Return EOF when reading past the end of a memory archive

Sources/ZIPFoundation/Archive+MemoryFile.swift

@@ -57,6 +57,7 @@ public enum MemoryFileError: Error {
 private extension Archive.MemoryFile {
 
     func readData(buffer: UnsafeMutableRawBufferPointer) -> Int {
+        guard self.offset < self.data.count else { return 0 }
         let size = min(buffer.count, data.count-offset)
         let start = data.startIndex
         self.data.copyBytes(to: buffer.bindMemory(to: UInt8.self), from: start+offset..<start+offset+size)

Tests/ZIPFoundationTests/ZIPFoundationMemoryTests.swift

@@ -160,6 +160,46 @@ extension ZIPFoundationTests {
         XCTAssertEqual(String(Unicode.Scalar(chars[1])), "B")
     }
 
+    func testReadPastEndOfMemoryFile() throws {
+        let originalData = Data("01234ABCDE".utf8)
+        let inputs = [Data(), Data("ABCDE".utf8), originalData[5..<originalData.count]]
+        for data in inputs {
+            let file = try Archive.MemoryFile(data: data).open(mode: .read)
+            defer { fclose(file) }
+            var buffer = [UInt8](repeating: 0, count: 3)
+            for offset in [data.count, data.count + 1, Int(Int32.max)] {
+                XCTAssertEqual(fseek(file, offset, SEEK_SET), 0)
+                XCTAssertEqual(fread(&buffer, 1, buffer.count, file), 0)
+                XCTAssertNotEqual(feof(file), 0)
+                XCTAssertEqual(ferror(file), 0)
+                XCTAssertEqual(ftell(file), offset)
+            }
+            // Reading past EOF must not prevent seeking back to valid data.
+            XCTAssertEqual(fseek(file, 0, SEEK_SET), 0)
+            XCTAssertEqual(feof(file), 0)
+            let count = fread(&buffer, 1, buffer.count, file)
+            XCTAssertEqual(count, min(data.count, buffer.count))
+            XCTAssertEqual(Array(buffer.prefix(count)), Array(data.prefix(buffer.count)))
+        }
+    }
+
+    func testMemoryArchiveWithLocalHeaderBeyondEOF() throws {
+        let archive = try Archive(accessMode: .create)
+        let contents = Data("test".utf8)
+        try archive.addEntry(with: "test.txt", type: .file,
+                             uncompressedSize: Int64(contents.count)) { position, size in
+            contents.subdata(in: Int(position)..<(Int(position) + size))
+        }
+        var data = try XCTUnwrap(archive.data)
+        let signature = Data([0x50, 0x4b, 0x01, 0x02])
+        let directoryOffset = try XCTUnwrap(data.range(of: signature)?.lowerBound)
+        // Point the local file header beyond the end of the archive.
+        data.replaceSubrange((directoryOffset + 42)..<(directoryOffset + 46),
+                             with: [0xff, 0xff, 0xff, 0x7f])
+        let reader = try Archive(data: data, accessMode: .read)
+        XCTAssertNil(reader.makeIterator().next())
+    }
+
     func testWriteOnlyFile() throws {
         let mem = Archive.MemoryFile()
         let file = try mem.open(mode: .create)

Tests/ZIPFoundationTests/ZIPFoundationTests.swift

@@ -134,7 +134,6 @@ class ZIPFoundationTests: XCTestCase {
         let originalGID = getgid()
         defer { setgid(originalGID) }
         guard let user = getpwnam("nobody") else { return }
-
         let gid = user.pointee.pw_gid
         guard 0 == setgid(gid) else { return }
     }
@@ -346,6 +345,8 @@ extension ZIPFoundationTests {
             ("testMemoryArchiveErrorConditions", testMemoryArchiveErrorConditions),
             ("testWriteOnlyFile", testWriteOnlyFile),
             ("testReadOnlyFile", testReadOnlyFile),
+            ("testReadPastEndOfMemoryFile", testReadPastEndOfMemoryFile),
+            ("testMemoryArchiveWithLocalHeaderBeyondEOF", testMemoryArchiveWithLocalHeaderBeyondEOF),
             ("testReadOnlySlicedFile", testReadOnlySlicedFile),
             ("testReadWriteFile", testReadWriteFile)
         ]
@@ -382,7 +383,6 @@ extension Data {
 
 #if os(macOS)
 extension NSUserScriptTask {
-
     static func makeVolumeCreationTask(at tempDir: URL, volumeName: String) throws -> NSUserScriptTask {
         let scriptURL = tempDir.appendingPathComponent("createVol.sh", isDirectory: false)
         let dmgURL = tempDir.appendingPathComponent(volumeName).appendingPathExtension("dmg")