Different rate limits depending on HTTP method (#5555)

Author: dsotirho-ucsc

lambdas/service/.chalice/config.json.template.py

@@ -35,6 +35,7 @@
             "lambda_functions": {
                 "api_handler": chalice.vpc_lambda_config(app_name),
                 service.generate_manifest.name: {
+                    "reserved_concurrency": 10,
                     "lambda_timeout": config.service_lambda_timeout
                 },
                 service.update_health_cache.name: {

src/azul/__init__.py

@@ -1503,6 +1503,8 @@ def docker_images(self) -> dict[str, str]:
 
     waf_rate_rule_name = 'RateRule'
 
+    waf_expensive_rate_rule_name = 'ExpensiveRateRule'
+
 
 config: Config = Config()  # yes, the type hint does help PyCharm
 

terraform/api_gateway.tf.json.template.py

@@ -204,6 +204,34 @@ def for_domain(cls, domain):
                     'rule': [
                         {
                             'priority': 0,
+                            'name': 'LabelPostRequests',
+                            'action': {
+                                'count': {}
+                            },
+                            'rule_label': {
+                                'name': 'azul:expensive'
+                            },
+                            'statement': {
+                                'byte_match_statement': {
+                                    'field_to_match': {
+                                        'method': {}
+                                    },
+                                    'positional_constraint': 'EXACTLY',
+                                    'search_string': 'POST',
+                                    'text_transformation': {
+                                        'priority': 0,
+                                        'type': 'NONE'
+                                    }
+                                }
+                            },
+                            'visibility_config': {
+                                'metric_name': 'LabelPostRequests',
+                                'sampled_requests_enabled': True,
+                                'cloudwatch_metrics_enabled': True
+                            }
+                        },
+                        {
+                            'priority': 1,
                             'name': 'BlockedIPs',
                             'action': {
                                 'block': {}
@@ -220,15 +248,39 @@ def for_domain(cls, domain):
                             }
                         },
                         {
-                            'priority': 1,
+                            'priority': 2,
+                            'name': config.waf_expensive_rate_rule_name,
+                            'action': {
+                                'block': {}
+                            },
+                            'statement': {
+                                'rate_based_statement': {
+                                    'limit': 100,  # limit must be between 100 and 20,000,000
+                                    'aggregate_key_type': 'IP',
+                                    'scope_down_statement': {
+                                        'label_match_statement': {
+                                            'scope': 'LABEL',
+                                            'key': 'azul:expensive'
+                                        }
+                                    }
+                                }
+                            },
+                            'visibility_config': {
+                                'metric_name': config.waf_expensive_rate_rule_name,
+                                'sampled_requests_enabled': True,
+                                'cloudwatch_metrics_enabled': True
+                            }
+                        },
+                        {
+                            'priority': 3,
                             'name': config.waf_rate_rule_name,
                             'action': {
                                 'block': {}
                             },
                             'statement': {
                                 'rate_based_statement': {
                                     'limit': 1000,  # limit must be between 100 and 20,000,000
-                                    'aggregate_key_type': 'IP'
+                                    'aggregate_key_type': 'IP',
                                 }
                             },
                             'visibility_config': {
@@ -238,7 +290,7 @@ def for_domain(cls, domain):
                             }
                         },
                         {
-                            'priority': 2,
+                            'priority': 4,
                             'name': 'AWS-CommonRuleSet',
                             'override_action': {
                                 'none': {}
@@ -274,7 +326,7 @@ def for_domain(cls, domain):
                             }
                         },
                         {
-                            'priority': 3,
+                            'priority': 5,
                             'name': 'AWS-AmazonIpReputationList',
                             'override_action': {
                                 'none': {}
@@ -292,7 +344,7 @@ def for_domain(cls, domain):
                             }
                         },
                         {
-                            'priority': 4,
+                            'priority': 6,
                             'name': 'AWS-UnixRuleSet',
                             'override_action': {
                                 'none': {}

terraform/cloudwatch.tf.json.template.py

@@ -367,6 +367,25 @@ def prod_qualified_resource_name(name: str) -> str:
                             },
                             'alarm_actions': ['${data.aws_sns_topic.monitoring.arn}'],
                             'ok_actions': ['${data.aws_sns_topic.monitoring.arn}'],
+                        },
+                        'waf_expensive_rate_blocked': {
+                            'alarm_name': config.qualified_resource_name('waf_expensive_rate_blocked'),
+                            'comparison_operator': 'GreaterThanThreshold',
+                            'threshold': 0,
+                            'datapoints_to_alarm': 1,
+                            'evaluation_periods': 1,
+                            'period': 5 * 60,
+                            'metric_name': 'BlockedRequests',
+                            'namespace': 'AWS/WAFV2',
+                            'statistic': 'Sum',
+                            'treat_missing_data': 'notBreaching',
+                            'dimensions': {
+                                'WebACL': '${aws_wafv2_web_acl.api_gateway.name}',
+                                'Region': config.region,
+                                'Rule': config.waf_expensive_rate_rule_name
+                            },
+                            'alarm_actions': ['${data.aws_sns_topic.monitoring.arn}'],
+                            'ok_actions': ['${data.aws_sns_topic.monitoring.arn}'],
                         }
                     }
                 }