74 lines
3.1 KiB
Swift
74 lines
3.1 KiB
Swift
//
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// NotificationService+Decrypt.swift
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// NotificationService
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//
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// Created by MainasuK Cirno on 2021-4-25.
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//
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import os.log
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import Foundation
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import CryptoKit
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extension NotificationService {
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static func decrypt(payload: Data, salt: Data, auth: Data, privateKey: P256.KeyAgreement.PrivateKey, publicKey: P256.KeyAgreement.PublicKey) -> Data? {
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guard let sharedSecret = try? privateKey.sharedSecretFromKeyAgreement(with: publicKey) else {
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os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s: failed to craete shared secret", ((#file as NSString).lastPathComponent), #line, #function)
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return nil
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}
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let keyMaterial = sharedSecret.hkdfDerivedSymmetricKey(using: SHA256.self, salt: auth, sharedInfo: Data("Content-Encoding: auth\0".utf8), outputByteCount: 32)
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let keyInfo = info(type: "aesgcm", clientPublicKey: privateKey.publicKey.x963Representation, serverPublicKey: publicKey.x963Representation)
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let key = HKDF<SHA256>.deriveKey(inputKeyMaterial: keyMaterial, salt: salt, info: keyInfo, outputByteCount: 16)
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let nonceInfo = info(type: "nonce", clientPublicKey: privateKey.publicKey.x963Representation, serverPublicKey: publicKey.x963Representation)
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let nonce = HKDF<SHA256>.deriveKey(inputKeyMaterial: keyMaterial, salt: salt, info: nonceInfo, outputByteCount: 12)
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let nonceData = nonce.withUnsafeBytes(Array.init)
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guard let sealedBox = try? AES.GCM.SealedBox(combined: nonceData + payload) else {
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os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s: failed to create sealedBox", ((#file as NSString).lastPathComponent), #line, #function)
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return nil
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}
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var _plaintext: Data?
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do {
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_plaintext = try AES.GCM.open(sealedBox, using: key)
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} catch {
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os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s: sealedBox open fail %s", ((#file as NSString).lastPathComponent), #line, #function, error.localizedDescription)
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}
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guard let plaintext = _plaintext else {
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os_log(.info, log: .debug, "%{public}s[%{public}ld], %{public}s: failed to open sealedBox", ((#file as NSString).lastPathComponent), #line, #function)
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return nil
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}
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let paddingLength = Int(plaintext[0]) * 256 + Int(plaintext[1])
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guard plaintext.count >= 2 + paddingLength else {
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print("1")
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fatalError()
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}
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let unpadded = plaintext.suffix(from: paddingLength + 2)
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return Data(unpadded)
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}
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static private func info(type: String, clientPublicKey: Data, serverPublicKey: Data) -> Data {
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var info = Data()
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info.append("Content-Encoding: ".data(using: .utf8)!)
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info.append(type.data(using: .utf8)!)
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info.append(0)
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info.append("P-256".data(using: .utf8)!)
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info.append(0)
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info.append(0)
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info.append(65)
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info.append(clientPublicKey)
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info.append(0)
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info.append(65)
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info.append(serverPublicKey)
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return info
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}
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}
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