RHEL9 STIG ARF gate run in CI; publish attaches the STIG ARF summary predicate per platform digest. See docs/compliance/stig.md, docs/compliance/nist-800-190.md, and docs/compliance/vex.md.

Runtime footprint is gated by tools/assert-footprint.py using exported-rootfs-regular-file-bytes. The current amd64 runtime measures 23,840,723 bytes / 22.7363 MiB against the 25 MiB H2 gate; local OCI compressed layer sum is 12,095,601 bytes / 11.5353 MiB. See docs/explanation/footprint.md.

Repository-specific decisions are recorded under docs/decision-records/repo/. They cover the byte-for-byte reproducibility gate, FIPS scope, SLSA generator identity model, runtime strip posture, RPM refresh loop, scanner policy, STIG and NIST evidence, CI runner determinism, direct-CDN runtime RPM sourcing, and base-family topology.

Documentation

The docs follow the org-standard Diataxis layout:

• Tutorials for learning walkthroughs.
• How-to guides for task procedures.
• Reference for contracts and gate inventories.
• Explanation for design rationale.
• Compliance for scoped evidence notes.
• Decision records for repository ADRs.

Start with docs/README.md for the full index.

License

This repository is licensed under the terms in LICENSE.