Improve signature validation

server/src/main/java/org/cloudfoundry/identity/uaa/oauth/jwt/UaaMacSigner.java

@@ -18,6 +18,7 @@
 import javax.crypto.SecretKey;
 import javax.crypto.spec.SecretKeySpec;
 import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
 import java.text.ParseException;
 import java.util.Collections;
 import java.util.LinkedHashSet;
@@ -84,11 +85,14 @@ public static JWTClaimsSet verify(String jwToken, JWKSet jwkSet) {
             String kid = header.getKeyID();
             JWK jwKey = jwkSet.getKeys().stream().filter(e -> kid.equals(e.getKeyID())).findFirst().orElseThrow();
             UaaMacSigner internal = new UaaMacSigner((String) jwKey.toJSONObject().get(JWKParameterNames.OCT_KEY_VALUE));
-            // symmetric signature check: create internal signature and compare if matches the signature from token
-            if (token.getSignature().equals(internal.sign(header, token.getSigningInput())) && SUPPORTED_ALGORITHMS.contains(header.getAlgorithm())) {
-                return token.getJWTClaimsSet();
+            // symmetric signature check: create internal signature and compare if matches the signature from token, using a constant-time comparison
+            if (SUPPORTED_ALGORITHMS.contains(header.getAlgorithm())) {
+                Base64URL expectedSignature = internal.sign(header, token.getSigningInput());
+                if (MessageDigest.isEqual(token.getSignature().decode(), expectedSignature.decode())) {
+                    return token.getJWTClaimsSet();
+                }
             }
-            throw new InvalidSignatureException("HMAC not mached");
+            throw new InvalidSignatureException("HMAC not matched");
         } catch (ParseException | JOSEException e) {
             throw new InvalidSignatureException("Invalid signed token", e);
         }

server/src/main/java/org/cloudfoundry/identity/uaa/provider/ldap/PasswordComparisonAuthenticator.java

@@ -34,7 +34,7 @@
 import javax.naming.NamingException;
 import javax.naming.directory.Attribute;
 import javax.naming.directory.Attributes;
-import java.util.Arrays;
+import java.security.MessageDigest;
 import java.util.function.Supplier;
 
 /**
@@ -117,7 +117,7 @@ public DirContextOperations localCompareAuthenticate(DirContextOperations user,
                     } else {
                         String encodedPassword = passwordEncoder.encode(password);
                         byte[] passwordBytes = Utf8.encode(encodedPassword);
-                        match = Arrays.equals(passwordBytes, valBytes);
+                        match = MessageDigest.isEqual(passwordBytes, valBytes);
                     }
                 }
             }

server/src/main/java/org/cloudfoundry/identity/uaa/provider/oauth/ExternalOAuthAuthenticationManager.java

@@ -98,6 +98,7 @@
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -658,13 +659,20 @@ protected <T extends AbstractExternalOAuthIdentityProviderDefinition<T>> Map<Str
                 final var algorithm = Optional.ofNullable(jsonData)
                         .map(it -> it.get("algorithm"))
                         .orElse(null);
-                if (algorithm != null && !"HMAC-SHA256".equals(algorithm)) {
-                    log.debug("Unknown algorithm was used to sign request! No claims returned.");
+                if (!"HMAC-SHA256".equals(algorithm)) {
+                    log.debug("Missing or unknown algorithm was used to sign request! No claims returned.");
                     return null;
                 }
-                //check if data is signed correctly
-                if (!hmacSignAndEncode(signedRequests[1], secret).equals(signature)) {
-                    log.debug("Signature is not correct, possibly the data was tampered with! No claims returned.");
+                // check if data is signed correctly using constant-time comparison
+                try {
+                    byte[] expectedMac = Base64.decodeBase64(hmacSignAndEncode(signedRequests[1], secret));
+                    byte[] suppliedMac = Base64.decodeBase64(signature);
+                    if (!MessageDigest.isEqual(expectedMac, suppliedMac)) {
+                        log.debug("Signature is not correct, possibly the data was tampered with! No claims returned.");
+                        return null;
+                    }
+                } catch (Exception _) {
+                    log.debug("Failed to validate signature due to encoding or computation error! No claims returned.");
                     return null;
                 }
                 return jsonData;