Restrict design doc update methodsrestrict-ddoc-update-methods

Documentation for design doc update functions specifies that permitted
methods are:

    POST /{db}/_design/{ddoc}/_update/{func}
    PUT /{db}/_design/{ddoc}/_update/{func}/{docid} [2]

But currently anything is accepted, even bogus methods such as in the
following example work:

```
$ curl -v -u adm localhost:15984/db-1/_design/ddoc/_update/change -X BOGUS

> BOGUS /db-1/_design/bar/_update/change HTTP/1.1
>
< HTTP/1.1 200 OK
< content-length: 11
< content-type: text/html; charset=utf-8
<
* Connection #0 to host localhost left intact
Empty World* Closing connection 0
```

A strict reading of the docs indicates that the null document endpoint
only allows POST [1] while the endpoint taking a document id only
allows PUT [2]. However, the examples in both cases exclusively use
POST, and also PUT doesn't make as much sense from a semantic
perspective since a new resource isn't being created, I assume the PUT
 is a typo, and both should be changed to POST.

However, given the inconsistent usage even in CouchDB's own test
suite, it seems prudent to minimize incompatibility, while still
imposing reasonable restrictions, and allow either PUT or POST for
both endpoints.

[1] https://docs.couchdb.org/en/latest/api/ddoc/render.html#post--db-_design-ddoc-_update-func
[2] https://docs.couchdb.org/en/latest/api/ddoc/render.html#put--db-_design-ddoc-_update-func-docid

2 files changed, 21 insertions, 9 deletions

diff --git a/src/chttpd/src/chttpd_show.erl b/src/chttpd/src/chttpd_show.erl
index c2c37c66d..de1eb2805 100644
--- a/src/chttpd/src/chttpd_show.erl
+++ b/src/chttpd/src/chttpd_show.erl
@@ -95,11 +95,12 @@ show_etag(#httpd{user_ctx=UserCtx}=Req, Doc, DDoc, More) ->
     couch_httpd:make_etag({couch_httpd:doc_etag(DDoc), DocPart, Accept,
         UserCtx#user_ctx.roles, More}).
 
-% /db/_design/foo/update/bar/docid
-% updates a doc based on a request
-% handle_doc_update_req(#httpd{method = 'GET'}=Req, _Db, _DDoc) ->
-%     % anything but GET
-%     send_method_not_allowed(Req, "POST,PUT,DELETE,ETC");
+
+handle_doc_update_req(#httpd{
+        method=Method,
+        path_parts=[_, <<"_design">>, _, <<"_update">> | _MaybeDocIdParts]
+    }=Req, _Db, _DDoc) when Method =/= 'POST' andalso Method =/= 'PUT' ->
+    chttpd:send_method_not_allowed(Req, "POST,PUT");
 
 handle_doc_update_req(#httpd{
         path_parts=[_, _, _, _, UpdateName]
diff --git a/test/elixir/test/update_documents_test.exs b/test/elixir/test/update_documents_test.exs
index c29b31a4d..df5856b44 100644
--- a/test/elixir/test/update_documents_test.exs
+++ b/test/elixir/test/update_documents_test.exs
@@ -106,6 +106,17 @@ defmodule UpdateDocumentsTest do
   @document %{word: "plankton", name: "Rusty"}
 
   @tag :with_db
+  test "update error method not allowed", context do
+    db_name = context[:db_name]
+    create_doc(db_name, @ddoc)
+
+    resp = Couch.get("/#{db_name}/_design/update/_update/")
+    assert resp.status_code == 405
+    assert resp.body["error"] == "method_not_allowed"
+    assert resp.body["reason"] == "Only POST,PUT allowed"
+  end
+
+  @tag :with_db
   test "update error invalid path", context do
     db_name = context[:db_name]
     create_doc(db_name, @ddoc)
@@ -135,7 +146,7 @@ defmodule UpdateDocumentsTest do
     # Fix for COUCHDB-379
     assert String.starts_with?(resp.headers["Server"], "CouchDB")
 
-    resp = Couch.put("/#{db_name}/_design/update/_update/hello")
+    resp = Couch.post("/#{db_name}/_design/update/_update/hello")
     assert resp.status_code == 200
     assert resp.body == "<p>Empty World</p>"
   end
@@ -246,7 +257,7 @@ defmodule UpdateDocumentsTest do
   test "Server provides UUID when POSTing without an ID in the URL", context do
     db_name = context[:db_name]
     create_doc(db_name, @ddoc)
-    resp = Couch.put("/#{db_name}/_design/update/_update/get-uuid/")
+    resp = Couch.post("/#{db_name}/_design/update/_update/get-uuid/")
     assert resp.status_code == 200
     assert String.length(resp.body) == 32
   end
@@ -286,10 +297,10 @@ defmodule UpdateDocumentsTest do
     assert resp.status_code == 200
     assert resp.body["counter"] == 3
 
-    resp = Couch.put("/#{db_name}/_design/update/_update/resp-code/")
+    resp = Couch.post("/#{db_name}/_design/update/_update/resp-code/")
     assert resp.status_code == 302
 
-    resp = Couch.put("/#{db_name}/_design/update/_update/resp-code-and-json/")
+    resp = Couch.post("/#{db_name}/_design/update/_update/resp-code-and-json/")
     assert resp.status_code == 302
     assert resp.body["ok"] == true
   end