xdr-terraform-modules/base/standard_iam/codebuild.tf

#-----------------------------------------------------------------------
# Common AssumeRole policy for these codebuild roles
#-----------------------------------------------------------------------
data "aws_iam_policy_document" "codebuild_role_assume_role_policy" {
  statement {
    effect = "Allow"
    actions = [
      "sts:AssumeRole"
    ]
    principals {
      type = "Service"
      identifiers = [
        "codebuild.amazonaws.com",
        "events.amazonaws.com"
      ]
    }
  }
}

#-----------------------------------------------------------------------
# "Basic" Codebuild Role - not capable to make EC2 images / run Packer
#-----------------------------------------------------------------------
resource "aws_iam_role" "codebuild_basic_role" {
  name               = "codebuild_basic_role"
  path               = "/aws_services/"
  assume_role_policy = data.aws_iam_policy_document.codebuild_role_assume_role_policy.json
}

resource "aws_iam_role_policy_attachment" "codebuild_basic_role_basic_policy_attach" {
  role       = aws_iam_role.codebuild_basic_role.name
  policy_arn = aws_iam_policy.codebuild_basic_policy.arn
}

#-----------------------------------------------------------------------
# "Packer" Codebuild Role
#-----------------------------------------------------------------------
resource "aws_iam_role" "codebuild_packer_role" {
  name               = "codebuild_packer_role"
  path               = "/aws_services/"
  assume_role_policy = data.aws_iam_policy_document.codebuild_role_assume_role_policy.json
}

# Packer role needs basic role too for things like cloudwatch
resource "aws_iam_role_policy_attachment" "codebuild_packer_role_basic_policy_attach" {
  role       = aws_iam_role.codebuild_packer_role.name
  policy_arn = aws_iam_policy.codebuild_basic_policy.arn
}

resource "aws_iam_role_policy_attachment" "codebuild_packer_role_packer_policy_attach" {
  role       = aws_iam_role.codebuild_packer_role.name
  policy_arn = aws_iam_policy.codebuild_build_ec2_amis_policy.arn
}

#-----------------------------------------------------------------------
# "Basic" Policy for codebuild - can make artifacts and ECR images but not EC2
# FIXME: Not sure about this policy
#   2.  Lets codebuild (apparently) write to ANY ECR repo
#   4.  Latest codebuild policies (from AWS console) have report-group resources and actions
#-----------------------------------------------------------------------
resource "aws_iam_policy" "codebuild_basic_policy" {
  name        = "codebuild_basic_policy"
  path        = "/aws_services/"
  description = "Policy for AWS codebuild to build AMIs"
  policy      = data.aws_iam_policy_document.codebuild_base_policy.json
}

data "aws_iam_policy_document" "codebuild_base_policy" {
  statement {
    sid    = "WriteCodebuildLogsToCloudwatchLogs"
    effect = "Allow"
    resources = [
      "arn:${local.aws_partition}:logs:${local.aws_region}:${local.aws_account}:log-group:/aws/codebuild/*"
    ]
    actions = [
      "logs:CreateLogGroup",
      "logs:CreateLogStream",
      "logs:PutLogEvents"
    ]
  }

  statement {
    sid    = "StoreArtifactsInBucket"
    effect = "Allow"
    resources = [
      "arn:${local.aws_partition}:s3:::xdr-codebuild-artifacts/*"
    ]
    actions = [
      "s3:PutObject",
      "s3:GetObject*",
      "s3:ListBucket"
    ]
  }

  statement {
    sid    = "UpdateECRRepos"
    effect = "Allow"
    resources = [
      "*"
    ]
    actions = [
      "ecr:GetAuthorizationToken",
      "ecr:BatchCheckLayerAvailability",
      "ecr:CompleteLayerUpload",
      "ecr:GetAuthorizationToken",
      "ecr:InitiateLayerUpload",
      "ecr:PutImage",
      "ecr:UploadLayerPart"
    ]
  }

  statement {
    sid    = "LetEventBridgeTriggerABuild"
    effect = "Allow"
    resources = [
      "*"
    ]
    actions = [
      "codebuild:StartBuild",
      "codebuild:StopBuild",
      "codebuild:BatchGet*",
      "codebuild:Get*",
      "codebuild:List*"
    ]
  }
}

#-----------------------------------------------------------------------
# "EC2" Policy for codebuild - able to build EC2 images / SGs / etc
# FIXME:  too powerful
#
# Parts of this are Lifted from
# https://www.packer.io/plugins/builders/amazon#iam-task-or-instance-role and
# converted from JSON to a terraform data source NOT AUDITED - taking Packer
# docs at word that these are "minimal permissions necessary"
#
# The rest is for EBS+KMS support cobbled from AWS docs
#-----------------------------------------------------------------------
resource "aws_iam_policy" "codebuild_build_ec2_amis_policy" {
  name        = "codebuild_build_ami_policy"
  path        = "/aws_services/"
  description = "Policy for AWS codebuild to build AMIs"
  policy      = data.aws_iam_policy_document.codebuild_build_ec2_amis.json
}

data "aws_iam_policy_document" "codebuild_build_ec2_amis" {
	statement {
		sid       = "BuildEC2AMIFromPackerDocs"
		effect    = "Allow"
		resources = [ "*" ]
		actions   = [
			"ec2:AttachVolume",
			"ec2:AuthorizeSecurityGroupIngress",
			"ec2:CopyImage",
			"ec2:CreateImage",
			"ec2:CreateKeypair",
			"ec2:CreateSecurityGroup",
			"ec2:CreateSnapshot",
			"ec2:CreateTags",
			"ec2:CreateVolume",
			"ec2:CreateNetworkInterface",
			"ec2:CreateNetworkInterfacePermission",
			"ec2:DeleteKeyPair",
			"ec2:DeleteNetworkInterface",
			"ec2:DeleteSecurityGroup",
			"ec2:DeleteSnapshot",
			"ec2:DeleteVolume",
			"ec2:DeregisterImage",
			"ec2:Describe*",
			"ec2:DetachVolume",
			"ec2:GetPasswordData",
			"ec2:ModifyImageAttribute",
			"ec2:ModifyInstanceAttribute",
			"ec2:ModifySnapshotAttribute",
			"ec2:RegisterImage",
			"ec2:RunInstances",
			"ec2:StopInstances",
			"ec2:TerminateInstances"
		]
	}
	statement {
		sid       = "BuildEC2WithInstanceRole"
		effect    = "Allow"
		resources = [ "*" ]
		actions   = [
			"iam:PassRole"
		]
	}

	statement {
		sid       = "PullFromSecretsManager"
		effect    = "Allow"
		resources = [ 
			"arn:${local.aws_partition}:secretsmanager:${local.aws_region}:${local.aws_account}:secret:msoc-build*",
			"arn:${local.aws_partition}:secretsmanager:${local.aws_region}:${local.aws_account}:secret:mdr-aws-codebuild*" 
		]
		actions   = [
			"secretsmanager:GetSecretValue"
		]
	}

  statement {
		sid       = "KMSAccessNeededForEBS"
		effect    = "Allow"
		resources = [ "*" ]
    	actions   = [
			"kms:RevokeGrant",
			"kms:ListGrants",
			"kms:Decrypt",
			"kms:DescribeKey",
			"kms:GenerateDataKeyWithoutPlainText",
			"kms:ReEncrypt*",
		]
	}

    statement {
		sid       = "SSMCodeBuildPause"
		effect    = "Allow"
		resources = [ "*" ]
    	actions   = [
        "ssmmessages:CreateControlChannel",
        "ssmmessages:CreateDataChannel",
        "ssmmessages:OpenControlChannel",
        "ssmmessages:OpenDataChannel"
		]
	}

  statement {
    sid       = "CreateGrantForEBS"
    effect    = "Allow"
    resources = ["*"]
    actions = [
      "kms:CreateGrant",
    ]
    condition {
      test     = "Bool"
      variable = "kms:GrantIsForAWSResource"
      values   = ["true"]
    }
  }
}