ContentDisposition trims charset in filename

Backport of c8bce96

Closes gh-24112

Author: rstoyanchev

spring-web/src/main/java/org/springframework/http/ContentDisposition.java

@@ -277,7 +277,7 @@ public static ContentDisposition parse(String contentDisposition) {
 				}
 				else if (attribute.equals("filename*") ) {
 					filename = decodeHeaderFieldParam(value);
-					charset = Charset.forName(value.substring(0, value.indexOf('\'')));
+					charset = Charset.forName(value.substring(0, value.indexOf('\'')).trim());
 					Assert.isTrue(UTF_8.equals(charset) || ISO_8859_1.equals(charset),
 							"Charset should be UTF-8 or ISO-8859-1");
 				}
@@ -371,7 +371,7 @@ private static String decodeHeaderFieldParam(String input) {
 		if (firstQuoteIndex == -1 || secondQuoteIndex == -1) {
 			return input;
 		}
-		Charset charset = Charset.forName(input.substring(0, firstQuoteIndex));
+		Charset charset = Charset.forName(input.substring(0, firstQuoteIndex).trim());
 		Assert.isTrue(UTF_8.equals(charset) || ISO_8859_1.equals(charset),
 				"Charset should be UTF-8 or ISO-8859-1");
 		byte[] value = input.substring(secondQuoteIndex + 1, input.length()).getBytes(charset);

spring-web/src/test/java/org/springframework/http/ContentDispositionTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -71,6 +71,14 @@ public void parseAndIgnoreEmptyParts() {
 				.name("foo").filename("foo.txt").size(123L).build(), disposition);
 	}
 
+	@Test // gh-24112
+	public void parseEncodedFilenameWithPaddedCharset() {
+		ContentDisposition disposition = ContentDisposition
+				.parse("attachment; filename*= UTF-8''some-file.zip");
+		assertEquals(ContentDisposition.builder("attachment")
+				.filename("some-file.zip", StandardCharsets.UTF_8).build(), disposition);
+	}
+
 	@Test
 	public void parseEncodedFilename() {
 		ContentDisposition disposition = ContentDisposition