Reject special Windows device names in ObjectChecker

If Windows rejection is enabled reject special device names like
NUL and PRN, including NUL.txt. This prevents a tree that might
be used on a Windows client from referencing a confusing name.

Change-Id: Ic700ea8fa68724509e0357d4b758a41178c4d70c

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ObjectCheckerTest.java

@@ -1039,6 +1039,7 @@ public class ObjectCheckerTest {
 		checkOneName("a<b>c:d|e");
 		checkOneName("test ");
 		checkOneName("test.");
+		checkOneName("NUL");
 	}
 
 	@Test
@@ -1456,6 +1457,29 @@ public class ObjectCheckerTest {
 		}
 	}
 
+	@Test
+	public void testRejectDevicesOnWindows() {
+		checker.setSafeForWindows(true);
+
+		String[] bad = { "CON", "PRN", "AUX", "NUL", "COM1", "COM2", "COM3",
+				"COM4", "COM5", "COM6", "COM7", "COM8", "COM9", "LPT1", "LPT2",
+				"LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9" };
+		for (String b : bad) {
+			try {
+				checkOneName(b);
+				fail("incorrectly accepted " + b);
+			} catch (CorruptObjectException e) {
+				assertEquals("invalid name '" + b + "'", e.getMessage());
+			}
+			try {
+				checkOneName(b + ".txt");
+				fail("incorrectly accepted " + b + ".txt");
+			} catch (CorruptObjectException e) {
+				assertEquals("invalid name '" + b + "'", e.getMessage());
+			}
+		}
+	}
+
 	@Test
 	public void testRejectInvalidWindowsCharacters() {
 		checker.setSafeForWindows(true);

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectChecker.java

@@ -410,10 +410,68 @@ public class ObjectChecker {
 			}
 		}
 
+		if (windows) {
 			// Windows ignores space and dot at end of file name.
-		if (windows && (raw[end - 1] == ' ' || raw[end - 1] == '.'))
+			if (raw[end - 1] == ' ' || raw[end - 1] == '.')
 				throw new CorruptObjectException("invalid name ends with '"
 						+ ((char) raw[end - 1]) + "'");
+			if (end - ptr >= 3)
+				checkNotWindowsDevice(raw, ptr, end);
+		}
+	}
+
+	private static void checkNotWindowsDevice(byte[] raw, int ptr, int end)
+			throws CorruptObjectException {
+		switch (toLower(raw[ptr])) {
+		case 'a': // AUX
+			if (end - ptr >= 3
+					&& toLower(raw[ptr + 1]) == 'u'
+					&& toLower(raw[ptr + 2]) == 'x'
+					&& (end - ptr == 3 || raw[ptr + 3] == '.'))
+				throw new CorruptObjectException("invalid name 'AUX'");
+			break;
+
+		case 'c': // CON, COM[1-9]
+			if (end - ptr >= 3
+					&& toLower(raw[ptr + 2]) == 'n'
+					&& toLower(raw[ptr + 1]) == 'o'
+					&& (end - ptr == 3 || raw[ptr + 3] == '.'))
+				throw new CorruptObjectException("invalid name 'CON'");
+			if (end - ptr >= 4
+					&& toLower(raw[ptr + 2]) == 'm'
+					&& toLower(raw[ptr + 1]) == 'o'
+					&& isPositiveDigit(raw[ptr + 3])
+					&& (end - ptr == 4 || raw[ptr + 4] == '.'))
+				throw new CorruptObjectException("invalid name 'COM"
+						+ ((char) raw[ptr + 3]) + "'");
+			break;
+
+		case 'l': // LPT[1-9]
+			if (end - ptr >= 4
+					&& toLower(raw[ptr + 1]) == 'p'
+					&& toLower(raw[ptr + 2]) == 't'
+					&& isPositiveDigit(raw[ptr + 3])
+					&& (end - ptr == 4 || raw[ptr + 4] == '.'))
+				throw new CorruptObjectException("invalid name 'LPT"
+						+ ((char) raw[ptr + 3]) + "'");
+			break;
+
+		case 'n': // NUL
+			if (end - ptr >= 3
+					&& toLower(raw[ptr + 1]) == 'u'
+					&& toLower(raw[ptr + 2]) == 'l'
+					&& (end - ptr == 3 || raw[ptr + 3] == '.'))
+				throw new CorruptObjectException("invalid name 'NUL'");
+			break;
+
+		case 'p': // PRN
+			if (end - ptr >= 3
+					&& toLower(raw[ptr + 1]) == 'r'
+					&& toLower(raw[ptr + 2]) == 'n'
+					&& (end - ptr == 3 || raw[ptr + 3] == '.'))
+				throw new CorruptObjectException("invalid name 'PRN'");
+			break;
+		}
 	}
 
 	private static boolean isInvalidOnWindows(byte c) {
@@ -446,6 +504,10 @@ public class ObjectChecker {
 		return (char) b;
 	}
 
+	private static boolean isPositiveDigit(byte b) {
+		return '1' <= b && b <= '9';
+	}
+
 	/**
 	 * Check a blob for errors.
 	 *