nebula/.github/actions/code-sign/action.yml

name: Code-sign Windows binaries
description: >
  Sign every .exe under a given path in place via the DefinedNet code-signer
  Lambda. If `role` or `bucket` is empty, logs a notice and skips signing so
  forks and dev branches without AWS access still produce usable builds.

inputs:
  path:
    description: "Directory whose .exe files should be signed in place"
    required: true
  role:
    description: "IAM role ARN to assume via OIDC; empty disables signing"
    required: false
    default: ""
  bucket:
    description: "S3 staging bucket the code-signer Lambda reads from; empty disables signing"
    required: false
    default: ""
  region:
    description: "AWS region for the role and Lambda"
    required: false
    default: "us-east-2"
  function-name:
    description: "Code-signer Lambda function name"
    required: false
    default: "code-signer"
  key-prefix:
    description: "S3 key prefix the caller is authorized to write under"
    required: false
    default: "code-signing/slackhq/nebula"

runs:
  using: composite
  steps:
    - name: Skip notice
      if: inputs.role == '' || inputs.bucket == ''
      shell: sh
      run: echo "::notice::code-signer role or bucket not set; skipping code signing."

    - name: Configure AWS credentials
      if: inputs.role != '' && inputs.bucket != ''
      uses: aws-actions/configure-aws-credentials@v6
      with:
        role-to-assume: ${{ inputs.role }}
        aws-region: ${{ inputs.region }}
        # Default is 12 retries to ride out IAM trust-policy propagation; once
        # the role is stable we want a real misconfiguration to fail fast.
        retry-max-attempts: 5

    - name: Sign .exe files
      if: inputs.role != '' && inputs.bucket != ''
      shell: sh
      env:
        SIGN_PATH: ${{ inputs.path }}
        BUCKET: ${{ inputs.bucket }}
        FUNCTION_NAME: ${{ inputs.function-name }}
        KEY_PREFIX: ${{ inputs.key-prefix }}
      run: |
        set -eu
        RUN="${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}"

        find "$SIGN_PATH" -name '*.exe' -print | while read -r path
        do
            rel=${path#"$SIGN_PATH"/}
            file=$(basename "$path")
            name=${file%.exe}
            prefix="${KEY_PREFIX}/${RUN}"
            src="${prefix}/unsigned/${rel}"
            dst="${prefix}/signed/${rel}"

            echo "::group::Sign ${rel}"
            echo "Uploading unsigned to s3://${BUCKET}/${src}"
            aws s3 cp --no-progress "$path" "s3://${BUCKET}/${src}" >/dev/null

            echo "Invoking ${FUNCTION_NAME} Lambda"
            payload=$(jq -nc \
                --arg s "$src" \
                --arg d "$dst" \
                --arg p "$name" \
                '{source_key: $s, dest_key: $d, program_name: $p}')
            meta=$(aws lambda invoke \
                --function-name "$FUNCTION_NAME" \
                --cli-binary-format raw-in-base64-out \
                --payload "$payload" \
                --output json \
                /tmp/sign-resp.json)
            if echo "$meta" | jq -e '.FunctionError != null' >/dev/null
            then
                echo "::endgroup::"
                echo "::error::code-signer Lambda failed for ${rel}"
                cat /tmp/sign-resp.json >&2
                exit 1
            fi

            echo "Downloading signed back to ${path}"
            aws s3 cp --no-progress "s3://${BUCKET}/${dst}" "$path" >/dev/null

            aws s3 rm "s3://${BUCKET}/${src}" >/dev/null 2>&1 || true
            aws s3 rm "s3://${BUCKET}/${dst}" >/dev/null 2>&1 || true

            # Sanity-check the bytes we got back actually carry an Authenticode
            # signature that this machine can validate end to end.
            status=$(powershell -NoProfile -Command "(Get-AuthenticodeSignature -FilePath '$path').Status" | tr -d '\r')
            if [ "$status" != "Valid" ]
            then
                echo "::endgroup::"
                echo "::error::${rel} signature status: ${status} (expected Valid)"
                exit 1
            fi

            echo "Signed ${rel} (sha256=$(jq -r '.sha256' /tmp/sign-resp.json), status=${status})"
            echo "::endgroup::"
        done