SNMPVACM(1) Net-SNMP SNMPVACM(1)NAMEsnmpvacm - creates and maintains SNMPv3 View-based Access Control
entries on a network entity
SYNOPSISsnmpvacm [COMMON OPTIONS] createSec2Group MODEL SECURITYNAME GROUPNAME
snmpvacm [COMMON OPTIONS] deleteSec2Group MODEL SECURITYNAME
snmpvacm [COMMON OPTIONS] createView [-Ce] NAME SUBTREE MASK
snmpvacm [COMMON OPTIONS] deleteView NAME SUBTREE
snmpvacm [COMMON OPTIONS] createAccess GROUPNAME [CONTEXTPREFIX] MODEL
LEVEL CONTEXTMATCH READVIEW WRITEVIEW NOTIFYVIEW
snmpvacm [COMMON OPTIONS] deleteAccess GROUPNAME [CONTEXTPREFIX] MODEL
LEVEL
snmpvacm [COMMON OPTIONS] createAuth GROUPNAME [CONTEXTPREFIX] MODEL
LEVEL AUTHTYPE CONTEXTMATCH VIEW
snmpvacm [COMMON OPTIONS] deleteAuth GROUPNAME [CONTEXTPREFIX] MODEL
LEVEL AUTHTYPE
DESCRIPTIONsnmpvacm is an SNMP application that can be used to do simple mainte‐
nance on the View-based Control Module (VACM) tables of an SNMP agent.
The SNMPv3 VACM specifications (see RFC2575) define assorted tables to
specify groups of users, MIB views, and authorised access settings.
These snmpvacm commands effectively create or delete rows in the appro‐
priate one of these tables, and match the equivalent configure direc‐
tives which are documented in the snmpd.conf(5) man page.
A fuller explanation of how these operate can be found in the project
FAQ.
SUB-COMMANDS
createSec2Group MODEL SECURITYNAME GROUPNAME
Create an entry in the SNMPv3 security name to group table. This table
allows a single access control entry to be applied to a number of users
(or 'principals'), and is indexed by the security model and security
name values.
MODEL
An integer representing the security model, taking one of the
following values:
1 - reserved for SNMPv1
2 - reserved for SNMPv2c
3 - User-based Security Model (USM)
SECURITYNAME
A string representing the security name for a principal (repre‐
sented in a security-model-independent format). For USM-based
requests, the security name is the same as the username.
GROUPNAME
A string identifying the group that this entry (i.e. security
name/model pair) should belong to. This group name will then be
referenced in the access table (see createAccess below).
deleteSec2Group MODEL SECURITYNAME
Delete an entry from the SNMPv3 security name to group table, thus
removing access control settings for the given principal. The entry to
be removed is indexed by the MODEL and SECURITYNAME values, which
should match those used in the corresponding createSec2Group command
(or equivalent).
createView [-Ce] NAME SUBTREE MASK
Create an entry in the SNMPv3 MIB view table. A MIB view consists of a
family of view subtrees which may be individually included in or (occa‐
sionally) excluded from the view. Each view subtree is defined by a
combination of an OID subtree together with a bit string mask. The
view table is indexed by the view name and subtree OID values.
[-Ce]
An optional flag to indicate that this view subtree should be
excluded from the named view. If not specified, the default is
to include the subtree in the view. When constructing a view
from a mixture of included and excluded subtrees, the excluded
subtrees should be defined first - particularly if the named
view is already referenced in one or more access entries.
NAME
A string identifying a particular MIB view, of which this OID
subtree/mask forms part (possibly the only part).
SUBTREE
The OID defining the root of the subtree to add to (or exclude
from) the named view.
MASK
A bit mask indicating which sub-identifiers of the associated
subtree OID should be regarded as significant.
deleteView NAME SUBTREE
Delete an entry from the SNMPv3 view table, thus removing the subtree
from the given MIB view. Removing the final (or only) subtree will
result in the deletion of the view. The entry to be removed is indexed
by the NAME and SUBTREE values, which should match those used in the
corresponding createView command (or equivalent).
When removing subtrees from a mixed view (i.e. containing both included
and excluded subtrees), the included subtrees should be removed first.
createAccess GROUPNAME [CONTEXTPREFIX] MODEL LEVEL CONTEXTMATCH READVIEW
WRITEVIEW NOTIFYVIEW
Create an entry in the SNMPv3 access table, thus allowing a certain
level of access to particular MIB views for the principals in the spec‐
ified group (given suitable security model and levels in the request).
The access table is indexed by the group name, context prefix, security
model and security level values.
GROUPNAME
The name of the group that this access entry applies to (as set
up by a createSec2Group command, or equivalent)
CONTEXTPREFIX
A string representing a context name (or collection of context
names) which this access entry applies to. The interpretation
of this string depends on the value of the CONTEXTMATCH field
(see below).
If omitted, this will default to the null context "".
MODEL
An integer representing the security model, taking one of the
following values:
1 - reserved for SNMPv1
2 - reserved for SNMPv2c
3 - User-based Security Model (USM)
LEVEL
An integer representing the minimal security level, taking one
of the following values:
1 - noAuthNoPriv
2 - authNoPriv
3 - authPriv
This access entry will be applied to requests of this level or
higher (where authPriv is higher than authNoPriv which is in
turn higher than noAuthNoPriv).
CONTEXTMATCH
Indicates how to interpret the CONTEXTPREFIX value. If this
field has the value '1' (representing 'exact') then the context
name of a request must match the CONTEXTPREFIX value exactly for
this access entry to be applicable to that request.
If this field has the value '2' (representing 'prefix') then the
initial substring of the context name of a request must match
the CONTEXTPREFIX value for this access entry to be applicable
to that request. This provides a simple form of wildcarding.
READVIEW
The name of the MIB view (as set up by createView or equivalent)
defining the MIB objects for which this request may request the
current values.
If there is no view with this name, then read access is not
granted.
WRITEVIEW
The name of the MIB view (as set up by createView or equivalent)
defining the MIB objects for which this request may potentially
SET new values.
If there is no view with this name, then read access is not
granted.
NOTIFYVIEW
The name of the MIB view (as set up by createView or equivalent)
defining the MIB objects which may be included in notification
request.
Note that this aspect of access control is not currently sup‐
ported.
deleteAccess GROUPNAME [CONTEXTPREFIX] MODEL LEVEL
Delete an entry from the SNMPv3 access table, thus removing the speci‐
fied access control settings. The entry to be removed is indexed by
the group name, context prefix, security model and security level val‐
ues, which should match those used in the corresponding createAccess
command (or equivalent).
createAuth GROUPNAME [CONTEXTPREFIX] MODEL LEVEL AUTHTYPE CONTEXTMATCH VIEW
Create an entry in the Net-SNMP extension to the standard access table,
thus allowing a certain type of access to the MIB view for the princi‐
pals in the specified group. The interpretation of GROUPNAME, CON‐
TEXTPREFIX, MODEL, LEVEL and CONTEXTMATCH are the same as for the cre‐
ateAccess directive. The extension access table is indexed by the
group name, context prefix, security model, security level and authtype
values.
AUTHTYPE
The style of access that this entry should be applied to. See
snmpd.conf(5) and snmptrapd.conf(5) for details of valid tokens.
VIEW
The name of the MIB view (as set up by createView or equivalent)
defining the MIB objects for which this style of access is
authorized.
deleteAuth GROUPNAME [CONTEXTPREFIX] MODEL LEVEL AUTHTYPE
Delete an entry from the extension access table, thus removing the
specified access control settings. The entry to be removed is indexed
by the group name, context prefix, security model, security level and
authtype values, which should match those used in the corresponding
createAuth command (or equivalent).
EXAMPLES
Given a pre-existing user dave (which could be set up using the snm‐
pusm(1) command), we could configure full read-write access to the
whole OID tree using the commands:
snmpvacm localhost createSec2Group 3 dave RWGroup
snmpvacm localhost createView all .1 80
snmpvacm localhost createAccess RWGroup 3 1 1 all all none
This creates a new security group named "RWGroup" containing the SNMPv3
user "dave", a new view "all" containing the full OID tree based on
.iso(1) , and then allows those users in the group "RWGroup" (i.e.
"dave") both read- and write-access to the view "all" (i.e. the full
OID tree) when using authenticated SNMPv3 requests.
As a second example, we could set up read-only access to a portion of
the OID tree using the commands:
snmpvacm localhost createSec2Group 3 wes ROGroup
snmpvacm localhost createView sysView system fe
snmpvacm localhost createAccess ROGroup 3 0 1 sysView none none
This creates a new security group named "ROGroup" containing the (pre-
existing) user "wes", a new view "sysView" containing just the OID tree
based on .iso(1).org(3).dod(6).inet(1).mgmt(2).mib-2(1).system(1) , and
then allows those users in the group "ROGroup" (i.e. "wes") read-
access, but not write-access to the view "sysView" (i.e. the system
group).
EXIT STATUS
The following exit values are returned:
0 - Successful completion
1 - A usage syntax error (which displays a suitable usage message) or a
request timeout.
2 - An error occurred while executing the command (which also displays
a suitable error message).
LIMITATIONS
This utility does not support the configuration of new community
strings, so is only of use for setting up new access control for SNMPv3
requests. It can be used to amend the access settings for existing
community strings, but not to set up new ones.
The use of numeric parameters for secLevel and contextMatch parameters
is less than intuitive. These commands do not provide the full flexi‐
bility of the equivalent config file directives.
There is (currently) no equivalent to the one-shot configure directives
rouser and rwuser.
SEE ALSOsnmpcmd(1), snmpusm(1), snmpd.conf(5), snmp.conf(5), RFC 2575, Net-SNMP
project FAQ
4th Berkeley Distribution 30 May 2003 SNMPVACM(1)
