workflows: Factor out artifact attestation and upload into a composite action (#169621)

Also, switch the release-sources workflow over to use this new action.
As a result of this change, the attestation file for the sources will be
renamed from attestation.jsonl to $TAG-sources-attestation.jsonl.

.github/workflows/release-sources.yml

@@ -64,11 +64,11 @@ jobs:
     name: Package Release Sources
     if: github.repository_owner == 'llvm'
     runs-on: ubuntu-24.04
+    outputs:
+      digest: ${{ steps.digest.outputs.digest }}
+      artifact-id: ${{ steps.artifact-upload.outputs.artifact-id }}
     needs:
       - inputs
-    permissions:
-      id-token: write
-      attestations: write
     steps:
       - name: Checkout LLVM
         uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
@@ -79,30 +79,47 @@ jobs:
         run: |
           pip install --require-hashes -r ./llvm/utils/git/requirements.txt
 
-      - name: Check Permissions
-        if: github.event_name != 'pull_request'
-        env:
-          GITHUB_TOKEN: ${{ github.token }}
-          USER_TOKEN: ${{ secrets.RELEASE_TASKS_USER_TOKEN }}
-        run: |
-          ./llvm/utils/release/./github-upload-release.py --token "$GITHUB_TOKEN" --user ${{ github.actor }} --user-token "$USER_TOKEN" check-permissions
       - name: Create Tarballs
         run: |
           ./llvm/utils/release/export.sh ${{ needs.inputs.outputs.export-args }}
-      - name: Attest Build Provenance
-        if: github.event_name != 'pull_request'
-        id: provenance
-        uses: actions/attest-build-provenance@977bb373ede98d70efdf65b84cb5f73e068dcc2a # v3.0.0
-        with:
-          subject-path: "*.xz"
-      - if: github.event_name != 'pull_request'
+
+      - name: Generate sha256 digest for sources
+        id: digest
         run: |
-          mv ${{ steps.provenance.outputs.bundle-path }} .
-      - name: Create Tarball Artifacts
+          echo "digest=$(cat *.xz | sha256sum | cut -d ' ' -f 1)" >> $GITHUB_OUTPUT
+    
+      - name: Release Sources Artifact
+        id: artifact-upload
         uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
         with:
+          name: ${{ needs.inputs.outputs.ref }}-sources
           path: |
             *.xz
-            attestation.jsonl
 
+  attest-release-sources:
+    name: Attest Release Sources
+    runs-on: ubuntu-24.04
+    if: github.event_name != 'pull_request'
+    needs:
+      - inputs
+      - release-sources
+    permissions:
+      id-token: write
+      attestations: write
+    steps:
+      - name: Checkout Release Scripts
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          sparse-checkout: |
+            .github/workflows/upload-release-artifact
+            llvm/utils/release/github-upload-release.py
+            llvm/utils/git/requirements.txt
+          sparse-checkout-cone-mode: false
 
+      - name: Upload Artifacts
+        uses: ./.github/workflows/upload-release-artifact
+        with:
+          artifact-id: ${{ needs.release-sources.outputs.artifact-id }}
+          attestation-name: ${{ needs.inputs.outputs.ref }}-sources-attestation
+          digest: ${{ needs.release-sources.outputs.digest }}
+          upload: false

.github/workflows/upload-release-artifact/action.yml

@@ -0,0 +1,105 @@
+name: Upload Release Artifact
+description: >-
+  Upload release artifact along with an attestation.  The action assumes that
+  the llvm-project repository has already been checked out.
+inputs:
+  release-version:
+    description: >-
+      The release where the artifact will be attached.
+    required: true
+  upload:
+    description: >-
+      Whether or not to upload the file and attestation to the release.  If this
+      is set to false, then the file will be uploaded to the job as an artifact,
+      but no atteastion will be generated and the artifact won't be uploaded
+      to the release.
+    default: true
+  user-token:
+    description: >-
+      Token with premissions to read llvm teams that is used to ensure that
+      the person who triggred the action has permission to upload artifacts.
+      This is required if upload is true.
+    requred: false
+  attestation-name:
+    description: >-
+      This will be used for the artifact name that is attached to the workflow and
+      will be used as the basename for the attestation file which will be called
+      $attestation-name.jsonl.  If this is not set, it will default
+      to the falue of `files`.
+    required: false
+  artifact-id:
+    description: >-
+      Artifact id of the artifact with the files to upload.
+    required: true
+  digest:
+    description: >-
+      sha256 digest to verify the authenticity of the files being uploaded.
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Download Artifact
+      uses: actions/download-artifact@018cc2cf5baa6db3ef3c5f8a56943fffe632ef53 # v6.0.0
+      id: download-artifact
+      with:
+        artifact-ids: ${{ inputs.artifact-id }}
+        path: downloads
+
+    # In theory github artifacts are immutable so we could just rely on using
+    # the artifact-id to download it, but just to be extra safe we want to
+    # generated a digest for the files we are uploading so we can verify it
+    # when downloading.
+    # See also: https://irsl.medium.com/github-artifact-immutability-is-a-lie-9b6244095694
+    - name: Verify Files
+      shell: bash
+      env:
+        INPUTS_DIGEST: ${{ inputs.digest }}
+      run: |
+        digest_file="sha256"
+        echo "$INPUTS_DIGEST -" > $digest_file
+        cat ${{ steps.download-artifact.outputs.download-path }}/* | sha256sum -c $digest_file
+
+    - name: Attest Build Provenance
+      id: provenance
+      uses: actions/attest-build-provenance@977bb373ede98d70efdf65b84cb5f73e068dcc2a # v3.0.0
+      with:
+        subject-path: ${{ steps.download-artifact.outputs.download-path }}/*
+
+    - name: Rename attestation file
+      shell: bash
+      env:
+        INPUTS_ATTESTATION_NAME: ${{ inputs.attestation-name }}
+      run: |
+        mv ${{ steps.provenance.outputs.bundle-path }} "$INPUTS_ATTESTATION_NAME".jsonl
+
+    - name: Upload Build Provenance
+      uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
+      with:
+        name: ${{ inputs.attestation-name }}
+        path: |
+          ${{ inputs.attestation-name }}.jsonl
+
+    - name: Install Python Requirements
+      if: inputs.upload == 'true'
+      shell: bash
+      run: |
+        pip install --require-hashes -r ./llvm/utils/git/requirements.txt
+
+    - name: Check Permissions
+      if: inputs.upload == 'true'
+      env:
+        GITHUB_TOKEN: ${{ github.token }}
+        USER_TOKEN: ${{ inputs.user-token }}
+      shell: bash
+      run: |
+        ./llvm/utils/release/./github-upload-release.py --token "$GITHUB_TOKEN" --user "$GITHUB_ACTOR" --user-token "$USER_TOKEN" check-permissions
+    - name: Upload Release
+      shell: bash
+      if: inputs.upload == 'true'
+      run: |
+        ./llvm/utils/release/github-upload-release.py \
+        --token ${{ github.token }} \
+        --release ${{ inputs.release-version }} \
+        upload \
+        --files ${{ steps.download-artifact.outputs.download-path }}/* ${{ steps.vars.outputs.attestation-name}}.jsonl