2014年3月18日 星期二

Python M2Crypto - X.509 Certificate Sign Request 與 Sign Certificate


X.509 憑證基本觀念

X.509 是由 ITU-T 所製定的 PKI 標準，它主要包含以下 4 個規範：
  1. public key certificates
  2. certificate revocation lists
  3. attribute certificates
  4. certification path validation algorithm
X.509 的憑證簽發關係的概念圖如下：


產生 Root CA Certificate

  • 產生一把 RSA key pair (public / private keys) 
  • 準備一個 Root CA 憑證, 以及所需要的資訊，並且設定有效期限(一般來說是10~20年)。
  • 設定此 Root CA 憑證的 X.509 V3 的 Extension 
  • 用此 Root CA 的 RSA private key 來簽署這個憑證( Self-Signed Root CA Certificate)
產生 Self-Signed Root CA Certificate 的基本範例程式:
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import M2Crypto
import time
import os
import struct
from M2Crypto import X509, EVP, ASN1

def generate_rsa_keypair(key_len, exponent):
    def empty_callback():
        pass
    rsa = M2Crypto.RSA.gen_key(key_len, exponent, empty_callback)
    return rsa

def create_self_signed_RootCA_certificate(root_ca_info, sign_method="sha256", days=3650):
    # Setp 1: Create RSA-key pair (public/private key)
    rsa = generate_rsa_keypair(2048, 65537)
    private_key = EVP.PKey()
    private_key.assign_rsa(rsa)
    
    # Step 2-1: Prepare X.509 Certificate Signed Request
    req = X509.Request()
    req.set_pubkey(private_key)
    x509_name = req.get_subject()
    x509_name.C = root_ca_info["C"]
    x509_name.CN = root_ca_info["CN"]
    x509_name.ST = root_ca_info["ST"]
    x509_name.L = root_ca_info["L"]
    x509_name.O = root_ca_info["O"]
    x509_name.OU = root_ca_info["OU"]
    req.sign(private_key,sign_method)
    # Step 2-2: Prepare X.509 certificate
    root_ca_cert = X509.X509()
    
    serial = struct.unpack("<Q", os.urandom(8))[0]
    root_ca_cert.set_serial_number(serial)
    root_ca_cert.set_version(3)
    # Setp 2-3: Set required information of RootCA certificate
    root_ca_cert.set_issuer(x509_name)
    root_ca_cert.set_subject(root_ca_cert.get_issuer())
    root_ca_cert.set_pubkey(req.get_pubkey())  # Get the CSR's public key    

    # Step 2-4: Set Valid Date for RootCA certificate
    t = long(time.time())
    now = ASN1.ASN1_UTCTIME()
    now.set_time(t)
    expire = ASN1.ASN1_UTCTIME()
    expire.set_time(t + days * 24 * 60 * 60)
    root_ca_cert.set_not_before(now)
    root_ca_cert.set_not_after(expire)
    # Step 3: Add Extensions for this Root CA certificate
    root_ca_cert.add_ext(X509.new_extension('basicConstraints', 'CA:TRUE'))
    root_ca_cert.add_ext(X509.new_extension('subjectKeyIdentifier', root_ca_cert.get_fingerprint()))
    
    # Step 4: Use Root CA's RSA private key to sign this certificate
    root_ca_cert.sign(private_key, sign_method)
    return root_ca_cert, private_key

if __name__ == '__main__':
    # Generate a Self-Signed Root CA Certificate
    root_ca_info = {}
    root_ca_info['C'] = "TW"
    root_ca_info['CN'] = "Root CA Certificate"
    root_ca_info['ST'] = "Taiwan"
    root_ca_info['O'] = "ijeCorp Ltd."
    root_ca_info['OU'] = "Security"
    root_ca_info['L'] = "Taipei"
    
    root_ca_cert, private_key = create_self_signed_RootCA_certificate(root_ca_info)
    with open('root_ca_cert.crt', 'w') as f:
        f.write(root_ca_cert.as_pem())
    with open('root_ca_private_key.pem', 'w') as f:
        f.write(private_key.as_pem(cipher=None))
    with open('root_ca_public_key.pem', 'w') as f:
        f.write(root_ca_cert.get_pubkey().as_pem(cipher=None))


產生 Certificate Signed Certificate 

  • 產生一把 RSA key pair (public/private key)
  • 準備一個 X.509 Request 
  • 設定 X.509 Request 的資訊
  • 用 RSA private key 去簽署這個 X.509 Request
產生 Certificate Signed Certificate (CSR) 的基本範例程式:
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import M2Crypto
from M2Crypto import X509, EVP

def generate_rsa_keypair(key_len, exponent):
    def empty_callback():
        pass

    rsa = M2Crypto.RSA.gen_key(key_len, exponent, empty_callback)
    return rsa

def create_Signed_Certificate_Request(csr_info, key_len=2048, sign_method="sha256"):
    # Step 1: Create a RSA key pair (public/private key)
    rsa_keypair = generate_rsa_keypair(key_len, 65537)
    evp_private_key = EVP.PKey()
    evp_private_key.assign_rsa(rsa_keypair)
    # Step 2: Create a X.509 request 
    csr = X509.Request()
    csr.set_pubkey(evp_private_key)
    # Step 3: Set CSR information
    x509_name = csr.get_subject()
    x509_name.C = csr_info['C']
    x509_name.CN = csr_info['CN']
    x509_name.ST = csr_info['ST']
    x509_name.O = csr_info['O']
    x509_name.OU = csr_info['OU']
    x509_name.L = csr_info['L']

    # Step 4: Use RSA private key to sign it
    csr.sign(evp_private_key, sign_method)
    return csr, evp_private_key

if __name__ == '__main__':
    # Generate CSR for signed Certificate
    csr_info = {}
    csr_info['C'] = "TW"
    csr_info['CN'] = "CA-Certificate"
    csr_info['ST'] = "Taiwan"
    csr_info['O'] = "AbcCorp Ltd."
    csr_info['OU'] = "ABC-CA"
    csr_info['L'] = "Taipei"

    csr, private_key = create_Signed_Certificate_Request(csr_info);

    with open('CSR.pem', 'w') as f:
        f.write(csr.as_pem())
    with open('CSR_private_key.pem', 'w') as f:
        f.write(private_key.as_pem(cipher = None))

Root CA 或是 CA 根據 CSR 簽署一個 Certificate

  • 準備一個 X.509 的憑證
  • 設定 X.509 憑證的有效期限, 有效時間的長短根據需求而有不同
  • 設定 X.509 的 Extension 資訊
  • 根據 CSR 所提供的 subject 以及 public key 來設定 X.509 憑證
  • 使用 Root CA 或是 CA 的 RSA private key 來簽署這個 X.509 憑證
Root CA 根據 CSR 產生 Certificate 的基本範例程式:
此範例程式，只需要研讀 Line 130~133 與 Line 14~47 即可，它是直接以 Root CA 的 private key並且依據 CSR 來簽署憑證


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import M2Crypto
import time
import os
import struct
from M2Crypto import X509, EVP, ASN1

def generate_rsa_keypair(key_len, exponent):
    def empty_callback():
        pass

    rsa = M2Crypto.RSA.gen_key(key_len, exponent, empty_callback)
    return rsa

def create_certificate_from_CSR(rootCA_cert, rootCA_private_key, csr, days = 365):
    # Step 1: Prepare X.509 Certificate
    cert = X509.X509()
    serial = struct.unpack("<Q", os.urandom(8))[0]
    cert.set_serial_number(serial)
    cert.set_version(3)
    # Step 2: Set Expired Date
    t = long(time.time())
    now = ASN1.ASN1_UTCTIME()
    now.set_time(t)
    expire = ASN1.ASN1_UTCTIME()
    expire.set_time(t + days * 24 * 60 * 60)
    cert.set_not_before(now)
    cert.set_not_after(expire)
    # Step 3: Set X.509 Extensions
    cert.add_ext(X509.new_extension('nsComment', 'SSL sever'))
    cert.add_ext(X509.new_extension('keyUsage', 'Digital Signature')) 
    cert.add_ext(X509.new_extension('keyUsage', 'Key Encipherment', 1)) # 1 means critical
    cert.add_ext(X509.new_extension('keyUsage', 'Data Encipherment',1))
    cert.add_ext(X509.new_extension('keyUsage', 'Key Agreement', 1))
    cert.add_ext(X509.new_extension('extendedKeyUsage', 'clientAuth'))
    cert.add_ext(X509.new_extension('basicConstraints', 'CA:TRUE'))
    cert.add_ext(X509.new_extension('subjectAltName', 'DNS:www.ijecorp.com'))
    PCI_FULL = "critical, language:Inherit all"
    PCI_LIMITED = "critical, language:1.3.6.1.4.1.3536.1.1.1.9"
    cert.add_ext(X509.new_extension('proxyCertInfo',PCI_FULL, 1))
    # Step 4: Set Subject and Public Key from CSR
    cert.set_issuer(rootCA_cert.get_issuer())
    cert.set_subject(csr.get_subject())
    cert.set_pubkey(csr.get_pubkey())
    # Step 5: Use Private Key of Root CA or CA to sign this X.509 certificate
    cert.sign(rootCA_private_key, 'sha256')

    return cert

def create_Signed_Certificate_Request(csr_info, key_len=2048, sign_method="sha256"):
    # Step 1: Create a RSA key pair (public/private key)
    rsa_keypair = generate_rsa_keypair(key_len, 65537)
    evp_private_key = EVP.PKey()
    evp_private_key.assign_rsa(rsa_keypair)
    # Step 2: Create a X.509 request 
    csr = X509.Request()
    csr.set_pubkey(evp_private_key)
    # Step 3: Set CSR information
    x509_name = csr.get_subject()
    x509_name.C = csr_info['C']
    x509_name.CN = csr_info['CN']
    x509_name.ST = csr_info['ST']
    x509_name.O = csr_info['O']
    x509_name.OU = csr_info['OU']
    # Step 4: Use RSA private key to sign it
    csr.sign(evp_private_key, sign_method)
    return csr, evp_private_key

def create_self_signed_RootCA_certificate(root_ca_info, sign_method="sha256", days=3650):
    # Setp 1: Create RSA-key pair (public/private key)
    rsa = generate_rsa_keypair(2048, 65537)
    private_key = EVP.PKey()
    private_key.assign_rsa(rsa)
    # Step 2-1: Prepare X.509 Certificate Signed Request
    req = X509.Request()
    req.set_pubkey(private_key)
    x509_name = req.get_subject()
    x509_name.C = root_ca_info["C"]
    x509_name.CN = root_ca_info["CN"]
    x509_name.ST = root_ca_info["ST"]
    x509_name.L = root_ca_info["L"]
    x509_name.O = root_ca_info["O"]
    x509_name.OU = root_ca_info["OU"]
    req.sign(private_key,sign_method)
    # Step 2-2: Prepare X.509 certificate
    root_ca_cert = X509.X509()
    serial = struct.unpack("<Q", os.urandom(8))[0]
    root_ca_cert.set_serial_number(serial)
    root_ca_cert.set_version(3)
    # Setp 2-3: Set required information of RootCA certificate
    root_ca_cert.set_issuer(x509_name)
    root_ca_cert.set_subject(root_ca_cert.get_issuer())
    root_ca_cert.set_pubkey(req.get_pubkey())  # Get the CSR's public key    

    # Step 2-4: Set Valid Date for RootCA certificate
    t = long(time.time())
    now = ASN1.ASN1_UTCTIME()
    now.set_time(t)
    expire = ASN1.ASN1_UTCTIME()
    expire.set_time(t + days * 24 * 60 * 60)
    root_ca_cert.set_not_before(now)
    root_ca_cert.set_not_after(expire)
    # Step 3: Add Extensions for this Root CA certificate
    root_ca_cert.add_ext(X509.new_extension('basicConstraints', 'CA:TRUE'))
    root_ca_cert.add_ext(X509.new_extension('subjectKeyIdentifier', root_ca_cert.get_fingerprint()))
    
    # Step 4: Use Root CA's RSA private key to sign this certificate
    root_ca_cert.sign(private_key, sign_method)
    return root_ca_cert, private_key

if __name__ == '__main__':
    # Generate a Self-Signed Root CA Certificate
    root_ca_info = {}
    root_ca_info['C'] = "TW"
    root_ca_info['CN'] = "Root CA Certificate"
    root_ca_info['ST'] = "Taiwan"
    root_ca_info['O'] = "ijeCorp Ltd."
    root_ca_info['OU'] = "Security"
    root_ca_info['L'] = "Taipei"
    root_ca_cert, root_ca_private_key = create_self_signed_RootCA_certificate(root_ca_info)

    # Generate CSR for signed Certificate
    csr_info = {}
    csr_info['C'] = "TW"
    csr_info['CN'] = "MyCompany-Certificate"
    csr_info['ST'] = "."
    csr_info['O'] = "ijeCorp Ltd."
    csr_info['OU'] = "Security"
    csr, ca_private_key = create_Signed_Certificate_Request(csr_info);

    # Use Root CA's private key to sign a certificate from CSR
    cert = create_certificate_from_CSR(root_ca_cert, root_ca_private_key, csr)
    with open('my_cert.crt', 'w') as f:
        f.write(cert.as_pem())
以上的範例程式都是採用 SHA-256 是基於安全性的考量，請參考[2]

Reference:
[1] http://svn.osafoundation.org/m2crypto/trunk/contrib/SimpleX509create.py
[2] http://www.tbs-certificates.co.uk/FAQ/en/475.html


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2014年3月12日 星期三

OpenSSL - 金鑰與憑證的管理

Key and Certificate Management

要讓 Web 或者 Service 能夠支援 SSL, 基本上有三個步驟：
1. 產生私有金鑰 (Private Key)
2. 產生 CSR (Certificate Signing Request), 並將 CSR 傳送給 CA
3. 把 CA 所提供的憑證 (Certificate) 安裝在 Web 或 Service的伺服器上

以下利用 OpenSSL 來說明如何完成以上 3 個步驟.

Key Generation

使用 openssl 產生私有金鑰 (private key) 的指令如下：

~$ openssl genrsa -aes256 -out private.key 2048

以下是執行後的輸出畫面, 會要求輸入Pass phrase 來保護這個 RSA private key.

Generating RSA private key, 2048 bit long modulus
.+++
.............................................+++
e is 65537 (0x10001)
Enter pass phrase for private.key:
Verifying - Enter pass phrase for private.key:


這是產生一把長度為 2048 bits 的 RSA private key, 並且使用 AES-256 與輸入的 Pass phrase 來保護這把 Private key。基本上, RSA的 Private key 長度建議至少是2048 bits才是比較安全的。執行後的結果 private.key 是一個加密後的檔案並且以 PEM 的格式儲存，內容類似以下：

-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-256-CBC,4616B291C58D187CE9787AD421E7DA80
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-----END RSA PRIVATE KEY-----

Creating Certificate Signing Requests (CSR)

為了向公開具備公信力的 CA 單位提出憑證申請, 必須要提供一個 CSR 的檔案給這個 CA單位。以下就是透過 openssl 使用先前產生的 RSA 金鑰來產生一個 CSR 的檔案，過程當中需要輸入一些相關的資料(可以參考以下範例中的黑色斜線粗體部份)
$ openssl req -new -key private.key -out CSR.csr

Enter pass phrase for private.key:
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]:TW
State or Province Name (full name) [Some-State]:.            
Locality Name (eg, city) []:Taipei
Organization Name (eg, company) [Internet Widgits Pty Ltd]:ijeCorp        
Organizational Unit Name (eg, section) []:Security
Common Name (e.g. server FQDN or YOUR name) []:www.ijecorp.com
Email Address []:miller.lai@gmail.com

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:IM@R.O.C    
An optional company name []:ijeCorp

產生 CSR 後, 可以透過 openssl 來檢測 CSR的內容是否正確，指令如下：
~$ openssl req -text -in CSR.csr -noout

執行後的輸出結果如下：
Certificate Request:
    Data:
        Version: 0 (0x0)
        Subject: C=TW, L=Taipei, O=ijeCorp, OU=Security, CN=www.ijecorp.com/emailAddress=miller.lai@gmail.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:b2:fb:c9:5f:4c:0f:2a:11:d7:81:05:a9:e6:41:
                    43:35:b7:47:ba:be:58:42:32:ad:e9:99:be:c8:82:
                    57:73:ca:87:6c:f9:90:15:1d:4a:6d:cc:fc:81:e2:
                    2e:c2:1f:ed:fd:ae:45:cd:ce:c9:6c:43:f1:47:ef:
                    aa:8d:f8:e3:32:52:10:80:db:0a:b5:fa:be:91:87:
                    94:08:57:86:8e:6b:86:f6:63:05:2d:53:3c:c3:4c:
                    48:ad:4d:ee:f2:de:7c:68:9d:f7:01:5b:a1:99:2e:
                    69:60:b8:b1:59:4c:d8:69:7a:cf:47:bb:3c:c6:6f:
                    5d:99:08:5d:e8:5e:bd:34:e2:52:00:9c:70:62:89:
                    4b:aa:c6:8c:d7:0d:a0:fc:d7:1d:bf:18:9a:d4:e2:
                    b6:f8:26:5d:0b:bb:b0:af:4d:7e:ee:f8:22:cc:18:
                    7f:b7:a4:b4:12:c1:78:34:ed:29:30:b3:fa:93:97:
                    04:4c:a2:32:3b:f4:cb:98:52:6f:ea:11:ab:01:8d:
                    03:b6:d3:b4:cb:0e:f8:3d:cf:2f:ae:3b:51:c9:1d:
                    16:15:e2:d6:cc:8b:35:8e:df:70:c2:c5:18:b7:8f:
                    9f:42:a3:d9:99:55:c0:74:f3:ab:40:98:d0:0a:4d:
                    99:12:2e:92:5b:d6:d3:d6:73:2c:01:76:96:ea:8d:
                    fd:d5
                Exponent: 65537 (0x10001)
        Attributes:
            unstructuredName         :unable to print attribute
            challengePassword        :unable to print attribute
    Signature Algorithm: sha1WithRSAEncryption
         0b:5c:f4:d5:ae:f3:4a:4b:9b:d2:8e:e6:cd:b6:20:2c:9d:61:
         57:f3:9d:7f:95:03:71:9e:95:1b:4c:8f:ad:f8:f9:6c:c3:a6:
         32:be:6a:b9:bf:45:81:0a:6f:6d:3c:29:f6:90:00:81:73:ac:
         65:8d:19:ea:39:86:5d:8f:2b:d7:bf:2f:02:63:01:bb:87:0f:
         dd:3d:81:b2:3c:72:1c:d4:ad:9e:ba:35:e6:41:f2:2f:fb:b8:
         0e:9f:5d:26:2b:52:37:a3:7f:97:b0:35:78:a6:d4:5a:4f:df:
         32:15:9f:45:43:04:95:4e:f4:d6:71:68:57:59:b2:5b:28:e3:
         13:73:96:c8:cf:c1:df:56:e4:b0:f2:d9:ee:e2:67:7a:37:d2:
         ba:f6:17:9e:ca:6a:b2:96:6d:e8:bb:cf:ff:17:13:fb:cc:d6:
         05:95:c2:4b:f9:49:b9:67:d8:c3:39:c9:78:00:56:20:6f:d4:
         2c:5c:66:c7:a0:1b:bd:2f:5d:c7:8b:98:69:93:67:be:44:f6:
         84:b9:8b:ec:45:1b:be:b8:5b:e9:94:00:2f:1c:30:ad:5f:c1:
         57:3c:f9:11:e0:49:85:bd:93:e6:09:54:aa:94:d5:31:b4:89:
         40:8d:c3:b8:e7:f9:80:d7:71:62:dd:51:88:71:51:ed:8f:b4:
         5e:12:93:3a

在確認 CSR 內容正確後，就可以將 CSR 傳送到公認且有公信力的 CA 單位，並請求該單位為此 CSR 產生憑證 (Certificate)。一旦取得 CA 為此 CSR 產生的憑證後, 就可以將它安裝在需要支援 SSL 的伺服器上。

但是，如果只是開發階段需要測試，或只是自己的想要使用並不是要公開對外支援 SSL時候，可以自行產生一個所謂 Self-signed 的憑證。產生 Self-signed 憑證的方式如下：

~$ openssl x509 -req -days 365 -in CSR.csr -signkey private.key -out self-signed.crt

以下是執行後的輸出畫面, 會要求輸入Pass phrase 來取得 private.key 進行 sign 憑證的處理。最後產生一個 PEM 格式的憑證內容在 self-signed.crt 檔案中
Signature ok
subject=/C=TW/L=Taipei/O=ijeCorp/OU=Security/CN=www.ijecorp.com/emailAddress=miller.lai@gmail.com
Getting Private key
Enter pass phrase for private.key:

PEM格式的 self-signed.crt 的內容類似如下：
-----BEGIN CERTIFICATE-----
MIIDgjCCAmoCCQCQyr2MuBjL8jANBgkqhkiG9w0BAQUFADCBgjELMAkGA1UEBhMC
VFcxDzANBgNVBAcMBlRhaXBlaTEQMA4GA1UECgwHaWplQ29ycDERMA8GA1UECwwI
U2VjdXJpdHkxGDAWBgNVBAMMD3d3dy5pamVjb3JwLmNvbTEjMCEGCSqGSIb3DQEJ
ARYUbWlsbGVyLmxhaUBnbWFpbC5jb20wHhcNMTQwMzEyMDEzODU2WhcNMTUwMzEy
MDEzODU2WjCBgjELMAkGA1UEBhMCVFcxDzANBgNVBAcMBlRhaXBlaTEQMA4GA1UE
CgwHaWplQ29ycDERMA8GA1UECwwIU2VjdXJpdHkxGDAWBgNVBAMMD3d3dy5pamVj
b3JwLmNvbTEjMCEGCSqGSIb3DQEJARYUbWlsbGVyLmxhaUBnbWFpbC5jb20wggEi
MA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCy+8lfTA8qEdeBBanmQUM1t0e6
vlhCMq3pmb7Igldzyods+ZAVHUptzPyB4i7CH+39rkXNzslsQ/FH76qN+OMyUhCA
2wq1+r6Rh5QIV4aOa4b2YwUtUzzDTEitTe7y3nxonfcBW6GZLmlguLFZTNhpes9H
uzzGb12ZCF3oXr004lIAnHBiiUuqxozXDaD81x2/GJrU4rb4Jl0Lu7CvTX7u+CLM
GH+3pLQSwXg07Skws/qTlwRMojI79MuYUm/qEasBjQO207TLDvg9zy+uO1HJHRYV
4tbMizWO33DCxRi3j59Co9mZVcB086tAmNAKTZkSLpJb1tPWcywBdpbqjf3VAgMB
AAEwDQYJKoZIhvcNAQEFBQADggEBAIqbY8rKAJ40JIXmtJJSWrLzZ5R9OXyxKWHy
N/8Szn8oLMeSPX6Fmd2oWGbJEDuHf17l9IkbKnfDIrlW+lbVG4qY2fZmH5GA2rmP
bWMrIzXqH+NJfp9NyUhhCCT59fDrHKiGf13opR8gvOo2ft0GOQ+kZsUn/7t1GoQ9
3Ybch2CNjfob5sEQ+nGDsyg3IRFnunAzeAdKLS9h4BwZOdz2lvVnHNR4Wb/TygDZ
mVL2ntg2uWCWQvJ5QCZlyjXthtp0EeDNiJeL3ThOlsiKujuhjMrqjThZuGqvpVxO
3v46/+iqCkdGuP/C2mZqJwbNYvOoPCBCeBYMXGpDrC2VqwYULy4=
-----END CERTIFICATE-----

此外，如果想要直接從 private key 產生 self-signed 憑證也是可以, 執行的指令如下：

~$ openssl req -new -x509 -days 365 -key private.key -out self-signed-2.crt

但是, 因為 Self-signed 憑證並不是透過公認與具有公信力的 CA 所發行的憑證。因此，當 Web 伺服器是安裝 Self-signed 的憑證來支援 SSL時，一般不同的瀏覽器在第一次瀏覽此網站時，遇到 self-signed 憑證時, 會跳出類似如下圖的畫面。



無論你是透過 CA 取得憑證或是自行產生 self-signed 的憑證, 都可以透過 openssl 指令來檢測憑證的內容，透過以下的指令：
~$ openssl x509 -text -in self-signed.crt -noout

執行後輸出的憑證內容如下，因為它是 self-signed 的憑證，所以只會有基本的資訊：
Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number: 10433359898838879218 (0x90cabd8cb818cbf2)
    Signature Algorithm: sha1WithRSAEncryption
        Issuer: C=TW, L=Taipei, O=ijeCorp, OU=Security, CN=www.ijecorp.com/emailAddress=miller.lai@gmail.com
        Validity
            Not Before: Mar 12 01:38:56 2014 GMT
            Not After : Mar 12 01:38:56 2015 GMT
        Subject: C=TW, L=Taipei, O=ijeCorp, OU=Security, CN=www.ijecorp.com/emailAddress=miller.lai@gmail.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:b2:fb:c9:5f:4c:0f:2a:11:d7:81:05:a9:e6:41:
                    43:35:b7:47:ba:be:58:42:32:ad:e9:99:be:c8:82:
                    57:73:ca:87:6c:f9:90:15:1d:4a:6d:cc:fc:81:e2:
                    2e:c2:1f:ed:fd:ae:45:cd:ce:c9:6c:43:f1:47:ef:
                    aa:8d:f8:e3:32:52:10:80:db:0a:b5:fa:be:91:87:
                    94:08:57:86:8e:6b:86:f6:63:05:2d:53:3c:c3:4c:
                    48:ad:4d:ee:f2:de:7c:68:9d:f7:01:5b:a1:99:2e:
                    69:60:b8:b1:59:4c:d8:69:7a:cf:47:bb:3c:c6:6f:
                    5d:99:08:5d:e8:5e:bd:34:e2:52:00:9c:70:62:89:
                    4b:aa:c6:8c:d7:0d:a0:fc:d7:1d:bf:18:9a:d4:e2:
                    b6:f8:26:5d:0b:bb:b0:af:4d:7e:ee:f8:22:cc:18:
                    7f:b7:a4:b4:12:c1:78:34:ed:29:30:b3:fa:93:97:
                    04:4c:a2:32:3b:f4:cb:98:52:6f:ea:11:ab:01:8d:
                    03:b6:d3:b4:cb:0e:f8:3d:cf:2f:ae:3b:51:c9:1d:
                    16:15:e2:d6:cc:8b:35:8e:df:70:c2:c5:18:b7:8f:
                    9f:42:a3:d9:99:55:c0:74:f3:ab:40:98:d0:0a:4d:
                    99:12:2e:92:5b:d6:d3:d6:73:2c:01:76:96:ea:8d:
                    fd:d5
                Exponent: 65537 (0x10001)
    Signature Algorithm: sha1WithRSAEncryption
         8a:9b:63:ca:ca:00:9e:34:24:85:e6:b4:92:52:5a:b2:f3:67:
         94:7d:39:7c:b1:29:61:f2:37:ff:12:ce:7f:28:2c:c7:92:3d:
         7e:85:99:dd:a8:58:66:c9:10:3b:87:7f:5e:e5:f4:89:1b:2a:
         77:c3:22:b9:56:fa:56:d5:1b:8a:98:d9:f6:66:1f:91:80:da:
         b9:8f:6d:63:2b:23:35:ea:1f:e3:49:7e:9f:4d:c9:48:61:08:
         24:f9:f5:f0:eb:1c:a8:86:7f:5d:e8:a5:1f:20:bc:ea:36:7e:
         dd:06:39:0f:a4:66:c5:27:ff:bb:75:1a:84:3d:dd:86:dc:87:
         60:8d:8d:fa:1b:e6:c1:10:fa:71:83:b3:28:37:21:11:67:ba:
         70:33:78:07:4a:2d:2f:61:e0:1c:19:39:dc:f6:96:f5:67:1c:
         d4:78:59:bf:d3:ca:00:d9:99:52:f6:9e:d8:36:b9:60:96:42:
         f2:79:40:26:65:ca:35:ed:86:da:74:11:e0:cd:88:97:8b:dd:
         38:4e:96:c8:8a:ba:3b:a1:8c:ca:ea:8d:38:59:b8:6a:af:a5:
         5c:4e:de:fe:3a:ff:e8:aa:0a:47:46:b8:ff:c2:da:66:6a:27:
         06:cd:62:f3:a8:3c:20:42:78:16:0c:5c:6a:43:ac:2d:95:ab:
         06:14:2f:2e

以下我們來觀察一個由公開 CA 所 signed 過的憑證內容, 有關 X509v3 extensions 的部分：
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            18:7a:a9:a8:c2:96:21:0c
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, O=Apple Inc., OU=Apple Certification Authority, CN=Apple Root CA
        Validity
            Not Before: Feb  1 22:12:15 2012 GMT
            Not After : Feb  1 22:12:15 2027 GMT
        Subject: CN=Developer ID Certification Authority, OU=Apple Certification Authority, O=Apple Inc., C=US
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (2048 bit)
                Modulus (2048 bit):
                    00:89:76:4f:06:5b:9a:41:ee:a5:23:2b:02:a3:5f:
                    d7:73:3f:c0:35:b0:8b:84:0a:3f:06:24:7f:a7:95:
                    3f:eb:4f:0e:93:af:b4:0e:d0:c8:3e:e5:6d:18:b3:
                    1f:e8:89:47:bf:d7:09:08:e4:ff:56:98:29:15:e7:
                    94:9d:b9:35:a3:0a:cd:b4:c0:e1:e2:60:f4:ca:ec:
                    29:78:45:69:69:60:6b:5f:8a:92:fc:9e:23:e6:3a:
                    c2:22:b3:31:4f:1c:ba:f2:b6:34:59:42:ee:b0:a9:
                    02:03:18:91:04:b6:b3:78:2e:33:1f:80:45:0d:45:
                    6f:bb:0e:5a:5b:7f:3a:e7:d8:08:d7:0b:0e:32:6d:
                    fb:86:36:e4:6c:ab:c4:11:8a:70:84:26:aa:9f:44:
                    d1:f1:b8:c6:7b:94:17:9b:48:f7:0b:58:16:ba:23:
                    c5:9f:15:39:7e:ca:5d:c3:32:5f:0f:e0:52:7f:40:
                    ea:be:ac:08:64:95:5b:c9:1a:9c:e5:80:ca:1f:6a:
                    44:1c:6c:3e:c4:b0:26:1f:1d:ec:7b:af:5e:a0:6a:
                    3d:47:a9:58:12:31:3f:20:76:28:6d:1d:1c:b0:c2:
                    4e:11:69:26:8b:cb:d6:d0:11:82:c9:4e:0f:f1:56:
                    74:d0:d9:08:4b:66:78:a2:ab:ac:a7:e2:d2:4c:87:
                    59:c9
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Key Identifier: 
                57:17:ED:A2:CF:DC:7C:98:A1:10:E0:FC:BE:87:2D:2C:F2:E3:17:54
            X509v3 Basic Constraints: critical
                CA:TRUE
            X509v3 Authority Key Identifier: 
                keyid:2B:D0:69:47:94:76:09:FE:F4:6B:8D:2E:40:A6:F7:47:4D:7F:08:5E

             X509v3 CRL Distribution Points: 
                URI:http://crl.apple.com/root.crl

             X509v3 Key Usage: critical
                Digital Signature, Certificate Sign, CRL Sign

 其中幾個比較重要的 X509 Extensions 相關說明如下：
X509v3 Basic Constraints 指定這個憑證是否屬於CA，另外是否為 critical 的限制。
例如：
X509v3 Basic Constraints: critical
    CA:TRUE

X509v3 Key Usage 指定這個憑證可以用來做什麼。
例如：

X509v3 Key Usage: critical
    Certificate Sign, CRL Sign

X509v3 Extended key Usage 指定這個憑證可以用在什麼操作上。
例如：
X509v3 Extended Key Usage: critical
    TLS Web Server Authentication, TLS Web Client Authentication

X509v3 CRL Distribution Points 指定CA所提供的 Revocation List 要去哪邊找。如果這個憑證是每隔一段時間就會更換的話，那麼這個設定就會非常重要。
例如：
X509v3 CRL Distribution Points: 

    Full Name:
      URI:http://www.apple.com/appleca/root.crl

X509v3 Certificate Policies 指定這個憑證是基於什麼 Policy 所簽發出來的。
例如：
X509v3 Certificate Policies: 

    Policy: 1.2.840.113635.100.5.1

      CPS: https://www.apple.com/appleca/

      User Notice:

        Explicit Text: Reliance on this certificate by any party assumes acceptance of the then applicable standard terms and conditions of use, certificate policy and certification practice statements.

Authority Information Access 是用來提供額外的CA資訊，以及即時驗證 certificate revocation的資料。而OCSP是指 CA's Online Certificate Status Protocol 的回應者 (responder)。
例如：
Authority Information Access:
    OCSP - URI: http://ocsp.starfieldtech.com/
    CA Issuers - URI:http://www.cert.com/resp/intermediate.crt

X509v3 Subject Key Identifier 主要在於表示這個 Certificate 包含一個特定的 Public Key。所有的CA Certificate都應該包含這個 extension, 由同一個 CA 所發出來的這些 Certificate 也要包含一個  X509v3 Authority Key Identifier 的 extension , 而它的值會和這個CA 的 Subject Key Identifier 一樣。

 X509v3 Authority Key Identifier 指定這張 Certificate 是由哪一個 CA 所發出來的。

 以下我們可以透過觀察 Facebook網站使用的 HTTPS Certificate來了解 Authority Key Identifier 和 Subject Key Identifier 的關係。








Root CA 是 DigCert  High  Assurance  EV Root CA 憑證的 Subject Key Identifier 和 Authority Key Identifier 分別如下：

X509v3 Subject Key Identifier: 
    B1:3E:C3:69:03:F8:BF:47:01:D4:98:26:1A:08:02:EF:63:64:2B:C3

 X509v3 Authority Key Identifier: 

    keyid:B1:3E:C3:69:03:F8:BF:47:01:D4:98:26:1A:08:02:EF:63:64:2B:C3

Root CA 所簽發的 Intermediate CA - DigiCert SHA2 High Assurance Server CA 憑證的 Subject Key Identifier 和 Authority Key Identifier 分別如下：

 X509v3 Subject Key Identifier: 
    51:68:FF:90:AF:02:07:75:3C:CC:D9:65:64:62:A2:12:B8:59:72:3B

 X509v3 Authority Key Identifier: 
    keyid:B1:3E:C3:69:03:F8:BF:47:01:D4:98:26:1A:08:02:EF:63:64:2B:C3

最後，由  Intermediate CA 所簽發的最後給Facebook的Web Server的憑證的 Subject Key Identifier 和 Authority Key Identifier 分別如下：

X509v3 Subject Key Identifier: 
    43:09:93:40:FA:11:4B:30:33:EC:F2:87:6E:8D:71:18:CF:8A:BC:8E

 X509v3 Authority Key Identifier: 
    keyid:51:68:FF:90:AF:02:07:75:3C:CC:D9:65:64:62:A2:12:B8:59:72:3B

在 verify certificate chain 過程中，Facebook 的 Web Server憑證中的 Authority Key Identifier  必須要對應到 Intermediate CA憑證的 Subject Key Identifier 。而 Intermediate CA憑證的 
Authority Key Identifier 必須要對應到 Root CA 憑證的 Subject Key Identifier。

 而 Root CA憑證中的Authority Key Identifier 則是對應自己的Subject Key Identifier  。

最後，Certificate Chain 的存放順序必須是如下所示，Root CA一定是放在最下方，再依據簽發的順序置放：

 -----BEGIN CERTIFICATE-----
Server certificate
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
Intermediate certificate
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
Root CA's certificate
-----END CERTIFICATE-----

Reference:
[1] Standard X.509 V3 Certificate Extensions
[2] Check Certificate Chain
[3] Creating a .pem File for SSL Certificate Installations
[4] CA建置工具：Openssl的管理與使用介紹（上）
[5] How to create SSL X.509 Certificate ?
[6] OpenSSL Cookbook

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