DCB SM-56 Manuel utilisateur

SM-56 Security Modem

Data Comm for Business, Inc.

PO Box 6329

Champaign, IL 61826-6329 July 7, 2009

(217) 897-6600 Firmware Version: 1.0

www.dcbnet.com

Table of Contents

PRODUCT DESCRIPTION............................................................................................... 4

CONFIGURATION EXAMPLES........................................................................................5

Setting Defaults and Protecting High S-Registers...................................................................... 5

Encrypted Connection................................................................................................................ 6

Configuring the Ethernet Interface.............................................................................................. 7

Dial-In User Authentication Example.......................................................................................... 8

One-Time Pass-Code Example.................................................................................................. 9

INTERFACE SPECIFICATION....................................................................................... 10

RS-232 Interface...................................................................................................................... 10

Cables...................................................................................................................................... 10

SWITCHES AND INDICATORS......................................................................................11

DTE Baud Rate Configuration.................................................................................................. 11

Front Panel Indicators.............................................................................................................. 11

AT COMMANDS, S-REGISTERS, AND RESULT CODES............................................12

Introduction............................................................................................................................... 12

Escape Code Sequence +++.................................................................................................. 12

Remote Escape Code Sequence ---....................................................................................... 13

AT Command Summary........................................................................................................... 14

Generic Modem Control Commands........................................................................................ 17

Soft Reset and Restore Profile.............................................................................................................. 17

Identification........................................................................................................................................... 17

Country of Installation............................................................................................................................ 17

Restore Factory Configuration (Profile)................................................................................................. 18

Designate a Default Reset Profile......................................................................................................... 18

Store Current Configuration................................................................................................................... 18

Store Telephone Number...................................................................................................................... 18

Read/Modify S-Register......................................................................................................................... 19

DTE-Modem Interface Commands........................................................................................... 20

Command Echo..................................................................................................................................... 20

Quiet Result Code Control..................................................................................................................... 20

Result Code Form.................................................................................................................................. 20

Connect Message Control..................................................................................................................... 20

Extended Result Codes......................................................................................................................... 20

RLSD (DCD) Option.............................................................................................................................. 21

DTR (Data Terminal Ready) Option...................................................................................................... 22

Flow Control........................................................................................................................................... 22

RTS/CTS (Request to Send/Clear to Send) Option.............................................................................. 22

DSR (Data Set Ready) Override........................................................................................................... 22

Call Control Commands........................................................................................................... 23

Dial......................................................................................................................................................... 23

Set Tone Dial Default............................................................................................................................. 24

Set Pulse Dial Default............................................................................................................................ 24

Answer................................................................................................................................................... 24

Hang-up (Disconnect)............................................................................................................................ 24

Return to Online Data Mode.................................................................................................................. 25

Speaker Volume.................................................................................................................................... 25

Speaker Control..................................................................................................................................... 25

Select Guard Tone................................................................................................................................. 26

Select Pulse Dial Make/Break Ratio...................................................................................................... 26

Display Current Configuration and Stored Profiles............................................................................... 26

Display Last Connection Statistics........................................................................................................ 27

Display Ethernet Status......................................................................................................................... 28

Display DHCP Status............................................................................................................................. 28

Report Line Signal Level....................................................................................................................... 28

Report Line Signal Quality..................................................................................................................... 28

Modulation Control Commands................................................................................................ 29

Modulation Selection............................................................................................................................. 29

Enable/Disable Data Compression........................................................................................................ 30

Line Quality Monitor and Auto-Retrain.................................................................................................. 30

Select µ-Law or A-Law Codec Type...................................................................................................... 31

Communication Standard Setting – CCITT or Bell................................................................................ 31

Automode Enable.................................................................................................................................. 31

Connection Mode................................................................................................................................... 32

Security Commands................................................................................................................. 33

Enable/Disable User Authentication...................................................................................................... 33

Enable/Disable Alert Action................................................................................................................... 33

Set Alert Action...................................................................................................................................... 33

Set Dial-Back Message......................................................................................................................... 33

Enable/Disable Encryption.................................................................................................................... 34

Hide Encryption Key.............................................................................................................................. 34

Set Encryption Key................................................................................................................................ 34

Display Activity Log................................................................................................................................ 35

Clear Activity Log................................................................................................................................... 35

Display Usage Statistics........................................................................................................................ 35

Clear Usage Statistics........................................................................................................................... 35

Set Modem Name.................................................................................................................................. 35

Protect S-Registers 96 – 255 from &F command.................................................................................. 35

Enable/Disable One-time Pass-code Authentication............................................................................ 36

Generate One-time Pass-code List....................................................................................................... 36

Set Remote ESC Password.................................................................................................................. 36

Enable/Disable Telnet Authentication................................................................................................... 36

Set User................................................................................................................................................. 37

Ethernet Commands................................................................................................................. 38

Enable Ethernet Port............................................................................................................................. 38

Set IP Address....................................................................................................................................... 38

Set Subnet Mask................................................................................................................................... 38

Set Gateway Address............................................................................................................................ 38

Set DNS Address................................................................................................................................... 38

Ping host................................................................................................................................................ 39

Set Telnet Port....................................................................................................................................... 39

Maintenance Commands.......................................................................................................... 40

Firmware Upload................................................................................................................................... 40

S-Registers............................................................................................................................... 41

Result Codes............................................................................................................................ 49

WARRANTY AND REPAIR............................................................................................ 52

Product Description

Thank you for your purchase or interest in the DCB SM-56 modem. If you are taking the time to read this

introduction, you are probably still in the evaluation phase, trying to understand what the SM-56 is and

how it can be applied to your particular application. This introduction will describe the SM-56, discuss

where it is applicable and also where it is not applicable. It will try to explain some of the limitations so

that you can make an appropriate design decision.

The SM-56 is a special purpose modem designed to enhance the security of remote dial-in access. Many

of us still rely on using a modem, attached directly to the serial port of some device, to remotely access

and manage that device. Unfortunately, the device may have little or no security. Anyone who stumbles

across the phone number to the modem, could attempt to gain access. However, improving security in

the end-device may be impossible or prohibitively expensive. By shifting security to the modem, it is a

simple matter of replacing your current modem with an SM-56.

The SM-56 behaves very much like a typical modem. It responds to the AT command set and can

answer and originate calls. However, it has the ability to inject additional security methods before

allowing communication through to the end-device. These methods include user name and password

authentication, one-time pass-code authentication, dial-back, and encryption based authentication.

These features can be enabled manually in the modem, without any special configuration required by the

end-device.

Another feature of SM-56 is an Ethernet interface that can take the place of the RS-232 serial port.

Instead of dialing in and connecting to a device attached to the serial port, you can instead be connected

via Telnet to an Ethernet device. This would allow dial-in access to a device that only supports Telnet

access. It also supports a Telnet server which will allow you to Telnet to the modem for the purpose of

dialing out.

The SM-56 has the ability to log all incoming connections. If user authentication is enabled, it will keep

track of each user, the amount of time connected and the amount of data transferred. It will also log all

failed authentication attempts. It can even be configured to dial-out a special number in the event of

repeated failed authentication attempts, as a indication that an unauthorized user may be trying to break

in.

The SM-56 achieves this added functionality by taking a real v92 modem and inserting a CPU in the path

between the modem and serial or Ethernet interface. The CPU actually emulates a virtual modem on the

DTE side, then controls the real modem based on the commands received.

The SM-56 has several limitations due to its design. Fax and voice features, typically found in a v92

modem, can not be supported. Also, the SM-56 adds a large amount of latency to the data stream. It can

add as much as 70 milliseconds to the first character. For typical console type applications, this added

latency is not noticeable. However, if used in a SCADA polling application, it may be necessary to adjust

the polling rate to account for the additional delay.

Configuration Examples

Setting Defaults and Protecting High S-Registers

The SM-56 modem has a number of non-standard S-Registers which are used to hold the security and

Ethernet configuration. These S-Registers are all located in registers 96 and above. One of the problems in

using the SM-56 with software packages that automatically configure the modem is that the software

typically resets the modem to factory defaults using the &F, &F0, or &F1 command as a first step.

Additionally, the software may not have the ability to configure the non-standard features. To work around

this, the SM-56 has a feature where the high S-Registers are not modified by the &F, &F0, &F1 commands.

This allows the non-standard features to be configured and stored manually.

The following examples will step through configuring most of the non standard features. When dealing with

an SM-56 in an unknown state, it is best to first issue a factory reset that will reset all features. The following

commands show how to achieve this:

AT&F2 ; Proprietary factory reset command, resets all S-Registers

; and configuration items to factory defaults.

AT+P ; Protect high S-Registers

Encrypted Connection

The method used to encrypt a dial-up connection is proprietary to the SM-56. So, in order to

implement an encrypted connection, an SM-56 is required at each end. Once configuration is

complete, dial-out can be performed manually or under software control. The status LED on the front

of the modem will illuminate after the connection is established to indicate the modems are operating

in encrypted mode.

Answer End

AT+P0 ; Unprotect high S-Registers.

AT&F0 ; Load factory default profile 0.

ATS0= ; Answer on first ring.

AT+K= 23456789abcdef ; Set encryption key. Choose your own key or use

; AT+K! to generate a random key.

AT+E ; Enable encryption mode.

AT+P ; Protect high S-Registers.

AT+H ; Optional – hide key so that it can not be

; read from modem.

AT&W0 ; Store the configuration to user profile 0

AT&Y0 ; Select profile 0 as the power-up default

Originate End

AT+P0 ; Unprotect high S-Registers.

AT&F0 ; Load factory default profile 0.

AT+K= 23456789abcdef ; Set encryption key. Must match answer key.

AT+E ; Enable Encryption Mode

AT+P ; Protect high S-Registers.

AT+H ; Optional – hide key so that it can not be

; read from modem.

AT&W0 ; Store the configuration to user profile 0

AT&Y0 ; Select profile 0 as the power-up default

ATD<phone_number> ; Dial remote modem – once connected, all data

; will be encrypted. Status LED will illuminate

; to indicate encrypted connection.

Configuring the Ethernet Interface

This example will show how to configure the Ethernet Interface with a static IP address. The default IP

address is 192.168.0.11.

AT+IP= 92. 68.0.25 ; Set the IP address to 92. 68.0.25

AT+SM=255.255.255.0 ; Set the subnet mask to 255.255.255.0

AT+GW= 92. 68.0. ; Optional, set default gateway address to

; 92. 68.0. If no gateway is present, set

; the gateway to 0.0.0.0

AT+DNS= 92. 68.0. ; Optional, set DNS server address to

; 92. 68.0. If no DNS server is present,

; set dns to 0.0.0.0

AT+N ; Enable the Ethernet Interface

AT&W0 ; Save the configuration to profile 0.

AT&Y0 ; Select profile 0 as power-up default

AT+P ; Optional, protect the high S-Registers,

; where the IP configuration is stored, from

; future &f0 and &f commands.

To verify and test the IP configuration:

AT&V3 ; Display Network Status

AT+PING= 92. 68.0. ; Attempt to ping a host.

Dial-In User Authentication E ample

This example will show how to configure 4 dial-in users, each showing a different type of action.

Upon dialing in, the user will be prompted for a user name and password. Upon successful

authentication, the indicated action will be performed.

AT&F2 ; Load factory defaults and clear user table.

; Note: if you are building upon another

; configuration you will not want to do &f2

ATS0= ; Answer on first ring.

AT+A ; Enable user-authentication mode.

AT+P ; Protect high S-Registers.

AT&W0 ; Store the configuration to user profile 0

AT&Y0 ; Select profile 0 as the power-up default

AT+USER0=Fred,secret 23

; Name,Password

; Normal user, pass-through to serial port

AT+USER =Sally,pass456,dial 9,555- 234

; Name, Password,dial(back)<phone number>

; Modem will hangup and dial-back

AT+USER2=Bob,secret,telnet 92. 68.0.5 3000

; Name, Password,telnet <IP address> <port>

; Modem will telnet to 92. 68.0.5 port 3000

AT+USER3=TheBoss,password,admin

; Administrative user, modem will enter online

; command mode.

One-Time Pass-Code E ample

This example will show how to configure the modem for one-time pass-code authentication. The modem will

generate a list of 80 pass-codes. When a dial-in user connects to the modem, he will be prompted for one of

the pass-codes. The modem will use each pass-code only once.

AT&F0 ; Load factory defaults

ATS0= ; Answer on first ring.

AT+PA ; Enable pass-code authentication mode.

AT+P ; Protect high S-Registers.

AT&W0 ; Store the configuration to user profile 0

AT&Y0 ; Select profile 0 as the power-up default

AT+PCODE ; Generate the pass-codes. The modem will only

; display the list once. Capture and store

; the list to a file for later reference.

; To generate a new list, repeat the command.

Interface Specification

RS-232 Interface

Pin Signal Direction

1 DTR input

2 Tx Data input

3 Rx Data output

4 RLSD (DCD) output

5 GND

6 Not used

7 CTS output

8 RTS input

9 Not used

Cables

Cables to provide a standard 25 pin or 9 pin DCE interface are included with the modem. Connect

the PC Direct adapter to the modem and use the patch cord and Remote PC adapters to connect to

the DTE device.

To connect a PC to the serial interface for initial configuration, use the two 9-pin adapters and a patch

cord.

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