feat(exec): require configured secret and header auth for /exec

server/app.py

@@ -1,4 +1,5 @@
 import base64
+import hmac
 import io
 import os
 import subprocess
@@ -49,6 +50,7 @@ SETTINGS = {
     "exec_default_timeout_s": int(os.getenv("CLICKTHROUGH_EXEC_TIMEOUT_S", "30")),
     "exec_max_timeout_s": int(os.getenv("CLICKTHROUGH_EXEC_MAX_TIMEOUT_S", "120")),
     "exec_max_output_chars": int(os.getenv("CLICKTHROUGH_EXEC_MAX_OUTPUT_CHARS", "20000")),
+    "exec_secret": os.getenv("CLICKTHROUGH_EXEC_SECRET", "").strip(),
 }
 
 
@@ -299,6 +301,8 @@ def _resolve_exec_program(shell_name: str, command: str) -> list[str]:
 def _exec_command(req: ExecRequest) -> dict:
     if not SETTINGS["exec_enabled"]:
         raise HTTPException(status_code=403, detail="exec endpoint disabled")
+    if not SETTINGS["exec_secret"]:
+        raise HTTPException(status_code=403, detail="exec secret not configured")
 
     run_dry = SETTINGS["dry_run"] or req.dry_run
     shell_name = _pick_shell(req.shell)
@@ -452,6 +456,7 @@ def health(_: None = Depends(_auth)):
         "allowed_region": SETTINGS["allowed_region"],
         "exec": {
             "enabled": SETTINGS["exec_enabled"],
+            "secret_configured": bool(SETTINGS["exec_secret"]),
             "default_shell": SETTINGS["exec_default_shell"],
             "default_timeout_s": SETTINGS["exec_default_timeout_s"],
             "max_timeout_s": SETTINGS["exec_max_timeout_s"],
@@ -575,7 +580,17 @@ def action(req: ActionRequest, _: None = Depends(_auth)):
 
 
 @app.post("/exec")
-def exec_command(req: ExecRequest, _: None = Depends(_auth)):
+def exec_command(
+    req: ExecRequest,
+    x_clickthrough_exec_secret: Optional[str] = Header(default=None),
+    _: None = Depends(_auth),
+):
+    expected = SETTINGS["exec_secret"]
+    if not expected:
+        raise HTTPException(status_code=403, detail="exec secret not configured")
+    if not x_clickthrough_exec_secret or not hmac.compare_digest(x_clickthrough_exec_secret, expected):
+        raise HTTPException(status_code=401, detail="invalid exec secret")
+
     result = _exec_command(req)
     return {
         "ok": True,