Background

ServiceNow is a very popular IT Service Management solution that includes capabilities like workflow and approvals, asset management, discovery, orchestration and more.  This is the fourth article in the series.  We have covered  ServiceNow federation using Multi-provider SSO, setting-up automatic provisioning with the Centrify Identity Service App and setting-up and configuring Centrify App Request;  in this post we'll discuss the steps to set up Centrify Privilege Access Request to leverage the Service Catalog to request login or password checkout of resource accounts in Centrify Privilege Service.

 

About Centrify Privilege Service (CPS)

CPS is a privileged identity management solution that focuses on shared secrets on UNIX, Linux, Windows, Network devices, AD domains, Oracle or SQL databases and more.  The approach is different than Server Suite that is focused on the principle of least privilege.  Privilege Service provides a built-in access request system with single and multi-level approvals.

checkout.PNG

 

Privilege Service's Workflow  vs.  ServiceNow Self-Service

We often get questions about what solution to use for self-service and approvals for application or privilege requests.  The answer is quite simple:  if you already have all your requests in ServiceNow, you should continue to do so, this helps standardization and a unified user experience.  The Centrify workflow engine is designed to meet the basic needs for Centrify products and ServiceNow is a full-fledged Service Management solution.

 

We'll continue to use the Plan-Do (Implement)-Check (Test)-Adjust (Enhance) methodology and assumes you have working knowledge of Identity Service and ServiceNow.

 

What you'll need

  • A SaaS instance of Centrify Privilege Service with UNIX, Linux, Windows or Network Devices configured.
    Note:  You can use an on-premises instance as well, provided that the network (e.g. publicly-facing) and name resolution (publicly-resolvable) aspects of the design are taken care of.
  • A ServiceNow Instance that allows you to install apps  (non-developer) with federated access to your Privilege Service instance.  For details on how to set up SAML federation with the Multi-provider SSO, click here or review the links below.
  • Administrative accounts on both systems

 

Planning

During planning, discuss with your infrastructure, operations and security teams about these topics:

  • Will you have a single approval or multiple approval groups per resource?
    Depending on the resource(s) in question you may have a single group or multiple groups approve.  You may also use a default approval group. 
  • How will the workflow be designed?
    This topic is very organization-dependent.  Some organizations may chose to have automatic approvals for certain systems and human approvals when the systems host sensitive data or are subject to strong security policy or regulations like SOx, PCI, HIPAA and others.
  • Have you identified a Default Approval Group in ServiceNow?
    If you chose to have a single group approve all privileged requests.
  • Have you created a CIS role and policy set for the servicenow service account?
    The servicenow account in Identity Service requires at a minimum the "Privilege Management" right, in addition, a policy that allows for username/password is required since the REST calls used by the app can't answer multi-factor authentication requests.
  • Will you have SLAs tied to your application requests?
    Although not in the scope of this post, SN offers a lot of flexibility when designing workflows including expiring worfkow requests when they are not approved within a defined duration.

 

Implementation

Overview

  • Create an Identity Service user (the service account that SN will use to authenticate and perform actions)
  • Create an Identity Service role with the minimum rights (the role that will be assigned to the service account)
  • Create an Identity Service Policy to allow user/password login
  • Download and Install Centrify Privilege Access Request app from the ServiceNow App Store
  • Configure the Centrify Privilege Access Request app

Create a Service Account

For this integration, you'll need a service account (you should know how to create users to follow this article).  To practice least privilege, this account needs to belong to a role with the Privilege Management right.   This is to be able grant login or password checkout rights on the accounts on each system.  Centrify Directory users are created under Admin Portal > Users

sn-create-serviceuser.png

When creating the user, be mindful of options that can cause an outage (like password expiration), and practice proper rotation and complexity based on your internal policy.

 

Create a Role with the minimum rights

To create a role, you have to go to the Admin Portal > Roles and Press Add role.  In the  members tab, add the newly-created account and in the Administrative rights tab, select the privilege management right.

 

privman.png 

Once completed, press the save button.

 

Create Policy to allow user/password login

This step may require you to create an Authentication profile that only asks for password (Admin Portal > Settings > Authentication > Authentication profiles).   The reason being is that Identity Service will (by default) ask for a step-up method for any unknown connections. 

 

  1. Log on to the Admin Portal with an administrative account
  2. Go to Policies > New Policy
  3. In Policy Settings, scroll down and select the "Specified roles" radio button
  4. Press Add and browse for the role created in the previous step.
  5. On the left pane expand User Security Policies > Login Authentication and select Yes to enable.
  6. Under default profile (used if no conditions matched) select your Auth profile that only challenges for password.
  7. Press Save
  8. In an incognito window for your browser, try to log in to the service with the newly-created account.  You should only be prompted for username and then password.

policy-summary.png

Important:  Make sure that the policy only applies to the members of the role created for this integration.

 

Download and Install the Privilege Access Request App from the ServiceNow Store

  1. Go to the ServiceNow app store and search for Centrify.
    priv-req.PNG
  2. Click on the Centrify Privileged Request App
  3. Click "Get" to make the Centrify Privileged Request app available for your ServiceNow instances.
  4. Go to the ServiceNow instance, select System Applications > Applications > Downloads to locate the app then click Install to install it.

Configure the Centrify Privileged Access Request app

There are three configuration tasks required.  Properties, API Sync and Accounts.  The third category is only needed if you are using individual groups as approvers for each resource's account.
Properties
  1. In the application pane (left) navigate to Centrify Privilege Request > Properties.  Populate these three fields
    Centrify Cloud Tenant URL:  the URL for your identity service tenant.  (e.g. https://your-tenant.my.centrify.com)
    Centrify Cloud Service Account: the account you created in previous steps
    Centrify Cloud Service Account Password:  the strong password you created for the user
    sn-app-access-conf1.png 
  2. Default Approval Group (Optional):  now you have a decision to make based on the planning above.  Populate the "Default Approval Group" if you decided to use a single ServiceNow group to approve all privilege requests.  You have to find the group in ServiceNow (System Security > Groups; find the group, right-click it and "Copy sys_id" and paste it on the Default Approval Group.  If you are planning to have approval groups per App, then you leave the field empty and press Save.

API Sync

  1. Go to Centrify Privilege Request > Customize API Sync
  2. Set the Active checkbox
  3. Select an appropriate interval based on your SLAs (e.g. 1 hour)
  4. Press Save and then Execute Now.
    api-sync.png
    This process will synchronize the Resources (systems) and accounts available in Privilege Service

Accounts
If you set up a "Default Approval Group" you can skip this part.  At this point you have to have a list of all the apps and the corresponding approval groups.  For example, the root account in the CentOS system called engcen7 will be approved by the Team Development Code Reviewers group included with the sample data of the ServiceNow instance and the canned workflow for software.

root-apprv.png 

 
Verification

To verify the functionality of the app, you'll have to run through the workflow of the apps (or independent apps) based on the approval group defined.  For example, in my scenario I chose to have independent approval groups.  My requester wants to checkout the "api-key" resource under the azure-rh1 resource and the self-service request is automatically approved based on existing ServiceNow rules.

 flow.png

 

Once the request is approved the app will provide the requester access to the type of request (login for SSH or RDP access) or checkout (for password reveal or clipboard copy).  In order to get access to the system or retrieve the password, the requester must switch over to privilege manager and find the system in the resources list or in their favorites.  For login they can use the PuTTY or web client and to check-out the password, they can use the system resource on privilege manager or the mobile app.

 

Documented Approvals

Security analysts and auditors may require reports of who has been requesting and approving apps, this is easily accessible using the service catalog requests or under the Centrify Privilege Request Access approvals or the Dashboard section.

requests.PNG

 

Improvements

Since this app focuses on ServiceNow approvals, the enhancements are around workflow design.  For example, you can have multi-approval groups, you can set timers for SLAs, etc.   However, there are other things that you can customize including the Dashboards and the appearance and location of the Centrify items in the Service Catalog.

helsinki.PNG 

Centrify & ServiceNow Resources

There are multiple resources available in the documentation and tech blogs:

Background

Regulatory frameworks have evolved to require documented evidence of approval for development or infrastructure-related change control.  These activities usually require the exercise of elevated privileges.  Some examples of these requirements and guidelines can be found on PCI DSS, SANS Critical Security controls, ISO 27001 and others:

  doc-approvals.png

 

Centrify DirectAuthorize and DirectAudit provide end-to-end, role-based access controls for UNIX, Linux and Windows, in addition it provides mechanisms for validation and tracking of changes via ticketing or request systems.

 

Requirements

We've had customers that have two categories of requirements:

  • Tracking activities related to a particular change control or approved request
    For example: We want to track all privileged activities related to a change control in my security operations dashboard.
    We covered this on this on the original dzdo validator article.  When privileges are elevated, entries in both syslog or DirectAuthorize get created automatically.
    Using Centrify-enhanced sudo:
    $ dzdo tail /var/log/messages
    Enter the change control ticket number:1255
    

    syslog:

    Nov  7 15:04:39 engcen6 dzcheck.sample[35173]: User "dwirth@centrify.vms" will run "/usr/bin/tail /var/log/messages" as "root" with ticket number "1255"
    
    DA Console:
    DirectAudit Analyzer - dzdo.validator event.jpg
  • Implementing controls to prevent unauthorized changes
    For example:  We want to make sure that any privilege elevation is only allowed with an approved request.
    This lab covers a basic lab setup to implement this requirement.

 

Lab Diagram

dzdo-validator-lab.png 

 

What you'll need:

  • Centrify Standard Edition and a Centrify Zone with some UNIX roles defined
  • An AD-joined UNIX or Linux  system in the Centrify zone
    The system should be able to reach the ServiceNow instance directly, via proxy or via ServiceNow MIDServer.
  • A DirectAuthorize role for UNIX
  • A ServiceNow instance (Fuji release minimum) and a shared credential or token to query existing requests
    Make sure that the credential only has the minimal rights (e.g. read-only) for your requests.
  • Optional:  Centrify Privilege Service (Saas or On-Prem) to vault the SN user's credential. 

 

Use Case

  1. Privileged user obtains a change control manager approval via ServiceNow workflow request.
    The request has a change control window.  (date/time range)
  2. During the request validity timeframe, the privileged user needs to perform activities (using Centrify-ehnanced sudo) and when the commands are issued, the SN request number has to be provided.
  3. The dzdo.validator script uses the ServiceNow Perl API to validate if the request is approved or not.
    Additional validations can be added like user, time-range, etc;  these won't be covered for blog brevity.
  4. If the request is a approved, the Centrify-enhanced sudo command is allowed to execute.  If not, the user is notified.

 

Implementation  Overview

  1. Install the ServiceNow Perl API
  2. Test ServiceNow Instance connectivity
  3. Optional:  Protect the shared credential using Privilege Service
  4. Modify one of the sample scripts to work with ServiceNow Requests
  5. Modify the dzdo.validator script to call the ServiceNow Perl API script
  6. Implement the dzdo.validator via parameter or GPO
  7. Test your results

 

Install the ServiceNow Perl API

The full instructions and requirements are here:  http://wiki.servicenow.com/index.php?title=Perl_API#gsc.tab=0

  1. Make sure you have the appropriate Perl plugins  (e.g. CentOS 6.x):
    SOAP::Lite  (e.g. yum install perl-SOAP-Lite)
    Crypt::SSLeay (e.g. yum install perl-Crypt-SSLeay)
    IO::Socket::SSL ( e.g. yum install perl-IO-Socket-SSL)
    File::Basename
    MIME::Types (e.g. yum install perl-MIME-Types)
    MIME::Type
    MIME::Base64
  2. Download the Servicenow Perl API  (link to 1.01 version) to your UNIX/Linux system
  3. Unzip the file in a new folder and run the following commands:
    ## create a new folder, download and unzip
    $ mkdir SN
    $ cd SN
    $ wget http://wiki.servicenow.com/images/e/e5/ServiceNow-Perl-API.zip
    $ unzip ServiceNoW-Perl-API.zip
    ## compile the files
    $ perl Makefile.PL $ make $ make test $ make install
    Follow the prompts, once you have all the ServiceNow Perl API libraries installed to use with your scripts.

 

Testing Connectivity with your ServiceNow Instance (Sample Script)

  1. Create a new file with these contents
    # This script retrieves all the requests from your servicenow instance
    # it is used to test connectivity.
    #!/usr/bin/perl -w
    use ServiceNow; use ServiceNow::Configuration;

    # This example uses Centrify Privilege Service's AAPM capability
    # by checking-out the password from the vault at runtime, we eliminate
    # the need to use a cleartext password in this script.
    # uses cgetaccount to check out the password for your-SN-user for 3 mins.
    # Alternatively you can enable OAuth and use Tokens (recommended)

    $SN_PASSWD = `cgetaccount -s -t 3 your-SN-user`; my $CONFIG = ServiceNow::Configuration->new(); $CONFIG->setSoapEndPoint("https://your-instance.service-now.com/"); $CONFIG->setUserName("your-SN-user"); $CONFIG->setUserPassword($SN_PASSWD); my $SN = ServiceNow->new($CONFIG); my @requests = $SN->queryRequestedItem(); my $count = scalar(@requests); print "Number of requests=" . $count . "\n"; foreach my $request (@requests) { print "Request number: $request->{'number'}\n"; print "Requested by: $request->{'sys_created_by'}\n"; print "Date Created: $request->{'sys_created_on'}\n"; print "Approval Status: $request->{'approval'}\n"; print "\n"

 2. To test the script, add the execution flag and run it

$ chmod +x checksn.sh
$ ./inc2.sh
Number of requests=34
Request number: RITM0000002
Requested by: fred.luddy
Date Created: 2016-05-02 18:15:39
Approval Status: requested

Request number: RITM0000004
Requested by: fred.luddy
Date Created: 2016-09-03 17:15:39
Approval Status: requested

Request number: RITM0000005
Requested by: fred.luddy
Date Created: 2016-05-22 19:15:43
Approval Status: requested
[output truncated]

Modify the Sample Script to work with Individual Ticket Numbers

To do this, you need to change the script to require arguments and check for usage.   The modified lines would look like this:

 

#!/usr/bin/perl -w

# You're checking for arguments here.  If there are no arguments
# show the usage and exit.  E.g.  checksn RTM00005

if (@ARGV)  {

# The previous program can go here.  Make sure you modify this line
# to look like this:

my @requests = $SN->queryRequestedItem({'number'=> $0})


}  else {
          print "USAGE:  checksn [ServiceNow Request ID]\n"
}
   

Note that there's no error logic for requests that are not found.  We're going to have to add this later.

 

Modify the dzdo.validator script to to use the ServiceNow Perl API script

 

Centrify provides a sample dzdo validator script called dzcheck.sample.  This script exists under /usr/share/centrifydc/bin.

With the author's limited scripting knowledge we were able to modify it to work this way:

 

  • Initialize the proper libraries and variables
  • Retrieve the password for the ServiceNow user (your-user) and store it in SN_PASSWD
  • Connect to ServiceNow instance
  • Prompt the user for a Change Control number
  • If the number is not found, log to syslog and the user will not be allowed to run the command
  • If the number is found but the status is not approved, log to syslog and the user will not be allowed to run the command
  • If the number is found and approved, log to syslog and allow the end user to run the command.

Note that additional error logic and checks can be added.

 

#!/bin/sh /usr/share/centrifydc/perl/run
# A modified demo for Centrify-enhanced sudo (dzdo) validator 
# Modified to work with ServiceNow Requests
use strict; use lib "../perl"; use lib '/usr/share/centrifydc/perl'; use CentrifyDC::Logger; use ServiceNow; use ServiceNow::Configuration;
# Use privilege service to retrieve SN shared account password
# Alternatively, you can modify the script to use an OAuth token
my $SN_PASSWD = `cgetaccount -s -t 3 your-user`; my $dzdo_user=$ENV{DZDO_USER}; my $dzdo_command=$ENV{DZDO_COMMAND}; my $dzdo_runasuser=$ENV{DZDO_RUNASUSER}; my $CONFIG = ServiceNow::Configuration->new(); $CONFIG->setSoapEndPoint("https://your-instance.service-now.com/"); $CONFIG->setUserName("your-user"); $CONFIG->setUserPassword($SN_PASSWD); my $SN = ServiceNow->new($CONFIG); my $logger = CentrifyDC::Logger->new('dzcheck'); printf STDERR "Enter the change control ticket number: "; my $user_input=<>; my @requests = $SN->queryRequestedItem({'number' => $user_input});
# Check if request(s) exist, if not, exit (1) if (scalar(@requests)==0) { system "adsendaudittrailevent", "-t", "tkt_id", "-i", "$user_input"; $logger->log('INFO', "Change control ticket number: %s", $user_input); $logger->log('INFO', "User \"%s\" will not be allowed to run \"%s\" as \"%s\" with ticket number (REASON:not found) \"%s\"", $dzdo_user, $dzdo_command, $dzdo_runasuser, $user_input); exit 1; }
foreach my $request (@requests) { my $req_status = $request->{'approval'}; # Exit if request is not in approved status if ($req_status ne "approved") { system "adsendaudittrailevent", "-t", "tkt_id", "-i", "$user_input"; $logger->log('INFO', "Change control ticket number: %s", $user_input); $logger->log('INFO', "User \"%s\" will not be allowed to run \"%s\" as \"%s\" with ticket number (REASON:not approved) \"%s\"", $dzdo_user, $dzdo_command, $dzdo_runasuser, $user_input,$req_status); exit 2; } }
# Run command and log if request is approved
system "adsendaudittrailevent", "-t", "tkt_id", "-i", "$user_input"; my $logger = CentrifyDC::Logger->new('dzcheck'); $logger->log('INFO', "Change control ticket number: %s", $user_input); $logger->log('INFO', "User \"%s\" will run \"%s\" as \"%s\" with ticket number \"%s\"", $dzdo_user, $dzdo_command, $dzdo_runasuser, $user_input); exit 0;

I've saved this script as dzcheck.snow in the same location.

 

Configure Centrify-enhanced sudo (dzdo) to use the ServiceNow Requests validator

  1. Open the /etc/centrifydc/centrifydc.conf file for editing
  2. Uncomment the dzdo.validator and set it to our scripts
    dzdo.validator: /usr/share/centrifydc/sbin/dzcheck.snow
  3.  Perform and adreload (or restart the agent)

 

Testing

We'll use a modified version of the sample script to check the requests for validity first, then we'll try to flush the cache using dzdo.

  1. Ticket does not exist  (ABC123)
    Request verification
    $ ./sncheck ABC123
    Request not found.
    $ dzdo adflush
    Enter the change control ticket number: ABC123
    Sorry, user dwirth is not allowed to execute '/usr/sbin/adflush' as root on engcen6.centrify.vms.
    
    # syslog contents
    Sep 20 18:00:52 engcen6 dzcheck.snow[35963]: Change control ticket number: ABC123
    Sep 20 18:00:52 engcen6 dzcheck.snow[35963]: User "dwirth@centrify.vms" will not be allowed to run "/usr/sbin/adflush" as "root" with ticket number (REASON:not found) "ABC123#012"
    Sep 20 18:00:52 engcen6 adclient[1526]: INFO  AUDIT_TRAIL|Centrify Suite|dzdo|1.0|1|dzdo denied|5|user=dwirth(type:ad,dwirth@CENTRIFY.VMS) pid=35961 utc=1474412452436 centrifyEventID=30001 status=DENIED service=dzdo command=/usr/sbin/adflush runas=root reason=Dzdo Validator checks failed. Do not permit to continue the privileged command.
  2. Ticket is not approved (RITM0010022)
    Request verification:
    $ ./sncheck RITM0010022
    number of requests=1
    Request number: RITM0010022
    Requested by: robertson.pimentel
    Date Created: 2016-09-16 16:55:06
    Approval Status: requested

    $ dzdo adflush
    Enter the change control ticket number: RITM0010022
    Sorry, user dwirth is not allowed to execute '/usr/sbin/adflush' as root on engcen6.centrify.vms.
    
    # syslog content
    Sep 20 18:03:04 engcen6 dzcheck.snow[36011]: Change control ticket number: RITM0010022
    Sep 20 18:03:04 engcen6 dzcheck.snow[36011]: User "dwirth@centrify.vms" will not be allowed to run "/usr/sbin/adflush" as "root" with ticket number (REASON:not approved) "RITM0010022#012"
    Sep 20 18:03:04 engcen6 adclient[1526]: INFO  AUDIT_TRAIL|Centrify Suite|dzdo|1.0|1|dzdo denied|5|user=dwirth(type:ad,dwirth@CENTRIFY.VMS) pid=36009 utc=1474412584884 centrifyEventID=30001 status=DENIED service=dzdo command=/usr/sbin/adflush runas=root reason=Dzdo Validator checks failed. Do not permit to continue the privileged command
  3. Ticket is approved (RITM001003)
    $ ./sncheck RITM0010003
    number of requests=1
    Request number: RITM0010003
    Requested by: diego.jimenez
    Date Created: 2016-09-11 14:57:57
    Approval Status: approved

    $ dzdo adflush
    Enter the change control ticket number: RITM0010003
    Demo Password:
    DNS cache flushed successfully.
    Authorization cache store flushed successfully.
    GC and DC caches expired successfully.
    The auditing service's name cache has been successfully flushed.
    The DirectAudit installation information cache has been successfully flushed.
    
    # syslog content Sep 20 18:06:22 engcen6 dzcheck.snow[36108]: Change control ticket number: RITM0010003 Sep 20 18:06:22 engcen6 dzcheck.snow[36108]: User "dwirth@centrify.vms" will run "/usr/sbin/adflush" as "root" with ticket number "RITM0010003#012" Sep 20 18:06:22 engcen6 adclient[1526]: INFO AUDIT_TRAIL|Centrify Suite|dzdo|1.0|0|dzdo granted|5|user=dwirth(type:ad,dwirth@CENTRIFY.VMS) pid=36106 utc=1474412782119 centrifyEventID=30000 status=GRANTED service=dzdo command=/usr/sbin/adflush runas=root role=UNIX Sysadmin/Global env=(none)

 

Benefits if you're using DirectAudit

If you have Enterprise Edition, DirectAudit's events will contain information about the Change Control and you can now search for all activity related to an individual change control number.

ben-da.png

 

Benefits if you're using the Centrify Splunk App

The Splunk App will display reports on the reasons why the privilege elevation failed.  You can also add alerts based on this to identify any privileged user trying to fish.

ben-splunk.png

 

Improvements

This is a lab blog post, therefore this is just a simple concept, but here are the improvements I'd make:

  • Use OAth tokens for ServiceNow instead of a shared credential
    http://wiki.servicenow.com/index.php?title=OAuth_Setup#gsc.tab=0
  • Compare the date of execution with the change control date range (we only did simple checks)
  • Provide better feedback to the user interactively
  • Allow the user to create a request if it's not in the system and notify the approver (cli-driven workflow)

 

Quick Overview Video

 Notes:  ServiceNow, PCI DSS, SANS and ISO 27001 logos are registered trademarks of their respective owners.

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