Details
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Bug
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Status: Closed
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Major
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Resolution: Fixed
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0.14
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None
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C++ Broker
Description
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.