Update HttpHeaderParser.scala

Author: pjfanning

http-core/src/main/scala/org/apache/pekko/http/impl/engine/parsing/HttpHeaderParser.scala

@@ -167,6 +167,7 @@ private[engine] final class HttpHeaderParser private (
   private def parseRawHeader(input: ByteString, lineStart: Int, cursor: Int, nodeIx: Int): Int = {
     val colonIx = input.indexOf(':', cursor, lineStart + 1 + maxHeaderNameLength)
     if (colonIx == -1) {
+      scanIllegalHeaderNameCharacters(input, cursor, lineStart + 1 + maxHeaderNameLength)
       fail(s"HTTP header name exceeds the configured limit of $maxHeaderNameLength characters",
         StatusCodes.RequestHeaderFieldsTooLarge)
     } else {
@@ -210,6 +211,32 @@ private[engine] final class HttpHeaderParser private (
     if (start == end) "" else build()
   }
 
+  // similar to scanAsciiString but only scans for illegal characters and fails or warns if it finds one
+  private def scanIllegalHeaderNameCharacters(input: ByteString, start: Int, end: Int): Unit = {
+    @tailrec def check(ix: Int = start): Unit =
+      if (ix == end) {
+        ()
+      } else {
+        val c = input(ix).toChar
+        if (tchar(c)) {
+          check(ix + 1)
+        } else {
+          settings.illegalResponseHeaderNameProcessingMode match {
+            case IllegalResponseHeaderNameProcessingMode.Error =>
+              fail(s"Illegal character '${escape(c)}' in header name")
+            case IllegalResponseHeaderNameProcessingMode.Warn =>
+              log.warning(s"Header key contains illegal character '${escape(c)}'")
+              check(ix + 1)
+            case IllegalResponseHeaderNameProcessingMode.Ignore =>
+              ()
+          }
+        }
+      }
+    if (start == end || settings.illegalResponseHeaderNameProcessingMode == IllegalResponseHeaderNameProcessingMode.Ignore)
+      ()
+    else check()
+  }
+
   @tailrec
   private def parseHeaderValue(input: ByteString, valueStart: Int, branch: ValueBranch)(cursor: Int = valueStart,
       nodeIx: Int = branch.branchRootNodeIx): Int = {