Python: fix(devui): validate function approval responses in DevUI executor - #4598
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Evan Mattson (moonbox3) merged 7 commits intoMar 12, 2026
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The DevUI /v1/responses endpoint accepts function_approval_response content without verifying that the request_id corresponds to a real pending approval request issued by the server. This allows forged approval responses to execute arbitrary tools with attacker-controlled arguments, bypassing approval_mode='always_require'. Changes: - Track outgoing approval requests in a server-side registry (_pending_approvals) keyed by request_id - Validate incoming approval responses against this registry; reject any response whose request_id was not issued by the server - Use server-stored function_call data (tool name, arguments, call_id) instead of client-supplied data when constructing the approval response - Consume request_ids on use (pop from registry) to prevent replay attacks Tests: - 8 new tests covering forged rejection, server-data enforcement, anti-replay, multiple independent approvals, and edge cases
Mark Wallace (markwallace-microsoft)
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Eduard van Valkenburg (eavanvalkenburg)
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Summary
Fixes #4597 - The DevUI executor accepts potentially forged
function_approval_responsecontent, allowing arbitrary tool execution without human approval.Problem
The
_convert_input_to_chat_message()method processesfunction_approval_responsecontent items from the client and trusts therequest_id, tool name, and arguments without verifying that the server ever issued a corresponding approval request. This means an attacker can fabricate a response and execute any registered tool with arbitrary arguments, completely bypassingapproval_mode="always_require".This can allow unauthenticated arbitrary tool execution.
Fix
Server-side tracking: When the executor streams events back to the client and encounters a
response.function_approval.requestedevent, it records therequest_idand the server-sidefunction_calldata in_pending_approvals.Validation on response: When a
function_approval_responsearrives, the executor checks therequest_idagainst_pending_approvals. If not found, the response is rejected with a warning log. If found, the server-stored tool name, arguments, and call_id are used. Client-supplied function_call data is ignored.Anti-replay: The
request_idis consumed (popped) on use, preventing the same approval from being replayed.Changes
python/packages/devui/agent_framework_devui/_executor.py- Added_pending_approvalsregistry,_track_approval_request()method, tracking inexecute_streaming(), and validated parsing in_convert_input_to_chat_message()python/packages/devui/tests/devui/test_approval_validation.py- 8 new security regression testsTesting
ruff check/ruff format/pyrightall clean