## Threat Model for resolve (module path resolution library)

### 1. Library Overview

- **Library Name:** resolve
- **Brief Description:** Implements Node.js `require.resolve()` algorithm for synchronous and asynchronous file path resolution. Used to locate modules and files in Node.js projects.
- **Key Public APIs/Functions:** `resolve.sync()` / `resolve/sync`, `resolve()` / `resolve/async`

### 2. Define Scope

This threat model focuses on the core path resolution algorithm, including filesystem interaction, option handling, and cache management.

### 3. Conceptual System Diagram

```
Caller Application → resolve(id, options) → Resolution Algorithm → File System
                           │
                           └→ Options Handling
                           └→ Cache System
```

**Trust Boundaries:**
- **Input module IDs:** May come from untrusted sources (user input, configuration)
- **Filesystem access:** The library interacts with the filesystem to resolve paths
- **Options:** Provided by the caller
- **Cache:** Used to improve performance, but could be a vector for tampering or information disclosure if not handled securely

### 4. Identify Assets

- **Integrity of resolution output:** Ensure correct and safe file path matching.
- **Confidentiality of configuration:** Prevent sensitive path information from being leaked.
- **Availability/performance for host application:** Prevent crashes or resource exhaustion.
- **Security of host application:** Prevent path traversal or unintended filesystem access.
- **Reputation of library:** Maintain trust by avoiding supply chain attacks and vulnerabilities[1][3][4].

### 5. Identify Threats

| Component / API / Interaction                       | S  | T  | R  | I  | D  | E  |
|-----------------------------------------------------|----|----|----|----|----|----|
| Public API Call (`resolve/async`, `resolve/sync`)   | ✓  | ✓  | –  | ✓  | –  | –  |
| Filesystem Access                                   | –  | ✓  | –  | ✓  | ✓  | –  |
| Options Handling                                    | ✓  | ✓  | –  | ✓  | –  | –  |
| Cache System                                        | –  | ✓  | –  | ✓  | –  | –  |

**Key Threats:**
- **Spoofing:** Malicious module IDs mimicking legitimate packages, or spoofing configuration options[1].
- **Tampering:** Caller-provided paths altering resolution order, or cache tampering leading to incorrect results[1][4].
- **Information Disclosure:** Error messages revealing filesystem structure or sensitive paths[1].
- **Denial of Service:** Recursive or excessive resolution exhausting filesystem handles or causing application crashes[1].
- **Path Traversal:** Malicious input allowing access to files outside the intended directory[4].

### 6. Mitigation/Countermeasures

| Threat Identified                          | Proposed Mitigation |
|--------------------------------------------|---------------------|
| Spoofing (malicious module IDs/config)     | Sanitize input IDs; validate against known patterns; restrict `basedir` to app-controlled paths[1][4]. |
| Tampering (path traversal, cache)          | Validate input IDs for directory escapes; secure cache reads/writes; restrict cache to trusted sources[1][4]. |
| Information Disclosure (error messages)    | Generic "not found" errors without internal paths; avoid exposing sensitive configuration in errors[1]. |
| Denial of Service (resource exhaustion)    | Limit recursive resolution depth; implement timeout; monitor for excessive filesystem operations[1]. |

### 7. Risk Ranking

- **High:** Path traversal via malicious IDs (if not properly mitigated)
- **Medium:** Cache tampering or spoofing (if cache is not secured)
- **Low:** Information disclosure in errors (if error handling is generic)

### 8. Next Steps & Review

1. **Implement input sanitization for module IDs and configuration.**
2. **Add resolution depth limiting and timeout.**
3. **Audit cache handling for race conditions and tampering.**
4. **Regularly review dependencies for vulnerabilities.**
5. **Keep documentation and threat model up to date.**
6. **Monitor for new threats as the ecosystem and library evolve[1][3].**
