通过 acme.sh 获取 Let's Encrypt 免费证书

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配置 Nginx 正确处理 Webroot 验证

在证书签发过程中 Let's Encrypt 会验证你拥有当前域名，最基本的方式在你的网站根目录创建一个文件，并通过域名在外部进行请求，如能请求到则认为你拥有该网站的控制权。假设你有一个域名 example.com， 验证步骤大体如下：

  1. 通过工具在网站根目录下创建 .well-known/acme-challenge/some-random-letters
  2. 工具将创建的路径告知 Let's Encrypt
  3. Let's Encrypt 通过域名请求该文件，如 http://example.com/.well-known/acme-challenge/some-random-letters
  4. 若能请求到则确认拥有该网站的控制权颁发证书，否则拒绝颁发

为了简化多个域名颁发证书需指定不同的 Webroot，我们可以将所有域名的验证统一放在一个目录下，并新增一个配置片段供需要启用 HTTPS 的网站引用，新增 /etc/nginx/snippets/letsencrypt-acme-challenge.conf ，并填充如下内容

#############################################################################
# Configuration file for Let's Encrypt ACME Challenge location
#############################################################################
#
# This config enables to access /.well-known/acme-challenge/xxxxxxxxxxx
# on all our sites (HTTP), including all subdomains.
# This is required by ACME Challenge (webroot authentication).
# You can check that this location is working by placing ping.txt here:
# /var/www/letsencrypt/.well-known/acme-challenge/ping.txt
# And pointing your browser to:
# http://xxx.domain.tld/.well-known/acme-challenge/ping.txt
#
# Sources:
# https://community.letsencrypt.org/t/howto-easy-cert-generation-and-renewal-with-nginx/3491
#
#############################################################################

# Rule for legitimate ACME Challenge requests (like /.well-known/acme-challenge/xxxxxxxxx)
# We use ^~ here, so that we don't check other regexes (for speed-up). We actually MUST cancel
# other regex checks, because in our other config files have regex rule that denies access to files with dotted names.
location ^~ /.well-known/acme-challenge/ {

    # Set correct content type. According to this:
    # https://community.letsencrypt.org/t/using-the-webroot-domain-verification-method/1445/29
    # Current specification requires "text/plain" or no content header at all.
    # It seems that "text/plain" is a safe option.
    default_type "text/plain";

    # This directory must be the same as in /etc/letsencrypt/cli.ini
    # as "webroot-path" parameter. Also don't forget to set "authenticator" parameter
    # there to "webroot".
    # Do NOT use alias, use root! Target directory is located here:
    # /var/www/common/letsencrypt/.well-known/acme-challenge/
    root         /var/www/letsencrypt;
}

# Hide /acme-challenge subdirectory and return 404 on all requests.
# It is somewhat more secure than letting Nginx return 403.
# Ending slash is important!
location = /.well-known/acme-challenge/ {
    return 404;
}

在需要启用验证的网站的 Nginx 配置中增加如下内容即可

server {
   ...

   include /etc/nginx/snippets/letsencrypt-acme-challenge.conf;
}

创建相应目录重启 Nginx

sudo mkdir -p /var/www/letsencrypt/
sudo chown $(whoami).$(whoami) /var/www/letsencrypt/
sudo /etc/init.d/nginx configtest && sudo /etc/init.d/nginx reload

获取证书

  1. 安装 acme.sh

    curl https://get.acme.sh | sh

  2. 获取证书

    acme.sh --issue -d example.com -d www.example.com -w /var/www/letsencrypt

安装证书

获取的证书因为在用户家目录下，所以不能直接使用，需要通过如下命令安装到系统中

sudo mkdir -p /etc/nginx/certs/example.com
sudo chown root.$(whoami) /etc/nginx/certs/example.com
sudo chmod g+w /etc/nginx/certs/example.com
acme.sh --install-cert -d example.com \
    --cert-file /etc/nginx/certs/example.com/cert.pem \
    --key-file /etc/nginx/certs/example.com/key.pem \
    --fullchain-file /etc/nginx/certs/example.com/fullchain.pem \
    --reloadcmd "service nginx reload"

安装后可以配置 Nginx 启用 HTTPS

server {
  listen  80;
  server_name     www.example.com;
  server_name     example.com;
  return         301 https://$server_name$request_uri;
}

server{
        listen 443 ssl;
        server_name     www.example.com;
        server_name     example.com;

        ssl_certificate /etc/nginx/certs/example.com/fullchain.pem;
        ssl_certificate_key /etc/nginx/certs/example.com/key.pem;
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_dhparam /etc/ssl/certs/dhparam.pem;
        ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:AES:CAMELLIA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA';
        ssl_session_timeout 1d;
        ssl_session_cache shared:SSL:50m;
        ssl_stapling on;
        ssl_stapling_verify on;
        add_header Strict-Transport-Security max-age=15768000;

        access_log      /var/log/nginx/www.example.com.log;

        location / {
                root    /var/www/html;
                index   index.html index.htm;
        }

        include /etc/nginx/snippets/letsencrypt-acme-challenge.conf;
}
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