Proxy of empty POST requests missing to content-lenght header

[vonatzigenc]

• WireMock version: 2.33.2
• Main-Method of WireMockServerRunner without any options

If a POST request with an empty payload is sent via a proxy mapping, the “content-length” header is lost. This causes the server to respond with status 411 (“The request must be chunked or have a content length”).

Example:

Stub Mapping:

{
  "request": {
    "urlPathPattern": "/example/.*",
    "method": "ANY"
  },
  "response": {
    "proxyBaseUrl": "https://api.app.mobiliar-sit.ch"
  }
}

Request: curl -X POST --location "http://localhost:8080/example/empty-post" -H "Content-Length: 0"

Analysis

There have been several changes which, in my opinion, lead to the behavior.

• With Adopt Apache HttpClient 5 for src/main #1625 the ContentType.DEFAULT_BINARY is set as default. (Will be ignored, if content-type Header is set)

  • wiremock/src/main/java/com/github/tomakehurst/wiremock/http/ProxyResponseRenderer.java

    Line 219 in 59e8c00

    new ByteArrayEntity(originalRequest.getBody(), ContentType.DEFAULT_BINARY)

• With proxy request fix #1765 the body of all http-methods is proxied
• This led to Wiremock 2.33.0+ - UnsupportedMediaType error on the back end for a GET request proxied by WireMock #1864 , where the fix Don't create request entity when it was not present in original request #1865 actually removes the empty body and thus also the content-length header
  -- Issue was "Unsupported Media Type", which usually comes from a “wrong” content-type header.

Proposed solution

• Don't set a default ContentType at

  wiremock/src/main/java/com/github/tomakehurst/wiremock/http/ProxyResponseRenderer.java

  Line 232 in 6728eb7

  new ByteArrayEntity(originalRequest.getBody(), ContentType.DEFAULT_BINARY));

  • Use the content-type from header of the original request or set it to null
• Create and add "HttpEntity", if it's an empty byte[] but content-length is set
  • Alternative: Always create HttpEntity. Drawback of this solution is, that the content-length Header will be set for all requests. (including GET).