attest: add a kms input for KMS signing, and fix the dist rebuild push

.github/workflows/build-attest-dist.yaml

@@ -9,6 +9,7 @@ on:
       - 'attest/index.js'
       - 'attest/package.json'
       - 'attest/package-lock.json'
+      - '.github/workflows/build-attest-dist.yaml'
   workflow_dispatch:
 
 permissions:
@@ -50,6 +51,8 @@ jobs:
         if: github.event_name == 'pull_request'
         env:
           PR_HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          PR_HEAD_REF: ${{ github.event.pull_request.head.ref }}
+          PR_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
           BASE_REPO: ${{ github.repository }}
         run: |
           # SECURITY: only act if the rebuild produced exactly one
@@ -88,4 +91,9 @@ jobs:
           git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
           git add attest/dist/index.js
           git commit -m "chore(attest): rebuild dist/index.js"
-          git push
+          # The checkout is the PR head SHA, a detached HEAD, so name the
+          # PR branch. The lease makes the push land only while the branch
+          # still points at the SHA this run built from; if it moved in any
+          # direction or was deleted, the push is rejected.
+          git push --force-with-lease="refs/heads/$PR_HEAD_REF:$PR_HEAD_SHA" \
+            origin "HEAD:refs/heads/$PR_HEAD_REF"

attest/README.md

@@ -47,18 +47,41 @@ If your environment cannot submit to the public Sigstore transparency
 log (e.g. customers in the USA / EU with data-residency requirements),
 use one of:
 
-- **KMS signing**: `--kms vault://<key-id>` (HashiCorp Vault transit).
-  The signature stays in your control. Vault transit is the only KMS
-  backend implemented today.
+- **KMS signing**: `kms: vault://<key-name>` (HashiCorp Vault transit).
+  The private key never leaves Vault; cimon sends the digest and receives
+  the signature. Vault transit is the only KMS backend implemented today,
+  and it requires cimon v1.0.28 or later.
 - **Keyed signing with checked-in private key**: `sign-key: private-key.pem`.
 - **Private Sigstore**: deploy your own Fulcio + Rekor and pass
   `fulcio-server-url` + `rekor-server-url`.
 
 See the inputs section below for the full list.
 
+### KMS signing with HashiCorp Vault transit
+
+cimon reads the Vault connection from the standard Vault environment
+variables (`VAULT_ADDR`, `VAULT_TOKEN`, and optionally `VAULT_NAMESPACE`
+and `VAULT_CACERT`). The transit engine must be mounted at `transit/`, and
+the key must support signing (for example `ecdsa-p256` or `rsa-3072`):
+
+```yaml
+- uses: cycodelabs/cimon-action/attest@v1
+  env:
+    VAULT_ADDR: https://vault.example.com:8200
+    VAULT_TOKEN: ${{ secrets.VAULT_TOKEN }}
+  with:
+    subjects: dist\my-app.msi
+    kms: vault://cimon-signing
+    fail-on-error: true
+```
+
+Verifiers need the key's public half, which Vault returns from
+`transit/keys/<key-name>`:
+`cimon attest verify --key public-key.pem --signed-prov provenance.intoto.jsonl.sig`.
+
 ### Timestamping key-based signatures
 
-A signature made with `sign-key` carries no time anchor unless you add an
+A signature made with `sign-key` or `kms` carries no time anchor unless you add an
 RFC 3161 timestamp, which lets a verifier show it was made before the
 key was rotated or revoked. Request one explicitly; `timestamp-server-url`
 accepts a Sigstore timestamp authority or a standard RFC 3161 service:
@@ -89,12 +112,13 @@ releases accept these inputs and produce no timestamp.
 | `source-path` | Path to the source checkout recorded in the attestation. Unset means automatic discovery (subject paths, run-id directory, workspace). Requires cimon v1.0.24 or later | — |
 | `skip-source-tree-check` | Skip verifying the source tree matches the recorded commit | `false` |
 | `sign-key` | Path to a private ECDSA/RSA/ED25519 PEM key | — |
+| `kms` | KMS key URI for signing. HashiCorp Vault transit: `vault://<key-name>`, configured through `VAULT_ADDR` and `VAULT_TOKEN`. Requires cimon v1.0.28 or later | — |
 | `keyless` | Use keyless (Sigstore) signing | `false` |
 | `tlog-upload` | **Keyless only.** Upload signature to Rekor transparency log | `true` |
-| `include-timestamp` | Request an RFC 3161 timestamp and embed it in the signature. Applies to `keyless` and `sign-key` signing | `false` |
+| `include-timestamp` | Request an RFC 3161 timestamp and embed it in the signature. Applies to `keyless`, `sign-key` and `kms` signing | `false` |
 | `fulcio-server-url` | **Keyless only.** Fulcio server URL | `https://fulcio.sigstore.dev` |
 | `rekor-server-url` | **Keyless only.** Rekor server URL | `https://rekor.sigstore.dev` |
-| `timestamp-server-url` | RFC 3161 timestamp server URL: a Sigstore timestamp authority or a standard RFC 3161 service. With `sign-key`, forwarded only when `include-timestamp: true` | — |
+| `timestamp-server-url` | RFC 3161 timestamp server URL: a Sigstore timestamp authority or a standard RFC 3161 service. With `sign-key` or `kms`, forwarded only when `include-timestamp: true` | — |
 | `allow-submit-data-to-public-sigstore` | **Keyless only.** Required when using public Sigstore | `false` |
 | `provenance-output` | Path for unsigned provenance | `provenance.intoto.jsonl` |
 | `signed-provenance-output` | Path for signed provenance | `provenance.intoto.jsonl.sig` |

attest/action.yml

@@ -43,6 +43,10 @@ inputs:
     description: Input path to a private ECDSA/RSA/ED25519 key used to sign provenance statement
     required: false
     default: ''
+  kms:
+    description: 'KMS key used to sign provenance statement, as a provider URI. HashiCorp Vault transit: vault://<key-name>, with the Vault address and token in the VAULT_ADDR and VAULT_TOKEN environment variables. Requires cimon v1.0.28 or later.'
+    required: false
+    default: ''
   keyless:
     description: Allow keyless signature if no signing key is provided
     required: false
@@ -52,7 +56,7 @@ inputs:
     required: false
     default: 'true'
   include-timestamp:
-    description: 'Request an RFC 3161 timestamp of the artifact signature from a timestamping authority. Applies to keyless and sign-key signing.'
+    description: 'Request an RFC 3161 timestamp of the artifact signature from a timestamping authority. Applies to keyless, sign-key and kms signing.'
     required: false
     default: 'false'
   fulcio-server-url:
@@ -64,7 +68,7 @@ inputs:
     required: false
     default: 'https://rekor.sigstore.dev'
   timestamp-server-url:
-    description: 'RFC 3161 timestamp server URL: a Sigstore timestamp authority or a standard RFC 3161 service. With sign-key, forwarded only when include-timestamp is true.'
+    description: 'RFC 3161 timestamp server URL: a Sigstore timestamp authority or a standard RFC 3161 service. With sign-key or kms, forwarded only when include-timestamp is true.'
     required: false
   allow-submit-data-to-public-sigstore:
     description: 'Keyless signing only: agree to submit data to an immutable public transparency log (needed for public Sigstore). Ignored unless keyless is true.'

attest/dist/index.js

@@ -127691,6 +127691,7 @@ function getActionConfig() {
             subjects: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getInput('subjects'),
             imageRef: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getInput('image-ref'),
             signKey: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getInput('sign-key'),
+            kms: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getInput('kms'),
             keyless: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getBooleanInput('keyless'),
             tlogUpload: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getBooleanInput('tlog-upload'),
             includeTimestamp: _actions_core__WEBPACK_IMPORTED_MODULE_0__.getBooleanInput('include-timestamp'),
@@ -127793,6 +127794,7 @@ async function run(config) {
     if (config.attest.signedProvenanceOutput !== '')
         args.push('--output-signed-prov', config.attest.signedProvenanceOutput);
     if (config.attest.signKey !== '') args.push('--key', config.attest.signKey);
+    if (config.attest.kms !== '') args.push('--kms', config.attest.kms);
     if (config.attest.sourcePath !== '')
         args.push('--source-path', config.attest.sourcePath);
     if (config.attest.skipSourceTreeCheck)
@@ -127804,6 +127806,8 @@ async function run(config) {
     if (config.cimon.logLevel !== '')
         args.push('--log-level', config.cimon.logLevel);
     if (config.report.reportJobSummary) args.push('--report-job-summary');
+    const keyBasedSigning =
+        config.attest.signKey !== '' || config.attest.kms !== '';
     if (config.attest.keyless) {
         args.push('--keyless');
 
@@ -127824,8 +127828,8 @@ async function run(config) {
                 `--timestamp-server-url=${config.attest.timestampServerUrl}`
             );
         }
-    } else if (config.attest.signKey !== '' && config.attest.includeTimestamp) {
-        // Key-based signing only timestamps on an explicit request, so the
+    } else if (keyBasedSigning && config.attest.includeTimestamp) {
+        // Key and KMS signing only timestamp on an explicit request, so the
         // inputs are forwarded only when include-timestamp is true. Older
         // cimon releases accept and ignore them.
         args.push('--include-timestamp=true');
@@ -127855,7 +127859,7 @@ async function run(config) {
             path__WEBPACK_IMPORTED_MODULE_5__.dirname(config.attest.provenanceOutput),
             { continueOnError: true }
         );
-        if (config.attest.signKey !== '') {
+        if (keyBasedSigning) {
             client.uploadArtifact(
                 `signed-provenance-${jobId}-${randomSuffix}`,
                 [config.attest.signedProvenanceOutput],

attest/index.js

@@ -131,6 +131,7 @@ function getActionConfig() {
             subjects: core.getInput('subjects'),
             imageRef: core.getInput('image-ref'),
             signKey: core.getInput('sign-key'),
+            kms: core.getInput('kms'),
             keyless: core.getBooleanInput('keyless'),
             tlogUpload: core.getBooleanInput('tlog-upload'),
             includeTimestamp: core.getBooleanInput('include-timestamp'),
@@ -233,6 +234,7 @@ async function run(config) {
     if (config.attest.signedProvenanceOutput !== '')
         args.push('--output-signed-prov', config.attest.signedProvenanceOutput);
     if (config.attest.signKey !== '') args.push('--key', config.attest.signKey);
+    if (config.attest.kms !== '') args.push('--kms', config.attest.kms);
     if (config.attest.sourcePath !== '')
         args.push('--source-path', config.attest.sourcePath);
     if (config.attest.skipSourceTreeCheck)
@@ -244,6 +246,8 @@ async function run(config) {
     if (config.cimon.logLevel !== '')
         args.push('--log-level', config.cimon.logLevel);
     if (config.report.reportJobSummary) args.push('--report-job-summary');
+    const keyBasedSigning =
+        config.attest.signKey !== '' || config.attest.kms !== '';
     if (config.attest.keyless) {
         args.push('--keyless');
 
@@ -264,8 +268,8 @@ async function run(config) {
                 `--timestamp-server-url=${config.attest.timestampServerUrl}`
             );
         }
-    } else if (config.attest.signKey !== '' && config.attest.includeTimestamp) {
-        // Key-based signing only timestamps on an explicit request, so the
+    } else if (keyBasedSigning && config.attest.includeTimestamp) {
+        // Key and KMS signing only timestamp on an explicit request, so the
         // inputs are forwarded only when include-timestamp is true. Older
         // cimon releases accept and ignore them.
         args.push('--include-timestamp=true');
@@ -295,7 +299,7 @@ async function run(config) {
             path.dirname(config.attest.provenanceOutput),
             { continueOnError: true }
         );
-        if (config.attest.signKey !== '') {
+        if (keyBasedSigning) {
             client.uploadArtifact(
                 `signed-provenance-${jobId}-${randomSuffix}`,
                 [config.attest.signedProvenanceOutput],