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 mainte-
       nance 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 set-
       tings (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) be-
       haviour 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 nec-
       essary  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 invo-
       cations	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	 vari-
       ant 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 configu-
       rations 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
	      inherits 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 local-
       host 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  transac-
       tions 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  versions,
       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)