feat(cosign): Making Cosign installation optional

.github/workflows/main.yml

@@ -11,29 +11,31 @@ jobs:
     name: Test regctl-installer Action
     runs-on: ${{ matrix.os }}
     strategy:
-      fail-fast: true
+      fail-fast: false # let other tests finish
       matrix:
         os: [macos-latest, ubuntu-latest, windows-latest]
+        cosign: [true, false]
 
     steps:
       - name: Checkout repo
         uses: actions/checkout@v3
 
+      - name: Install Cosign
+        uses: sigstore/cosign-installer@v3.0.1
+        if: matrix.cosign
+
       - name: Install regctl
         uses: ./
 
       - name: Test regctl
-        run: |
-          regctl version
-          regctl tag ls caddy
-          regctl image digest nginx:latest
-          regctl image manifest alpine:3.11
+        run: regctl version
 
   main:
-    if: ${{ github.event_name == 'push' }}
     name: Publish new version
     runs-on: ubuntu-latest
     needs: [test]
+
+    if: github.event_name == 'push'
     steps:
       - name: Checkout repo
         uses: actions/checkout@v3

README.md

@@ -5,7 +5,7 @@
 [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/IAreKyleW00t/regctl-installer/main.yml)](https://github.com/IAreKyleW00t/regctl-installer/actions/workflows/main.yml)
 [![License](https://img.shields.io/github/license/IAreKyleW00t/regctl-installer)](https://github.com/IAreKyleW00t/regctl-installer/blob/main/LICENSE)
 
-This GitHub Action enables you to interacting with remote images and registries using [`regctl`](https://github.com/google/go-containerregistry/tree/main/cmd/regctl). This action will verify the integrity of the `regctl` release during installation using [Cosign](https://docs.sigstore.dev/cosign/overview/).
+This GitHub Action enables you to interacting with remote images and registries using [`regctl`](https://github.com/google/go-containerregistry/tree/main/cmd/regctl). This action will verify the integrity of the `regctl` release during installation if you setup [Cosign](https://docs.sigstore.dev/cosign/overview/) ahead of time (see examples below).
 
 For a quick start guide on the usage of `regctl`, please refer to https://github.com/regclient/regclient/blob/main/docs/regctl.md. For available regctl releases, see https://github.com/regclient/regclient/releases.
 
@@ -18,6 +18,7 @@ For a quick start guide on the usage of `regctl`, please refer to https://github
   - [Pinned version](#pinned-version)
   - [Default version](#pinned-version)
   - [Authenicate on other registries](#authenticate-on-other-registries)
+  - [Automatic validation with Cosign](#automatic-validation-with-cosign)
 
 ## Tags
 
@@ -93,6 +94,21 @@ jobs:
             --pass-stdin
 ```
 
+### Automatic validation with Cosign
+
+```yaml
+jobs:
+  regctl:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Cosign
+        uses: sigstore/cosign-installer@v3.0.1
+      - name: Install regctl
+        uses: iarekylew00t/regctl-installer@v1
+      - name: Check install
+        run: regctl version
+```
+
 ## Contributing
 
 Feel free to contribute and make things better by opening an [Issue](https://github.com/IAreKyleW00t/regctl-installer/issues) or [Pull Request](https://github.com/IAreKyleW00t/regctl-installer/pulls).

action.yml

@@ -26,7 +26,6 @@ inputs:
 runs:
   using: "composite"
   steps:
-    - uses: sigstore/cosign-installer@v3.0.1
     - shell: bash
       run: |
         #!/bin/bash
@@ -66,15 +65,18 @@ runs:
         curl -fsSL "https://github.com/regclient/regclient/releases/download/${VERSION}/regctl-${OS}-${ARCH}${BIN_SUFFIX}" > "${{ inputs.install-dir }}/regctl${BIN_SUFFIX}"
         chmod 755 "${{ inputs.install-dir }}/regctl${BIN_SUFFIX}"
 
-        # Validate download
-        curl -fsSL https://github.com/regclient/regclient/releases/latest/download/metadata.tgz > metadata.tgz
-        tar -xzf metadata.tgz regctl-${OS}-${ARCH}.pem regctl-${OS}-${ARCH}.sig
-        cosign verify-blob \
-          --certificate-oidc-issuer https://token.actions.githubusercontent.com \
-          --certificate-identity-regexp https://github.com/regclient/regclient/.github/workflows/ \
-          --certificate regctl-${OS}-${ARCH}.pem \
-          --signature regctl-${OS}-${ARCH}.sig \
-          "${{ inputs.install-dir }}/regctl${BIN_SUFFIX}"
+        # Validate download (if cosign is setup)
+        if which cosign >/dev/null; then
+          curl -fsSL https://github.com/regclient/regclient/releases/latest/download/metadata.tgz > metadata.tgz
+          tar -xzf metadata.tgz regctl-${OS}-${ARCH}.pem regctl-${OS}-${ARCH}.sig
+          cosign verify-blob \
+            --certificate-oidc-issuer https://token.actions.githubusercontent.com \
+            --certificate-identity-regexp https://github.com/regclient/regclient/.github/workflows/ \
+            --certificate regctl-${OS}-${ARCH}.pem \
+            --signature regctl-${OS}-${ARCH}.sig \
+            "${{ inputs.install-dir }}/regctl${BIN_SUFFIX}"
+          rm -rf metadata.tgz regctl-${OS}-${ARCH}.pem regctl-${OS}-${ARCH}.sig
+        fi
 
     - if: ${{ runner.os == 'Linux' || runner.os == 'macOS' }}
       run: echo "${{ inputs.install-dir }}" >> $GITHUB_PATH