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https://issues.apache.org/jira/browse/QPID-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13198931#comment-13198931
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Rajith Attapattu commented on QPID-3799:
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A few quick thoughts/comments on the issues raised by Chuck
Conflicting Rules
-------------------
IMO the ACL system should highlight conflicting rules. At least the c++ module
is quite weak in validation and there is a lot more room for improvement there.
"ACL lines greater that 1000 characters are silently truncated. ACL processing
should stop and emit an error if lines are too long."
This is a bug IMO, we should file a JIRA for this.
Limits
--------
As for limits, I think there is a lot of room to improve. We really need to
rethink how we handle limits and their effectiveness.
Some of the improvements we can make,
1. The ability to express rules in a more intuitive way like maxqueuesize <=
1000
2. Ensure that limits can be enforced more meaningfully.
For example trying to limit users with queuesize is not good enough. If
somebody wants to really mess up then they can still create a million queues
(all within the max queue size limit). So IMO the max-queue-size is only
meaningful if we also limit the number of live queues the user can create.
In general I think we need to look at the some improvements to the ACL module.
Some of the drawbacks I see in the current design/model/code are,
1. Does not work within a cluster
2. Being tied to the AMQP 0-10 model
3. Rules cannot be provisioned dynamically
4. Handling of limits is ugly etc..
5. Not being able to integrate with 3rd party security models.
Rajith
> ACL processing by C++ broker produces unexpected results
> --------------------------------------------------------
>
> Key: QPID-3799
> URL: https://issues.apache.org/jira/browse/QPID-3799
> Project: Qpid
> Issue Type: Bug
> Components: C++ Broker
> Affects Versions: 0.14
> Environment: C++ Broker
> Reporter: Chuck Rolke
>
> There are several instances of C++ ACL-processing code that produce results
> that do not match what would be expected after reading the Developer Pages,
> ACL site page. Clean up of both the site page and the code in a few cases
> requires an agreement on the actual desired behaviour.
> Some of the rule sets below are contrived and not something that a normal
> person would write. However, rule sets may be machine generated or they may
> be in a confused state due to cut and paste errors. Rule processing must be
> predictable regardless of how the rule sets came to be.
> 1. Conflicting permissions rules. Given the following rule set[1]:
> acl allow bob@QPID create queue
> acl deny bob@QPID create queue
> acl allow all all
> What happens when bob tries to create a queue? The site page suggests that
> the rules are processed in order and the first rule that matches defines the
> action to take. By that reading bob should be allowed to create a queue. In
> the C++ broker, however, the first 'acl allow' rule is discarded. Then the
> first rule to match is the deny rule.
> Q1: What is the correct behaviour for the conflicting rules in rule set 1?
> 2. ACL lines greater that 1000 characters are silently truncated. ACL
> processing should stop and emit an error if lines are too long.
> 3. The C++ broker handles some numeric limits on queue creation but these
> limits are not documented in the wiki page.
> We have the following rule set[2]:
> 1. acl allow bob create queue maxqueuesize=1000
> 2. acl deny bob all all
> Line 1 allows bob to create queues as long as the qpid.max_size
> argument in the queue_declare request is<= 1000.
> Line 2 prevents bob from doing anything else.
> We have another rule set[3]:
> 1. acl allow bob create queue maxqueuesize=1000
> 2. acl allow bob create queue maxqueuesize=10000
> 3. acl deny bob all all
> What happens when ACL processing gets to Line 1 when bob tries to create a
> queue with max_size = 2000? Line 1 disallows the creation but Line 2 allows
> it.
> * If code treats the numeric tests as another "comparison criteria" then
> Line 1 will not match. This allows processing to move to Line 2 where the
> action will be allowed.
> * If the code treats the numeric tests as a "deny subclause" then Line 1
> will be a match and bob will be denied.
> Q3: What should happen when bob tries to create a queue with max_size = 2000
> using rule set [3]?
> 4. Numeric limits should work differently on deny rules[4].
> 1. acl deny bob create queue maxqueuesize=1000
> 2. acl allow bob all all
> I suggest that when the numeric tests specifying max values are used as
> "comparison criteria" then:
> * In an allow rule the match is true when the user's value is "less than or
> equal to" the ACL max limit.
> * In a deny rule the match is true when the user's value is "greater than"
> the ACL max limit.
> Q4: How should numeric limits be applied in deny rules?
> I'm interested to know what folks think is the "correct" behaviour for these
> rules and/or how the Java broker would handle them.
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