Get user's IP Address in Lambda (with API Gateway, and Python)

Question

I was using this technique (How could I retrieve AWS Lambda public IP address by using Python?) but it gives the IPAddress of the Lambda Server within AWS.

Based on this: How can I retrieve a user's public IP address via Amazon API Gateway + Lambda (node), it looks like I should be able to use

ip_address = event['requestContext']['identity']['sourceIp'];

My handler starts like this:

def lambda_handler(event, context):

but if I do a pprint.pprint(event), I don't see any RequestContext in it, only the "body".

The last comment by FFXSam on the Jonathan answer says "It should be noted that event.requestContext.identity is not present if you're serving a page that's not behind an authorizer.". I'm not sure what that means or why it is true. I'm using API Gateway, and JavaScript code on the client side is calling it.

I could ask the client coder to send me the local IP Address in the body, but it seems like I should be able to get it in the Lambda function itself.

Someone ask for the events, even though I said it only had the fields being passed in a json element called "body":

code:

print("pprint event:")
pprint.pprint(event)


2021-06-06T13:30:01.231-05:00   pprint event:
2021-06-06T13:30:01.231-05:00   {'body': {'ResponseTimeMilliseconds': 2225,
2021-06-06T13:30:01.231-05:00   'authToken': '12312312',
2021-06-06T13:30:01.231-05:00   'handNumber': 7}}

Answer 1

I rewarded bounty to Muzaffar Shaikh, but here I will give a more thorough explanation, which seems to be lacking on StackOverflow. His answer got the IP Address, but dropped my "body" field, but it certainly pointed me in the right direction.

In the AWS API Gateway tool, click "Resources" then your method (mine was "Post"), then click on "Integration Request" as shown here.

Scroll down to the bottom, and if there are not any templates, type in "application/json" and click the checkbox (note, "application/json" is there in light gray letters, but just clicking the checkbox without typing it doesn't work).

Then I put in the following template:

{
   "client_ip" : "$input.params('X-Forwarded-For')",
   "user_agent" : "$input.params('User-Agent')",
   "body" : $input.json('$.body') 
}

NOTE: if I put $input.json('$') or $input.json('body'), I ended up with a "body" field inside my "body" field, which broke the current logic.

When the web page was completed, it looked like this:

The next step is to redeploy your template to the "deploy stage" (environment) you were using.

By the way, when entering the template, if you click "Method Request passthrough" in the "Generate template" drop down box, it will generate a template like this (I didn't use this option, but will read more about it soon):

##  See http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
##  This template will pass through all parameters including path, querystring, header, stage variables, and context through to the integration endpoint via the body/payload
#set($allParams = $input.params())
{
"body-json" : $input.json('$'),
"params" : {
#foreach($type in $allParams.keySet())
    #set($params = $allParams.get($type))
"$type" : {
    #foreach($paramName in $params.keySet())
    "$paramName" : "$util.escapeJavaScript($params.get($paramName))"
        #if($foreach.hasNext),#end
    #end
}
    #if($foreach.hasNext),#end
#end
},
"stage-variables" : {
#foreach($key in $stageVariables.keySet())
"$key" : "$util.escapeJavaScript($stageVariables.get($key))"
    #if($foreach.hasNext),#end
#end
},
"context" : {
    "account-id" : "$context.identity.accountId",
    "api-id" : "$context.apiId",
    "api-key" : "$context.identity.apiKey",
    "authorizer-principal-id" : "$context.authorizer.principalId",
    "caller" : "$context.identity.caller",
    "cognito-authentication-provider" : "$context.identity.cognitoAuthenticationProvider",
    "cognito-authentication-type" : "$context.identity.cognitoAuthenticationType",
    "cognito-identity-id" : "$context.identity.cognitoIdentityId",
    "cognito-identity-pool-id" : "$context.identity.cognitoIdentityPoolId",
    "http-method" : "$context.httpMethod",
    "stage" : "$context.stage",
    "source-ip" : "$context.identity.sourceIp",
    "user" : "$context.identity.user",
    "user-agent" : "$context.identity.userAgent",
    "user-arn" : "$context.identity.userArn",
    "request-id" : "$context.requestId",
    "resource-id" : "$context.resourceId",
    "resource-path" : "$context.resourcePath"
    }
}

Two reference for mapping templates:

1. https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
2. https://docs.aws.amazon.com/apigateway/latest/developerguide/models-mappings.html

I still have some research to do as to when to user "$input.params" vs "$context.some_value".