这是一篇快速指南，使用 OpenSSL 来生成 CA （证书授权中心（certificate authority））、中级 CA（intermediate CA） 和末端证书（end certificate）。包括 OCSP、CRL 和 CA颁发者（Issuer）信息、具体颁发和失效日期。
我们将设置我们自己的根 CA（root CA），然后使用根 CA 生成一个示例的中级 CA，并使用中级 CA 签发最终用户证书。
根 CA
为根 CA 创建一个目录，并进入：
mkdir -p ~/SSLCA/root/ cd ~/SSLCA/root/
生成根 CA 的 8192 位长的 RSA 密钥：
openssl genrsa -out rootca.key 8192
输出类似如下：
Generating RSA private key, 8192 bit long modulus .........++ ....................................................................................................................++ e is 65537 (0x10001)
假如你要用密码保护这个密钥，在命令行添加选项 -aes256。
创建 SHA-256 自签名的根 CA 证书 ca.crt；你需要为你的根 CA 提供识别信息：
openssl req -sha256 -new -x509 -days 1826 -key rootca.key -out rootca.crt
输出类似如下：
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]:Beijing Locality Name (eg, city) []:Chaoyang dist. Organization Name (eg, company) [Internet Widgits Pty Ltd]:Linux.CN Organizational Unit Name (eg, section) []:Linux.CN CA Common Name (e.g. server FQDN or YOUR name) []:Linux.CN Root CA Email Address []:ca@linux.cn
创建几个文件， 用于该 CA 存储其序列号：
touch certindex echo 1000 > certserial echo 1000 > crlnumber
创建 CA 的配置文件，该文件包含 CRL 和 OCSP 终端的存根。
# vim ca.conf [ ca ] default_ca = myca [ crl_ext ] issuerAltName=issuer:copy authorityKeyIdentifier=keyid:always [ myca ] dir = ./ new_certs_dir = $dir unique_subject = no certificate = $dir/rootca.crt database = $dir/certindex private_key = $dir/rootca.key serial = $dir/certserial default_days = 730 default_md = sha1 policy = myca_policy x509_extensions = myca_extensions crlnumber = $dir/crlnumber default_crl_days = 730 [ myca_policy ] commonName = supplied stateOrProvinceName = supplied countryName = optional emailAddress = optional organizationName = supplied organizationalUnitName = optional [ myca_extensions ] basicConstraints = critical,CA:TRUE keyUsage = critical,any subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always,issuer keyUsage = digitalSignature,keyEncipherment,cRLSign,keyCertSign extendedKeyUsage = serverAuth crlDistributionPoints = @crl_section subjectAltName = @alt_names authorityInfoAccess = @ocsp_section [ v3_ca ] basicConstraints = critical,CA:TRUE,pathlen:0 keyUsage = critical,any subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always,issuer keyUsage = digitalSignature,keyEncipherment,cRLSign,keyCertSign extendedKeyUsage = serverAuth crlDistributionPoints = @crl_section subjectAltName = @alt_names authorityInfoAccess = @ocsp_section [ alt_names ] DNS.0 = Linux.CN Root CA DNS.1 = Linux.CN CA Root [crl_section] URI.0 = http://pki.linux.cn/rootca.crl URI.1 = http://pki2.linux.cn/rootca.crl [ ocsp_section ] caIssuers;URI.0 = http://pki.linux.cn/rootca.crt caIssuers;URI.1 = http://pki2.linux.cn/rootca.crt OCSP;URI.0 = http://pki.linux.cn/ocsp/ OCSP;URI.1 = http://pki2.linux.cn/ocsp/
假如你要设置一个特定的证书起止时间，添加下述内容到 [myca]。
# format: YYYYMMDDHHMMSS default_enddate = 20191222035911 default_startdate = 20181222035911
创建1号中级 CA
生成中级 CA 的私钥
openssl genrsa -out intermediate1.key 4096
生成其 CSR：
openssl req -new -sha256 -key intermediate1.key -out intermediate1.csr
输出类似如下：
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]:Beijing Locality Name (eg, city) []:Chaoyang dist. Organization Name (eg, company) [Internet Widgits Pty Ltd]:Linux.CN Organizational Unit Name (eg, section) []:Linux.CN CA Common Name (e.g. server FQDN or YOUR name) []:Linux.CN Intermediate CA Email Address []: Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []:
请确保中级 CA 的主题名（CN，Common Name）和根 CA 的不同。
使用根 CA 为你创建的中级 CA 的 CSR 签名：
openssl ca -batch -config ca.conf -notext -in intermediate1.csr -out intermediate1.crt
输出类似如下：
Using configuration from ca.conf Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows countryNameRINTABLE:'CN' stateOrProvinceName :ASN.1 12:'Beijing' localityName :ASN.1 12:'chaoyang dist.' organizationName :ASN.1 12:'Linux.CN' organizationalUnitName:ASN.1 12:'Linux.CN CA' commonName :ASN.1 12:'Linux.CN Intermediate CA' Certificate is to be certified until Mar 30 15:07:43 2017 GMT (730 days) Write out database with 1 new entries Data Base Updated
生成 CRL （包括 PEM 和 DER 两种格式）：
openssl ca -config ca.conf -gencrl -keyfile rootca.key -cert rootca.crt -out rootca.crl.pem openssl crl -inform PEM -in rootca.crl.pem -outform DER -out rootca.crl
每次使用该 CA 签名证书后都需要生成 CRL。
假如需要的话，你可以撤销（revoke）这个中级证书：
openssl ca -config ca.conf -revoke intermediate1.crt -keyfile rootca.key -cert rootca.crt
配置1号中级 CA
给该中级 CA 创建新目录，并进入：
mkdir ~/SSLCA/intermediate1/ cd ~/SSLCA/intermediate1/
从根 CA 那边复制这个中级 CA 的证书和私钥：
cp ../root/intermediate1.key ./ cp ../root/intermediate1.crt ./
创建索引文件：
touch certindex echo 1000 > certserial echo 1000 > crlnumber
创建一个新的 ca.conf ：
# vim ca.conf [ ca ] default_ca = myca [ crl_ext ] issuerAltName=issuer:copy authorityKeyIdentifier=keyid:always [ myca ] dir = ./ new_certs_dir = $dir unique_subject = no certificate = $dir/intermediate1.crt database = $dir/certindex private_key = $dir/intermediate1.key serial = $dir/certserial default_days = 365 default_md = sha1 policy = myca_policy x509_extensions = myca_extensions crlnumber = $dir/crlnumber default_crl_days = 365 [ myca_policy ] commonName = supplied stateOrProvinceName = supplied countryName = optional emailAddress = optional organizationName = supplied organizationalUnitName = optional [ myca_extensions ] basicConstraints = critical,CA:FALSE keyUsage = critical,any subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always,issuer keyUsage = digitalSignature,keyEncipherment extendedKeyUsage = serverAuth crlDistributionPoints = @crl_section subjectAltName = @alt_names authorityInfoAccess = @ocsp_section [ alt_names ] DNS.0 = Linux.CN Intermidiate CA 1 DNS.1 = Linux.CN CA Intermidiate 1 [ crl_section ] URI.0 = http://pki.linux.cn/intermediate1.crl URI.1 = http://pki2.linux.cn/intermediate1.crl [ ocsp_section ] caIssuers;URI.0 = http://pki.linux.cn/intermediate1.crt caIssuers;URI.1 = http://pki2.linux.cn/intermediate1.crt OCSP;URI.0 = http://pki.linux.cn/ocsp/ OCSP;URI.1 = http://pki2.linux.cn/ocsp/
修改 [alt_names] 小节为你所需的替代主题名（Subject Alternative names）。假如不需要就删除引入它的 subjectAltName = @alt_names 行。
假如你需要指定起止时间，添加如下行到 [myca] 中。
# format: YYYYMMDDHHMMSS default_enddate = 20191222035911 default_startdate = 20181222035911
生成一个空的 CRL （包括 PEM 和 DER 两种格式）：
openssl ca -config ca.conf -gencrl -keyfile intermediate1.key -cert intermediate1.crt -out intermediate1.crl.pem openssl crl -inform PEM -in intermediate1.crl.pem -outform DER -out intermediate1.crl
创建最终用户证书
我们使用新的中级 CA 来生成最终用户的证书。为每个你需要用此 CA 签名的最终用户证书重复这些步骤。
mkdir ~/enduser-certs cd ~/enduser-certs
生成最终用户的私钥：
openssl genrsa -out enduser-example.com.key 4096
生成最终用户的 CSR：
openssl req -new -sha256 -key enduser-example.com.key -out enduser-example.com.csr
输出类似如下：
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]:Shanghai Locality Name (eg, city) []:Xuhui dist. Organization Name (eg, company) [Internet Widgits Pty Ltd]:Example Inc Organizational Unit Name (eg, section) []:IT Dept Common Name (e.g. server FQDN or YOUR name) []:example.com Email Address []: Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []:
用1号中级 CA 签名最终用户的证书：
cd ~/SSLCA/intermediate1 openssl ca -batch -config ca.conf -notext -in ~/enduser-certs/enduser-example.com.csr -out ~/enduser-certs/enduser-example.com.crt
输出类似如下：
Using configuration from ca.conf Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows countryName
生成 CRL （包括 PEM 和 DER 两种格式）：
cd ~/SSLCA/intermediate1/ openssl ca -config ca.conf -gencrl -keyfile intermediate1.key -cert intermediate1.crt -out intermediate1.crl.pem openssl crl -inform PEM -in intermediate1.crl.pem -outform DER -out intermediate1.crl
每次使用该 CA 签名证书后都需要生成 CRL。
假如需要的话，你可以撤销revoke这个最终用户证书：
cd ~/SSLCA/intermediate1/ openssl ca -config ca.conf -revoke ~/enduser-certs/enduser-example.com.crt -keyfile intermediate1.key -cert intermediate1.crt
输出类似如下：
Using configuration from ca.conf Revoking Certificate 1000. Data Base Updated
将根证书和中级证书连接起来创建证书链文件：
cat ../root/rootca.crt intermediate1.crt > ~/enduser-certs/enduser-example.com.chain
将这些文件发送给最终用户：
enduser-example.com.crt enduser-example.com.key enduser-example.com.chain
你也可以让最终用户提供他们中级的 CSR 文件，而只发回给他们 这个 .crt 文件。不要从服务器上删除它们，否则就不能撤销了。
校验证书
你可以通过如下命令使用证书链来验证最终用户证书：
cd ~/enduser-certs openssl verify -CAfile enduser-example.com.chain enduser-example.com.crt enduser-example.com.crt: OK
你也可以用 CRL 来校验它。首先将 PEM CRL 连接到证书链文件：
cd ~/SSLCA/intermediate1 cat ../root/rootca.crt intermediate1.crt intermediate1.crl.pem > ~/enduser-certs/enduser-example.com.crl.chain
校验证书：
cd ~/enduser-certs openssl verify -crl_check -CAfile enduser-example.com.crl.chain enduser-example.com.crt
假如该证书未撤销，输出如下：
enduser-example.com.crt: OK
假如撤销了，输出如下：
enduser-example.com.crt: CN = example.com, ST = Beijing, C = CN, O = Example Inc, OU = IT Dept error 23 at 0 depth lookup:certificate revoked