Lambda created using Terraform is not authorized to perform: secretsmanager:GetSecretValue

Question

I am trying to access my AWS RDS from a Lambda function using IAM authentication. I have stored the secrets using secret manager. I am using terraform to provision all the services. 
**I am getting the following error:**
software.amazon.awssdk.services.secretsmanager.model.SecretsManagerException: User: arn:aws:sts:::assumed-role/poc-da37e8d3/poc-forms-da37e8d3 is not authorized to perform: secretsmanager:GetSecretValue because no identity-based policy allows the secretsmanager:GetSecretValue action (Service: SecretsManager, Status Code: 400, Request ID: 915700aa-bbc2-49c8-8082-af6635642755)
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is software.amazon.awssdk.services.secretsmanager.model.SecretsManagerException: User: arn:aws:sts:::assumed-role/poc-da37e8d3/poc-forms-da37e8d3 is not authorized to perform: secretsmanager:GetSecretValue because no identity-based policy allows the secretsmanager:GetSecretValue action (Service: SecretsManager, Status Code: 400, Request ID: 915700aa-bbc2-49c8-8082-af6635642755)
Can anyone please help me to resolve this issue?

**My Terraform code snippet:**
module "my_lambda" {
  source = "git::https://bitbucket..com/scm//aws-lambda.git"
  id                         = local.id
  name                       = "${var.name}-mylmbda"
  description                = "Lambda" 
  handler_prefix             = "com.my_forms_api"
  handler_suffix             = "ApiHandler::handleRequest"  
  source_folder_zip_dir      = "${path.module}/app/src/forms-api.zip"
  runtime                    = "java11"
  timeout                    = 30
  memory_size                = 1024
  vpc_subnet_ids             = var.vpc_subnet_ids 
  vpc_security_group_ids     = var.vpc_security_group_ids
  environment_variables      = { secret_name = data.aws_secretsmanager_secret.secretkey.name }
  invoke_function_permission = [{ "apigateway.amazonaws.com" = "arn:aws:execute-api:${local.region}:${local.account_id}:${module.aws_api_gateway.id}/*/*/*" }]    
  use_existing_role          = true
  existing_role_arn          = module.lambda_role.arn
  tags = local.tags
}
module "lambda_role" {
  source             = "git::https://bitbucket..com/scm//iam-role.git"
  assume_role_policy = data.aws_iam_policy_document.assume_role_policy.json
  id                 = local.id
  name               = var.name
  description        = "IAM role for lambda."
  inline_policy_docs = [data.aws_iam_policy_document.lambda_execution_policy.json]
  tags               = local.tags
}

data "aws_iam_policy_document" "assume_role_policy" {
  statement {
    actions = ["sts:AssumeRole"]
    principals {
      type        = "Service"
      identifiers = ["lambda.amazonaws.com"]
    }
  }
}

data "aws_iam_policy_document" "lambda_execution_policy" {
  statement {
    actions = [
      "rds-db:connect"
    ]
    effect    = "Allow"
    resources = [
             "arn:aws:rds-db:${local.region}:${local.account_id}:dbuser:${var.dbresourceid}/${var.dbuser}"
         ]
  }
  statement {
    actions = [
      "logs:CreateLogGroup",
      "logs:CreateLogStream",
      "logs:PutLogEvents"
    ]
    effect    = "Allow"
    resources = ["arn:aws:logs:*:*:*"]
  }
  statement {
    actions = [
      "ec2:CreateNetworkInterface",
      "ec2:DeleteNetworkInterface",
      "ec2:DescribeNetworkInterfaces"
    ]
    effect    = "Allow"
    resources = ["*"]
  }
  statement {
    actions = [
      "logs:CreateLogGroup",
      "logs:CreateLogStream",
      "logs:PutLogEvents",
      "ec2:CreateNetworkInterface",
      "ec2:DescribeNetworkInterfaces",
      "ec2:DeleteNetworkInterface",
      "ec2:AssignPrivateIpAddresses",
      "ec2:UnassignPrivateIpAddresses"
    ]
    effect    = "Allow"
    resources = ["*"]
  }
  statement {
    actions = [
      "secretsmanager:GetResourcePolicy",
      "secretsmanager:GetSecretValue",
      "secretsmanager:DescribeSecret",
      "secretsmanager:ListSecretVersionIds"
    ]
    effect    = "Allow"
    resources = ["arn:aws:secretsmanager:${local.region}:${local.account_id}:secret:${var.secretname_arn}"]
  }
}

data "aws_secretsmanager_secret" "secretkey" {  
  arn = "arn:aws:secretsmanager:${local.region}:${local.account_id}:secret:${var.secretname_arn}"
}

Accepted Answer

I could solve the issue.
Issue was with my java code.
Previously I was using this line of code to create SecretsManagerClient -

var secretsManagerClient = SecretsManagerClient.create();
but using this piece of code solved the issue -

SecretsManagerClient secretsManagerClient = SecretsManagerClient.builder()
                .region(region)
                .build();

Answer

The error message indicates that the role used by the lambda function doesn't have "secretsmanager:GetSecretValue" permission.

You may want to check for the following-

1. In the role attached to the lambda function, check that the action "secretsmanager:GetSecretValue" is allowed for the SecretsManager secret it is trying to access. Looking at the code snippet, this seems to be configured, but double-check.
Here is a sample permission.

`{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "secretsmanager:GetSecretValue",
      "Resource": "SecretARN"
    }
  ]
}`

2. In the SecretsManager, check the resource policy attached to the secret. It should allow "secretsmanager:GetSecretValue". Here is a sample permission.

`{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::123456789012:role/MyRole"
            },
            "Action": "secretsmanager:GetSecretValue",
            "Resource": "*"
        }
    ]
}`

3. Finally, if the secret is encrypted using a KMS key, then the role attached to the lambda function should also have "kms:Decrypt" permission.

Answer

Hi,

Is rds database in same vpc? In that case you need a vpc interface endpoint to access it.

If in same vpc, look for security groups setup.

A nice guide can be found here: https://repost.aws/knowledge-center/connect-lambda-to-an-rds-instance

Lambda created using Terraform is not authorized to perform: secretsmanager:GetSecretValue

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