From be193e05b4767215f7c5cd7d87552e6873d7ac6d Mon Sep 17 00:00:00 2001
From: Sid Wadikar <sidw@meta.com>
Date: Mon, 29 Jul 2024 11:13:55 -0700
Subject: [PATCH] Create lambda function

Summary: Opensourcing new TTP for Cloud.

Differential Revision: D60400010
---
 .../lambda/create-lambda-function/README.md   |  89 ++++++++++
 .../create-lambda-function.yaml               | 161 ++++++++++++++++++
 .../create-lambda-function/lambda-function.py |  25 +++
 .../create-lambda-function/trust-policy.json  |  13 ++
 4 files changed, 288 insertions(+)
 create mode 100644 ttps/cloud/aws/lambda/create-lambda-function/README.md
 create mode 100644 ttps/cloud/aws/lambda/create-lambda-function/create-lambda-function.yaml
 create mode 100644 ttps/cloud/aws/lambda/create-lambda-function/lambda-function.py
 create mode 100644 ttps/cloud/aws/lambda/create-lambda-function/trust-policy.json

diff --git a/ttps/cloud/aws/lambda/create-lambda-function/README.md b/ttps/cloud/aws/lambda/create-lambda-function/README.md
new file mode 100644
index 0000000..72df6b2
--- /dev/null
+++ b/ttps/cloud/aws/lambda/create-lambda-function/README.md
@@ -0,0 +1,89 @@
+# Create AWS Lambda Function
+
+![Meta TTP](https://img.shields.io/badge/Meta_TTP-blue)
+
+This TTP is used to create a new Lambda function in AWS. It uses the AWS CLI to create a new function with the specified name.
+  A temprory IAM role, S3 bucket are created to hold the lambda function code.
+  If a function with given name exists, no new function is created.
+  If a function does not exist a new function is created. It is also deleted during cleanup.
+  A public API gateway is created to also invoke this function. This enables use to invoke the function from the internet.
+  `--no-cleanup` options should be explicitly specified if we do not want the new function created to be deleted.
+
+
+## Arguments
+
+- **region**: Name of the AWS region to use with TTPForge.
+- **lambda_function_name**: The name of the new Lambda function to be created.
+
+## Steps
+
+1. Set up necessary cloud environment variables.
+2. Create a temprory IAM role to be assumed by the lambda function.
+3. Create a S3 bucket with a random string name
+4. Zip and upload lambad code from local device to the newly created S3 bucket.
+5. Create a new Lambda function if no existing function is found with given function name.
+6. Create a API which is publicly accessible and integrate the newly created lambda function with it.
+6. Invoke the newly created Lambda function by accessing the API URL
+7. By default during the cleanup, delete the recently created Lambda function, S3 bucket, IAM role and the API gateway.
+
+## Manual Reproduction Steps
+
+```
+# Set necessary env variables
+
+# Create new temp IAM role
+aws iam create-role --role-name "ROLE-NAME" --assume-role-policy-document file://trust-policy.json
+
+# Create a new S3 bucket to host lambda function
+aws s3 mb s3://BUCKET_NAME
+
+# Upload lambda function zip file to S3 bucket
+aws s3 cp lambda-function.zip s3://BUCKET_NAME
+
+# Create a new function
+aws lambda create-function --function-name "FUNCTION_NAME" --runtime "RUNTIME" --handler "HANDLER" --role "ROLE_ARN" --code "S3Bucket=$BUCKET_NAME,S3Key=lambda-function.zip"
+
+# Create a new REST API
+rest_api_id=$(aws apigateway create-rest-api --name "FUNCTION_NAME"-api --query 'id' --output text)
+
+# Get the root resource id
+root_resource_id=$(aws apigateway get-resources --rest-api-id $rest_api_id --query 'items[?path==`/`].id' --output text)
+
+# Create a GET method for the new resource
+aws apigateway put-method --rest-api-id $rest_api_id --resource-id $root_resource_id --http-method GET --authorization-type "NONE" > /dev/null 2>&1
+
+# Add necessary permissions to the new resource method
+lambda_func_arn=$(aws lambda get-function --function-name "FUNCTION_NAME" --query 'Configuration.FunctionArn' --output text)
+account_id=$(aws sts get-caller-identity --query Account --output text)
+account_region=$(aws configure get region)
+source_arn="arn:aws:execute-api:$account_region:$account_id:$rest_api_id/*/*/"
+
+aws lambda add-permission --function-name $lambda_func_arn --source-arn $source_arn --principal apigateway.amazonaws.com --statement-id apigateway-test1-"FUNCTION_NAME" --action lambda:InvokeFunction > /dev/null 2>&1
+
+
+# Connect the GET method to the Lambda function (define integration)
+lambda_invocation_uri="arn:aws:apigateway:$account_region:lambda:path/2015-03-31/functions/$lambda_func_arn/invocations"
+aws apigateway put-integration --rest-api-id $rest_api_id --resource-id $root_resource_id --http-method GET --type AWS --integration-http-method POST --uri $lambda_invocation_uri > /dev/null 2>&1
+
+
+# Specify an INTEGRATION RESPONSE for a method response code of 200 and allow Passthrough content handling
+aws apigateway put-integration-response --rest-api-id $rest_api_id --resource-id $root_resource_id --http-method GET --status-code 200 > /dev/null 2>&1
+
+# Specify a METHOD response for HTTP status code 200
+aws apigateway put-method-response --rest-api-id $rest_api_id --resource-id $root_resource_id --http-method GET --status-code 200 > /dev/null 2>&1
+
+# Deploy the API
+aws apigateway create-deployment --rest-api-id $rest_api_id --stage-name prod  > /dev/null 2>&1
+
+# Get the invoke URL and curl it
+invoke_url="https://$rest_api_id.execute-api.$account_region.amazonaws.com/prod"
+curl $invoke_url
+
+```
+
+## MITRE ATT&CK Mapping
+
+- **Tactics**:
+  - TA0003 Persistence
+- **Techniques**:
+  - T1098 Account Manipulation
diff --git a/ttps/cloud/aws/lambda/create-lambda-function/create-lambda-function.yaml b/ttps/cloud/aws/lambda/create-lambda-function/create-lambda-function.yaml
new file mode 100644
index 0000000..7cffea3
--- /dev/null
+++ b/ttps/cloud/aws/lambda/create-lambda-function/create-lambda-function.yaml
@@ -0,0 +1,161 @@
+---
+api_version: 2.0
+uuid: 4b783ca9-7cf7-49c4-a74f-26c753a4b1c2
+name: create_lambda_function
+description: |
+  This TTP is used to create a new Lambda function in AWS. It uses the AWS CLI to create a new function with the specified name and runtime.
+  If a function with given name exists, nothing is done and the TTP is closed.
+  If a function does not exist a new function is created. It is also deleted during cleanup.
+  A public API gateway is also created to invoke this function. This enables use to invoke the function from the internet.
+  `--no-cleanup` options should be explicitly specified if we do not want the new function created to be deleted.
+
+args:
+  - name: lambda_function_name
+    description: The name of the new Lambda function to be created.
+    default: ttpforge-lambda-function
+  - name: region
+    description: Name of the AWS region to use with TTPForge
+    default: us-east-1
+
+mitre:
+  tactics:
+    - TA0003 Persistence
+  techniques:
+    - T1098 Account Manipulation
+
+steps:
+  - name: aws-connector
+    description: This step invokes the verifies aws creds are present and aws cli is available.
+    ttp: //helpers/cloud/aws/validate-aws-env-configured.yaml
+    args:
+      region: "{{ .Args.region }}"
+
+  - name: create_temp_iam_role
+    description: Create a temp IAM role that will be used by the lambda function.
+    inline: |
+      echo "Creating temp IAM role..."
+
+      role_name="{{.Args.lambda_function_name}}-role"
+      aws iam create-role --role-name $role_name --assume-role-policy-document file://trust-policy.json
+      echo "Temp IAM role created: $role_name"
+
+    cleanup:
+      inline: |
+        echo "Deleting temp IAM role..."
+
+        role_name="{{.Args.lambda_function_name}}-role"
+        aws iam delete-role --role-name $role_name
+
+  - name: create_s3_bucket
+    description: Create a S3 bucket with a random string name.
+    inline: |
+      echo "Creating S3 bucket..."
+
+      bucket_suffix=$(cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 10 | head -n 1)
+      bucket_name="{{.Args.lambda_function_name}}-${bucket_suffix}"
+
+      aws s3 mb s3://$bucket_name
+      echo "S3 bucket created: $bucket_name"
+    cleanup:
+      inline: |
+        echo "Deleting S3 bucket..."
+        bucket_name=$(aws s3 ls | grep {{.Args.lambda_function_name}} | awk '{print $3}')
+        echo $bucket_name
+
+        aws s3 rb s3://$bucket_name --force
+
+  - name: upload_lambda_code
+    description: Upload the lambda code to the newly created S3 bucket.
+    inline: |
+      echo "Uploading lambda code to S3 bucket..."
+
+      bucket_name=$(aws s3 ls | grep {{.Args.lambda_function_name}} | awk '{print $3}')
+      echo $bucket_name
+
+      zip -r lambda-function.zip lambda-function.py
+      aws s3 cp lambda-function.zip s3://$bucket_name
+
+      echo "Lambda code uploaded to S3 bucket: $bucket_name"
+
+    cleanup:
+      inline: |
+        echo "Deleting created lambda function zip file..."
+        rm -rf lambda-function.zip
+
+  - name: create_lambda_function
+    description: Check if the specified Lambda function exists. If not create a new one.
+    inline: |
+      echo "Checking if function {{.Args.lambda_function_name}} exists..."
+      role_name="{{.Args.lambda_function_name}}-role"
+      role_arn=$(aws iam get-role --role-name $role_name --query 'Role.Arn' --output text)
+      bucket_name=$(aws s3 ls | grep {{.Args.lambda_function_name}} | awk '{print $3}')
+
+      function_exists=$(aws lambda list-functions --query 'Functions[?FunctionName==`{{.Args.lambda_function_name}}`]' 2>&1)
+      if [ -n "$function_exists" ] && [ "$function_exists" = "[]" ]; then
+        echo -  "Function does not exist. Creating a new function..."
+        aws lambda create-function --function-name {{.Args.lambda_function_name}} --runtime "python3.9" --handler lambda-function.lambda_handler --role $role_arn --code S3Bucket=$bucket_name,S3Key=lambda-function.zip
+        echo "New Lambda function created: {{.Args.lambda_function_name}}"
+        sleep 5
+      else
+        echo "Function {{.Args.lambda_function_name}} already exists."
+      fi
+    cleanup:
+      inline: |
+        echo "Deleting Lambda function..."
+        aws lambda delete-function --function-name {{.Args.lambda_function_name}}
+        echo "Lambda function deleted: {{.Args.lambda_function_name}}"
+
+  - name: create_api_and_invoke
+    description: Invoke the newly created Lambda function and display the output. This is a public API, that means anyone on the internet can invoke this lambda function
+    inline: |
+      echo "Creating REST API Gateway..."
+
+      # Create a new REST API
+      rest_api_id=$(aws apigateway create-rest-api --name {{.Args.lambda_function_name}}-api --query 'id' --output text)
+
+      # Get the root resource id
+      root_resource_id=$(aws apigateway get-resources --rest-api-id $rest_api_id --query 'items[?path==`/`].id' --output text)
+
+      # Create a GET method for the new resource
+      aws apigateway put-method --rest-api-id $rest_api_id --resource-id $root_resource_id --http-method GET --authorization-type "NONE" > /dev/null 2>&1
+
+      # Add necessary permissions to the new resource method
+      lambda_func_arn=$(aws lambda get-function --function-name {{.Args.lambda_function_name}} --query 'Configuration.FunctionArn' --output text)
+      account_id=$(aws sts get-caller-identity --query Account --output text)
+      account_region=$(aws configure get region)
+      statement_id=apigateway-$(cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 10 | head -n 1)-{{.Args.lambda_function_name}}
+      source_arn="arn:aws:execute-api:$account_region:$account_id:$rest_api_id/*/GET/"
+
+      aws lambda add-permission --function-name $lambda_func_arn --source-arn $source_arn \
+      --principal apigateway.amazonaws.com --statement-id $statement_id --action lambda:InvokeFunction > /dev/null 2>&1
+
+
+      # Connect the GET method to the Lambda function (define integration)
+      lambda_invocation_uri="arn:aws:apigateway:$account_region:lambda:path/2015-03-31/functions/$lambda_func_arn/invocations"
+      aws apigateway put-integration --rest-api-id $rest_api_id --resource-id $root_resource_id \
+      --http-method GET --type AWS --integration-http-method POST --uri $lambda_invocation_uri > /dev/null 2>&1
+
+
+      # Specify an INTEGRATION RESPONSE for a method response code of 200 and allow Passthrough content handling
+      aws apigateway put-integration-response --rest-api-id $rest_api_id --resource-id $root_resource_id \
+      --http-method GET --status-code 200 --response-templates '{"application/json":"$input.path('\'$.body\'')"}' > /dev/null 2>&1
+
+      # Specify a METHOD response for HTTP status code 200
+      aws apigateway put-method-response --rest-api-id $rest_api_id --resource-id $root_resource_id \
+      --http-method GET --status-code 200 > /dev/null 2>&1
+
+      # Deploy the API
+      aws apigateway create-deployment --rest-api-id $rest_api_id --stage-name prod  > /dev/null 2>&1
+
+      # Get the invoke URL and curl it
+      invoke_url="https://$rest_api_id.execute-api.$account_region.amazonaws.com/prod"
+      echo "Invoke URL: $invoke_url"
+      sleep 10
+      curl $invoke_url
+
+    cleanup:
+      inline: |
+        echo "Deleting REST API Gateway..."
+        rest_api_id=$(aws apigateway get-rest-apis --query 'items[?name==`{{.Args.lambda_function_name}}-api`].id' --output text)
+        aws apigateway delete-rest-api --rest-api-id $rest_api_id
+        echo "REST API Gateway deleted: $rest_api_id"
diff --git a/ttps/cloud/aws/lambda/create-lambda-function/lambda-function.py b/ttps/cloud/aws/lambda/create-lambda-function/lambda-function.py
new file mode 100644
index 0000000..09f7ee6
--- /dev/null
+++ b/ttps/cloud/aws/lambda/create-lambda-function/lambda-function.py
@@ -0,0 +1,25 @@
+import json
+import logging
+
+import boto3
+
+logger = logging.getLogger()
+logger.setLevel(logging.INFO)
+
+
+def lambda_handler(event, context):
+    sts = boto3.client("sts")
+    sts_response = sts.get_caller_identity()
+    print("STS Response: ", sts_response)
+
+    logger.info(f"CloudWatch logs group: {context.log_group_name}")
+
+    formatted_sts_response = json.dumps(sts_response, indent=4)
+    return {
+        "statusCode": 200,
+        "body": formatted_sts_response,
+        "headers": {
+            "Content-Type": "text/plain",
+        },
+        "isBase64Encoded": False,
+    }
diff --git a/ttps/cloud/aws/lambda/create-lambda-function/trust-policy.json b/ttps/cloud/aws/lambda/create-lambda-function/trust-policy.json
new file mode 100644
index 0000000..381f2d3
--- /dev/null
+++ b/ttps/cloud/aws/lambda/create-lambda-function/trust-policy.json
@@ -0,0 +1,13 @@
+{
+    "Version": "2012-10-17",
+    "Statement": [
+      {
+        "Action": "sts:AssumeRole",
+        "Principal": {
+          "Service": "lambda.amazonaws.com"
+        },
+        "Effect": "Allow",
+        "Sid": ""
+      }
+    ]
+  }