---
name: Codeql
description: Run CodeQL static analysis for security vulnerability detection, taint tracking, and data flow analysis. Use when asked to analyze code with CodeQL, create CodeQL databases, write custom QL queries, perform security audits, or set up CodeQL in CI/CD pipelines.
---

# CodeQL Static Analysis

## When to Use CodeQL

**Ideal scenarios:**
- Source code access with ability to build (for compiled languages)
- Open-source projects or GitHub Advanced Security license
- Need for interprocedural data flow and taint tracking
- Finding complex vulnerabilities requiring AST/CFG analysis
- Comprehensive security audits where analysis time is not critical

**Consider Semgrep instead when:**
- No build capability for compiled languages
- Licensing constraints
- Need fast, lightweight pattern matching
- Simple, single-file analysis is sufficient

### Why Interprocedural Analysis Matters

Simple grep/pattern tools only see one function at a time. Real vulnerabilities often span multiple functions:

```
HTTP Handler → Input Parser → Business Logic → Database Query
     ↓              ↓              ↓              ↓
   source      transforms       passes       sink (SQL)
```

CodeQL tracks data flow across all these steps. A tainted input in the handler can be traced through 5+ function calls to find where it reaches a dangerous sink.

Pattern-based tools miss this because they can't connect `request.param` in file A to `db.execute(query)` in file B.

## When NOT to Use

Do NOT use this skill for:
- Projects that cannot be built (CodeQL requires successful compilation for compiled languages)
- Quick pattern searches (use Semgrep or grep for speed)
- Non-security code quality checks (use linters instead)
- Projects without source code access

## Environment Check

```bash
# Check if CodeQL is installed
command -v codeql >/dev/null 2>&1 && echo "CodeQL: installed" || echo "CodeQL: NOT installed (run install steps below)"
```

## Installation

### CodeQL CLI

```bash
# macOS/Linux (Homebrew)
brew install --cask codeql

# Update
brew upgrade codeql
```

Manual: Download bundle from https://github.com/github/codeql-action/releases

### Trail of Bits Queries (Optional)

Install public ToB security queries for additional coverage:

```bash
# Download ToB query packs
codeql pack download trailofbits/cpp-queries trailofbits/go-queries

# Verify installation
codeql resolve qlpacks | grep trailofbits
```

## Core Workflow

### 1. Create Database

```bash
codeql database create codeql.db --language=<LANG> [--command='<BUILD>'] --source-root=.
```

| Language | `--language=` | Build Required |
|----------|---------------|----------------|
| Python | `python` | No |
| JavaScript/TypeScript | `javascript` | No |
| Go | `go` | No |
| Ruby | `ruby` | No |
| Rust | `rust` | Yes (`--command='cargo build'`) |
| Java/Kotlin | `java` | Yes (`--command='./gradlew build'`) |
| C/C++ | `cpp` | Yes (`--command='make -j8'`) |
| C# | `csharp` | Yes (`--command='dotnet build'`) |
| Swift | `swift` | Yes (macOS only) |

### 2. Run Analysis

```bash
# List available query packs
codeql resolve qlpacks
```

**Run security queries:**

```bash
# SARIF output (recommended)
codeql database analyze codeql.db \
  --format=sarif-latest \
  --output=results.sarif \
  -- codeql/python-queries:codeql-suites/python-security-extended.qls

# CSV output
codeql database analyze codeql.db \
  --format=csv \
  --output=results.csv \
  -- codeql/javascript-queries
```

**With Trail of Bits queries (if installed):**

```bash
codeql database analyze codeql.db \
  --format=sarif-latest \
  --output=results.sarif \
  -- trailofbits/go-queries
```

## Writing Custom Queries

### Query Structure

CodeQL uses SQL-like syntax: `from Type x where P(x) select f(x)`

### Basic Template

```ql
/**
 * @name Find SQL injection vulnerabilities
 * @description Identifies potential SQL injection from user input
 * @kind path-problem
 * @problem.severity error
 * @security-severity 9.0
 * @precision high
 * @id py/sql-injection
 * @tags security
 *       external/cwe/cwe-089
 */

import python
import semmle.python.dataflow.new.DataFlow
import semmle.python.dataflow.new.TaintTracking

module SqlInjectionConfig implements DataFlow::ConfigSig {
  predicate isSource(DataFlow::Node source) {
    // Define taint sources (user input)
    exists(source)
  }

  predicate isSink(DataFlow::Node sink) {
    // Define dangerous sinks (SQL execution)
    exists(sink)
  }
}

module SqlInjectionFlow = TaintTracking::Global<SqlInjectionConfig>;

from SqlInjectionFlow::PathNode source, SqlInjectionFlow::PathNode sink
where SqlInjectionFlow::flowPath(source, sink)
select sink.getNode(), source, sink, "SQL injection from $@.", source.getNode(), "user input"
```

### Query Metadata

| Field | Description | Values |
|-------|-------------|--------|
| `@kind` | Query type | `problem`, `path-problem` |
| `@problem.severity` | Issue severity | `error`, `warning`, `recommendation` |
| `@security-severity` | CVSS score | `0.0` - `10.0` |
| `@precision` | Confidence | `very-high`, `high`, `medium`, `low` |

### Key Language Features

```ql
// Predicates
predicate isUserInput(DataFlow::Node node) {
  exists(Call c | c.getFunc().(Attribute).getName() = "get" and node.asExpr() = c)
}

// Transitive closure: + (one or more), * (zero or more)
node.getASuccessor+()

// Quantification
exists(Variable v | v.getName() = "password")
forall(Call c | c.getTarget().hasName("dangerous") | hasCheck(c))
```

## Creating Query Packs

```bash
codeql pack init myorg/security-queries
```

Structure:
```
myorg-security-queries/
├── qlpack.yml
├── src/
│   └── SqlInjection.ql
└── test/
    └── SqlInjectionTest.expected
```

**qlpack.yml:**
```yaml
name: myorg/security-queries
version: 1.0.0
dependencies:
  codeql/python-all: "*"
```

## CI/CD Integration (GitHub Actions)

```yaml
name: CodeQL Analysis

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
  schedule:
    - cron: '0 0 * * 1'  # Weekly

jobs:
  analyze:
    runs-on: ubuntu-latest
    permissions:
      actions: read
      contents: read
      security-events: write

    strategy:
      matrix:
        language: ['python', 'javascript']

    steps:
      - uses: actions/checkout@v4

      - name: Initialize CodeQL
        uses: github/codeql-action/init@v3
        with:
          languages: ${{ matrix.language }}
          queries: security-extended,security-and-quality
          # Add custom queries/packs:
          # queries: security-extended,./codeql/custom-queries
          # packs: trailofbits/python-queries

      - uses: github/codeql-action/autobuild@v3

      - uses: github/codeql-action/analyze@v3
        with:
          category: "/language:${{ matrix.language }}"
```

## Testing Queries

```bash
codeql test run test/
```

Test file format:
```python
def vulnerable():
    user_input = request.args.get("q")  # Source
    cursor.execute("SELECT * FROM users WHERE id = " + user_input)  # Alert: sql-injection

def safe():
    user_input = request.args.get("q")
    cursor.execute("SELECT * FROM users WHERE id = ?", (user_input,))  # OK
```

## Troubleshooting

| Issue | Solution |
|-------|----------|
| Database creation fails | Clean build environment, verify build command works independently |
| Slow analysis | Use `--threads`, narrow query scope, check query complexity |
| Missing results | Check file exclusions, verify source files were parsed |
| Out of memory | Set `CODEQL_RAM=48000` environment variable (48GB) |
| CMake source path issues | Adjust `--source-root` to point to actual source location |

## Rationalizations to Reject

| Shortcut | Why It's Wrong |
|----------|----------------|
| "No findings means the code is secure" | CodeQL only finds patterns it has queries for; novel vulnerabilities won't be detected |
| "This code path looks safe" | Complex data flow can hide vulnerabilities across 5+ function calls; trace the full path |
| "Small change, low risk" | Small changes can introduce critical bugs; run full analysis on every change |
| "Tests pass so it's safe" | Tests prove behavior, not absence of vulnerabilities; they test expected paths, not attacker paths |
| "The query didn't flag it" | Default query suites don't cover everything; check if custom queries are needed for your domain |

## Resources

- Docs: https://codeql.github.com/docs/
- Query Help: https://codeql.github.com/codeql-query-help/
- Security Lab: https://securitylab.github.com/
- Trail of Bits Queries: https://github.com/trailofbits/codeql-queries
- VSCode Extension: "CodeQL" for query development