feat(sign): support for keyless signing and offline verification by brandtkeller · Pull Request #4891 · zarf-dev/zarf

brandtkeller · 2026-05-11T23:21:30Z

Description

Note - Breaking Changes

The cosign functionality under src/pkg/utils has been moved to `src/pkg/signing
The embedded structs in signing.Sign|VerifyBlobOptions have been updated to align with cosign.

This PR enables the use of connected keyless signing workflows and offline-compatible verification for a keyless signed package via an embedded trusted root.

This uses the previously implemented zarf tools trusted-root create command to refresh the embedded trusted root. Think of this as a mechanism to streamline the UX of enabling offline verification of keyless-signed packages so that users are not required to bring additional verification material by default - but of which they can overwrite as required.

Additionally this PR enables the bundlesignature feature by default. Note that the VersionRequirement for a package with a bundle signature is v0.71.0 which is the version that introduced the ability to load packages with the bundle file. The feature flag gates are retained such that users who cannot use the bundle still have an opportunity to opt-out until we fully remove.

One early improvement is the UX of retrieving the keyless-signed identity and issuer. These are retrieved on package sign so that we can log the entries that package creators need to provide to those who want to verify - but additionally I believe we could add a zarf package inspect signature <package> command to make this discoverable. We can't place it directly in the build data because it is only accessible post-signing - whereby the zarf definition can no longer be modified without invalidating the signature.

Best practices documentation to follow.

Try it Yourself

# Build the CLI
make build

# Pull a package for signing
zarf tools download-init

# Sign the package (this will conduct browser auth)
./build/zarf package sign zarf-init-arm64-v0.75.0.tar.zst --keyless

# (optional) turn off wifi

# Verify the package
./build/zarf package verify zarf-init-arm64-v0.75.0.tar.zst --certificate-identity brandt.keller@defenseunicorns.com --certificate-oidc-issuer https://github.com/login/oauth

Related Issue

Fixes #2805
Fixes #4571

Relates to #

Checklist before merging

Test, docs, adr added or updated as needed
Contributor Guide Steps followed

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

…_flags

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

…_flags

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

codecov · 2026-05-11T23:24:43Z

Codecov Report

❌ Patch coverage is 40.37855% with 189 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/cmd/package.go	19.62%	86 Missing ⚠️
src/pkg/utils/oci_artifacts.go	0.00%	39 Missing ⚠️
src/pkg/packager/layout/package.go	70.00%	16 Missing and 5 partials ⚠️
src/pkg/signing/cosign.go	5.00%	19 Missing ⚠️
src/pkg/signing/trustedroot.go	30.76%	6 Missing and 3 partials ⚠️
src/pkg/packager/publish.go	0.00%	4 Missing and 3 partials ⚠️
src/pkg/signing/bundle.go	88.88%	4 Missing and 1 partial ⚠️
src/cmd/tools_trustedroot.go	0.00%	1 Missing ⚠️
src/pkg/packager/load.go	0.00%	1 Missing ⚠️
src/pkg/packager/pull.go	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/cmd/viper.go	`60.19% <100.00%> (+4.28%)`	⬆️
src/pkg/feature/feature.go	`91.12% <100.00%> (ø)`
src/pkg/packager/layout/assemble.go	`43.17% <100.00%> (ø)`
src/cmd/tools_trustedroot.go	`75.64% <0.00%> (ø)`
src/pkg/packager/load.go	`62.89% <0.00%> (ø)`
src/pkg/packager/pull.go	`50.00% <0.00%> (ø)`
src/pkg/signing/bundle.go	`88.88% <88.88%> (ø)`
src/pkg/packager/publish.go	`63.10% <0.00%> (-3.21%)`	⬇️
src/pkg/signing/trustedroot.go	`30.76% <30.76%> (ø)`
src/pkg/signing/cosign.go	`1.01% <5.00%> (ø)`
... and 3 more

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

…o 2805_keyless_signing

…tion Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

netlify · 2026-05-12T19:04:59Z

✅ Deploy Preview for zarf-docs canceled.

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🔍 Latest deploy log	https://app.netlify.com/projects/zarf-docs/deploys/6a0549920bad3d00087a05f0

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller · 2026-05-13T01:29:18Z

+#!/usr/bin/env bash
+# Refresh the embedded Sigstore TrustedRoot used for keyless verification.
+# Run before each release. Commit the result.
+


Making a mental note to schedule daily checks and notify the zarf channel using this process. A lag in releasing new trusted roots won't be critical but should be nice to have.

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

AustinAbro321

Excited how signing is taking shape, no doubt this will improve the UX

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller · 2026-05-13T19:37:22Z

+)
+
+// GetCosignArtifacts returns signatures and attestations for the given image.
+func GetCosignArtifacts(image string) ([]string, error) {


I kept this function in utils - it is not soo much a signing function as it is a helper for signature/attestation retrieval.

Co-authored-by: Austin Abro <37223396+AustinAbro321@users.noreply.github.com> Signed-off-by: Brandt Keller <43887158+brandtkeller@users.noreply.github.com>

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

AustinAbro321 · 2026-05-14T14:03:07Z

+// BundleInfo contains parsed metadata from a Sigstore bundle file.
+type BundleInfo struct {
+	// Method is "keyless" for Fulcio-issued certificate bundles, "key" for public-key bundles.
+	Method   string


nit: can we make this an enum

AustinAbro321 · 2026-05-14T14:11:02Z

+
+	// Keyless signatures require bundle format — the cert chain cannot be stored in the
+	// legacy .sig file. For key-based signing, respect the BundleSignature feature flag.
+	bundleEnabled := feature.IsEnabled(feature.BundleSignature) || opts.Keyless


nit: I think it makes more sense to error if the feature is not enabled and keyless is true. Probably doesn't matter much now that we're enabled by default, but that's the preferred pattern for the codebase imo

AustinAbro321 · 2026-05-14T14:17:28Z

+// ReadKeylessIdentityFromBundle parses a Sigstore bundle file and returns the
+// signer identity (cert SAN) and OIDC issuer claim. Returns an error if the
+// bundle does not contain a certificate (i.e. is not a keyless signature).
+func ReadKeylessIdentityFromBundle(bundlePath string) (identity, issuer string, err error) {


This function is not used

AustinAbro321 · 2026-05-14T14:23:38Z

+// extractIdentityFromCert extracts the signer identity (cert SAN) and OIDC issuer
+// from a Fulcio-issued X.509 certificate using Sigstore OID extensions.
+// SAN priority: email > URI > DNS. OID priority: V2 > legacy.
+func extractIdentityFromCert(cert *x509.Certificate) (identity, issuer string) {


I believe we can replace this function with github.com/sigstore/sigstore-go/pkg/fulcio/certificate.SummarizeCertificate

AustinAbro321 · 2026-05-14T14:31:23Z

+	if o.keyless && !cmd.Flags().Changed("tlog-upload") {
+		signOpts.TlogUpload = true
+	}


Is the current plan to support tsa using the same enable flag if keyless method? Cosign does use tsa by default and our default trusted root has the timestampAuthorities field

brandtkeller added 16 commits May 7, 2026 22:15

feat(sign): align signing and verification to cosign

895809a

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

chore(docs): update comments and language

972fa31

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(cosign): implement non-prompting passfunc

762484e

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

feat(sign): support for embedded TrustedRoot

30bbdbd

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

feat(sign): enable keyless signing and verification

17dfcd1

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(options): deprecate duplicitive fields

cab4e08

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

Merge branch 'main' of github.com:zarf-dev/zarf into 4572_sign_verify…

bfd2a5f

…_flags

fix(flags): review flags that can be further hidden based on utility

4f2d01e

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(flags): trustedroot flag is not operational... yet

e30354e

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

Merge branch 'main' of github.com:zarf-dev/zarf into 4572_sign_verify…

4c26a4e

…_flags

chore(update): resolve changes from 4572 branch

1719f3b

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(sigstore): retrieve identity/issuer from bundle

fc8151b

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(cmd): explicit opt-in for cosign options/flags

7682107

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

choer(merge): merge 4572 into 2805

1fa7225

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

feat(sign): implement keyless signing options explicitly

bc9797d

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(sign): support for oci signing operations

6956676

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

github-project-automation Bot added this to Zarf May 11, 2026

brandtkeller added 4 commits May 12, 2026 03:17

fix(test): update error message for verification material

fa088d4

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(cosign): add timeout to verify

4f49439

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

Merge branch '4572_sign_verify_flags' of github.com:zarf-dev/zarf int…

650aebd

…o 2805_keyless_signing

fix(requirement): add version requirement for bundle signing verifica…

c49d85d

…tion Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

Base automatically changed from 4572_sign_verify_flags to main May 12, 2026 17:25

merge main into 2805_keyless_signing

69067ca

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller added 2 commits May 12, 2026 22:59

feat(sign): add signature build metadata for future utility

aed485c

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(bundle): implement generic bundle parsing

19259d7

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller commented May 13, 2026

View reviewed changes

chore: generate the updated schema

efb1d68

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller marked this pull request as ready for review May 13, 2026 01:48

brandtkeller requested review from a team as code owners May 13, 2026 01:48

brandtkeller added 2 commits May 13, 2026 01:52

fix(test): update test for error output

d73dcde

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(test): update expected errors

bcaa110

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

AustinAbro321 requested changes May 13, 2026

View reviewed changes

Comment thread src/pkg/packager/layout/package.go

Comment thread src/cmd/package.go

Comment thread src/cmd/package.go Outdated

Comment thread src/pkg/signing/bundle.go

Comment thread src/api/v1alpha1/package.go Outdated

Comment thread src/pkg/packager/layout/package.go Outdated

github-project-automation Bot moved this to In progress in Zarf May 13, 2026

brandtkeller added 3 commits May 13, 2026 19:05

feat(signing): isolate cosign signing and verification into new package

0e6a4e2

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

fix(schema): remove signature field and regen schema

bcccd08

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

move deprecation logic earlier in the chain

2487805

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller commented May 13, 2026

View reviewed changes

brandtkeller requested a review from AustinAbro321 May 13, 2026 20:18

AustinAbro321 requested changes May 13, 2026

View reviewed changes

Comment thread hack/refresh-trusted-root.sh Outdated

Update hack/refresh-trusted-root.sh

cfe6743

Co-authored-by: Austin Abro <37223396+AustinAbro321@users.noreply.github.com> Signed-off-by: Brandt Keller <43887158+brandtkeller@users.noreply.github.com>

brandtkeller mentioned this pull request May 14, 2026

feat(sign): support for sigstore bundle format #4369

Closed

2 tasks

feat(cmd): support signing/verify viper configuration

3f63c37

Signed-off-by: Brandt Keller <brandt.keller@defenseunicorns.com>

brandtkeller mentioned this pull request May 14, 2026

Trusted Signers viper configuration #4899

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AustinAbro321 reviewed May 14, 2026

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Description

Try it Yourself

Related Issue

Checklist before merging

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