v2 ACL file format for brokers

This new ACL implementation has been designed for implementation and interoperability on all Qpid brokers. It is currently supported in the following brokers:

Contents

Specification

 Notes on file formats

• A line starting with the character '#' will be considered a comment, and are ignored.
• Since the '#' char (and others that are commonly used for comments) are commonly found in routing keys and other AMQP literals, it is simpler (for now) to hold off on allowing trailing comments (ie comments in which everything following a '#' is considered a comment). This could be reviewed later once the rest of the format is finalized.
• Empty lines ("") and lines that contain only whitespace (any combination of ' ', '\f', '\n', '\r', '\t', '\v') are ignored.
• All tokens are case sensitive. "name1" != "Name1" and "create" != "CREATE".
• Group lists may be extended to the following line by terminating the line with the '\' character. However, this may only occur after the group name or any of the names following the group name. Empty extension lines (ie just a '\' character) are not permitted.

  # Examples of extending group lists using a trailing '\' character
  
  group group1 name1 name2 \
               name3 name4 \
               name5
  
  group group2 \
               group1 \
               name6
  
  # The following are illegal:
  
  # '\' must be after group name
  group \
        group3 name7 name8
  
  # No empty extension lines
  group group4 name9 \
                     \
               name10
  

• Additional whitespace (ie more than one whitespace char) between and after tokens is ignored. However group and acl definitions must start with "group" or "acl" respectively and with no preceding whitespace.
• All acl rules are limited to a single line.
• Rules are interpreted from the top of the file down until the name match is obtained; at which point processing stops.
• The keyword "all" is reserved, and matches all individuals, groups and actions. It may be used in place of a group or individual name and/or an action - eg "acl allow all all", "acl deny all all" or "acl deny user1 all".
• The last line of the file (whether present or not) will be assumed to be "acl deny all all". If present in the file, any lines below this one are ignored.
• Names and group names may contain only a-z, A-Z, 0-9, '-','_'.
• Rules must be preceded by any group definitions they may use; any name not previously defined as a group will be assumed to be that of an individual.
• ACL rules must have the following tokens in order on a single line:
  • The string literal "acl";
  • The permission;
  • The name of a single group or individual or the keyword "all";
  • The name of an action or the keyword "all";
  • Optionally, a single object name or the keyword "all";
  • If the object is present, then optionally one or more property name-value pair(s) (in the form property=value).

user = username[@domain[/realm]]
user-list = user1 user2 user3 ...
group-name-list = group1 group2 group3 ...

group <group-name> = [user-list] [group-name-list]


permission = [allow|allow-log|deny|deny-log]
action = [consume|publish|create|access|bind|unbind|delete|purge|update]
object = [virtualhost|queue|exchange|broker|link|route|method]
property = [name|durable|owner|routingkey|passive|autodelete|exclusive|type|alternate|queuename|schemapackage|schemaclass]

acl permission {<group-name>|<user-name>|"all"} {action|"all"} [object|"all"] [property=<property-value>]

Validation

The new ACL file format needs to perform validation on the acl rules. The validation should be performed depending on the set value:

strict-acl-validation=none
The default setting should be 'warn'

On validation of this acl the following checks would be expected:

acl allow client publish routingkey=exampleQueue exchange=amq.direct

1. The If the user 'client' cannot be found, if the authentication mechanism cannot be queried then a 'user' value should be added to the file.
2. There is an exchange called 'amq.direct'
3. There is a queue bound to 'exampleQueue' on 'amq.direct'

Each of these checks that fail will result in a log statement being generated.

In the case of a fatal logging the full file will be validated before the broker shuts down.

Example file:

# Some groups
group admin ted@QPID martin@QPID
group user-consume martin@QPID ted@QPID
group group2 kim@QPID user-consume rob@QPID
group publisher group2 \
                tom@QPID andrew@QPID debbie@QPID

# Some rules
acl allow carlt@QPID create exchange name=carl.*
acl deny rob@QPID create queue
acl allow guest@QPID bind exchange name=amq.topic routingkey=stocks.ibm.#  owner=self
acl allow user-consume create queue name=tmp.*

acl allow publisher publish all durable=false
acl allow publisher create queue name=RequestQueue
acl allow consumer consume queue durable=true
acl allow fred@QPID create all
acl allow bob@QPID all queue
acl allow admin all
acl deny kim@QPID all
acl allow all consume queue owner=self
acl allow all bind exchange owner=self

# Last (default) rule
acl deny all all

Design Documentation

Mapping of ACL traps to action and type

The C++ broker maps the ACL traps in the follow way for AMQP 0-10:
The Java broker currently only performs ACLs on the AMQP connection not on management functions:

Management actions that are not explicitly given a name property it will default the name property to management method name, if the action is 'W' Action will be 'Update', if 'R' Action will be 'Access'.

for example, if the mgnt method 'joinCluster' was not mapped in schema it will be mapped in ACL file as follows

v2 ACL User Guide

Writing Good/Fast ACL

The file gets read top down and rule get passed based on the first match. In the following example the first rule is a dead rule. I.e. the second rule is wider than the first rule. DON'T do this, it will force extra analysis, worst case if the parser does not kill the dead rule you might get a false deny.

allow peter@QPID create queue name=tmp <-- dead rule!!
allow peter@QPID create queue
deny all all

By default files end with

deny all all

the mode of the ACL engine can be swapped to be allow based by putting the following at the end of the file

allow all all

Note that 'allow' based file will be a LOT faster for message transfer. This is because the AMQP specification does not allow for creating subscribes on publish, so the ACL is executed on every message transfer. Also, ACL's rules using less properties on publish will in general be faster.

Getting ACL to Log

In order to get log messages from ACL actions use allow-log and deny-log for example

allow-log john@QPID all all
deny-log guest@QPID all all

User Id / domains running with C++ broker

The user-id used for ACL is taken from the connection user-id. Thus in order to use ACL the broker authentication has to be setup. i.e. (if --auth no is used in combination with ACL the broker will deny everything)

The user id in the ACL file is of the form <user-id>@<domain> The Domain is configured via the SASL configuration for the broker, and the domain/realm for qpidd is set using --realm and default to 'QPID'.

To load the ACL module use, load the acl module cmd line or via the config file

./src/qpidd --load-module src/.libs/acl.so

The ACL plugin provides the following option '--acl-file'. If do ACL file is supplied the broker will not enforce ACL. If an ACL file name is supplied, and the file does not exist or is invalid the broker will not start.

ACL Options:
  --acl-file FILE       The policy file to load from, loaded from data dir