Security: Remove shell=True to prevent command injection (Fix #261) #293
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Pull request overview
This PR mitigates a command injection vulnerability in the FRI Flask server by removing shell=True usage and adding input validation for user-supplied values used in subprocess calls for /contribute and /library.
Changes:
- Added a regex-based
validate_input()helper and applied it to request parameters in/contributeand/library. - Switched Windows subprocess execution to
subprocess.run(..., check=True, capture_output=True, text=True)(noshell=True). - Added explicit handling for
ValueErrorandCalledProcessErrorin both endpoints.
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- Add validate_filename() for strict filename validation (no path traversal) - Add validate_text_field() for PR title/body (allow punctuation, check length) - Add get_error_output() to extract error details from CalledProcessError - Use cmd.exe /c to invoke .bat scripts on Windows for shell=False compatibility - Add required parameter to validate_input() to reject None for required fields - Normalize None to empty string for optional fields - Include captured output in error responses for better diagnostics
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@pradeeban
Fixes critical command injection vulnerability in FRI server endpoints (/contribute and /library).
Root Cause
User input was executed via subprocess.check_output() with shell=True, allowing attackers to inject arbitrary shell commands via malformed JSON payloads (e.g., {"branch": "main & rm -rf /"}).
Fix
Removed shell=True from subprocess calls on Windows
Switched to subprocess.run() with check=True, capture_output=True, text=True for safe argument handling
Added input validation function (validate_input()) using regex pattern ^[a-zA-Z0-9_-/. ]+$
All user-supplied parameters (study, path, auth, branch, title, desc, filename) are now validated before execution
Added proper error handling for ValueError and CalledProcessError
Changes
/contribute endpoint: Removed shell=True, added input validation for 6 parameters
/library endpoint: Removed shell=True, added input validation for 2 parameters
Impact
Testing
#261