remove 32-byte minimum keyLength restriction in `Base64StringKeyGenerator` (#17012)

Signed-off-by: Andrey Litvitski <andrey1010102008@gmail.com>

crypto/src/main/java/org/springframework/security/crypto/keygen/Base64StringKeyGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -24,6 +24,7 @@ import java.util.Base64;
  *
  * @author Joe Grandja
  * @author Rob Winch
+ * @author Andrey Litvitski
  * @since 5.0
  */
 public class Base64StringKeyGenerator implements StringKeyGenerator {
@@ -67,8 +68,8 @@ public class Base64StringKeyGenerator implements StringKeyGenerator {
 		if (encoder == null) {
 			throw new IllegalArgumentException("encode cannot be null");
 		}
-		if (keyLength < DEFAULT_KEY_LENGTH) {
+		if (keyLength <= 0) {
-			throw new IllegalArgumentException("keyLength must be greater than or equal to " + DEFAULT_KEY_LENGTH);
+			throw new IllegalArgumentException("keyLength must be greater than 0");
 		}
 		this.encoder = encoder;
 		this.keyGenerator = KeyGenerators.secureRandom(keyLength);

crypto/src/test/java/org/springframework/security/crypto/keygen/Base64StringKeyGeneratorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -25,13 +25,14 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
 
 /**
  * @author Rob Winch
+ * @author Andrey Litvitski
  * @since 5.0
  */
 public class Base64StringKeyGeneratorTests {
 
 	@Test
-	public void constructorIntWhenLessThan32ThenIllegalArgumentException() {
+	public void constructorIntWhenEqual0ThenIllegalArgumentException() {
-		assertThatIllegalArgumentException().isThrownBy(() -> new Base64StringKeyGenerator(31));
+		assertThatIllegalArgumentException().isThrownBy(() -> new Base64StringKeyGenerator(0));
 	}
 
 	@Test