feat: add support for additional request limits

Resolves: cloudfoundry#309

jobs/gorouter/spec

@@ -266,12 +266,44 @@ properties:
       description: "Enforce strict validation of a route service signature"
       default: false
   router.max_header_kb:
+    description: |
+        Deprecated, use router.max_request_header_kb instead which is equivalent to this option.
+    default: 1024 # 1Mb
+  router.max_request_header_kb:
     description: |
         This value controls the maximum number of bytes (in KB) the gorouter will read
         parsing the request header's keys and values, including the request
         line. It does not limit the size of the request body. Requests with
         larger headers will result in a 431 status code. Must be between 1 and 1024kb.
-    default: 1024 # 1Mb
+        Note: This value is called max_header_kb for compatibilty reasons but only
+        affects the request headers and not the response headers. See max_response_header_kb
+        for that.
+        Note: This value takes precedence over router.max_header_kb but has no default to not break
+        existing setups. If you previously configured router.max_header_kb it is recommended to
+        switch to this property instead.
+    example: 1024 # 1Mb
+  router.max_response_header_kb:
+    description: |
+        This value controls the maximum number of bytes (in KB) the gorouter will read
+        parsing the response header's keys and values, including the request
+        line. It does not limit the size of the response body. Responses with
+        larger headers will result in a 502 status code. A limit of zero or less will
+        result in the default GoLang limit being used.
+    default: 0
+  router.max_request_headers:
+    description: |
+        This value controls the maximum number of headers gorouter will accept in a
+        single request. Only the header keys are counted and values separated by commas
+        are not considered additional headers. Setting this to zero or less disables the
+        limit.
+    default: 0
+  router.max_response_headers:
+    description: |
+        This value controls the maximum number of headers gorouter will accept in a
+        single response. Only the header keys are counted and values separated by commas
+        are not considered additional headers. Setting this to zero or less disables the
+        limit.
+    default: 0
   router.extra_headers_to_log:
     description: "An array of headers that access log events will be annotated with. This only applies to headers on requests."
     default: []

jobs/gorouter/templates/gorouter.yml.erb

@@ -28,13 +28,6 @@ def parse_ip (ip, var_name)
   end
 end
 
-def validate_max_header_kb (kb)
-  if kb < 1 or kb > 1024
-    raise "Invalid router.max_header_kb value. Must be between 1 and 1,024 kb"
-  end
-  kb * 1024
-end
-
 def validate_balancing_algorithm (algorithm)
   valid_balancing_algorithms = ['round-robin', 'least-connection']
   unless valid_balancing_algorithms.include?(algorithm)
@@ -82,6 +75,19 @@ def status_tls
   return tls
 end
 
+def max_request_header_bytes
+  # See property description for details.
+  if_p("router.max_request_header_kb") do |kb|
+    return kb * 1024
+  end
+
+  kb = p("router.max_header_kb")
+  if kb < 1 or kb > 1024
+    raise "Invalid router.max_header_kb value. Must be between 1 and 1,024 kb"
+  end
+
+  return kb * 1024
+end
 
 params = {
   'zone' => spec.az,
@@ -145,7 +151,10 @@ params = {
   'route_services_internal_server_port' => p('router.route_services_internal_server_port'),
   'route_services_hairpinning_allowlist' => p('router.route_services_internal_lookup_allowlist'),
   'extra_headers_to_log' => p('router.extra_headers_to_log'),
-  'max_header_bytes' => validate_max_header_kb(p('router.max_header_kb')),
+  'max_request_header_bytes' => max_request_header_bytes,
+  'max_response_header_bytes' => p('router.max_response_header_kb') * 1024,
+  'max_request_headers' => p('router.max_request_headers'),
+  'max_response_headers' => p('router.max_response_headers'),
   'token_fetcher_max_retries' => 3,
   'token_fetcher_retry_interval' => '5s',
   'token_fetcher_expiration_buffer_time' => 30,

spec/gorouter_templates_spec.rb

@@ -302,9 +302,30 @@
         end
       end
 
-      describe 'max_header_kb' do
-        it 'should set max_header_kb' do
-          expect(parsed_yaml['max_header_bytes']).to eq(1_048_576)
+      describe 'max_(request_)header_kb' do
+        context 'as a default' do
+          it 'should set max_request_header_bytes' do
+            expect(parsed_yaml['max_request_header_bytes']).to eq(1_048_576)
+          end
+        end
+
+        context 'when only max_header_kb is set' do
+          before do
+            deployment_manifest_fragment['router']['max_header_kb'] = 10
+          end
+          it 'should set max_request_header_bytes according to it' do
+            expect(parsed_yaml['max_request_header_bytes']).to eq(10_240)
+          end
+        end
+
+        context 'when max_header_kb and max_request_header_kb are set' do
+          before do
+            deployment_manifest_fragment['router']['max_header_kb'] = 10
+            deployment_manifest_fragment['router']['max_request_header_kb'] = 20
+          end
+          it 'should set max_request_header_bytes according to max_request_header_kb' do
+            expect(parsed_yaml['max_request_header_bytes']).to eq(20_480)
+          end
         end
       end