84 lines
2.7 KiB
Swift
84 lines
2.7 KiB
Swift
import CryptoKit
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import Foundation
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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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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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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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print(error)
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}
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guard let plaintext = _plaintext else {
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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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private static 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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extension String {
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func escape() -> String {
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return replacingOccurrences(of: "&", with: "&")
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.replacingOccurrences(of: "<", with: "<")
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.replacingOccurrences(of: ">", with: ">")
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.replacingOccurrences(of: """, with: "\"")
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.replacingOccurrences(of: "'", with: "'")
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.replacingOccurrences(of: "'", with: "’")
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}
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func URLSafeBase64ToBase64() -> String {
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var base64 = replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
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let countMod4 = count % 4
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if countMod4 != 0 {
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base64.append(String(repeating: "=", count: 4 - countMod4))
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}
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return base64
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}
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}
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