TerraformでJSONを扱う方法

Terraformでjsonを利用する際の方法をまとめました。
AWSはIPアドレスのレンジをjsonで公開していたりするので、Terraformでアクセス許可設定するときなど便利そうです。（例として利用します）

v0.12 から使えるようになった For Expression (jsondecodeもだけど) がとても便利で、下の例のようにregionやserviceで絞り込むことも出来るのでかなり使いやすいと思います。

AWS IP range: https://ip-ranges.amazonaws.com/ip-ranges.json

ローカルのjsonを利用

output "local_aws_ip_range" {
  value = [ for prefix in jsondecode(file("./ip-range.json"))["prefixes"] : prefix.ip_prefix if prefix.region == "ap-northeast-1" && prefix.service == "EC2" ]
}

# 出力結果
local_aws_ip_range = [
  "52.194.0.0/15",
  "54.168.0.0/16",
  "54.238.0.0/16",
  "54.250.0.0/16",
  "54.92.0.0/17",
  "18.183.0.0/16",
  "176.32.64.0/19",
  "52.196.0.0/14",
  "175.41.192.0/18",
  "54.150.0.0/16",
  "99.77.139.0/24",
  "54.199.0.0/16",
  "176.34.32.0/19",
  "54.248.0.0/15",
  "18.182.0.0/16",
  "13.112.0.0/14",
  "52.68.0.0/15",
  "52.94.248.80/28",
  "54.95.0.0/16",
  "52.95.243.0/24",
  "3.112.0.0/14",
  "18.178.0.0/16",
  "52.192.0.0/15",
  "13.230.0.0/15",
  "54.178.0.0/16",
  "18.180.0.0/15",
  "52.95.255.48/28",
  "103.4.8.0/21",
  "18.179.0.0/16",
  "46.51.224.0/19",
  "54.64.0.0/15",
  "176.34.0.0/19",
  "18.176.0.0/15",
  "15.193.1.0/24",
]

HTTPで取得したjsonを利用

data "http" "aws_ip_range" {
  url = "https://ip-ranges.amazonaws.com/ip-ranges.json"
}

output "aws_ip_range" {
  value = [ for prefix in jsondecode(data.http.aws_ip_range.body)["prefixes"] : prefix.ip_prefix if prefix.region == "ap-northeast-1" && prefix.service == "EC2" ]
}

# 出力結果
aws_ip_range = [
  "52.194.0.0/15",
  "54.168.0.0/16",
  "54.238.0.0/16",
  "54.250.0.0/16",
  "54.92.0.0/17",
  "18.183.0.0/16",
  "176.32.64.0/19",
  "52.196.0.0/14",
  "175.41.192.0/18",
  "54.150.0.0/16",
  "99.77.139.0/24",
  "54.199.0.0/16",
  "176.34.32.0/19",
  "54.248.0.0/15",
  "18.182.0.0/16",
  "13.112.0.0/14",
  "52.68.0.0/15",
  "52.94.248.80/28",
  "54.95.0.0/16",
  "52.95.243.0/24",
  "3.112.0.0/14",
  "18.178.0.0/16",
  "52.192.0.0/15",
  "13.230.0.0/15",
  "54.178.0.0/16",
  "18.180.0.0/15",
  "52.95.255.48/28",
  "103.4.8.0/21",
  "18.179.0.0/16",
  "46.51.224.0/19",
  "54.64.0.0/15",
  "176.34.0.0/19",
  "18.176.0.0/15",
  "15.193.1.0/24",
]