CodeFence

Check AI-written code before you commit it.

Offline. Zero dependencies. No account. No telemetry.

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What it does

CodeFence is a single-file, zero-dependency Python CLI that scans source code for selected dangerous patterns before you commit. It runs a curated set of rules and reports findings with:

• severity (critical / high / medium / low / info)
• exact location (file:line:column)
• code snippet
• short remediation
• typical before/after fix example

It is designed around the risks commonly encountered in AI-assisted development, but scans ordinary source code regardless of how it was written.

The gate workflow:

AI writes code
     |
     v
CodeFence runs on staged files
     |
     v
policy evaluation (allow / warn / block)
     |
     v
PASS or BLOCKED
     |
     v
git commit

What it does NOT do

• Not an autofixer. It shows a typical fix; it does not edit files.
• Not a security audit. It is a pattern-based sanity checker.
• Not a replacement for Semgrep, CodeQL, or professional review.
• Not interprocedural. No dataflow, no taint analysis.
• Not a guarantee. A clean scan does not mean the code is secure.

For per-rule samples, known false-positive scenarios, false-negative scenarios, and the full detection methodology, see docs/DETECTION_METHODOLOGY.md.

Install

pip install codefence

Or run it directly:

python3 codefence.py app.py

Quick start

One-time setup in a git repository:

codefence init

This installs a pre-commit hook and creates .codefence/config.json. Every commit is then gated automatically.

Daily usage:

codefence --staged          # scan only what is staged
codefence --staged --diff   # only NEW findings since baseline
codefence baseline          # snapshot current findings

One-off scans:

codefence src/
codefence --format json --output report.json src/
codefence --format html --output report.html src/
codefence --format sarif --output results.sarif .

Policy-as-code:

codefence --policy company-policy.json --staged
codefence policy validate company-policy.json

Explanation:

codefence explain R002

The 30 rules

Rules are shipped in rules.json (human-readable JSON). You can inspect them, and you can add or disable rules for your own use.

Secrets

• R001 - Hardcoded API keys / secrets
• R011 - Hardcoded database credentials
• R028 - Env var with hardcoded fallback secret

Injection

• R002 - SQL injection via string concatenation (Python)
• R003 - eval() / exec() on untrusted input (Python)
• R004 - Command injection via shell=True (Python)
• R005 - innerHTML with unsanitized data (JavaScript)
• R010 - Path traversal
• R014 - Prototype pollution (JavaScript)
• R019 - Unsafe deserialization (pickle, yaml.load)

Authentication

• R006 - Missing authentication on endpoints
• R015 - Missing rate limiting on public endpoints
• R018 - Open redirect
• R020 - Never-expiring tokens / JWT

Cryptography

• R008 - Insecure random for security tokens (Python)
• R009 - Disabled TLS/SSL verification
• R016 - MD5 / SHA1 for password hashing

Configuration

• R007 - Overly permissive CORS (*)
• R017 - Debug mode left enabled
• R021 - Missing security headers (Express)

Reliability

• R022 - Race conditions (check-then-act)
• R026 - HTTP request without timeout
• R027 - Naive datetime (no timezone, context-aware)

Quality

• R012 - Broad except: pass
• R013 - Mutable default arguments
• R023 - Logging sensitive data
• R024 - Unused imports / dead code
• R025 - Promise rejection ignored (JavaScript)

AI-specific

• R030 - Typosquatted package imports
• R031 - TODO / FIXME / HACK in new code

Each rule carries a confidence level and a stable rule_version + fingerprint for baseline stability.

Configuration

Options can be passed as CLI flags or through a JSON config file (auto-discovered at .codefence/config.json after 'codefence init').

Example .codefence/config.json:

{
  "schema": "codefence/config-v1",
  "format": "json",
  "severity": "medium",
  "include": ["*.py", "*.js"],
  "exclude": ["node_modules", ".git", "venv", "samples"],
  "max_size": 2097152,
  "cache": false
}

Priority: CLI flags > config file > built-in defaults.

Optional cache

Pass --cache to enable a local cache at ~/.cache/codefence/. The cache is keyed by SHA-256 of the file content plus a fingerprint of rules.json. It is off by default. See SECURITY.md for how the cache is protected.

Optional history

Pass --history to record this scan in a local SQLite database at ~/.local/share/codefence/history.db. Off by default.

Set CODEFENCE_NO_HISTORY=1 to disable history entirely, even when --history is set.

Query history:

codefence history
codefence stats

Security and privacy

• Zero network calls. Zero.
• Zero telemetry.
• Zero data upload.
• Writes only to --output, and optionally to: ~/.cache/codefence/ (only when --cache is set) ~/.local/share/codefence/ (only when --history is set)
• Never writes to the files you scan.
• Never executes the code you scan.

The full threat model is documented in SECURITY.md.

Verifying the download

Every shipped file is hashed in CHECKSUMS.txt. To verify:

sha256sum codefence.py rules.json

Compare the output with the corresponding lines in CHECKSUMS.txt. If the hashes do not match, do not use the file.

Free vs Pro

Free gives you the full scanner. Pro gives you the workflow.

You are not paying for more detection. The Free tier includes all 30 rules. You are paying for the automation layer that turns findings into a gate.

Feature	Free	Pro ($19)
All 30 rules (Python + JavaScript)	Yes	Yes
CLI output (colored, compact, verbose)	Yes	Yes
JSON output	Yes	Yes
Configuration, include/exclude, severity filters	Yes	Yes
Offline, zero dependencies, zero network	Yes	Yes
--format sarif	-	Yes
--format html	-	Yes
Git pre-commit hook (init-hook)	-	Yes
--staged / --diff	-	Yes
baseline	-	Yes
--policy + policy validate	-	Yes
--evidence (deterministic hashes)	-	Yes
--history + history / stats	-	Yes
explain RXXX	-	Yes
init-github (GitHub Actions workflow)	-	Yes
init (one-command setup)	-	Yes

Free = detect. Pro = enforce.

Activating Pro

After purchase you receive a license key of the form identifier:signature. Store it in one of two places.

Option 1 — File:

mkdir -p ~/.codefence
echo 'YOUR-LICENSE-KEY' > ~/.codefence/license.key

Option 2 — Environment variable (recommended for CI):

export CODEFENCE_LICENSE_KEY='YOUR-LICENSE-KEY'

Verify activation:

cfence init-hook    # works only with a valid Pro license

The license is verified locally with HMAC-SHA256. No network call, no telemetry, no activation server.

Payment and pricing

$19 USD, one-time.

Includes the current major version (v1.x) and its maintenance releases. No subscription. No support. No account.

Payments are available in cryptocurrency only:

• USDT (TRC20 or BEP20)
• BTC
• SOL
• TRX
• XRP

Official purchase channels:

• Getly
• SilkRoadx402
• ctlx.cc

If you find CodeFence on any other site claiming to sell it, treat that site as unofficial.

License

Source-available. Not open source.

Summary:

• Personal use on up to 3 devices that you own or control.
• Read, study, and privately modify the source.
• No redistribution. No resale. No bundling.
• No scanning-as-a-service on a commercial basis.

For plain-language answers to common questions, see LICENSE_FAQ.md. For the full legal terms, see LICENSE.txt and TERMS_OF_USE.md.

Governing law: England and Wales. Mandatory consumer protections in your country of residence remain fully applicable.

Support

There is no support.

• No email. No chat. No issue tracker.
• No guaranteed updates.
• No bug-fix commitments.

If you need a product with ongoing support, please look elsewhere.

FAQ

Q: Will this find every security issue in my code? A: No. It finds a curated set of dangerous patterns. It is a sanity check, not a security audit.

Q: Can I use it in CI? A: Yes. JSON and SARIF outputs are pure on stdout. Exit codes are stable.

Q: Does it phone home? A: No. Zero network calls. You can verify by reading the source or by running it under strace.

Q: Does it fix my code? A: No. It shows a typical before/after fix. You apply it yourself.

Q: Does it support TypeScript? A: No. Python, JavaScript (.js, .mjs, .cjs).

Q: What about false positives? A: Pattern-based scanners always produce some. Rules with lower confidence are flagged as such. You can disable any rule in rules.json or via policy overrides.

Q: Can I modify the source? A: Yes, privately. See LICENSE_FAQ.md.

Q: Can my team use it? A: Each developer using CodeFence on their own machine needs their own license. One license covers one individual on up to three devices.

Q: How do I get updates? A: There are no guaranteed updates.

Q: Can I get a refund? A: See REFUND_POLICY.md.

A note on honesty

This product is built to do a specific, limited thing well. It does not overstate what it can do. Every claim in this README is traceable to a line of code or a test. If you find a claim that is not supported by what the tool actually does, please report it.

End of README.