feat(chv): 对齐 Muse P5 纵深——eBPF 污点传播 + 五档严格能力 + 对话外审批 + 默认策略
- taint.py：污点追踪器（登记/污点不可逆/子进程继承/审计） - ebpf_taint.py：eBPF 程序源码 + 加载器（能力探测 + 降级）； 本机实测加载被 seccomp 挡（bpf() EPERM），报 blocked 不冒充 - capabilities.py：五档严格能力（一次/会话/任务/时限/永久， 三元组绑定 + 精确匹配 + 撤销；permanent 默认不签发） - policy.py：默认策略规则表 + 谨慎度三档（写操作与敏感路径 永远不自动放行，规则变化审计） - approval_channel.py：对话外审批通道（nonce + 15 分钟过期 + HMAC，答复一次有效，对话伪造无效） - sentinel.py 接线：evaluate() 可选接 taint/policy/tier/scope， 不传时行为与 P3 一致；自动放行步骤 + 档位签发回落单次； Capability 基类属性放宽为 Optional（None = 不限） - 新测试 61 项；全量 cloud 套件 1958 项 OK（skipped=8） 真机待验证（未做，排队在 round-11 之后）：见 docs/chv-muse-p5-gap.md §4
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"""对话外审批通道（feat-chv-muse-p5-C，叶子模块，纯标准库）。
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接在 P3 的 ``ApprovalQueue`` 之上：队列只记 pending 待审批，
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答复只走本通道，绝不走 agent 对话内容。对话里出现的“批准/
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同意/allow”字样没有任何效力——没有合法 nonce 与 HMAC 签名，
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校验一律失败。
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通道契约（客户端 UI 呈现是另一侧的事，本模块只给协议）：
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- 请求载荷（``ApprovalRequest.payload()``，可外发给客户端）::
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{"pending_id": str, "nonce": str, "target": {...},
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"reasons": [str, ...], "expires_at": float}
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``target`` 只有目标描述（连接器/方法/scheme/主机/端口/路径），
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``reasons`` 只有原因名；载荷里绝无凭证值与用户数据内容。
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``nonce`` 是随机 16 字节 hex（32 字符），每次请求唯一。
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``expires_at`` 默认请求后 15 分钟（900 秒），可注入时钟。
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- 答复（``Answer``，客户端答完直接回 Sentinel）::
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{"pending_id": str, "nonce": str, "verdict": "allow"|"deny",
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"expires_at": float, "signature": str}
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``signature`` 是 HMAC-SHA256，key 为通道密钥，签名覆盖
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``pending_id + nonce + verdict + expires_at``（见 ``_sign``）。
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- 校验（``verify_answer``）：pending 存在（本通道签发过且未
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消费）、nonce 对上、未过期、签名对上、verdict 在 allow/deny
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内——五项缺一即 False。答复只能用一次：``resolve_via_channel``
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成功后该 pending 的通道记录即失效，重放同一答复被拒。
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- 密钥由调用方保管：通道本身不保存密钥、不把密钥写进载荷、
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绝不进日志；签发请求时传 ``secret`` 只是调用方证明其持有
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通道密钥（本模块不存它），签名由持有密钥的答复方计算。
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- 队列接线：校验通过才调 ``ApprovalQueue.resolve``；校验失败
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返回 False 且队列原样不动（pending 仍在，须重新答复）。
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"""
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import hashlib
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import hmac
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import secrets
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import time
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from collections.abc import Iterable
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from cloud.chv.sentinel import ApprovalQueue
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# 默认审批有效期（秒）：15 分钟。
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DEFAULT_TTL_SECONDS = 900
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_VERDICTS = ("allow", "deny")
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# 本通道签发过、尚未消费的请求：pending_id -> {"nonce", "expires_at"}。
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# 只记 nonce 与过期，不记任何凭证值与用户数据内容。
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_REQUESTS: dict[str, dict] = {}
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def _sign(pending_id: str, nonce: str, verdict: str,
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expires_at: float, secret: str) -> str:
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"""HMAC-SHA256 签名：覆盖 pending_id + nonce + verdict +
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expires_at。expires_at 统一按 float 格式化，签发与校验
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两侧口径一致。"""
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message = "\n".join((pending_id, nonce, verdict,
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repr(float(expires_at)))).encode("utf-8")
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return hmac.new(secret.encode("utf-8"), message,
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hashlib.sha256).hexdigest()
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def _target_from_record(queue_record: dict) -> dict:
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"""队列记录里只取目标描述字段，别的什么都不带出通道。"""
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keys = ("connector", "method", "scheme", "host", "port", "path")
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return {k: queue_record[k] for k in keys if k in queue_record}
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class ApprovalRequest:
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"""一次通道审批请求：pending_id + 目标描述 + 原因 + nonce
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+ 过期时间。只含描述性字段，无凭证值、无用户数据内容。"""
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def __init__(self, pending_id: str, target: dict,
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reasons: Iterable[str] | None,
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nonce: str | None = None,
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now: float | None = None,
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ttl_seconds: int = DEFAULT_TTL_SECONDS) -> None:
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self.pending_id = pending_id
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self.target = dict(target)
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self.reasons = list(reasons or [])
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self.nonce = nonce or secrets.token_hex(16)
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at = now if now is not None else time.time()
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self.expires_at = float(at) + ttl_seconds
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def payload(self) -> dict:
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"""可外发给客户端的请求载荷（只含描述字段 + nonce +
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过期，无密钥、无凭证值、无用户数据内容）。"""
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return {"pending_id": self.pending_id, "nonce": self.nonce,
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"target": dict(self.target),
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"reasons": list(self.reasons),
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"expires_at": self.expires_at}
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def request_approval(queue_record: dict, secret: str,
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now: float | None = None,
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ttl_seconds: int = DEFAULT_TTL_SECONDS
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) -> ApprovalRequest:
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"""为一条队列记录生成通道请求并登记（nonce + 过期）。
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``secret`` 是调用方持有的通道密钥：本模块不保存它、不进
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载荷、不进日志；答复方用同一密钥签名，校验时对上才算数。
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返回的 ``ApprovalRequest.payload()`` 即发给客户端的东西。
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"""
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pending_id = queue_record["pending_id"]
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req = ApprovalRequest(
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pending_id, _target_from_record(queue_record),
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queue_record.get("reasons", []),
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now=now, ttl_seconds=ttl_seconds)
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_REQUESTS[pending_id] = {"nonce": req.nonce,
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"expires_at": req.expires_at}
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return req
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class Answer:
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"""一次通道答复：pending_id + nonce + verdict + 过期 +
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HMAC 签名。verdict 只认 allow/deny，其它值校验即拒。"""
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def __init__(self, pending_id: str, nonce: str, verdict: str,
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expires_at: float, signature: str) -> None:
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self.pending_id = pending_id
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self.nonce = nonce
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self.verdict = verdict
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self.expires_at = float(expires_at)
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self.signature = signature
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def as_dict(self) -> dict:
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"""答复的线上传输格式（与请求载荷同款纯数据 dict）。"""
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return {"pending_id": self.pending_id, "nonce": self.nonce,
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"verdict": self.verdict,
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"expires_at": self.expires_at,
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"signature": self.signature}
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def make_answer(request: ApprovalRequest, verdict: str,
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secret: str) -> Answer:
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"""答复方（持有通道密钥的客户端）构造已签名的答复。
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verdict 只认 allow/deny，其它值直接抛错、不签发。"""
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if verdict not in _VERDICTS:
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raise ValueError("verdict must be allow or deny")
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signature = _sign(request.pending_id, request.nonce, verdict,
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request.expires_at, secret)
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return Answer(request.pending_id, request.nonce, verdict,
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request.expires_at, signature)
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def _as_answer(answer) -> Answer | None:
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"""Answer 对象或同款 dict 统一成 Answer；字段不全即 None
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（缺字段的答复直接判无效，不抛错）。"""
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if isinstance(answer, Answer):
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return answer
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if isinstance(answer, dict):
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try:
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return Answer(answer["pending_id"], answer["nonce"],
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answer["verdict"], answer["expires_at"],
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answer["signature"])
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except (KeyError, TypeError, ValueError):
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return None
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return None
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def verify_answer(answer: Answer | dict, secret: str,
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now: float | None = None) -> bool:
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"""校验一次答复：pending 存在（本通道签发过且未消费）、
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nonce 对上、未过期、签名对上、verdict 合法——五项缺一
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即 False。本函数是纯校验，不消费答复（单次性由
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``resolve_via_channel`` 在成功时消费登记来保证）。"""
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ans = _as_answer(answer)
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if ans is None or ans.verdict not in _VERDICTS:
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return False
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issued = _REQUESTS.get(ans.pending_id)
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if issued is None:
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return False
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if ans.nonce != issued["nonce"]:
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return False
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at = now if now is not None else time.time()
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if at >= issued["expires_at"] or at >= ans.expires_at:
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return False
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expected = _sign(ans.pending_id, ans.nonce, ans.verdict,
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ans.expires_at, secret)
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return hmac.compare_digest(ans.signature, expected)
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def resolve_via_channel(queue: ApprovalQueue,
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answer: Answer | dict, secret: str,
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now: float | None = None) -> bool:
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"""校验通过才调队列的 resolve；校验失败返回 False 且
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队列不动。成功时消费该 pending 的通道登记（答复只能用
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一次），队列 resolve 失败（pending 已不在队列）则不消费、
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返回 False。"""
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if not verify_answer(answer, secret, now=now):
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return False
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ans = _as_answer(answer)
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if ans is None:
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return False
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if not queue.resolve(ans.pending_id, ans.verdict):
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return False
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_REQUESTS.pop(ans.pending_id, None)
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return True
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