Use SHA256 by default in Remember Me

Closes gh-11520

docs/modules/ROOT/pages/servlet/authentication/rememberme.adoc

@@ -114,9 +114,9 @@ A `key` is shared between this authentication provider and the `TokenBasedRememb
 In addition, `TokenBasedRememberMeServices` requires a `UserDetailsService`, from which it can retrieve the username and password for signature comparison purposes and generate the `RememberMeAuthenticationToken` to contain the correct `GrantedAuthority` instances.
 `TokenBasedRememberMeServices` also implements Spring Security's `LogoutHandler` interface so that it can be used with `LogoutFilter` to have the cookie cleared automatically.
 
-By default, this implementation uses the MD5 algorithm to encode the token signature.
+By default, this implementation uses the SHA-256 algorithm to encode the token signature.
 To verify the token signature, the algorithm retrieved from `algorithmName` is parsed and used.
-If no `algorithmName` is present, the default matching algorithm will be used, which is MD5.
+If no `algorithmName` is present, the default matching algorithm will be used, which is SHA-256.
 You can specify different algorithms for signature encoding and for signature matching, this allows users to safely upgrade to a different encoding algorithm while still able to verify old ones if there is no `algorithmName` present.
 To do that you can specify your customized `TokenBasedRememberMeServices` as a Bean and use it in the configuration.
 

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

@@ -94,9 +94,9 @@ import org.springframework.util.StringUtils;
  */
 public class TokenBasedRememberMeServices extends AbstractRememberMeServices {
 
-	private static final RememberMeTokenAlgorithm DEFAULT_MATCHING_ALGORITHM = RememberMeTokenAlgorithm.MD5;
+	private static final RememberMeTokenAlgorithm DEFAULT_MATCHING_ALGORITHM = RememberMeTokenAlgorithm.SHA256;
 
-	private static final RememberMeTokenAlgorithm DEFAULT_ENCODING_ALGORITHM = RememberMeTokenAlgorithm.MD5;
+	private static final RememberMeTokenAlgorithm DEFAULT_ENCODING_ALGORITHM = RememberMeTokenAlgorithm.SHA256;
 
 	private final RememberMeTokenAlgorithm encodingAlgorithm;
 

web/src/test/java/org/springframework/security/web/authentication/rememberme/TokenBasedRememberMeServicesTests.java

@@ -407,7 +407,7 @@ public class TokenBasedRememberMeServicesTests {
 		assertThat(cookie.getMaxAge()).isEqualTo(this.services.getTokenValiditySeconds());
 		assertThat(CodecTestUtils.isBase64(cookie.getValue().getBytes())).isTrue();
 		assertThat(new Date().before(new Date(determineExpiryTimeFromBased64EncodedToken(cookie.getValue())))).isTrue();
-		assertThat("MD5").isEqualTo(determineAlgorithmNameFromBase64EncodedToken(cookie.getValue()));
+		assertThat("SHA256").isEqualTo(determineAlgorithmNameFromBase64EncodedToken(cookie.getValue()));
 	}
 
 	@Test
@@ -459,11 +459,11 @@ public class TokenBasedRememberMeServicesTests {
 	}
 
 	@Test
-	public void constructorWhenNoEncodingAlgorithmSpecifiedThenMd5() {
+	public void constructorWhenNoEncodingAlgorithmSpecifiedThenSha256() {
 		TokenBasedRememberMeServices rememberMeServices = new TokenBasedRememberMeServices("key", this.uds);
 		RememberMeTokenAlgorithm encodingAlgorithm = (RememberMeTokenAlgorithm) ReflectionTestUtils
 				.getField(rememberMeServices, "encodingAlgorithm");
-		assertThat(encodingAlgorithm).isSameAs(RememberMeTokenAlgorithm.MD5);
+		assertThat(encodingAlgorithm).isSameAs(RememberMeTokenAlgorithm.SHA256);
 	}
 
 }