Add support for AES CFB mode in _CryptoExtras (#252)

Sources/_CryptoExtras/AES/AES_CFB.swift

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftCrypto open source project
+//
+// Copyright (c) 2024 Apple Inc. and the SwiftCrypto project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.md for the list of SwiftCrypto project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Crypto
+import Foundation
+
+@usableFromInline
+typealias AESCFBImpl = OpenSSLAESCFBImpl
+
+extension AES {
+    public enum _CFB {
+        @inlinable
+        public static func encrypt<Plaintext: DataProtocol>(
+            _ plaintext: Plaintext,
+            using key: SymmetricKey,
+            iv: AES._CFB.IV
+        ) throws -> Data {
+            let bytes: ContiguousBytes = plaintext.regions.count == 1 ? plaintext.regions.first! : Array(plaintext)
+            return try AESCFBImpl.encryptOrDecrypt(.encrypt, bytes, using: key, iv: iv)
+        }
+
+        @inlinable
+        public static func decrypt<Ciphertext: DataProtocol>(
+            _ ciphertext: Ciphertext,
+            using key: SymmetricKey,
+            iv: AES._CFB.IV
+        ) throws -> Data {
+            let bytes: ContiguousBytes = ciphertext.regions.count == 1 ? ciphertext.regions.first! : Array(ciphertext)
+            return try AESCFBImpl.encryptOrDecrypt(.decrypt, bytes, using: key, iv: iv)
+        }
+    }
+}
+
+extension AES._CFB {
+    public struct IV: Sendable {
+        // AES CFB uses a 128-bit IV.
+        private var ivBytes: (UInt64, UInt64)
+
+        public init() {
+            var rng = SystemRandomNumberGenerator()
+            self.ivBytes = (rng.next(), rng.next())
+        }
+
+        public init<IVBytes: Collection>(ivBytes: IVBytes) throws where IVBytes.Element == UInt8 {
+            guard ivBytes.count == 16 else {
+                throw CryptoKitError.incorrectParameterSize
+            }
+
+            self.ivBytes = (0, 0)
+
+            Swift.withUnsafeMutableBytes(of: &self.ivBytes) { bytesPtr in
+                bytesPtr.copyBytes(from: ivBytes)
+            }
+        }
+
+        mutating func withUnsafeMutableBytes<ReturnType>(_ body: (UnsafeMutableRawBufferPointer) throws -> ReturnType) rethrows -> ReturnType {
+            return try Swift.withUnsafeMutableBytes(of: &self.ivBytes, body)
+        }
+    }
+}

Sources/_CryptoExtras/AES/BoringSSL/AES_CFB_boring.swift

@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftCrypto open source project
+//
+// Copyright (c) 2024 Apple Inc. and the SwiftCrypto project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.md for the list of SwiftCrypto project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@_implementationOnly import CCryptoBoringSSL
+import Crypto
+import Foundation
+
+@usableFromInline
+enum OpenSSLAESCFBImpl {
+    @usableFromInline
+    enum Mode {
+        case encrypt
+        case decrypt
+
+        @usableFromInline
+        var _boringSSLParameter: Int32 {
+            switch self {
+            case .encrypt: return AES_ENCRYPT
+            case .decrypt: return AES_DECRYPT
+            }
+        }
+    }
+
+    @inlinable
+    static func encryptOrDecrypt<Plaintext: ContiguousBytes>(
+        _ mode: Mode,
+        _ plaintext: Plaintext,
+        using key: SymmetricKey,
+        iv: AES._CFB.IV
+    ) throws -> Data {
+        guard [128, 192, 256].contains(key.bitCount) else {
+            throw CryptoKitError.incorrectKeySize
+        }
+        return plaintext.withUnsafeBytes { plaintextBufferPtr in
+            Self._encryptOrDecrypt(mode, plaintextBufferPtr, using: key, iv: iv)
+        }
+    }
+
+    @usableFromInline
+    static func _encryptOrDecrypt(
+        _ mode: Mode,
+        _ plaintextBufferPtr: UnsafeRawBufferPointer,
+        using key: SymmetricKey,
+        iv: AES._CFB.IV
+    ) -> Data {
+        var ciphertext = Data(repeating: 0, count: plaintextBufferPtr.count)
+        ciphertext.withUnsafeMutableBytes { ciphertextBufferPtr in
+            var iv = iv
+            var num = UInt32.zero
+            key.withUnsafeBytes { keyBufferPtr in
+                iv.withUnsafeMutableBytes { ivBufferPtr in
+                    var key = AES_KEY()
+                    precondition(CCryptoBoringSSL_AES_set_encrypt_key(keyBufferPtr.baseAddress, UInt32(keyBufferPtr.count * 8), &key) == 0)
+                    CCryptoBoringSSL_AES_cfb128_encrypt(
+                        plaintextBufferPtr.baseAddress,
+                        ciphertextBufferPtr.baseAddress,
+                        plaintextBufferPtr.count,
+                        &key,
+                        ivBufferPtr.baseAddress,
+                        &num,
+                        mode._boringSSLParameter
+                    )
+                }
+            }
+        }
+        return ciphertext
+    }
+}

Tests/_CryptoExtrasTests/AES_CFBTests.swift

@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftCrypto open source project
+//
+// Copyright (c) 2024 Apple Inc. and the SwiftCrypto project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.md for the list of SwiftCrypto project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Crypto
+@testable import _CryptoExtras
+import XCTest
+
+final class AES_CFBTests: XCTestCase {
+    /// Test vectors from NIST, of the following form:
+    /// ```
+    /// COUNT = 0
+    /// KEY = 00000000000000000000000000000000
+    /// IV = f34481ec3cc627bacd5dc3fb08f273e6
+    /// PLAINTEXT = 00000000000000000000000000000000
+    /// CIPHERTEXT = 0336763e966d92595a567cc9ce537f5e
+    /// ```
+    /// —— source: https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/block-ciphers
+    struct TestVector: Codable {
+        var count: Int
+        var key: [UInt8]
+        var iv: [UInt8]
+        var plaintext: [UInt8]
+        var ciphertext: [UInt8]
+
+        enum CodingKeys: String, CodingKey {
+            case count = "COUNT"
+            case key = "KEY"
+            case iv = "IV"
+            case plaintext = "PLAINTEXT"
+            case ciphertext = "CIPHERTEXT"
+        }
+    }
+
+    func testVector(_ vector: TestVector) throws {
+        let (contiguousPlaintextData, discontiguousPlaintextData) = vector.plaintext.asDataProtocols()
+        for plaintextData in [contiguousPlaintextData as DataProtocol, discontiguousPlaintextData as DataProtocol] {
+            let key = SymmetricKey(data: Data(vector.key))
+            let iv = try AES._CFB.IV(ivBytes: vector.iv)
+            let ciphertext = try AES._CFB.encrypt(plaintextData, using: key, iv: iv)
+            XCTAssertEqual(ciphertext, Data(vector.ciphertext))
+        }
+    }
+
+    func testVectorsFrom(fileName: String) throws {
+        var decoder = try RFCVectorDecoder(bundleType: self, fileName: fileName)
+        let vectors = try decoder.decode([TestVector].self)
+        for vector in vectors {
+            try self.testVector(vector)
+        }
+    }
+
+    func testVectors() throws {
+        try self.testVectorsFrom(fileName: "AESCFB128GFSbox128")
+        try self.testVectorsFrom(fileName: "AESCFB128GFSbox128")
+        try self.testVectorsFrom(fileName: "AESCFB128GFSbox128")
+        try self.testVectorsFrom(fileName: "AESCFB128GFSbox192")
+        try self.testVectorsFrom(fileName: "AESCFB128GFSbox256")
+        try self.testVectorsFrom(fileName: "AESCFB128KeySbox128")
+        try self.testVectorsFrom(fileName: "AESCFB128KeySbox192")
+        try self.testVectorsFrom(fileName: "AESCFB128KeySbox256")
+        try self.testVectorsFrom(fileName: "AESCFB128VarKey128")
+        try self.testVectorsFrom(fileName: "AESCFB128VarKey192")
+        try self.testVectorsFrom(fileName: "AESCFB128VarKey256")
+        try self.testVectorsFrom(fileName: "AESCFB128VarTxt128")
+        try self.testVectorsFrom(fileName: "AESCFB128VarTxt192")
+        try self.testVectorsFrom(fileName: "AESCFB128VarTxt256")
+    }
+
+    func testRoundtrip() throws {
+        let key = SymmetricKey(size: .bits128)
+        let plaintext = Data(SystemRandomNumberGenerator.randomBytes(count: 1024))
+        let iv = AES._CFB.IV()
+        let ciphertext = try AES._CFB.encrypt(plaintext, using: key, iv: iv)
+        XCTAssertEqual(try AES._CFB.decrypt(ciphertext, using: key, iv: iv), plaintext)
+    }
+
+    func testRejectsInvalidIVSizes() throws {
+        let someBytes = Array(repeating: UInt8(0), count: 24)
+
+        for count in 0..<someBytes.count {
+            let ivBytes = someBytes.prefix(count)
+
+            if count != 16 {
+                XCTAssertThrowsError(try AES._CFB.IV(ivBytes: ivBytes))
+            } else {
+                XCTAssertNoThrow(try AES._CFB.IV(ivBytes: ivBytes))
+            }
+        }
+    }
+}