Convert existing CORS module into a policy

apicast/src/policy/cors.lua

@@ -0,0 +1,83 @@
+--- CORS policy
+-- This policy enables CORS (Cross Origin Resource Sharing) request handling.
+-- The policy is configurable. Users can specify the values for the following
+-- headers in the response:
+--   - Access-Control-Allow-Headers
+--   - Access-Control-Allow-Methods
+--   - Access-Control-Allow-Origin
+--   - Access-Control-Allow-Credentials
+-- By default, those headers are set so all the requests are allowed. For
+-- example, if the request contains the 'Origin' header set to 'example.com',
+-- by default, 'Access-Control-Allow-Origin' in the response will be set to
+-- 'example.com' too.
+
+local policy = require('policy')
+local _M = policy.new('CORS Policy')
+
+local new = _M.new
+
+--- Initialize a CORS policy
+-- @tparam[opt] table config
+-- @field[opt] allow_headers Table with the allowed headers (e.g. Content-Type)
+-- @field[opt] allow_methods Table with the allowed methods (GET, POST, etc.)
+-- @field[opt] allow_origin Allowed origins (e.g. 'http://example.com', '*')
+-- @field[opt] allow_credentials Boolean
+function _M.new(config)
+  local self = new()
+  self.config = config or {}
+  return self
+end
+
+local function set_access_control_allow_headers(allow_headers)
+  local value = allow_headers or ngx.var.http_access_control_request_headers
+  ngx.header['Access-Control-Allow-Headers'] = value
+end
+
+local function set_access_control_allow_methods(allow_methods)
+  local value = allow_methods or ngx.var.http_access_control_request_method
+  ngx.header['Access-Control-Allow-Methods'] = value
+end
+
+local function set_access_control_allow_origin(allow_origin, default)
+  ngx.header['Access-Control-Allow-Origin'] = allow_origin or default
+end
+
+local function set_access_control_allow_credentials(allow_credentials)
+  local value = allow_credentials
+  if value == nil then value = 'true' end
+  ngx.header['Access-Control-Allow-Credentials'] = value
+end
+
+local function set_cors_headers(config)
+  local origin = ngx.var.http_origin
+  if not origin then return end
+
+  set_access_control_allow_headers(config.allow_headers)
+  set_access_control_allow_methods(config.allow_methods)
+  set_access_control_allow_origin(config.allow_origin, origin)
+  set_access_control_allow_credentials(config.allow_credentials)
+end
+
+local function cors_preflight_response(config)
+  set_cors_headers(config)
+  ngx.status = 204
+  ngx.exit(ngx.status)
+end
+
+local function is_cors_preflight()
+  return ngx.req.get_method() == 'OPTIONS' and
+         ngx.var.http_origin and
+         ngx.var.http_access_control_request_method
+end
+
+function _M:rewrite()
+  if is_cors_preflight() then
+    return cors_preflight_response(self.config)
+  end
+end
+
+function _M:header_filter()
+  set_cors_headers(self.config)
+end
+
+return _M

t/apicast-policy-cors.t

@@ -0,0 +1,165 @@
+use lib 't';
+use TestAPIcastBlackbox 'no_plan';
+
+repeat_each(1);
+run_tests();
+
+__DATA__
+
+=== TEST 1: CORS preflight request
+Returns 204 and sets the appropriate headers.
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "backend_version":  1,
+      "backend_authentication_type": "service_token",
+      "backend_authentication_value": "token-value",
+      "proxy": {
+        "policy_chain": [
+          { "name": "policy.cors" },
+          { "name": "apicast" }
+        ],
+        "api_backend": "http://test:$TEST_NGINX_SERVER_PORT/",
+        "proxy_rules": [
+          { "pattern": "/", "http_method": "GET", "metric_system_name": "hits", "delta": 2 }
+        ]
+      }
+    }
+  ]
+}
+--- request
+OPTIONS /
+--- more_headers
+Origin: localhost
+Access-Control-Request-Method: GET
+--- error_code: 204
+--- no_error_log
+[error]
+
+=== TEST 2: CORS actual request with default config
+This tests a CORS actual (not preflight) request. The only difference with a
+non-CORS request is that the CORS headers will be included in the response.
+In this test, we are not using a custom config for the CORS policy. This means
+that the response will contain the default CORS headers. By default, all of
+them (allow-headers, allow-methods, etc.) simply match the headers received in
+the request. So for example, if the request sets the 'Origin' header to
+'example.com' the response will set 'Access-Control-Allow-Origin' to
+'example.com'.
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "backend_version":  1,
+      "backend_authentication_type": "service_token",
+      "backend_authentication_value": "token-value",
+      "proxy": {
+        "policy_chain": [
+          { "name": "policy.cors" },
+          { "name": "apicast" }
+        ],
+        "api_backend": "http://test:$TEST_NGINX_SERVER_PORT/",
+        "proxy_rules": [
+          { "pattern": "/", "http_method": "GET", "metric_system_name": "hits", "delta": 2 }
+        ]
+      }
+    }
+  ]
+}
+--- backend
+  location /transactions/authrep.xml {
+    content_by_lua_block {
+      local expected = "service_token=token-value&service_id=42&usage%5Bhits%5D=2&user_key=value"
+      local args = ngx.var.args
+      if args == expected then
+        ngx.exit(200)
+      else
+        ngx.log(ngx.ERR, expected, ' did not match: ', args)
+        ngx.exit(403)
+      end
+    }
+  }
+--- upstream
+  location / {
+     echo 'yay, api backend: $http_host';
+  }
+--- request
+GET /?user_key=value
+--- more_headers
+Origin: http://example.com
+Access-Control-Request-Method: GET
+Access-Control-Request-Headers: Content-Type
+--- response_body
+yay, api backend: test
+--- response_headers
+Access-Control-Allow-Headers: Content-Type
+Access-Control-Allow-Methods: GET
+Access-Control-Allow-Origin: http://example.com
+Access-Control-Allow-Credentials: true
+--- error_code: 200
+--- no_error_log
+[error]
+
+=== TEST 3: CORS actual request with custom config
+This tests a CORS actual (not preflight) request. We use a custom config to set
+the CORS headers in the response.
+--- configuration
+{
+  "services": [
+    {
+      "id": 42,
+      "backend_version":  1,
+      "backend_authentication_type": "service_token",
+      "backend_authentication_value": "token-value",
+      "proxy": {
+        "policy_chain": [
+          { "name": "policy.cors",
+            "configuration": { "allow_headers": [ "X-Custom-Header-1", "X-Custom-Header-2" ],
+                               "allow_methods": [ "POST", "GET", "OPTIONS" ],
+                               "allow_origin" : "*",
+                               "allow_credentials": false } },
+          { "name": "apicast" }
+        ],
+        "api_backend": "http://test:$TEST_NGINX_SERVER_PORT/",
+        "proxy_rules": [
+          { "pattern": "/", "http_method": "GET", "metric_system_name": "hits", "delta": 2 }
+        ]
+      }
+    }
+  ]
+}
+--- backend
+  location /transactions/authrep.xml {
+    content_by_lua_block {
+      local expected = "service_token=token-value&service_id=42&usage%5Bhits%5D=2&user_key=value"
+      local args = ngx.var.args
+      if args == expected then
+        ngx.exit(200)
+      else
+        ngx.log(ngx.ERR, expected, ' did not match: ', args)
+        ngx.exit(403)
+      end
+    }
+  }
+--- upstream
+  location / {
+     echo 'yay, api backend: $http_host';
+  }
+--- request
+GET /?user_key=value
+--- more_headers
+Origin: http://example.com
+Access-Control-Request-Method: GET
+Access-Control-Request-Headers: Content-Type
+--- response_body
+yay, api backend: test
+--- response_headers
+Access-Control-Allow-Headers: X-Custom-Header-1, X-Custom-Header-2
+Access-Control-Allow-Methods: POST, GET, OPTIONS
+Access-Control-Allow-Origin: *
+Access-Control-Allow-Credentials: false
+--- error_code: 200
+--- no_error_log
+[error]