fix(web): sanitize username in report file paths to prevent path traversal (#2678)

* fix: sanitize username in report file paths to prevent path traversal (CWE-22)

* address review: add unit tests for sanitize_username_for_path()

maigret/web/app.py

@@ -99,6 +99,16 @@ async def search_multiple_usernames(usernames, options):
     return results
 
 
+def sanitize_username_for_path(username: str) -> str:
+    """Remove path separators and dangerous components from username for safe file path usage."""
+    # Replace path separators and null bytes
+    sanitized = username.replace('/', '_').replace('\\', '_').replace('\0', '_')
+    # Remove . and .. components
+    sanitized = sanitized.strip('.')
+    # If empty after sanitization, use a fallback
+    return sanitized or '_'
+
+
 def process_search_task(usernames, options, timestamp):
     try:
         loop = asyncio.new_event_loop()
@@ -123,7 +133,8 @@ def process_search_task(usernames, options, timestamp):
 
         individual_reports = []
         for username, id_type, results in general_results:
-            report_base = os.path.join(session_folder, f"report_{username}")
+            safe_username = sanitize_username_for_path(username)
+            report_base = os.path.join(session_folder, f"report_{safe_username}")
 
             csv_path = f"{report_base}.csv"
             json_path = f"{report_base}.json"
@@ -162,16 +173,16 @@ def process_search_task(usernames, options, timestamp):
                 {
                     'username': username,
                     'csv_file': os.path.join(
-                        f"search_{timestamp}", f"report_{username}.csv"
+                        f"search_{timestamp}", f"report_{safe_username}.csv"
                     ),
                     'json_file': os.path.join(
-                        f"search_{timestamp}", f"report_{username}.json"
+                        f"search_{timestamp}", f"report_{safe_username}.json"
                     ),
                     'pdf_file': os.path.join(
-                        f"search_{timestamp}", f"report_{username}.pdf"
+                        f"search_{timestamp}", f"report_{safe_username}.pdf"
                     ),
                     'html_file': os.path.join(
-                        f"search_{timestamp}", f"report_{username}.html"
+                        f"search_{timestamp}", f"report_{safe_username}.html"
                     ),
                     'claimed_profiles': claimed_profiles,
                 }

tests/test_sanitize_username.py

@@ -0,0 +1,28 @@
+import pytest
+
+from maigret.web.app import sanitize_username_for_path
+
+
+@pytest.mark.parametrize(
+    "input_username, expected",
+    [
+        ("../../tmp/x", "_.._tmp_x"),
+        ("..", "_"),
+        ("....", "_"),
+        ("foo/bar", "foo_bar"),
+        ("\0foo", "_foo"),
+        ("normaluser123", "normaluser123"),
+    ],
+)
+def test_sanitize_username_for_path(input_username, expected):
+    result = sanitize_username_for_path(input_username)
+    assert result == expected
+    # Verify no path separators or null bytes remain
+    assert "/" not in result
+    assert "\\" not in result
+    assert "\0" not in result
+    # Verify result is not empty
+    assert len(result) > 0
+    # Verify no leading/trailing dots
+    assert not result.startswith(".")
+    assert not result.endswith(".")