53 lines
2.0 KiB
Swift
53 lines
2.0 KiB
Swift
import CryptoSwift
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import Curve25519Kit
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import SessionUtilitiesKit
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/// A fallback session cipher which uses the the recipient's public key to encrypt data.
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@objc public final class FallBackSessionCipher : NSObject {
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/// The hex encoded public key of the recipient.
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private let recipientPublicKey: String
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private let privateKey: Data?
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private let ivSize: Int32 = 16
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private lazy var recipientPublicKeyAsData: Data = {
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var recipientPublicKey = self.recipientPublicKey
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if recipientPublicKey.count == 66 && recipientPublicKey.hasPrefix("05") {
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let index = recipientPublicKey.index(recipientPublicKey.startIndex, offsetBy: 2)
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recipientPublicKey = recipientPublicKey.substring(from: index)
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}
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return Data(hex: recipientPublicKey)
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}()
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private lazy var symmetricKey: Data? = {
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guard let privateKey = privateKey else { return nil }
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let keyPair = ECKeyPair(publicKey: recipientPublicKeyAsData, privateKey: privateKey)
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return Curve25519.generateSharedSecret(fromPublicKey: recipientPublicKeyAsData, andKeyPair: keyPair)
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}()
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@objc public init(recipientPublicKey: String, privateKey: Data?) {
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self.recipientPublicKey = recipientPublicKey
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self.privateKey = privateKey
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super.init()
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}
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@objc public func encrypt(_ plaintext: Data) -> Data? {
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guard let symmetricKey = symmetricKey else { return nil }
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do {
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return try DiffieHellman.encrypt(plaintext, using: symmetricKey)
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} catch {
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SNLog("Couldn't encrypt message using fallback session cipher due to error: \(error).")
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return nil
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}
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}
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@objc public func decrypt(_ ivAndCiphertext: Data) -> Data? {
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guard let symmetricKey = symmetricKey else { return nil }
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do {
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return try DiffieHellman.decrypt(ivAndCiphertext, using: symmetricKey)
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} catch {
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SNLog("Couldn't decrypt message using fallback session cipher due to error: \(error).")
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return nil
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}
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}
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}
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