Lambda With Vulnerable Policy

• Query id: ad9dabc7-7839-4bae-a957-aa9120013f39
• Query name: Lambda With Vulnerable Policy
• Platform: Terraform
• Severity: Medium
• Category: Access Control
• URL: Github

Description

The attribute 'action' should not have wildcard
Documentation

Code samples

Code samples with security vulnerabilities

Positive test num. 1 - tf file

provider "aws" {
  region = "us-east-1"
}

resource "aws_lambda_function" "my-lambda" {
  filename = "~/Downloads/lambda.json.zip"
  function_name = "my-lambda"
  role          = aws_iam_role.lambda-role.arn
  handler       = "lambda_function.lambda_handler"
  runtime = "python3.8"
}

resource "aws_iam_role" "lambda-role" {
  name = "lambda-role"

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}

resource "aws_lambda_permission" "all" {
  statement_id  = "AllowAllResources"
  action        = "lambda:*"
  function_name = aws_lambda_function.my-lambda.function_name
  principal     = "s3.amazonaws.com"
  source_arn    = "arn:aws:s3:::delete-me-us-east-1-permissions-tests"
  source_account = "111111111111"
  qualifier     = aws_lambda_alias.my-lambda-alias.name
}


resource "aws_lambda_alias" "my-lambda-alias" {
  name             = "v1"
  description      = "a sample description"
  function_name    = aws_lambda_function.my-lambda.function_name
  function_version = "$LATEST"
}

Code samples without security vulnerabilities

Negative test num. 1 - tf file

resource "aws_lambda_permission" "allow_cloudwatch" {
  statement_id  = "AllowExecutionFromCloudWatch"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.test_lambda.function_name
  principal     = "events.amazonaws.com"
  source_arn    = "arn:aws:events:eu-west-1:111122223333:rule/RunDaily"
  qualifier     = aws_lambda_alias.test_alias.name
}

resource "aws_lambda_alias" "test_alias" {
  name             = "testalias"
  description      = "a sample description"
  function_name    = aws_lambda_function.test_lambda.function_name
  function_version = "$LATEST"
}

resource "aws_lambda_function" "test_lambda" {
  filename      = "lambdatest.zip"
  function_name = "lambda_function_name"
  role          = aws_iam_role.iam_for_lambda.arn
  handler       = "exports.handler"
  runtime       = "nodejs12.x"
}

resource "aws_iam_role" "iam_for_lambda" {
  name = "iam_for_lambda"

  # Terraform's "jsonencode" function converts a
  # Terraform expression result to valid JSON syntax.
  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = "sts:AssumeRole"
        Effect = "Allow"
        Sid    = ""
        Principal = {
          Service = "lambda.amazonaws.com"
        }
      },
    ]
  })
}