Restrict PoC command to only run within it's directory, and on a spec…#142
Restrict PoC command to only run within it's directory, and on a spec…#142QuinnDACollins wants to merge 1 commit intomainfrom
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…ific file when encountering a Path Traversal vulnerability
QuinnDACollins
requested review from
QuanZhang-William,
capachino,
evanotero,
heltonduarte and
shrishabh
as code owners
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🤖 Hi @QuinnDACollins, I've received your request, and I'm working on it now! You can track my progress in the logs for more details. |
Summary of ChangesHello @QuinnDACollins, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly improves the security and determinism of the PoC (Proof-of-Concept) command. It introduces a critical restriction that limits PoC script execution to a dedicated, secure directory, mitigating potential risks associated with running untrusted code. Additionally, it refines the process for generating Path Traversal PoCs, ensuring a consistent and verifiable method for demonstrating this specific vulnerability, which includes strict temporary file management. Highlights
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Code Review
This pull request introduces a security enhancement by restricting the execution of Proof-of-Concept (PoC) scripts to a specific directory (.gemini_security/poc), which effectively prevents path traversal attacks. The changes include validation logic in poc.ts and updated tests to cover this new security measure.
My review identifies a critical command injection vulnerability that remains in the runPoc function, which should be addressed. I've also included a couple of medium-severity suggestions to improve code maintainability by reducing code duplication in tests and centralizing hardcoded paths.
| // Validate that the filePath is within the safe PoC directory | ||
| const resolvedFilePath = dependencies.path.resolve(filePath); | ||
| const safePocDir = dependencies.path.resolve(process.cwd(), '.gemini_security/poc'); | ||
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| if (!resolvedFilePath.startsWith(safePocDir + dependencies.path.sep)) { | ||
| return { | ||
| content: [ | ||
| { | ||
| type: 'text', | ||
| text: JSON.stringify({ | ||
| error: `Security Error: PoC execution is restricted to files within '${safePocDir}'. Attempted to access '${resolvedFilePath}'.`, | ||
| }), | ||
| }, | ||
| ], | ||
| isError: true, | ||
| }; | ||
| } |
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While this path validation is an excellent security improvement against path traversal, a critical command injection vulnerability remains. The filePath variable is later used directly in a shell command via execAsync(node ${filePath}). If filePath contains shell metacharacters (e.g., ';', '&&', '|'), it can lead to arbitrary command execution.
To fix this, you should use a method that properly handles arguments and does not execute a shell, such as execFile from child_process.
Example:
import { execFile } from 'child_process';
import { promisify } from 'util';
const execFileAsync = promisify(execFile);
// In runPoc, instead of execAsync:
await execFileAsync('node', [filePath]);This change is crucial to fully secure the PoC execution.
| const mockPath = { | ||
| dirname: (p: string) => p.substring(0, p.lastIndexOf('/')), | ||
| resolve: (p1: string, p2?: string) => { | ||
| if (p2) return p1 + '/' + p2; | ||
| return p1; | ||
| }, | ||
| sep: '/', | ||
| }; |
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To improve maintainability and reduce code duplication, consider defining the mockPath object once at the describe block level and reusing it across all tests within this suite. This will make the test file cleaner and easier to update if the mock implementation needs to change.
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| // Validate that the filePath is within the safe PoC directory | ||
| const resolvedFilePath = dependencies.path.resolve(filePath); | ||
| const safePocDir = dependencies.path.resolve(process.cwd(), '.gemini_security/poc'); |
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The path '.gemini_security/poc' is hardcoded here. This string is also referenced in mcp-server/src/index.ts and test files. To improve maintainability and avoid magic strings, consider defining this path as a constant in a shared location and reusing it across the application.
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📋 Review Summary
This pull request introduces a security measure to restrict the execution of Proof-of-Concept (PoC) scripts to a specific directory, preventing potential path traversal vulnerabilities. The changes are well-implemented and include corresponding tests.
🔍 General Feedback
- The addition of the security check in
poc.tsis a welcome improvement. - The new test case in
poc.test.tseffectively validates the security restriction. - The updated instructions in
index.tsare clear and provide good guidance for generating PoCs for path traversal vulnerabilities.
| // Validate that the filePath is within the safe PoC directory | ||
| const resolvedFilePath = dependencies.path.resolve(filePath); | ||
| const safePocDir = dependencies.path.resolve(process.cwd(), '.gemini_security/poc'); | ||
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| if (!resolvedFilePath.startsWith(safePocDir + dependencies.path.sep)) { |
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| // Validate that the filePath is within the safe PoC directory | |
| const resolvedFilePath = dependencies.path.resolve(filePath); | |
| const safePocDir = dependencies.path.resolve(process.cwd(), '.gemini_security/poc'); | |
| if (!resolvedFilePath.startsWith(safePocDir + dependencies.path.sep)) { | |
| const POC_DIRECTORY = '.gemini_security/poc'; | |
| ... | |
| const allowedPocDir = dependencies.path.resolve(process.cwd(), POC_DIRECTORY); | |
| if (!resolvedFilePath.startsWith(allowedPocDir + dependencies.path.sep)) { | |
| ... |
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The pull request introduces a command injection vulnerability in the runPoc function. The filePath parameter is used in a shell command without proper sanitization, which could allow an attacker to execute arbitrary commands.
🔍 General Feedback
- The path traversal check is a good security measure, but it's not sufficient to prevent command injection.
- It's recommended to use
spawnorforkinstead ofexecorexecAsyncwhen dealing with user input to prevent command injection vulnerabilities.
| * Create a 'poc' directory in '.gemini_security' if it doesn't exist. | ||
| * Generate a Node.js script that demonstrates the vulnerability under the '.gemini_security/poc/' directory. | ||
| * Based on the vulnerability type certain criteria must be met in our script, otherwise generate the PoC to the best of your ability: | ||
| * If the vulnerability is a Path Traversal, the script should demonstrate the vulnerability by creating a temporary file 'gcli_secext_temp.txt' directly outside of the project directory. The script should then try to read the file using the vulnerable code. **IMPORTANT:** The script MUST clean up (delete) the 'gcli_secext_temp.txt' file after the verification step, regardless of whether the read was successful or not. Wrap file operations in try/finally blocks to ensure cleanup. |
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Do we need to rely on the script to do the cleanup? Can we strictly enforce the creation path and then have a deterministic cleanup function that attempts to delete the file always? This would avoid us relying on agent to do the cleanup.
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Thinking further - can we do that with file creation as well? i.e. use a separate function to create the file, then ask the PoC generator to generate exploit such that we are able to access that file, and then use a function to clean up the file. The only part that LLMs would do would be to write the exploit to look for the pre-defined file.
2 participants
Introduce more Determinism in our PoC command, and specifically when generating concept for path traversal