Wednesday, 8 November 2017

Configuring Dog Tag (PKI) Certificate Authority on Fedora

After trialling several web based CA's Dog Tag was one of the few CA's I found a reasonable amount of documentation for and has readily available packages for CentOS / Fedora.

Firstly let's install the package (it's not currently available in the stable repo yet):

sudo yum --enablerepo=updates-testing install dogtag-pki 389-ds-base

We will use 389 Directory Server to create a new LDAP server instance that Dogtag can use:

sudo setup-ds.pl --silent\
 General.FullMachineName=`hostname`\
 General.SuiteSpotUserID=nobody\
 General.SuiteSpotGroup=nobody\
 slapd.ServerPort=389\
 slapd.ServerIdentifier=pki-tomcat\
 slapd.Suffix=dc=example,dc=com\
 slapd.RootDN="cn=Directory Manager"\
 slapd.RootDNPwd=yourpassword

and then create our CA subsystem with:

sudo su -
pkispawn

Subsystem (CA/KRA/OCSP/TKS/TPS) [CA]: 

Tomcat:
  Instance [pki-tomcat]: 
  HTTP port [8080]: 
  Secure HTTP port [8443]: 
  AJP port [8009]: 
  Management port [8005]: 

Administrator:
  Username [caadmin]: 
  Password: 
  Verify password: 
  Import certificate (Yes/No) [N]? 
  Export certificate to [/root/.dogtag/pki-tomcat/ca_admin.cert]: 

Directory Server:
  Hostname [YOURVM.LOCAL]: 
  Use a secure LDAPS connection (Yes/No/Quit) [N]? 
  LDAP Port [389]: 
  Bind DN [cn=Directory Manager]: 
  Password: 
  Base DN [o=pki-tomcat-CA]: 

Security Domain:
  Name [LOCAL Security Domain]: 

Begin installation (Yes/No/Quit)? Y

Log file: /var/log/pki/pki-ca-spawn.20171108144208.log
Installing CA into /var/lib/pki/pki-tomcat.
Storing deployment configuration into /etc/sysconfig/pki/tomcat/pki-tomcat/ca/deployment.cfg.
Notice: Trust flag u is set automatically if the private key is present.
Created symlink /etc/systemd/system/multi-user.target.wants/pki-tomcatd.target → /usr/lib/systemd/system/pki-tomcatd.target.

    ==========================================================================
                                INSTALLATION SUMMARY
    ==========================================================================

      Administrator's username:             caadmin
      Administrator's PKCS #12 file:
            /root/.dogtag/pki-tomcat/ca_admin_cert.p12

      To check the status of the subsystem:
            systemctl status pki-tomcatd@pki-tomcat.service

      To restart the subsystem:
            systemctl restart pki-tomcatd@pki-tomcat.service

      The URL for the subsystem is:
            https://YOURVM.LOCAL:8443/ca

      PKI instances will be enabled upon system boot

    ==========================================================================

We can now either use the CLI or web-based interface to manage the server - however we will firstly need to ensure that the certificate we generated prior (/root/.dogtag/pki-tomcat/ca_admin.cert) is included in the Firefox certificate store:

Firefox >> Edit >> Preferences >> Advanced >> Certificates >> View Certificates >> 'Your Certificates' >> 'Import...'

Browse to the web ui: https://YOURVM.LOCAL:8443/ca

You should be presented with a certificate dialog like below:


End users can access the following URL in order to request certificates:

https://yourvm.local:8443/ca/ee/ca/

For this purposes of this tutorial we will keep things simple and generate a certificate for use on a Windows machine - so let's firstly select 'Manual Server Certificate Enrolment':

openssl genrsa -out computer.key 2048
openssl req -new -sha256 -key computer.key -out computer.csr

cat computer.csr

and paste the certificate in as below:


Hopefully then (after hitting submit) we'll see:

Now - let's head to the admin section and approve the request:

https://yourvm.local:8443/ca/agent/ca/

List Requests >> Find


Click on the request, check the details etc. and finally hit 'Approve' at the bottom.

Once it has been approved you should see a copy of the (BASE64 encoded) certificate at the bottom of the confirmation page.

Finally we'll want to package this up a long with the corresponding private key:

openssl pkcs12 -inkey computer.key -in computer.pem -export -out computer.pfx

(where 'computer.pem' is the public portion that has just been generated.)

Proceed by importing the PFX file into the Windows Computer certificate store under 'Personal'.

Sources

Fedora Project :: PKI :: Quick Start

Wednesday, 1 November 2017

Implementing 802.1X with a Cisco 2960, FreeRADIUS and Windows 7 / 10

802.1X: 802.1X allows you to securely authenticate devices connecting to a network - while often employed in wireless networks it is also often used along side wired ones as well. A typical transaction will involve the authenticator (the switch in this case) sending a EAP message to the supplicant (the client workstation in this case) and will then send back an EAP response.

For this lab we will be focusing on wired networks and will be attempting to address the problem of visiting employees from company A from plugging in their equipment into Company B's infrastructure.

To start we will need the following components:

- A client machine running Windows 7 / 10 (192.168.20.2/24)
- A Cisco 2960 switch with IOS > 15 (192.168.20.1/24)
- A linux box running FreeRadius (192.168.20.254/24)

Switch

So let's firstly look at the switch portion - we'll configure dot1x and radius on the switch:

conf t
aaa new-model

radius server dot1x-auth-serv
 address ipv4 192.168.20.2 auth-port 1812 acct-port 1813
 timeout 3
 key (7) <sharedkey>

aaa group server radius dot1x-auth
server name dot1x-auth-serv

aaa authentication dot1x default group dot1x-auth
aaa accounting dot1x default start-stop group dot1x-auth
aaa authorization network default group dot1x-auth

and proceed by enabling dot1x:

dot1x system-auth-control

and we'll then enable it on the relevant ports:

int range gi0/1-5
switchport mode access
authentication port-control auto
dot1x pae authenticator

FreeRADIUS Server

We'll continue on the server by installing radiusd:

sudo yum install freeradius

and then use samba to communicate with the domain:

sudo yum install samba samba-common samba-common-tools krb5-workstation openldap-clients policycoreutils-python

(We are not actually setting up a samba server - instead just using some of the tools that are provided with it!)

vi /etc/samba/smb.conf


[global]
        workgroup = <domain-name>
        security = user
        winbind use default domain = no
        password server = <ad-server>
        realm = <domain-name>
        #passdb backend = tdbsam


[homes]
        comment = Home Directories
        valid users = %S, %D%w%S
        browseable = No
        read only = No
        inherit acls = Yes

and then edit the kerberos configuration:

vi /etc/krb5.conf

 Configuration snippets may be placed in this directory as well
includedir /etc/krb5.conf.d/

[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
 dns_lookup_realm = false
 ticket_lifetime = 24h
 renew_lifetime = 7d
 forwardable = true
 rdns = false
 # default_realm = EXAMPLE.COM
 default_ccache_name = KEYRING:persistent:%{uid}

[realms]
 domain.com = {
  kdc = pdc.domain.com
 }

[domain_realm]
 .domain.com = DOMAIN.COM
 domain.com = DOMAIN.COM

and then modify NSS to ensure that it performs lookups using windbind:

vi /etc/nsswitch.conf

passwd:     files winbind
shadow:     files winbind
group:      files winbind
protocols:  files winbind
services:   files winbind
netgroup:   files winbind
automount:  files winbind

ensure samba starts on boot and restart the system:

sudo systemctl enable smb
sudo systemctl enable winbind
sudo shutdown -r now

Now join the domain with:

net join -U <admin-user>

and attempt to authenticate against a user with:

wbinfo -a <username>%<password>

should return something like:

Could not authenticate user user%pass with plaintext password
challenge/response password authentication succeeded

We also need to ensure NTLM authentication works (as this is what is used with FreeRadius):

ntlm_auth --request-nt-key --domain=<domain-name> --username=<username>

should return:

NT_STATUS_OK: Success (0x0)

(Providing the account is in good order e.g. not locked etc.)

The 'ntlm_auth' program needs access to the 'winbind_privileged' directory - so we should ensure that the user running the radius server is within the 'wbpriv' group:

usermod -a -G wbpriv radiusd

and then proceed to install and setup freeradius:

sudo yum install freeradius
sudo systemctl enable radiusd

mv /etc/raddb/clients.conf /etc/raddb/clients.conf.orig
vi /etc/raddb/clients.conf

and add the following:

client <switch-ip> {
        secret                = <secret-key>
        shortname             = <switch-ip>
        nastype               = cisco
}

We'll now configure mschap:

vi /etc/raddb/mods-enabled/mschap

and ensure the following is set:

with_ntdomain_hack = yes

ntlm_auth = "/usr/bin/ntlm_auth --request-nt-key --username=%{%{Stripped-User-Name}:-%{%{User-Name}:-None}} --challenge=%{%{mschap:Challenge}:-00} --nt-response=%{%{mschap:NT-Response}:-00}"

and the EAP configuration:

sudo vi /etc/raddb/mods-available/eap

Search for the following line:

tls-config tls-common

and uncomment:

random_file = /dev/urandom

Make sure your firewall is setup correctly:

sudo iptables -A INPUT -p udp -m state --state NEW -m udp --dport 1812 -j ACCEPT
sudo iptables -A INPUT -p udp -m state --state NEW -m udp --dport 1813 -j ACCEPT

and then test the configuration by running FreeRadius in test mode:

sudo radiusd -XXX

Then on the Windows 7 / 10 client workstation ensure that the 'Wired AutoConfig' service has been started (and has also been set to 'Automatic'.)

On the relevant NIC properties ensure that 'Enable 802.1X authentication' has been enabled:


Within Windows 10 you should not need to perform this - however it's always best to check the defaults just in case!

If you are not using a certificate ensure that the 'Verify the server's identity by validating the certificate' is unchecked as below (within the PEAP Settings):



Click 'Configure...' next to 'Secured password (EAP-MSCHAP v2) and ensure that 'Automatically use my Windows logon name and password' is ticked.

Finally hit 'OK' and back on the 'Authentication' tab - click on 'Additional settings...' and ensure 'Specify authentication mode' is ticked and is set to 'User authentication'.

We can now attempt to plug the client into the switch and with any luck we will obtain network access!


Sources

https://documentation.meraki.com/MS/Access_Control/Configuring_802.1X_Wired_Authentication_on_a_Windows_7_Client

http://wiki.freeradius.org/guide/freeradius-active-directory-integration-howto

Wednesday, 18 October 2017

SELinux: Adding a trusted directory into the httpd policy

By default on CentOS 7 / RHEL the '/var/www' directory is not permitted as part of the httpd policy - so instead we need to use semanage command in order to add this directory:

semanage fcontext -a -t httpd_sys_rw_content_t '/var/www/'

and then apply the context changes with:

restorecon -v /var/www/

you will also need to apply the context changes to any files within the directory as well e.g.:

restorecon -v /var/www/index.html

Thursday, 5 October 2017

Using Arachni Scanner with cookies / restricted areas

Below is a command line example I like to use with the Arachni Scanner - it allows you to use a session cookie (you can obtain from something like tamperdata) and ensures that specific URL's are not caled - for example logoff - which would (obviously) kill our session:

./arachni --http-cookie-string "cookie123" --scope-exclude-pattern logoff --scope-exclude-pattern login https://yourdomain.com/auth/restrictedarea/

Thursday, 28 September 2017

Python Example: Viewing members of a group with ldap3

Although the ldap3 module for python is well documented I didn't find many good examples - so I decided to publish this one for others:


from ldap3 import Server, Connection, ALL, NTLM, SUBTREE
import re
# Global varsBindUser = 'domain\\username'BindPassword = '<yourpassword>'SearchGroup = 'Domain Admins'ADServer = 'dc01.domain.tld'SearchBase = 'DC=domain,DC=tld'

def getUsersInGroup(username, password, group):
    server = Server(ADServer)
    conn = Connection(server, user=username, password=password, authentication=NTLM, auto_bind=True)
    conn.bind()

    conn.search(search_base=SearchBase,
                search_filter='(&(objectClass=GROUP)(cn=' + group +'))', search_scope=SUBTREE,
                attributes=['member'], size_limit=0)
    result = conn.entries

    conn.unbind()
    return result

def getUserDescription(username, password, userdn):
    server = Server(ADServer)
    conn = Connection(server, user=username, password=password, authentication=NTLM, auto_bind=True)
    conn.bind()

    conn.search(search_base=SearchBase,
                search_filter='(&(objectClass=person)(cn=' + userdn + '))', search_scope=SUBTREE,
                attributes=['description'], size_limit=0)
    result = conn.entries

    conn.unbind()
    return result

print('Querying group: ' + SearchGroup)

regex_short = r" +CN=([a-zA-Z ]+)" # extracts username onlyregex_long = r" +(?:[O|C|D][U|N|C]=[a-zA-Z ]+,?)+" # extracts complete DNmatches = re.findall(regex_short, str(getUsersInGroup(username=BindUser, password=BindPassword, group=SearchGroup)))

print('Found ' + str(len(matches)) + ' users associated with this group...')

for match in matches:
    print('Getting description for account: ' + match + '...')
    match_description = str(getUserDescription(username=BindUser, password=BindPassword, userdn=match))

    # check if user has a valid description    regex_desc = r"description:[ A-Za-z]+"    if re.search(regex_desc, match_description):
        print(re.search(regex_desc, match_description)

Wednesday, 27 September 2017

Tuesday, 26 September 2017

Changing a puppet master certificate

In the event you want to change a puppet server's hostname you will need to also generate a new certificate and re-issue a certificate to each of it's agents.

Firstly delete the existing certificate on the puppet master:

rm -Rf /etc/puppetlabs/puppet/ssl/

and on the puppetserver / CA issue:

sudo puppet cert destroy <puppetserver.tld>

and then on the puppetserver generate a new CA with:

puppet cert generate puppetserver.int --dns_alt_names=puppetserver,puppetdb

start the server:

puppet master --no-daemonize --debug

and on each puppet agent generate a new certificate - but firstly ensure existing old CA certs etc. have been removed.

Run the following on the master:

puppet cert clean client01

and the following on the client:

sudo service puppet stop
rm -Rf /etc/puppetlabs/puppet/ssl
rm -Rf /opt/puppetlabs/puppet/cache/client_data/catalog/client01.json
sudo service puppet start

puppet agent --test --dns_alt_names=puppetserver,puppetdb

And finally sign them on the puppet

puppet cert --list

puppet cert --allow-dns-alt-names sign puppetserver.int

puppet cert --allow-dns-alt-names sign puppetagent01.int

puppet cert --allow-dns-alt-names sign puppetagent02.int

and so on...

If you are using PuppetDB you will also need to ensure it's using the latest CA cert:

rm -Rf /etc/puppetlabs/puppetdb/ssl

puppetdb ssl-setup