SNMPUSM(1)							     Net-SNMP								SNMPUSM(1)

NAME

       snmpusm - creates and maintains SNMPv3 users on a network entity

SYNOPSIS

       snmpusm [COMMON OPTIONS] create USER [CLONEFROM-USER]
       snmpusm [COMMON OPTIONS] delete USER
       snmpusm [COMMON OPTIONS] cloneFrom USER CLONEFROM-USER
       snmpusm [COMMON OPTIONS] [-Ca] [-Cx] passwd OLD-PASSPHRASE NEW-PASSPHRASE [USER]
       snmpusm [COMMON OPTIONS] <-Ca | -Cx> -Ck passwd OLD-KEY-OR-PASSPHRASE NEW-KEY-OR-PASSPHRASE [USER]
       snmpusm [COMMON OPTIONS] [-Ca] [-Cx] changekey [USER]

DESCRIPTION

       snmpusm	is  an SNMP application that can be used to do simple maintenance on the users known to an SNMP agent, by manipulating the agent's
       User-based Security Module (USM) table.	The user needs write access to the usmUserTable MIB table.  This  tool	can  be  used  to  create,
       delete, clone, and change the passphrase of users configured on a running SNMP agent.

OPTIONS

       Common options for all snmpusm commands:

       -CE ENGINE-ID
	      Set  usmUserEngineID  to	be  used  as  part of the index of the usmUserTable.  Default is to use the contextEngineID (set via -E or
	      probed) as the usmUserEngineID.

       -Cp STRING
	      Set the usmUserPublic value of the (new) user to the specified STRING.

       Options for the passwd and changekey commands:

       -Ca    Change the authentication key.

       -Cx    Change the privacy key.

       -Ck    Allows to use localized key (must start with 0x) instead of passphrase.  When this option is used, either the -Ca or -Cx option (but
	      not both) must also be used.

CREATING USERS

       An unauthenticated SNMPv3 user can be created using the command

	      snmpusm [OPTIONS] create USER

       This  constructs  an  (inactive)  entry in the usmUserTable, with no authentication or privacy settings.  In principle, this user should be
       useable for 'noAuthNoPriv' requests, but in practise the Net-SNMP agent will not allow such an entry to be made active.

       In order to activate this entry, it is necessary to "clone" an existing user, using the command

	      snmpusm [OPTIONS] cloneFrom USER CLONEFROM-USER

       The USER entry then inherits the same authentication and privacy settings (including pass phrases) as the CLONEFROM user.

       These two steps can be combined into one, by using the command

	      snmpusm [OPTIONS] create USER CLONEFROM-USER

       The two forms of the create sub-command require that the user being created does not already exist.   The  cloneFrom  sub-command  requires
       that the user being cloned to does already exist.

       Cloning	is  the only way to specify which authentication and privacy protocols to use for a given user, and it is only possible to do this
       once.  Subsequent attempts to reclone onto the same user will appear to succeed, but will be silently ignored.  This (somewhat  unexpected)
       behaviour  is mandated by the SNMPv3 USM specifications (RFC 3414).  To change the authentication and privacy settings for a given user, it
       is necessary to delete and recreate the user entry.  This is not necessary for simply changing the pass phrases (see  below).   This  means
       that  the  agent  must  be  initialized	with  at  least  one  user  for each combination of authentication and privacy protocols.  See the
       snmpd.conf(5) manual page for details of the createUser configuration directive.

DELETING USERS

       A user can be deleted from the usmUserTable using the command

	      snmpusm [OPTIONS] delete USER

CHANGING PASS PHRASES

       User profiles contain private keys that are never transmitted over the wire  in	clear  text  (regardless  of  whether  the  administration
       requests  are  encrypted or not).  To change the secret key for a user, it is necessary to specify the user's old passphrase as well as the
       new one.  This uses the command

	      snmpusm [OPTIONS] [-Ca] [-Cx] passwd OLD-PASSPHRASE NEW-PASSPHRASE [USER]

       After cloning a new user entry from the appropriate template, you should immediately change the new user's passphrase.

       If USER is not specified, this command will change the passphrase of the (SNMPv3) user issuing the command.  If the -Ca or -Cx options  are
       specified,  then only the authentication or privacy keys are changed.  If these options are not specified, then both the authentication and
       privacy keys are changed.

	      snmpusm [OPTIONS] [-Ca] [-Cx] changekey [USER]

       This command changes the key in a perfect-forward-secrecy compliant way through a diffie-helman exchange.  The remote  agent  must  support
       the  SNMP-USM-DH-OBJECTS-MIB for this command to work.  The resulting keys are printed to the console and may be then set in future command
       invocations using the --defAuthLocalizedKey and --defPrivLocalizedKey options or in your snmp.conf file using the  defAuthLocalizedKey  and
       defPrivLocalizedKey keywords.

       Note  that  since  these keys are randomly generated based on a diffie helman exchange, they are no longer derived from a more easily typed
       password.  They are, however, much more secure.

       To change from a localized key back to a password, the following variant of the passwd sub-command is used:

	      snmpusm [OPTIONS] <-Ca | -Cx> -Ck passwd OLD-KEY-OR-PASSPHRASE NEW-KEY-OR-PASSPHRASE [USER]

       Either the -Ca or the -Cx option must be specified.  The OLD-KEY-OR-PASSPHRASE and/or  NEW-KEY-OR-PASSPHRASE  arguments	can  either  be  a
       passphrase or a localized key starting with "0x", e.g. as printed out by the changekey sub-command.

EXAMPLES

       Let's assume for our examples that the following VACM and USM configurations lines were in the snmpd.conf file for a Net-SNMP agent.  These
       lines set up a default user called "initial" with the authentication passphrase "setup_passphrase" so that we can perform the initial setup
       of an agent:

	      # VACM configuration entries
	      rwuser initial
	      # lets add the new user we'll create too:
	      rwuser wes
	      # USM configuration entries
	      createUser initial MD5 setup_passphrase DES

       Note:  the  "initial"  user's setup should be removed after creating a real user that you grant administrative privileges to (like the user
       "wes" we'll be creating in this example.

       Note: passphrases must be 8 characters minimum in length.

   Create a new user
       snmpusm -v3 -u initial -n "" -l authNoPriv -a MD5 -A setup_passphrase localhost create wes initial

	      Creates a new user, here named "wes" using the user "initial" to do it.  "wes" is cloned from "initial" in the process, so he inher-
	      its that user's passphrase ("setup_passphrase").

   Change the user's passphrase
       snmpusm -v 3 -u wes -n "" -l authNoPriv -a MD5 -A setup_passphrase localhost passwd setup_passphrase new_passphrase

	      After  creating  the user "wes" with the same passphrase as the "initial" user, we need to change his passphrase for him.  The above
	      command changes it from "setup_passphrase", which was inherited from the initial user, to "new_passphrase".

   Test the new user
       snmpget -v 3 -u wes -n "" -l authNoPriv -a MD5 -A new_passphrase localhost sysUpTime.0

	      If the above commands were successful, this command should have properly performed an authenticated SNMPv3 GET request to the agent.

       Now, go remove the vacm "group" snmpd.conf entry for the "initial" user and you have a valid user 'wes' that you can use for future  trans-
       actions instead of initial.

WARNING

       Manipulating  the  usmUserTable using this command can only be done using SNMPv3.  This command will not work with the community-based ver-
       sions, even if they have write access to the table.

SEE ALSO

       snmpd.conf(5), snmp.conf(5), RFC 3414

4th Berkeley Distribution					    22 Oct 2005 							SNMPUSM(1)