feat(router): make header size configurable (#1457)

Author: Noroth

router-tests/graphql_over_http_test.go

@@ -2,12 +2,16 @@ package integration
 
 import (
 	"bytes"
+
 	"io"
 	"net/http"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 	"github.com/wundergraph/cosmo/router-tests/testenv"
+	"github.com/wundergraph/cosmo/router/core"
+	"github.com/wundergraph/cosmo/router/pkg/config"
 )
 
 func TestGraphQLOverHTTPCompatibility(t *testing.T) {
@@ -196,5 +200,43 @@ func TestGraphQLOverHTTPCompatibility(t *testing.T) {
 			require.NoError(t, err)
 			require.Equal(t, `{"data":{"findEmployees":[{"id":1,"details":{"forename":"Jens","surname":"Neuse"}},{"id":2,"details":{"forename":"Dustin","surname":"Deus"}},{"id":4,"details":{"forename":"Björn","surname":"Schwenzer"}},{"id":11,"details":{"forename":"Alexandra","surname":"Neuse"}}]}}`, string(data))
 		})
+		t.Run("request with long header should return 431 response", func(t *testing.T) {
+			header := http.Header{}
+
+			// the limit actually behaves a bit weird in the http library. It's not exactly 1<<20 (1MiB)
+			// It also has some threshold added, and when running all tests at the same time the limit goes even higher.
+			// I couldn't figure out why, so I just go way beyond the limit to make sure it fails.
+			header.Add("X-Long-Header", strings.Repeat("abc", http.DefaultMaxHeaderBytes)) // 3MB
+
+			body := []byte(`{"query":"query Find($criteria: SearchInput!) {findEmployees(criteria: $criteria){id details {forename surname}}}","variables":{"criteria":{"nationality":"GERMAN"}},"operationName":"Find"}`)
+			res, err := xEnv.MakeRequest("POST", "/graphql", header, bytes.NewReader(body))
+			require.NoError(t, err)
+			require.Equal(t, http.StatusRequestHeaderFieldsTooLarge, res.StatusCode)
+		})
+	})
+
+	t.Run("request with long header and updated max size should return 200 response", func(t *testing.T) {
+		t.Parallel()
+		testenv.Run(t, &testenv.Config{
+			RouterOptions: []core.Option{
+				core.WithRouterTrafficConfig(&config.RouterTrafficConfiguration{
+					MaxHeaderBytes:      4 << 20, // 4MiB
+					MaxRequestBodyBytes: 5 << 20, // 5MiB
+				}),
+			},
+		}, func(t *testing.T, xEnv *testenv.Environment) {
+			header := http.Header{
+				"Content-Type": []string{"application/json"},
+				"Accept":       []string{"application/json"},
+			}
+
+			header.Add("X-Long-Header", strings.Repeat("abc", http.DefaultMaxHeaderBytes)) // 3MB
+
+			body := []byte(`{"query":"query Find($criteria: SearchInput!) {findEmployees(criteria: $criteria){id details {forename surname}}}","variables":{"criteria":{"nationality":"GERMAN"}},"operationName":"Find"}`)
+
+			res, err := xEnv.MakeRequest("POST", "/graphql", header, bytes.NewReader(body))
+			require.NoError(t, err)
+			require.Equal(t, http.StatusOK, res.StatusCode)
+		})
 	})
 }

router/core/http_server.go

@@ -29,6 +29,7 @@ type httpServerOptions struct {
 	tlsServerConfig *tls.Config
 	healthcheck     health.Checker
 	baseURL         string
+	maxHeaderBytes  int
 }
 
 func newServer(opts *httpServerOptions) *server {
@@ -37,9 +38,10 @@ func newServer(opts *httpServerOptions) *server {
 		ReadTimeout: 60 * time.Second,
 		// Disable write timeout to keep the connection open until the client closes it
 		// This is required for SSE (Server-Sent-Events) subscriptions to work correctly
-		WriteTimeout: 0,
-		ErrorLog:     zap.NewStdLog(opts.logger),
-		TLSConfig:    opts.tlsServerConfig,
+		WriteTimeout:   0,
+		ErrorLog:       zap.NewStdLog(opts.logger),
+		TLSConfig:      opts.tlsServerConfig,
+		MaxHeaderBytes: opts.maxHeaderBytes,
 	}
 
 	n := &server{

router/core/router.go

@@ -710,6 +710,7 @@ func (r *Router) NewServer(ctx context.Context) (Server, error) {
 		tlsServerConfig: r.tlsServerConfig,
 		healthcheck:     r.healthcheck,
 		baseURL:         r.baseURL,
+		maxHeaderBytes:  int(r.routerTrafficConfig.MaxHeaderBytes.Uint64()),
 	})
 
 	// Start the server with the static config without polling
@@ -1044,6 +1045,7 @@ func (r *Router) Start(ctx context.Context) error {
 		tlsServerConfig: r.tlsServerConfig,
 		healthcheck:     r.healthcheck,
 		baseURL:         r.baseURL,
+		maxHeaderBytes:  int(r.routerTrafficConfig.MaxHeaderBytes.Uint64()),
 	})
 
 	// Start the server with the static config without polling
@@ -1779,12 +1781,6 @@ func WithCacheWarmupConfig(cfg *config.CacheWarmupConfiguration) Option {
 	}
 }
 
-func WithHostName(hostName string) Option {
-	return func(r *Router) {
-		r.hostName = hostName
-	}
-}
-
 type ProxyFunc func(req *http.Request) (*url.URL, error)
 
 func newHTTPTransport(opts TransportTimeoutOptions, proxy ProxyFunc) *http.Transport {

router/pkg/config/config.go

@@ -152,6 +152,8 @@ type FileUpload struct {
 type RouterTrafficConfiguration struct {
 	// MaxRequestBodyBytes is the maximum size of the request body in bytes
 	MaxRequestBodyBytes BytesString `yaml:"max_request_body_size" envDefault:"5MB"`
+	// MaxHeaderBytes is the maximum size of the request headers in bytes
+	MaxHeaderBytes BytesString `yaml:"max_header_bytes" envDefault:"0MiB" env:"MAX_HEADER_BYTES"`
 }
 
 type GlobalSubgraphRequestRule struct {

router/pkg/config/config.schema.json

@@ -1162,6 +1162,12 @@
                 "minimum": "1MB"
               },
               "description": "The maximum request body size. The size is specified as a string with a number and a unit, e.g. 10KB, 1MB, 1GB. The supported units are 'KB', 'MB', 'GB'."
+            },
+            "max_header_bytes": {
+              "type": "string",
+              "description": "The maximum size of the request headers. Setting this to 0 uses the default value from the http standard lib, which is 1MiB.",
+              "default": "0MiB",
+              "bytes": {}
             }
           }
         },

router/pkg/config/fixtures/full.yaml

@@ -146,6 +146,7 @@ traffic_shaping:
   router:
     # Is the maximum size of the request body in MB, mib
     max_request_body_size: 5MB
+    max_header_bytes: 4MiB
   all: # Rules are applied to all subgraph requests.
     # Subgraphs transport options
     request_timeout: 60s

router/pkg/config/testdata/config_defaults.json

@@ -118,7 +118,8 @@
       "KeepAliveProbeInterval": 30000000000
     },
     "Router": {
-      "MaxRequestBodyBytes": 5000000
+      "MaxRequestBodyBytes": 5000000,
+      "MaxHeaderBytes": 0
     },
     "Subgraphs": null
   },

router/pkg/config/testdata/config_full.json

@@ -242,7 +242,8 @@
       "KeepAliveProbeInterval": 30000000000
     },
     "Router": {
-      "MaxRequestBodyBytes": 5000000
+      "MaxRequestBodyBytes": 5000000,
+      "MaxHeaderBytes": 4194304
     },
     "Subgraphs": {
       "products": {