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Auth using files

Authentication

VerneMQ comes with a simple file-based password authentication mechanism which is enabled by default. If you don't need this it can be disabled by setting:

plugins.vmq_passwd = off

Per default VerneMQ doesn't accept any client that hasn't been configured using vmq-passwd. If you want to change this and accept any client connection you can set:

allow_anonymous = on

{% hint style="info" %} Warning: Setting allow_anonymous=on completely disables authentication in the broker and plugin authentication hooks are never called! Find more information on the authentication hooks here. {% endhint %}

In a production setup you can use the provided password based authentication mechanism, one of the provided authentication Database plugins, or implement your own authentication plugins.

VerneMQ periodically checks the specified password file.

vmq_passwd.password_file = /etc/vernemq/vmq.passwd

The check interval defaults to 10 seconds and can also be defined in the vernemq.conf.

vmq_passwd.password_reload_interval = 10

Setting the password_reload_interval = 0 disables automatic reloading.

{% hint style="info" %} Both configuration parameters can also be changed at runtime using the vmq-admin script.

Example: to dynamically set the reload interval to 60 seconds on all your cluster nodes, issue the following command on one of the nodes:

sudo vmq-admin set vmq_passwd.password_reload_interval=60 --all {% endhint %}

Manage Password Files for VerneMQ

vmq-passwd is a tool for managing password files for the VerneMQ broker. Usernames must not contain ":", passwords are stored in similar format to crypt(3).

How to use vmq-passwd

vmq-passwd [-c | -D] passwordfile username

vmq-passwd -U passwordfile

Options

-c

Creates a new password file. Does not overwrite existing file.

-cf

Creates a new password file. If the file already exists, it will be overwritten.

<no option>

When run with no option, It will create a new user and password and append it to the password file if exists. Does not overwrite the existing file

-D

Deletes the specified user from the password file.

-U

This option can be used to upgrade/convert a password file with plain text passwords into one using hashed passwords. It will modify the specified file. It does not detect whether passwords are already hashed, so using it on a password file that already contains hashed passwords will generate new hashes based on the old hashes and render the password file unusable. Note, with this option neither usernames or passwords may contain ":".

passwordfile

The password file to modify.

username

The username to add/update/delete.

Examples

Add a user to a new password file: (you can choose an arbitrary name for the password file, it only has to match the configuration in the VerneMQ configuration file).

vmq-passwd -c /etc/vernemq/vmq.passwd henry

Delete a user from a password file

vmq-passwd -D /etc/vernemq/vmq.passwd henry

Add multiple user to the existing password file :

vmq-passwd /etc/vernemq/vmq.passwd bob
vmq-passwd /etc/vernemq/vmq.passwd john

Acknowledgements

The original version of vmq-passwd was developed by Roger Light ([email protected]).

vmq-passwd includes :

Authorization

VerneMQ comes with a simple ACL based authorization mechanism which is enabled by default. If you don't need this it can be disabled by setting:

plugins.vmq_acl = off

VerneMQ periodically checks the specified ACL file.

vmq_acl.acl_file = /etc/vernemq/vmq.acl

The check interval defaults to 10 seconds and can also be defined in the vernemq.conf.

vmq_acl.acl_reload_interval = 10

Setting the acl_reload_interval = 0 disables automatic reloading.

{% hint style="info" %} Both configuration parameters can also be changed at runtime using the vmq-admin script. {% endhint %}

Managing the ACL entries

Topic access is added with lines of the format:

topic [read|write] <topic>

The access type is controlled using read or write. If not provided then read an write access is granted for the topic. The topic can use the MQTT subscription wildcards + or #.

The first set of topics are applied to all anonymous clients (assuming allow_anonymous = on). User specific ACLs are added after a user line as follows (this is the username not the client id):

user <username>

It is also possible to define ACLs based on pattern substitution within the the topic. The form is the same as for the topic keyword, but using pattern as the keyword.

pattern [read|write] <topic>

The patterns available for substitution are:

  • %c to match the client id of the client
  • %u to match the username of the client

The substitution pattern must be the only text for that level of hierarchy. Pattern ACLs apply to all users even if the user keyword has previously been given.

Example:

pattern write sensor/%u/data

{% hint style="warning" %} VerneMQ currently doesn't cancel active subscriptions in case the ACL file revokes access for a topic. It is possible to reauthenticate sessions manually (vmq-admin) {% endhint %}

Simple ACL Example

# ACL for anonymous clients
topic bar
topic write foo
topic read open_to_all


# ACL for user 'john'
user john
topic foo
topic read baz
topic write open_to_all

Anonymous users are allowed to

  • publish & subscribe to topic bar.
  • publish to topic foo.
  • subscribe to topic open_to_all.

User john is allowed to

  • publish & subscribe to topic foo.
  • subscribe to topic baz.
  • publish to topic open_to_all.