Grandstream Networks UCM Series User manual

Grandstream Networks, Inc.
UCM series IP PBX
Security Manual

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UCM Security Manual
Table of Contents
OVERVIEW.....................................................................................................................4
WEB UI ACCESS ...........................................................................................................5
UCM HTTP Server Access ....................................................................................................................5
Protocol Type .........................................................................................................................................5
User Login..............................................................................................................................................6
Login Settings ........................................................................................................................................8
User Management Levels ......................................................................................................................9
EXTENSION SECURITY .............................................................................................. 11
SIP/IAX Password................................................................................................................................11
Strategy of IP Access Control .............................................................................................................. 11
Example: Local Subnet Only ........................................................................................................ 11
SRTP....................................................................................................................................................14
TRUNK SECURITY.......................................................................................................15
Outbound Rule Permissions ................................................................................................................15
Privilege Level ..............................................................................................................................15
Source Caller ID Filter ..................................................................................................................16
Password protection .....................................................................................................................16
PIN Groups ...................................................................................................................................17
IVR Dial Trunk......................................................................................................................................19
Allow Guest Calls.................................................................................................................................20
TLS ...............................................................................................................................21
FIREWALL....................................................................................................................23
Static Defense......................................................................................................................................23
Static Defense Example: Blocking TCP Connection from a Specific Host...................................24
Static Defense Example: Blocking SSH Connection to UCM ......................................................25
Dynamic Defense.................................................................................................................................28

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Fail2ban ...............................................................................................................................................28
AMI................................................................................................................................31

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Table of Figures
Figure 1: UCM6202 Web UI Login ................................................................................................................6
Figure 2: Default Random Password ............................................................................................................7
Figure 3: Login Settings ................................................................................................................................8
Figure 4: Creating Custom Privilege Levels................................................................................................10
Figure 5: Strategy – Local Subnet Only ......................................................................................................12
Figure 6: Registration Failed from Subnet Not Allowed for Registration ....................................................13
Figure 7: Registration Successful from Allowed Subnet .............................................................................13
Figure 8: Enabling SRTP ............................................................................................................................14
Figure 9: Outbound Rule Permissions ........................................................................................................15
Figure 10: Source Caller ID Filter ...............................................................................................................16
Figure 11: Password Protection ..................................................................................................................17
Figure 12: Adding PIN Groups ....................................................................................................................17
Figure 13: Outbound route with PIN group .................................................................................................18
Figure 15: IVR Dial Trunk............................................................................................................................19
Figure 16: PBX SettingsSIP SettingsTCP/TLS....................................................................................21
Figure 17: Firewall Rule Custom Configuration ..........................................................................................24
Figure 18: Static Defense Blocking Host 192.168.40.142 Using TCP Connection ....................................24
Figure 19: Host blocked by UCM ................................................................................................................25
Figure 20: UCM SSH Access ......................................................................................................................26
Figure 21: Block SSH Connection ..............................................................................................................27
Figure 22: Putty Setup for SSH Connection ...............................................................................................27
Figure 23: SSH Connection Blocked by UCM ............................................................................................28
Figure 24: Fail2Ban Default Configuration..................................................................................................29
Figure 25: Asterisk Service Fail2Ban setting ..............................................................................................30

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OVERVIEW
This document presents a summary of security concerns on UCM. It covers the security risks and related
configurations that users need to consider when deploying the UCM.
The following sections are covered in this document:
•Web UI access
Web UI is secured by user login and login timeout mechanism. Two-level user management is
configurable. Admin with limited access can be created by the default super administrator.
•Extension security
This includes SIP/IAX password for authentication, IP access control and SRTP.
•Trunk security
Trunk security is achieved mainly by setting the privilege level, configuring source caller ID filter to filter
out outbound call requests from unwanted source
•TLS
This is to secure the SIP signaling.
•Firewall mechanism
Three types of firewall mechanism can be configured to protect UCM against malicious attacks: Static
Defense, Dynamic Defense (UCM6510 and UCM6102/UCM6202/UCM6204/UCM6208 only) and
Fail2ban.
•AMI
Using AMI feature comes with security concerns for UCM administrators to consider.
This document is subject to change without notice. The latest electronic version of this document is available
for download here:
http://www.grandstream.com/support
Reproduction or transmittal of the entire or any part, in any form or by any means, electronic or print, for
any purpose without the express written permission of Grandstream Networks, Inc. is not permitted.

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WEB UI ACCESS
UCM HTTP Server Access
The UCM embedded web server responds to HTTP/HTTPS GET/POST requests. Embedded HTML pages
allow users to configure the device through a web browser such as Microsoft IE, Mozilla Firefox, Google
Chrome and etc. This is the most important tool to configure all the settings on the UCM. It’s also the
immediate interface for the administrator to access configurations, user status and all the system
information. Therefore, it’s crucial to understand that directly placing the UCM on public network could
expose the domain name / IP address of the UCM and pose serious security concerns.
Protocol Type
HTTP and HTTPS web access are supported to access the UCM web UI. It can be configured under web
UISettingsHTTP Server. The protocol type is also the protocol used for zero config when the endpoint
device downloads the config file from the UCM. Therefore, it’s recommended to use HTTPS instead of
HTTP to secure the transactions and prevent unauthorized access.
Note also that by default we are using HTTP/HTTPS ports that are different from the well know ports 80
and 443.
It is recommended to disable the option “Redirect From Port 80”.
Finally, users have the option to specify a list of UP to 10 IP addresses which will be allowed to access the
UCM web GUI, otherwise the connection will be refused for any IP address not figuring in the white list.
To add IPs to the whitelist, go under menu web UISettingsHTTP Server:
•Enable the option “Enable IP Address Whitelist”
•Enter the permitted IP(s) by specifying both the address and the Subnet mask.

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User Login
UCM web UI access is restricted by user login. Username and password are required when logging in to
web UI.
Figure 1: UCM6202 Web UI Login
The factory default value of “Username” is “admin” while the default random password can be found on the
sticker at the back of the unit.

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Note: Units manufactured starting January 2017 have a unique random password printed on the sticker.
Older units and UCM6100 series have default password “admin”.
Figure 2: Default Random Password
It is highly recommended to change the default password after login for the first time.
To change the password for the default user “admin”, go to web GUISettingsChange Password page.
The new password has to be at least 4 characters. The maximum length of the password is 30 characters.
The minimum requirement for the login password is as below if “Enable Strong Password” (on web GUI
PBXInternal OptionsGeneral) is turned on:
•Must contain numeric digit.
•Must contain at least one lowercase alphabet, uppercase alphabet or special character.
Strong password with a combination of numbers, lowercase alphabet characters, uppercase characters
and special characters is always recommended to protect your login.

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Login Settings
An authenticated user of the UCM web UI may log in the system and then leave the active session on a
terminal unattended without intentionally logging-off from the system. An adversary with access to the
terminal could then have access to the UCM, meaning all the configuration and status information could be
exposed and changed intentionally or unintentionally.
UCM provides protection from such vulnerability using login timeout. After the user logs in the UCM web UI,
the user will be automatically logged out after certain timeout. This timeout value can be specified under
UCM web GUIMaintenanceChange InformationLogin Settings page. In the case that the user doesn’t
make any operation on web GUI within the timeout period, the user will be logged out automatically and the
web UI will be redirected to the login page, requiring password to access the web pages.
If the login timeout period is set to a short enough time, the chances of an adversary gaining access to an
unattended terminal are significantly reduced. However, the timeout period cannot be too short that an
authenticated user becomes annoyed by frequent automatic logouts during normal use. Therefore, users
shall set it to a value according to actual usage and situation. The default value of login timeout is 10
minutes.
Along with the login timeout feature, the UCM supports also user banning upon unsuccessful login attempts
with the possibility to configure the maximum number of allowed failed login attempts as well as settings
the ban period as shown on the below figure.
Figure 3: Login Settings

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User Management Levels
On UCM, Four privilege levels for web UI users are supported:
•Super Admin: high priority.
•Admin: low priority.
•Custom level: custom priority.
•Consumer: Low Priority
Super administrator can access all pages on UCM web UI, change configuration for all options and execute
all the operations, while normal administrator created by super administrator has limited access. Normal
administrator can access all pages on UCM web UI except the following:
•MaintenanceUpgrade
•MaintenanceBackup
•MaintenanceCleaner
•MaintenanceReset/Reboot
•SettingsUser ManagementOperation Log
A “Super Admin” user with username “admin” is innately configured in the UCM at the factory setting. It is
the only allowed “Super Admin” account and cannot be deleted and changed. This super administrator
could create, edit and delete new user accounts with lower privileges “Admin”, “Custom” and “Consumer”.
Super Admin also has the authority to view operations done by all the users in web
GUIMaintenanceOperation Log where normal users with lower privilege level “Admin” don’t have
access.
If there are more than one PBX administrator required to manage the UCM in your enterprise, it’s highly
recommended for the super administrator to create lower privilege administrators in order to manage the
UCM together, instead of handing out super administrator password to all the other users who may need
access the UCM web UI. The super administrator can also monitor the operation log to keep a record as
well as ensure no abnormal operations done on the PBX.
While In case the super admin wants to assign some users specific privileges, the custom privilege user
level can be helpful by giving him access to one or more of the following items:
▪View Status Information
▪Manage Conferences
▪System Events
▪CDR Reports
▪CDR API
▪Wakeup Service

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To create a new custom privilege level, navigate to the web UI menu MaintenanceUser
ManagementCustom Privilege, the name the new custom user level and assign the desired modules as
shown on the figure below.
Figure 4: Creating Custom Privilege Levels
From the security perspective, this feature can be helpful by giving each person the level of access that
they just need, no more nor less.
The last user access level is the “Consumer” level, this is the default assigned one for user portal access
where each user can access the UCM portal using his/her extension number and password in order to
manage their own data and benefit from the value-added feature. This way normal users don’t have access
to configuration modules/items than can affect the whole system and cannot access to advanced
maintenance operations.

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EXTENSION SECURITY
SIP/IAX Password
When creating a new SIP/IAX extension, the UCM administrator is required to configure “SIP/IAX Password”
which will be used for account registration authentication.
If “Enable Random Password” (on web GUIPBX SettingsGeneral Settings) is enabled, “SIP/IAX
Password” is automatically filled with a randomly generated secure password when creating the extension
on the UCM.
If “Enable Strong Password” (on web GUI PBX SettingsGeneral Settings) is enabled, the password
must be alphanumeric which should contain numeric digit and at least one lower case alphabet or upper-
case alphabet, or special character.
It is recommended to use random password and strong password to reduce the chance that the password
being guessed or cracked out.
Strategy of IP Access Control
The UCM administrator could control what IP address(s) is allowed to register to a certain extension by
editing “strategy” option under extension configuration dialog“Media” tag. Make sure to configure the
“strategy” option to the smallest set to block registration attempts from anyone that doesn’t need to register
to the account.
The strategy options are:
•“Local Subnet Only”: allows register requests from local IPs only. By default, the local subnet where the
UCM is location is allowed. User could also add more local subnets where devices are allowed to
register to this extension.
•“A Specific IP Address”: allows register requests from one user specified IP only.
•“Allow All”: the registration address is the entire Internet which is least recommended.
Example: Local Subnet Only
1. Assuming there are multiple subnets within the office and the devices in all subnets can reach each
other. The network administrator would like to allow only devices in 192.168.40.x network to register to
this UCM.
2. Under UCM web UI extension dialog, configure “Local Subnet Only” for “Strategy” option and
192.168.40.0 for “Local Subnet”.

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Figure 5: Strategy – Local Subnet Only
3. Save and Apply changes.
Now if the SIP end device is in subnet other than 192.168.40.x, e.g., 172.18.31.x subnet, the UCM will not
allow registration using this extension. The following figure shows the SIP device IP address is 172.18.31.17.
The UCM on IP 192.168.40.171 replies 404 Not Found for the registration request.

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Figure 6: Registration Failed from Subnet Not Allowed for Registration
Once moving this device to 192.168.40.x subnet, registration will be successful. The following figure shows
the IP address for the same SIP end device is 192.168.40.190. The UCM on IP address 192.168.40.171
replies 200 OK for the registration request.
Figure 7: Registration Successful from Allowed Subnet

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SRTP
SRTP is supported on UCM to secure RTP audio stream during the call. By default, it’s disabled. To use it,
please configure under extension configuration dialog“Media” tab when creating/editing an extension. If
SRTP is enabled, RTP data flow will be encrypted.
Figure 8: Enabling SRTP
As shown above, users have two options while enabling SRTP under extension parameters:
▪Enabled and forced: On this case, the extension does support SRTP for secure audio and doesn’t
allow any calls without SRTP.
▪Enabled But Not Forced: The extension does support SRTP, but can allow negotiation to setup
calls without SRTP in case the other end doesn’t support it.

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TRUNK SECURITY
A potential risk for trunks is that unwanted users may gain the authority to make international or long-
distance calls. This will result in unexpected high charges before the UCM administrator notices this. Usually
this high cost is due to improper configurations on the UCM. Therefore, administrators must be extremely
cautious when configuring those trunks that will be charged by placing certain calls, for example, PSTN
trunks or SIP trunks with international call capability.
Outbound Rule Permissions
Four methods are supported on UCM to control outbound rule permissions and users can apply one of
them to the outbound rule.
1. Privilege Level
2. Enable Filter on Source Caller ID
3. Password protection
4. PIN groups
Please make sure to configure it to allow only the desired group of users to call from this route.
Figure 9: Outbound Rule Permissions
Privilege Level
On the UCM, the supported 4 privilege levels are “Internal”, “Local”, “National” and “International” from the
lowest to the highest. Outbound calls through trunk can be placed only if the permission level assigned to
the caller is higher or equal to the privilege level of the outbound rule. Outbound call requests from users
with privilege lower than the outbound rule will be rejected.

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Please configure the privilege for the outbound rule high enough to restrict the extensions allowed to call
external numbers via this trunk.
Source Caller ID Filter
Instead of using privilege level, UCM administrator could specify the extensions/extension groups that are
allowed to use the outbound rule. This can be done by selecting extension/extension groups or defining
pattern for the source caller ID in “Custom Dynamic Route” field. The extension allowed to make outbound
call will either need to be an extension in the selected list or match the defined pattern.
Figure 10: Source Caller ID Filter
Please specify the extension or the pattern here to the minimal set so that only the desired users can dial
out from this outbound route.
For detailed configuration instructions, please refer to MANAGING OUTBOUND ROUTE section in white
paper: How to manage inbound/outbound route on UCM6510/6100
Password protection
For even more security, users could protect the outbound rule with a password that will be requested by
the UCM from the callers in order to allow outbound calls. Users can set the password on each outbound
on the specified field as shown on the figure below.

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Figure 11: Password Protection
PIN Groups
In some cases, multiple users do share same phone (ex: phone on public mode with user login), and the
shared phone can be used to make outbound calls, the administrator on this case can set the outbound
rule protection mode to PIN groups where each user should enter his PIN code in order to be allowed to
make outbound calls through trunks. In order to set PIN group protection, the admin should follow below
steps:
1. Navigate on the web UI under Extension/TrunkOutbound RoutesPIN Groups
2. Click Add to create a new PIN group and enter the user names and passwords.
Figure 12: Adding PIN Groups

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3. Save and apply, then on your outbound routes you can select the created group and each time one
the PIN group members tries to make outbound call, he/she will be requested to enter their PIN
code as a security protection.
Figure 13: Outbound route with PIN group

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IVR Dial Trunk
When creating/editing an IVR, the administrator could decide whether to allow the calls entering the IVR to
make outbound calls through trunks by configuring “Dial Trunk” and “Permission”. If “Dial Trunk” option is
enabled, the caller calling into the IVR will be able to dial external numbers through a trunk if the IVR’S
permission is higher than or equal to the privilege of the trunk. The potential risk here is that unwanted
users may call into IVR and then dial external number. This could possibly generate expected high charges
especially if an IVR is configured as the destination of an inbound route of a PSTN trunk, in which case,
anyone can call into the IVR and then dial out to long distance or international calls.
Figure 14: IVR Dial Trunk
We recommend disabling “Dial Trunk” option unless the risk associated with it is clearly understood or the
PBX administrator intentionally configures it to do so for specific reasons. If it has to be enabled, please
configure the “permission” as secure as possible to restrict the authorized callers to be known users.
For more information about IVR permissions, please refer to IVR PERMISSION section in white paper:
How to manage inbound/outbound route on UCM6510/6100