SEC-1666: Use constant time comparison for sensitive data.

Constant time comparison helps to mitigate timing attacks. See the following link for more information

 * http://rdist.root.org/2010/07/19/exploiting-remote-timing-attacks/
 * http://en.wikipedia.org/wiki/Timing_attack for more information.

core/src/main/java/org/springframework/security/authentication/encoding/LdapShaPasswordEncoder.java

@@ -145,7 +145,7 @@ public class LdapShaPasswordEncoder implements PasswordEncoder {
 
         String encodedRawPass = encodePassword(rawPass, salt).substring(startOfHash);
 
-        return encodedRawPass.equals(encPass.substring(startOfHash));
+        return PasswordEncoderUtils.equals(encodedRawPass,encPass.substring(startOfHash));
     }
 
     /**

core/src/main/java/org/springframework/security/authentication/encoding/Md4PasswordEncoder.java

@@ -78,7 +78,7 @@ public class Md4PasswordEncoder extends BaseDigestPasswordEncoder {
     public boolean isPasswordValid(String encPass, String rawPass, Object salt) {
         String pass1 = "" + encPass;
         String pass2 = encodePassword(rawPass, salt);
-        return pass1.equals(pass2);
+        return PasswordEncoderUtils.equals(pass1,pass2);
     }
 
     public String getAlgorithm() {

core/src/main/java/org/springframework/security/authentication/encoding/MessageDigestPasswordEncoder.java

@@ -126,7 +126,7 @@ public class MessageDigestPasswordEncoder extends BaseDigestPasswordEncoder {
         String pass1 = "" + encPass;
         String pass2 = encodePassword(rawPass, salt);
 
-        return pass1.equals(pass2);
+        return PasswordEncoderUtils.equals(pass1,pass2);
     }
 
     public String getAlgorithm() {

core/src/main/java/org/springframework/security/authentication/encoding/PasswordEncoderUtils.java

@@ -0,0 +1,45 @@
+package org.springframework.security.authentication.encoding;
+
+import java.io.UnsupportedEncodingException;
+
+/**
+ * Utility for constant time comparison to prevent against timing attacks.
+ *
+ * @author Rob Winch
+ */
+class PasswordEncoderUtils {
+
+    /**
+     * Constant time comparison to prevent against timing attacks.
+     * @param expected
+     * @param actual
+     * @return
+     */
+    static boolean equals(String expected, String actual) {
+        byte[] expectedBytes = bytesUtf8(expected);
+        byte[] actualBytes = bytesUtf8(actual);
+        int expectedLength = expectedBytes == null ? -1 : expectedBytes.length;
+        int actualLength = actualBytes == null ? -1 : actualBytes.length;
+        if (expectedLength != actualLength) {
+            return false;
+        }
+
+        int result = 0;
+        for (int i = 0; i < expectedLength; i++) {
+            result |= expectedBytes[i] ^ actualBytes[i];
+        }
+        return result == 0;
+    }
+
+    private static byte[] bytesUtf8(String s) {
+        if(s == null) {
+            return null;
+        }
+        try {
+            return s.getBytes("UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            throw new IllegalStateException("Could not get bytes in UTF-8 format",e);
+        }
+    }
+    private PasswordEncoderUtils() {}
+}

core/src/main/java/org/springframework/security/authentication/encoding/PlaintextPasswordEncoder.java

@@ -15,6 +15,8 @@
 
 package org.springframework.security.authentication.encoding;
 
+import java.util.Locale;
+
 /**
  * <p>Plaintext implementation of PasswordEncoder.</p>
  *  <P>As callers may wish to extract the password and salts separately from the encoded password, the salt must
@@ -46,11 +48,12 @@ public class PlaintextPasswordEncoder extends BasePasswordEncoder {
         // authentication will fail as the encodePassword never allows them)
         String pass2 = mergePasswordAndSalt(rawPass, salt, false);
 
-        if (!ignorePasswordCase) {
-            return pass1.equals(pass2);
-        } else {
-            return pass1.equalsIgnoreCase(pass2);
+        if (ignorePasswordCase) {
+            // Note: per String javadoc to get correct results for Locale insensitive, use English
+            pass1 = pass1.toLowerCase(Locale.ENGLISH);
+            pass2 = pass2.toLowerCase(Locale.ENGLISH);
         }
+        return PasswordEncoderUtils.equals(pass1,pass2);
     }
 
     /**

core/src/test/java/org/springframework/security/authentication/encoding/PasswordEncoderUtilsTests.java

@@ -0,0 +1,33 @@
+package org.springframework.security.authentication.encoding;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+/**
+ * @author Rob Winch
+ */
+public class PasswordEncoderUtilsTests {
+
+    @Test
+    public void differentLength() {
+        assertFalse(PasswordEncoderUtils.equals("abc", "a"));
+        assertFalse(PasswordEncoderUtils.equals("a", "abc"));
+    }
+
+    @Test
+    public void equalsNull() {
+        assertFalse(PasswordEncoderUtils.equals(null, "a"));
+        assertFalse(PasswordEncoderUtils.equals("a", null));
+        assertTrue(PasswordEncoderUtils.equals(null, null));
+    }
+
+    @Test
+    public void equalsCaseSensitive() {
+        assertFalse(PasswordEncoderUtils.equals("aBc", "abc"));
+    }
+
+    @Test
+    public void equalsSuccess() {
+        assertTrue(PasswordEncoderUtils.equals("abcdef", "abcdef"));
+    }
+}

crypto/src/main/java/org/springframework/security/crypto/password/StandardPasswordEncoder.java

@@ -21,8 +21,6 @@ import static org.springframework.security.crypto.util.EncodingUtils.hexEncode;
 import static org.springframework.security.crypto.util.EncodingUtils.subArray;
 import static org.springframework.security.crypto.util.EncodingUtils.utf8Encode;
 
-import java.util.Arrays;
-
 import org.springframework.security.crypto.keygen.BytesKeyGenerator;
 import org.springframework.security.crypto.keygen.KeyGenerators;
 import org.springframework.security.crypto.util.Digester;
@@ -79,8 +77,21 @@ public final class StandardPasswordEncoder implements PasswordEncoder {
         return hexDecode(encodedPassword);
     }
 
+    /**
+     * Constant time comparison to prevent against timing attacks.
+     * @param expected
+     * @param actual
+     * @return
+     */
     private boolean matches(byte[] expected, byte[] actual) {
-        return Arrays.equals(expected, actual);
-    }
+        if (expected.length != actual.length) {
+            return false;
+        }
 
+        int result = 0;
+        for (int i = 0; i < expected.length; i++) {
+            result |= expected[i] ^ actual[i];
+        }
+        return result == 0;
+    }
 }

crypto/src/test/java/org/springframework/security/crypto/password/StandardPasswordEncoderTests.java

@@ -16,6 +16,12 @@ public class StandardPasswordEncoderTests {
         assertTrue(encoder.matches("password", result));
     }
 
+    @Test
+    public void matchesLengthChecked() {
+        String result = encoder.encode("password");
+        assertFalse(encoder.matches("password", result.substring(0,result.length()-1)));
+    }
+
     @Test
     public void notMatches() {
         String result = encoder.encode("password");

web/src/main/java/org/springframework/security/web/authentication/rememberme/TokenBasedRememberMeServices.java

@@ -23,6 +23,7 @@ import org.springframework.util.StringUtils;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import java.io.UnsupportedEncodingException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
@@ -81,6 +82,7 @@ public class TokenBasedRememberMeServices extends AbstractRememberMeServices {
 
     //~ Methods ========================================================================================================
 
+    @Override
     protected UserDetails processAutoLoginCookie(String[] cookieTokens, HttpServletRequest request,
             HttpServletResponse response) {
 
@@ -117,9 +119,9 @@ public class TokenBasedRememberMeServices extends AbstractRememberMeServices {
         String expectedTokenSignature = makeTokenSignature(tokenExpiryTime, userDetails.getUsername(),
                 userDetails.getPassword());
 
-        if (!expectedTokenSignature.equals(cookieTokens[2])) {
+        if (!equals(expectedTokenSignature,cookieTokens[2])) {
             throw new InvalidCookieException("Cookie token[2] contained signature '" + cookieTokens[2]
-                    + "' but expected '" + expectedTokenSignature + "'");
+                                                                                                    + "' but expected '" + expectedTokenSignature + "'");
         }
 
         return userDetails;
@@ -145,6 +147,7 @@ public class TokenBasedRememberMeServices extends AbstractRememberMeServices {
         return tokenExpiryTime < System.currentTimeMillis();
     }
 
+    @Override
     public void onLoginSuccess(HttpServletRequest request, HttpServletResponse response,
             Authentication successfulAuthentication) {
 
@@ -216,4 +219,35 @@ public class TokenBasedRememberMeServices extends AbstractRememberMeServices {
     private boolean isInstanceOfUserDetails(Authentication authentication) {
         return authentication.getPrincipal() instanceof UserDetails;
     }
+
+    /**
+     * Constant time comparison to prevent against timing attacks.
+     * @param expected
+     * @param actual
+     * @return
+     */
+    private static boolean equals(String expected, String actual) {
+        byte[] expectedBytes = bytesUtf8(expected);
+        byte[] actualBytes = bytesUtf8(actual);
+        if (expectedBytes.length != actualBytes.length) {
+            return false;
+        }
+
+        int result = 0;
+        for (int i = 0; i < expectedBytes.length; i++) {
+            result |= expectedBytes[i] ^ actualBytes[i];
+        }
+        return result == 0;
+    }
+
+    private static byte[] bytesUtf8(String s) {
+        if(s == null) {
+            return null;
+        }
+        try {
+            return s.getBytes("UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            throw new IllegalStateException("Could not get bytes in UTF-8 format",e);
+        }
+    }
 }