资料：
如何使用 OpenSSL 建立開發測試用途的自簽憑證 (Self-Signed Certificate)
Create a self-signed certificate using OpenSSL
OpenSSL Certification Authority (CA) on Ubuntu Server
Create your own Certificate Authority
现在生产环境最次其实也应该有个 Let‘s Encrypt，而且能够被浏览器信任，自签证书除了测试环境其实没啥用（
实验
本例我们需要自己扮演一个根证书颁发机构 ( CA )，来自己给自己签发一个根证书，并用这个根证书为其他证书签名。
这个实验需要使用 OpenSSL 来签发证书。
这个实验需要几个步骤，分别为:
在生产环境中，要签发实际使用的证书通常在我们的本机上生成私钥，来确保加密传输的安全性，但实验中，我们完全可以把所有环节均在 CA 服务器上完成，这样可以省下许多把文件传来传去的时间。
根证书的签发
签发根证书前，先做一些配置。
修改 /usr/lib/ssl/openssl.cnf，在 48 行，[CA_default] 中，修改 dir 为存放 CA 需要文件的根目录，本例为 /CA
修改后，创建两个文件
# 用于定位根目录位置
$ touch /CA/index.txt
# 一个初始数字用于代表签发证书的数量，每签发一张证书，数字便会 +1
$ echo 1000 > /CA/serial
创建好目录结构
cd /CA
mkdir newcerts private certs
接下来切换到 CA 的根目录，开始生成 CA 根证书
$ cd /CA
# 根证书的私钥，即 key 文件，长度为 4096 bit
$ openssl genrsa -out cakey.pem 4096
$ mv cakey.pem ./private/
# 用刚才生成的私钥签发证书
$ openssl req -new -x509 -key ./private/cakey.pem -out ./cacert.pem
# 根据需求输入证书信息
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.
-----
Country Name (2 letter code) [AU]:CN
State or Province Name (full name) [Some-State]:Liaoning
Locality Name (eg, city) []:Dandong
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Inc
Organizational Unit Name (eg, section) []:
Common Name (e.g. server FQDN or YOUR name) []:Skill Global Root CA
Email Address []:
生成的 cacert.pem 即为根证书，需要将其导入所有主机的信任列表
其他证书的签发
签发其他证书时，依然需要生成私钥，但第二步需要生成证书签发请求，然后使用 CA 根证书签名
# 生成一个私钥
$ openssl genrsa -out server01key.pem 4096
# 使用私钥生成一个证书签发请求
$ openssl req -new -key server01key.pem -out server01.csr
ou 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.
-----
Country Name (2 letter code) [AU]:CN
State or Province Name (full name) [Some-State]:Liaoning
Locality Name (eg, city) []:Dandong
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Inc
Organizational Unit Name (eg, section) []:
Common Name (e.g. server FQDN or YOUR name) []:server01.sdskills.com
Email Address []:
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
# 用根证书与私钥签发证书
$ openssl ca -in server01.csr -out server01.pem
Using configuration from /usr/lib/ssl/openssl.cnf
Check that the request matches the signature
Signature ok
Certificate Details:
Serial Number: 4096 (0x1000)
Validity
Not Before: Mar 28 14:36:39 2021 GMT
Not After : Mar 28 14:36:39 2022 GMT
Subject:
countryName = CN
stateOrProvinceName = Liaoning
organizationName = Inc
commonName = server01.sdskills.com
X509v3 extensions:
X509v3 Basic Constraints:
CA:FALSE
Netscape Comment:
OpenSSL Generated Certificate
X509v3 Subject Key Identifier:
29:55:53:D7:48:A6:93:6A:56:9C:E5:38:C3:92:6A:2F:3C:AC:B7:06
X509v3 Authority Key Identifier:
keyid:18:D9:48:2B:0E:D2:F4:FF:0C:0D:67:E8:CB:26:4C:30:CE:F2:6D:60
Certificate is to be certified until Mar 28 14:36:39 2022 GMT (365 days)
Sign the certificate? [y/n]:y
1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated
连敲两个 y 即可
生成的 server01.pem 即为证书
在配置证书时，需要生成的客户机自己的私钥，与经过根证书签名的证书，根证书自己的私钥需在 CA 服务器上自己保存好。
之后要签发证书，按照生成私钥 -> 生成签发请求 -> 在 CA 上签名 这三步即可。
由于总是要传一些签发好的证书，所以建议这时先不要阻挡 CA 服务器的 SSH 访问，能大大加快实际做题的速度
指用 SCP 传文件