| 1 | """MCP invocation gateway: lookup, validation, policy, timeout and normalization.""" |
| 2 | from __future__ import annotations |
| 3 | |
| 4 | import asyncio |
| 5 | import time |
| 6 | from typing import Any |
| 7 | |
| 8 | from pydantic import ValidationError |
| 9 | |
| 10 | from app.audit import McpAuditSink |
| 11 | from app.contracts import ( |
| 12 | McpAuthContext, |
| 13 | McpErrorCode, |
| 14 | McpGatewayError, |
| 15 | McpResultEnvelope, |
| 16 | normalize_request_id, |
| 17 | ) |
| 18 | from app.policy import McpToolPolicy |
| 19 | from app.registry import McpToolRegistry |
| 20 | |
| 21 | |
| 22 | class McpInvocationService: |
| 23 | def __init__( |
| 24 | self, |
| 25 | registry: McpToolRegistry, |
| 26 | policy: McpToolPolicy, |
| 27 | audit: McpAuditSink, |
| 28 | *, |
| 29 | timeout_seconds: float, |
| 30 | ) -> None: |
| 31 | if timeout_seconds <= 0: |
| 32 | raise ValueError("timeout_seconds must be positive") |
| 33 | self.registry = registry |
| 34 | self.policy = policy |
| 35 | self.audit = audit |
| 36 | self.timeout_seconds = timeout_seconds |
| 37 | |
| 38 | async def invoke( |
| 39 | self, |
| 40 | tool: str, |
| 41 | arguments: dict[str, Any] | None, |
| 42 | auth: McpAuthContext, |
| 43 | *, |
| 44 | request_id: str | int | None = None, |
| 45 | ) -> dict[str, Any]: |
| 46 | request_id_value = normalize_request_id(request_id) |
| 47 | started = time.perf_counter() |
| 48 | definition = self.registry.get(tool) |
| 49 | self.audit.emit( |
| 50 | "MCP_TOOL_INVOKED", |
| 51 | tool=tool, |
| 52 | request_id=request_id_value, |
| 53 | auth=auth, |
| 54 | risk_class=definition.risk_class if definition else None, |
| 55 | kind=definition.kind if definition else None, |
| 56 | ) |
| 57 | |
| 58 | if definition is None: |
| 59 | return self._failed( |
| 60 | tool, request_id_value, auth, McpErrorCode.MCP_TOOL_NOT_FOUND, started |
| 61 | ) |
| 62 | |
| 63 | try: |
| 64 | self.policy.authorize(definition, auth) |
| 65 | except McpGatewayError as exc: |
| 66 | return self._denied(tool, request_id_value, auth, definition, exc.code, started) |
| 67 | |
| 68 | try: |
| 69 | validated = definition.input_model.model_validate(arguments or {}) |
| 70 | except ValidationError: |
| 71 | return self._failed( |
| 72 | tool, request_id_value, auth, McpErrorCode.INVALID_ARGUMENT, started, definition |
| 73 | ) |
| 74 | |
| 75 | try: |
| 76 | async with asyncio.timeout(self.timeout_seconds): |
| 77 | result = await definition.handler(validated, auth, request_id_value) |
| 78 | except TimeoutError: |
| 79 | return self._failed( |
| 80 | tool, request_id_value, auth, McpErrorCode.DOWNSTREAM_TIMEOUT, started, definition |
| 81 | ) |
| 82 | except McpGatewayError as exc: |
| 83 | return self._failed(tool, request_id_value, auth, exc.code, started, definition) |
| 84 | except Exception: |
| 85 | return self._failed( |
| 86 | tool, |
| 87 | request_id_value, |
| 88 | auth, |
| 89 | McpErrorCode.DOWNSTREAM_UNAVAILABLE, |
| 90 | started, |
| 91 | definition, |
| 92 | ) |
| 93 | |
| 94 | envelope = McpResultEnvelope.success( |
| 95 | tool=tool, |
| 96 | request_id=request_id_value, |
| 97 | data=result.data, |
| 98 | generated_at=result.generated_at, |
| 99 | rule_engine_version=result.rule_engine_version, |
| 100 | warnings=list(result.warnings), |
| 101 | ) |
| 102 | self.audit.emit( |
| 103 | "MCP_TOOL_SUCCEEDED", |
| 104 | tool=tool, |
| 105 | request_id=request_id_value, |
| 106 | auth=auth, |
| 107 | risk_class=definition.risk_class, |
| 108 | kind=definition.kind, |
| 109 | duration_ms=round((time.perf_counter() - started) * 1000), |
| 110 | ) |
| 111 | return envelope.wire() |
| 112 | |
| 113 | def _denied(self, tool, request_id, auth, definition, code, started): |
| 114 | self.audit.emit( |
| 115 | "MCP_TOOL_DENIED", |
| 116 | tool=tool, |
| 117 | request_id=request_id, |
| 118 | auth=auth, |
| 119 | risk_class=definition.risk_class, |
| 120 | kind=definition.kind, |
| 121 | code=code.value, |
| 122 | duration_ms=round((time.perf_counter() - started) * 1000), |
| 123 | ) |
| 124 | return McpResultEnvelope.failure( |
| 125 | tool=tool, request_id=request_id, code=code |
| 126 | ).wire() |
| 127 | |
| 128 | def _failed(self, tool, request_id, auth, code, started, definition=None): |
| 129 | self.audit.emit( |
| 130 | "MCP_TOOL_FAILED", |
| 131 | tool=tool, |
| 132 | request_id=request_id, |
| 133 | auth=auth, |
| 134 | risk_class=definition.risk_class if definition else None, |
| 135 | kind=definition.kind if definition else None, |
| 136 | code=code.value, |
| 137 | duration_ms=round((time.perf_counter() - started) * 1000), |
| 138 | ) |
| 139 | return McpResultEnvelope.failure( |
| 140 | tool=tool, request_id=request_id, code=code |
| 141 | ).wire() |