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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  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 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 transactions 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