From c3a914318356d7b82ab6a8a1d0c658d3e2b62928 Mon Sep 17 00:00:00 2001
From: Luiz Rodrigo Martins Barbosa <luiz@developercity.de>
Date: Fri, 8 Oct 2021 10:13:47 +0200
Subject: [PATCH] Fix unsafe Data Range when extracting subdata (#27)

---
 .../Data/Data+Extensions.swift                |  4 +-
 .../Data/DataExtensionsTests.swift            | 38 +++++++++++++++++++
 .../{ => Data}/DataMD5Tests.swift             |  0
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 Tests/FoundationExtensionsTests/Data/DataExtensionsTests.swift
 rename Tests/FoundationExtensionsTests/{ => Data}/DataMD5Tests.swift (100%)

diff --git a/Sources/FoundationExtensions/Data/Data+Extensions.swift b/Sources/FoundationExtensions/Data/Data+Extensions.swift
index f9c0f7f..433ea7f 100644
--- a/Sources/FoundationExtensions/Data/Data+Extensions.swift
+++ b/Sources/FoundationExtensions/Data/Data+Extensions.swift
@@ -34,7 +34,9 @@ extension Numeric {
 extension Data {
 
     public func range(start: Int, length: Int) -> Data {
-        subdata(in: start..<start + length)
+        guard start < endIndex else { return Data() }
+        let end = Swift.min(endIndex, start + length)
+        return subdata(in: start ..< end)
     }
 
     public func readValue<T>() -> T {
diff --git a/Tests/FoundationExtensionsTests/Data/DataExtensionsTests.swift b/Tests/FoundationExtensionsTests/Data/DataExtensionsTests.swift
new file mode 100644
index 0000000..4646f90
--- /dev/null
+++ b/Tests/FoundationExtensionsTests/Data/DataExtensionsTests.swift
@@ -0,0 +1,38 @@
+// Copyright © 2021 Lautsprecher Teufel GmbH. All rights reserved.
+
+#if !os(watchOS)
+import FoundationExtensions
+import XCTest
+
+class DataExtensionsTests: XCTestCase {
+    func testDataInRangeSuccessfullyExtractSubdataInTheMiddle() {
+        let fullData = Data([0xDE, 0xAD, 0xBE, 0xFF])
+        let partialData = fullData.range(start: 1, length: 1)
+        XCTAssertEqual(partialData, Data([0xAD]))
+    }
+
+    func testDataInRangeSuccessfullyExtractSubdataAtTheEnd() {
+        let fullData = Data([0xDE, 0xAD, 0xBE, 0xFF])
+        let partialData = fullData.range(start: 3, length: 1)
+        XCTAssertEqual(partialData, Data([0xFF]))
+    }
+
+    func testDataOutOfRangeBecauseOfLengthABitTooLong() {
+        let fullData = Data([0xDE, 0xAD, 0xBE, 0xFF])
+        let partialData = fullData.range(start: 3, length: 2)
+        XCTAssertEqual(partialData, Data([0xFF]))
+    }
+
+    func testDataOutOfRangeBecauseOfLengthWayTooLong() {
+        let fullData = Data([0xDE, 0xAD, 0xBE, 0xFF])
+        let partialData = fullData.range(start: 1, length: 10)
+        XCTAssertEqual(partialData, Data([0xAD, 0xBE, 0xFF]))
+    }
+
+    func testDataOutOfRangeBecauseOfStart() {
+        let fullData = Data([0xDE, 0xAD, 0xBE, 0xFF])
+        let partialData = fullData.range(start: 4, length: 1)
+        XCTAssertEqual(partialData, Data([]))
+    }
+}
+#endif
diff --git a/Tests/FoundationExtensionsTests/DataMD5Tests.swift b/Tests/FoundationExtensionsTests/Data/DataMD5Tests.swift
similarity index 100%
rename from Tests/FoundationExtensionsTests/DataMD5Tests.swift
rename to Tests/FoundationExtensionsTests/Data/DataMD5Tests.swift