103 lines
3.4 KiB
Swift
103 lines
3.4 KiB
Swift
//
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// Copyright 2024 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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import Foundation
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public import LibSignalClient
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public struct MessageBackupKeyMaterialImpl: MessageBackupKeyMaterial {
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private let mrbkStore: MediaRootBackupKeyStore
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private let svrKeyDeriver: SVRKeyDeriver
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public init(
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mrbkStore: MediaRootBackupKeyStore,
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svrKeyDeriver: SVRKeyDeriver
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) {
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self.mrbkStore = mrbkStore
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self.svrKeyDeriver = svrKeyDeriver
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}
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/// Get the root backup key used by the encryption mode. The key may be derived
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/// differently depending on the mode, but derivations downstream of it work the same.
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public func backupKey(
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type: MessageBackupAuthCredentialType,
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tx: DBReadTransaction
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) throws(MessageBackupKeyMaterialError) -> BackupKey {
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let resultData: Data
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switch type {
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case .media:
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guard let backupKey = mrbkStore.getMediaRootBackupKey(tx: tx) else {
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throw MessageBackupKeyMaterialError.missingMediaRootBackupKey
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}
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resultData = backupKey
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case .messages:
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guard let backupKey = svrKeyDeriver.data(for: .backupKey, tx: tx) else {
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throw MessageBackupKeyMaterialError.missingMasterKey
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}
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guard backupKey.type == .backupKey else {
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owsFailDebug("Wrong key provided")
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throw MessageBackupKeyMaterialError.missingMasterKey
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}
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resultData = backupKey.rawData
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}
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do {
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return try resultData.withUnsafeBytes { try BackupKey(contents: Array($0)) }
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} catch {
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throw MessageBackupKeyMaterialError.derivationError(error)
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}
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}
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public func mediaEncryptionMetadata(
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mediaName: String,
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type: MediaTierEncryptionType,
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tx: any DBReadTransaction
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) throws(MessageBackupKeyMaterialError) -> MediaTierEncryptionMetadata {
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let backupKey = try backupKey(type: .media, tx: tx)
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let mediaId: [UInt8]
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do {
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mediaId = try backupKey.deriveMediaId(mediaName)
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} catch {
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throw MessageBackupKeyMaterialError.derivationError(error)
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}
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let keyBytes: [UInt8]
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do {
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switch type {
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case .attachment:
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keyBytes = try backupKey.deriveMediaEncryptionKey(mediaId)
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case .thumbnail:
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keyBytes = try backupKey.deriveThumbnailTransitEncryptionKey(mediaId)
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}
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} catch {
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throw MessageBackupKeyMaterialError.derivationError(error)
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}
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return MediaTierEncryptionMetadata(
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type: type,
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mediaId: Data(mediaId),
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hmacKey: Data(Array(keyBytes[0..<32])),
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aesKey: Data(Array(keyBytes[32..<64]))
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)
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}
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}
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#if TESTABLE_BUILD
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open class MessageBackupKeyMaterialMock: MessageBackupKeyMaterial {
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public func backupKey(
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type: MessageBackupAuthCredentialType,
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tx: any DBReadTransaction
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) throws(MessageBackupKeyMaterialError) -> BackupKey {
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fatalError("Unimplemented")
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}
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public func mediaEncryptionMetadata(
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mediaName: String,
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type: MediaTierEncryptionType,
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tx: any DBReadTransaction
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) throws(MessageBackupKeyMaterialError) -> MediaTierEncryptionMetadata {
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fatalError("Unimplemented")
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}
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}
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#endif
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