Dockerfile & Container Build Sanity Gate — Catch Root Users, Bloat, Leaked Secrets & Fragile Layers Before You Build
An adversarial reviewer for Dockerfiles and container builds. It flags root users, image bloat, unpinned or cache-busting layers, leaked secrets, and missing hardening, then returns a PASS / FIX / BLOCK verdict — before you build or push the image.
- Reviewing a Dockerfile for root users and leaked secrets before building the image
- Checking a teammate's Dockerfile in a pull request for bloat and fragile layers
- Auditing an oversized or slow-building image for missing hardening before it ships
$13
· or 65 creditsSecure checkout via Stripe
Included in download
- Reviewing a Dockerfile for root users and leaked secrets before building the image
- Checking a teammate's Dockerfile in a pull request for bloat and fragile layers
- file_read automation included
Sample input
Review this Dockerfile: FROM node:latest COPY . . RUN npm install && npm run build ENV API_TOKEN=sk-live-abc123 CMD ["node", "server.js"]
Sample output
VERDICT: BLOCK PRIVILEGE: risk - no USER directive, so the container runs as root. SIZE: bloated - single stage leaves npm and build tools in the final image. LAYERS: fragile - FROM node:latest is unpinned; COPY . . before install busts the cache on every code change. SECRETS: API_TOKEN in ENV is baked into a layer and visible to anyone who pulls the image - highest risk. HARDENING: no .dockerignore, no HEALTHCHECK, packages not minimized. TOP 3 FIXES: remove API_TOKEN from ENV and pass it at runtime; pin the base image and move COPY after dependency install; add a non-root USER plus a multi-stage build.
Dockerfile & Container Build Sanity Gate — Catch Root Users, Bloat, Leaked Secrets & Fragile Layers Before You Build
An adversarial reviewer for Dockerfiles and container builds. It flags root users, image bloat, unpinned or cache-busting layers, leaked secrets, and missing hardening, then returns a PASS / FIX / BLOCK verdict — before you build or push the image.
$13
· or 65 creditsSecure checkout via Stripe
Included in download
- Reviewing a Dockerfile for root users and leaked secrets before building the image
- Checking a teammate's Dockerfile in a pull request for bloat and fragile layers
- file_read automation included
- Instant install
Sample input
Review this Dockerfile: FROM node:latest COPY . . RUN npm install && npm run build ENV API_TOKEN=sk-live-abc123 CMD ["node", "server.js"]
Sample output
VERDICT: BLOCK PRIVILEGE: risk - no USER directive, so the container runs as root. SIZE: bloated - single stage leaves npm and build tools in the final image. LAYERS: fragile - FROM node:latest is unpinned; COPY . . before install busts the cache on every code change. SECRETS: API_TOKEN in ENV is baked into a layer and visible to anyone who pulls the image - highest risk. HARDENING: no .dockerignore, no HEALTHCHECK, packages not minimized. TOP 3 FIXES: remove API_TOKEN from ENV and pass it at runtime; pin the base image and move COPY after dependency install; add a non-root USER plus a multi-stage build.
About This Skill
The Dockerfile & Container Build Sanity Gate is an adversarial reviewer for Dockerfiles and container build files. You paste a Dockerfile and it reads it the way a security-minded platform engineer would in code review — then returns a structured verdict. It does not rewrite your Dockerfile or generate one. It runs five passes — privilege and user, image size and bloat, layer order and pinning, secret and data leakage, and hardening best practices — and returns a structured PASS / FIX / BLOCK verdict with the highest-impact fixes first. It is built to be the last read before an image is built or pushed, when the author is too close to the file to spot a root process, a baked-in token, or a cache-busting layer.
Use Cases
- Reviewing a Dockerfile for root users and leaked secrets before building the image
- Checking a teammate's Dockerfile in a pull request for bloat and fragile layers
- Auditing an oversized or slow-building image for missing hardening before it ships
Known Limitations
It reasons over the text of the Dockerfile you provide, so it cannot inspect the actual built image, scan installed packages for CVEs, or detect issues that only appear at runtime. It is not a replacement for dedicated image scanners, signing tools, or a full security audit. Its flags are heuristics based on common container pitfalls, not guarantees. It does not rewrite or build your Dockerfile, and it only sees the files you paste.
How to Install
mkdir -p ~/.claude/skills && curl -sL https://www.agensi.io/api/install/dockerfile-container-build-sanity-gate-catch-root-users-bloat-leaked-secrets-fragile-layers-before-you-build -o /tmp/dockerfile-container-build-sanity-gate-catch-root-users-bloat-leaked-secrets-fragile-layers-before-you-build.zip && unzip -o /tmp/dockerfile-container-build-sanity-gate-catch-root-users-bloat-leaked-secrets-fragile-layers-before-you-build.zip -d ~/.claude/skills && rm /tmp/dockerfile-container-build-sanity-gate-catch-root-users-bloat-leaked-secrets-fragile-layers-before-you-build.zipFree skills install directly. Paid skills require purchase - use the download button above after buying.
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Security Scanned
Passed automated security review
Permissions
File Scopes
Read-only is all this skill needs. It reads the Dockerfile (and any .dockerignore or compose snippet) you provide and reasons over it to produce a verdict. It does not write files, build or run images, edit your Dockerfile, make network or cloud calls, or run any commands. Nothing leaves your machine.
Model-agnostic and works with any assistant that can read a file or pasted text. Pure reasoning over the Dockerfile you provide — it requests read-only access and has no network or write access, so nothing is sent anywhere and no build is run. Paste a single Dockerfile or include a .dockerignore or compose snippet and it returns a structured verdict. It reviews the build; it does not modify or run it.
Creator
PubsProToolkit builds AI agent skills that bring regulated-industry rigor to written output. Created by a CMPP-certified medical writer with a PhD and 10+ years in pharma — covering clinical and scientific publishing, plus evidence-grounded QC for any agent.
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