From a1acb616aac8ed21ad8aa3274ed980193bfee148 Mon Sep 17 00:00:00 2001 From: Uzair Haroon Date: Wed, 10 Jun 2026 12:35:37 +0100 Subject: [PATCH] Created initial ALB/NLB module --- infrastructure/modules/alb/README.md | 197 +++++++++++++ infrastructure/modules/alb/context.tf | 374 ++++++++++++++++++++++++ infrastructure/modules/alb/main.tf | 68 +++++ infrastructure/modules/alb/outputs.tf | 44 +++ infrastructure/modules/alb/variables.tf | 110 +++++++ infrastructure/modules/alb/versions.tf | 10 + 6 files changed, 803 insertions(+) create mode 100644 infrastructure/modules/alb/README.md create mode 100644 infrastructure/modules/alb/context.tf create mode 100644 infrastructure/modules/alb/main.tf create mode 100644 infrastructure/modules/alb/outputs.tf create mode 100644 infrastructure/modules/alb/variables.tf create mode 100644 infrastructure/modules/alb/versions.tf diff --git a/infrastructure/modules/alb/README.md b/infrastructure/modules/alb/README.md new file mode 100644 index 0000000..54bdbec --- /dev/null +++ b/infrastructure/modules/alb/README.md @@ -0,0 +1,197 @@ +# AWS Application / Network Load Balancer Terraform module + +Thin NHS wrapper around [terraform-aws-modules/alb/aws](https://registry.terraform.io/modules/terraform-aws-modules/alb/aws) that enforces the screening platform's baseline controls. + +## Fixed controls + +| Setting | Value | Reason | +|---|---|---| +| `enable_deletion_protection` | `true` | Prevents accidental load balancer deletion via the AWS API | +| `drop_invalid_header_fields` | `true` (ALB only) | Prevents HTTP header injection attacks | + +## Usage + +### Internet-facing ALB with HTTPS + +```hcl +module "alb" { + source = "../../modules/alb" + + context = module.this.context + stack = "web" + name = "bcss-web" + label_order = ["service", "environment", "stack", "name"] + + vpc_id = data.aws_vpc.selected.id + subnets = data.aws_subnets.public.ids + + access_logs = { + bucket = module.logs_bucket.id + prefix = terraform.workspace + enabled = true + } + + security_group_ingress_rules = { + http = { + from_port = 80 + to_port = 80 + ip_protocol = "tcp" + description = "HTTP from internet — redirected to HTTPS by listener" + cidr_ipv4 = "0.0.0.0/0" + } + https = { + from_port = 443 + to_port = 443 + ip_protocol = "tcp" + description = "HTTPS from internet" + cidr_ipv4 = "0.0.0.0/0" + } + } + + security_group_egress_rules = { + https_out = { + from_port = 443 + to_port = 443 + ip_protocol = "tcp" + description = "HTTPS to targets" + cidr_ipv4 = "0.0.0.0/0" + } + } + + listeners = { + http-redirect = { + port = 80 + protocol = "HTTP" + redirect = { + port = "443" + protocol = "HTTPS" + status_code = "HTTP_301" + } + } + https = { + port = 443 + protocol = "HTTPS" + ssl_policy = "ELBSecurityPolicy-TLS13-1-2-Res-2021-06" + certificate_arn = local.acm_certificate_arn + forward = { + target_group_key = "web" + } + } + } + + target_groups = { + web = { + port = 443 + protocol = "HTTPS" + target_type = "ip" + health_check = { + protocol = "HTTPS" + path = "/health" + matcher = "200" + healthy_threshold = 2 + unhealthy_threshold = 2 + interval = 60 + } + } + } +} +``` + +### ALB with WAF association + +```hcl +module "alb" { + source = "../../modules/alb" + + context = module.this.context + name = "bcss-web" + + vpc_id = data.aws_vpc.selected.id + subnets = data.aws_subnets.public.ids + + listeners = { ... } + target_groups = { ... } + + web_acl_arn = module.waf.web_acl_arn +} +``` + +### Internal NLB + +```hcl +module "nlb" { + source = "../../modules/alb" + + context = module.this.context + name = "internal-nlb" + + load_balancer_type = "network" + internal = true + vpc_id = data.aws_vpc.selected.id + subnets = data.aws_subnets.private.ids + + security_group_ingress_rules = { + tcp = { + from_port = 8080 + to_port = 8080 + ip_protocol = "tcp" + description = "Internal TCP traffic" + cidr_ipv4 = data.aws_vpc.selected.cidr_block + } + } + + security_group_egress_rules = { + tcp_out = { + from_port = 8080 + to_port = 8080 + ip_protocol = "tcp" + cidr_ipv4 = data.aws_vpc.selected.cidr_block + } + } + + listeners = { + tcp = { + port = 8080 + protocol = "TCP" + forward = { target_group_key = "service" } + } + } + + target_groups = { + service = { + port = 8080 + protocol = "TCP" + target_type = "ip" + health_check = { + protocol = "TCP" + port = "8080" + } + } + } +} +``` + +## Outputs + +| Name | Description | Used by | +|---|---|---| +| `arn` | ARN of the load balancer | WAF ACL association | +| `dns_name` | DNS name of the load balancer | Route53 alias records | +| `zone_id` | Hosted zone ID of the load balancer | Route53 alias records | +| `listeners` | Map of listeners and their attributes | ECS task `depends_on` | +| `target_groups` | Map of target groups and their attributes | ECS task `target_group_arn` | +| `security_group_id` | ID of the load balancer security group | ECS task security group rules | + + + + +## Requirements + +| Name | Version | +|---|---| +| terraform | >= 1.5.7 | +| aws | >= 6.28 | + + + + diff --git a/infrastructure/modules/alb/context.tf b/infrastructure/modules/alb/context.tf new file mode 100644 index 0000000..39d9b94 --- /dev/null +++ b/infrastructure/modules/alb/context.tf @@ -0,0 +1,374 @@ +# +# ONLY EDIT THIS FILE IN github.com/NHSDigital/screening-terraform-modules-aws/infrastructure/modules/tags +# All other instances of this file should be a copy of that one +# +# +# Copy this file from https://github.com/NHSDigital/screening-terraform-modules-aws/blob/master/infrastructure/modules/tags/exports/context.tf +# and then place it in your Terraform module to automatically get +# tag module standard configuration inputs suitable for passing +# to other modules. +# +# curl -sL https://raw.githubusercontent.com/NHSDigital/screening-terraform-modules-aws/master/infrastructure/modules/tags/exports/context.tf -o context.tf +# +# Modules should access the whole context as `module.this.context` +# to get the input variables with nulls for defaults, +# for example `context = module.this.context`, +# and access individual variables as `module.this.`, +# with final values filled in. +# +# For example, when using defaults, `module.this.context.delimiter` +# will be null, and `module.this.delimiter` will be `-` (hyphen). +# + +module "this" { + source = "../tags" + + service = var.service + project = var.project + region = var.region + environment = var.environment + stack = var.stack + workspace = var.workspace + name = var.name + delimiter = var.delimiter + attributes = var.attributes + tags = var.tags + additional_tag_map = var.additional_tag_map + label_order = var.label_order + regex_replace_chars = var.regex_replace_chars + id_length_limit = var.id_length_limit + label_key_case = var.label_key_case + label_value_case = var.label_value_case + terraform_source = coalesce(var.terraform_source, path.module) + descriptor_formats = var.descriptor_formats + labels_as_tags = var.labels_as_tags + + context = var.context +} + +# Copy contents of screening-terraform-modules-aws/tags/variables.tf here +# tflint-ignore: terraform_unused_declarations +variable "aws_region" { + type = string + description = "The AWS region" + default = "eu-west-2" + validation { + condition = contains(["eu-west-1", "eu-west-2", "us-east-1"], var.aws_region) + error_message = "AWS Region must be one of eu-west-1, eu-west-2, us-east-1" + } +} + +variable "context" { + type = any + default = { + enabled = true + service = null + project = null + region = null + environment = null + stack = null + workspace = null + name = null + delimiter = null + attributes = [] + tags = {} + additional_tag_map = {} + regex_replace_chars = null + label_order = [] + id_length_limit = null + label_key_case = null + label_value_case = null + terraform_source = null + descriptor_formats = {} + # Note: we have to use [] instead of null for unset lists due to + # https://github.com/hashicorp/terraform/issues/28137 + # which was not fixed until Terraform 1.0.0, + # but we want the default to be all the labels in `label_order` + # and we want users to be able to prevent all tag generation + # by setting `labels_as_tags` to `[]`, so we need + # a different sentinel to indicate "default" + labels_as_tags = ["unset"] + } + description = <<-EOT + Single object for setting entire context at once. + See description of individual variables for details. + Leave string and numeric variables as `null` to use default value. + Individual variable settings (non-null) override settings in context object, + except for attributes, tags, and additional_tag_map, which are merged. + EOT + + validation { + condition = lookup(var.context, "label_key_case", null) == null ? true : contains(["lower", "title", "upper"], var.context["label_key_case"]) + error_message = "Allowed values: `lower`, `title`, `upper`." + } + + validation { + condition = lookup(var.context, "label_value_case", null) == null ? true : contains(["lower", "title", "upper", "none"], var.context["label_value_case"]) + error_message = "Allowed values: `lower`, `title`, `upper`, `none`." + } +} + +variable "terraform_source" { + type = string + default = null + description = "Source location to record in the Terraform_source tag. Defaults to this module path." +} + +variable "enabled" { + type = bool + default = null + description = "Set to false to prevent the module from creating any resources" +} + +variable "service" { + type = string + default = null + description = "ID element. Usually an abbreviation of your service directorate name, e.g. 'bcss' or 'csms', to help ensure generated IDs are globally unique" +} + +variable "region" { + type = string + default = null + description = "ID element _(Rarely used, not included by default)_. Usually an abbreviation of the selected AWS region e.g. 'uw2', 'ew2' or 'gbl' for resources like IAM roles that have no region" +} + +variable "project" { + type = string + default = null + description = "ID element. A project identifier, indicating the name or role of the project the resource is for, such as `website` or `api`" +} +variable "stack" { + type = string + default = null + description = "ID element. The name of the stack/component, e.g. `database`, `web`, `waf`, `eks`" +} +variable "workspace" { + type = string + default = null + description = "ID element. The Terraform workspace, to help ensure generated IDs are unique across workspaces" +} +variable "environment" { + type = string + default = null + description = "ID element. Usually used to indicate role, e.g. 'prd', 'dev', 'test', 'preprod', 'prod', 'uat'" +} + +variable "name" { + type = string + default = null + description = <<-EOT + ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. + This is the only ID element not also included as a `tag`. + The "name" tag is set to the full `id` string. There is no tag with the value of the `name` input. + EOT +} + +variable "delimiter" { + type = string + default = null + description = <<-EOT + Delimiter to be used between ID elements. + Defaults to `-` (hyphen). Set to `""` to use no delimiter at all. + EOT +} + +variable "attributes" { + type = list(string) + default = [] + description = <<-EOT + ID element. Additional attributes (e.g. `workers` or `cluster`) to add to `id`, + in the order they appear in the list. New attributes are appended to the + end of the list. The elements of the list are joined by the `delimiter` + and treated as a single ID element. + EOT +} + +variable "labels_as_tags" { + type = set(string) + default = ["default"] + description = <<-EOT + Set of labels (ID elements) to include as tags in the `tags` output. + Default is to include all labels. + Tags with empty values will not be included in the `tags` output. + Set to `[]` to suppress all generated tags. + **Notes:** + The value of the `name` tag, if included, will be the `id`, not the `name`. + Unlike other `null-label` inputs, the initial setting of `labels_as_tags` cannot be + changed in later chained modules. Attempts to change it will be silently ignored. + EOT +} + +variable "tags" { + type = map(string) + default = {} + description = <<-EOT + Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`). + Neither the tag keys nor the tag values will be modified by this module. + EOT +} + +variable "additional_tag_map" { + type = map(string) + default = {} + description = <<-EOT + Additional key-value pairs to add to each map in `tags_as_list_of_maps`. Not added to `tags` or `id`. + This is for some rare cases where resources want additional configuration of tags + and therefore take a list of maps with tag key, value, and additional configuration. + EOT +} + +variable "label_order" { + type = list(string) + default = null + description = <<-EOT + The order in which the labels (ID elements) appear in the `id`. + Defaults to ["namespace", "environment", "stage", "name", "attributes"]. + You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present. + EOT +} + +variable "regex_replace_chars" { + type = string + default = null + description = <<-EOT + Terraform regular expression (regex) string. + Characters matching the regex will be removed from the ID elements. + If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits. + EOT +} + +variable "id_length_limit" { + type = number + default = null + description = <<-EOT + Limit `id` to this many characters (minimum 6). + Set to `0` for unlimited length. + Set to `null` for keep the existing setting, which defaults to `0`. + Does not affect `id_full`. + EOT + validation { + condition = var.id_length_limit == null ? true : var.id_length_limit >= 6 || var.id_length_limit == 0 + error_message = "The id_length_limit must be >= 6 if supplied (not null), or 0 for unlimited length." + } +} + +variable "label_key_case" { + type = string + default = null + description = <<-EOT + Controls the letter case of the `tags` keys (label names) for tags generated by this module. + Does not affect keys of tags passed in via the `tags` input. + Possible values: `lower`, `title`, `upper`. + Default value: `title`. + EOT + + validation { + condition = var.label_key_case == null ? true : contains(["lower", "title", "upper"], var.label_key_case) + error_message = "Allowed values: `lower`, `title`, `upper`." + } +} + +variable "label_value_case" { + type = string + default = null + description = <<-EOT + Controls the letter case of ID elements (labels) as included in `id`, + set as tag values, and output by this module individually. + Does not affect values of tags passed in via the `tags` input. + Possible values: `lower`, `title`, `upper` and `none` (no transformation). + Set this to `title` and set `delimiter` to `""` to yield Pascal Case IDs. + Default value: `lower`. + EOT + + validation { + condition = var.label_value_case == null ? true : contains(["lower", "title", "upper", "none"], var.label_value_case) + error_message = "Allowed values: `lower`, `title`, `upper`, `none`." + } +} + +variable "descriptor_formats" { + type = any + default = {} + description = <<-EOT + Describe additional descriptors to be output in the `descriptors` output map. + Map of maps. Keys are names of descriptors. Values are maps of the form + `{ + format = string + labels = list(string) + }` + (Type is `any` so the map values can later be enhanced to provide additional options.) + `format` is a Terraform format string to be passed to the `format()` function. + `labels` is a list of labels, in order, to pass to `format()` function. + Label values will be normalized before being passed to `format()` so they will be + identical to how they appear in `id`. + Default is `{}` (`descriptors` output will be empty). + EOT +} + +variable "owner" { + type = string + description = "The name and or NHS.net email address of the service owner" + default = "None" +} + +variable "tag_version" { + type = string + description = "Used to identify the tagging version in use" + default = "1.0" +} + +variable "data_classification" { + type = string + description = "Used to identify the data classification of the resource, e.g 1-5" + default = "n/a" + validation { + condition = contains(["n/a", "1", "2", "3", "4", "5"], var.data_classification) + error_message = "Data Classification must be \"n/a\" or between 1-5" + } +} + +variable "data_type" { + type = string + description = "The tag data_type" + default = "None" + validation { + condition = contains(["None", "PCD", "PID", "Anonymised", "UserAccount", "Audit"], var.data_type) + error_message = "Data Type must be one of None, PCD, PID, Anonymised, UserAccount, Audit" + } +} + + +variable "public_facing" { + type = bool + description = "Whether this resource is public facing" + default = false +} + +variable "service_category" { + type = string + description = "The tag service_category" + default = "n/a" + validation { + condition = contains(["n/a", "Bronze", "Silver", "Gold", "Platinum"], var.service_category) + error_message = "The Service Category must be one of n/a, Bronze, Silver, Gold, Platinum" + } +} +variable "on_off_pattern" { + type = string + description = "Used to turn resources on and off based on a time pattern" + default = "n/a" +} + +variable "application_role" { + type = string + description = "The role the application is performing" + default = "General" +} + +variable "tool" { + type = string + description = "The tool used to deploy the resource" + default = "Terraform" +} + +#### End of copy of screening-terraform-modules-aws/tags/variables.tf diff --git a/infrastructure/modules/alb/main.tf b/infrastructure/modules/alb/main.tf new file mode 100644 index 0000000..fe03f1a --- /dev/null +++ b/infrastructure/modules/alb/main.tf @@ -0,0 +1,68 @@ +################################################################ +# Application / Network Load Balancer +# +# Thin NHS wrapper around the community ALB module that enforces +# the screening platform's baseline controls: +# +# * Deletion protection: always enabled +# * Invalid header fields: always dropped (ALB only) +# * Naming: derived from context labels via module.this.id +# * Tagging: all NHS-required tags applied automatically +# * Enabled flag: create = module.this.enabled +# +# Inputs intentionally NOT exposed (hardcoded below): +# - enable_deletion_protection → always true +# - drop_invalid_header_fields → always true (ALB); null (NLB) +################################################################ + +module "alb" { + source = "terraform-aws-modules/alb/aws" + version = "10.5.0" + + create = module.this.enabled + + name = module.this.id + load_balancer_type = var.load_balancer_type + internal = var.internal + vpc_id = var.vpc_id + subnets = var.subnets + + # ---------------------------------------------------------------- + # Security baseline — hardcoded, callers cannot override. + # drop_invalid_header_fields is ALB-only; pass null for NLB so + # the upstream module does not error. + # ---------------------------------------------------------------- + enable_deletion_protection = true + drop_invalid_header_fields = var.load_balancer_type == "application" ? true : null + + # ---------------------------------------------------------------- + # Security group rules — caller-supplied so both ALB (HTTP+HTTPS) + # and NLB (TCP) patterns are supported. + # ---------------------------------------------------------------- + security_group_ingress_rules = var.security_group_ingress_rules + security_group_egress_rules = var.security_group_egress_rules + + # ---------------------------------------------------------------- + # Access logging to a caller-supplied S3 bucket. + # ---------------------------------------------------------------- + access_logs = var.access_logs + + # ---------------------------------------------------------------- + # Listeners and target groups — passed through as-is. + # Callers define the full listener/target group configuration + # including SSL policies, certificates, health checks, etc. + # ---------------------------------------------------------------- + listeners = var.listeners + target_groups = var.target_groups + + # ---------------------------------------------------------------- + # WAF association — optional, ALB only. + # ---------------------------------------------------------------- + associate_web_acl = var.web_acl_arn != null + web_acl_arn = var.web_acl_arn + + # ---------------------------------------------------------------- + # Tags — automatically populated from context. + # ---------------------------------------------------------------- + tags = module.this.tags +} diff --git a/infrastructure/modules/alb/outputs.tf b/infrastructure/modules/alb/outputs.tf new file mode 100644 index 0000000..6a659a9 --- /dev/null +++ b/infrastructure/modules/alb/outputs.tf @@ -0,0 +1,44 @@ +output "arn" { + description = "ARN of the load balancer. Used by WAF to associate a Web ACL." + value = module.alb.arn +} + +output "dns_name" { + description = "DNS name of the load balancer. Used by Route53 alias records." + value = module.alb.dns_name +} + +output "zone_id" { + description = "Hosted zone ID of the load balancer. Used by Route53 alias records." + value = module.alb.zone_id +} + +output "id" { + description = "ID of the load balancer (same as ARN)." + value = module.alb.id +} + +output "arn_suffix" { + description = "ARN suffix of the load balancer. Used with CloudWatch metrics." + value = module.alb.arn_suffix +} + +output "listeners" { + description = "Map of listeners created and their attributes. ECS tasks use this for depends_on." + value = module.alb.listeners +} + +output "target_groups" { + description = "Map of target groups created and their attributes. ECS tasks reference target_group ARNs from here." + value = module.alb.target_groups +} + +output "security_group_id" { + description = "ID of the security group created for the load balancer." + value = module.alb.security_group_id +} + +output "security_group_arn" { + description = "ARN of the security group created for the load balancer." + value = module.alb.security_group_arn +} diff --git a/infrastructure/modules/alb/variables.tf b/infrastructure/modules/alb/variables.tf new file mode 100644 index 0000000..e1bbcaf --- /dev/null +++ b/infrastructure/modules/alb/variables.tf @@ -0,0 +1,110 @@ +################################################################ +# ALB/NLB-specific inputs. +# +# Naming, tagging and the master `enabled` switch come from +# context.tf via `module.this`. +# +# Inputs intentionally NOT exposed (hardcoded in main.tf): +# - enable_deletion_protection → always true +# - drop_invalid_header_fields → always true for ALB +################################################################ + +variable "load_balancer_type" { + type = string + default = "application" + description = "Type of load balancer to create. Either 'application' (ALB) or 'network' (NLB)." + + validation { + condition = contains(["application", "network"], var.load_balancer_type) + error_message = "load_balancer_type must be 'application' or 'network'." + } +} + +variable "internal" { + type = bool + default = false + description = "When true, the load balancer is internal (private). When false, it is internet-facing. Defaults to false." +} + +variable "subnets" { + type = list(string) + description = "List of subnet IDs to attach to the load balancer. For internet-facing ALBs, use public subnets." +} + +variable "vpc_id" { + type = string + description = "ID of the VPC in which the load balancer security group will be created." +} + +variable "security_group_ingress_rules" { + type = any + default = {} + description = <<-EOT + Map of ingress rules to add to the load balancer security group. + Each key is a logical name; each value is an object describing the rule. + Example: + security_group_ingress_rules = { + https = { + from_port = 443 + to_port = 443 + ip_protocol = "tcp" + description = "HTTPS from internet" + cidr_ipv4 = "0.0.0.0/0" + } + } + EOT +} + +variable "security_group_egress_rules" { + type = any + default = {} + description = <<-EOT + Map of egress rules to add to the load balancer security group. + Example: + security_group_egress_rules = { + https_out = { + from_port = 443 + to_port = 443 + ip_protocol = "tcp" + cidr_ipv4 = "0.0.0.0/0" + } + } + EOT +} + +variable "access_logs" { + type = object({ + bucket = string + prefix = optional(string) + enabled = optional(bool, true) + }) + default = null + description = "S3 access log delivery configuration. When null, access logging is disabled." +} + +variable "listeners" { + type = any + default = {} + description = <<-EOT + Map of listener configurations to create. Passed directly to the upstream module. + For ALB, define HTTPS and HTTP listeners here. For NLB, define TCP/TLS listeners. + See https://registry.terraform.io/modules/terraform-aws-modules/alb/aws/latest + for full schema documentation. + EOT +} + +variable "target_groups" { + type = any + default = {} + description = <<-EOT + Map of target group configurations to create. Passed directly to the upstream module. + See https://registry.terraform.io/modules/terraform-aws-modules/alb/aws/latest + for full schema documentation. + EOT +} + +variable "web_acl_arn" { + type = string + default = null + description = "ARN of a WAFv2 Web ACL to associate with the load balancer. Only valid for ALB. When null, no WAF association is created." +} diff --git a/infrastructure/modules/alb/versions.tf b/infrastructure/modules/alb/versions.tf new file mode 100644 index 0000000..d2afd5f --- /dev/null +++ b/infrastructure/modules/alb/versions.tf @@ -0,0 +1,10 @@ +terraform { + required_version = ">= 1.5.7" + + required_providers { + aws = { + source = "hashicorp/aws" + version = ">= 6.28" + } + } +}