Delete password from memory in AuthenticationManager

Zero out the password to remove it from memory after use.
This is only a first step, implementing it for one method:
`AuthenticationManager.authenticate(String, char[], String)`.

src/main/java/com/gitblit/manager/AuthenticationManager.java

@@ -452,7 +452,6 @@ public class AuthenticationManager implements IAuthenticationManager {
 	/**
 	 * Authenticate a user based on a username and password.
 	 *
-	 * @see IUserService.authenticate(String, char[])
 	 * @param username
 	 * @param password
 	 * @return a user object or null
@@ -471,34 +470,39 @@ public class AuthenticationManager implements IAuthenticationManager {
 		}
 		
 		String usernameDecoded = StringUtils.decodeUsername(username);
-		String pw = new String(password);
-		if (StringUtils.isEmpty(pw)) {
+		if (StringUtils.isEmpty(password)) {
 			// can not authenticate empty password
 			return null;
 		}
 
 		UserModel user = userManager.getUserModel(usernameDecoded);
 
-		// try local authentication
-		if (user != null && user.isLocalAccount()) {
-			UserModel returnedUser = authenticateLocal(user, password);
-			if (returnedUser != null) {
-				// user authenticated
-				return returnedUser;
-			}
-		} else {
-			// try registered external authentication providers
-			for (AuthenticationProvider provider : authenticationProviders) {
-				if (provider instanceof UsernamePasswordAuthenticationProvider) {
-					UserModel returnedUser = provider.authenticate(usernameDecoded, password);
-					if (returnedUser != null) {
-						// user authenticated
-						returnedUser.accountType = provider.getAccountType();
-						return validateAuthentication(returnedUser, AuthenticationType.CREDENTIALS);
+		try {
+			// try local authentication
+			if (user != null && user.isLocalAccount()) {
+				UserModel returnedUser = authenticateLocal(user, password);
+				if (returnedUser != null) {
+					// user authenticated
+					return returnedUser;
+				}
+			} else {
+				// try registered external authentication providers
+				for (AuthenticationProvider provider : authenticationProviders) {
+					if (provider instanceof UsernamePasswordAuthenticationProvider) {
+						UserModel returnedUser = provider.authenticate(usernameDecoded, password);
+						if (returnedUser != null) {
+							// user authenticated
+							returnedUser.accountType = provider.getAccountType();
+							return validateAuthentication(returnedUser, AuthenticationType.CREDENTIALS);
+						}
 					}
 				}
 			}
 		}
+		finally {
+			// Zero out password array to delete password from memory
+			Arrays.fill(password, Character.MIN_VALUE);
+		}
 
 		// could not authenticate locally or with a provider
 		logger.warn(MessageFormat.format("Failed login attempt for {0}, invalid credentials from {1}", username, 

src/main/java/com/gitblit/utils/StringUtils.java

@@ -56,6 +56,21 @@ public class StringUtils {
 		return value == null || value.trim().length() == 0;
 	}
 
+	/**
+	 * Returns true if the character array represents an empty String.
+	 * An empty character sequence is defined as a sequence that
+	 * either has no characters at all, or no characters above
+	 * '\u0020' (space).
+	 *
+	 * @param value
+	 * @return true if value is null or represents an empty String
+	 */
+	public static boolean isEmpty(char[] value) {
+		if (value == null || value.length == 0) return true;
+		for ( char c : value) if (c > '\u0020') return false;
+		return true;
+	}
+
 	/**
 	 * Replaces carriage returns and line feeds with html line breaks.
 	 *

src/test/java/com/gitblit/tests/AuthenticationManagerTest.java

@@ -19,13 +19,7 @@ import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.security.Principal;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Enumeration;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
+import java.util.*;
 
 import javax.servlet.AsyncContext;
 import javax.servlet.DispatcherType;
@@ -654,16 +648,84 @@ public class AuthenticationManagerTest extends GitblitUnitTest {
 	public void testAuthenticate() throws Exception {
 		IAuthenticationManager auth = newAuthenticationManager();
 
+
+		String password = "pass word";
 		UserModel user = new UserModel("sunnyjim");
-		user.password = "password";
+		user.password = password;
 		users.updateUserModel(user);
 
-		assertNotNull(auth.authenticate(user.username, user.password.toCharArray(), null));
+		char[] pwd = password.toCharArray();
+		assertNotNull(auth.authenticate(user.username, pwd, null));
+
+		// validate that the passed in password has been zeroed out in memory
+		char[] zeroes = new char[pwd.length];
+		Arrays.fill(zeroes, Character.MIN_VALUE);
+		assertArrayEquals(zeroes, pwd);
+	}
+
+
+	@Test
+	public void testAuthenticateDisabledUser() throws Exception {
+		IAuthenticationManager auth = newAuthenticationManager();
+
+
+		String password = "password";
+		UserModel user = new UserModel("sunnyjim");
+		user.password = password;
 		user.disabled = true;
+		users.updateUserModel(user);
+
+		assertNull(auth.authenticate(user.username, password.toCharArray(), null));
+
+		user.disabled = false;
+		users.updateUserModel(user);
+		assertNotNull(auth.authenticate(user.username, password.toCharArray(), null));
+	}
+
+
+	@Test
+	public void testAuthenticateEmptyPassword() throws Exception {
+		IAuthenticationManager auth = newAuthenticationManager();
+
+
+		String password = "password";
+		UserModel user = new UserModel("sunnyjim");
+		user.password = password;
+		users.updateUserModel(user);
+
+		assertNull(auth.authenticate(user.username, "".toCharArray(), null));
+		assertNull(auth.authenticate(user.username, " 	 ".toCharArray(), null));
+		assertNull(auth.authenticate(user.username, new char[]{' ', '\u0010', '\u0015'}, null));
+	}
+
+
+
 
+	@Test
+	public void testAuthenticateWrongPassword() throws Exception {
+		IAuthenticationManager auth = newAuthenticationManager();
+
+
+		String password = "password";
+		UserModel user = new UserModel("sunnyjim");
+		user.password = password;
 		users.updateUserModel(user);
-		assertNull(auth.authenticate(user.username, user.password.toCharArray(), null));
-		users.deleteUserModel(user);
+
+		assertNull(auth.authenticate(user.username, "helloworld".toCharArray(), null));
+	}
+
+
+	@Test
+	public void testAuthenticateNoSuchUser() throws Exception {
+		IAuthenticationManager auth = newAuthenticationManager();
+
+
+		String password = "password";
+		UserModel user = new UserModel("sunnyjim");
+		user.password = password;
+		users.updateUserModel(user);
+
+		assertNull(auth.authenticate("rainyjoe", password.toCharArray(), null));
 	}
 
 

src/test/java/com/gitblit/tests/StringUtilsTest.java

@@ -26,12 +26,25 @@ public class StringUtilsTest extends GitblitUnitTest {
 
 	@Test
 	public void testIsEmpty() throws Exception {
-		assertTrue(StringUtils.isEmpty(null));
+		assertTrue(StringUtils.isEmpty((String)null));
 		assertTrue(StringUtils.isEmpty(""));
 		assertTrue(StringUtils.isEmpty("  "));
 		assertFalse(StringUtils.isEmpty("A"));
 	}
 
+	@Test
+	public void testIsEmptyCharArray() throws Exception {
+		assertTrue(StringUtils.isEmpty((char[])null));
+		assertTrue(StringUtils.isEmpty(new char[0]));
+		assertTrue(StringUtils.isEmpty(new char[]{ ' ' }));
+		assertTrue(StringUtils.isEmpty(new char[]{ '	'}));
+		assertTrue(StringUtils.isEmpty(new char[]{ ' ', ' ' }));
+		assertTrue(StringUtils.isEmpty(new char[]{ '	',  ' ', '	' }));
+		assertFalse(StringUtils.isEmpty(new char[]{ '\u0020', 'f' }));
+		assertFalse(StringUtils.isEmpty(new char[]{ '\u0148', '\u0020' }));
+		assertFalse(StringUtils.isEmpty(new char[]{ 'A' }));
+	}
+
 	@Test
 	public void testBreakLinesForHtml() throws Exception {
 		String input = "this\nis\r\na\rtest\r\n\r\nof\n\nline\r\rbreaking";