1SNMPUSM(1) Net-SNMP SNMPUSM(1)
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6 snmpusm - creates and maintains SNMPv3 users on a network entity
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9 snmpusm [COMMON OPTIONS] [-Cw] AGENT create USER [CLONEFROM-USER]
10 snmpusm [COMMON OPTIONS] AGENT delete USER
11 snmpusm [COMMON OPTIONS] AGENT cloneFrom USER CLONEFROM-USER
12 snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT passwd OLD-PASSPHRASE NEW-
13 PASSPHRASE [USER]
14 snmpusm [COMMON OPTIONS] <-Ca | -Cx> -Ck AGENT passwd OLD-KEY-OR-
15 PASSPHRASE NEW-KEY-OR-PASSPHRASE [USER]
16 snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT changekey [USER]
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20 snmpusm is an SNMP application that can be used to do simple mainte‐
21 nance on the users known to an SNMP agent, by manipulating the agent's
22 User-based Security Module (USM) table. The user needs write access to
23 the usmUserTable MIB table. This tool can be used to create, delete,
24 clone, and change the passphrase of users configured on a running SNMP
25 agent.
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29 Common options for all snmpusm commands:
30 -CE ENGINE-ID
32 Set usmUserEngineID to be used as part of the index of the
33 usmUserTable. Default is to use the contextEngineID (set via -E
34 or probed) as the usmUserEngineID.
35 -Cp STRING
37 Set the usmUserPublic value of the (new) user to the specified
38 STRING.
39 Options for the passwd and changekey commands:
41 -Ca Change the authentication key.
43 -Cx Change the privacy key.
45 -Ck Allows one to use localized key (must start with 0x) instead of
47 passphrase. When this option is used, either the -Ca or -Cx
48 option (but not both) must also be used.
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52 An unauthenticated SNMPv3 user can be created using the command
53 snmpusm [COMMON OPTIONS] AGENT create USER
55 This constructs an (inactive) entry in the usmUserTable, with no
57 authentication or privacy settings. In principle, this user should be
58 useable for 'noAuthNoPriv' requests, but in practise the Net-SNMP agent
59 will not allow such an entry to be made active. The user can be cre‐
60 ated via the createAndWait operation instead by using the -Ca flag.
61 This will prevent the user from being marked as active in any agent
62 until explicitly activated later via the activate command.
63 In order to activate this entry, it is necessary to "clone" an existing
66 user, using the command
67 snmpusm [COMMON OPTIONS] AGENT cloneFrom USER CLONEFROM-USER
69 The USER entry then inherits the same authentication and privacy set‐
71 tings (including pass phrases) as the CLONEFROM user.
72 These two steps can be combined into one, by using the command
75 snmpusm [COMMON OPTIONS] AGENT create USER CLONEFROM-USER
77 The two forms of the create sub-command require that the user being
80 created does not already exist. The cloneFrom sub-command requires
81 that the user being cloned to does already exist.
82 Cloning is the only way to specify which authentication and privacy
85 protocols to use for a given user, and it is only possible to do this
86 once. Subsequent attempts to reclone onto the same user will appear to
87 succeed, but will be silently ignored. This (somewhat unexpected) be‐
88 haviour is mandated by the SNMPv3 USM specifications (RFC 3414). To
89 change the authentication and privacy settings for a given user, it is
90 necessary to delete and recreate the user entry. This is not necessary
91 for simply changing the pass phrases (see below). This means that the
92 agent must be initialized with at least one user for each combination
93 of authentication and privacy protocols. See the snmpd.conf(5) manual
94 page for details of the createUser configuration directive.
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98 A user can be deleted from the usmUserTable using the command
99 snmpusm [COMMON OPTIONS] AGENT delete USER
101
104 User profiles contain private keys that are never transmitted over the
105 wire in clear text (regardless of whether the administration requests
106 are encrypted or not). To change the secret key for a user, it is nec‐
107 essary to specify the user's old passphrase as well as the new one.
108 This uses the command
109 snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT passwd OLD-PASSPHRASE
111 NEW-PASSPHRASE [USER]
112 After cloning a new user entry from the appropriate template, you
115 should immediately change the new user's passphrase.
116 If USER is not specified, this command will change the passphrase of
119 the (SNMPv3) user issuing the command. If the -Ca or -Cx options are
120 specified, then only the authentication or privacy keys are changed.
121 If these options are not specified, then both the authentication and
122 privacy keys are changed.
123 snmpusm [COMMON OPTIONS] [-Ca] [-Cx] AGENT changekey [USER]
126 This command changes the key in a perfect-forward-secrecy compliant way
129 through a diffie-helman exchange. The remote agent must support the
130 SNMP-USM-DH-OBJECTS-MIB for this command to work. The resulting keys
131 are printed to the console and may be then set in future command invo‐
132 cations using the --defAuthLocalizedKey and --defPrivLocalizedKey
133 options or in your snmp.conf file using the defAuthLocalizedKey and
134 defPrivLocalizedKey keywords.
135 Note that since these keys are randomly generated based on a diffie
138 helman exchange, they are no longer derived from a more easily typed
139 password. They are, however, much more secure.
140 To change from a localized key back to a password, the following vari‐
143 ant of the passwd sub-command is used:
144 snmpusm [COMMON OPTIONS] <-Ca | -Cx> -Ck AGENT passwd OLD-KEY-
147 OR-PASSPHRASE NEW-KEY-OR-PASSPHRASE [USER]
148 Either the -Ca or the -Cx option must be specified. The OLD-KEY-OR-
151 PASSPHRASE and/or NEW-KEY-OR-PASSPHRASE arguments can either be a
152 passphrase or a localized key starting with "0x", e.g. as printed out
153 by the changekey sub-command.
154 Note that snmpusm REQUIRES an argument specifying the agent to query
157 as described in the .I snmpcmd(1) manual page.
158
160 Let's assume for our examples that the following VACM and USM configu‐
161 rations lines were in the snmpd.conf file for a Net-SNMP agent. These
162 lines set up a default user called "initial" with the authentication
163 passphrase "setup_passphrase" so that we can perform the initial setup
164 of an agent:
165 # VACM configuration entries
167 rwuser initial
168 # lets add the new user we'll create too:
169 rwuser wes
170 # USM configuration entries
171 createUser initial MD5 setup_passphrase DES
172 Note: the "initial" user's setup should be removed after creating a
174 real user that you grant administrative privileges to (like the user
175 "wes" we'll be creating in this example.
176 Note: passphrases must be 8 characters minimum in length.
178 Create a new user
180 snmpusm -v3 -u initial -n "" -l authNoPriv -a MD5 -A setup_passphrase
181 localhost create wes initial
182 Creates a new user, here named "wes" using the user "initial" to
184 do it. "wes" is cloned from "initial" in the process, so he
185 inherits that user's passphrase ("setup_passphrase").
186 Change the user's passphrase
188 snmpusm -v 3 -u wes -n "" -l authNoPriv -a MD5 -A setup_passphrase
189 localhost passwd setup_passphrase new_passphrase
190 After creating the user "wes" with the same passphrase as the
192 "initial" user, we need to change his passphrase for him. The
193 above command changes it from "setup_passphrase", which was
194 inherited from the initial user, to "new_passphrase".
195 Test the new user
197 snmpget -v 3 -u wes -n "" -l authNoPriv -a MD5 -A new_passphrase local‐
198 host sysUpTime.0
199 If the above commands were successful, this command should have
201 properly performed an authenticated SNMPv3 GET request to the
202 agent.
203 Now, go remove the vacm "group" snmpd.conf entry for the "initial" user
205 and you have a valid user 'wes' that you can use for future transac‐
206 tions instead of initial.
207
210 Manipulating the usmUserTable using this command can only be done using
211 SNMPv3. This command will not work with the community-based versions,
212 even if they have write access to the table.
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216 snmpd.conf(5), snmp.conf(5), RFC 3414
217V5.8 11 Dec 2009 SNMPUSM(1)