Performing Container Image Hardening

# Build stage with all dependencies
FROM python:3.12-bookworm AS builder
WORKDIR /build
COPY requirements.txt .
RUN pip install --no-cache-dir --prefix=/install -r requirements.txt
COPY src/ ./src/
RUN python -m compileall src/

# Production stage with minimal base
FROM python:3.12-slim-bookworm AS production
RUN apt-get update && \
    apt-get install -y --no-install-recommends libpq5 && \
    rm -rf /var/lib/apt/lists/* && \
    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false

COPY --from=builder /install /usr/local
COPY --from=builder /build/src /app/src

RUN groupadd -r appuser && useradd -r -g appuser -d /app -s /sbin/nologin appuser
RUN chown -R appuser:appuser /app

USER appuser
WORKDIR /app

HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8080/health')" || exit 1

EXPOSE 8080
ENTRYPOINT ["python", "-m", "src.main"]

Step 2: Use Distroless Base Images

# Go application with distroless
FROM golang:1.22 AS builder
WORKDIR /app
COPY go.* ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /server .

FROM gcr.io/distroless/static-debian12:nonroot
COPY --from=builder /server /server
USER nonroot:nonroot
ENTRYPOINT ["/server"]

Step 3: Remove Unnecessary Components

# Hardened image checklist
FROM ubuntu:24.04 AS base

RUN apt-get update && \
    apt-get install -y --no-install-recommends \
      ca-certificates \
      libssl3 && \
    # Remove package manager to prevent runtime package installation
    apt-get purge -y --auto-remove apt dpkg && \
    rm -rf /var/lib/apt/lists/* \
           /var/cache/apt/* \
           /tmp/* \
           /var/tmp/* \
           /usr/share/doc/* \
           /usr/share/man/* \
           /usr/share/info/* \
           /root/.cache

# Remove shells if not needed
RUN rm -f /bin/sh /bin/bash /usr/bin/sh 2>/dev/null || true

# Remove setuid/setgid binaries
RUN find / -perm /6000 -type f -exec chmod a-s {} + 2>/dev/null || true

Step 4: Configure Read-Only Filesystem

# Kubernetes deployment with read-only root filesystem
apiVersion: apps/v1