為使用OpenSSL的憑證設定SAN值

簡介

本文介紹如何在使用OpenSSL建立的憑證上設定多個使用者替代名稱(SAN)值。

必要條件

需求

思科建議您瞭解以下主題的基本知識：

• 安全通訊端層(SSL)憑證
• OpenSSL
• Linux命令
• SAN

採用元件

本檔案中的資訊是根據以下軟體版本：

• OpenSSL版本CiscoSSL 1.1.1j.7.2sp.230
• 內部憑證授權單位(CA)

本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。

背景資訊

在證書中使用SAN值是目前常見的做法，對於各種應用(如遠端接入VPN(RAVPN)身份驗證或零信任網路接入(ZTNA)裝置的SSL證書)來說都是必不可少的。這些應用程式通常需要包含多個SAN值的證書來安全地支援不同的域名或IP地址。

預設情況下，Cisco Firepower Management Center(FMC)或其他CSR生成器等工具生成的證書簽名請求(CSR)通常不包括新增多個SAN值的選項。這種限制導致證書中僅包含單個SAN值，不能滿足現代網路環境的需求。

設定

為克服此限制，建議的方法是使用OpenSSL等工具將SAN值直接新增到CSR。這確保在證書頒發機構(CA)簽署CSR時，生成的證書包含所需的SAN條目。此過程的關鍵是修改OpenSSL配置或使用指定SAN值的相應配置檔案。這樣，CSR會明確包括SAN擴展，允許CA根據需要使用多個SAN頒發證書。

附註：如果使用第三方或已知的CA，請在提交之前驗證CA是否支援CSR中的自訂SAN值。

步驟1.建立RSA私鑰

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

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

步驟2.建立配置檔案

此檔案指定要包含在CSR中的SAN值。

1.建立名為<config_file_name>.conf的配置檔案，並使用文本編輯器編輯該檔案。例如，在Vim中運行<config_file_name>.conf命令（您可以使用另一個文本編輯器）。

vim config.conf

2.新增此內容，在[alt_names]部分下用您的實際證書詳細資訊和所需的SAN條目替換佔位符值：

[ 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 = 

步驟3.使用私鑰和組態檔請求CSR

使用先前建立的私鑰和組態檔，使用openssl req -new <key_name>.key -config <conf_name>.conf -out <CSR_Name>.csr指令建立CSR。

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

附註：運行此命令時，請確保私鑰和配置檔案位於同一目錄中。

執行此命令後，<CSR_name>.csr檔案會出現在資料夾中。這是必須傳送到CA伺服器進行簽名的CSR檔案。

驗證

執行openssl req -text -noout -verify -in CSR.csr命令，以確保CSR中的SAN值可用。

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機構返回簽名證書，請開啟證書。導航到Details選單並找到Subject Alternative Names。您可以在憑證本身上看到SAN值。