Let's Encryptよりワイルドカードなサーバ証明書を取得する

## 1. GithubよりLet's EncryptリポジトリをCloneする
```
# git clone https://github.com/letsencrypt/letsencrypt.git
```

## 2. 以下のコマンドを実行する
```
# cd letsencrypt
# ./letsencrypt-auto certonly --manual -d *.<ドメイン名> --preferred-challenges dns
```
- ```<ドメイン名>```は、``` * ```以下のドメインを入力する。

## 3. 画面の指示に従い、操作を行う
### メールアドレスの登録
メールアドレスを入力して、[Enter]を押下します。

```
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None
Enter email address (used for urgent renewal and security notices) (Enter 'c' to
cancel): <メールアドレス>
```

### 規約、メールアドレスの収集、IPアドレスの収集に関する同意
``` a ``` を入力し、[Enter]を押下して進めます。

```
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Please read the Terms of Service at
https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf. You must
agree in order to register with the ACME server at
https://acme-v02.api.letsencrypt.org/directory
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
(A)gree/(C)ancel: A
```

### 規約、メールアドレスの収集、IPアドレスの収集に関する同意
全て``` y ``` を入力し、[Enter]を押下して進めます。

```
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Would you be willing to share your email address with the Electronic Frontier
Foundation, a founding partner of the Let's Encrypt project and the non-profit
organization that develops Certbot? We'd like to send you email about our work
encrypting the web, EFF news, campaigns, and ways to support digital freedom.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
(Y)es/(N)o: y
Obtaining a new certificate
Performing the following challenges:
dns-01 challenge for <ドメイン名>

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
NOTE: The IP of this machine will be publicly logged as having requested this
certificate. If you're running certbot in manual mode on a machine that is not
your server, please ensure you're okay with that.

Are you OK with your IP being logged?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
(Y)es/(N)o: y
```

## 4. DNS TXTレコードの登録
以下のようなメッセージが表示され、DNS TXTレコードのエントリとして指定された値の入力（登録）を求められますので、DNSサーバに対して登録を行います。

```
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Please deploy a DNS TXT record under the name
_acme-challenge.<ドメイン名> with the following value:

<TXTレコードへ入力する値>

Before continuing, verify the record is deployed.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
```

DNSサーバへの登録後、しばらく（5分程度）時間をおいてから[Enter]を押下します。

## 5. 登録完了
次のようなメッセージが表示され、サーバ証明書が発行されます。

```
Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<ドメイン名>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<ドメイン名>/privkey.pem
   Your cert will expire on <有効期限>. To obtain a new or tweaked
   version of this certificate in the future, simply run
   letsencrypt-auto again. To non-interactively renew *all* of your
   certificates, run "letsencrypt-auto renew"
 - Your account credentials have been saved in your Certbot
   configuration directory at /etc/letsencrypt. You should make a
   secure backup of this folder now. This configuration directory will
   also contain certificates and private keys obtained by Certbot so
   making regular backups of this folder is ideal.
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le
```

上記に表示されたディレクトリを確認すると、証明書ファイルを確認することが出来ます。

```
# cd /etc/letsencrypt/live/<ドメイン名>/
# ls -la
total 12
drwxr-xr-x 2 root root 4096 Nov  1 08:39 .
drwx------ 3 root root 4096 Nov  1 08:39 ..
-rw-r--r-- 1 root root  682 Nov  1 08:39 README
lrwxrwxrwx 1 root root   52 Nov  1 08:39 cert.pem -> ../../archive/<ドメイン名>/cert1.pem
lrwxrwxrwx 1 root root   53 Nov  1 08:39 chain.pem -> ../../archive/<ドメイン名>/chain1.pem
lrwxrwxrwx 1 root root   57 Nov  1 08:39 fullchain.pem -> ../../archive/<ドメイン名>/fullchain1.pem
lrwxrwxrwx 1 root root   55 Nov  1 08:39 privkey.pem -> ../../archive/<ドメイン名>/privkey1.pem
```