# Trivy scan (image)

Composite action that runs **`trivy image`** inside **Docker** with the same hardening style as [setup-db](../setup-db): read-only root filesystem, dropped capabilities, `no-new-privileges`, AppArmor `docker-default`, a private `tmpfs` on `/tmp`, and resource limits.

You pass a pullable **`image`** reference (e.g. `alpine:3.20` or a digest). Trivy pulls and scans it inside the container. The Trivy cache from [setup-db](../setup-db) is mounted **read-only** at `/cache` (**`--skip-db-update`** avoids re-downloading the DB). Your **`output-dir`** is mounted **read-write** at `/out`; the report is written as **`output-file`** inside that directory. The report format is always **SARIF** (`--format sarif`). Trivy is always run with **`--offline-scan`** (no API calls to identify dependencies) and **`--exit-code 0`** (the step succeeds after writing the report even when findings are present). Image layers are still pulled over the network when needed.

**Image scans need network access** to pull the image (and possibly layers). This action does **not** set `--network none` (unlike [scan-config](../scan-config) and [scan-fs](../scan-fs)).

## Prerequisites

- Docker on the runner.
- A populated Trivy cache at **`cache-dir`** (typically from the [setup-db](../setup-db) action).

## Usage

```yaml
- name: Setup Trivy DB cache
  id: db
  uses: ./setup-db
- name: Image scan
  id: scan
  uses: ./scan-image
  with:
    image: alpine:3.20
    cache-dir: ${{ steps.db.outputs.cache-dir }}
    output-dir: ${{ github.workspace }}/trivy-reports
    output-file: image.sarif
- name: Upload report
  uses: actions/upload-artifact@v4
  with:
    name: trivy-image
    path: ${{ steps.scan.outputs.output-path }}
```

## Inputs

| Input           | Description                                                                 | Required | Default |
| --------------- | --------------------------------------------------------------------------- | -------- | ------- |
| `image`         | Image reference to scan (pulled inside the container)                       | Yes      | —       |
| `cache-dir`     | Trivy cache directory (mounted read-only at `/cache`)                       | No       | `${{ github.workspace }}/.trivy-cache` |
| `output-dir`    | Host directory for the report (mounted read-write at `/out`)                | Yes      | —       |
| `output-file`   | SARIF file name only (no `/`); created under `output-dir`                   | Yes      | —       |
| `trivy-version` | Trivy Docker image (digest pin recommended)                                 | No       | Same pin as `setup-db` / see `action.yaml` |

**`trivy-version` is optional.** Omit it to use the default image from `action.yaml`.

## Outputs

| Output         | Description                          |
| -------------- | ------------------------------------ |
| `output-path`  | Absolute path to the SARIF report on the host |

## Notes

- Use **`cache-dir`** and **`output-dir`** under **`${{ github.workspace }}`** (or another path the Docker daemon can bind-mount) when the job runs in a container.
- **`output-dir`** and **`cache-dir`** are created with `mkdir -p` if missing.
- Local-only images (e.g. built on the host) are not supported unless they are available to the **inner** Docker pull (this action does not mount `docker.sock`).
- The step still fails if Docker or the container exits non-zero before Trivy completes (e.g. mount or runtime errors).