dcg

# DCG — Destructive Command Guard A high-performance Claude Code hook that intercepts and blocks destructive commands before they execute. Written in Rust with SIMD-accelerated filtering for sub-millisecond latency. ## Why This Exists AI coding agents are powerful but fallible. They can accidentally run destructive commands: - **"Let me clean up the build artifacts"** → `rm -rf ./src` (typo) - **"I'll reset to the last commit"** → `git reset --hard` (destroys uncommitted changes) - **"Let me fix the merge conflict"** → `git checkout -- .` (discards all modifications) - **"I'll clean up untracked files"** → `git clean -fd` (permanently deletes untracked files) DCG intercepts dangerous commands *before* execution and blocks them with a clear explanation, giving you a chance to stash your changes first. ## Critical Design Principles ### 1. Whitelist-First Architecture Safe patterns are checked *before* destructive patterns. This ensures explicitly safe commands are never accidentally blocked: ``` git checkout -b feature → Matches SAFE "checkout-new-branch" → ALLOW git checkout -- file.txt → No safe match, matches DESTRUCTIVE → DENY ``` ### 2. Fail-Safe Defaults (Default-Allow) Unrecognized commands are **allowed by default**. This ensures: - The hook never breaks legitimate workflows - Only *known* dangerous patterns are blocked - New git commands work until explicitly categorized ### 3. Zero False Negatives Philosophy The pattern set prioritizes **never allowing dangerous commands** over avoiding false positives. A few extra prompts for manual confirmation are acceptable; lost work is not. ## What It Blocks ### Git Commands That Destroy Uncommitted Work | Command | Reason | |---------|--------| | `git reset --hard` | Destroys uncommitted changes | | `git reset --merge` | Destroys uncommitted changes | | `git checkout -- <file>` | Discards file modifications | | `git restore <file>` (without `--staged`) | Discards uncommitted changes | | `git clean -f` | Permanently deletes untracked files | ### Git Commands That Destroy Remote History | Command | Reason | |---------|--------| | `git push --force` / `-f` | Overwrites remote commits | | `git branch -d`, `--delete`, `-D`, `-f`, `-M`, `-C` | Deletes or force-overwrites a user-owned branch ref | ### Git Commands That Destroy Stashed Work | Command | Reason | |---------|--------| | `git stash drop` | Permanently deletes a stash | | `git stash clear` | Permanently deletes all stashes | ### Filesystem Commands | Command | Reason | |---------|--------| | `rm -rf` (outside `/tmp`, `/var/tmp`, `$TMPDIR`) | Recursive deletion is dangerous | ## What It ALLOWS Safe operations pass through silently: ### Always Safe Git Operations `git status`, `git log`, `git diff`, `git add`, `git commit`, `git push`, `git pull`, `git fetch`, read-only branch listings, `git stash`, `git stash pop`, `git stash list` ### Explicitly Safe Patterns | Pattern | Why Safe | |---------|----------| | `git checkout -b <branch>` | Creating new branches | | `git checkout --orphan <branch>` | Creating orphan branches | | `git restore --staged <file>` | Unstaging only, doesn't touch working tree | | `git restore -S <file>` | Short flag for staged | | `git clean -n` / `--dry-run` | Preview mode, no actual deletion | | `rm -rf /tmp/*` | Temp directories are ephemeral | | `rm -rf $TMPDIR/*` | Shell variable forms | ### Safe Alternative: `--force-with-lease` ```bash git push --force-with-lease # ALLOWED - refuses if remote has unseen commits git push --force # BLOCKED - can overwrite others' work ``` ## Modular Pack System DCG uses a modular "pack" system to organize patterns by category: ### Core Packs (Always Enabled) | Pack | Description | |------|-------------| | `core.git` | Destructive git commands | | `core.filesystem` | Dangerous rm -rf outside temp | ### Database Packs | Pack | Description | |------|-------------| | `database.postgresql` | DROP/TRUNCATE in PostgreSQL | | `database.mysql` | DROP/TRUNCATE in MySQL/MariaDB | | `database.mongodb` | dropDatabase, drop() | | `database.redis` | FLUSHALL/FLUSHDB | | `database.sqlite` | DROP in SQLite | ### Container Packs | Pack | Description | |------|-------------| | `containers.docker` | docker system prune, docker rm -f | | `containers.compose` | docker-compose down --volumes | | `containers.podman` | podman system prune | ### Kubernetes Packs | Pack | Description | |------|-------------| | `kubernetes.kubectl` | kubectl delete namespace | | `kubernetes.helm` | helm uninstall | | `kubernetes.kustomize` | kustomize delete patterns | ### Cloud Provider Packs | Pack | Description | |------|-------------| | `cloud.aws` | Destructive AWS CLI commands | | `cloud.gcp` | Destructive gcloud commands | | `cloud.azure` | Destructive az commands | ### Infrastructure Packs | Pack | Description | |------|-------------| | `infrastructure.terraform` | terraform destroy | | `infrastructure.ansible` | Dangerous ansible patterns | | `infrastructure.pulumi` | pulumi destroy | ### System Packs | Pack | Description | |------|-------------| | `system.disk` | dd, mkfs, fdisk operations | | `system.permissions` | Dangerous chmod/chown patterns | | `system.services` | systemctl stop/disable patterns | ### Other Packs | Pack | Description | |------|-------------| | `strict_git` | Extra paranoid git protections | | `package_managers` | npm unpublish, cargo yank | ### Configuring Packs ```toml # ~/.config/dcg/config.toml [packs] enabled = [ "database.postgresql", "containers.docker", "kubernetes", # Enables all kubernetes sub-packs ] ``` ## Environment Variables | Variable | Description | |----------|-------------| | `DCG_PACKS="containers.docker,kubernetes"` | Enable packs (comma-separated) | | `DCG_DISABLE="kubernetes.helm"` | Disable packs/sub-packs | | `DCG_VERBOSE=1` | Verbose output | | `DCG_COLOR=auto\|always\|never` | Color mode | | `DCG_BYPASS=1` | Bypass DCG entirely (escape hatch) | ## Installation ### Quick Install (Verified Release) Install `minisign` through your trusted OS package manager first (for example, `apt install minisign` or `brew install minisign`). Then paste this function into **Bash**. It authenticates the release installer with the project's pinned Minisign key and checks its fixed SHA-256 identity before executing any downloaded code. The key is the trust root; establish it from a trusted copy of this documentation or an independent maintainer channel, not from the same download as the installer. A downloaded checksum alone does not authenticate a publisher. <!-- verified-release-install:begin --> ```bash dcg_install() ( # Explicit failure guards also work when called inside `if dcg_install ...`. set -eu umask 077 if [ "$#" -gt 1 ]; then printf '%s\n' 'Usage: dcg_install [--easy-mode|--system]' >&2 exit 1 fi case "${1:-}" in ''|--easy-mode|--system) ;; *) printf '%s\n' 'Usage: dcg_install [--easy-mode|--system]' >&2; exit 1 ;; esac readonly dcg_tag='v0.16.0' readonly dcg_sha256='072462974ad790008e8a3aadb1a9eecf2d9b6bd0ef7b469f69f0fb0fa3b51c7c' readonly dcg_key='RWSoYi6NXJWzaRs1mJmOwwXrZfPWcq6MXnQlNMLBYKzlIQTLwuVQG6uO' dcg_minisign=$(type -P minisign) || { printf '%s\n' 'Install minisign with your trusted OS package manager first.' >&2 exit 1 } dcg_curl=$(type -P curl) || exit 1 dcg_bash=$(type -P bash) || exit 1 if dcg_hash=$(type -P sha256sum); then dcg_hash_kind=sha256sum elif dcg_hash=$(type -P shasum); then dcg_hash_kind=shasum else printf '%s\n' 'A SHA-256 verifier (sha256sum or shasum) is required.' >&2 exit 1 fi dcg_tmp=$(mktemp -d "${TMPDIR:-/tmp}/dcg-install.XXXXXXXXXX") || exit 1 printf 'Installer verification files: %s\n' "$dcg_tmp" dcg_base="https://github.com/Dicklesworthstone/destructive_command_guard/releases/download/$dcg_tag" for dcg_asset in install.sh install.sh.minisig; do "$dcg_curl" --proto '=https' --proto-redir '=https' --tlsv1.2 -fsSL \ --max-time 120 --user-agent 'destructive_command_guard-installer' \ "$dcg_base/$dcg_asset" -o "$dcg_tmp/$dcg_asset" || exit 1 done "$dcg_minisign" -Vm "$dcg_tmp/install.sh" \ -x "$dcg_tmp/install.sh.minisig" -P "$dcg_key" || exit 1 if [ "$dcg_hash_kind" = sha256sum ]; then dcg_actual=$("$dcg_hash" "$dcg_tmp/install.sh") || exit 1 else dcg_actual=$("$dcg_hash" -a 256 "$dcg_tmp/install.sh") || exit 1 fi if [ "${dcg_actual%% *}" != "$dcg_sha256" ]; then printf '%s\n' 'Installer does not match the pinned release; refusing execution.' >&2 exit 1 fi case "${1:-}" in --system) # The first elevated command runs only after BOTH checks succeed. sudo -- "$dcg_bash" "$dcg_tmp/install.sh" \ --version "$dcg_tag" --require-minisign --system ;; --easy-mode) "$dcg_bash" "$dcg_tmp/install.sh" \ --version "$dcg_tag" --require-minisign --easy-mode ;; *) "$dcg_bash" "$dcg_tmp/install.sh" \ --version "$dcg_tag" --require-minisign ;; esac ) ``` <!-- verified-release-install:end --> Choose **one** installation mode after defining the function: ```bash dcg_install # Normal: install to ~/.local/bin dcg_install --easy-mode # Also configure PATH automatically dcg_install --system # Install to /usr/local/bin using sudo after verification ``` For system-wide installation, install `minisign` on the system PATH so the elevated installer can also verify the binary archive. Missing tools, missing assets, invalid signatures, or a different installer digest stop installation; there is no unsigned or source-build fallback. The private download directory is retained for inspection. The tag and digest are a pair: upgrading this recipe requires independently verifying and pinning the new release's installer bytes. Do not replace the tag with `main` or `latest` or remove either verification. For native Windows, follow the [verified PowerShell workflow](docs/windows.md#verified-release-installation). ### From Source (Requires Rust Nightly) For development, build from a trusted, reviewed local checkout. This uses the checkout's pinned toolchain and lockfile; it is a separate source-trust decision, not a fallback when release authentication fails. ```bash cargo install --path . --locked ``` ### Prebuilt Binaries Available for: Linux x86_64, Linux ARM64, macOS Intel, macOS Apple Silicon, Windows ## Claude Code Configuration Add to `~/.claude/settings.json`: ```json { "hooks": { "PreToolUse": [ { "matcher": "Bash|PowerShell|Monitor", "hooks": [ { "type": "command", "command": "/absolute/path/to/dcg" } ] } ] } } ```