feat(awslambda): New check to ensure that a function is inside VPC (#4783)

Co-authored-by: Sergio Garcia <38561120+sergargar@users.noreply.github.com>

prowler/providers/aws/services/awslambda/awslambda_function_inside_vpc/awslambda_function_inside_vpc.metadata.json

@@ -0,0 +1,30 @@
+{
+  "Provider": "aws",
+  "CheckID": "awslambda_function_inside_vpc",
+  "CheckTitle": "Ensure AWS Lambda Functions Are Deployed Inside a VPC",
+  "CheckType": [],
+  "ServiceName": "lambda",
+  "SubServiceName": "",
+  "ResourceIdTemplate": "arn:partition:lambda:region:account-id:function/function-name",
+  "Severity": "low",
+  "ResourceType": "AwsLambdaFunction",
+  "Description": "This check verifies whether an AWS Lambda function is deployed within a Virtual Private Cloud (VPC). Deploying Lambda functions inside a VPC improves security by allowing control over the network environment, reducing the exposure to public internet threats.",
+  "Risk": "Lambda functions not deployed in a VPC may expose your application to increased security risks, including unauthorized access and data breaches. Without the network isolation provided by a VPC, your Lambda functions are more vulnerable to attacks.",
+  "RelatedUrl": "https://docs.aws.amazon.com/lambda/latest/dg/configuration-vpc.html",
+  "Remediation": {
+    "Code": {
+      "CLI": "aws lambda update-function-configuration --region <region-name> --function-name <function-name> --vpc-config SubnetIds=<subnet-id-1>,<subnet-id-2>,SecurityGroupIds=<security-group-id>",
+      "NativeIaC": "https://www.trendmicro.com/cloudoneconformity/knowledge-base/aws/Lambda/function-in-vpc.html",
+      "Other": "https://docs.aws.amazon.com/securityhub/latest/userguide/lambda-controls.html#lambda-3",
+      "Terraform": "https://docs.prowler.com/checks/aws/general-policies/ensure-that-aws-lambda-function-is-configured-inside-a-vpc-1/"
+    },
+    "Recommendation": {
+      "Text": "Configure your AWS Lambda functions to operate within a Virtual Private Cloud (VPC) to enhance security and control network access.",
+      "Url": ""
+    }
+  },
+  "Categories": [],
+  "DependsOn": [],
+  "RelatedTo": [],
+  "Notes": ""
+}

prowler/providers/aws/services/awslambda/awslambda_function_inside_vpc/awslambda_function_inside_vpc.py

@@ -0,0 +1,27 @@
+from typing import List
+
+from prowler.lib.check.models import Check, Check_Report_AWS
+from prowler.providers.aws.services.awslambda.awslambda_client import awslambda_client
+
+
+class awslambda_function_inside_vpc(Check):
+    def execute(self) -> List[Check_Report_AWS]:
+        findings = []
+        for function_arn, function in awslambda_client.functions.items():
+            report = Check_Report_AWS(self.metadata())
+            report.region = function.region
+            report.resource_id = function.name
+            report.resource_arn = function_arn
+            report.resource_tags = function.tags
+            report.status = "FAIL"
+            report.status_extended = (
+                f"Lambda function {function.name} is not inside a VPC"
+            )
+
+            if function.vpc_id:
+                report.status = "PASS"
+                report.status_extended = f"Lambda function {function.name} is inside of VPC {function.vpc_id}"
+
+            findings.append(report)
+
+        return findings

prowler/providers/aws/services/awslambda/awslambda_service.py

@@ -37,13 +37,13 @@ class Lambda(AWSService):
                     ):
                         lambda_name = function["FunctionName"]
                         lambda_arn = function["FunctionArn"]
+                        vpc_config = function.get("VpcConfig", {})
                         # We must use the Lambda ARN as the dict key since we could have Lambdas in different regions with the same name
                         self.functions[lambda_arn] = Function(
                             name=lambda_name,
                             arn=lambda_arn,
-                            security_groups=function.get("VpcConfig", {}).get(
-                                "SecurityGroupIds", []
-                            ),
+                            security_groups=vpc_config.get("SecurityGroupIds", []),
+                            vpc_id=vpc_config.get("VpcId"),
                             region=regional_client.region,
                         )
                         if "Runtime" in function:
@@ -201,4 +201,5 @@ class Function(BaseModel):
     policy: dict = None
     code: LambdaCode = None
     url_config: URLConfig = None
+    vpc_id: Optional[str]
     tags: Optional[list] = []

tests/providers/aws/services/awslambda/awslambda_function_inside_vpc/awslambda_function_inside_vpc_test.py

@@ -0,0 +1,155 @@
+from json import dumps
+from unittest import mock
+
+from boto3 import client
+from moto import mock_aws
+
+from tests.providers.aws.utils import AWS_REGION_EU_WEST_1, set_mocked_aws_provider
+
+
+class Test_awslambda_function_inside_vpc:
+    def test_no_functions(self):
+        from prowler.providers.aws.services.awslambda.awslambda_service import Lambda
+
+        aws_provider = set_mocked_aws_provider(AWS_REGION_EU_WEST_1)
+
+        with mock.patch(
+            "prowler.providers.common.provider.Provider.get_global_provider",
+            return_value=aws_provider,
+        ), mock.patch(
+            "prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc.awslambda_client",
+            new=Lambda(aws_provider),
+        ):
+            # Test Check
+            from prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc import (
+                awslambda_function_inside_vpc,
+            )
+
+            check = awslambda_function_inside_vpc()
+            result = check.execute()
+
+            assert len(result) == 0
+
+    @mock_aws
+    def test_function_inside_vpc(self):
+        # Create IAM Role for Lambda Function
+        iam_client = client("iam", region_name=AWS_REGION_EU_WEST_1)
+        role_name = "test-role"
+        assume_role_policy_document = {
+            "Version": "2012-10-17",
+            "Statement": [
+                {
+                    "Effect": "Allow",
+                    "Principal": {"Service": "lambda.amazonaws.com"},
+                    "Action": "sts:AssumeRole",
+                }
+            ],
+        }
+        role_arn = iam_client.create_role(
+            RoleName=role_name,
+            AssumeRolePolicyDocument=dumps(assume_role_policy_document),
+        )["Role"]["Arn"]
+
+        # Create Lambda Function inside VPC
+        lambda_client = client("lambda", region_name=AWS_REGION_EU_WEST_1)
+        function_name = "test_function"
+        function_arn = lambda_client.create_function(
+            FunctionName=function_name,
+            Runtime="python3.8",
+            Role=role_arn,
+            Handler="lambda_function.lambda_handler",
+            Code={"ZipFile": b"file not used"},
+            VpcConfig={
+                "SubnetIds": ["subnet-12345678"],
+                "SecurityGroupIds": ["sg-12345678"],
+            },
+        )["FunctionArn"]
+
+        from prowler.providers.aws.services.awslambda.awslambda_service import Lambda
+
+        aws_provider = set_mocked_aws_provider([AWS_REGION_EU_WEST_1])
+
+        with mock.patch(
+            "prowler.providers.common.provider.Provider.get_global_provider",
+            return_value=aws_provider,
+        ), mock.patch(
+            "prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc.awslambda_client",
+            new=Lambda(aws_provider),
+        ):
+            from prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc import (
+                awslambda_function_inside_vpc,
+            )
+
+            check = awslambda_function_inside_vpc()
+            result = check.execute()
+
+            assert len(result) == 1
+            assert result[0].status == "PASS"
+            assert (
+                result[0].status_extended
+                == "Lambda function test_function is inside of VPC vpc-123abc"
+            )
+            assert result[0].region == AWS_REGION_EU_WEST_1
+            assert result[0].resource_id == function_name
+            assert result[0].resource_arn == function_arn
+            assert result[0].resource_tags == [{}]
+
+    @mock_aws
+    def test_function_outside_vpc(self):
+        # Create IAM Role for Lambda Function
+        iam_client = client("iam", region_name=AWS_REGION_EU_WEST_1)
+        role_name = "test-role"
+        assume_role_policy_document = {
+            "Version": "2012-10-17",
+            "Statement": [
+                {
+                    "Effect": "Allow",
+                    "Principal": {"Service": "lambda.amazonaws.com"},
+                    "Action": "sts:AssumeRole",
+                }
+            ],
+        }
+        role_arn = iam_client.create_role(
+            RoleName=role_name,
+            AssumeRolePolicyDocument=dumps(assume_role_policy_document),
+        )["Role"]["Arn"]
+
+        # Create Lambda Function outside VPC
+        lambda_client = client("lambda", region_name=AWS_REGION_EU_WEST_1)
+        function_name = "test_function"
+        function_arn = lambda_client.create_function(
+            FunctionName=function_name,
+            Runtime="python3.8",
+            Role=role_arn,
+            Handler="lambda_function.lambda_handler",
+            Code={"ZipFile": b"file not used"},
+        )["FunctionArn"]
+
+        from prowler.providers.aws.services.awslambda.awslambda_service import Lambda
+
+        aws_provider = set_mocked_aws_provider([AWS_REGION_EU_WEST_1])
+
+        with mock.patch(
+            "prowler.providers.common.provider.Provider.get_global_provider",
+            return_value=aws_provider,
+        ), mock.patch(
+            "prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc.awslambda_client",
+            new=Lambda(aws_provider),
+        ):
+            from prowler.providers.aws.services.awslambda.awslambda_function_inside_vpc.awslambda_function_inside_vpc import (
+                awslambda_function_inside_vpc,
+            )
+
+            check = awslambda_function_inside_vpc()
+            result = check.execute()
+
+            assert len(result) == 1
+            assert result[0].status == "FAIL"
+            assert (
+                result[0].status_extended
+                == "Lambda function test_function is not inside a VPC"
+            )
+            assert result[0].region == AWS_REGION_EU_WEST_1
+            assert result[0].resource_id == function_name
+            assert result[0].resource_arn == function_arn
+            assert result[0].resource_tags == [{}]

tests/providers/aws/services/awslambda/awslambda_service_test.py

@@ -220,6 +220,7 @@ class Test_Lambda_Service:
             assert awslambda.functions[
                 lambda_arn_1
             ].url_config.cors_config.allow_origins == ["*"]
+            assert awslambda.functions[lambda_arn_1].vpc_id == "vpc-123abc"
 
             assert awslambda.functions[lambda_arn_1].tags == [{"test": "test"}]