SIERRA VIDEO SYSTEMS
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before the “K” command in the same command string as the “K” command. The password that is
set remains in effect until another “K” command is received from the same remote address.
It would be used to establish a password for a remote address, to be used for such things as
locking and unlocking outputs and modifying the router configuration. When the router receives a
protected command (one which requires use of a password) from a remote address, it compares
the current password for that remote address with the password required to execute the protected
command. Protected commands consist of many of the “G” commands that change router
configuration, as well as
take
and
salvo trigger
commands when the output to be taken is locked.
In the former case, the administrator password is the one that must be sent in the “K” command
to permit the router configuration to be changed, while in the latter case the password that was
used to lock the output is the one that must be sent in the “K” command to permit the
take
to
occur.
Refer to the “B” command and the “G ADMIN_PASSWORD” command (in a separate document)
for more information.
For example, the command:
** M197 K1777 !!
requests that password 1777 be stored as the current password for remote address 197. The
command:
** M197 Y7,9 !!
requests that output 7 be connected to input 9, using the password stored for remote address 197
as the output lockout override password. The
take
will succeed if output 9 is either not locked or
is locked with password 1777. Otherwise, the
take
will fail.
“M”: Set Remote Address
The command "
M
" is followed by a remote address value, and it sets the remote address to be
used by all remaining commands in the current command string. This command is supported on
larger routers. It would be used when a client/server software system on a router control port
permits multiple remote users to send commands to the router through that control port. In such a
system, the server software that talks to the control port can insert an “M” command at the
beginning of each command string it sends to the router on behalf of its clients. The server would
assign a different address to each of its clients. The router uses the address to control access to
and modification of protected resources. The “M” command will typically work in conjunction with
the “K” command, which allows a password to be sent to the router. Some commands, such as
those that allow modification of router configuration settings, might require entry of an
administrator password before allowing the router configuration to be modified. The “K” command
is used to send the password, but the router must be able to record that password in association
with a particular remote user. The router would save the password as the one established by the
remote address specified in the “M” command. The examples below show how this would work.
If the “M” command is not present in a control string received on a serial port, the address
assigned to the
serial port itself
is used as the address for all commands in that command string.
The “M” command works on an honor system. There is nothing to keep a remote device from
forging a false address. This conforms with the philosophy of providing protection mechanisms
that are not designed to be totally hack-proof, but rather, are designed under the assumption that
controlling devices will honor the system. A dedicated hacker can always hack into the system if
he chooses. Note, however, that the server in a client/server relationship can provide a great deal
of added security for the system, forcing the correct “M” command to be sent each time, and
filtering out bogus “M” commands received from clients.
When the router receives an “M” command in a command string, it echoes the same “M”
command in its response. This allows the server connected to the serial port to parse the
received response string and determine to which client it should route the response.
