semg-cust-sast-rule

name	semg-cust-sast-rule
description	Write custom Semgrep SAST rules in YAML to detect application-specific vulnerabilities, enforce coding standards, and integrate into CI/CD pipelines.
domain	cybersecurity
subdomain	devsecops
tags	["semgrep","sast","static-analysis","custom-rules","devsecops","code-security"]
version	1.0
author	mahipal
license	Apache-2.0
nist_csf	["PR.PS-01","GV.SC-07","ID.IM-04","PR.PS-04"]

Implementing Semgrep for Custom SAST Rules

Overview

Semgrep is an open-source static analysis tool that uses pattern-matching to find bugs, enforce code standards, and detect security vulnerabilities. Custom rules are written in YAML using Semgrep's pattern syntax, making it accessible without requiring compiler knowledge. It supports 30+ languages including Python, JavaScript, Go, Java, and C.

When to Use

• When deploying or configuring implementing semgrep for custom sast rules capabilities in your environment
• When establishing security controls aligned to compliance requirements
• When building or improving security architecture for this domain
• When conducting security assessments that require this implementation

Prerequisites

• Python 3.8+ or Docker
• Semgrep CLI installed
• Target codebase in a supported language

Installation

# Install via pip
pip install semgrep

# Install via Homebrew
brew install semgrep

# Run via Docker
docker run -v "${PWD}:/src" returntocorp/semgrep semgrep --config auto /src

# Verify
semgrep --version

Running Semgrep

# Auto-detect rules for your code
semgrep --config auto .

# Use Semgrep registry rules
semgrep --config r/python.lang.security

# Use custom rule file
semgrep --config my-rules.yaml .

# Use multiple configs
semgrep --config auto --config ./custom-rules/ .

# JSON output
semgrep --config auto --json . > results.json

# SARIF output for GitHub
semgrep --config auto --sarif . > results.sarif

# Filter by severity
semgrep --config auto --severity ERROR .

Writing Custom Rules

Basic Pattern Matching

# rules/sql-injection.yaml
rules:
  - id: sql-injection-string-format
    languages: [python]
    severity: 
              
       []
       []