Clarify endianness in integer byte accessor

Bouke · Dec 31, 2022 · 8262d98 · 8262d98
1 parent 475fd1e
commit 8262d98
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Showing 4 changed files with 48 additions and 32 deletions.
diff --git a/Sources/HAP/Security/Cryptographer.swift b/Sources/HAP/Security/Cryptographer.swift
@@ -44,7 +44,7 @@ class Cryptographer {
                                                                     tag: T) throws -> Data {
         defer { decryptCount += 1 }
 
-        let nonce = try ChaChaPoly.Nonce(data: Data(count: 4) + decryptCount.bigEndian.bytes)
+        let nonce = try ChaChaPoly.Nonce(data: Data(count: 4) + decryptCount.littleEndianBytes)
         let box = try ChaChaPoly.SealedBox(nonce: nonce, ciphertext: ciphertext, tag: tag)
 
         return try ChaChaPoly.open(box, using: decryptKey, authenticating: lengthBytes)
@@ -53,8 +53,8 @@ class Cryptographer {
     func encrypt(plaintext: ByteBuffer) throws -> Data {
         defer { encryptCount += 1 }
 
-        let nonce = try ChaChaPoly.Nonce(data: Data(count: 4) + encryptCount.bigEndian.bytes)
-        let authenticationData = UInt16(plaintext.readableBytes).bigEndian.bytes
+        let nonce = try ChaChaPoly.Nonce(data: Data(count: 4) + encryptCount.littleEndianBytes)
+        let authenticationData = UInt16(plaintext.readableBytes).littleEndianBytes
 
         let box = try ChaChaPoly.seal(plaintext.readableBytesView,
                                       using: encryptKey,

diff --git a/Sources/HAP/Utils/FixedWidthInteger+Extensions.swift b/Sources/HAP/Utils/FixedWidthInteger+Extensions.swift
@@ -0,0 +1,13 @@
+import Foundation
+
+extension FixedWidthInteger {
+	/// Returns bytes in Big Endian or Network Byte Ordering.
+	public var bigEndianBytes: Data {
+		withUnsafeBytes(of: bigEndian, { Data(bytes: $0.baseAddress!, count: $0.count) })
+	}
+
+	/// Returns bytes in Little Endian.
+	public var littleEndianBytes: Data {
+		withUnsafeBytes(of: littleEndian, { Data(bytes: $0.baseAddress!, count: $0.count) })
+	}
+}
diff --git a/Sources/HAP/Utils/Integer+Data.swift b/Sources/HAP/Utils/Integer+Data.swift
diff --git a/Tests/HAPTests/FixedWithInteger+ExtensionsTests.swift b/Tests/HAPTests/FixedWithInteger+ExtensionsTests.swift
@@ -0,0 +1,32 @@
+@testable import HAP
+import XCTest
+
+final class FixedWidthIntegerExtensionTests: XCTestCase {
+    func testBigEndianBytes() throws {
+		XCTAssertEqual(UInt8(1).bigEndianBytes, Data([1]))
+		XCTAssertEqual(UInt16(1).bigEndianBytes, Data([0, 1]))
+		XCTAssertEqual(UInt32(1).bigEndianBytes, Data([0, 0, 0, 1]))
+		XCTAssertEqual(UInt64(1).bigEndianBytes, Data([0, 0, 0, 0, 0, 0, 0, 1]))
+		XCTAssertEqual(UInt16(1 << 8).bigEndianBytes, Data([1, 0]))
+		XCTAssertEqual(UInt32(1 << 24).bigEndianBytes, Data([1, 0, 0, 0]))
+		XCTAssertEqual(UInt64(1 << 56).bigEndianBytes, Data([1, 0, 0, 0, 0, 0, 0, 0]))
+    }
+
+	func testLittleEndianBytes() throws {
+		XCTAssertEqual(UInt8(1).littleEndianBytes, Data([1]))
+		XCTAssertEqual(UInt16(1).littleEndianBytes, Data([1, 0]))
+		XCTAssertEqual(UInt32(1).littleEndianBytes, Data([1, 0, 0, 0]))
+		XCTAssertEqual(UInt64(1).littleEndianBytes, Data([1, 0, 0, 0, 0, 0, 0, 0]))
+		XCTAssertEqual(UInt16(1 << 8).littleEndianBytes, Data([0, 1]))
+		XCTAssertEqual(UInt32(1 << 24).littleEndianBytes, Data([0, 0, 0, 1]))
+		XCTAssertEqual(UInt64(1 << 56).littleEndianBytes, Data([0, 0, 0, 0, 0, 0, 0, 1]))
+	}
+
+	func testBE() throws {
+		try XCTSkipUnless(UInt(16) == UInt(16).bigEndian, "Platform is LE")
+	}
+
+	func testLE() throws {
+		try XCTSkipIf(UInt(16) == UInt(16).bigEndian, "Platform is BE")
+	}
+}