respect content-type header in finger request

lib/pleroma/web/web_finger.ex

@@ -94,7 +94,8 @@ def represent_user(user, "XML") do
     |> XmlBuilder.to_doc()
   end
 
-  defp webfinger_from_xml(doc) do
+  defp webfinger_from_xml(body) do
+    with {:ok, doc} <- XML.parse_document(body) do
       subject = XML.string_from_xpath("//Subject", doc)
 
       subscribe_address =
@@ -113,8 +114,10 @@ defp webfinger_from_xml(doc) do
 
       {:ok, data}
     end
+  end
 
-  defp webfinger_from_json(doc) do
+  defp webfinger_from_json(body) do
+    with {:ok, doc} <- Jason.decode(body) do
       data =
         Enum.reduce(doc["links"], %{"subject" => doc["subject"]}, fn link, data ->
           case {link["type"], link["rel"]} do
@@ -135,11 +138,12 @@ defp webfinger_from_json(doc) do
 
       {:ok, data}
     end
+  end
 
   def get_template_from_xml(body) do
     xpath = "//Link[@rel='lrdd']/@template"
 
-    with doc when doc != :error <- XML.parse_document(body),
+    with {:ok, doc} <- XML.parse_document(body),
          template when template != nil <- XML.string_from_xpath(xpath, doc) do
       {:ok, template}
     end
@@ -192,15 +196,23 @@ def finger(account) do
              address,
              [{"accept", "application/xrd+xml,application/jrd+json"}]
            ),
-         {:ok, %{status: status, body: body}} when status in 200..299 <- response do
+         {:ok, %{status: status, body: body, headers: headers}} when status in 200..299 <-
-      doc = XML.parse_document(body)
+           response do
+      case List.keyfind(headers, "content-type", 0) do
+        {_, content_type} ->
+          case Plug.Conn.Utils.media_type(content_type) do
+            {:ok, "application", subtype, _} when subtype in ~w(xrd+xml xml) ->
+              webfinger_from_xml(body)
 
-      if doc != :error do
+            {:ok, "application", subtype, _} when subtype in ~w(jrd+json json) ->
-        webfinger_from_xml(doc)
+              webfinger_from_json(body)
-      else
+
-        with {:ok, doc} <- Jason.decode(body) do
+            _ ->
-          webfinger_from_json(doc)
+              {:error, {:content_type, content_type}}
           end
+
+        _ ->
+          {:error, {:content_type, nil}}
       end
     else
       e ->

lib/pleroma/web/xml.ex

@@ -31,7 +31,7 @@ def parse_document(text) do
         |> :binary.bin_to_list()
         |> :xmerl_scan.string(quiet: true)
 
-      doc
+      {:ok, doc}
     rescue
       _e ->
         Logger.debug("Couldn't parse XML: #{inspect(text)}")

test/fixtures/tesla_mock/xn--q9jyb4c_host_meta

@@ -1,4 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">
-    <Link rel="lrdd" template="https://zetsubou.xn--q9jyb4c/.well-known/webfinger?resource={uri}" type="application/xrd+xml" />
-</XRD>

test/pleroma/web/web_finger_test.exs

@@ -45,6 +45,26 @@ test "returns error for nonsensical input" do
       assert {:error, _} = WebFinger.finger("pleroma.social")
     end
 
+    test "returns error when there is no content-type header" do
+      Tesla.Mock.mock(fn
+        %{url: "http://social.heldscal.la/.well-known/host-meta"} ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/social.heldscal.la_host_meta")
+           }}
+
+        %{
+          url:
+            "https://social.heldscal.la/.well-known/webfinger?resource=acct:invalid_content@social.heldscal.la"
+        } ->
+          {:ok, %Tesla.Env{status: 200, body: ""}}
+      end)
+
+      user = "invalid_content@social.heldscal.la"
+      assert {:error, {:content_type, nil}} = WebFinger.finger(user)
+    end
+
     test "returns error when fails parse xml or json" do
       user = "invalid_content@social.heldscal.la"
       assert {:error, %Jason.DecodeError{}} = WebFinger.finger(user)
@@ -113,5 +133,52 @@ test "it works with idna domains as link" do
       ap_id = "https://" <> to_string(:idna.encode("zetsubou.みんな")) <> "/users/lain"
       {:ok, _data} = WebFinger.finger(ap_id)
     end
+
+    test "respects json content-type" do
+      Tesla.Mock.mock(fn
+        %{
+          url:
+            "https://mastodon.social/.well-known/webfinger?resource=acct:emelie@mastodon.social"
+        } ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/webfinger_emelie.json"),
+             headers: [{"content-type", "application/jrd+json"}]
+           }}
+
+        %{url: "http://mastodon.social/.well-known/host-meta"} ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/mastodon.social_host_meta")
+           }}
+      end)
+
+      {:ok, _data} = WebFinger.finger("emelie@mastodon.social")
+    end
+
+    test "respects xml content-type" do
+      Tesla.Mock.mock(fn
+        %{
+          url: "https://pawoo.net/.well-known/webfinger?resource=acct:pekorino@pawoo.net"
+        } ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/https___pawoo.net_users_pekorino.xml"),
+             headers: [{"content-type", "application/xrd+xml"}]
+           }}
+
+        %{url: "http://pawoo.net/.well-known/host-meta"} ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/pawoo.net_host_meta")
+           }}
+      end)
+
+      {:ok, _data} = WebFinger.finger("pekorino@pawoo.net")
+    end
   end
 end

test/support/http_request_mock.ex

@@ -122,7 +122,7 @@ def get(
      %Tesla.Env{
        status: 200,
        body: File.read!("test/fixtures/tesla_mock/mike@osada.macgirvin.com.json"),
-       headers: activitypub_object_headers()
+       headers: [{"content-type", "application/jrd+json"}]
      }}
   end
 
@@ -187,7 +187,8 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       body: File.read!("test/fixtures/tesla_mock/lain_squeet.me_webfinger.xml")
+       body: File.read!("test/fixtures/tesla_mock/lain_squeet.me_webfinger.xml"),
+       headers: [{"content-type", "application/xrd+xml"}]
      }}
   end
 
@@ -526,22 +527,6 @@ def get(
      }}
   end
 
-  def get("http://zetsubou.xn--q9jyb4c/.well-known/host-meta", _, _, _) do
-    {:ok,
-     %Tesla.Env{
-       status: 200,
-       body: File.read!("test/fixtures/tesla_mock/xn--q9jyb4c_host_meta")
-     }}
-  end
-
-  def get("https://zetsubou.xn--q9jyb4c/.well-known/host-meta", _, _, _) do
-    {:ok,
-     %Tesla.Env{
-       status: 200,
-       body: File.read!("test/fixtures/tesla_mock/xn--q9jyb4c_host_meta")
-     }}
-  end
-
   def get("http://pleroma.soykaf.com/.well-known/host-meta", _, _, _) do
     {:ok,
      %Tesla.Env{
@@ -786,7 +771,8 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       body: File.read!("test/fixtures/tesla_mock/shp@social.heldscal.la.xml")
+       body: File.read!("test/fixtures/tesla_mock/shp@social.heldscal.la.xml"),
+       headers: [{"content-type", "application/xrd+xml"}]
      }}
   end
 
@@ -796,7 +782,7 @@ def get(
         _,
         [{"accept", "application/xrd+xml,application/jrd+json"}]
       ) do
-    {:ok, %Tesla.Env{status: 200, body: ""}}
+    {:ok, %Tesla.Env{status: 200, body: "", headers: [{"content-type", "application/jrd+json"}]}}
   end
 
   def get("http://framatube.org/.well-known/host-meta", _, _, _) do
@@ -816,7 +802,7 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       headers: [{"content-type", "application/json"}],
+       headers: [{"content-type", "application/jrd+json"}],
        body: File.read!("test/fixtures/tesla_mock/framasoft@framatube.org.json")
      }}
   end
@@ -876,7 +862,7 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       headers: [{"content-type", "application/json"}],
+       headers: [{"content-type", "application/jrd+json"}],
        body: File.read!("test/fixtures/tesla_mock/kaniini@gerzilla.de.json")
      }}
   end
@@ -1074,7 +1060,8 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       body: File.read!("test/fixtures/lain.xml")
+       body: File.read!("test/fixtures/lain.xml"),
+       headers: [{"content-type", "application/xrd+xml"}]
      }}
   end
 
@@ -1087,7 +1074,16 @@ def get(
     {:ok,
      %Tesla.Env{
        status: 200,
-       body: File.read!("test/fixtures/lain.xml")
+       body: File.read!("test/fixtures/lain.xml"),
+       headers: [{"content-type", "application/xrd+xml"}]
+     }}
+  end
+
+  def get("http://zetsubou.xn--q9jyb4c/.well-known/host-meta", _, _, _) do
+    {:ok,
+     %Tesla.Env{
+       status: 200,
+       body: File.read!("test/fixtures/host-meta-zetsubou.xn--q9jyb4c.xml")
      }}
   end
 
@@ -1153,7 +1149,8 @@ def get("https://mstdn.jp/.well-known/webfinger?resource=acct:kpherox@mstdn.jp",
     {:ok,
      %Tesla.Env{
        status: 200,
-       body: File.read!("test/fixtures/tesla_mock/kpherox@mstdn.jp.xml")
+       body: File.read!("test/fixtures/tesla_mock/kpherox@mstdn.jp.xml"),
+       headers: [{"content-type", "application/xrd+xml"}]
      }}
   end