我已经在 Paypal 中使用 Sandbox 成功实现了 webhook 集成。现在我想让它更安全，以便只接受 Paypal 签名的通知。我试图使用验证 webhook 签名
https://developer.paypal.com/docs/api/webhooks/v1/#verify-webhook-signature_post
但它总是返回FAILURE。
请求是：
{"auth_algo":"SHA256withRSA","transmission_time":"2020-08-17T12:11:08Z","cert_url":"https://api.sandbox.paypal.com/v1/notifications/certs/CERT- 360caa42-fca2a594-1d93a270","webhook_id":"0JD18557VD498931R","transmission_id":"bbaae190-e082-11ea-aa52-1fdbf2bc8461","webhook_event":{"summary":"5.0 美元的付款完成"," event_type":"PAYMENT.SALE.COMPLETED","create_time":"2020-08-17T12:11:05.015Z","resource":{"billing_agreement_id":"I-DNVD3H9UWYHL","amount":{"total ":"5.00","currency":"USD","details":{"subtotal":"5.00"}},"payment_mode":"INSTANT_TRANSFER","update_time":"2020-08-17T12:10:39Z","create_time":"2020-08-17T12:10:39Z","protection_eligibility_type":"ITEM_NOT_RECEIVED_ELIGIBLE,UNAUTHORIZED_PAYMENT_ELIGIBLE","transaction_fee":{"currency" :"USD","value":"0.45"},"protection_eligibility":"ELIGIBLE","links":[{"method":"GET","rel":"self","href":"https ://api.sandbox.paypal.com/v1/payments/sale/8TV124151P468690Y"},{"method":"POST","rel":"refund","href":"https://api.sandbox .paypal.com/v1/payments/sale/8TV124151P468690Y/refund"}],"id":"8TV124151P468690Y","state":"completed","invoice_number":""},"resource_type":"sale","links":[{"href":"https://api.sandbox.paypal.com/v1/notifications/webhooks-events/WH-2XT265922L1486124-74F09092JL7840709"," rel":"self","targetSchema":null,"method":"GET","enctype":null,"schema":null},{"href":"https://api.sandbox.paypal. com/v1/notifications/webhooks-events/WH-2XT265922L1486124-74F09092JL7840709/resend","rel":"resend","targetSchema":null,"method":"POST","enctype":null,"schema" :null}],"id":"WH-2XT265922L1486124-74F09092JL7840709"},"transmission_sig":"RYILWohVPkK0hUrMjTSU3+fCgd6NTgqkjrZtsOJiC7FR3U3atOK1k29/Md8DQRReAicdfOpXrS7E4vrvB17HOM39w/D3i4Ohy34HL3CqSsZovL69lhfFmviCGkXjjSbkBhpKGJvQAB4q0E9AWl/SBZc4MUNGezIbk/laJZ6ikQuwGeEHCFaPVrza7kSlZRo03lM9sYSb7q3ixewYmz8voKIyJ2RYjOgsAohNFWgovtKwG+ac66YCp3ZRJLe4fL2Q1UaEDn5BnUhK+5Q2+EqD+BixpqNTuSmYqRwkyDTdrH1EPV5DRU4uYM0gJLXnBovGaqHe8JujpVs+dJu4Mrmgdg=="}
结果是
{“验证状态”：“失败”}
有人可以帮忙吗，拜托！！