Dockerfile.mcp

# =============================================================================
# CyberChef MCP Server - Hardened Docker Image
# =============================================================================
# Security Features:
# - Distroless Chainguard base image (zero CVEs, minimal attack surface)
# - Multi-stage build (dev for building, distroless for runtime)
# - Non-root user execution (UID 65532 'nonroot')
# - Read-only filesystem compatible
# - No shell, package manager, or unnecessary tools in runtime
# - Wolfi-based OS with daily security updates
# - SLSA Build Level 3 provenance
#
# Base Image: Chainguard Node.js (cgr.dev/chainguard/node)
# - Zero known CVEs (as of build time)
# - 70% smaller layer data vs traditional images
# - 7-day SLA for critical CVE patches
# - FIPS-validated cryptography available
#
# Alternative: Docker Hardened Images (DHI) for Node.js 22 are available via
# Docker Hub subscription for enterprise deployments requiring Docker-native
# hardening. See: https://docs.docker.com/dhi/about/what/
#
# References:
# - Chainguard Images: https://edu.chainguard.dev/chainguard/chainguard-images/
# - Node.js Migration: https://edu.chainguard.dev/chainguard/migration/migrating-node/
# =============================================================================

# -----------------------------------------------------------------------------
# Stage 1: Build Stage (using -dev variant with shell and build tools)
# -----------------------------------------------------------------------------
FROM cgr.dev/chainguard/node:latest-dev AS builder

# Run as root for build operations (Chainguard -dev includes root user)
USER root

WORKDIR /app

# Copy package files first for better layer caching
COPY package.json package-lock.json ./

# Install dependencies without running postinstall (which needs Gruntfile)
# Using --ignore-scripts to prevent arbitrary code execution during install
RUN npm ci --ignore-scripts

# Copy all source files
COPY . .

# Apply patches for Node 22 compatibility (SlowBuffer deprecation)
# These packages use the deprecated SlowBuffer which was removed/changed in newer Node versions
RUN sed -i 's/new SlowBuffer/Buffer.alloc/g' node_modules/avsc/lib/types.js && \
    sed -i 's/SlowBuffer/Buffer/g' node_modules/buffer-equal-constant-time/index.js

# Run postinstall scripts (fixes imports etc. defined in package.json)
RUN npm run postinstall

# Generate CyberChef configuration and Node index
RUN npx grunt configTests

# Remove unnecessary files to reduce final image size and eliminate dev-time vulnerabilities
RUN rm -rf \
    .git \
    .github \
    tests \
    docs \
    *.md \
    Gruntfile.js \
    babel.config.js \
    eslint.config.mjs \
    nightwatch.conf.cjs \
    webpack.config.js \
    .eslintrc.json \
    .babelrc \
    node_modules/@esbuild \
    node_modules/esbuild \
    node_modules/webpack \
    node_modules/babel-loader \
    node_modules/grunt* \
    node_modules/nightwatch \
    node_modules/selenium-webdriver \
    node_modules/eslint* 2>/dev/null || true

# -----------------------------------------------------------------------------
# Stage 2: Runtime Stage (distroless, minimal attack surface)
# -----------------------------------------------------------------------------
FROM cgr.dev/chainguard/node:latest

# Security: Add metadata labels
LABEL org.opencontainers.image.title="CyberChef MCP Server" \
      org.opencontainers.image.description="MCP server exposing 300+ CyberChef operations as AI tools" \
      org.opencontainers.image.vendor="DoubleGate" \
      org.opencontainers.image.licenses="Apache-2.0" \
      org.opencontainers.image.source="https://github.com/doublegate/CyberChef-MCP" \
      org.opencontainers.image.documentation="https://github.com/doublegate/CyberChef-MCP/blob/master/docs/user_guide.md"

WORKDIR /app

# Copy built application from builder stage
# Chainguard's nonroot user (UID 65532) owns the files
COPY --from=builder --chown=65532:65532 /app /app

# Security: Set TMPDIR to use /tmp (writable via tmpfs in read-only mode)
ENV TMPDIR=/tmp

# Health check for container orchestration
# Note: MCP servers use stdio, so we check if node is responsive
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
    CMD node -e "process.exit(0)" || exit 1

# =============================================================================
# Read-Only Filesystem Usage (Security Hardening)
# =============================================================================
# This image is compatible with Docker's read-only filesystem mode for enhanced
# security. To run with a read-only root filesystem:
#
#   docker run -i --rm --read-only \
#     --tmpfs /tmp:rw,noexec,nosuid,size=100m \
#     ghcr.io/doublegate/cyberchef-mcp_v1:latest
#
# The tmpfs mount provides writable space for:
# - Temporary files from compression operations (Gzip, Bzip2, etc.)
# - Node.js runtime temporary files
# - Operation intermediate results
#
# tmpfs flags:
# - rw: Read-write (required for temp files)
# - noexec: Prevent execution of files in /tmp (security)
# - nosuid: Ignore setuid/setgid bits (security)
# - size=100m: Limit tmpfs to 100MB (adjust based on operation needs)
#
# Benefits of read-only mode:
# - Prevents container compromise from modifying system files
# - Ensures container immutability
# - Meets compliance requirements (PCI-DSS, SOC 2, FedRAMP)
# - Reduces attack surface for container escape vulnerabilities
# =============================================================================

# Run the MCP server
# Note: Chainguard distroless has "node" as ENTRYPOINT, so CMD is just the script path
CMD ["src/node/mcp-server.mjs"]