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Add comprehensive fuzz testing infrastructure with automated CI/CD integration (#25) Implements fuzz testing to ensure the testscript-rs parser is resilient to malformed, malicious, or unexpected input. This addresses security and stability concerns by systematically testing edge cases that could cause crashes, panics, or vulnerabilities. ## What's Added **Fuzz Testing Infrastructure:** - Four specialized fuzz targets using `cargo-fuzz` and libFuzzer - Structured input generation with the `arbitrary` crate - Comprehensive seed corpus with 26+ test cases for better coverage - Complete documentation for developers and CI integration **GitHub Actions Integration:** - Automated daily fuzzing workflow that runs at 2 AM UTC - Manual trigger capability via `workflow_dispatch` with configurable parameters - Automatic crash detection and artifact upload - Corpus preservation for improved coverage over time **Security Testing Coverage:** - **Path traversal attempts**: Tests filenames like `../../etc/passwd` - **Command injection patterns**: Malicious command sequences and arguments - **Memory safety**: Ensures no crashes, infinite loops, or excessive memory usage - **Input validation**: Verifies proper error handling for malformed input - **UTF-8 handling**: Graceful degradation for invalid byte sequences ## Fuzz Targets 1. **`parser`** - Tests the main `parser::parse()` function with completely random bytes 2. **`tokens`** - Focuses on command parsing with various quoting, conditions, and negation 3. **`env_substitution`** - Tests environment variable substitution with edge cases and special characters 4. **`structured`** - Uses `arbitrary` to generate well-formed but boundary-case txtar content ## Usage **Local Testing:** ```bash # Install fuzzing tools cargo install cargo-fuzz rustup default nightly # Run parser fuzzing cargo fuzz run parser # Quick test all targets for target in parser tokens env_substitution structured; do timeout 30 cargo fuzz run "$target" done ``` **GitHub Actions:** 1. Navigate to Actions → "Fuzz Testing" workflow 2. Click "Run workflow" to trigger manual execution 3. Optionally configure duration and run count parameters ## Results All fuzz targets achieve high code coverage (300+ coverage points each) and successfully handle malformed input without panics. The parser maintains deterministic behavior and properly rejects security-sensitive patterns like path traversal attempts. **Files Added:** - `fuzz/` - Complete fuzzing infrastructure - `FUZZ.md` - Quick start documentation - `fuzz/README.md` - Comprehensive fuzzing guide - `.github/workflows/fuzz.yml` - Automated CI/CD workflow - Four fuzz targets with seed corpus files This implementation provides ongoing security assurance as the parser evolves with both local development tools and automated continuous testing through GitHub Actions. <!-- START COPILOT CODING AGENT SUFFIX --> <details> <summary>Original prompt</summary> > > ---- > > *This section details on the original issue you should resolve* > > <issue_title>Add fuzz testing for parser resilience</issue_title> > <issue_description>## Feature Request: Fuzz Testing > > Since testscript-rs parses arbitrary user input in `.txtar` format, we should add fuzz testing to ensure the parser is resilient to malformed, malicious, or unexpected input. > > ## Fuzz Testing Targets > > ### **Primary Target: Parser** > - **`parser::parse()`** - Main entry point for parsing .txtar content > - Test with malformed file headers, invalid command syntax, edge cases > - Ensure parser never panics, always returns proper errors > > ### **Secondary Targets:** > - **Command token parsing** - `parse_command_tokens()` > - **Environment variable substitution** - `substitute_env_vars()` > - **File path handling** - Directory traversal attempts, special characters > > ## Implementation > > Use `cargo-fuzz` with libFuzzer: > > ```toml > # Cargo.toml > [dev-dependencies] > arbitrary = { version = "1.0", features = ["derive"] } > > # fuzz/Cargo.toml > [dependencies.testscript-rs] > path = ".." > > [dependencies] > libfuzzer-sys = "0.4" > arbitrary = { version = "1.0", features = ["derive"] } > ``` > > ## Fuzz Test Cases > > 1. **Random .txtar content** - Completely random bytes > 2. **Structured fuzzing** - Valid-looking but malformed txtar > 3. **Command injection attempts** - Malicious command patterns > 4. **Path traversal attempts** - `../../../etc/passwd` in filenames > 5. **Large inputs** - Very long lines, many files, deep nesting > 6. **Unicode edge cases** - Invalid UTF-8, special characters > > ## Success Criteria > > - Parser never panics on any input > - All errors are properly structured (using our Error types) > - No infinite loops or excessive memory usage > - Security: No path traversal or command injection vulnerabilities > > ## Commands > > ```bash > cargo install cargo-fuzz > cargo fuzz run parser > cargo fuzz run tokens > ```</issue_description> > > ## Comments on the Issue (you are @copilot in this section) > > <comments> > </comments> > </details> Fixes imjasonh/testscript-rs#11 <!-- START COPILOT CODING AGENT TIPS --> --- 💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click [here](https://survey3.medallia.com/?EAHeSx-AP01bZqG0Ld9QLQ) to start the survey. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: imjasonh <210737+imjasonh@users.noreply.github.com>
2025-09-27 19:36:31 +00:00
# Running Fuzz Tests
This document describes how to run fuzz tests for testscript-rs to ensure parser resilience.
## Quick Start
```bash
# Install fuzzing tools
cargo install cargo-fuzz
# Switch to nightly Rust (required for fuzzing)
rustup default nightly
# Run parser fuzzing for 30 seconds
timeout 30 cargo fuzz run parser
# Run all fuzz targets with time limit
for target in parser tokens env_substitution structured; do
echo "Fuzzing $target..."
timeout 60 cargo fuzz run "$target" -- -timeout=10 -runs=10000
done
```
## What Gets Tested
The fuzz tests target potential security and stability issues:
### Security Concerns
- **Path traversal**: `../../etc/passwd` in filenames
- **Command injection**: Malicious command patterns
- **Memory safety**: No crashes, infinite loops, excessive memory usage
- **Input validation**: Proper error handling for malformed input
### Parser Resilience
- **Never panics**: All inputs should return proper Result types
- **Deterministic**: Same input produces same output
- **UTF-8 handling**: Graceful degradation for invalid UTF-8
- **Edge cases**: Empty files, malformed headers, unclosed quotes
## Fuzz Targets
| Target | Purpose |
|--------|---------|
| `parser` | Main parser with random input |
| `tokens` | Command token parsing edge cases |
| `env_substitution` | Environment variable handling |
| `structured` | Well-formed but boundary-case inputs |
## Example Output
```bash
$ cargo fuzz run parser -- -runs=1000
INFO: Loaded 1 modules (1968 inline 8-bit counters)
INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes
#1000 DONE cov: 249 ft: 413 corp: 23/70b lim: 4 exec/s: 0 rss: 44Mb
Done 1000 runs in 1 second(s)
```
No crashes = success! 🎉
## GitHub Actions Integration
A dedicated fuzzing workflow runs daily at 2 AM UTC and can be triggered manually via GitHub Actions. This provides continuous security testing for the parser.
## Switch Back to Stable
```bash
# Return to stable Rust for normal development
rustup default stable
```
See `fuzz/README.md` for detailed documentation.
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