fix(security): validate ticker before using as path component (#618)

The ticker symbol reaches three filesystem-path construction sites
(load_ohlcv cache filename, checkpointer DB path, _log_state results
directory) without validation. A value containing path separators or
"../" escapes the configured cache / checkpoints / results directory.

Two attack vectors:
- Programmatic callers passing arbitrary ticker to propagate()
- Prompt injection via fetched news content steering the LLM into
  tool calls with attacker-chosen ticker

Fix: new safe_ticker_component() validator in tradingagents/dataflows/
utils.py applied at all three sites. Allows the standard ticker
character set ([A-Za-z0-9._\-\^], up to 32 chars) and explicitly
rejects dot-only values like "." and ".." which would otherwise pass
the regex but traverse parent directories. Seven test cases cover
the accepted formats (BRK-B, 7203.T, ^GSPC, etc.) and the rejected
inputs (path separators, null bytes, whitespace, empty values,
overlong strings, dot-only values).

Closes #618.

tradingagents/graph/checkpointer.py

@@ -13,12 +13,16 @@ from typing import Generator
 
 from langgraph.checkpoint.sqlite import SqliteSaver
 
+from tradingagents.dataflows.utils import safe_ticker_component
+
 
 def _db_path(data_dir: str | Path, ticker: str) -> Path:
     """Return the SQLite checkpoint DB path for a ticker."""
+    # Reject ticker values that would escape the checkpoints directory.
+    safe = safe_ticker_component(ticker).upper()
     p = Path(data_dir) / "checkpoints"
     p.mkdir(parents=True, exist_ok=True)
-    return p / f"{ticker.upper()}.db"
+    return p / f"{safe}.db"
 
 
 def thread_id(ticker: str, date: str) -> str:

tradingagents/graph/trading_graph.py

@@ -18,6 +18,7 @@ from tradingagents.llm_clients import create_llm_client
 from tradingagents.agents import *
 from tradingagents.default_config import DEFAULT_CONFIG
 from tradingagents.agents.utils.memory import TradingMemoryLog
+from tradingagents.dataflows.utils import safe_ticker_component
 from tradingagents.agents.utils.agent_states import (
     AgentState,
     InvestDebateState,
@@ -378,8 +379,10 @@ class TradingAgentsGraph:
             "final_trade_decision": final_state["final_trade_decision"],
         }
 
-        # Save to file
-        directory = Path(self.config["results_dir"]) / self.ticker / "TradingAgentsStrategy_logs"
+        # Save to file. Reject ticker values that would escape the
+        # results directory when joined as a path component.
+        safe_ticker = safe_ticker_component(self.ticker)
+        directory = Path(self.config["results_dir"]) / safe_ticker / "TradingAgentsStrategy_logs"
         directory.mkdir(parents=True, exist_ok=True)
 
         log_path = directory / f"full_states_log_{trade_date}.json"