fix(security): remediate path traversal vulnerabilities in file operations

- Fix critical vulnerability: sanitize GPT metadata filename before use
- Fix insecure string-based path validation with pathlib methods
- Add validation for GPT-extracted filenames
- Add comprehensive security test suite (24 tests)
- Document all findings in SECURITY_AUDIT.md

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/tasks/embed_metadata_into_pdf.py

@@ -5,6 +5,7 @@ import logging
 import os
 import shutil
 import tempfile
+from pathlib import Path
 
 import PyPDF2  # Replace fitz with PyPDF2
 
@@ -16,6 +17,7 @@ from app.models import FileRecord
 from app.tasks.finalize_document_storage import finalize_document_storage
 from app.tasks.retry_config import BaseTaskWithRetry
 from app.utils import log_task_progress
+from app.utils.filename_utils import sanitize_filename
 
 logger = logging.getLogger(__name__)
 
@@ -141,7 +143,10 @@ def embed_metadata_into_pdf(self, local_file_path: str, extracted_text: str, met
         log_task_progress(task_id, "modify_pdf", "success", "PDF metadata embedded", file_id=file_id)
 
         # Use the suggested filename from metadata; if not provided, use the original basename.
+        # SECURITY: Sanitize filename to prevent path traversal vulnerabilities
         suggested_filename = metadata.get("filename", os.path.splitext(os.path.basename(local_file_path))[0])
+        # Sanitize the filename to remove path separators and dangerous characters
+        suggested_filename = sanitize_filename(suggested_filename)
         # Remove any extension and then add .pdf
         suggested_filename = os.path.splitext(suggested_filename)[0]
         # Define the final directory based on settings.workdir and ensure it exists.
@@ -184,13 +189,21 @@ def embed_metadata_into_pdf(self, local_file_path: str, extracted_text: str, met
         finalize_document_storage.delay(original_file, final_file_path, metadata, file_id=file_id)
 
         # After triggering final storage, delete the original file if it is in workdir/tmp.
-        workdir_tmp = os.path.join(settings.workdir, TMP_SUBDIR)
-        if original_file.startswith(workdir_tmp) and os.path.exists(original_file):
-            try:
-                os.remove(original_file)
-                logger.info(f"[{task_id}] Deleted original file from {original_file}")
-            except Exception as e:
-                logger.error(f"[{task_id}] Could not delete original file {original_file}: {e}")
+        # SECURITY: Use pathlib for safe path validation to prevent path traversal
+        workdir_tmp_path = Path(settings.workdir) / TMP_SUBDIR
+        try:
+            original_file_path = Path(original_file).resolve()
+            workdir_tmp_resolved = workdir_tmp_path.resolve()
+            
+            # Check if file is within workdir/tmp and exists
+            if original_file_path.is_relative_to(workdir_tmp_resolved) and original_file_path.exists():
+                try:
+                    original_file_path.unlink()
+                    logger.info(f"[{task_id}] Deleted original file from {original_file}")
+                except Exception as e:
+                    logger.error(f"[{task_id}] Could not delete original file {original_file}: {e}")
+        except (ValueError, OSError) as e:
+            logger.error(f"[{task_id}] Error validating path for deletion {original_file}: {e}")
 
         return {"file": final_file_path, "metadata_file": json_path, "status": "Metadata embedded"}
 

app/tasks/extract_metadata_with_gpt.py

@@ -122,6 +122,24 @@ def extract_metadata_with_gpt(self, filename: str, cleaned_text: str, file_id: i
             return {}
 
         metadata = json.loads(json_text)
+        
+        # SECURITY: Validate filename format from GPT to prevent path traversal
+        # The prompt requests filenames with only letters, numbers, periods, and underscores
+        # Enforce this constraint to prevent malicious filenames
+        import re
+        filename = metadata.get("filename", "")
+        if filename:
+            # Check if filename contains only safe characters (alphanumeric, dash, underscore, period, space)
+            # This matches the sanitize_filename behavior but validates before use
+            if not re.match(r'^[\w\-\. ]+$', filename):
+                logger.warning(f"[{task_id}] Invalid filename format from GPT: '{filename}', using fallback")
+                # Reset to empty to trigger fallback to original filename
+                metadata["filename"] = ""
+            # Additional check: ensure no path traversal patterns
+            elif ".." in filename or "/" in filename or "\\" in filename:
+                logger.warning(f"[{task_id}] Path traversal attempt in GPT filename: '{filename}', using fallback")
+                metadata["filename"] = ""
+        
         logger.info(f"[{task_id}] Extracted metadata: {metadata}")
         log_task_progress(
             task_id, "parse_metadata", "success", f"Parsed metadata: {list(metadata.keys())}", file_id=file_id