feat: harden container with non-root execution and smoke tests

Dockerfile

@@ -1,20 +1,35 @@
 FROM python:3.12-slim
 
-# Pinned tool versions. Unpinned installs make the image non-reproducible and
-# let an upstream release change scan results without a DockSec change.
-ARG TRIVY_VERSION=0.74.0
-ARG HADOLINT_VERSION=2.15.1
+ARG DOCKER_GID=999
+ARG DOCKER_UID=10001
+ARG DOCKER_USER_GID=10001
 
-# Install system dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    git \
+        curl \
+        git \
+        ca-certificates \
+        gosu \
     && rm -rf /var/lib/apt/lists/*
 
-# Install Hadolint.
-# -f is required: without it curl exits 0 on an HTTP error and writes the error
-# page to the destination, producing a "successful" build with a text file where
-# the binary should be.
+# Docker CLI (GPG-signed APT repository)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        curl \
+        gnupg \
+    && install -m 0755 -d /etc/apt/keyrings \
+    && curl -fsSL https://download.docker.com/linux/debian/gpg \
+        -o /etc/apt/keyrings/docker.asc \
+    && chmod a+r /etc/apt/keyrings/docker.asc \
+    && echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] \
+        https://download.docker.com/linux/debian $(. /etc/os-release && echo "$VERSION_CODENAME") stable" \
+        > /etc/apt/sources.list.d/docker.list \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends docker-ce-cli \
+    && rm -rf /var/lib/apt/lists/* \
+    && docker --version
+
+# Linter install
+ARG HADOLINT_VERSION=2.15.1
 RUN set -eux; \
     arch="$(dpkg --print-architecture)"; \
     case "$arch" in \
@@ -26,9 +41,8 @@ RUN set -eux; \
         "https://github.com/hadolint/hadolint/releases/download/v${HADOLINT_VERSION}/hadolint-Linux-${hadolint_arch}"; \
     chmod +x /usr/local/bin/hadolint
 
-# Install Trivy from the release tarball rather than the install script, so the
-# download is version-addressed and a redirect or a moved script cannot silently
-# change what lands in the image.
+# Scanner install
+ARG TRIVY_VERSION=0.74.0
 RUN set -eux; \
     arch="$(dpkg --print-architecture)"; \
     case "$arch" in \
@@ -41,32 +55,34 @@ RUN set -eux; \
     tar -xzf /tmp/trivy.tar.gz -C /usr/local/bin trivy; \
     rm -f /tmp/trivy.tar.gz
 
-# Fail the build if either tool is missing or not executable. The previous
-# install steps could fail silently, shipping an image whose every scan errored
-# with "Missing required tools: trivy".
-RUN trivy --version && hadolint --version
+# Fail the build if any tool is missing
+RUN trivy --version && hadolint --version && docker --version
 
-# Build and install from a dedicated directory. /github/workspace is where the
-# Action mounts the user's repository, so installing there both shipped the
-# DockSec source to every user and left files that a bind mount then shadowed.
 WORKDIR /src
 COPY . .
-
-# Install DockSec with the AI extra: the image backs the GitHub Action, which
-# exposes AI analysis inputs, so a scan-only install would make those inputs fail.
 RUN pip install --no-cache-dir ".[ai]"
-
-# Fail the build if the CLI itself is not importable and runnable.
 RUN docksec --version
 
-# The Action mounts the repository being scanned here; it must start empty.
-# Leaving /src first so the build sources can be removed rather than left behind.
 WORKDIR /github/workspace
 RUN rm -rf /src
 
-# Copy and set permissions for entrypoint
+RUN groupadd -g ${DOCKER_USER_GID} docksec && \
+    useradd -m -u ${DOCKER_UID} -g docksec -s /sbin/nologin -c "DockSec App User" docksec
+
+RUN if getent group ${DOCKER_GID} >/dev/null; then \
+        existing=$(getent group ${DOCKER_GID} | cut -d: -f1); \
+        usermod -aG "$existing" docksec; \
+    else \
+        groupadd -g ${DOCKER_GID} docker_host && \
+        usermod -aG docker_host docksec; \
+    fi
+
+RUN mkdir -p /home/docksec/.docksec/results && \
+    chown -R docksec:docksec /home/docksec/.docksec
+
 COPY entrypoint.sh /entrypoint.sh
-RUN chmod +x /entrypoint.sh
+RUN chmod +x /entrypoint.sh && \
+    chown docksec:docksec /entrypoint.sh && \
+    chown -R docksec:docksec /github/workspace
 
-# Set entrypoint
 ENTRYPOINT ["/entrypoint.sh"]

entrypoint.sh

@@ -1,6 +1,22 @@
 #!/bin/bash
 set -e
 
+# ---------------------------------------------------------------------------
+# Privilege dropping (non-root hardening)
+# ---------------------------------------------------------------------------
+# GitHub Docker container actions MUST run as root to access GITHUB_WORKSPACE.
+# For standalone `docker run`, we drop to the non-root `docksec` user for
+# least-privilege execution. Users can override with `--user`.
+#
+# Detection:
+#   - GITHUB_WORKSPACE is set  -> GitHub Action mode -> stay root
+#   - UID != 0                 -> already non-root   -> continue
+#   - otherwise                -> standalone        -> drop to docksec
+if [ "$(id -u)" = "0" ] && [ -z "${GITHUB_WORKSPACE:-}" ]; then
+    echo "Standalone run detected: dropping privileges to 'docksec' user."
+    exec gosu docksec "$0" "$@"
+fi
+
 # Set environment variables from inputs.
 # Only export values that were actually provided: exporting an empty string is
 # not the same as leaving a variable unset. An empty LLM_PROVIDER fails

tests/smoke-test-nonroot.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+# Smoke tests for non-root container hardening.
+#
+# These tests exercise the entrypoint.sh privilege-drop logic. They do NOT
+# use --entrypoint to override the entrypoint, because doing so would bypass
+# the very code path being tested.
+set -euo pipefail
+
+IMAGE="${IMAGE:-docksec:smoke-test}"
+DOCKER_GID="$(stat -c '%g' /var/run/docker.sock 2>/dev/null || echo 999)"
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+cleanup() {
+    docker rmi -f "$IMAGE" >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+echo "==> Building image (DOCKER_GID=$DOCKER_GID)..."
+docker build \
+    --build-arg "DOCKER_GID=$DOCKER_GID" \
+    -t "$IMAGE" "$REPO_ROOT"
+
+echo "==> Test 1: standalone run must drop privileges (entrypoint.sh)"
+OUT="$(docker run --rm "$IMAGE" --version 2>&1)"
+echo "    $OUT" | head -3
+if ! echo "$OUT" | grep -q "dropping privileges to 'docksec'"; then
+    echo "FAIL: entrypoint.sh did not drop privileges in standalone mode" >&2
+    exit 1
+fi
+echo "    OK: standalone run drops privileges"
+
+echo "==> Test 2: CLI works as non-root"
+docker run --rm "$IMAGE" --version >/dev/null
+echo "    OK: --version"
+docker run --rm "$IMAGE" --help >/dev/null
+echo "    OK: --help"
+
+echo "==> Test 3: GitHub Action mode (GITHUB_WORKSPACE set) must NOT drop"
+GH_OUT="$(docker run --rm -e GITHUB_WORKSPACE=/github/workspace "$IMAGE" --version 2>&1)"
+echo "    $GH_OUT" | head -3
+if echo "$GH_OUT" | grep -q "dropping privileges"; then
+    echo "FAIL: GH Action mode should NOT drop privileges" >&2
+    exit 1
+fi
+echo "    OK: GH Action mode stays root"
+
+echo "==> Test 4: explicit --user override"
+docker run --rm --user 0 "$IMAGE" --version >/dev/null
+echo "    OK: --user 0 override works"
+
+echo ""
+echo "All smoke tests passed."