参考：如何利用中继证书（凭证）建立客户端证书
地址：https://qingmu.blog.csdn.net/article/details/108226592?spm=1001.2014.3001.5502
自建根证书详解
中继证书建立详解
并且需要安装openssl库：
sudo apt-get install openssl
本实验是在根证书和中继证书的前提下完成的，可参考根证书的建立和中继证书的建立
输入命令（注意路径哦）：
mkdir client
cd client
文件名：openssl_csr.cnf
路径：client目录下
具体内容：
[ req ]
# req 工具需要的參數.
default_bits = 2048
distinguished_name = req_distinguished_name
string_mask = utf8only
default_md = sha256
[ req_distinguished_name ]
# 产生证书时要输入的资料说明.
countryName = Country Name (2 letter code)
stateOrProvinceName = State or Province Name
localityName = Locality Name
0.organizationName = Organization Name
organizationalUnitName = Organizational Unit Name
commonName = Common Name
emailAddress = Email Address
文件名：client.key.pem
路径：client目录下
输入命令：
openssl genrsa -aes256 -out client.key.pem 4096
会提示输入私钥的密码, 例如是 helen123
Enter pass phrase for server.key.pem:helen123
再次输入密码：
Verifying - Enter pass phrase for server.key.pem:helen123
更改私钥的权限为只读：
chmod 400 client.key.pem
输入命令：
openssl req -config openssl_csr.cnf -new -sha256 -key client.key.pem -out client.csr.pem
会提示输入服务器证书的私钥的密码, 也就是 helen123
Enter pass phrase for server.key.pem:helen123
# 接着输入证书拥有者的信息
You are about to be asked to enter information that will be incorporated into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank For some fields there will be a default value,
If you enter '.', the field will be left blank.
# 所在国家的缩写, 2 个字母
Country Name (2 letter code) []:AU
# 所在的州或省.
State or Province Name []:New South Wales
# 所在的城市.
Locality Name []:Sydney
# 所在的公司.
Organization Name []:Helen
# 所在的公司的单位.
Organizational Unit Name []:Helen
# 证书名称
Common Name []:helen@personal
# 邮箱
Email Address []:helen@personal
在中继证书目录下操作.
cd ../intermediate
签发凭证签发申请档, 有效期限是 3650 天.
输入命令：
openssl ca -config openssl_intermediate_ca.cnf -extensions client_cert -days 365 -notext -md sha256 -in ../client/client.csr.pem -out ../client/client.cert.pem
# 会提示需要输入根凭证的私钥密码, 也就是 bob123
Enter pass phrase for /ca/intermediate/private/intermediate_ca.key.pem:bob123
# 接著会显示要签发的凭证签发申请档的内容.
Check that the request matches the signature
Signature ok
Certificate Details:
...
# 并询问是否签发, 输入 y
Sign the certificate? [y/n]:y
# 以及询问是否纪录签发的凭证到资料库 (index.txt, serial), 输入 y
1 out of 1 certificate requests certified, commit? [y/n]y
变更签发的凭证的存取权限为只读
输入命令：
chmod 444 ../client/client.cert.pem
输入命令：
openssl x509 -noout -text -in ../client/client.cert.pem
# 使用的算法
Signature Algorithm: sha256WithRSAEncryption
# 公钥的长度
Subject Public Key Info:
Public-Key: (4096 bit)
# 有效日期.
Validity:
Not Before: Aug 4 23:59:15 2017 GMT
Not After : Aug 4 23:59:15 2018 GMT
# 主旨 (Helen 的资料).
Subject: C=AU, ST=New South Wales, O=Helen, OU=Helen,CN=helen@personal/emailAddress=helen@local
# 签发者 (Bob 的资料).
Issuer: C=US, ST=California, O=Bob Ltd, OU=Bob Ltd Certificate Authority, CN=Bob Ltd Intermediate CA/emailAddress=bob@local
输入命令：
openssl verify -CAfile chain/chain.cert.pem ../client/client.cert.pem
显示 OK 表示正确.
…/client/client.cert.pem: OK
回到客户端证书目录里
cd ../client
产生证书串链：
cat client.cert.pem ../intermediate/chain/chain.cert.pem > client_chain.cert.pem
变更串链的读取权限为只读：
chmod 444 client_chain.cert.pem
