snmpusm(1) - man - phpman

SNMPUSM(1)                                    Net-SNMP                                    SNMPUSM(1)



NAME
       snmpusm - creates and maintains SNMPv3 users on a network entity

SYNOPSIS
       snmpusm [COMMON OPTIONS] [-Cw] AGENT create USER [CLONEFROM-USER]
       snmpusm [COMMON OPTIONS] AGENT delete USER
       snmpusm [COMMON OPTIONS] AGENT cloneFrom USER CLONEFROM-USER
       snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT passwd OLD-PASSPHRASE NEW-PASSPHRASE [USER]
       snmpusm  [COMMON  OPTIONS]  <-Ca  |  -Cx>  -Ck AGENT passwd OLD-KEY-OR-PASSPHRASE NEW-KEY-OR-
       PASSPHRASE [USER]
       snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT 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 one 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 [COMMON OPTIONS] AGENT 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
       created via the createAndWait operation instead by using the -Cw flag.  This will prevent the
       user  from being marked as active in any agent until explicitly activated later via the acti‐
       vate command.


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

              snmpusm [COMMON OPTIONS] AGENT 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 [COMMON OPTIONS] AGENT 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 authentica‐
       tion  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 authentica‐
       tion 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 [COMMON OPTIONS] AGENT 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  se‐
       cret  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 [COMMON OPTIONS] [-Ca] [-Cx] AGENT 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 issu‐
       ing 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 [COMMON OPTIONS] [-Ca] [-Cx] AGENT changekey [USER]


       This command changes the key in a perfect-forward-secrecy compliant way through a diffie-hel‐
       man  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 [COMMON OPTIONS] <-Ca | -Cx> -Ck AGENT 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.


       Note  that snmpusm REQUIRES  an argument specifying the agent to query as described in the .I
       snmpcmd(1) manual page.

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



V5.9.1                                       11 Dec 2009                                  SNMPUSM(1)