这两天在检查一台 Nginx 配置的时候，遇到了一个极端诡异的问题。一段很通用的配置，配在这个服务器上，就会 100% 导致 Chrome 报 ERR_SSL_PROTOCOL_ERROR 。但是这段配置非常的通用，是用 Mozilla 提供的工具生成的。

而且在 iPhone 的 Safari 上访问又是完全正常的，服务器日志也看不到任何错误。看到的请求相应码也是完全正确的 200 。

先贴出配置：

# https://mozilla.github.io/server-side-tls/ssl-config-generator/
    listen 443 ssl http2;

    # certs sent to the client in SERVER HELLO are concatenated in ssl_certificate
    ssl_certificate /path/to/signed_cert_plus_intermediates;
    ssl_certificate_key /path/to/private_key;
    ssl_session_timeout 1d;
    ssl_session_cache shared:SSL:50m;
    ssl_session_tickets off;


    # modern configuration. tweak to your needs.
    ssl_protocols TLSv1.2;
    ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256';
    ssl_prefer_server_ciphers on;

可以看到是在 Mozilla 网站上选择 Nginx 和 Modern 生成出来的配置。

在测试过程中，排查了各种问题，包括但不限于 SSL 证书问题，HTTP Basic Auth 问题，http2 问题等等，然而都没有解决这个现象。

一次偶然的尝试，发现只要注释掉我给这个 server 特殊配置的这段逻辑，使用服务器通用的 ssl.ngx 文件中的 SSL 配置，就不会出现问题。于是开始先使用 ssl.ngx 文件中的配置，然后逐行替换，来查找具体出现问题的配置。

终于，当我将配置中的这行加上时，问题出现了：

ssl_session_tickets off;

于是以这个配置作为关键字搜索，找到了这么一篇文章：

https://community.letsencrypt.org/t/errors-from-browsers-with-ssl-session-tickets-off-nginx/18124/5

I’m posting this here both because this question was recently asked and because it took me many hours of troubleshooting to figure out the issue as while I found several references to the problem on Google, no one seemed to have a real solution. So here it is:

ssl_session_tokens off breaks if it’s not set the same for all ssl-enabled server{} blocks. So if you have 2 server configurations and and you have ssl_server_tokens set to on in one (which is the default so it counts even if you omit it) and set to off in another, it will break the one where it’s set to off in certain browsers. The easiest way to resolve this, unless you have multiple http{} blocks, is to just set it to off in the http{} block. I have not tested to see if you you can have different settings in different http{} blocks as I haven’t had need to set up more than one http{} block.

For others looking for this issue, I want to add that Chrome will respond with: ERR_SSL_PROTOCOL_ERROR while Firefox responds with: SSL_ERROR_RX_UNEXPECTED_NEW_SESSION_TICKET and curl responds with: gnutls_handshake() failed: An unexpected TLS packet was received. IE seemed to work, surprisingly.

简单翻译一下，这里是说，如果你的 nginx 开了多个 https 的 server，其中某些 server 没有配置 ssl_server_tokens off; ，而有些 server 配置了这个选项，那么就会导致没有手动 off 的 server 采用默认值 on，而手动 off 掉的 server 采用 off。这种情况会导致 nginx 和浏览器之间的握手出现问题，从而导致 Chrome 报出 ERR_SSL_PROTOCOL_ERROR ，FireFox 则会报出 SSL_ERROR_RX_UNEXPECTED_NEW_SESSION_TICKET 。

那么解决方法也很简单，只要在所有的 server 块统一这个配置就好了。要么都设置为 on，要么都设置为 off，问题解决。目前没有尝试多个 http 块隔离两个 server，建议还是将这个配置统一一下。