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snmpusm(1)                         Net-SNMP                         snmpusm(1)




NAME

       snmpusm - creates and maintains SNMPv3 users on a network entity


SYNOPSIS

       snmpusm [COMMON OPTIONS] [-Cw] 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.  The user can  be  cre-
       ated  via  the  createAndWait  operation instead by using the -Ca flag.
       This will prevent the user from being marked as  active  in  any  agent
       until explicitly activated later via the activate command.


       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



V5.6                              11 Dec 2009                       snmpusm(1)

Mac OS X 10.7 - Generated Wed Aug 10 15:23:37 CDT 2011
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