Sweet32漏洞，升级openssl或者禁用3DES和DES弱加密算法
问题
由于等保的原因，被服务商扫描出漏洞。
warnings:
| 64-bit block cipher 3DES vulnerable to SWEET32 attack
漏洞复现
$ nmap -sV --script ssl-enum-ciphers -p 443 xx.xxxxbac.com
Starting Nmap 7.80 ( https://nmap.org ) at 2022-09-27 10:54 CST
Nmap scan report for xx.xxxxbac.com (120.77.xx.xx)
Host is up (0.0090s latency).
PORT STATE SERVICE VERSION
443/tcp open ssl/http nginx
| ssl-enum-ciphers:
| TLSv1.1:
| ciphers:
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (ecdh_x25519) - A
| TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (ecdh_x25519) - A
| TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
| TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA (ecdh_x25519) - C
| TLS_RSA_WITH_3DES_EDE_CBC_SHA (rsa 2048) - C
| compressors:
| NULL
| cipher preference: server
| warnings:
| 64-bit block cipher 3DES vulnerable to SWEET32 attack
| TLSv1.2:
| ciphers:
| TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 (ecdh_x25519) - A
| TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (ecdh_x25519) - A
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (ecdh_x25519) - A
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (ecdh_x25519) - A
| TLS_RSA_WITH_AES_128_GCM_SHA256 (rsa 2048) - A
| TLS_RSA_WITH_AES_128_CCM_8 (rsa 2048) - A
| TLS_RSA_WITH_AES_128_CCM (rsa 2048) - A
| TLS_RSA_WITH_AES_128_CBC_SHA256 (rsa 2048) - A
| TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
| TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (ecdh_x25519) - A
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (ecdh_x25519) - A
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (ecdh_x25519) - A
| TLS_RSA_WITH_AES_256_GCM_SHA384 (rsa 2048) - A
| TLS_RSA_WITH_AES_256_CCM_8 (rsa 2048) - A
| TLS_RSA_WITH_AES_256_CCM (rsa 2048) - A
| TLS_RSA_WITH_AES_256_CBC_SHA256 (rsa 2048) - A
| TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
| TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA (ecdh_x25519) - C
| TLS_RSA_WITH_3DES_EDE_CBC_SHA (rsa 2048) - C
| compressors:
| NULL
| cipher preference: server
| warnings:
| 64-bit block cipher 3DES vulnerable to SWEET32 attack
|_ least strength: C
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 14.93 seconds
如何不喜欢使用nmap,也可以使用如下工具testssl.sh，但是输出的内容太多了，本次我只截取部分
$ docker run --rm -ti drwetter/testssl.sh xx.xxxxbac.com
###########################################################
testssl.sh 3.2rc1 from https://testssl.sh/dev/
This program is free software. Distribution and
modification under GPLv2 permitted.
USAGE w/o ANY WARRANTY. USE IT AT YOUR OWN RISK!
Please file bugs @ https://testssl.sh/bugs/
###########################################################
Secure Renegotiation (RFC 5746) supported (OK)
Secure Client-Initiated Renegotiation not vulnerable (OK)
CRIME, TLS (CVE-2012-4929) not vulnerable (OK)
BREACH (CVE-2013-3587) no gzip/deflate/compress/br HTTP compression (OK) - only supplied "/" tested
POODLE, SSL (CVE-2014-3566) not vulnerable (OK), no SSLv3 support
TLS_FALLBACK_SCSV (RFC 7507) Downgrade attack prevention supported (OK)
SWEET32 (CVE-2016-2183, CVE-2016-6329) VULNERABLE, uses 64 bit block ciphers
解决办法
解决办法有两个，一个是升级OpenSSL 1.0.2k-fips 26 Jan 2017 以上，另外一个是更新nginx配置，禁用3DES和DES弱加密算法。
第一个比较麻烦，影响面积比较广，centos7 上，大多数教程都是需要自行编译，影响线上环境。
本次介绍第二种方法，更新nginx配置禁用3DES和DES弱加密算法，然后nginx -s reload即可。
#注释下面的语句
#ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE:ECDH:AES:HIGH:!NULL:!aNULL:!MD5:!ADH:!RC4;
ssl_ciphers HIGH:!ADH:!MD5;
再次运行，将会全部提示A等级。
nmap -sV --script ssl-enum-ciphers -p 443 xx.xxxxbac.com