Require Locale argument for toLower/toUpperCase usage

cas/src/main/java/org/springframework/security/cas/userdetails/GrantedAuthorityFromAssertionAttributesUserDetailsService.java

@@ -18,6 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 import org.jasig.cas.client.validation.Assertion;
 
@@ -73,7 +74,8 @@ protected UserDetails loadUserDetails(final Assertion assertion) {
 	}
 
 	private SimpleGrantedAuthority createSimpleGrantedAuthority(Object o) {
-		return new SimpleGrantedAuthority(this.convertToUpperCase ? o.toString().toUpperCase() : o.toString());
+		return new SimpleGrantedAuthority(
+				this.convertToUpperCase ? o.toString().toUpperCase(Locale.ROOT) : o.toString());
 	}
 
 	/**

config/src/main/java/org/springframework/security/config/http/HttpConfigurationBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 import javax.servlet.ServletRequest;
 
@@ -286,7 +287,7 @@ void setCsrfIgnoreRequestMatchers(List<BeanDefinition> requestMatchers) {
 
 	// Needed to account for placeholders
 	static String createPath(String path, boolean lowerCase) {
-		return lowerCase ? path.toLowerCase() : path;
+		return lowerCase ? path.toLowerCase(Locale.ENGLISH) : path;
 	}
 
 	BeanReference getSecurityContextRepositoryForAuthenticationFilters() {

core/src/main/java/org/springframework/security/core/authority/mapping/SimpleAttributes2GrantedAuthoritiesMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -79,10 +79,10 @@ public List<GrantedAuthority> getGrantedAuthorities(Collection<String> attribute
 	 */
 	private GrantedAuthority getGrantedAuthority(String attribute) {
 		if (isConvertAttributeToLowerCase()) {
-			attribute = attribute.toLowerCase(Locale.getDefault());
+			attribute = attribute.toLowerCase(Locale.ROOT);
 		}
 		else if (isConvertAttributeToUpperCase()) {
-			attribute = attribute.toUpperCase(Locale.getDefault());
+			attribute = attribute.toUpperCase(Locale.ROOT);
 		}
 		if (isAddPrefixIfAlreadyExisting() || !attribute.startsWith(getAttributePrefix())) {
 			return new SimpleGrantedAuthority(getAttributePrefix() + attribute);

core/src/main/java/org/springframework/security/core/authority/mapping/SimpleAuthorityMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
 import java.util.Collection;
 import java.util.HashSet;
+import java.util.Locale;
 import java.util.Set;
 
 import org.springframework.beans.factory.InitializingBean;
@@ -71,10 +72,10 @@ public Set<GrantedAuthority> mapAuthorities(Collection<? extends GrantedAuthorit
 
 	private GrantedAuthority mapAuthority(String name) {
 		if (this.convertToUpperCase) {
-			name = name.toUpperCase();
+			name = name.toUpperCase(Locale.ROOT);
 		}
 		else if (this.convertToLowerCase) {
-			name = name.toLowerCase();
+			name = name.toLowerCase(Locale.ROOT);
 		}
 		if (this.prefix.length() > 0 && !name.startsWith(this.prefix)) {
 			name = this.prefix + name;

core/src/main/java/org/springframework/security/core/userdetails/MapReactiveUserDetailsService.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -91,7 +92,7 @@ private UserDetails withNewPassword(UserDetails userDetails, String newPassword)
 	}
 
 	private String getKey(String username) {
-		return username.toLowerCase();
+		return username.toLowerCase(Locale.ROOT);
 	}
 
 }

core/src/main/java/org/springframework/security/core/userdetails/memory/UserAttributeEditor.java

@@ -19,6 +19,7 @@
 import java.beans.PropertyEditorSupport;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 import org.springframework.util.StringUtils;
 
@@ -45,10 +46,10 @@ public void setAsText(String s) throws IllegalArgumentException {
 				userAttrib.setPassword(currentToken);
 			}
 			else {
-				if (currentToken.toLowerCase().equals("enabled")) {
+				if (currentToken.toLowerCase(Locale.ENGLISH).equals("enabled")) {
 					userAttrib.setEnabled(true);
 				}
-				else if (currentToken.toLowerCase().equals("disabled")) {
+				else if (currentToken.toLowerCase(Locale.ENGLISH).equals("disabled")) {
 					userAttrib.setEnabled(false);
 				}
 				else {

core/src/main/java/org/springframework/security/provisioning/InMemoryUserDetailsManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@
 import java.util.Collection;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Properties;
 
@@ -92,23 +93,23 @@ private User createUserDetails(String name, UserAttribute attr) {
 	@Override
 	public void createUser(UserDetails user) {
 		Assert.isTrue(!userExists(user.getUsername()), "user should not exist");
-		this.users.put(user.getUsername().toLowerCase(), new MutableUser(user));
+		this.users.put(user.getUsername().toLowerCase(Locale.ROOT), new MutableUser(user));
 	}
 
 	@Override
 	public void deleteUser(String username) {
-		this.users.remove(username.toLowerCase());
+		this.users.remove(username.toLowerCase(Locale.ROOT));
 	}
 
 	@Override
 	public void updateUser(UserDetails user) {
 		Assert.isTrue(userExists(user.getUsername()), "user should exist");
-		this.users.put(user.getUsername().toLowerCase(), new MutableUser(user));
+		this.users.put(user.getUsername().toLowerCase(Locale.ROOT), new MutableUser(user));
 	}
 
 	@Override
 	public boolean userExists(String username) {
-		return this.users.containsKey(username.toLowerCase());
+		return this.users.containsKey(username.toLowerCase(Locale.ROOT));
 	}
 
 	@Override
@@ -139,14 +140,14 @@ public void changePassword(String oldPassword, String newPassword) {
 	@Override
 	public UserDetails updatePassword(UserDetails user, String newPassword) {
 		String username = user.getUsername();
-		MutableUserDetails mutableUser = this.users.get(username.toLowerCase());
+		MutableUserDetails mutableUser = this.users.get(username.toLowerCase(Locale.ROOT));
 		mutableUser.setPassword(newPassword);
 		return mutableUser;
 	}
 
 	@Override
 	public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
-		UserDetails user = this.users.get(username.toLowerCase());
+		UserDetails user = this.users.get(username.toLowerCase(Locale.ROOT));
 		if (user == null) {
 			throw new UsernameNotFoundException(username);
 		}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 
 import java.security.MessageDigest;
 import java.util.Base64;
+import java.util.Locale;
 
 import org.springframework.security.crypto.codec.Utf8;
 import org.springframework.security.crypto.keygen.BytesKeyGenerator;
@@ -50,11 +51,11 @@ public class LdapShaPasswordEncoder implements PasswordEncoder {
 
 	private static final String SSHA_PREFIX = "{SSHA}";
 
-	private static final String SSHA_PREFIX_LC = SSHA_PREFIX.toLowerCase();
+	private static final String SSHA_PREFIX_LC = SSHA_PREFIX.toLowerCase(Locale.ENGLISH);
 
 	private static final String SHA_PREFIX = "{SHA}";
 
-	private static final String SHA_PREFIX_LC = SHA_PREFIX.toLowerCase();
+	private static final String SHA_PREFIX_LC = SHA_PREFIX.toLowerCase(Locale.ENGLISH);
 
 	private BytesKeyGenerator saltGenerator;
 

etc/checkstyle/checkstyle-suppressions.xml

@@ -53,4 +53,11 @@
 	<suppress files="WithSecurityContextTestExecutionListenerTests\.java" checks="SpringMethodVisibility"/>
 	<suppress files="AbstractOAuth2AuthorizationGrantRequestEntityConverter\.java" checks="SpringMethodVisibility"/>
 	<suppress files="JoseHeader\.java" checks="SpringMethodVisibility"/>
+
+	<!-- Lambdas that we can't replace with a method reference because a closure is required -->
+	<suppress files="BearerTokenAuthenticationFilter\.java" checks="SpringLambda"/>
+
+	<!-- Ignore String.toUpperCase() and String.toLowerCase() checks in tests -->
+	<suppress files="[\\/]src[\\/]test[\\/]" checks="RegexpSinglelineJava" id="toLowerCaseWithoutLocale"/>
+	<suppress files="[\\/]src[\\/]test[\\/]" checks="RegexpSinglelineJava" id="toUpperCaseWithoutLocale"/>
 </suppressions>

etc/checkstyle/checkstyle.xml

@@ -23,5 +23,21 @@
 			<property name="message" value="Please use assertThatExceptionOfType." />
 			<property name="ignoreComments" value="true" />
 		</module>
+		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
+			<property name="id" value="toLowerCaseWithoutLocale"/>
+			<property name="format" value="\.toLowerCase\(\)"/>
+			<property name="maximum" value="0"/>
+			<property name="message"
+					  value="String.toLowerCase() should be String.toLowerCase(Locale.ROOT) or String.toLowerCase(Locale.ENGLISH)"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
+		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
+			<property name="id" value="toUpperCaseWithoutLocale"/>
+			<property name="format" value="\.toUpperCase\(\)"/>
+			<property name="maximum" value="0"/>
+			<property name="message"
+					  value="String.toUpperCase() should be String.toUpperCase(Locale.ROOT) or String.toUpperCase(Locale.ENGLISH)"/>
+			<property name="ignoreComments" value="true"/>
+		</module>
 	</module>
 </module>

ldap/src/main/java/org/springframework/security/ldap/LdapEncoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2005-2010 the original author or authors.
+ * Copyright 2005-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.ldap;
 
+import java.util.Locale;
+
 import org.springframework.ldap.BadLdapGrammarException;
 
 /**
@@ -72,7 +74,7 @@ private LdapEncoder() {
 	}
 
 	protected static String toTwoCharHex(char c) {
-		String raw = Integer.toHexString(c).toUpperCase();
+		String raw = Integer.toHexString(c).toUpperCase(Locale.ENGLISH);
 		return (raw.length() > 1) ? raw : "0" + raw;
 	}
 

ldap/src/main/java/org/springframework/security/ldap/authentication/LdapEncoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2005-2010 the original author or authors.
+ * Copyright 2005-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.ldap.authentication;
 
+import java.util.Locale;
+
 import org.springframework.ldap.BadLdapGrammarException;
 
 /**
@@ -72,7 +74,7 @@ private LdapEncoder() {
 	}
 
 	protected static String toTwoCharHex(char c) {
-		String raw = Integer.toHexString(c).toUpperCase();
+		String raw = Integer.toHexString(c).toUpperCase(Locale.ENGLISH);
 		return (raw.length() > 1) ? raw : "0" + raw;
 	}
 

ldap/src/main/java/org/springframework/security/ldap/authentication/ad/ActiveDirectoryLdapAuthenticationProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@
 import java.util.HashMap;
 import java.util.Hashtable;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -142,9 +143,9 @@ public final class ActiveDirectoryLdapAuthenticationProvider extends AbstractLda
 	 */
 	public ActiveDirectoryLdapAuthenticationProvider(String domain, String url, String rootDn) {
 		Assert.isTrue(StringUtils.hasText(url), "Url cannot be empty");
-		this.domain = StringUtils.hasText(domain) ? domain.toLowerCase() : null;
+		this.domain = StringUtils.hasText(domain) ? domain.toLowerCase(Locale.ROOT) : null;
 		this.url = url;
-		this.rootDn = StringUtils.hasText(rootDn) ? rootDn.toLowerCase() : null;
+		this.rootDn = StringUtils.hasText(rootDn) ? rootDn.toLowerCase(Locale.ROOT) : null;
 	}
 
 	/**
@@ -153,7 +154,7 @@ public ActiveDirectoryLdapAuthenticationProvider(String domain, String url, Stri
 	 */
 	public ActiveDirectoryLdapAuthenticationProvider(String domain, String url) {
 		Assert.isTrue(StringUtils.hasText(url), "Url cannot be empty");
-		this.domain = StringUtils.hasText(domain) ? domain.toLowerCase() : null;
+		this.domain = StringUtils.hasText(domain) ? domain.toLowerCase(Locale.ROOT) : null;
 		this.url = url;
 		this.rootDn = (this.domain != null) ? rootDnFromDomain(this.domain) : null;
 	}
@@ -361,7 +362,7 @@ private String rootDnFromDomain(String domain) {
 	}
 
 	String createBindPrincipal(String username) {
-		if (this.domain == null || username.toLowerCase().endsWith(this.domain)) {
+		if (this.domain == null || username.toLowerCase(Locale.ROOT).endsWith(this.domain)) {
 			return username;
 		}
 		return username + "@" + this.domain;

ldap/src/main/java/org/springframework/security/ldap/userdetails/DefaultLdapAuthoritiesPopulator.java

@@ -20,6 +20,7 @@
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Function;
@@ -179,7 +180,7 @@ else if (groupSearchBase.length() == 0) {
 				return null;
 			}
 			if (this.convertToUpperCase) {
-				role = role.toUpperCase();
+				role = role.toUpperCase(Locale.ROOT);
 			}
 			return new SimpleGrantedAuthority(this.rolePrefix + role);
 		};