Author: thomasm
Date: Wed Mar 26 10:39:44 2014
New Revision: 1581782
URL: http://svn.apache.org/r1581782
Log:
OAK-1616 Password utility: prevent timing attacks
Modified:
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/security/user/util/PasswordUtil.java
Modified:
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/security/user/util/PasswordUtil.java
URL:
http://svn.apache.org/viewvc/jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/security/user/util/PasswordUtil.java?rev=1581782&r1=1581781&r2=1581782&view=diff
==============================================================================
---
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/security/user/util/PasswordUtil.java
(original)
+++
jackrabbit/oak/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/spi/security/user/util/PasswordUtil.java
Wed Mar 26 10:39:44 2014
@@ -175,7 +175,7 @@ public final class PasswordUtil {
}
String hash = generateHash(password, algorithm, salt,
iterations);
- return hashedPassword.equals(hash);
+ return compareSecure(hashedPassword, hash);
} // hashedPassword is plaintext -> return false
} catch (NoSuchAlgorithmException e) {
log.warn(e.getMessage());
@@ -184,7 +184,36 @@ public final class PasswordUtil {
}
return false;
}
-
+
+ /**
+ * Compare two strings. The comparison is constant time: it will always
loop
+ * over all characters and doesn't use conditional operations in the loop
to
+ * make sure an attacker can not use a timing attack.
+ *
+ * @param a
+ * @param b
+ * @return true if both parameters contain the same data.
+ */
+ private static boolean compareSecure(String a, String b) {
+ if ((a == null) || (b == null)) {
+ return (a == null) && (b == null);
+ }
+ int len = a.length();
+ if (len != b.length()) {
+ return false;
+ }
+ if (len == 0) {
+ return true;
+ }
+ // don't use conditional operations inside the loop
+ int bits = 0;
+ for (int i = 0; i < len; i++) {
+ // this will never reset any bits
+ bits |= a.charAt(i) ^ b.charAt(i);
+ }
+ return bits == 0;
+ }
+
//------------------------------------------------------------< private
>---
private static String generateHash(@Nonnull String pwd, @Nonnull String
algorithm,
