Advanced API security for Kubernetes containers running in AWS - NGINX App Protect per-service deployment through a CI/CD pipeline
Introduction
When the design objective for Kubernetes security is the separate management of WAF security policies, the solution is NGINX App Protect deployed per-service. This article describes such a deployment, with NGINX App Protect augmenting AWS API Gateway to provide advanced security to API workloads, deployed through a CI/CD pipeline. The advantage of NGINX App Protect deployed per-service in a Kubernetes environment is the separation of security policies between different services, allowing for better customisation of the policies and easier portability to different environments.
In this particular instance, I used a demo application, Arcadia Finance, that has a Web interface and also exposes an API allowing the users to make financial transactions. The API is described in an OpenAPI 3.0 file, allowing for the automated building of the positive security policy elements (allow list elements) whereas in the case of the web security policy, this configuration will be done manually.
The difference in configuration methods between the API and Web policies and the additional requirement for policy separation and independent portability between environments prompted the usage of two separate NGINX App Protect instance, each securing their respective service (Web and API).
The deployment used AWS EKS as Kubernetes environment where, beside the Arcadia Finance application components and NGINX App Protect instances, there is also a Fluentd deployment configured as a Syslog server for security logs sent by the NGINX App Protect instances. The logs are then being sent to AWS Elasticsearch and displayed via Kibana NGINX App Protect dashboards.
Access to EKS cluster is being provided by an NGINX Ingress Controller instance. The Web interface is being exposed externally through an AWS Application LoadBalancer, handling the SSL offloading while the API is exposed through a Network LoadBalancer. The API is published externally through AWS API Gateway, providing basic security, using a VPC link to connect to the Network LoadBalancer.
The configuration
The configuration (Arcadia Finance deployment, NGINX KIC, NGINX App Protect configuration, OpenAPI file) is being stored in AWS CodeComit and deployed through AWS CodePipeline and AWS CodeBuild.
The API Gateway configuration is being described in an OpenAPI file annotated for AWS API Gateway-specific elements:
{
"openapi" : "3.0.1",
"info" : {
"title" : "API Arcadia Finance",
"description" : "Arcadia OpenAPI",
"version" : "1.0.0-oas3"
},
"servers" : [ {
"url" : "https://api.cloud-app.uk"
} ],
"paths" : {
"/api/rest/execute_money_transfer.php" : {
"post" : {
"requestBody" : {
"content" : {
"application/json" : {
"schema" : {
"$ref" : "#/components/schemas/MODEL9e8bc4"
}
}
},
"required" : true
},
"responses" : {
"200" : {
"description" : "200 response",
"content" : { }
}
},
"x-amazon-apigateway-request-validator": "Validate body, query string parameters, and headers",
"x-amazon-apigateway-gateway-responses": {
"BAD_REQUEST_BODY": {
"responseTemplates": {
"application/json": "{\"message\": \"Bla Bla\"}"
}
}
},
"x-amazon-apigateway-integration" : {
"type" : "http_proxy",
"uri" : "http://api.cloud-app.uk/api/rest/execute_money_transfer.php",
"responses" : {
"default" : {
"statusCode" : "200"
}
},
"passthroughBehavior" : "when_no_match",
"connectionType" : "VPC_LINK",
"connectionId" : "emda4d",
"httpMethod" : "POST"
}
}
},
"/trading/transactions.php" : {
"get" : {
"responses" : {
"200" : {
"description" : "200 response",
"content" : { }
}
},
"x-amazon-apigateway-request-validator": "Validate body, query string parameters, and headers",
"x-amazon-apigateway-gateway-responses": {
"BAD_REQUEST_BODY": {
"responseTemplates": {
"application/json": "{\"message\": \"$context.error.validationErrorString\"}"
}
}
},
"x-amazon-apigateway-integration" : {
"type" : "http_proxy",
"uri" : "http://www.cloud-app.uk/trading/transactions.php",
"responses" : {
"default" : {
"statusCode" : "200"
}
},
"passthroughBehavior" : "when_no_match",
"connectionType" : "VPC_LINK",
"connectionId" : "emda4d",
"httpMethod" : "GET"
}
}
},
"/trading/rest/sell_stocks.php" : {
"post" : {
"requestBody" : {
"content" : {
"application/json" : {
"schema" : {
"$ref" : "#/components/schemas/MODEL1ed7ad"
}
}
},
"required" : true
},
"responses" : {
"200" : {
"description" : "200 response",
"content" : { }
}
},
"x-amazon-apigateway-request-validator": "Validate body, query string parameters, and headers",
"x-amazon-apigateway-gateway-responses": {
"BAD_REQUEST_BODY": {
"responseTemplates": {
"application/json": "{\"message\": \"$context.error.validationErrorString\"}"
}
}
},
"x-amazon-apigateway-integration" : {
"type" : "http_proxy",
"uri" : "http://api.cloud-app.uk/trading/rest/sell_stocks.php",
"responses" : {
"default" : {
"statusCode" : "200"
}
},
"passthroughBehavior" : "when_no_match",
"connectionType" : "VPC_LINK",
"connectionId" : "emda4d",
"httpMethod" : "POST"
}
}
},
"/trading/rest/buy_stocks.php" : {
"post" : {
"requestBody" : {
"content" : {
"application/json" : {
"schema" : {
"$ref" : "#/components/schemas/MODEL94f81c"
}
}
},
"required" : true
},
"responses" : {
"200" : {
"description" : "200 response",
"content" : { }
}
},
"x-amazon-apigateway-request-validator": "Validate body, query string parameters, and headers",
"x-amazon-apigateway-gateway-responses": {
"BAD_REQUEST_BODY": {
"responseTemplates": {
"application/json": "{\"message\": \"$context.error.validationErrorString\"}"
}
}
},
"x-amazon-apigateway-integration" : {
"type" : "http_proxy",
"uri" : "http://api.cloud-app.uk/trading/rest/buy_stocks.php",
"responses" : {
"default" : {
"statusCode" : "200"
}
},
"passthroughBehavior" : "when_no_match",
"connectionType" : "VPC_LINK",
"connectionId" : "emda4d",
"httpMethod" : "POST"
}
}
}
},
"components" : {
"schemas" : {
"MODEL94f81c" : {
"required" : [ "action", "company", "qty", "stock_price", "trans_value" ],
"type" : "object",
"properties" : {
"trans_value" : {
"minimum" : 0,
"type" : "number"
},
"qty" : {
"minimum" : 0,
"type" : "integer",
"format" : "int32"
},
"company" : {
"type" : "string"
},
"action" : {
"type" : "string",
"enum" : [ "buy" ]
},
"stock_price" : {
"minimum" : 0,
"type" : "number"
}
},
"additionalProperties" : false
},
"MODEL1ed7ad" : {
"required" : [ "action", "company", "qty", "stock_price", "trans_value" ],
"type" : "object",
"properties" : {
"trans_value" : {
"minimum" : 0,
"type" : "number"
},
"qty" : {
"minimum" : 0,
"type" : "integer",
"format" : "int32"
},
"company" : {
"type" : "string"
},
"action" : {
"type" : "string",
"enum" : [ "sell" ]
},
"stock_price" : {
"minimum" : 0,
"type" : "number"
}
},
"additionalProperties" : false
},
"MODEL9e8bc4" : {
"required" : [ "account", "amount", "currency", "friend" ],
"type" : "object",
"properties" : {
"amount" : {
"minimum" : 0,
"type" : "number"
},
"account" : {
"type" : "number"
},
"currency" : {
"type" : "string"
},
"friend" : {
"type" : "string"
}
},
"additionalProperties" : false
}
}
},
"x-amazon-apigateway-policy" : {
"Version" : "2012-10-17",
"Statement" : [ {
"Effect" : "Allow",
"Principal" : "*",
"Action" : "execute-api:Invoke",
"Resource" : "arn:aws:execute-api:us-west-2:856265587682:7g8sbh9zs6/*"
} ]
},
"x-amazon-apigateway-request-validators": {
"Validate body, query string parameters, and headers": {
"validateRequestParameters": true,
"validateRequestBody": true
}
}
}
The Ingress objects controlled by NGINX KIC are responsible for steering the traffic to either the Web or API instances of NGINX App Protect:
apiVersion: extensions/v1beta1 kind: Ingress metadata: annotations: kubernetes.io/ingress.class: nginx name: arcadia-nginx-kic namespace: default spec: rules: - host: "*.cloud-app.uk" http: paths: - backend: serviceName: api-nap servicePort: 80 path: /api/rest/execute_money_transfer.php - backend: serviceName: api-nap servicePort: 80 path: /trading/rest/buy_stocks.php - backend: serviceName: api-nap servicePort: 80 path: /trading/rest/sell_stocks.php - backend: serviceName: web-nap servicePort: 80 path: /trading/transactions.php - backend: serviceName: web-nap servicePort: 80 path: / - backend: serviceName: web-nap servicePort: 80 path: /files - backend: serviceName: web-nap servicePort: 80 path: /api - backend: serviceName: web-nap servicePort: 80 path: /app3
The NGINX App Protect configuration is also controlled by AWS CodePipeline, deployed as a ConfigMap and mounted as a volume on the NGINX instance:
apiVersion: v1
kind: ConfigMap
metadata:
name: nginx-conf-map-api
namespace: default
data:
nginx.conf: |+
user nginx;
worker_processes auto;
load_module modules/ngx_http_app_protect_module.so;
error_log /var/log/nginx/error.log debug;
events {
worker_connections 10240;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
upstream main_DNS_name {
server main;
}
upstream app2_DNS_name {
server app2;
}
server {
listen 80;
server_name *.cloud-app.uk;
proxy_http_version 1.1;
app_protect_enable on;
app_protect_policy_file "/etc/nginx/NAP_API_Policy.json";
app_protect_security_log_enable on;
app_protect_security_log "/etc/nginx/custom_log_format.json" syslog:server=fluentd.logging.svc.cluster.local:24224;
location /trading {
client_max_body_size 0;
default_type text/html;
# set your backend here
proxy_pass http://main_DNS_name;
proxy_set_header Host $host;
}
location /api {
client_max_body_size 0;
default_type text/html;
# set your backend here
proxy_pass http://app2_DNS_name;
proxy_set_header Host $host;
}
}
}
apiVersion: apps/v1 kind: Deployment metadata: name: api-nap labels: app: api-nap spec: selector: matchLabels: app: api-nap replicas: 1 template: metadata: labels: app: api-nap spec: containers: - name: api-nap image: 856265587682.dkr.ecr.us-west-2.amazonaws.com/per-service-nginx-app-protect:latest imagePullPolicy: IfNotPresent ports: - containerPort: 80 volumeMounts: - name: nginx-conf-map-api-volume mountPath: "/etc/nginx/nginx.conf" subPath: "nginx.conf" readOnly: true - name: nap-api-policy-volume mountPath: "/etc/nginx/NAP_API_Policy.json" subPath: "NAP_API_Policy.json" readOnly: true volumes: - name: nginx-conf-map-api-volume configMap: name: nginx-conf-map-api - name: nap-api-policy-volume configMap: name: nap-api-policy
In case of API NGINX App Protect configuration, there is a reference to the OpenAPI file placed by the CI/CD pipeline in an S3 bucket:
apiVersion: v1
kind: ConfigMap
metadata:
name: nap-api-policy
namespace: default
data:
NAP_API_Policy.json: |+
{
"policy": {
"name": "policy_name",
"template": { "name": "POLICY_TEMPLATE_NGINX_BASE" },
"applicationLanguage": "utf-8",
"enforcementMode": "blocking",
"signature-sets": [
{
"name": "High Accuracy Signatures",
"block": true,
"alarm": true
}
],
"bot-defense": {
"settings": {
"isEnabled": true
},
"mitigations": {
"classes": [
{
"name": "trusted-bot",
"action": "alarm"
},
{
"name": "untrusted-bot",
"action": "block"
},
{
"name": "malicious-bot",
"action": "block"
}
]
}
},
"open-api-files": [
{
"link": "https://per-service-nginx-app-protect.s3.us-west-2.amazonaws.com/arcadia-openapi3-aws.json"
}
],
"blocking-settings": {
"violations": [
{
"name": "VIOL_JSON_FORMAT",
"alarm": true,
"block": true
},
{
"name": "VIOL_PARAMETER_VALUE_METACHAR",
"alarm": false,
"block": false
},
{
"name": "VIOL_HTTP_PROTOCOL",
"alarm": true,
"block": true
},
{
"name": "VIOL_EVASION",
"alarm": true,
"block": true
},
{
"name": "VIOL_FILETYPE",
"alarm": true,
"block": true
},
{
"name": "VIOL_METHOD",
"alarm": true,
"block": true
},
{
"block": true,
"description": "Disallowed file upload content detected in body",
"name": "VIOL_FILE_UPLOAD_IN_BODY"
},
{
"block": true,
"description": "Mandatory request body is missing",
"name": "VIOL_MANDATORY_REQUEST_BODY"
},
{
"block": true,
"description": "Illegal parameter location",
"name": "VIOL_PARAMETER_LOCATION"
},
{
"block": true,
"description": "Mandatory parameter is missing",
"name": "VIOL_MANDATORY_PARAMETER"
},
{
"block": true,
"description": "JSON data does not comply with JSON schema",
"name": "VIOL_JSON_SCHEMA"
},
{
"block": true,
"description": "Illegal parameter array value",
"name": "VIOL_PARAMETER_ARRAY_VALUE"
},
{
"block": true,
"description": "Illegal Base64 value",
"name": "VIOL_PARAMETER_VALUE_BASE64"
},
{
"block": true,
"description": "Disallowed file upload content detected",
"name": "VIOL_FILE_UPLOAD"
},
{
"block": true,
"description": "Illegal request content type",
"name": "VIOL_URL_CONTENT_TYPE"
},
{
"block": true,
"description": "Illegal static parameter value",
"name": "VIOL_PARAMETER_STATIC_VALUE"
},
{
"block": true,
"description": "Illegal parameter value length",
"name": "VIOL_PARAMETER_VALUE_LENGTH"
},
{
"block": true,
"description": "Illegal parameter data type",
"name": "VIOL_PARAMETER_DATA_TYPE"
},
{
"block": true,
"description": "Illegal parameter numeric value",
"name": "VIOL_PARAMETER_NUMERIC_VALUE"
},
{
"block": true,
"description": "Parameter value does not comply with regular expression",
"name": "VIOL_PARAMETER_VALUE_REGEXP"
},
{
"block": true,
"description": "Illegal URL",
"name": "VIOL_URL"
},
{
"block": true,
"description": "Illegal parameter",
"name": "VIOL_PARAMETER"
},
{
"block": true,
"description": "Illegal empty parameter value",
"name": "VIOL_PARAMETER_EMPTY_VALUE"
},
{
"block": true,
"description": "Illegal repeated parameter name",
"name": "VIOL_PARAMETER_REPEATED"
}
],
"http-protocols": [
{
"description": "Header name with no header value",
"enabled": true
},
{
"description": "Chunked request with Content-Length header",
"enabled": true
},
{
"description": "Check maximum number of parameters",
"enabled": true,
"maxParams": 5
},
{
"description": "Check maximum number of headers",
"enabled": true,
"maxHeaders": 30
},
{
"description": "Body in GET or HEAD requests",
"enabled": true
},
{
"description": "Bad multipart/form-data request parsing",
"enabled": true
},
{
"description": "Bad multipart parameters parsing",
"enabled": true
},
{
"description": "Unescaped space in URL",
"enabled": true
}
],
"evasions": [
{
"description": "Bad unescape",
"enabled": true
},
{
"description": "Directory traversals",
"enabled": true
},
{
"description": "Bare byte decoding",
"enabled": true
},
{
"description": "Apache whitespace",
"enabled": true
},
{
"description": "Multiple decoding",
"enabled": true,
"maxDecodingPasses": 2
},
{
"description": "IIS Unicode codepoints",
"enabled": true
},
{
"description": "%u decoding",
"enabled": true
}
]
},
"methodReference": {
"link": "https://per-service-nginx-app-protect.s3.us-west-2.amazonaws.com/methods.txt"
},
"filetypeReference": {
"link": "https://per-service-nginx-app-protect.s3.us-west-2.amazonaws.com/filetypes.txt"
}
}
}
In this case, the same OpenAPI file is pushed to both AWS API Gateway and, through the S3 bucket, to the NGINX App Protect API instance.
NGINX App Protect augmenting the security provided by AWS API Gateway
The NGINX App Protect API instance enhances the security posture of API Gateway by providing negative security (attack signature matching) and advanced security like bot detection. To demonstrate this functionality, a SQLi attack is simulated against the API.
This valid API call sent by Postman is successfully completed:
A similar call that contains an attack pattern (SQL injection) is being blocked by the NGINX App Protect instance:
To demonstrate the bot detection capability, the same valid call sent before is now sent from Curl (as opposed to Postman used earlier), now matching an untrusted bot signature and being blocked:
curl -vvvk https://api.cloud-app.uk/api/rest/execute_money_transfer.php -d '{"account": 2075894, "amount": 1, "currency": "GBP", "friend": "Vincent"}' -H "Content-Type: application/json" -X POST
Note: Unnecessary use of -X or --request, POST is already inferred.
* Trying 143.204.170.103...
* TCP_NODELAY set
* Connected to api.cloud-app.uk (143.204.170.103) port 443 (#0)
* WARNING: disabling hostname validation also disables SNI.
* TLS 1.2 connection using TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
* Server certificate: *.cloudfront.net
* Server certificate: DigiCert Global CA G2
* Server certificate: DigiCert Global Root G2
> POST /api/rest/execute_money_transfer.php HTTP/1.1
> Host: api.cloud-app.uk
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 73
>
* upload completely sent off: 73 out of 73 bytes
< HTTP/1.1 403 Forbidden
< Content-Type: application/json; charset=utf-8
< Content-Length: 37
< Connection: keep-alive
< Date: Sat, 28 Nov 2020 20:59:01 GMT
< x-amzn-RequestId: 213ca523-173b-42a9-ab41-e3420602bef9
< x-amzn-Remapped-Content-Length: 37
< x-amzn-Remapped-Connection: keep-alive
< x-amz-apigw-id: WvIDaFu0PHcFZOg=
< Cache-Control: no-cache
< x-amzn-Remapped-Server: nginx/1.19.3
< Pragma: no-cache
< x-amzn-Remapped-Date: Sat, 28 Nov 2020 20:59:01 GMT
< X-Cache: Error from cloudfront
< Via: 1.1 9a0d5427f47351631cdee4d5e38248d8.cloudfront.net (CloudFront)
< X-Amz-Cf-Pop: LHR50-C1
< X-Amz-Cf-Id: _VYxM43hCyrzj5hJNitbxLkzjww7iygpoWXT7sege-5eySEaKmcRxQ==
<
{"supportID": "4099392564272510395"}
* Connection #0 to host api.cloud-app.uk left intact
This can be checked in the NGINX App Protect security logs displayed in Kibana NGINX App Protect dashboards, running in AWS ElasticSearch:
The bot defense behavior can be controlled from the policy file under the CodeCommit repository. Changing the action from "block" to "alarm" for "untrusted bot" and commiting the change will trigger the pipeline to redeploy the NGINX App Protect policy:
apiVersion: v1
kind: ConfigMap
metadata:
name: nap-api-policy
namespace: default
data:
NAP_API_Policy.json: |+
{
"policy": {
"name": "policy_name",
"template": { "name": "POLICY_TEMPLATE_NGINX_BASE" },
"applicationLanguage": "utf-8",
"enforcementMode": "blocking",
"signature-sets": [
{
"name": "High Accuracy Signatures",
"block": true,
"alarm": true
}
],
"bot-defense": {
"settings": {
"isEnabled": true
},
"mitigations": {
"classes": [
{
"name": "trusted-bot",
"action": "alarm"
},
{
"name": "untrusted-bot",
"action": "block"
},
{
"name": "malicious-bot",
"action": "block"
}
]
}
},
...............................................................................................................
The same Curl call is now being allowed:
curl -vvvk https://api.cloud-app.uk/api/rest/execute_money_transfer.php -d '{"account": 2075894, "amount": 1, "currency": "GBP", "friend": "Vincent"}' -H "Content-Type: application/json" -X POST
Note: Unnecessary use of -X or --request, POST is already inferred.
* Trying 143.204.192.29...
* TCP_NODELAY set
* Connected to api.cloud-app.uk (143.204.192.29) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/cert.pem
CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256
* ALPN, server accepted to use h2
* Server certificate:
* subject: CN=*.cloud-app.uk
* start date: Nov 18 00:00:00 2020 GMT
* expire date: Dec 17 23:59:59 2021 GMT
* issuer: C=US; O=Amazon; OU=Server CA 1B; CN=Amazon
* SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7fc877008200)
> POST /api/rest/execute_money_transfer.php HTTP/2
> Host: api.cloud-app.uk
> User-Agent: curl/7.64.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 75
>
* Connection state changed (MAX_CONCURRENT_STREAMS == 128)!
* We are completely uploaded and fine
< HTTP/2 200
< content-type: text/html; charset=UTF-8
< content-length: 155
< date: Mon, 30 Nov 2020 11:02:19 GMT
< x-amzn-requestid: 9bdb2379-06c4-4970-a528-cd8de9cb75b3
< x-amzn-remapped-content-length: 155
< x-amzn-remapped-connection: keep-alive
< x-amz-apigw-id: W0WhMH_TvHcFndQ=
< x-amzn-remapped-server: nginx/1.19.3
< vary: Accept-Encoding
< x-amzn-remapped-date: Mon, 30 Nov 2020 11:02:19 GMT
< x-cache: Miss from cloudfront
< via: 1.1 bb501579906725a97059c817430425cf.cloudfront.net (CloudFront)
< x-amz-cf-pop: LHR3-C1
< x-amz-cf-id: xo4zfKVqUeejkHzLPArADi1rxRxTJkg61YgfhruAR4KjdpMSnYymkQ==
<
* Connection #0 to host api.cloud-app.uk left intact
{"name":"Vincent", "status":"success","amount":"1", "currency":"GBP", "transid":"753910682", "msg":"The money transfer has been successfully completed "}* Closing connection 0
The new bot defense behavior can be checked in the NGINX App Protect Kibana dashboard:
Conclusion
To recap, this article has demoed the per-service model of deployment for NGINX App Protect in Kubernetes environment. The main advantage of this deployment model is the independent management of security policies and the portability of each security policy.
NGINX App Protect elevates the security level provided by the API Gateway by providing negative security and advanced security features like bot detection.
The configuration is being controlled by a CI/CD pipeline, in this case AWS CodePipeline, and the same OpenAPI file used to configure the AWS API Gateway is also ingested by the NGINX App Protect API instance.
Lastly the security logs sent by NGINX App Protect through Fluentd to AWS ElasticSearch are being displayed in Kibana dashboards.
Published Jan 15, 2021
Version 1.0
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