AWS Lambda Authorizer

Field	Value
Document ID	ASCEND-SDK-004
Version	2026.04
Last Updated	April 2026
Author	Ascend Engineering Team
Publisher	OW-KAI Technologies Inc.
Classification	Enterprise Client Documentation
Compliance	SOC 2 CC6.1/CC6.2, PCI-DSS 7.1/8.3, HIPAA 164.312, NIST 800-53 AC-2/SI-4

Reading Time: 15 minutes | Skill Level: Intermediate

Overview

The ASCEND Lambda Authorizer integrates AI governance with Amazon API Gateway. Every request is evaluated against your governance policies before reaching backend services.

Fail-Secure Behavior

When ASCEND is unreachable, the Lambda Authorizer denies all requests by default. Ensure ASCEND availability before enabling governance in production.

Architecture

┌─────────────────────────────────────────────────────────────────────┐
│                     LAMBDA AUTHORIZER FLOW                           │
├─────────────────────────────────────────────────────────────────────┤
│                                                                       │
│   ┌─────────┐    ┌──────────────┐    ┌────────────────────────────┐ │
│   │   AI    │    │    API       │    │    Lambda Authorizer       │ │
│   │  Agent  │───▶│   Gateway    │───▶│                            │ │
│   │         │    │              │    │  1. Map request            │ │
│   └─────────┘    └──────────────┘    │  2. Check cache            │ │
│                         │            │  3. Call ASCEND            │ │
│                         │            │  4. Generate IAM policy    │ │
│                         │            │  5. Return Allow/Deny      │ │
│                         │            └────────────────────────────┘ │
│                         │                        │                   │
│                         │                        ▼                   │
│                         │               ┌────────────────┐          │
│                         │               │ ASCEND Platform │          │
│                         │               │                │          │
│                         │               │ Risk Assessment│          │
│                         │               │ Policy Engine  │          │
│                         │               │ Audit Log      │          │
│                         │               └────────────────┘          │
│                         │                                            │
│                         ▼                                            │
│               ┌──────────────┐                                      │
│               │   Backend    │                                      │
│               │   Service    │                                      │
│               └──────────────┘                                      │
│                                                                       │
└─────────────────────────────────────────────────────────────────────┘

Prerequisites

AWS Account with API Gateway
AWS CLI configured
Python 3.9+ runtime
ASCEND API key

Deployment Options

Option 1: AWS Serverless Application Repository (Recommended)

The easiest way to deploy is via the AWS Serverless Application Repository:

# Deploy via AWS Console
# Visit: https://serverlessrepo.aws.amazon.com/applications/us-east-2/511851427029/ascend-lambda-authorizer

# Or deploy via CLI
aws serverlessrepo create-cloud-formation-change-set \
  --application-id arn:aws:serverlessrepo:us-east-2:511851427029:applications/ascend-lambda-authorizer \
  --stack-name ascend-authorizer \
  --capabilities CAPABILITY_IAM \
  --parameter-overrides Name=AscendApiKeySecret,Value=arn:aws:secretsmanager:REGION:ACCOUNT:secret:ascend-api-key

Package Info: ascend-lambda-authorizer on AWS SAR | Version: 1.0.0

Option 2: CloudFormation

# Source: lambda-authorizer/cloudformation/template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Description: ASCEND Lambda Authorizer

Parameters:
  AscendApiKey:
    Type: String
    NoEcho: true
    Description: ASCEND API Key

  AscendApiUrl:
    Type: String
    Default: https://pilot.owkai.app
    Description: ASCEND API URL

  Environment:
    Type: String
    Default: production
    AllowedValues:
      - production
      - staging
      - development

Resources:
  AscendAuthorizerFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: ascend-authorizer
      Runtime: python3.11
      Handler: handler.lambda_handler
      Code:
        S3Bucket: ascend-lambda-artifacts
        S3Key: authorizer/latest.zip
      Timeout: 10
      MemorySize: 256
      Environment:
        Variables:
          ASCEND_API_KEY: !Ref AscendApiKey
          ASCEND_API_URL: !Ref AscendApiUrl
          ASCEND_ENVIRONMENT: !Ref Environment
          CACHE_ENABLED: 'true'
          CACHE_TTL_SECONDS: '60'
          FAIL_OPEN: 'false'

  AscendAuthorizer:
    Type: AWS::ApiGateway::Authorizer
    Properties:
      Name: AscendAuthorizer
      RestApiId: !Ref MyRestApi
      Type: REQUEST
      AuthorizerUri: !Sub 'arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${AscendAuthorizerFunction.Arn}/invocations'
      AuthorizerResultTtlInSeconds: 60
      IdentitySource: method.request.header.X-Ascend-Agent-ID

  AuthorizerPermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt AscendAuthorizerFunction.Arn
      Action: lambda:InvokeFunction
      Principal: apigateway.amazonaws.com
      SourceArn: !Sub 'arn:aws:execute-api:${AWS::Region}:${AWS::AccountId}:${MyRestApi}/*'

Outputs:
  AuthorizerArn:
    Value: !GetAtt AscendAuthorizerFunction.Arn

Deploy:

aws cloudformation deploy \
  --template-file template.yaml \
  --stack-name ascend-authorizer \
  --parameter-overrides \
    AscendApiKey="owkai_your_key_here" \
    Environment=production \
  --capabilities CAPABILITY_IAM

Option 3: SAM (Serverless Application Model)

# template.yaml
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Resources:
  AscendAuthorizer:
    Type: AWS::Serverless::Function
    Properties:
      Handler: handler.lambda_handler
      Runtime: python3.11
      CodeUri: ./src
      Environment:
        Variables:
          ASCEND_API_KEY: '{{resolve:ssm:/ascend/api-key}}'
          ASCEND_API_URL: https://pilot.owkai.app

Deploy:

sam build
sam deploy --guided

Option 4: Terraform

# main.tf
resource "aws_lambda_function" "ascend_authorizer" {
  filename         = "authorizer.zip"
  function_name    = "ascend-authorizer"
  role            = aws_iam_role.authorizer_role.arn
  handler         = "handler.lambda_handler"
  runtime         = "python3.11"
  timeout         = 10
  memory_size     = 256

  environment {
    variables = {
      ASCEND_API_KEY     = var.ascend_api_key
      ASCEND_API_URL     = "https://pilot.owkai.app"
      ASCEND_ENVIRONMENT = "production"
      CACHE_ENABLED      = "true"
      CACHE_TTL_SECONDS  = "60"
    }
  }
}

resource "aws_api_gateway_authorizer" "ascend" {
  name                   = "ascend-authorizer"
  rest_api_id           = aws_api_gateway_rest_api.api.id
  authorizer_uri        = aws_lambda_function.ascend_authorizer.invoke_arn
  authorizer_result_ttl_in_seconds = 60
  type                  = "REQUEST"
  identity_source       = "method.request.header.X-Ascend-Agent-ID"
}

Configuration

Environment Variables

Variable	Required	Default	Description
`ASCEND_API_KEY`	Yes	-	Your ASCEND API key
`ASCEND_API_URL`	No	`https://pilot.owkai.app`	API endpoint
`ASCEND_ENVIRONMENT`	No	`production`	Environment name
`CACHE_ENABLED`	No	`true`	Enable decision caching
`CACHE_TTL_SECONDS`	No	`60`	Cache TTL in seconds
`FAIL_OPEN`	No	`false`	Allow on error (dangerous)
`LOG_LEVEL`	No	`INFO`	Logging level

Lambda Handler

The handler processes API Gateway events:

# Source: lambda-authorizer/src/handler.py:109
def lambda_handler(event: Dict[str, Any], context: Any) -> Dict[str, Any]:
    """
    Lambda authorizer entry point.

    Security:
        - FAIL SECURE: Any error returns Deny policy
        - Never logs sensitive data (API keys, tokens)
        - All decisions are audited
    """
    # Lambda handler implementation continues

Supported Event Types

Event Type	API Gateway Type	Support
REQUEST	REST API	✅ Full
TOKEN	REST API	✅ Full
HTTP API v2	HTTP API	✅ Full

Request Mapping

Agent ID Extraction

The authorizer extracts agent ID from:

X-Ascend-Agent-ID header (preferred)
Request context (if configured)
Default agent ID (if configured)

Action Type Mapping

HTTP Method	Path Pattern	Action Type
GET	`/customers/*`	`api.read_customers`
POST	`/orders`	`api.create_orders`
DELETE	`/users/*`	`api.delete_users`

Custom mappings can be configured via environment variables.

IAM Policy Generation

Allow Policy

{
    "principalId": "my-agent-001",
    "policyDocument": {
        "Version": "2012-10-17",
        "Statement": [{
            "Action": "execute-api:Invoke",
            "Effect": "Allow",
            "Resource": "arn:aws:execute-api:us-east-1:123456789:api/stage/GET/customers"
        }]
    },
    "context": {
        "ascend_action_id": "12345",
        "ascend_risk_score": "3.5",
        "ascend_risk_level": "low",
        "ascend_status": "approved"
    }
}

Deny Policy

{
    "principalId": "my-agent-001",
    "policyDocument": {
        "Version": "2012-10-17",
        "Statement": [{
            "Action": "execute-api:Invoke",
            "Effect": "Deny",
            "Resource": "arn:aws:execute-api:*"
        }]
    },
    "context": {
        "ascend_status": "denied",
        "ascend_reason": "High-risk operation requires approval",
        "ascend_error_code": "POLICY_VIOLATION"
    }
}

Caching

API Gateway Caching

Enable caching in API Gateway Authorizer settings:

AuthorizerResultTtlInSeconds: 60  # Cache approved results for 60s

Internal Caching

The Lambda also maintains an internal cache for faster responses:

# Source: lambda-authorizer/src/policy_generator.py
# Internal cache for approved policies
# Reduces ASCEND API calls for repeated requests

Monitoring

CloudWatch Metrics

The authorizer publishes these metrics:

Metric	Description
`AscendAuthorizerLatency`	Total authorization time
`AscendApiLatency`	ASCEND API call time
`CacheHitRate`	Percentage of cache hits
`DenyRate`	Percentage of denied requests
`ErrorRate`	Percentage of errors

CloudWatch Logs

Structured JSON logging:

{
    "correlation_id": "req-12345",
    "agent_id": "my-agent-001",
    "action_type": "api.read_customers",
    "status": "approved",
    "risk_score": 3.5,
    "latency_ms": 45,
    "cache_hit": false
}

Alarms

Recommended CloudWatch Alarms:

# High error rate alarm
AscendErrorAlarm:
  Type: AWS::CloudWatch::Alarm
  Properties:
    AlarmName: ascend-authorizer-errors
    MetricName: ErrorRate
    Namespace: Ascend/Authorizer
    Threshold: 5
    EvaluationPeriods: 3
    ComparisonOperator: GreaterThanThreshold

Fail Secure Design

The authorizer follows FAIL SECURE principles:

# Source: lambda-authorizer/src/handler.py:182
# FAIL SECURE: Any error returns Deny policy
# unless explicitly configured for fail_open

try:
    response = call_ascend_api(action)
except AscendTimeoutError:
    return create_deny_policy("Authorization timeout")
except AscendAPIError:
    return create_deny_policy("Authorization service error")
except Exception:
    return create_deny_policy("Internal authorization error")

Testing

Local Testing

# test_handler.py
import json
from src.handler import lambda_handler

event = {
    "type": "REQUEST",
    "methodArn": "arn:aws:execute-api:us-east-1:123456:api/prod/GET/customers",
    "headers": {
        "X-Ascend-Agent-ID": "test-agent"
    },
    "httpMethod": "GET",
    "path": "/customers"
}

response = lambda_handler(event, None)
print(json.dumps(response, indent=2))

Integration Testing

# Test with curl
curl -H "X-Ascend-Agent-ID: test-agent" \
     https://api.yourcompany.com/customers

Troubleshooting

Lambda returns 403 Deny for all requests

Cause: The ASCEND API key environment variable is not set or is invalid. The authorizer defaults to Deny on any initialization error. Solution: Verify ASCEND_API_KEY is set in the Lambda environment variables. Check CloudWatch Logs for the Lambda function — look for AscendAuthenticationError or ConfigurationError entries.

Cold start latency exceeds API Gateway timeout

Cause: Lambda cold starts in VPC configurations can take 5-10 seconds, exceeding the default API Gateway authorizer timeout (10 seconds). Solution: Enable Provisioned Concurrency on the Lambda function to eliminate cold starts. Alternatively, increase the API Gateway authorizer timeout to 30 seconds.

Cached decisions not refreshing

Cause: API Gateway caches authorizer responses for the configured TTL. Stale cached decisions persist until the cache entry expires. Solution: Set AuthorizerResultTtlInSeconds to an appropriate value (default 300 seconds). To force a refresh, update the authorizer configuration which invalidates the cache.

Best Practices

Use Secrets Manager for API Key

ASCEND_API_KEY: '{{resolve:secretsmanager:ascend-api-key}}'

Enable Provisioned Concurrency for consistent latency
Set appropriate timeout (10s recommended)
Monitor error rates with CloudWatch Alarms
Use VPC endpoint for private API access

Next Steps

Kong Plugin — For Kong Gateway
Envoy/Istio — For service mesh
Smart Rules — Create custom rules

Document Version: 2026.04 | Last Updated: April 2026

Overview​

Architecture​

Prerequisites​

Deployment Options​

Option 1: AWS Serverless Application Repository (Recommended)​

Option 2: CloudFormation​

Option 3: SAM (Serverless Application Model)​

Option 4: Terraform​

Configuration​

Environment Variables​

Lambda Handler​

Supported Event Types​

Request Mapping​

Agent ID Extraction​

Action Type Mapping​

IAM Policy Generation​

Allow Policy​

Deny Policy​

Caching​

API Gateway Caching​

Internal Caching​

Monitoring​

CloudWatch Metrics​

CloudWatch Logs​

Alarms​

Fail Secure Design​

Testing​

Local Testing​

Integration Testing​

Troubleshooting​

Lambda returns 403 Deny for all requests​

Cold start latency exceeds API Gateway timeout​

Cached decisions not refreshing​

Best Practices​

Next Steps​