Fix tchar pattern in RestRequest (#96406)

This commits fixes the incorrect pattern for TChar defined in RFC7230 section 3.2.6
`a-zA-z` was accidentally used and the pattern `a-zA-Z` should be used instead

docs/changelog/96406.yaml

@@ -0,0 +1,5 @@
+pr: 96406
+summary: Fix tchar pattern in `RestRequest`
+area: Infra/REST API
+type: bug
+issues: []

libs/x-content/src/main/java/org/elasticsearch/xcontent/ParsedMediaType.java

@@ -27,7 +27,7 @@ public class ParsedMediaType {
     private final String subType;
     private final Map<String, String> parameters;
     // tchar pattern as defined by RFC7230 section 3.2.6
-    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-z0-9!#$%&'*+\\-.\\^_`|~]+");
+    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-Z0-9!#$%&'*+\\-.\\^_`|~]+");
 
     private ParsedMediaType(String originalHeaderValue, String type, String subType, Map<String, String> parameters) {
         this.originalHeaderValue = originalHeaderValue;

libs/x-content/src/test/java/org/elasticsearch/xcontent/ParsedMediaTypeTests.java

@@ -11,6 +11,7 @@ package org.elasticsearch.xcontent;
 import org.elasticsearch.test.ESTestCase;
 
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 
 import static org.hamcrest.Matchers.equalTo;
@@ -108,6 +109,14 @@ public class ParsedMediaTypeTests extends ESTestCase {
         assertEquals(Collections.emptyMap(), parsedMediaType.getParameters());
     }
 
+    public void testMalformedMediaType() {
+        List<String> headers = List.of("a/b[", "a/b]", "a/b\\");
+        for (String header : headers) {
+            IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> ParsedMediaType.parseMediaType(header));
+            assertThat(e.getMessage(), equalTo("invalid media-type [" + header + "]"));
+        }
+    }
+
     public void testMalformedParameters() {
         String mediaType = "application/foo";
         IllegalArgumentException exception = expectThrows(

server/src/main/java/org/elasticsearch/rest/RestRequest.java

@@ -48,7 +48,7 @@ import static org.elasticsearch.core.TimeValue.parseTimeValue;
 public class RestRequest implements ToXContent.Params {
 
     // tchar pattern as defined by RFC7230 section 3.2.6
-    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-z0-9!#$%&'*+\\-.\\^_`|~]+");
+    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-Z0-9!#$%&'*+\\-.\\^_`|~]+");
 
     private static final AtomicLong requestIdGenerator = new AtomicLong();
 

server/src/test/java/org/elasticsearch/rest/RestRequestTests.java

@@ -201,6 +201,17 @@ public class RestRequestTests extends ESTestCase {
         assertThat(e.getMessage(), equalTo("Invalid media-type value on headers [Content-Type]"));
     }
 
+    public void testInvalidMediaTypeCharacter() {
+        List<String> headers = List.of("a/b[", "a/b]", "a/b\\");
+        for (String header : headers) {
+            IllegalArgumentException e = expectThrows(
+                IllegalArgumentException.class,
+                () -> RestRequest.parseContentType(Collections.singletonList(header))
+            );
+            assertThat(e.getMessage(), equalTo("invalid Content-Type header [" + header + "]"));
+        }
+    }
+
     public void testNoContentTypeHeader() {
         RestRequest contentRestRequest = contentRestRequest("", Collections.emptyMap(), Collections.emptyMap());
         assertNull(contentRestRequest.getXContentType());

x-pack/plugin/sql/sql-proto/src/main/java/org/elasticsearch/xpack/sql/proto/content/ParsedMediaType.java

@@ -19,7 +19,7 @@ import java.util.stream.Collectors;
  */
 class ParsedMediaType {
     // tchar pattern as defined by RFC7230 section 3.2.6
-    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-z0-9!#$%&'*+\\-.\\^_`|~]+");
+    private static final Pattern TCHAR_PATTERN = Pattern.compile("[a-zA-Z0-9!#$%&'*+\\-.\\^_`|~]+");
 
     private final String originalHeaderValue;
     private final String type;