Written by: ilmarkerm

Category: Blog entry

Published: April 14, 2024

Here I’m exploring how to control the basic network level resource security accesses. In AWS there is a concept called Security Groups. In OCI Oracle Cloud the similar concept is called Network Security Groups, also there is a little bit less powerful concept called Security Lists. A good imprevement with Network Security Groups over Security Lists is that in rules you can refer to other NSGs, not only CIDR.

Below I create two NSG – one for databases and one for application servers, and allow unrestricted outgoing traffc from them both.

# security.tf

# Rules for appservers

resource "oci_core_network_security_group" "appserver" {
    compartment_id = oci_identity_compartment.compartment.id
    vcn_id = oci_core_vcn.main.id
    display_name = "Application servers"
}

resource "oci_core_network_security_group_security_rule" "appserver_egress" {
    network_security_group_id = oci_core_network_security_group.appserver.id
    direction = "EGRESS"
    protocol = "all"
    description = "Allow all Egress traffic"
    destination = "0.0.0.0/0"
    destination_type = "CIDR_BLOCK"
}

# Rules for databases

resource "oci_core_network_security_group" "db" {
    compartment_id = oci_identity_compartment.compartment.id
    vcn_id = oci_core_vcn.main.id
    display_name = "Databases"
}

resource "oci_core_network_security_group_security_rule" "db_egress" {
    network_security_group_id = oci_core_network_security_group.db.id
    direction = "EGRESS"
    protocol = "all"
    description = "Allow all Egress traffic"
    destination = "0.0.0.0/0"
    destination_type = "CIDR_BLOCK"
}

Some rule examples to allow traffic from appservers towards databases. Here referring to the appserver NSG as source – not a CIDR.

# This rule allows port 1521/tcp to be accessed from NSG "appserver" created earlier
resource "oci_core_network_security_group_security_rule" "db_appserver_oracle" {
    network_security_group_id = oci_core_network_security_group.db.id
    direction = "INGRESS"
    protocol = "6" # TCP
    description = "Allow ingress from application servers to 1521/tcp"
    source_type = "NETWORK_SECURITY_GROUP"
    source = oci_core_network_security_group.appserver.id
    tcp_options {
        destination_port_range {
            min = 1521
            max = 1521
        }
    }
}

# This rule allows port 5432/tcp to be accessed from NSG "appserver" created earlier
resource "oci_core_network_security_group_security_rule" "db_appserver_postgres" {
    network_security_group_id = oci_core_network_security_group.db.id
    direction = "INGRESS"
    protocol = "6" # TCP
    description = "Allow ingress from application servers to 5432/tcp"
    source_type = "NETWORK_SECURITY_GROUP"
    source = oci_core_network_security_group.appserver.id
    tcp_options {
        destination_port_range {
            min = 5432
            max = 5432
        }
    }
}

And one example rule for appserver group, here I just want to show that the source NSG can refer to itself – so the port is open only to resources placed in the same NSG.

# This rule allows port 80/tcp to be accessed from the NSG itself
# Example use - the application is running unencrypted HTTP and is expected to have a loadbalancer in front, that does the encryption. In this case loadbalancer could be put to the same NSG.
# Or if the different application servers need to have a backbone communication port between each other - like cluster interconnect
resource "oci_core_network_security_group_security_rule" "appserver_http" {
    network_security_group_id = oci_core_network_security_group.appserver.id
    direction = "INGRESS"
    protocol = "6" # TCP
    description = "Allow access port port 80/tcp only from current NSG (self)"
    source_type = "NETWORK_SECURITY_GROUP"
    source = oci_core_network_security_group.appserver.id
    tcp_options {
        destination_port_range {
            min = 80
            max = 80
        }
    }
}

Now, network security groups need to be attached to the resources they are intended to protect. NSG-s are attached to the virtual network adapers VNICs.

To attach NSG to my previously created compute instance, I have to go back and edit the compute instance declaration to attach a NSG to the primary VNIC of that instance.

# compute.tf

resource "oci_core_instance" "arm_instance" {
    compartment_id = oci_identity_compartment.compartment.id
    # oci iam availability-domain list
    availability_domain = "MpAX:EU-STOCKHOLM-1-AD-1"
    # oci compute shape list --compartment-id 
    shape = "VM.Standard.A1.Flex" # ARM based shape
    shape_config {
        # How many CPUs and memory
        ocpus = 2
        memory_in_gbs = 4
    }
    display_name = "test-arm-1"
    source_details {
        # The source operating system image
        # oci compute image list --all --output table --compartment-id 
        source_id = data.oci_core_images.oel.images[0].id
        source_type = "image"
    }
    create_vnic_details {
        # Network details
        subnet_id = oci_core_subnet.subnet.id
        assign_public_ip = true
        # attaching Network Security Groups - NSGs
        nsg_ids = [oci_core_network_security_group.appserver.id]
    }
    # CloudInit metadata - including my public SSH key
    metadata = {
        ssh_authorized_keys = "ssh-rsa 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 ilmars_public_key"
    }
}

Written by: ilmarkerm

Category: Blog entry

Published: March 24, 2024

I thought I’ll start exploring Oracle Cloud offerings a little and try building something with Terraform.

The execution environment

OCI Could Console offers Cloud Shell and Code Editor right from the browser. Cloud Shell is a small Oracle Linux container with shell access, that has the most popular cloud tools and OCI SDKs already deployed. Most importantly, however, all Oracle Cloud API commands you execute from there, they run silently as yourself, no additional setup required. Including setting up terraform. Pretty awesome idea I would say – no need to set up any admin computer first.

Since I would mainly write code, I’m going to use only only Code Editor (which is actually VS Code in your browser) and VS Code also has a built in terminal for executing commands.

Read about executing and using Cloud Shell here.

Setting up Terraform provider

When executing from Cloud Shell / Code Editor, then setting up the terraform provider is very simple.

# versions.tf

provider "oci" {
   region = "eu-stockholm-1"
}

It is very good practice to also place terraform state file in the shared object store. OCI also provides an object store and to set it up first create a Bucket in Object Storage.

This also requires setting up Customer Secret Keys, for accessing the bucket using S3 protocol. I’m going to save my access key and secret access key in a file named bucket.credentials.

# bucket.credentials

[default]
aws_access_key_id=here is your access key
aws_secret_access_key=here is your secret access key


# remote_state.tf

terraform {
    backend "s3" {
        bucket = "oci-terraform-bucket"
        key    = "oci-terraform.tfstate"
        region = "eu-stockholm-1"
        # ax9u97qgbo5h is the namespace of the bucket, it is shown in the Bucket Details page
        endpoint = "https://ax9u97qgbo5h.compat.objectstorage.eu-stockholm-1.oraclecloud.com"
        shared_credentials_file     = "bucket.credentials"
        skip_region_validation      = true
        skip_credentials_validation = true
        skip_metadata_api_check     = true
        force_path_style            = true
    }
}

Creating compartment and basic networking

Compartment is just a handy hierarchical logical container which helps to organise your Oracle Cloud resources better. It can also be used to set common tags for all resources created under it.

# main.tf

locals {
    tenancy_id = "ocid1.tenancy.oc1..aaaaaaaawf2fv3ipfdp564ffiqpfqr6u6n3uofydgtihq3wget5357lq5i6a"
    environment = "dev"
}

# Information about current tenancy, for example home region
data "oci_identity_tenancy" "tenancy" {
    tenancy_id = local.tenancy_id
}

# Get the parent compartment as a terraform object
data "oci_identity_compartment" "parent_compartment" {
    # Top get list of existing compartments execute:
    # oci iam compartment list
    id = data.oci_identity_tenancy.tenancy.id
}

# Create compartment
resource "oci_identity_compartment" "compartment" {
    # Compartment_id must be the parent compartment ID and it is required
    compartment_id = data.oci_identity_compartment.parent_compartment.id
    description = "oci-terraform experiments"
    name = "oci-terraform-experiments"
    # Define some default tags that are added to all resources created under this compartment
    freeform_tags = {
        "deployed_by" = "terraform"
        "environment" = local.environment
    }
}

To set up networking, first you need VCN Virtual Cloud Network and under it subnets.

# network.tf

resource "oci_core_vcn" "main" {
    compartment_id = oci_identity_compartment.compartment.id
    display_name = "VCN for oci-terraform test"
    dns_label = "ocitf"
    cidr_blocks = ["10.1.2.0/24"]
    is_ipv6enabled = false
}

resource "oci_core_subnet" "subnet" {
    cidr_block = "10.1.2.0/25"
    compartment_id = oci_identity_compartment.compartment.id
    vcn_id = oci_core_vcn.main.id

    # List availability domains
    # oci iam availability-domain list
    # Documentation recommends creating regional subnets instead, without specifying availability_domain
    #availability_domain = "MpAX:EU-STOCKHOLM-1-AD-1"
    display_name = "Subdomain #1"
    prohibit_internet_ingress = false
    prohibit_public_ip_on_vnic = false
}

To be continued

I don’t really know where this post series is going. I’ve done quite a bit of Terraforming in AWS, so here I’m just exporing what Oracle Cloud has to offer and instead of using the dreaded ClickOps, I’ll try to be proper with Terraform.

At the end of the post I have these resources created.