Configure vsftpd with SSL

準備 CA 憑證檔

方式一：使用自我簽署(Self-Signed)

mkdir /etc/vsftpd/cert

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/vsftpd/cert/mydomain.key -out /etc/vsftpd/cert/mydomain.crt

NOTE:

建立自我簽署檔時，下列輸入的資訊必須與事實相符，以便於後續的憑證資訊查詢:
Country Name: TW  國碼
State or Province Name: TAIWAN 州/省別
Locality Name: Taoyuan 城市
Organization Name: Your Company Corp. 公司名
Organization Unit Name: IT 公司組織單位名稱
Common Name: your.domain.name 網址 (*最重要*)

方式二：使用第三方機構簽署 TWNCA

使用 Linux 主機產生兩個檔案

1. mydomain.key 伺服器金鑰檔
2. mydomain.csr 憑證簽署請求檔

openssl genrsa -out /etc/vsftpd/cert/mydomain.key 2048
openssl req -new -key /etc/vsftpd/cert/mydomain.key -out /etc/vsftpd/cert/mydomain.csr

NOTE:

輸入以下資訊必須與事實相符
Country Name: TW  國碼
State or Province Name: TAIWAN 州/省別
Locality Name: Taoyuan 城市
Organization Name: Your Company Corp. 公司名
Organization Unit Name: IT 公司組織單位名稱
Common Name: your.domain.name 網址 (*最重要*)

將上述檔案 mydomain.csr 上傳至 TWCA 官網，並完成申請簽署的程序。一旦官方完成憑證簽署，會以 Email 方式通知，並可以下載簽署後的憑證檔

TWCA 簽署後的憑證檔包含下述檔案
- root.crt 根憑證檔
- server.crt 伺服器憑證檔
- uca_1.crt 中繼憑證#1檔
- uca_2.crt 中繼憑證#2檔

簽署後的憑證檔內容類似這樣

#> cat server.crt

-----BEGIN CERTIFICATE-----
MIIFNjCCBB6gAwIBAgIQR+AAAAAANxpF4wYFvl5COzANBgkqhkiG9w0BAQsFADBv
MQswCQYDVQQGEwJUVzESMBAGA1UEChMJVEFJV0FOLUNBMRowGAYDVQQLExFTZWN1
cmUgU1NMIFN1Yi1DQTEwMC4GA1UEAxMnVFdDQSBTZWN1cmUgU1NMIENlcnRpZmlj
...
KiZDoZe0ziN7Usrzb5CNgzZj9tP09KPF8wepQlMWOu5lHb84IroCHaAhb56zbwmy
4TU/SwImtZT5L+j68W3AhqeYX7u42lscl/Qda7b/nES/lcN8yH9y7zKP6PriCP9A
np13mawkqJi34dkoFobJ9tqitigMRs82dcMVVzbBEUK8e4e7pYoLe0iP
-----END CERTIFICATE-----

#> openssl x509 -noout -text -in server.crt

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            47:e0:00:00:00:00:37:1a:45:e3:06:05:be:5e:42:3b
        Signature Algorithm: sha256WithRSAEncryption                注意: Issuer 表示憑證發行單位
        Issuer: C=TW, O=TAIWAN-CA, OU=Secure SSL Sub-CA, CN=TWCA Secure SSL Certification Authority
        Validity
            Not Before: Jan 28 09:48:26 2016 GMT                                      注意: 憑證有效日期
            Not After : Jan 28 15:59:59 2019 GMT
        Subject: C=TW, ST=TAIWAN, L=Taoyuan, O=Your Company Corp., OU=IT, CN=your.domain.name
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (2048 bit)
                Modulus (2048 bit):
                    00:a7:6c:96:42:5c:84:ca:ee:82:1d:de:49:5e:d5:
                    d6:37:2b:78:5f:48:57:df:55:33:84:06:9a:49:af:
                    d5:ca:0f:bf:44:e1:0c:c6:af:17:8f:e6:0c:19:34:
                    ed:7b:6c:26:02:03:38:f1:af:2e:70:0c:3d:d9:0a:
                    71:78:26:fb:9f:75:5e:34:c4:6e:0c:44:74:99:40:
                    19:60:41:fb:dd:71:0f:fe:2f:82:34:cf:9d:a0:08:
                    ...
                    a6:ee:b9:3e:24:4a:af:c5:62:7f:1b:8a:03:a9:37:
                    83:45:43:be:b4:cc:ac:0a:54:62:89:0e:f3:74:10:
                    71:b9:1c:1f:47:00:ba:3d:43:f5:32:51:b2:99:e1:
                    4f:65
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Authority Key Identifier:
                keyid:F8:07:C2:68:24:FF:85:95:CB:DB:1E:E3:33:9C:2A:4F:97:20:56:7B

            X509v3 Subject Key Identifier:
                4D:1D:44:34:1D:D6:07:64:4A:98:F2:BD:B8:64:F6:6E:21:0B:FC:8D:AA:93:CA:0A:60:AD:10:C7:2A:59:FC:FE
            X509v3 CRL Distribution Points:
                URI:http://sslserver.twca.com.tw/sslserver/Securessl_revoke_sha2_2014.crl

            X509v3 Subject Alternative Name:
                DNS:ftp.winfoundry.com
            Authority Information Access:
                CA Issuers - URI:http://sslserver.twca.com.tw/cacert/secure_sha2_2014.crt
                OCSP - URI:http://twcasslocsp.twca.com.tw/

            X509v3 Certificate Policies:
                Policy: 1.3.6.1.4.1.40869.1.1.25
                  CPS: www.twca.com.tw

            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment
            X509v3 Extended Key Usage:
                TLS Web Server Authentication, TLS Web Client Authentication
    Signature Algorithm: sha256WithRSAEncryption
        6e:54:75:c3:b6:0f:b1:73:93:c0:28:c9:b3:ee:91:79:1e:1b:
        42:46:90:b1:81:0c:d8:3a:2c:94:95:7c:03:d3:b4:83:48:a9:
        13:f0:06:23:04:b6:ca:21:c6:49:2e:0a:ee:f9:54:70:f7:15:
        ...
        0c:46:cf:36:75:c3:15:57:36:c1:11:42:bc:7b:87:bb:a5:8a:
        0b:7b:48:8f 

上述檔案在這篇教學只會用到 server.crt

cp server.crt /etc/vsftpd/cert/mydomain.crt

chown root:root /etc/vsftpd/cert/mydomain.crt
chmod 0600 /etc/vsftpd/cert/mydomain.crt

TIP：

檔案權限設定主要是考慮系統安全性，與服務是否正常運作無關。

設定 vsftpd

需要的檔案：

1. mydomain.key 伺服器金鑰檔
2. mydomain.crt 伺服器憑證檔

編輯 /etc/vsftpd/vsftpd.conf
加上這幾行

# SSL Configuration
rsa_private_key_file=/etc/vsftpd/cert/mydomain.key
rsa_cert_file=/etc/vsftpd/cert/mydomain.crt
ssl_enable=YES
allow_anon_ssl=NO
force_local_data_ssl=YES
force_local_logins_ssl=YES
ssl_tlsv1=YES
ssl_sslv2=NO
ssl_sslv3=NO
ssl_ciphers=HIGH

TIP：

force_local_data_ssl=YES
force_local_logins_ssl=YES
如果設定 NO，client 可使用加密與不加密連線，YES 強制使用加密連線。

ssl_sslv2=NO
ssl_sslv3=NO
因為 ssl 協定不太安全，建議只保留 TLS。

重啟 vsftpd

service vsftpd restart

F.A.Q

openssl x509 -noout -text -in /etc/vsftpd/cert/mydomain.crt
openssl rsa -noout -text -in /etc/vsftpd/cert/mydomain.key

延伸閱讀

• SECURE LINUX FTP SERVER (VSFTPD SERVER) USING SSL ENCRYPTION / TLS ENCRYPTION