feat: tell httpc to close the connection if we're using client certs

In addition to the separate profile, this header serves as a note to
both the remote server and `httpc` that we're not keeping the connection
open after the request.`

src/oidcc_http_util.erl

@@ -85,17 +85,32 @@ when
             Accumulator :: term()},
     TelemetryOpts :: telemetry_opts(),
     RequestOpts :: request_opts().
-request(Method, Request, TelemetryOpts, RequestOpts) ->
+request(Method, Request0, TelemetryOpts, RequestOpts) ->
     TelemetryTopic = maps:get(topic, TelemetryOpts),
     TelemetryExtraMeta = maps:get(extra_meta, TelemetryOpts, #{}),
     Timeout = maps:get(timeout, RequestOpts, timer:minutes(1)),
     SslOpts = maps:get(ssl, RequestOpts, undefined),
 
     HttpOpts0 = [{timeout, Timeout}],
-    {HttpOpts, HttpProfile} =
+    HttpOpts =
         case SslOpts of
-            undefined -> {HttpOpts0, default};
-            _Opts -> {[{ssl, SslOpts} | HttpOpts0], oidcc_app:httpc_profile()}
+            undefined -> HttpOpts0;
+            _Opts -> [{ssl, SslOpts} | HttpOpts0]
+        end,
+
+    %% if we're using special SSL opts, always close the connection after we're
+    %% done. we do this to work around an issue with httpc where it doesn't take
+    %% the client certificates into account when pipelining, so if the HTTP
+    %% implementation changes we should think about undoing this.
+    {Request, HttpProfile} =
+        case using_client_certificate(SslOpts) of
+            false ->
+                {Request0, default};
+            true ->
+                ReqHeaders0 = element(2, Request0),
+                ReqHeaders1 = [{"connection", "close"} | ReqHeaders0],
+                ReqHeaders = lists:ukeysort(1, ReqHeaders1),
+                {setelement(2, Request0, ReqHeaders), oidcc_app:httpc_profile()}
         end,
 
     telemetry:span(
@@ -166,3 +181,21 @@ fetch_content_type(Headers) ->
         _Other ->
             unknown
     end.
+
+-spec using_client_certificate([ssl:tls_client_option()] | undefined) -> boolean().
+using_client_certificate(undefined) ->
+    false;
+using_client_certificate(SslOpts) ->
+    lists:foldl(
+        fun
+            (_, true) -> true;
+            ({key, _}, _) -> true;
+            ({keyfile, _}, _) -> true;
+            ({cert, _}, _) -> true;
+            ({certfile, _}, _) -> true;
+            ({certs_keys, _}, _) -> true;
+            (_, Acc) -> Acc
+        end,
+        false,
+        SslOpts
+    ).

test/oidcc_http_util_SUITE.erl

@@ -73,6 +73,19 @@ client_cert(_Config) ->
             keyfile => KeyFile
         }
     ],
+
+    ?assertMatch(
+        {error, {http_error, 403, <<"">>}},
+        oidcc_http_util:request(
+            get, {"https://certauth.idrix.fr/json/", []}, telemetry_opts(), #{
+                ssl => [
+                    {verify, verify_peer},
+                    {cacerts, public_key:cacerts_get()}
+                ]
+            }
+        )
+    ),
+
     ?assertMatch(
         {ok, {
             {json, #{