KTOR-7470 Rethrow UnsupportedMediaTypeException if content type header is not present or is invalid

Author: Gleb Nazarov

ktor-server/ktor-server-core/common/src/io/ktor/server/plugins/Errors.kt

@@ -85,9 +85,11 @@ public class CannotTransformContentToTypeException(
  */
 @OptIn(ExperimentalCoroutinesApi::class)
 public class UnsupportedMediaTypeException(
-    private val contentType: ContentType
-) : ContentTransformationException("Content type $contentType is not supported"),
-    CopyableThrowable<UnsupportedMediaTypeException> {
+    private val contentType: ContentType?
+) : ContentTransformationException(
+    contentType?.let { "Content type $it is not supported" }
+        ?: "Content-Type header is required for multipart processing"
+), CopyableThrowable<UnsupportedMediaTypeException> {
 
     override fun createCopy(): UnsupportedMediaTypeException = UnsupportedMediaTypeException(contentType).also {
         it.initCauseBridge(this)

ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/DefaultTransformJvm.kt

@@ -8,6 +8,7 @@ import io.ktor.http.*
 import io.ktor.http.cio.*
 import io.ktor.http.content.*
 import io.ktor.server.application.*
+import io.ktor.server.plugins.UnsupportedMediaTypeException
 import io.ktor.server.request.*
 import io.ktor.util.pipeline.*
 import io.ktor.utils.io.*
@@ -17,6 +18,7 @@ import io.ktor.utils.io.streams.*
 import kotlinx.coroutines.*
 import kotlinx.io.*
 import java.io.*
+import java.io.IOException
 
 internal actual suspend fun PipelineContext<Any, PipelineCall>.defaultPlatformTransformations(
     query: Any
@@ -33,16 +35,21 @@ internal actual suspend fun PipelineContext<Any, PipelineCall>.defaultPlatformTr
 @OptIn(InternalAPI::class)
 internal actual fun PipelineContext<*, PipelineCall>.multiPartData(rc: ByteReadChannel): MultiPartData {
     val contentType = call.request.header(HttpHeaders.ContentType)
-        ?: throw IllegalStateException("Content-Type header is required for multipart processing")
+        ?: throw UnsupportedMediaTypeException(null)
 
     val contentLength = call.request.header(HttpHeaders.ContentLength)?.toLong()
-    return CIOMultipartDataBase(
-        coroutineContext + Dispatchers.Unconfined,
-        rc,
-        contentType,
-        contentLength,
-        call.formFieldLimit
-    )
+
+    try {
+        return CIOMultipartDataBase(
+            coroutineContext + Dispatchers.Unconfined,
+            rc,
+            contentType,
+            contentLength,
+            call.formFieldLimit
+        )
+    } catch (_: IOException) {
+        throw UnsupportedMediaTypeException(ContentType.parse(contentType))
+    }
 }
 
 internal actual fun Source.readTextWithCustomCharset(charset: Charset): String =

ktor-server/ktor-server-core/jvm/test/io/ktor/tests/server/engine/MultiPartDataTest.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.tests.server.engine
+
+import io.ktor.http.*
+import io.ktor.server.application.*
+import io.ktor.server.engine.multiPartData
+import io.ktor.server.plugins.UnsupportedMediaTypeException
+import io.ktor.server.request.*
+import io.ktor.util.pipeline.*
+import io.ktor.utils.io.*
+import io.mockk.*
+import kotlinx.coroutines.*
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
+import kotlin.test.*
+
+class MultiPartDataTest {
+    private val mockContext = mockk<PipelineContext<*, PipelineCall>>(relaxed = true)
+    private val mockRequest = mockk<PipelineRequest>(relaxed = true)
+    private val testScope = TestScope()
+
+    @Test
+    fun givenRequest_whenNoContentTypeHeaderPresent_thenUnsupportedMediaTypeException() {
+        // Setup
+        every { mockContext.call.request } returns mockRequest
+        every { mockRequest.header(HttpHeaders.ContentType) } returns null
+
+        // Act & Assert
+        assertFailsWith<UnsupportedMediaTypeException> {
+            runBlocking { mockContext.multiPartData(ByteReadChannel("sample data")) }
+        }
+    }
+
+    @Test
+    fun givenWrongContentType_whenProcessMultiPart_thenUnsupportedMediaTypeException() {
+        // Given
+        val rc = ByteReadChannel("sample data")
+        val contentType = "test/plain; boundary=test"
+        val contentLength = "123"
+        every { mockContext.call.request } returns mockRequest
+        every { mockContext.call.attributes.getOrNull<Long>(any()) } returns 0L
+        every { mockRequest.header(HttpHeaders.ContentType) } returns contentType
+        every { mockRequest.header(HttpHeaders.ContentLength) } returns contentLength
+
+        // When & Then
+        testScope.runTest {
+            assertFailsWith<UnsupportedMediaTypeException> {
+                mockContext.multiPartData(rc)
+            }
+        }
+    }
+}