Property:Telnet

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BoxMatrix >> Lexicon >> Network-Protocols >> Telnet

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Protocol

Protocol:	Telnet	Wiki	Freetz	IPPF	whmf	AVM	Web
Short for:	Teletype Network
Location:	Lexicon >> Network-Protocols
Weblinks:	Wikipedia.int  -  Wikipedia.de   -  RFC-15   -  RFC-854   -  RFC-855
Description:	Older remote shell protocol

Goto:   FRITZ!OS   -   Pseudo-Update  -  Telephone  -  Phonebook  -  TR-069  -  Shellinabox  -  SMW-Browser

Details

Telnet is is old unsecure remote shell protocol (1969, extended 1983) using Port-23-tcp.
It is deprecated and replaced by the secure SSH protocol.

FRITZ!OS

AVM uses Telnet for diagnosis and debugging of FRITZ!OS since fw 1.120.

The server is telnetd which is part of the busybox executable.

Pseudo-Update

The oldest method (2005-01-19) which works with all models which accept unsigned firmware is from Enrik Berkhan:

• starttelnet.image

It is an uncompressed tar which could be "flashed" like a firmware image and contains this install script:

#! /bin/sh

/usr/sbin/telnetd -l /sbin/ar7login

exit 0

This works on all older models which have the telnetd symlink and the applet built into busybox.
See the Model-Matrix of the telnetd (bbcmd). If no <bb> is listed in the Path column the applet is missing.
The telnetd applet is known to be missing for the 2170, 3131, 3170, and in newer fw for the 5140.
The symlink is known to be missing on the 7369 and all cable models and all firmware since 6.25.

Signed firmware was introduced in fw 4.03, see the Model-Matrix of the avm_firmware_public_key1.
Unsigned firmware was accepted as long as update_not_signed.html was built into the firmware.

Telephone

For all models which have the telefon daemon bultin telnetd can be started using special Dial-Codes.
#96*7* starts telnetd and #96*8* stops it again. This is persistent since telefon stores the setting in its config.

This only works with analog, ISDN or DECT telephones connected to the respective box but not with IP-Phones or Apps.
Same here, if the applet or the symlink is missing this method fails.

Phonebook

If you do not have any telephone at hand you can use the phonebook method.
It requires the Click to Dial (german Wählhilfe) function to be enabled.

Then you create Phonebook entries for #96*7* and #96*8*.
Now you can click the respective numbers in the Phonebook to enable or disable telnetd.
Same here, if the applet or the symlink is missing this method fails.

TR-069

Today telnetd is still built into busybox for ISP or ARGO usage by TR-069 calling busybox telnetd.
But the user can not call this by any means with original firmware.

Shellinabox

For internal development AVM does not use telnetd any more but shellinaboxd.
Unfortunately this is not used in Labor or Release firmware.

SMW-Browser

Property:Telnet

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