feat: update Gradle builder to accomodate for e2e test (#2636)

1. Add two public download actions
2. Add option for specifying a path to the Gradle project

I found these changes to be necessary to run [the Gradle e2e
test](slsa-framework/example-package#270).

---------

Signed-off-by: AdamKorcz <44787359+AdamKorcz@users.noreply.github.com>
Signed-off-by: AdamKorcz <adam@adalogics.com>
Co-authored-by: laurentsimon <64505099+laurentsimon@users.noreply.github.com>

.github/workflows/builder_gradle_slsa3.yml

@@ -31,6 +31,11 @@ on:
         required: false
         default: 17
         type: number
+      directory:
+        description: "Sub-directory to launch the build from. Must be under the workspace. Relative from the root of the file directory when invoking the builder."
+        required: false
+        type: string
+        default: "."
     outputs:
       provenance-name:
         description: "The file name of the attestation upload artifact."

actions/gradle/secure-download-attestations/action.yml

@@ -0,0 +1,36 @@
+# Copyright 2023 SLSA Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "Secure attestion download for maven builder"
+description: "Download the attestations-directory produced by the Maven builder and verify its SHA256"
+inputs:
+  name:
+    description: "Name of provenance directory. This is generated by the Maven builder."
+    required: true
+  path:
+    description: "The path to download the attestations directory into. (Must be under the GITHUB_WORKSPACE)"
+    required: true
+  sha256:
+    description: "SHA256 of the file for verification. This is generated by the Maven builder"
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Download the attestation directory
+      uses: slsa-framework/slsa-github-generator/.github/actions/secure-download-folder@main
+      with:
+        name: ${{ inputs.name }}
+        path: ${{ inputs.path }}
+        sha256: ${{ inputs.sha256 }}

actions/gradle/secure-download-target/action.yml

@@ -0,0 +1,36 @@
+# Copyright 2023 SLSA Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "Secure target directory download for maven builder"
+description: "Download the 'target'-directory and verify its SHA256"
+inputs:
+  name:
+    description: "Name of the target directory. The Maven builder makes this 'target'."
+    required: true
+  path:
+    description: "The path to download the target directory into. (Must be under the GITHUB_WORKSPACE)"
+    required: true
+  sha256:
+    description: "SHA256 of the file for verification."
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Download the target directory
+      uses: slsa-framework/slsa-github-generator/.github/actions/secure-download-folder@main
+      with:
+        name: ${{ inputs.name }}
+        path: ${{ inputs.path }}
+        sha256: ${{ inputs.sha256 }}

internal/builders/gradle/action.yml

@@ -60,24 +60,59 @@ runs:
         java-version: ${{ fromJson(inputs.slsa-workflow-inputs).jdk-version }}
     - name: Setup Gradle
       uses: gradle/gradle-build-action@a4cf152f482c7ca97ef56ead29bf08bcd953284c # v2.7.0
-      with:
-        arguments: build -x test
+    - name: Run gradle builder
+      shell: bash
+      env:
+        UNTRUSTED_PROJECT_ROOT: ${{ fromJson(inputs.slsa-workflow-inputs).directory }}
+      run: |
+        # Ensure no directory traversal.
+        # NOTE: the actions/download-artifact Action only creates files
+        # in the workspace directory, but this may change in the future.
+        # TODO(#1893): Consolidate directory traversal checks
+        validate_path() {
+          untrusted_path=$1
+          resolved_dir=$(readlink -m "$untrusted_path")
+          wd=$(readlink -m "${GITHUB_WORKSPACE}")
+          if [[ "${resolved_dir}" != "${wd}"/* ]] && [[ "${resolved_dir}" != "${wd}" ]]; then
+            if [[ "${RUNNER_TEMP}" != "" ]] && [[ "${resolved_dir}" != "${RUNNER_TEMP}"/* ]] && [[ "${resolved_dir}" != "${RUNNER_TEMP}" ]]; then
+              if [[ "${resolved_dir}" != /tmp/* ]] && [[ "${resolved_dir}" != "/tmp" ]]; then
+                echo "Path is not in the workspace or temp directory: $untrusted_path"
+                exit 1
+              fi
+            fi
+          fi
+        }
+        validate_path "${UNTRUSTED_PROJECT_ROOT}"
+        # remove trailing "/"'s with `realpath`
+        project_root=$(realpath "${UNTRUSTED_PROJECT_ROOT}")
+
+        cd "${project_root}" \
+          && ./gradlew build -x test
+
     - name: Put release artifacts in one directory
       shell: bash
       env:
         SLSA_OUTPUTS_ARTIFACTS_FILE: ${{ inputs.slsa-layout-file }}
-        ARTIFACT_LIST: ${{ fromJson(inputs.slsa-workflow-inputs).artifact-list }}
-      run: ./../__TOOL_ACTION_DIR__/collect_release_artifacts.sh
-    - name: Upload built artifacts from gradlew build
-      uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # v3.1.2
-      with:
-        path: ./release-files-for-slsa/*
+        UNTRUSTED_ARTIFACT_LIST: ${{ fromJson(inputs.slsa-workflow-inputs).artifact-list }}
+        PROJECT_ROOT: ${{ fromJson(inputs.slsa-workflow-inputs).directory }}
+      run: |
+        cd "${PROJECT_ROOT}" && "${GITHUB_WORKSPACE}"/../__TOOL_ACTION_DIR__/collect_release_artifacts.sh
     - name: Make outputs
       id: make-outputs
       shell: bash
       env:
         SLSA_OUTPUTS_ARTIFACTS_FILE: ${{ inputs.slsa-layout-file }}
-      run: ./../__TOOL_ACTION_DIR__/create_attestation.sh
+        PROJECT_ROOT: ${{ fromJson(inputs.slsa-workflow-inputs).directory }}
+      run: |
+        cd "${PROJECT_ROOT}" && "${GITHUB_WORKSPACE}"/../__TOOL_ACTION_DIR__/create_attestation.sh
+    - name: Move build dir to avoid making it a sub-dir when uploading
+      shell: bash
+      env:
+        # PROJECT_ROOT is generally untrusted, but the builder has validated
+        # it in the 'Run gradle builder' step and is therefore trusted now.
+        PROJECT_ROOT: ${{ fromJson(inputs.slsa-workflow-inputs).directory }}
+      run: |
+        mv "${PROJECT_ROOT}"/build "${GITHUB_WORKSPACE}"/
     - name: Upload build dir
       id: upload-build-dir
       uses: slsa-framework/slsa-github-generator/.github/actions/secure-upload-folder@main

internal/builders/gradle/collect_release_artifacts.sh

@@ -20,7 +20,7 @@ mkdir release-files-for-slsa
 GRADLE_VERSION=$(./gradlew properties -q | grep "version:" | awk '{print $2}')
 
 # Move artifacts from the user-supplied artifact list
-IFS=',' read -ra artifact_array <<< "$ARTIFACT_LIST"
+IFS=',' read -ra artifact_array <<< "$UNTRUSTED_ARTIFACT_LIST"
 for i in "${artifact_array[@]}"
 do
     i="${i#"${i%%[![:space:]]*}"}" # trim leading whitespace                                                                                                                                                                                                                                                                                                                                         
@@ -38,5 +38,5 @@ do
 
     # Move the file
     bn=$(basename -- "$path_with_version")
-    mv "$path_with_version" release-files-for-slsa/"$bn"
+    cp "$path_with_version" release-files-for-slsa/"$bn"
 done

internal/builders/gradle/create_attestation.sh

@@ -16,6 +16,8 @@
 
 set -euo pipefail
 
+SLSA_OUTPUTS_ARTIFACTS_FILE="${GITHUB_WORKSPACE}/${SLSA_OUTPUTS_ARTIFACTS_FILE}"
+
 # "version" and "attestations" fields:
 echo -e -n "{\n  \"version\": 1,\n  \"attestations\": [" >> "$SLSA_OUTPUTS_ARTIFACTS_FILE"