Add provenance for Haskell

internal/builders/generic/README.md

@@ -29,6 +29,7 @@ project simply generates provenance as a separate step in an existing workflow.
   - [Provenance for Bazel](#provenance-for-bazel)
   - [Provenance for Java](#provenance-for-java)
   - [Provenance for Rust](#provenance-for-rust)
+  - [Provenance for Haskell](#provenance-for-haskell)
 
 ---
 
@@ -403,7 +404,7 @@ jobs:
         run: |
           # Your normal build workflow targets here
           bazel build //path/to/target_binary //path/to_another/binary
-         
+
           # Copy the binaries.
           cp bazel-bin/path/to/target_binary .
           cp bazel-bin/path/to/another/binary .
@@ -425,7 +426,7 @@ jobs:
 ```
 
 4. Call the generic workflow to generate provenance by declaring the job below:
-  
+
 ```yaml
   provenance:
     needs: [build]
@@ -456,7 +457,7 @@ jobs:
         run: |
           # Your normal build workflow targets here
           bazel build //path/to/target_binary //path/to_another/binary
-         
+
           # Copy the binaries.
           cp bazel-bin/path/to/target_binary .
           cp bazel-bin/path/to/another/binary .
@@ -512,7 +513,7 @@ jobs:
         run: |
           # Your normal build workflow targets here
           mvn clean package
-          
+
           # Save the location of the maven output files for easier reference
           ARTIFACT_PATTERN=./target/$(mvn help:evaluate -Dexpression=project.artifactId -q -DforceStdout)-$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)*.jar
           echo "::set-output name=artifact_pattern::$ARTIFACT_PATTERN"
@@ -563,7 +564,7 @@ jobs:
         run: |
           # Your normal build workflow targets here
           mvn clean package
-          
+
           # Save the location of the maven output files for easier reference
           ARTIFACT_PATTERN=./target/$(mvn help:evaluate -Dexpression=project.artifactId -q -DforceStdout)-$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)*.jar
           echo "::set-output name=artifact_pattern::$ARTIFACT_PATTERN"
@@ -572,7 +573,7 @@ jobs:
         id: hash
         run: |
           echo "::set-output name=hashes::$(sha256sum ${{ steps.build.outputs.artifact_pattern }} | base64 -w0)"
-      
+
       - name: Upload build artifacts
         uses: actions/upload-artifact@3cea5372237819ed00197afe530f5a7ea3e805c8 # tag=v3
         with:
@@ -606,7 +607,7 @@ jobs:
 ```
 
 2. Add an `id: build` field to your gradle build ste:
- 
+
 ```yaml
     steps:
       [...]
@@ -665,7 +666,7 @@ jobs:
         id: hash
         run: |
           echo "::set-output name=hashes::$(sha256sum ./build/libs/* | base64 -w0)"
-      
+
       - name: Upload build artifacts
         uses: actions/upload-artifact@3cea5372237819ed00197afe530f5a7ea3e805c8 # tag=v3
         with:
@@ -778,4 +779,109 @@ jobs:
       base64-subjects: "${{ needs.build.outputs.hashes }}"
       upload-assets: true # Optional: Upload to a new release
 
-```
+```
+
+### Provenance for Haskell
+
+If you use [Haskell](https://www.haskell.org/) (either via
+[`cabal`](https://www.haskell.org/cabal/) or
+[`stack`](https://docs.haskellstack.org/en/stable/README/)) to generate your
+artifacts, you can easily generate SLSA3 provenance by updating your existing
+workflow with the steps indicated in the workflow below.
+
+1. Declare an `outputs` for the hashes:
+
+```yaml
+jobs:
+  build:
+    outputs:
+      hashes: ${{ steps.hash.outputs.hashes }}
+
+```
+
+2. Build your binaries. Then add a step to generate the provenance subjects as shown below. Update the sha256 sum arguments to include all binaries that you generate provenance for:
+
+```yaml
+    steps:
+      [...]
+      - name: Build using Haskell
+        run: |
+          # Your normal build workflow targets here.
+          cabal build  # or stack build
+
+          # Copy the binary to the root directory for easier reference
+          # For Cabal, use the following command
+          cp $(cabal list-bin .) .
+          # For Stack, use the following command instead
+          # cp $(stack path --local-install-root)/bin/target_binary .
+
+      # Generate the subject.
+      - name: Generate subject
+        id: hash
+        run: |
+          set -euo pipefail
+
+          echo "::set-output name=hashes::$(sha256sum target_binary | base64 -w0)"
+
+```
+
+3. Call the generic workflow to generate provenance by declaring the job below:
+
+```yaml
+  provenance:
+    needs: [build]
+    permissions:
+      actions: read   # To read the workflow path.
+      id-token: write # To sign the provenance.
+      contents: write # To add assets to a release.
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v1.2.0
+    with:
+      base64-subjects: "${{ needs.build.outputs.hashes }}"
+      upload-assets: true # Optional: Upload to a new release
+
+```
+
+All in all, it will look as the following:
+
+```yaml
+jobs:
+  build:
+    outputs:
+      hashes: ${{ steps.hash.outputs.hashes }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b # tag=v3
+      - name: Setup Haskell
+        uses: haskell/actions/setup@745062a754c3c4b70b87cb93937ad443096cc94d # tag=v1
+
+      - name: Build using Haskell
+        run: |
+          # Your normal build workflow targets here.
+          cabal build  # or stack build
+
+          # Copy the binary to the root directory for easier reference
+          # For Cabal, use the following command
+          cp $(cabal list-bin .) .
+          # For Stack, use the following command instead
+          # cp $(stack path --local-install-root)/bin/target_binary .
+
+      # Generate the subject.
+      - name: Generate subject
+        id: hash
+        run: |
+          set -euo pipefail
+
+          echo "::set-output name=hashes::$(sha256sum target_binary | base64 -w0)"
+
+  provenance:
+    needs: [build]
+    permissions:
+      actions: read   # To read the workflow path.
+      id-token: write # To sign the provenance.
+      contents: write # To add assets to a release.
+    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v1.2.0
+    with:
+      base64-subjects: "${{ needs.build.outputs.hashes }}"
+      upload-assets: true # Optional: Upload to a new release
+```