Request-based AWS Lambda authorizer

aws-authorizer-request.py

def lambda_handler(event, context):
    principalId = 'me'
    
    tmp = event['methodArn'].split(':')
    apiGatewayArnTmp = tmp[5].split('/')
    awsAccountId = tmp[4]

    headers = event['headers']
    queryStringParameters = event['queryStringParameters']
    pathParameters = event['pathParameters']
    stageVariables = event['stageVariables']

    region = tmp[3];
    restApiId = apiGatewayArnTmp[0]
    stage = apiGatewayArnTmp[1]
    method = apiGatewayArnTmp[2]
    resource = '/'  # root resource
    if apiGatewayArnTmp[3]:
        resource += apiGatewayArnTmp[3]
   
    authResponse = {}
    
    if (headers['HeaderAuth1'] == "1" and queryStringParameters['QueryString1'] == "2" and stageVariables['StageVar1'] == "3"):
        return generateAllow(principalId, event['methodArn'])
    else:
        raise Exception("Unauthorized")

def generatePolicy(principalId, effect, resource):
    authResponse = {}
    authResponse['principalId'] = principalId
    if (effect and resource):
        policyDocument = {}
        policyDocument['Version'] = '2012-10-17'
        policyDocument['Statement'] = []
        statementOne = {}
        statementOne['Action'] = 'execute-api:Invoke';
        statementOne['Effect'] = effect
        statementOne['Resource'] = resource
        policyDocument['Statement'].append(statementOne)
        authResponse['policyDocument'] = policyDocument
        
        context = {
            'key': 'value',  # $context.authorizer.key -> value
            'number': 1,
            'bool': True
        }
    
        authResponse['context'] = context
    return authResponse

def generateAllow(principalId, resource):
    return generatePolicy(principalId, 'Allow', resource)

def generateDeny(principalId, resource):
    return generatePolicy(principalId, 'Deny', resource)