Detect missing colon when parsing http headers with no value (netty#9871)

Motivation:

Technical speaking its valid to have http headers with no values so we should support it. That said we need to detect if these are "generated" because of an "invalid" fold.

Modifications:

- Detect if a colon is missing when parsing headers.
- Add unit test

Result:

Fixes netty#9866

Author: normanmaurer

codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectDecoder.java

@@ -747,6 +747,11 @@ private void splitHeader(AppendableCharSequence sb) {
             }
         }
 
+        if (nameEnd == length) {
+            // There was no colon present at all.
+            throw new IllegalArgumentException("No colon found");
+        }
+
         for (colonEnd = nameEnd; colonEnd < length; colonEnd ++) {
             if (sb.charAtUnsafe(colonEnd) == ':') {
                 colonEnd ++;

codec-http/src/test/java/io/netty/handler/codec/http/HttpRequestDecoderTest.java

@@ -334,4 +334,20 @@ public void testWhitespace() {
         assertTrue(request.decoderResult().cause() instanceof IllegalArgumentException);
         assertFalse(channel.finish());
     }
+
+    @Test
+    public void testHeaderWithNoValueAndMissingColon() {
+        EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder());
+        String requestStr = "GET /some/path HTTP/1.1\r\n" +
+                "Content-Length: 0\r\n" +
+                "Host:\r\n" +
+                "netty.io\r\n\r\n";
+
+        assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, CharsetUtil.US_ASCII)));
+        HttpRequest request = channel.readInbound();
+        System.err.println(request.headers().names().toString());
+        assertTrue(request.decoderResult().isFailure());
+        assertTrue(request.decoderResult().cause() instanceof IllegalArgumentException);
+        assertFalse(channel.finish());
+    }
 }