Enabling subdomain isolation

About subdomain isolation

Subdomain isolation mitigates cross-site scripting and other related vulnerabilities. For more information, see "Cross-site scripting" on Wikipedia. We highly recommend that you enable subdomain isolation on your GitHub Enterprise Server instance.

When subdomain isolation is enabled, GitHub Enterprise Server replaces several paths with subdomains. After enabling subdomain isolation, attempts to access the previous paths for some user-supplied content, such as http(s)://HOSTNAME/raw/, may return 404 errors.

Path without subdomain isolation	Path with subdomain isolation
`http(s)://HOSTNAME/assets/`	`http(s)://assets.HOSTNAME/`
`http(s)://HOSTNAME/avatars/`	`http(s)://avatars.HOSTNAME/`
`http(s)://HOSTNAME/codeload/`	`http(s)://codeload.HOSTNAME/`
`http(s)://HOSTNAME/gist/`	`http(s)://gist.HOSTNAME/`
`http(s)://HOSTNAME/media/`	`http(s)://media.HOSTNAME/`
`http(s)://HOSTNAME/pages/`	`http(s)://pages.HOSTNAME/`
`http(s)://HOSTNAME/raw/`	`http(s)://raw.HOSTNAME/`
`http(s)://HOSTNAME/render/`	`http(s)://render.HOSTNAME/`
`http(s)://HOSTNAME/reply/`	`http(s)://reply.HOSTNAME/`
`http(s)://HOSTNAME/uploads/`	`http(s)://uploads.HOSTNAME/`
`https://HOSTNAME/`	`http(s)://docker.HOSTNAME/`
`https://HOSTNAME/_registry/npm/`	`https://npm.HOSTNAME/`
`https://HOSTNAME/_registry/rubygems/`	`https://rubygems.HOSTNAME/`
`https://HOSTNAME/_registry/maven/`	`https://maven.HOSTNAME/`
`https://HOSTNAME/_registry/nuget/`	`https://nuget.HOSTNAME/`

Prerequisites

警告: Subdomain Isolation を無効化している� �合は、エンタープライズの GitHub Pages も無効化することをおすすめします。ユーザが提供するGitHub Pagesのコンテンツをその他のEnterpriseのデータから分離しておく方法はありません。詳細については、「エンタープライズで GitHub Pages を構成する」を参照してく� さい。

Before you enable subdomain isolation, you must configure your network settings for your new domain.

Specify a valid domain name as your hostname, instead of an IP address. For more information, see "Configuring a hostname."

警告: 初期セットアップ後に GitHub Enterprise Server のホスト名を変更しないでく� さい。ホスト名を変更すると、インスタンスの停止に及ぶ予想外の動作が生じます。

Set up a wildcard Domain Name System (DNS) record or individual DNS records for the subdomains listed above. We recommend creating an A record for *.HOSTNAME that points to your server's IP address so you don't have to create multiple records for each subdomain.
Get a wildcard Transport Layer Security (TLS) certificate for *.HOSTNAME with a Subject Alternative Name (SAN) for both HOSTNAME and the wildcard domain *.HOSTNAME. For example, if your hostname is github.octoinc.com, get a certificate with the Common Name value set to *.github.octoinc.com and a SAN value set to both github.octoinc.com and *.github.octoinc.com.
Enable TLS on your appliance. For more information, see "Configuring TLS."