mirror of https://github.com/oxen-io/session-ios
Add encryption to DeviceNames.
parent
79375e20b2
commit
0d20ebc62b
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//
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// Copyright (c) 2018 Open Whisper Systems. All rights reserved.
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//
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import Foundation
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import Curve25519Kit
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@objc
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public enum DeviceNameError: Int, Error {
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case assertionFailure
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}
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@objc
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public class DeviceNames: NSObject {
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// Never instantiate this class.
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private override init() {}
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@objc
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public class func encryptDeviceName(plaintext: String,
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identityKeyPair: ECKeyPair) throws -> Data {
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guard let plaintextData = plaintext.data(using: .utf8) else {
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owsFail("Could not convert text to UTF-8.")
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}
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let ephemeralKeyPair = Curve25519.generateKeyPair()
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// master_secret = ECDH(ephemeral_private, identity_public).
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let masterSecret: Data
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do {
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masterSecret = try Curve25519.generateSharedSecret(fromPublicKey: identityKeyPair.publicKey,
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privateKey: ephemeralKeyPair.privateKey)
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} catch {
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Logger.error("Could not generate shared secret: \(error)")
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throw error
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}
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// synthetic_iv = HmacSHA256(key=HmacSHA256(key=master_secret, input=“auth”), input=plaintext)[0:16]
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guard let syntheticIVInput = "auth".data(using: .utf8) else {
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owsFail("Could not convert text to UTF-8.")
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}
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guard let syntheticIVKey = Cryptography.computeSHA256HMAC(syntheticIVInput, withHMACKey: masterSecret) else {
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owsFailDebug("Could not compute synthetic IV key.")
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throw DeviceNameError.assertionFailure
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}
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let ivLength: UInt = 16
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guard let syntheticIV = Cryptography.truncatedSHA256HMAC(plaintextData, withHMACKey: syntheticIVKey, truncation: ivLength) else {
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owsFailDebug("Could not compute synthetic IV.")
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throw DeviceNameError.assertionFailure
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}
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// cipher_key = HmacSHA256(key=HmacSHA256(key=master_secret, “cipher”), input=synthetic_iv)
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guard let cipherKeyInput = "cipher".data(using: .utf8) else {
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owsFail("Could not convert text to UTF-8.")
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}
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guard let cipherKeyKey = Cryptography.computeSHA256HMAC(cipherKeyInput, withHMACKey: masterSecret) else {
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owsFailDebug("Could not compute cipher key key.")
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throw DeviceNameError.assertionFailure
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}
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guard let cipherKey = Cryptography.computeSHA256HMAC(syntheticIV, withHMACKey: cipherKeyKey) else {
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owsFailDebug("Could not compute cipher key.")
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throw DeviceNameError.assertionFailure
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}
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// cipher_text = AES-CTR(key=cipher_key, input=plaintext, counter=0)
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//
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// TODO: Is this right?
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let cipherTextIV = Data(count: Int(kAES256CTR_IVLength))
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guard let cipherTextKey = OWSAES256Key(data: cipherKey) else {
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owsFailDebug("Invalid cipher key.")
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throw DeviceNameError.assertionFailure
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}
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guard let cipherText: AES256CTREncryptionResult = Cryptography.encryptAESCTR(plaintextData: plaintextData, initializationVector: cipherTextIV, key: cipherTextKey) else {
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owsFailDebug("Could not compute cipher text.")
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throw DeviceNameError.assertionFailure
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}
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let protoBuilder = SignalIOSProtoDeviceName.builder(ephemeralPublic: ephemeralKeyPair.publicKey,
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syntheticIv: syntheticIV,
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ciphertext: cipherText.ciphertext)
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let protoData = try protoBuilder.buildSerializedData()
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let protoDataBase64 = protoData.base64EncodedData()
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return protoDataBase64
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}
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}
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