Let’s Encrypt从2018年开始支持泛域名证书，有效期3个月，目前仅支持acme方式申请，暂不支持certbot。
1、安装acme.sh
curl https://get.acme.sh | sh
2、请求证书（泛域名以*.s-b.me为例）
cd /.acme.sh
./acme.sh --issue -d *.s-b.me -d s-b.me --dns --yes-I-know-dns-manual-mode-enough-go-ahead-please
输出：
[Sat Mar 24 13:10:07 UTC 2018] Registering account
[Sat Mar 24 13:10:08 UTC 2018] Registered
[Sat Mar 24 13:10:08 UTC 2018] ACCOUNT_THUMBPRINT='hS_gwvXaqMtxJh2Bz0asmWK3r7iMYIknkOWDqO1a76U'
[Sat Mar 24 13:10:08 UTC 2018] Creating domain key
[Sat Mar 24 13:10:09 UTC 2018] The domain key is here: /root/.acme.sh/*.s-b.me/*.s-b.me.key
[Sat Mar 24 13:10:09 UTC 2018] Multi domain='DNS:*.s-b.me,DNS:s-b.me'
[Sat Mar 24 13:10:09 UTC 2018] Getting domain auth token for each domain
[Sat Mar 24 13:10:10 UTC 2018] Getting webroot for domain='*.s-b.me'
[Sat Mar 24 13:10:10 UTC 2018] Getting webroot for domain='s-b.me'
[Sat Mar 24 13:10:10 UTC 2018] Add the following TXT record:
[Sat Mar 24 13:10:10 UTC 2018] Domain: '_acme-challenge.s-b.me'
[Sat Mar 24 13:10:10 UTC 2018] TXT value: '6sf1Iuh7r****************bHPs8QriJf8ibpszRk'
[Sat Mar 24 13:10:10 UTC 2018] Please be aware that you prepend _acme-challenge. before your domain
[Sat Mar 24 13:10:10 UTC 2018] so the resulting subdomain will be: _acme-challenge.s-b.me
[Sat Mar 24 13:10:10 UTC 2018] Add the following TXT record:
[Sat Mar 24 13:10:10 UTC 2018] Domain: '_acme-challenge.s-b.me'
[Sat Mar 24 13:10:10 UTC 2018] TXT value: 'iA68V9A14****************mlrsZx24raM-S0gmpI'
[Sat Mar 24 13:10:10 UTC 2018] Please be aware that you prepend _acme-challenge. before your domain
[Sat Mar 24 13:10:10 UTC 2018] so the resulting subdomain will be: _acme-challenge.s-b.me
[Sat Mar 24 13:10:10 UTC 2018] Please add the TXT records to the domains, and re-run with --renew.
[Sat Mar 24 13:10:10 UTC 2018] Please add '--debug' or '--log' to check more details.
[Sat Mar 24 13:10:10 UTC 2018] See: https://github.com/Neilpang/acme.sh/wiki/How-to-debug-acme.sh
3、参考输出，添加域名txt记录，以验证域名所有权
_acme-challenge.s-b.me txt iA68V9A14****************mlrsZx24raM-S0gmpI
_acme-challenge.s-b.me txt 6sf1Iuh7r****************bHPs8QriJf8ibpszRk
4、申请泛解析证书
./acme.sh --renew -d *.s-b.me -d s-b.me --dns --yes-I-know-dns-manual-mode-enough-go-ahead-please
如果顺利，会在当前目录下生成以泛域名为名字的证书目录
/root/.acme.sh
*.s-b.me/
├── ca.cer
├── fullchain.cer
├── *.s-b.me.cer
├── *.s-b.me.conf
├── *.s-b.me.csr
├── *.s-b.me.csr.conf
└── *.s-b.me.key
5、配置nginx或其他web server以支持SSL访问
.cer 是证书文件
.key 是私钥文件
fullchain.cer 是证书链证书
6、证书续期
通过crontab或者其他定时任务系统执行
./acme.sh --renew -d *.s-b.me -d s-b.me --dns --yes-I-know-dns-manual-mode-enough-go-ahead-please
【参考】
https://github.com/Neilpang/acme.sh
https://keelii.github.io/2016/06/12/free-https-cert-lets-encrypt-apply-install/