Project VOLANS: How to set up Your own Certification Authority

:: How to set up Your own Certification Authority ::
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How to set up Your own Certification Authority

Some of the below information has been taken from:

SSL certificates Howto [*]
Book : Network Security with OpenSSL. [*]

The following steps will be of great help.

Download and install the openssl software: If you are on RH linux, just check if this software is installed using

[openvpn@mia openvpn]# rpm -qi openssl
Name        : openssl                      Relocations: (not relocateable)
Version     : 0.9.7a                            Vendor: Red Hat, Inc.
Release     : 5                             Build Date: Wed Mar 19 14:13:12 2003
Install Date: Tue Apr 29 12:15:45 2003      Build Host: daffy.perf.redhat.com
Group       : System Environment/Libraries   Source RPM: openssl-0.9.7a-5.src.rpm
Size        : 2608270                          License: BSDish
Signature   : DSA/SHA1, Fri Mar 28 19:30:55 2003, Key ID 219180cddb42a60e
Packager    : Red Hat, Inc. 
URL         : http://www.openssl.org/
Summary     : The OpenSSL toolkit.
Description :
The OpenSSL toolkit provides support for secure communications between
machines. OpenSSL includes a certificate management tool and shared
libraries which provide various cryptographic algorithms and
protocols.

(Most of the time it comes installed.. Most of the things that i have said below might be applicable to RH 9.0)

Openssl has a global configuration file that it uses. To find out the location of this file use
```
sshvpn@mia:~> openssl ca
Using configuration from /usr/share/ssl/openssl.cnf
---SNIP--
```
This file has some useful sections.. Take a look at it. Pretty much self explanatory. Let us now start making our own Certificate Authority.

Create the required directories first. You can create such directories anywhere.. I preferred to create my CA in /etc/CertAuth

mia#> cd /etc
mia#> mkdir CertAuth; cd CertAuth
mia#> mkdir certs; mkdir private
mia#> chmod 700 private
mia#> echo '01' > serial
mia#> touch index.txt

Copy the following file to /etc/CertAuth/openssl.cnf (You can even copy from /usr/share/ssl/openssl.cnf, and edit it to match the below)

#
# OpenSSL example configuration file.
#The original configuration file is in /usr/share/ssl/openssl.cnf
#
####################################################################
[ ca ]
default_ca      = CA_default            # The default ca section
####################################################################
[ CA_default ]
dir             = /etc/CertAuth         # Where everything is kept
certificate     = $dir/cacert.pem       # The CA certificate
database        = $dir/index.txt        # database index file.
new_certs_dir   = $dir/certs            # default place for new certs.
private_key     = $dir/private/cakey.pem# The private key
certs           = $dir/certs            # Where the issued certs are kept
serial          = $dir/serial           # The current serial number
crl_dir         = $dir/crl              # Where the issued crl are kept
default_days    = 700                   # how long to certify for
default_crl_days= 300                   # how long before next CRL
default_md      = md5                   # which md to use.
policy          = CertAuthCA_policy
x509_extensions = certificate_extensions        # The extentions to add to the cert

# For the CA policy
[ CertAuthCA_policy ]
commonName              = supplied
stateOrProvinceName     = supplied
countryName             = supplied
emailAddress            = supplied
organizationName        = supplied
organizationalUnitName  = optional

[ certificate_extensions ]
basicConstraints=CA:FALSE
####################################################################
[ req ]
default_bits            = 2048
default_keyfile         = /etc/CertAuth/private/cakey.pem
defualt_md              = md5
prompt                  = no
distinguished_name      = root_ca_distinguished_name
x509_extensions         = root_ca_extensions

[ root_ca_distinguished_name ]
commonName              = Certificate Authority Created by Shashank Khanvilkar
stateOrProvinceName     = Illinois
countryName             = US
emailAddress            = shashank@evl.uic.edu
organizationName        = Root Certification Authority

[ root_ca_extensions ]
basicConstraints        = CA:true

Set the environment variable OPENSSL_CONF You can put this variable permanently in the root's .tcshrc as
```
setenv OPENSSL /etc/CertAuth/openssl.cnf
 ------- OR -------
```
You can add the following on every openssl command line
```
-config /etc/CertAuth/openssl.cnf
```
I prefer the first method.
Create a root certificate: Use the follwing command:
```
mia#> openssl req -x509 -newkey rsa -out cacert.pem -outform PEM -days 10000
Generating a 2048 bit RSA private key
..........................................................................................+++
................................................................................................................+++
writing new private key to '/etc/CertAuth/private/cakey.pem'
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
-----
```
If you are not sure about the above command use man req and it will tell you about all the options. However a few things need to be clarified. The -x509 option is used to create a new certificate. While genrating a new certificate for oneself, it also generates a Private key (/etc/CertAuth/private/cakey.pem), encrypted by the passphrase and a publick key, which is placed at the bottom of cacert.pem. The "-days" option makes sure that the certificate will be valid for a very very long time.
cacert.pem must be distributed to all users.

View the root certificate, to make sure that you are using the right config file, and the certificate remains valid for a long time. NOTE: The actual cacert.pem file only contains the lines

However to read the contents of this certificate we need to issue the following command. U can see the Public key, and other details...The -text option prints out everything.. The -noout option prevents openssl from printing the contents of the cacert.pem file again. Some more specific options are

 -serial         - print serial number value
 -hash           - print hash value
 -subject        - print subject DN
 -issuer         - print issuer DN
 -email          - print email address(es)
 -startdate      - notBefore field
 -enddate        - notAfter field
 -purpose        - print out certificate purposes
 -dates          - both Before and After dates
 -modulus        - print the RSA key modulus
 -pubkey         - output the public key
 -fingerprint    - print the certificate fingerprint
 -alias          - output certificate alias

Below I have listed the CA certificate in a more readable format.

mia#> openssl x509 -in cacert.pem -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 0 (0x0)
        Signature Algorithm: md5WithRSAEncryption
        Issuer: CN=Certificate Authority Created by Shashank Khanvilkar, ST=Illinois, C=US/emailAddress=shashank@evl.uic.edu, O=Root Certification Authority
        Validity
            Not Before: May 15 22:33:41 2003 GMT
            Not After : Sep 30 22:33:41 2030 GMT
        Subject: CN=Certificate Authority Created by Shashank Khanvilkar, ST=Illinois, C=US/emailAddress=shashank@evl.uic.edu, O=Root Certification Authority
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (2048 bit)
                Modulus (2048 bit):
                    00:e3:a6:75:8f:52:f8:39:e3:79:3c:81:ec:24:76:
                    be:09:f0:80:87:22:9f:a3:b3:60:91:9f:37:73:cf:
                    f9:76:25:13:69:95:bc:c1:7a:7c:6a:d0:89:dd:4c:
                    b3:26:55:e7:87:95:52:96:54:3c:a5:d8:50:91:84:
                    12:53:9e:ab:e1:c1:86:74:68:c3:ce:c7:74:07:a1:
                    be:39:7b:80:99:40:0d:38:55:59:31:18:f9:00:b7:
                    2a:ba:8c:f3:69:40:8d:f1:60:9a:68:31:6c:cc:ff:
                    5a:b4:ab:42:db:67:c4:11:56:cd:6b:bd:f5:01:2e:
                    9f:e8:71:5b:0c:24:e9:3f:9e:07:28:81:28:84:eb:
                    79:ae:95:85:fb:e1:f6:b6:ff:35:bd:81:73:ad:c1:
                    52:30:32:0e:49:cd:44:16:eb:97:a5:06:6a:33:b0:
                    de:b9:6d:df:8e:5d:6e:a9:ab:3e:dc:de:eb:3a:c2:
                    ab:19:97:a1:96:0b:c7:3e:cc:30:e5:9b:10:d8:df:
                    00:07:fb:02:19:82:be:1a:24:07:98:46:05:4f:24:
                    78:da:44:0c:fa:4b:93:20:ab:31:6d:08:e2:8c:eb:
                    f5:82:94:09:04:c3:0d:ba:a0:5b:f7:a7:53:8f:71:
                    5f:6d:b0:47:8b:e4:a2:ce:bf:79:6e:5c:4c:8a:23:
                    63:85
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Basic Constraints: 
            CA:TRUE
    Signature Algorithm: md5WithRSAEncryption
        92:69:e7:3d:a8:a9:73:7a:f0:16:15:96:cf:69:1a:f6:14:e4:
        78:15:67:6d:a4:fb:85:3a:e7:ee:47:a6:24:b1:ab:10:80:06:
        15:40:e6:13:03:72:f6:55:d8:b7:fd:5c:7c:1c:31:bf:53:a1:
        82:fc:a7:9b:83:cc:f5:09:b9:ff:73:a5:07:2a:89:10:a3:f8:
        64:d0:3f:4f:6e:03:71:06:f2:af:5d:a0:8d:59:cd:5a:e1:08:
        bb:ca:15:c8:05:aa:6d:76:a6:89:d1:8b:6b:03:39:43:21:a4:
        be:21:95:54:33:5e:a7:71:8c:6a:81:c0:0b:91:83:70:32:5c:
        0c:96:1e:c8:71:ba:e7:22:b7:b7:fb:d0:40:8d:f9:62:bc:44:
        16:4e:37:1c:59:7a:a4:8d:29:db:c0:18:3a:f7:cc:89:03:f3:
        75:3b:af:ef:30:e8:4e:c8:d4:30:5a:65:5f:f4:47:04:d2:da:
        ac:a7:79:c1:b9:56:59:11:e7:f0:4a:86:f1:2e:05:a9:d2:fc:
        95:e2:e2:fb:61:dd:7d:bc:77:07:ba:4c:30:0e:46:b2:e6:0e:
        d7:07:4d:c6:9b:e3:79:5a:c0:32:08:33:c8:5e:ae:fa:df:3d:
        d5:08:38:b6:78:77:0a:e3:c9:a8:2f:9f:d0:c7:ad:53:8b:a5:
        77:12:ad:2c

Users generating a certificate request: Now we have a certificate authority. But some user who wants to get his certificate signed from us, has to generate a certificate request. I will assume that I am user "sshvpn". here are the list of commands that i will follow... Two files are created testkey.pem and testreq.pem

testkey.pem ==> private key generated for the user (protected by the pass phrase.. usually I will not provide a passphrase as i need to use this for automatic creation without user intervention. To do this, I have to provide the -nodes option on the command line.)
testreq.pem ==> request to be sent to the CA for being accepted.

Here goes..

sshvpn@mia:~> openssl req -newkey rsa:1024 -keyout testkey.pem -keyform PEM -out testreq.pem -outform PEM -nodes
Generating a 1024 bit RSA private key
.........................++++++
.++++++
writing new private key to 'testkey.pem'
-----
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) [GB]:US
State or Province Name (full name) [Berkshire]:Illinois
Locality Name (eg, city) [Newbury]:Chicago
Organization Name (eg, company) [My Company Ltd]:UIC
Organizational Unit Name (eg, section) []:ECE
Common Name (eg, your name or your server's hostname) []:Shashank Khanvilkar
Email Address []:skhanv1@uic.edu 

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:i am a good boy
An optional company name []: PRESS ENTER

We show below the testreq.pem file

sshvpn@mia:~> openssl req -in testreq.pem -text
Certificate Request:
    Data:
        Version: 0 (0x0)
        Subject: C=US, ST=Illinois, L=Chicago, O=UIC, OU=ECE, CN=Shashank Khanvilkar/emailAddress=skhanv1@uic.edu
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (1024 bit)
                Modulus (1024 bit):
                    00:b2:9b:8d:04:3c:21:54:6f:b1:99:9f:35:2b:79:
                    2b:72:cb:4c:4d:6a:fa:87:98:a3:dd:3c:fe:bd:c8:
                    38:42:f8:ef:c5:88:03:6e:0f:86:97:e2:51:bb:40:
                    f4:e8:95:f8:2b:2e:37:31:74:c1:ff:34:fd:5c:fe:
                    31:3b:ab:af:10:bf:9d:14:c0:41:99:6f:b7:44:af:
                    62:73:a9:da:d1:3b:01:9c:a2:06:80:e5:01:4d:ad:
                    ef:a1:0d:11:9f:64:6f:d0:c1:63:fe:44:f9:00:7a:
                    ff:a6:c0:8d:b4:56:05:d0:bf:73:92:aa:8c:71:da:
                    a4:a0:45:05:d0:37:db:af:85
                Exponent: 65537 (0x10001)
        Attributes:
            challengePassword        :i am a good boy
    Signature Algorithm: md5WithRSAEncryption
        a5:c1:6b:1d:fe:e6:3f:2a:ce:d7:b2:62:cd:1a:b7:d1:bc:9d:
        1b:c9:0b:f8:9b:c3:cf:71:72:b0:da:e8:d8:90:2a:ff:dd:64:
        3b:97:59:97:e8:a3:df:ba:9f:96:d8:4a:47:d8:0c:b4:f1:74:
        ee:aa:35:cf:67:d4:c1:0a:4c:af:fc:e7:c2:7e:1f:aa:5b:b5:
        8b:f9:ae:bd:e6:21:0e:af:09:b7:26:a6:71:4a:db:4a:d8:37:
        39:d5:28:96:b9:39:9f:39:ba:53:c7:df:30:e6:a4:37:ae:25:
        9e:69:21:a4:3a:ad:d6:88:05:d1:e1:8f:ad:a2:15:7f:46:83:
        78:12
-----BEGIN CERTIFICATE REQUEST-----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-----END CERTIFICATE REQUEST-----

Send the testreq.pem file as an attachment in email to the CA ... (or just copy it to /etc/CertAuth)

Issuing the certificate: The CA should verify that the certifiacte comes from the right person and issue it using the following command. It is recommended that u use the "-notext" and "-out testcert.cert" option. This will not print any output to stdout.. and make a copy of the certificate in the file testcert.cert in the current directory.. This way you will not have to search the certs/ directory for the new certifcate.

mia#> openssl ca -in testreq.pem -notext -out testcert.cert
Using configuration from /etc/CertAuth/openssl.cnf
Enter pass phrase for /etc/CertAuth/private/cakey.pem:secretcode
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'US'
stateOrProvinceName   :PRINTABLE:'Illinois'
localityName          :PRINTABLE:'Chicago'
organizationName      :PRINTABLE:'UIC'
organizationalUnitName:PRINTABLE:'ECE'
commonName            :PRINTABLE:'Shashank Khanvilkar'
emailAddress          :IA5STRING:'skhanv1@uic.edu'
Certificate is to be certified until Apr 14 22:54:31 2005 GMT (700 days)
Sign the certificate? [y/n]:y


1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

Return the signed certificate (testcert.cert, in our above example) to the owner.

The signed certifiate contains a lot of information. You can peek inside by using the following command:

[openvpn@mia certificates]# openssl x509 -in testcert.cert -text
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 7 (0x7)
        Signature Algorithm: md5WithRSAEncryption
        Issuer: CN=Certificate Authority Created by Shashank Khanvilkar, ST=Illinois, C=US/emailAddress=shashank@evl.uic.edu, O=Root Certification Authority
        Validity
            Not Before: Jun  4 18:26:30 2003 GMT
            Not After : May  4 18:26:30 2005 GMT
        Subject: CN=openvpn, ST=Illinois, C=US/emailAddress=openvpn@mia.ece.uic.edu, O=UIC, OU=ECE
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (1024 bit)
                Modulus (1024 bit):
                    00:b1:a3:76:cd:69:d0:dd:f4:d6:3b:bc:56:3c:95:
                    ad:3b:dd:92:0a:fe:9f:83:fa:ca:25:47:10:49:25:
                    e3:81:6f:4d:bf:18:c1:57:1d:e9:56:bd:fb:25:36:

                    0e:31:d0:be:71:2c:82:2d:e4:2b:20:5f:bf:2a:25:
                    ab:7d:c4:6e:43:8c:ce:b0:cd
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Basic Constraints: 
            CA:FALSE
    Signature Algorithm: md5WithRSAEncryption
        b8:e9:56:0d:36:0c:76:fc:1c:8e:77:7e:42:6d:5e:b6:98:ad:
        64:d1:ca:14:60:dc:92:9b:d5:60:59:11:82:99:15:4f:95:76:
        ab:72:58:8d:de:03:a4:fb:6d:1c:31:2c:17:16:21:fc:12:7e:
        22:7a:ae:27:72:af:29:f0:3c:39:aa:21:79:6b:53:8c:2d:b2:
        bf:fd:f4:1a:77:c3:99:4b:e3:c1:24:1f:41:71:54:8f:ee:ff:
        ce:b1:d9:06:db:8d:70:81:e4:4f:07:0c:05:93:5c:3d:74:9a:
        ad:be:33:52:5a:c9:5a:d7:67:5f:b2:7b:cd:b4:39:74:ef:99:
        ee:ac:85:49:27:4f:83:cb:16:14:7b:39:a2:f8:11:f1:4a:7e:
        a4:65:af:a6
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

A simple cat on testcert.cert will reveal:

[openvpn@mia]# cat testcert.cert 
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

I use this file testcert.cert for sending my certificates to my peer.

Revoking a certificates:I don't have much idea about revoking, but I know that i have to use the following two commands. The -keyfile and -cert option are not necessary if you have set the OPENSSL_CONF shell variable.

#openssl ca -gencrl -keyfile /etc/CertAuth/private/cakey.pem -cert /etc/CertAuth/cacert.pem -out my_crl.pem 
#openssl ca -revoke /etc/CertAuth/certs/bad_crt_file -keyfile /etc/CertAuth/private/cakey.pem -cert /etc/CertAuth/cacert.pem

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