Correctly throw ErrorDataDecoderException for errors while decoding (#11198)

Motivation:

We didn't correctly handle the case when no content-type header was found or if the charset was illegal and just did throw a NPE or ICE. We should in both cases throw an ErrorDataDecoderException to reflect what is documented in the javadocs.

Modifications:

- Throw correct exception
- Merge private method into the constructor as it is only used there
- Add unit tests

Result:

Throw expected exceptions on decoding errors

codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostMultipartRequestDecoder.java

@@ -35,6 +35,7 @@ import io.netty.util.internal.StringUtil;
 
 import java.io.IOException;
 import java.nio.charset.Charset;
+import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.UnsupportedCharsetException;
 import java.util.ArrayList;
 import java.util.List;
@@ -183,7 +184,26 @@ public class HttpPostMultipartRequestDecoder implements InterfaceHttpPostRequest
         this.factory = requireNonNull(factory, "factory");
         // Fill default values
 
-        setMultipart(this.request.headers().get(HttpHeaderNames.CONTENT_TYPE));
+        String contentTypeValue = this.request.headers().get(HttpHeaderNames.CONTENT_TYPE);
+        if (contentTypeValue == null) {
+            throw new ErrorDataDecoderException("No '" + HttpHeaderNames.CONTENT_TYPE + "' header present.");
+        }
+
+        String[] dataBoundary = HttpPostRequestDecoder.getMultipartDataBoundary(contentTypeValue);
+        if (dataBoundary != null) {
+            multipartDataBoundary = dataBoundary[0];
+            if (dataBoundary.length > 1 && dataBoundary[1] != null) {
+                try {
+                    this.charset = Charset.forName(dataBoundary[1]);
+                } catch (IllegalCharsetNameException e) {
+                    throw new ErrorDataDecoderException(e);
+                }
+            }
+        } else {
+            multipartDataBoundary = null;
+        }
+        currentStatus = MultiPartStatus.HEADERDELIMITER;
+
         if (request instanceof HttpContent) {
             // Offer automatically if the given request is als type of HttpContent
             // See #1089
@@ -193,22 +213,6 @@ public class HttpPostMultipartRequestDecoder implements InterfaceHttpPostRequest
         }
     }
 
-    /**
-     * Set from the request ContentType the multipartDataBoundary and the possible charset.
-     */
-    private void setMultipart(String contentType) {
-        String[] dataBoundary = HttpPostRequestDecoder.getMultipartDataBoundary(contentType);
-        if (dataBoundary != null) {
-            multipartDataBoundary = dataBoundary[0];
-            if (dataBoundary.length > 1 && dataBoundary[1] != null) {
-                charset = Charset.forName(dataBoundary[1]);
-            }
-        } else {
-            multipartDataBoundary = null;
-        }
-        currentStatus = MultiPartStatus.HEADERDELIMITER;
-    }
-
     private void checkDestroyed() {
         if (destroyed) {
             throw new IllegalStateException(HttpPostMultipartRequestDecoder.class.getSimpleName()

codec-http/src/test/java/io/netty/handler/codec/http/multipart/HttpPostMultiPartRequestDecoderTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2021 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.handler.codec.http.multipart;
+
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpVersion;
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+public class HttpPostMultiPartRequestDecoderTest {
+
+    @Test
+    public void testDecodeFullHttpRequestWithNoContentTypeHeader() {
+        FullHttpRequest req = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, "/");
+        try {
+            new HttpPostMultipartRequestDecoder(req);
+            fail("Was expecting an ErrorDataDecoderException");
+        } catch (HttpPostRequestDecoder.ErrorDataDecoderException expected) {
+            // expected
+        } finally {
+            assertTrue(req.release());
+        }
+    }
+
+    @Test
+    public void testDecodeFullHttpRequestWithInvalidCharset() {
+        FullHttpRequest req = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, "/");
+        req.headers().set(HttpHeaderNames.CONTENT_TYPE,
+                "multipart/form-data; boundary=--89421926422648 [; charset=UTF-8]");
+
+        try {
+            new HttpPostMultipartRequestDecoder(req);
+            fail("Was expecting an ErrorDataDecoderException");
+        } catch (HttpPostRequestDecoder.ErrorDataDecoderException expected) {
+            // expected
+        } finally {
+            assertTrue(req.release());
+        }
+    }
+}