main.tf

data "aws_partition" "current" {}

locals {
  create = var.create && var.putin_khuylo
  tags   = merge(var.tags, { terraform-aws-modules = "alb" })
}

################################################################################
# Load Balancer
################################################################################

resource "aws_lb" "this" {
  count = local.create ? 1 : 0

  dynamic "access_logs" {
    for_each = length(var.access_logs) > 0 ? [var.access_logs] : []

    content {
      bucket  = access_logs.value.bucket
      enabled = try(access_logs.value.enabled, true)
      prefix  = try(access_logs.value.prefix, null)
    }
  }

  dynamic "connection_logs" {
    for_each = length(var.connection_logs) > 0 ? [var.connection_logs] : []
    content {
      bucket  = connection_logs.value.bucket
      enabled = try(connection_logs.value.enabled, true)
      prefix  = try(connection_logs.value.prefix, null)
    }
  }

  client_keep_alive                                            = var.client_keep_alive
  customer_owned_ipv4_pool                                     = var.customer_owned_ipv4_pool
  desync_mitigation_mode                                       = var.desync_mitigation_mode
  dns_record_client_routing_policy                             = var.dns_record_client_routing_policy
  drop_invalid_header_fields                                   = var.drop_invalid_header_fields
  enable_cross_zone_load_balancing                             = var.enable_cross_zone_load_balancing
  enable_deletion_protection                                   = var.enable_deletion_protection
  enable_http2                                                 = var.enable_http2
  enable_tls_version_and_cipher_suite_headers                  = var.enable_tls_version_and_cipher_suite_headers
  enable_waf_fail_open                                         = var.enable_waf_fail_open
  enable_xff_client_port                                       = var.enable_xff_client_port
  enforce_security_group_inbound_rules_on_private_link_traffic = var.enforce_security_group_inbound_rules_on_private_link_traffic
  idle_timeout                                                 = var.idle_timeout
  internal                                                     = var.internal
  ip_address_type                                              = var.ip_address_type
  load_balancer_type                                           = var.load_balancer_type
  name                                                         = var.name
  name_prefix                                                  = var.name_prefix
  preserve_host_header                                         = var.preserve_host_header
  security_groups                                              = var.create_security_group ? concat([aws_security_group.this[0].id], var.security_groups) : var.security_groups

  dynamic "subnet_mapping" {
    for_each = var.subnet_mapping

    content {
      allocation_id        = lookup(subnet_mapping.value, "allocation_id", null)
      ipv6_address         = lookup(subnet_mapping.value, "ipv6_address", null)
      private_ipv4_address = lookup(subnet_mapping.value, "private_ipv4_address", null)
      subnet_id            = subnet_mapping.value.subnet_id
    }
  }

  subnets                    = var.subnets
  tags                       = local.tags
  xff_header_processing_mode = var.xff_header_processing_mode

  timeouts {
    create = try(var.timeouts.create, null)
    update = try(var.timeouts.update, null)
    delete = try(var.timeouts.delete, null)
  }

  lifecycle {
    ignore_changes = [
      tags["elasticbeanstalk:shared-elb-environment-count"]
    ]
  }
}

################################################################################
# Listener(s)
################################################################################

resource "aws_lb_listener" "this" {
  for_each = { for k, v in var.listeners : k => v if local.create }

  alpn_policy     = try(each.value.alpn_policy, null)
  certificate_arn = try(each.value.certificate_arn, null)

  dynamic "default_action" {
    for_each = try([each.value.authenticate_cognito], [])

    content {
      authenticate_cognito {
        authentication_request_extra_params = try(default_action.value.authentication_request_extra_params, null)
        on_unauthenticated_request          = try(default_action.value.on_unauthenticated_request, null)
        scope                               = try(default_action.value.scope, null)
        session_cookie_name                 = try(default_action.value.session_cookie_name, null)
        session_timeout                     = try(default_action.value.session_timeout, null)
        user_pool_arn                       = default_action.value.user_pool_arn
        user_pool_client_id                 = default_action.value.user_pool_client_id
        user_pool_domain                    = default_action.value.user_pool_domain
      }

      order = try(default_action.value.order, null)
      type  = "authenticate-cognito"
    }
  }

  dynamic "default_action" {
    for_each = try([each.value.authenticate_oidc], [])

    content {
      authenticate_oidc {
        authentication_request_extra_params = try(default_action.value.authentication_request_extra_params, null)
        authorization_endpoint              = default_action.value.authorization_endpoint
        client_id                           = default_action.value.client_id
        client_secret                       = default_action.value.client_secret
        issuer                              = default_action.value.issuer
        on_unauthenticated_request          = try(default_action.value.on_unauthenticated_request, null)
        scope                               = try(default_action.value.scope, null)
        session_cookie_name                 = try(default_action.value.session_cookie_name, null)
        session_timeout                     = try(default_action.value.session_timeout, null)
        token_endpoint                      = default_action.value.token_endpoint
        user_info_endpoint                  = default_action.value.user_info_endpoint
      }

      order = try(default_action.value.order, null)
      type  = "authenticate-oidc"
    }
  }

  dynamic "default_action" {
    for_each = try([each.value.fixed_response], [])

    content {
      fixed_response {
        content_type = default_action.value.content_type
        message_body = try(default_action.value.message_body, null)
        status_code  = try(default_action.value.status_code, null)
      }

      order = try(default_action.value.order, null)
      type  = "fixed-response"
    }
  }

  dynamic "default_action" {
    for_each = try([each.value.forward], [])

    content {
      order            = try(default_action.value.order, null)
      target_group_arn = length(try(default_action.value.target_groups, [])) > 0 ? null : try(default_action.value.arn, aws_lb_target_group.this[default_action.value.target_group_key].arn, null)
      type             = "forward"
    }
  }

  dynamic "default_action" {
    for_each = try([each.value.weighted_forward], [])

    content {
      forward {
        dynamic "target_group" {
          for_each = try(default_action.value.target_groups, [])

          content {
            arn    = try(target_group.value.arn, aws_lb_target_group.this[target_group.value.target_group_key].arn, null)
            weight = try(target_group.value.weight, null)
          }
        }

        dynamic "stickiness" {
          for_each = try([default_action.value.stickiness], [])

          content {
            duration = try(stickiness.value.duration, 60)
            enabled  = try(stickiness.value.enabled, null)
          }
        }
      }

      order = try(default_action.value.order, null)
      type  = "forward"
    }
  }

  dynamic "default_action" {
    for_each = try([each.value.redirect], [])

    content {
      order = try(default_action.value.order, null)

      redirect {
        host        = try(default_action.value.host, null)
        path        = try(default_action.value.path, null)
        port        = try(default_action.value.port, null)
        protocol    = try(default_action.value.protocol, null)
        query       = try(default_action.value.query, null)
        status_code = default_action.value.status_code
      }

      type = "redirect"
    }
  }

  dynamic "mutual_authentication" {
    for_each = try([each.value.mutual_authentication], [])
    content {
      mode                             = mutual_authentication.value.mode
      trust_store_arn                  = try(mutual_authentication.value.trust_store_arn, null)
      ignore_client_certificate_expiry = try(mutual_authentication.value.ignore_client_certificate_expiry, null)
    }
  }

  load_balancer_arn = aws_lb.this[0].arn
  port              = try(each.value.port, var.default_port)
  protocol          = try(each.value.protocol, var.default_protocol)
  ssl_policy        = contains(["HTTPS", "TLS"], try(each.value.protocol, var.default_protocol)) ? try(each.value.ssl_policy, "ELBSecurityPolicy-TLS13-1-2-Res-2021-06") : try(each.value.ssl_policy, null)
  tags              = merge(local.tags, try(each.value.tags, {}))
}

################################################################################
# Listener Rule(s)
################################################################################

locals {
  # This allows rules to be specified under the listener definition
  listener_rules = flatten([
    for listener_key, listener_values in var.listeners : [
      for rule_key, rule_values in lookup(listener_values, "rules", {}) :
      merge(rule_values, {
        listener_key = listener_key
        rule_key     = rule_key
      })
    ]
  ])
}

resource "aws_lb_listener_rule" "this" {
  for_each = { for v in local.listener_rules : "${v.listener_key}/${v.rule_key}" => v if local.create }

  listener_arn = try(each.value.listener_arn, aws_lb_listener.this[each.value.listener_key].arn)
  priority     = try(each.value.priority, null)

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "authenticate-cognito"]

    content {
      type  = "authenticate-cognito"
      order = try(action.value.order, null)

      authenticate_cognito {
        authentication_request_extra_params = try(action.value.authentication_request_extra_params, null)
        on_unauthenticated_request          = try(action.value.on_unauthenticated_request, null)
        scope                               = try(action.value.scope, null)
        session_cookie_name                 = try(action.value.session_cookie_name, null)
        session_timeout                     = try(action.value.session_timeout, null)
        user_pool_arn                       = action.value.user_pool_arn
        user_pool_client_id                 = action.value.user_pool_client_id
        user_pool_domain                    = action.value.user_pool_domain
      }
    }
  }

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "authenticate-oidc"]

    content {
      type  = "authenticate-oidc"
      order = try(action.value.order, null)

      authenticate_oidc {
        authentication_request_extra_params = try(action.value.authentication_request_extra_params, null)
        authorization_endpoint              = action.value.authorization_endpoint
        client_id                           = action.value.client_id
        client_secret                       = action.value.client_secret
        issuer                              = action.value.issuer
        on_unauthenticated_request          = try(action.value.on_unauthenticated_request, null)
        scope                               = try(action.value.scope, null)
        session_cookie_name                 = try(action.value.session_cookie_name, null)
        session_timeout                     = try(action.value.session_timeout, null)
        token_endpoint                      = action.value.token_endpoint
        user_info_endpoint                  = action.value.user_info_endpoint
      }
    }
  }

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "redirect"]

    content {
      type  = "redirect"
      order = try(action.value.order, null)

      redirect {
        host        = try(action.value.host, null)
        path        = try(action.value.path, null)
        port        = try(action.value.port, null)
        protocol    = try(action.value.protocol, null)
        query       = try(action.value.query, null)
        status_code = action.value.status_code
      }
    }
  }

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "fixed-response"]

    content {
      type  = "fixed-response"
      order = try(action.value.order, null)

      fixed_response {
        content_type = action.value.content_type
        message_body = try(action.value.message_body, null)
        status_code  = try(action.value.status_code, null)
      }
    }
  }

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "forward"]

    content {
      type             = "forward"
      order            = try(action.value.order, null)
      target_group_arn = try(action.value.target_group_arn, aws_lb_target_group.this[action.value.target_group_key].arn, null)
    }
  }

  dynamic "action" {
    for_each = [for action in each.value.actions : action if action.type == "weighted-forward"]

    content {
      type  = "forward"
      order = try(action.value.order, null)

      forward {
        dynamic "target_group" {
          for_each = try(action.value.target_groups, [])

          content {
            arn    = try(target_group.value.arn, aws_lb_target_group.this[target_group.value.target_group_key].arn)
            weight = try(target_group.value.weight, null)
          }
        }

        dynamic "stickiness" {
          for_each = try([action.value.stickiness], [])

          content {
            enabled  = try(stickiness.value.enabled, null)
            duration = try(stickiness.value.duration, 60)
          }
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "host_header")]

    content {
      dynamic "host_header" {
        for_each = try([condition.value.host_header], [])

        content {
          values = host_header.value.values
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "http_header")]

    content {
      dynamic "http_header" {
        for_each = try([condition.value.http_header], [])

        content {
          http_header_name = http_header.value.http_header_name
          values           = http_header.value.values
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "http_request_method")]

    content {
      dynamic "http_request_method" {
        for_each = try([condition.value.http_request_method], [])

        content {
          values = http_request_method.value.values
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "path_pattern")]

    content {
      dynamic "path_pattern" {
        for_each = try([condition.value.path_pattern], [])

        content {
          values = path_pattern.value.values
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "query_string")]

    content {
      dynamic "query_string" {
        for_each = try([condition.value.query_string], [])

        content {
          key   = try(query_string.value.key, null)
          value = query_string.value.value
        }
      }
    }
  }

  dynamic "condition" {
    for_each = [for condition in each.value.conditions : condition if contains(keys(condition), "source_ip")]

    content {
      dynamic "source_ip" {
        for_each = try([condition.value.source_ip], [])

        content {
          values = source_ip.value.values
        }
      }
    }
  }

  tags = merge(local.tags, try(each.value.tags, {}))
}

################################################################################
# Certificate(s)
################################################################################

locals {
  # Take the list of `additional_certificate_arns` from the listener and create
  # a map entry that maps each certificate to the listener key. This map of maps
  # is then used to create the certificate resources.
  additional_certs = merge(values({
    for listener_key, listener_values in var.listeners : listener_key =>
    {
      # This will cause certs to be detached and reattached if certificate_arns
      # towards the front of the list are updated/removed. However, we need to have
      # unique keys on the resulting map and we can't have computed values (i.e. cert ARN)
      # in the key so we are using the array index as part of the key.
      for idx, cert_arn in lookup(listener_values, "additional_certificate_arns", []) :
      "${listener_key}/${idx}" => {
        listener_key    = listener_key
        certificate_arn = cert_arn
      }
    } if length(lookup(listener_values, "additional_certificate_arns", [])) > 0
  })...)
}

resource "aws_lb_listener_certificate" "this" {
  for_each = { for k, v in local.additional_certs : k => v if local.create }

  listener_arn    = aws_lb_listener.this[each.value.listener_key].arn
  certificate_arn = each.value.certificate_arn
}

################################################################################
# Target Group(s)
################################################################################

resource "aws_lb_target_group" "this" {
  for_each = { for k, v in var.target_groups : k => v if local.create }

  connection_termination = try(each.value.connection_termination, null)
  deregistration_delay   = try(each.value.deregistration_delay, null)

  dynamic "health_check" {
    for_each = try([each.value.health_check], [])

    content {
      enabled             = try(health_check.value.enabled, null)
      healthy_threshold   = try(health_check.value.healthy_threshold, null)
      interval            = try(health_check.value.interval, null)
      matcher             = try(health_check.value.matcher, null)
      path                = try(health_check.value.path, null)
      port                = try(health_check.value.port, null)
      protocol            = try(health_check.value.protocol, null)
      timeout             = try(health_check.value.timeout, null)
      unhealthy_threshold = try(health_check.value.unhealthy_threshold, null)
    }
  }

  ip_address_type                    = try(each.value.ip_address_type, null)
  lambda_multi_value_headers_enabled = try(each.value.lambda_multi_value_headers_enabled, null)
  load_balancing_algorithm_type      = try(each.value.load_balancing_algorithm_type, null)
  load_balancing_anomaly_mitigation  = try(each.value.load_balancing_anomaly_mitigation, null)
  load_balancing_cross_zone_enabled  = try(each.value.load_balancing_cross_zone_enabled, null)
  name                               = try(each.value.name, null)
  name_prefix                        = try(each.value.name_prefix, null)
  port                               = try(each.value.target_type, null) == "lambda" ? null : try(each.value.port, var.default_port)
  preserve_client_ip                 = try(each.value.preserve_client_ip, null)
  protocol                           = try(each.value.target_type, null) == "lambda" ? null : try(each.value.protocol, var.default_protocol)
  protocol_version                   = try(each.value.protocol_version, null)
  proxy_protocol_v2                  = try(each.value.proxy_protocol_v2, null)
  slow_start                         = try(each.value.slow_start, null)

  dynamic "stickiness" {
    for_each = try([each.value.stickiness], [])

    content {
      cookie_duration = try(stickiness.value.cookie_duration, null)
      cookie_name     = try(stickiness.value.cookie_name, null)
      enabled         = try(stickiness.value.enabled, true)
      type            = var.load_balancer_type == "network" ? "source_ip" : stickiness.value.type
    }
  }

  dynamic "target_failover" {
    for_each = try(each.value.target_failover, [])

    content {
      on_deregistration = target_failover.value.on_deregistration
      on_unhealthy      = target_failover.value.on_unhealthy
    }
  }

  dynamic "target_health_state" {
    for_each = try([each.value.target_health_state], [])
    content {
      enable_unhealthy_connection_termination = try(target_health_state.value.enable_unhealthy_connection_termination, true)
    }
  }

  target_type = try(each.value.target_type, null)
  vpc_id      = try(each.value.vpc_id, var.vpc_id)

  tags = merge(local.tags, try(each.value.tags, {}))

  lifecycle {
    create_before_destroy = true
  }
}

################################################################################
# Target Group Attachment
################################################################################

resource "aws_lb_target_group_attachment" "this" {
  for_each = { for k, v in var.target_groups : k => v if local.create && lookup(v, "create_attachment", true) }

  target_group_arn  = aws_lb_target_group.this[each.key].arn
  target_id         = each.value.target_id
  port              = try(each.value.target_type, null) == "lambda" ? null : try(each.value.port, var.default_port)
  availability_zone = try(each.value.availability_zone, null)

  depends_on = [aws_lambda_permission.this]
}

resource "aws_lb_target_group_attachment" "additional" {
  for_each = { for k, v in var.additional_target_group_attachments : k => v if local.create }

  target_group_arn  = aws_lb_target_group.this[each.value.target_group_key].arn
  target_id         = each.value.target_id
  port              = try(each.value.target_type, null) == "lambda" ? null : try(each.value.port, var.default_port)
  availability_zone = try(each.value.availability_zone, null)

  depends_on = [aws_lambda_permission.this]
}

################################################################################
# Lambda Permission
################################################################################

# Filter out the attachments for lambda functions. The ALB target group needs
# permission to forward a request on to # the specified lambda function.
# This filtered list is used to create those permission resources. # To get the
# lambda_function_name, the 6th index is taken from the function ARN format below
# arn:aws:lambda:<region>:<account-id>:function:my-function-name:<version-number>
locals {
  lambda_target_groups = {
    for k, v in var.target_groups :
    (k) => merge(v, { lambda_function_name = split(":", v.target_id)[6] })
    if try(v.attach_lambda_permission, false)
  }
}

resource "aws_lambda_permission" "this" {
  for_each = { for k, v in local.lambda_target_groups : k => v if local.create }

  function_name = each.value.lambda_function_name
  qualifier     = try(each.value.lambda_qualifier, null)

  statement_id       = try(each.value.lambda_statement_id, "AllowExecutionFromLb")
  action             = try(each.value.lambda_action, "lambda:InvokeFunction")
  principal          = try(each.value.lambda_principal, "elasticloadbalancing.${data.aws_partition.current.dns_suffix}")
  source_arn         = aws_lb_target_group.this[each.key].arn
  source_account     = try(each.value.lambda_source_account, null)
  event_source_token = try(each.value.lambda_event_source_token, null)
}

################################################################################
# Security Group
################################################################################

locals {
  create_security_group = local.create && var.create_security_group
  security_group_name   = try(coalesce(var.security_group_name, var.name, var.name_prefix), "")
}

resource "aws_security_group" "this" {
  count = local.create_security_group ? 1 : 0

  name        = var.security_group_use_name_prefix ? null : local.security_group_name
  name_prefix = var.security_group_use_name_prefix ? "${local.security_group_name}-" : null
  description = coalesce(var.security_group_description, "Security group for ${local.security_group_name} ${var.load_balancer_type} load balancer")
  vpc_id      = var.vpc_id

  tags = merge(local.tags, var.security_group_tags)

  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_vpc_security_group_egress_rule" "this" {
  for_each = { for k, v in var.security_group_egress_rules : k => v if local.create_security_group }

  # Required
  security_group_id = aws_security_group.this[0].id
  ip_protocol       = try(each.value.ip_protocol, "tcp")

  # Optional
  cidr_ipv4                    = lookup(each.value, "cidr_ipv4", null)
  cidr_ipv6                    = lookup(each.value, "cidr_ipv6", null)
  description                  = try(each.value.description, null)
  from_port                    = try(each.value.from_port, null)
  prefix_list_id               = lookup(each.value, "prefix_list_id", null)
  referenced_security_group_id = lookup(each.value, "referenced_security_group_id", null)
  to_port                      = try(each.value.to_port, null)

  tags = merge(local.tags, var.security_group_tags, try(each.value.tags, {}))
}

resource "aws_vpc_security_group_ingress_rule" "this" {
  for_each = { for k, v in var.security_group_ingress_rules : k => v if local.create_security_group }

  # Required
  security_group_id = aws_security_group.this[0].id
  ip_protocol       = try(each.value.ip_protocol, "tcp")

  # Optional
  cidr_ipv4                    = lookup(each.value, "cidr_ipv4", null)
  cidr_ipv6                    = lookup(each.value, "cidr_ipv6", null)
  description                  = try(each.value.description, null)
  from_port                    = try(each.value.from_port, null)
  prefix_list_id               = lookup(each.value, "prefix_list_id", null)
  referenced_security_group_id = lookup(each.value, "referenced_security_group_id", null)
  to_port                      = try(each.value.to_port, null)

  tags = merge(local.tags, var.security_group_tags, try(each.value.tags, {}))
}

################################################################################
# Route53 Record(s)
################################################################################

resource "aws_route53_record" "this" {
  for_each = { for k, v in var.route53_records : k => v if var.create }

  zone_id = each.value.zone_id
  name    = try(each.value.name, each.key)
  type    = each.value.type

  alias {
    name                   = aws_lb.this[0].dns_name
    zone_id                = aws_lb.this[0].zone_id
    evaluate_target_health = true
  }
}

################################################################################
# WAF
################################################################################

resource "aws_wafv2_web_acl_association" "this" {
  count = var.associate_web_acl ? 1 : 0

  resource_arn = aws_lb.this[0].arn
  web_acl_arn  = var.web_acl_arn
}