Grandstream Networks GAC2500 User manual

Grandstream Networks, Inc.
GAC2500
Audio Conference Phone for AndroidTM
Security Guide

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GAC2500 Security Guide
Table of Contents
OVERVIEW.....................................................................................................................3
WEB UI/SSH ACCESS ...................................................................................................4
GAC2500 Web UI Access ....................................................................................................................4
Web UI Access Protocols .....................................................................................................................4
User Login ............................................................................................................................................5
User Management Levels ....................................................................................................................6
SSH Access..........................................................................................................................................6
DEVICE CONTROL SECURITY .....................................................................................7
Configuration via Keypad Menu ...........................................................................................................7
Permission to Install/Uninstall Apps .....................................................................................................7
GUI Config Tool Settings ......................................................................................................................8
SECURITY FOR SIP ACCOUNTS AND CALLS ............................................................9
Protocols and Ports ..............................................................................................................................9
Anonymous/Unsolicited Calls Protection ........................................................................................... 11
SRTP ..................................................................................................................................................12
NETWORK SECURITY.................................................................................................13
VPN ....................................................................................................................................................13
802.1X ................................................................................................................................................13
Bluetooth ............................................................................................................................................14
SECURITY FOR GAC2500 SERVICES........................................................................15
Provisioning via Configuration File .....................................................................................................15
Firmware Upgrading ...........................................................................................................................17
TR-069................................................................................................................................................18
FTP Server .........................................................................................................................................18
ADB Service .......................................................................................................................................19
LDAP ..................................................................................................................................................19
Syslog.................................................................................................................................................20
SECURITY GUIDELINES FOR GAC2500 DEPLOYMENT ..........................................21

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GAC2500 Security Guide
Table of Figures
Figure 1: Web UI Access Settings.................................................................................................................4
Figure 2: GAC2500 Web UI Login ................................................................................................................5
Figure 3: GAC2500 Admin Password Change..............................................................................................5
Figure 5: Disable SSH Access on GAC2500 ................................................................................................6
Figure 6: Limit Access to Advanced Settings on LCD...................................................................................7
Figure 7: Cust File Provision Page ...............................................................................................................8
Figure 8: Configure TLS as SIP Transport ....................................................................................................9
Figure 9: SIP TLS Settings on GAC2500......................................................................................................9
Figure 10: Additional SIP TLS Settings .......................................................................................................10
Figure 11: Settings to Block Anonymous Call .............................................................................................11
Figure 12: Settings to Block Unwanted Calls..............................................................................................11
Figure 13: SRTP Settings ...........................................................................................................................12
Figure 14: VPN Settings..............................................................................................................................13
Figure 16: 802.1X Settings..........................................................................................................................14
Figure 17: 802.1X for GAC2500 Deployment .............................................................................................14
Figure 19: GAC2500 Config File Provisioning ............................................................................................15
Figure 20: Validate Certification Chain........................................................................................................16
Figure 21: Certificate Management.............................................................................................................16
Figure 22: GAC2500 Firmware Upgrade Configuration..............................................................................17
Figure 23: Validate Certification Chain........................................................................................................17
Figure 25: TR-069 Connection Settings Page ............................................................................................18
Figure 26: FTP Service On .........................................................................................................................19
Figure 27: Developer Mode Enabled ..........................................................................................................19
Figure 28: GAC2500 LDAP Settings...........................................................................................................20
Figure 29: Syslog Protocol ..........................................................................................................................20

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GAC2500 Security Guide
OVERVIEW
This document presents a summary of security measures, factors, and configurations that users are
recommended to consider when configuring and deploying the GAC2500.
Note: We recommend using the latest firmware for latest security patches.
The following sections are covered in this document:
•Web UI/SSH Access
Web UI access is protected by username/password and login timeout. Two-level user management is
configurable. SSH access is supported for mainly troubleshooting purpose and it’s recommended to disable
it in normal usage.
•Device Control Security
The GAC2500 has multiple ways to limit the use for network settings, apps, and other settings if not
necessary for the end user.
•Security for SIP Accounts and Calls
The SIP accounts use specific port for signaling and media stream transmission. It also offers configurable
options to block anonymous calls and unsolicited calls.
•Network Security
The GAC2500 supports VPN, 802.1X, Bluetooth. VPN secures remote connection and 802.1X provides
network access control. it’s recommended to turn off Bluetooth if not used.
•Security for GAC2500 Services
GAC2500 supports service such as HTTP/HTTPS/TFTP provisioning, TR-069, LDAP, as well as allows
ADB and FTP access. For provisioning, we recommend using HTTPS with username/password and using
password-protected XML file. For services such as ADB and FTP, we recommend disabling them if not
used to avoid potential port exposure.
•Deployment Guidelines for GAC2500
This section introduces protocols and ports used on GAC2500 and recommendations for routers/firewall
settings.
This document is subject to change without notice.
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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GAC2500 Security Guide
WEB UI/SSH ACCESS
GAC2500 Web UI Access
The GAC2500 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. With this, administrators can access and configure all available GAC2500
information and settings. It is critical to understand the security risks involved when placing the GAC2500
phone on public networks and it’s recommended not to do so.
Web UI Access Protocols
HTTP and HTTPS are supported to access the GAC2500 web UI and can be configured under web UI →
Maintenance → Security Settings. To secure transactions and prevent unauthorized access, it is highly
recommended to:
1. Use HTTPS instead of HTTP.
2. Avoid using well known port numbers such as 80 and 443.
Figure 1: Web UI Access Settings

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GAC2500 Security Guide
User Login
Username and password are required to log in the GAC2500 web UI.
Figure 2: GAC2500 Web UI Login
The factory default username is “admin” and the default password is “admin”. The GAC2500 web UI require
to change the default password at first time login.
Figure 3: GAC2500 Admin Password Change
To change the password for default user "admin", Press on Change Password in the highlighted upper
corner or navigate to Maintenance → Security Settings. The password length must between 6 and 32
characters. Strong password with a combination of numbers, uppercase letters, lowercase letters, and
special characters is always recommended for security purpose.

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GAC2500 Security Guide
User Management Levels
Two user privilege levels are currently supported:
•Admin
•User
Admin login has access to all of the GAC2500’s web UI pages and can execute all available operations.
User login has limited access to the web UI pages. With user login, the user is allowed to configure the
following settings:
•Call
•Contacts
•Account: Call Settings
•Advanced: MPK General Settings, MPK LCD Settings
•Maintenance: Network Settings, Time & Language, Security Settings, Device Manager
•Status: Account Status, Network Status, System Info
Even if user login can access certain web UI pages, it has less options compared to admin login.
It is recommended to keep admin login with administrator only. And end user should be provided with user-
level login only, if web UI access is needed.
SSH Access
The GAC2500 allows access via SSH for advanced troubleshooting purpose. This is usually not needed
unless the administrator or Grandstream support needs it for troubleshooting purpose. SSH access on
GAC2500 is enabled by default with port 22 used. It’s recommended to disable it for daily normal usage. If
SSH access needs to be enabled, changing the port to a different port other than the well-known port 22 is
a good practice.
Figure 4: Disable SSH Access on GAC2500

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GAC2500 Security Guide
DEVICE CONTROL SECURITY
From GAC2500 web UI → Maintenance → Security Settings. administrator can set whether the user can
use specific features:
Figure 5: Limit Access to Advanced Settings on LCD
Configuration via Keypad Menu
This option configures access for keypad Menu settings on the Settings interface of the phone. It is
recommended to use “Constraint Mode” for end users.
•Unrestricted:
Configure all settings on the LCD settings interface.
•Basic Settings Only:
Advanced Settings, Wireless & Network options will not be displayed in LCD settings menu.
•Constraint Mode:
The user is required to enter the correct admin password to access Wireless & Network options and
Advanced Settings.
Permission to Install/Uninstall Apps
This option configures the permission for users to install/uninstall 3rd party applications. “Unknown Sources”
setting is under LCD → Advanced Settings → General Settings. It is recommended to use “Not allow” if the
device is used at public properties.
•Allow:
The user can install/uninstall any 3rd party apps as needed.
•Require admin password:
The user needs to enter the correct admin password before he/she can install/uninstall 3rd party apps.
•Require admin password if the app source is unknown:
The user needs to enter the correct admin password only when installing apps from unknown source.
Admin password is also required when the user uninstalls the 3rd party apps.
•Not allow:
The user cannot install/uninstall third-party apps. Unknown sources setting is not available under this
mode.

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GAC2500 Security Guide
GUI Config Tool Settings
The GUI config tool is a tool designed to customize the GUI desktop layout as well as GUI configuration
for devices. Here is the link to download the GUI config tool:
http://www.grandstream.com/tools/gui_customization_tool_v3.9.0.zip
From there, the administrator can build a customized file to remove access for certain apps and task bar
features. The tool would generate a file “GAC2500cust” which should be uploaded to a HTTP/TFTP server.
Then the user needs to configure the server address as GUI Customization File URL under web UI →
Maintenance → Upgrade → Cust Config Server Path to download the file to GAC2500.
Figure 6: Cust File Provision Page
For more details, please refer to the guide:
http://www.grandstream.com/tools/gac2500_gui_customization_guide.pdf

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GAC2500 Security Guide
SECURITY FOR SIP ACCOUNTS AND CALLS
Protocols and Ports
By default, after factory reset, the SIP account 1 is active. Since the default local SIP port is 5060 for account
1, this allows user to make direct IP call even if the account is not registered to any PBX. If the user is not
using any account, it is recommended to uncheck the settings from web UI → Account → General Settings
→ Account Active to deactivate account 1.
Below are the ports/protocols used on GAC2500 SIP accounts. GAC2500 supports up to 6 SIP accounts.
•SIP transport protocol:
The GAC2500 supports SIP transport protocol “UDP” “TCP” and “TLS”. By default, it’s set to “UDP”.
It’s recommended to use “TLS” so the SIP signaling is encrypted. SIP transport protocol can be
configured per SIP account under web UI → Account → Account x → SIP Settings. When “TLS” is used,
we recommend using “sips” instead of “sip” for SIP URI scheme to ensure the entire SIP transaction is
secured instead of “best-effort”.
Figure 7: Configure TLS as SIP Transport
SIP TLS certificate, private key and password can be configured under GAC2500 web
UI→Maintenance → Security Settings → SIP TLS.
Figure 8: SIP TLS Settings on GAC2500

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GAC2500 Security Guide
When SIP TLS is used, the GAC2500 also offers additional configurations to check domain certificate
and validate certificate chain. These settings can be found under web UI → Account → Account x →
SIP Settings.
- Check Domain Certificate:
If enabled, the GAC2500 will check the domain certificate when TLS/TCP is used for SIP transport.
The default setting is “No”.
- Validate Certification Chain:
If enabled, the GAC2500 will validate server’s certification chain when TLS/TCP is used for SIP
transport. The default setting is “No”.
Figure 9: Additional SIP TLS Settings
•Local SIP port when using UDP/TCP:
Starting from 5060 for account 1, the port numbers increase by 2 for account x. For example, 5062 is
the default local SIP port for account 2, 5064 for account 3, etc. The local SIP port can be configured
under Account→SIP Settings for each SIP account.
•Local SIP port when using TLS:
The SIP TLS port is the UDP SIP port plus 1. For example, if account 1’s SIP port is 5060, its TLS port
would be 5061.

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GAC2500 Security Guide
•Local RTP port:
The default port value is 5004. The Local RTP port can be configured from web UI → Advanced Settings
→ General Settings. This parameter defines the local RTP-RTCP port pair used to listen and transmit.
If it is configured with X, in channel 0 the port X will be used for audio RTP message, the port X+1 for
audio RTCP message, the port X+2 for video RTP message and the port X+3 for video RTCP. In
Channel 1, each port number will be incremented by 4 for each message. This increment rule will apply
to other channels and other port numbers. By default, the Account 1 will use Channel 0, Account 2
Channel 1, Account 3 Channel 2, Account 4 Channel 3, and Account 5 Channel 4 and Account 6
Channel 5. If an account needs to establish multiple session simultaneously, the system will use the
ports in the next available channels. The valid range is from 1024 to 65400.
Anonymous/Unsolicited Calls Protection
If the user would like to have anonymous calls blocked, please go to GAC2500 web UI → Account →
Account x → Call Settings and enable option “Reject Anonymous call”. This will automatically block the SIP
call if the caller ID is anonymous.
Figure 10: Settings to Block Anonymous Call
Additionally, the GAC2500 has built-in mechanism that detects and stops the spam SIP calls from ringing
the phones. Please see below web UI → Account → Account x → Advanced Settings. It is recommended
to enable highlighted options to validate incoming SIP requests.
Figure 11: Settings to Block Unwanted Calls

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GAC2500 Security Guide
- Only Accept SIP Requests from Known Servers:
When set to “Yes”, the GAC2500 will answer the SIP request from saved servers and only the SIP
requests from saved servers will be accepted. The SIP requests from the unregistered server will be
rejected. The default setting is “No”.
- Check SIP User ID for Incoming INVITE:
This configures the GAC2500 to check the SIP User ID in the Request URI of the SIP INVITE message
from the remote party. If it doesn't match the phone's SIP User ID, the call will be rejected. The default
setting is “No”.
- Authenticate Incoming INVITE:
This configures the GAC2500 to authenticate the SIP INVITE message from the remote party. If set to
"Yes", the phone will challenge the incoming INVITE for authentication with SIP 401 Unauthorized
response. The default setting is "No".
- Validate incoming SIP messages:
Specifies if the phone system will check the incoming SIP messages caller ID and CSeq headers. If the
message does not include the headers, it will be rejected.
SRTP
To protect voice communication from eavesdropping, the GAC2500 phones support SRTP for media traffic
using AES 128&256. It is recommended to use SRTP if server supports it. SRTP can be configured in web
UI → Account → Codec Settings.
Figure 12: SRTP Settings
When SRTP Key Life Time parameter is enabled, during the SRTP call, the SRTP key will be valid within
231 SIP packets, and phone will renew the SRTP key after this limitation.

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GAC2500 Security Guide
NETWORK SECURITY
VPN
Users can add VPN using different protocols (PPTP, L2TP/IPSec PSK, L2TP/IPSec RSA, IPSec Xauth
PSK, IPSeXauth RSA and IPSec Hybrid RSA). VPN settings can be configured from GAC2500 LCD
Settings →Advanced settings →Wireless & network →VPN and Tap on "Add VPN file" to access
configuration page as shown below:
Figure 13: VPN Settings
802.1X
GAC2500 supports EAPOL where access to switchports can be controlled with identity/password and
certificate. By default, it is disabled. When it is enabled, there are 3 different mode for selection: EAP-MD5,
EAP-TLS and EAP-PEAP. Network administrators can set this up accordingly for media access control and
network security purpose.

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GAC2500 Security Guide
Figure 14: 802.1X Settings
Figure 15: 802.1X for GAC2500 Deployment
Bluetooth
GAC2500 supports Bluetooth for Bluetooth headset connection, file transferring and handsfree mode for
cell phones. By default, Bluetooth is disabled and it can be enabled from LCD. If there is no Bluetooth
device used with GAC2500, it’s recommended to turn off Bluetooth so it’s not discoverable by nearly
Bluetooth devices.

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GAC2500 Security Guide
SECURITY FOR GAC2500 SERVICES
Provisioning via Configuration File
GAC2500 supports downloading configuration file via HTTP/HTTPS/TFTP. Below figure shows the options
for config file provisioning.
Figure 16: GAC2500 Config File Provisioning
We recommend users to consider the following options for added security when deploying the GAC2500
with provisioning.
- Config Upgrade Via: HTTPS:
By default, HTTPS is selected. This is recommended so the traffic is encrypted while travelling through
the network.
- HTTP/HTTPS User Name and Password:
This can be set up as required on the provisioning server when HTTP/HTTPS is used. Only when the
GAC2500 has the correct username and password configured, it can be authenticated by the
provisioning server and the config file can be downloaded.
- Authenticate Config file:
This sets the GAC2500 to authenticate configuration file before applying it. When set to “Yes”, the
configuration file must include P value P1 with GAC2500’s administration password. If it is missed or
does not match the password, the GAC2500 will not apply the config file.

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GAC2500 Security Guide
- XML Config File Password:
The GAC2500 XML config file can be encrypted using OpenSSL. When it’s encrypted, the GAC2500
must supply the correct password in this field so it can decrypt XML configuration file after downloading
it. Then the configuration can be applied to the GAC2500. Please note this feature is supported on XML
config file instead of the binary config file. Therefore, it’s recommended to use XML config file format
and encrypt it with this feature.
- Validate Certificate Chain:
This configures whether to validate the server certificate when downloading the firmware/config file. If
set to "Yes", the phone will download the firmware/config file only from the legitimate server.
Figure 17: Validate Certification Chain
GAC2500 supports uploading CA certificate to validate the server certificate and this setting is under
GAC2500 web UI → System Settings → Security Settings.
Figure 18: Certificate Management

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GAC2500 Security Guide
Firmware Upgrading
Similar to configuration file provisioning, GAC2500 supports downloading firmware file via
HTTP/HTTPS/TFTP. The firmware file is encrypted and GAC2500 ensures only authentic, signed and
untampered firmware file can run. Here are the recommended settings for firmware downloading.
Figure 19: GAC2500 Firmware Upgrade Configuration
- Firmware Upgrade Mode: HTTPS.
HTTPS is recommended so the traffic is encrypted while travelling through the network.
- HTTP/HTTPS User Name and Password:
This can be set up as required on the provisioning server when HTTP/HTTPS is used. Only when the
GAC2500 has the correct username and password configured, it can be authenticated by the firmware
server and the firmware file will be downloaded.
- Validate Certificate Chain:
This configures whether to validate the server certificate when downloading the firmware/config file. If
set to "Yes", the phone will download the firmware/config file only from the legitimate server.
Figure 20: Validate Certification Chain
GAC2500 supports uploading CA certificate to validate the server certificate and this setting is under
GAC2500 web UI→System Settings→Security Settings.

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GAC2500 Security Guide
TR-069
TR-069 is enabled by default, which means the connection request port 86400 is open for TR-069 session.
If the user does not need TR-069 service, it’s recommended to disable it. When TR-069 is enabled and the
service is to be used, users can also consider using a different connection request port other than the well-
known port 86400 for security purpose.
Figure 21: TR-069 Connection Settings Page
FTP Server
FTP server is disabled by default on GAC2500. It can be enabled from LCD menu→ app. FTP service
on GAC2500 uses port 2121. After the user enables FTP server on GAC2500 and connects to it, users can
browse the GAC2500 files such as screenshots from a remote PC. It is recommended to disable the FTP
server during normal usage, and only turn it on for specific purpose. After the file is retrieved, please disable
the FTP server.

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GAC2500 Security Guide
Figure 22: FTP Service On
ADB Service
Android Debug Bridge (ADB) is a versatile command-line tool that allows users to communicate with
GAC2500 for installing apps, debugging apps and running specific commands. To enable ADB connection,
users must turn on developer mode under LCD system security menu first and accept the RSA key from
remote device to allow access. The port number used for ADB connection is 5555. It is not recommended
to enable developer mode if ADB connection is not needed.
Figure 23: Developer Mode Enabled
LDAP
GAC2500 supports LDAP to obtain enterprise contacts from LDAP server. It’s recommended to change the
default connection mode “LDAP” to “LDAPS” to protect and encrypt LDAP queries and responses using
SSL/TLS.