eligibility-signposting-api/infrastructure/modules/lambda/kms.tf at f6d6de72f78f3de35120e91836adda95d5b3057c · NHSDigital/eligibility-signposting-api · GitHub

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resource "aws_kms_key" "lambda_cmk" {
  description             = "${terraform.workspace == "default" ? "" : "${terraform.workspace}-"}${var.lambda_func_name} Master Key"
  deletion_window_in_days = 14
  is_enabled              = true
  enable_key_rotation     = true
  tags                    = var.tags
}

resource "aws_kms_alias" "lambda_cmk" {
  name          = "alias/${terraform.workspace == "default" ? "" : "${terraform.workspace}-"}${var.lambda_func_name}-cmk"
  target_key_id = aws_kms_key.lambda_cmk.key_id
}

resource "aws_kms_key_policy" "lambda_cmk" {
  key_id = aws_kms_key.lambda_cmk.id
  policy = data.aws_iam_policy_document.lambda_cmk.json
}

data "aws_iam_policy_document" "lambda_cmk" {
  statement {
    sid    = "Enable IAM User Permissions for Lambda CMK"
    effect = "Allow"
    principals {
      type        = "AWS"
      identifiers = ["arn:aws:iam::${data.aws_caller_identity.current.account_id}:root"]
    }
    actions   = ["kms:*"]
    resources = [aws_kms_key.lambda_cmk.arn]
  }

  statement {
    sid    = "AllowCloudWatchLogsUseOfTheKey"
    effect = "Allow"
    principals {
      type        = "Service"
      identifiers = ["logs.${var.region}.amazonaws.com"]
    }
    actions = [
      "kms:Encrypt",
      "kms:Decrypt",
      "kms:ReEncrypt*",
      "kms:GenerateDataKey*",
      "kms:DescribeKey"
    ]
    resources = [aws_kms_key.lambda_cmk.arn]
  }
}