使用OpenSSL配置证书的SAN值

简介

本文档介绍如何在使用OpenSSL创建的证书上配置多个主题备用名称(SAN)值。

先决条件

要求

Cisco 建议您具有以下主题的基础知识：

• 安全套接字层(SSL)证书
• OpenSSL
• Linux命令
• SAN

使用的组件

本文档中的信息基于以下软件版本：

• OpenSSL版本CiscoSSL 1.1.1j.7.2sp.230
• 内部证书颁发机构(CA)

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您的网络处于活动状态，请确保您了解所有命令的潜在影响。

背景信息

在证书中使用SAN值是当今的常见做法，对于各种应用(例如远程接入VPN(RAVPN)身份验证或零信任网络接入(ZTNA)设备的SSL证书)至关重要。这些应用程序通常需要包含多个SAN值的证书，以便安全地支持不同的域名或IP地址。

默认情况下，Cisco Firepower管理中心(FMC)或其他CSR生成器等工具生成的证书签名请求(CSR)通常不包括添加多个SAN值的选项。此限制导致证书仅包含单个SAN值，不能满足现代网络环境的要求。

配置

为了克服此限制，推荐的方法是使用OpenSSL之类的工具将SAN值直接添加到CSR。这可以确保在证书颁发机构(CA)签署CSR时，生成的证书包含所需的SAN条目。此过程的关键是修改OpenSSL配置或使用指定SAN值的相应配置文件。这样，CSR明确包括SAN扩展，允许CA根据需要颁发包含多个SAN的证书。

注意：如果使用第三方或已知的CA，请在提交之前验证CA是否支持CSR中的自定义SAN值。

步骤1.创建RSA私钥

使用命令openssl genrsa -out <key_name>.key 4096。

root@host1:/home/admin/certificate# openssl genrsa -out privatekey.key 4096

步骤2.创建配置文件

此文件指定要包括在CSR中的SAN值。

1.创建名为<config_file_name>.conf的配置文件，并使用文本编辑器编辑该文件。例如，在Vim中运行<config_file_name>.conf命令（您可以使用其他文本编辑器）。

vim config.conf

2.添加此内容，在[alt_names]部分下用您的实际证书详细信息和所需的SAN条目替换占位符值：

[ req ] 
default_bits = 4096 
default_md = sha256 
prompt = no  
distinguished_name = req_distinguished_name 
req_extensions = v3_req

[ req_distinguished_name ] 
countryName = 
stateOrProvinceName = 
localityName = 
organizationName = 
organizationalUnitName = 
commonName = 

[ v3_req ] 
subjectAltName = @alt_names

[ alt_names ] 
DNS.1 = 
DNS.2 = 
DNS.3 = 
DNS.4 = 

步骤3.使用私钥和配置文件请求CSR

使用之前创建的私钥和配置文件，使用命令openssl req -new <key_name>.key -config <conf_name>.conf -out <CSR_Name>.csr创建CSR。

openssl req -new -key privatekey.key -config config.conf -out CSR.csr

注意：运行此命令时，请确保私钥和配置文件位于同一目录中。

运行命令后，<CSR_name>.csr文件将显示在文件夹中。这是必须发送到CA服务器进行签名的CSR文件。

验证

运行openssl req -text -noout -verify -in CSR.csr命令以确保SAN值在CSR中可用。

root@FTD1:/home/admin/TZSANValue# openssl req -text -noout -verify -in CSR.csr
verify OK
Certificate Request:
Data:
Version: 1 (0x0)
Subject: C = US, ST = California, L = San Francisco, O = Cisco, OU = VPN, CN = <Domain Name>
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public-Key: (4096 bit)
Modulus:
00:de:6a:85:c6:1b:33:8c:14:a4:5b:0b:f8:fb:5a:
c8:a3:2e:b6:74:63:0c:4e:ad:05:24:bd:16:ad:cc:
a3:b9:a3:3b:f4:c7:52:9d:f2:02:ff:67:49:0f:cc:
64:e2:9a:70:53:9b:68:88:f1:92:1e:09:9c:fc:34:
76:31:c4:0a:e8:ce:de:61:8f:fb:1e:02:f9:a6:57:
78:c7:86:71:e9:46:d8:70:88:c0:c6:0d:93:83:ae:
45:05:e6:b4:ca:26:39:b9:8e:42:6d:de:43:92:a7:
c4:4d:11:7c:01:4a:d5:b9:bf:b7:5e:f6:a8:2d:4a:
78:98:36:25:89:a3:52:1c:63:8a:40:f6:6f:84:b3:
8d:c7:b0:dd:29:b7:4a:e7:41:76:cc:b5:a7:87:ca:
90:9d:04:c2:cf:b8:66:8e:8c:50:5e:3d:26:75:ea:
97:bd:8c:a3:fe:77:30:52:6c:38:30:10:e8:a9:9f:
cc:ab:f8:85:fd:c8:c6:c2:88:39:42:e7:7d:41:51:
48:44:78:ae:82:dd:e6:96:cb:eb:15:13:3e:a0:e3:
86:03:b1:c3:fa:fc:5e:db:7c:79:bf:54:06:54:dc:
9c:4e:83:de:97:7a:c0:e1:18:70:ba:d8:f8:20:69:
58:52:23:4a:6f:78:e4:7f:f7:cb:b6:2f:be:59:db:
cf:d5:d5:7c:49:12:e1:9c:ef:24:83:0e:80:94:48:
01:ce:6f:ce:61:c3:a5:aa:bb:98:45:d3:f1:26:99:
02:5a:b1:84:73:8b:31:94:1d:00:4b:96:60:c6:55:
52:7c:f5:62:25:cd:17:eb:7a:1d:c3:0d:53:23:8f:
c3:ce:94:42:35:6a:13:ac:db:76:ac:fc:9d:8d:a1:
39:05:c2:1b:27:04:4f:67:bc:22:58:1d:91:b4:85:
b0:99:44:7d:e9:55:ce:ca:bd:c0:42:26:9c:f8:88:
26:d5:74:5d:43:c4:ba:9c:25:6c:0f:b9:2e:59:91:
a8:d1:01:b4:2c:63:40:46:8f:9a:e2:34:02:00:81:
39:cc:6b:3a:39:ff:c1:aa:c5:80:d1:ed:66:15:94:
a5:25:e8:2c:3a:52:b2:de:f5:03:76:26:be:9d:8f:
84:5c:f4:78:6f:f1:64:55:2a:f0:b0:1e:23:3c:b6:
65:1a:6c:ba:4a:e1:c0:cf:22:cc:cd:e8:59:ce:75:
60:14:c0:c7:dd:e0:61:34:77:a6:d6:cc:c2:5e:5e:
15:e0:37:c3:f4:ed:a3:c0:69:52:78:38:b7:b3:d7:
42:49:97:ff:23:76:80:5b:0b:cd:5e:2f:7e:30:c7:
77:91:bb:b8:52:24:ad:c5:86:8e:9b:18:e0:2e:ea:
e2:bb:83
Exponent: 65537 (0x10001)
Attributes:
Requested Extensions:
X509v3 Subject Alternative Name: 
DNS:, DNS:, DNS:, DNS:
Signature Algorithm: sha256WithRSAEncryption
60:9b:12:b8:f8:e8:07:3f:d7:e7:73:f9:4e:d4:a9:28:7f:1d:
30:44:2b:16:88:dc:d6:01:39:ee:c0:06:71:61:90:ad:b4:c3:
f0:ea:eb:bb:4f:8b:11:68:fe:3c:24:ae:a6:bc:cb:68:4a:21:
77:bb:85:37:91:a3:fa:0c:ee:ce:b1:78:5f:fc:cb:d5:c6:2a:
ae:2d:41:df:0f:3d:d4:eb:8e:83:4c:8c:10:d0:81:42:62:0c:
e6:19:e1:2e:14:ef:46:cd:32:20:64:1a:0d:32:44:57:b7:3d:
76:f3:4c:b9:61:51:a6:20:cf:6d:37:ca:b6:b3:4e:ea:36:16:
bb:a9:ec:8a:6d:5b:a0:c8:1a:fe:b5:8c:08:86:7f:c5:a9:f1:
d9:2c:7e:5a:f4:ca:e8:c2:4b:44:70:35:e2:80:ea:ad:12:7c:
70:5e:2c:c9:1f:db:9b:0e:f7:cf:68:a3:93:da:33:18:f2:6c:
8e:4f:2b:ed:04:9d:c0:58:2e:66:d6:dc:25:30:6c:19:54:a2:
9f:68:7d:e7:63:d7:a9:db:6b:6e:e5:53:b4:27:84:98:dc:bc:
65:47:25:ae:7e:02:62:5c:c8:da:83:34:4e:5b:52:5d:5b:76:
bc:47:8f:cc:57:e0:b8:55:2b:6b:78:b0:e1:04:4a:1b:4b:20:
6d:e3:01:06:58:99:1c:1d:15:fb:2b:48:9a:b1:ad:84:fc:ed:
b2:31:98:5d:a2:97:26:69:0e:e6:0d:b4:2c:9b:40:7a:34:99:
e9:11:40:66:79:e1:0c:a9:7d:e7:47:bb:96:59:5a:af:f4:b3:
dc:73:5e:dc:8b:f5:97:88:b3:9d:0f:e0:fb:8a:63:a6:1e:af:
af:19:ea:c6:33:2a:97:a9:f1:bd:cf:67:54:5c:30:bf:1e:5b:
1c:68:9f:ba:91:4b:2f:3a:05:c5:be:43:fc:1a:0c:e1:32:29:
2a:08:04:a7:00:32:33:5b:19:56:17:61:e3:8d:7d:a3:b2:f9:
a8:9d:24:a6:9c:9c:ab:12:09:c3:b3:12:db:8b:8b:39:5b:f8:
09:5e:a0:48:eb:e0:8e:f3:cb:83:d2:89:43:c4:64:06:30:ec:
fa:69:ed:96:08:67:b0:20:48:d8:e9:b2:1e:1b:66:0b:80:3e:
81:0e:cd:2b:a6:5e:07:de:40:b1:70:bd:b8:fb:bf:30:ad:b9:
66:6b:a2:48:da:4e:27:ab:ae:06:13:ec:61:1f:79:bc:e6:c1:
4a:ef:75:f4:a1:bf:28:3d:f2:99:de:f3:71:84:cf:1c:58:17:
4d:66:97:8a:fe:f9:1c:77:ab:5d:b2:d9:20:93:ff:a3:c2:7c:

一旦CA机构返回签名证书，请打开证书。导航到Details菜单并查找Subject Alternative Names。您可以看到证书本身上的SAN值。