53 lines
1.6 KiB
Swift
53 lines
1.6 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 class DecryptingStreamTransform: StreamTransform, FinalizableStreamTransform {
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public enum Error: Swift.Error {
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case initialBufferTooSmall
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case notInitialized
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}
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public enum Constants {
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static let HeaderSize = 16
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}
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private let encryptionKey: Data
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private var cipherContext: CipherContext?
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public var hasInitialized = false
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public var hasFinalized: Bool { hasInitialized && self.cipherContext == nil }
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init(encryptionKey: Data) throws {
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self.encryptionKey = encryptionKey
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}
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public func transform(data: Data) throws -> Data {
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var inputBuffer = data
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if !hasInitialized {
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guard inputBuffer.count > Constants.HeaderSize else { throw Error.initialBufferTooSmall }
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// read the IV
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let iv = inputBuffer.prefix(Constants.HeaderSize)
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inputBuffer.removeFirst(Constants.HeaderSize)
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self.cipherContext = try CipherContext(
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operation: .decrypt,
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algorithm: .aes,
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options: .pkcs7Padding,
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key: encryptionKey,
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iv: iv,
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)
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hasInitialized = true
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}
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return try self.cipherContext?.update(inputBuffer) ?? { throw OWSGenericError("already finalized") }()
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}
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public func finalize() throws -> Data {
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guard hasInitialized else { throw Error.notInitialized }
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return try self.cipherContext.take()?.finalize() ?? Data()
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}
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}
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