通过 acme.sh 获取 Let's Encrypt 免费证书

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