fix(forward-auth): clear configured upstream headers not present in auth response (#13183)

Author: shreemaan-abhishek

apisix/plugins/forward-auth.lua

@@ -184,12 +184,12 @@ function _M.access(conf, ctx)
         return res.status, res.body
     end
 
-    -- append headers that need to be get from the auth response header
+    -- set headers from the auth response, clearing any client-supplied values
+    -- for configured headers not present in the auth response
     for _, header in ipairs(conf.upstream_headers) do
         local header_value = res.headers[header]
-        if header_value then
-            core.request.set_header(ctx, header, header_value)
-        end
+        -- if header_value is nil, the client header's value will be removed if it exists
+        core.request.set_header(ctx, header, header_value)
     end
 end
 

t/plugin/forward-auth3.t

@@ -0,0 +1,107 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+use t::APISIX 'no_plan';
+
+repeat_each(1);
+no_long_string();
+no_root_location();
+
+add_block_preprocessor(sub {
+    my ($block) = @_;
+
+    if (!defined $block->request) {
+        $block->set_value("request", "GET /t");
+    }
+});
+
+run_tests();
+
+__DATA__
+
+=== TEST 1: setup routes
+--- config
+    location /t {
+        content_by_lua_block {
+            local data = {
+                {
+                    url = "/apisix/admin/upstreams/u1",
+                    data = [[{
+                        "nodes": {
+                            "127.0.0.1:1984": 1
+                        },
+                        "type": "roundrobin"
+                    }]],
+                },
+                {
+                    url = "/apisix/admin/routes/auth",
+                    data = {
+                        plugins = {
+                            ["serverless-pre-function"] = {
+                                phase = "rewrite",
+                                functions =  {
+                                    [[return function(conf, ctx)
+                                        local core = require("apisix.core")
+                                        -- auth succeeds without setting X-User-ID
+                                        core.response.exit(200)
+                                    end]]
+                                }
+                            }
+                        },
+                        uri = "/auth"
+                    },
+                },
+                {
+                    url = "/apisix/admin/routes/1",
+                    data = [[{
+                        "plugins": {
+                            "forward-auth": {
+                                "uri": "http://127.0.0.1:1984/auth",
+                                "upstream_headers": ["X-User-ID"]
+                            },
+                            "serverless-post-function": {
+                                "phase": "access",
+                                "functions": [
+                                    "return function(conf, ctx) local core = require(\"apisix.core\"); core.response.exit(200, core.request.headers(ctx)); end"
+                                ]
+                            }
+                        },
+                        "upstream_id": "u1",
+                        "uri": "/hello"
+                    }]],
+                }
+            }
+
+            local t = require("lib.test_admin").test
+
+            for _, data in ipairs(data) do
+                local code, body = t(data.url, ngx.HTTP_PUT, data.data)
+                ngx.say(body)
+            end
+        }
+    }
+--- response_body eval
+"passed\n" x 3
+
+
+
+=== TEST 2: client-supplied upstream_headers are cleared when auth response omits them
+--- request
+GET /hello
+--- more_headers
+X-User-ID: injected-value
+--- response_body_unlike eval
+qr/x-user-id/