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feat: use cosign to verify kubelet binaries #96

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Merged
merged 1 commit into from
Oct 30, 2025
Merged

feat: use cosign to verify kubelet binaries #96

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30 changes: 11 additions & 19 deletions Dockerfile
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Original file line number Diff line number Diff line change
Expand Up @@ -4,32 +4,24 @@
ARG BASE_IMAGE=registry.k8s.io/build-image/debian-iptables:bookworm-v1.0.0
ARG SLIM_PACKAGES="ca-certificates libcap2 ethtool iproute2 nfs-common socat util-linux"

FROM alpine:latest AS builder-amd64
FROM alpine:latest AS builder

ARG TARGETARCH
ARG KUBELET_VER
ARG KUBELET_SHA512_AMD64
ARG KUBELET_URL=https://dl.k8s.io/release/${KUBELET_VER}/bin/linux/${TARGETARCH}/kubelet

RUN wget -q -O /kubelet ${KUBELET_URL} \
&& sha512sum /kubelet \
&& echo "${KUBELET_SHA512_AMD64} /kubelet" | sha512sum -cw \
&& chmod +x /kubelet

FROM alpine:latest AS builder-arm64
RUN apk add --no-cache cosign

ARG TARGETARCH
ARG KUBELET_VER
ARG KUBELET_SHA512_ARM64
ARG KUBELET_URL=https://dl.k8s.io/release/${KUBELET_VER}/bin/linux/${TARGETARCH}/kubelet

RUN wget -q -O /kubelet ${KUBELET_URL} \
&& sha512sum /kubelet \
&& echo "${KUBELET_SHA512_ARM64} /kubelet" | sha512sum -cw \
&& chmod +x /kubelet
RUN wget -q -O /kubelet ${KUBELET_URL}
RUN wget -q -O /kubelet.sig ${KUBELET_URL}.sig
RUN wget -q -O /kubelet.cert ${KUBELET_URL}.cert

ARG TARGETARCH
FROM builder-${TARGETARCH} AS builder
# see https://kubernetes.io/docs/tasks/administer-cluster/verify-signed-artifacts/
RUN cosign verify-blob "/kubelet" \
--signature "/kubelet.sig" \
--certificate "/kubelet.cert" \
--certificate-identity [email protected] \
--certificate-oidc-issuer https://accounts.google.com

########################

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11 changes: 0 additions & 11 deletions Makefile
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Expand Up @@ -6,8 +6,6 @@ BRANCH ?= $(shell git rev-parse --abbrev-ref HEAD)
REGISTRY_AND_USERNAME := $(REGISTRY)/$(USERNAME)
NAME := kubelet
KUBELET_VER := v1.35.0-alpha.2
KUBELET_SHA512_AMD64 := 1b4bfe455eafec7aa5f5bc1510d4b9eebe1e62ac85544871409ffca9ee0b7e226862356110acc3d96bad5d9205e9e46032c05c238cb51d50cb438de51d9cfedf
KUBELET_SHA512_ARM64 := e2fffce6c95c367c8441c194ecb9dadbf5c394a834a6b8d4535b550694a3e03ca0d41183818a7623a2a09e934d49522d8b9721d838ba77d8a675c15e376ac162

# For kubelet versions >= 1.31.0, the slim image is the default one, and previous image is labeled as -fat.
# For kubelet versions < 1.31.0, the fat image is the default one, and previous image is labeled as -slim.
Expand All @@ -33,8 +31,6 @@ COMMON_ARGS += --build-arg=REGISTRY_AND_USERNAME=$(REGISTRY_AND_USERNAME)
COMMON_ARGS += --build-arg=NAME=$(NAME)
COMMON_ARGS += --build-arg=TAG=$(TAG)
COMMON_ARGS += --build-arg=KUBELET_VER=$(KUBELET_VER)
COMMON_ARGS += --build-arg=KUBELET_SHA512_AMD64=$(KUBELET_SHA512_AMD64)
COMMON_ARGS += --build-arg=KUBELET_SHA512_ARM64=$(KUBELET_SHA512_ARM64)

KRES_IMAGE ?= ghcr.io/siderolabs/kres:latest

Expand All @@ -57,13 +53,6 @@ docker-%: ## Builds the specified target defined in the Dockerfile using the def
container:
@$(MAKE) docker-$@ TARGET_ARGS="--push=$(PUSH)"

.PHONY: update-sha
update-sha: update-sha-amd64 update-sha-arm64 ## Updates the kubelet sha512 checksums in the Makefile.

update-sha-%:
sha512=`curl -sL https://dl.k8s.io/release/$(KUBELET_VER)/bin/linux/${*}/kubelet.sha512`; \
sed -i "s/KUBELET_SHA512_$(shell echo '$*' | tr '[:lower:]' '[:upper:]') := .*/KUBELET_SHA512_$(shell echo '$*' | tr '[:lower:]' '[:upper:]') := $${sha512}/" Makefile

.PHONY: rekres
rekres:
@docker pull $(KRES_IMAGE)
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