[APPSEC-8287] Add AppSec::Processor::RuleMerger #2686
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LGTM, but I think it needs a few adjustments.
Also, I feel like it would make sense to rebase this PR onto the chain of PRs, the latest add-remote-config-component one would be a good candidate as a rebase target + base branch for the PR. This would make integration of the merger usable immediately.
| if override['rules_override'] | ||
| override['rules_override'].each do |rule_override| | ||
| rules_override << rule_override | ||
| end | ||
| elsif override['exclusions'] | ||
| override['exclusions'].each do |exclusion| | ||
| exclusions << exclusion | ||
| end | ||
| end |
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I seem to recall you mentioned it's probably best if rules_override and exclusions processing is split between combine_overrides and combine_exclusions.
Do we expect these to be ever realistically mixed?
| rules_data = combine_data(data) if data | ||
| rules_overrides_and_exclusions = combine_overrides(overrides) if overrides | ||
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| rules_dup.merge!(rules_data) if rules_data |
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If I'm not mistaken combine_data only ever returns a hash with the 'rules_data' key?
Maybe if combine_data returned result, then result could be assigned directly to rules_dup['rules_data'].
This would also save us a hash allocation.
| rules_overrides_and_exclusions = combine_overrides(overrides) if overrides | ||
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| rules_dup.merge!(rules_data) if rules_data | ||
| rules_dup.merge!(rules_overrides_and_exclusions) if rules_overrides_and_exclusions |
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If I'm not mistaken combine_overrides only ever returns a hash with the 'rules_override' and 'exclusions' key?
Maybe if combine_overrides was split and returned result, then result could be assigned directly to rules_dup['rules_override'] and rules_dup['exclusions']
This would also save us a hash allocation.
| data_exists = result.select { |x| x['id'] == value['id'] } | ||
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| if data_exists.any? | ||
| existing_data = data_exists.first | ||
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| if existing_data['type'] == value['type'] |
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This seems to be equivalent to:
if (existing_data = result.find { |x| x['id'] == value['id'] }) &&
if existing_data['type'] == value['type']
# ...
So:
if (existing_data = result.find { |x| x['id'] == value['id'] }) && existing_data['type'] == value['type']
# ...
And a single else clause
| # There could be cases that there is no experitaion value. | ||
| # To singal that there is no expiration we use the default value 0. |
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If it was omitted at the source, should we omit it instead of using a default?
| result = data1.each_with_object({}) do |value, acc| | ||
| acc[value['value']] = value['expiration'] | ||
| end | ||
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| data2.each do |data| | ||
| if result.key?(data['value']) | ||
| # The value is duplicated so we need to keep | ||
| # the one with the highest expiration value | ||
| # We replace it if the expiration is higher than the current one | ||
| # or if no experiration | ||
| expiration = result[data['value']] | ||
| result[data['value']] = data['expiration'] if data['expiration'].nil? || data['expiration'] > expiration |
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Could that last expiration be nil?
| module RuleMerger | ||
| class << self | ||
| def merge(rules:, data: nil, overrides: nil) | ||
| rules_dup = rules.dup |
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Looking at the logic below it's a bit hard to track whether no nested mutation happens.
WDYT of adding some deep freeze to the lets in specs so that we ensure we never mutate the originals?
| end | ||
| end | ||
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| return unless result.any? |
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I guess this is because empty rulesets are disallowed by libddwaf
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This will not be any empty ruleset but an empty rules_data key. We will not add it to the final rules hash.
| class Processor | ||
| # RuleMerger merge different sources of information | ||
| # into the rules payload | ||
| module RuleMerger |
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This is not merging rules but collections of rules, expirations, and overrides. I'm not happy with the name but I can't figure another one right now so let's go with that.
Consider maybe doing it the other way -- merging this to master (as long as it has no impact on existing users) and merging master into the working branch. This way allows incremental changes to land in master, rather than a big "land-everything" PR that is very hard to review. |
I'm confused, there is no "big PR", there is a chain of (currently) seven PRs, each with a specific and progressive subset of change that should be easier to review in order and in isolation than a big PR, and each allowing incremental changes to land. Whether this PR here is incrementally merged now or downstream of the sequence of PRs is immaterial. Each PR having their own branch based on the previous one, merging this to master and then merging master to the (currently) last branch would effectively freeze all the branches since they would not be rebase-able anymore†. So any change on a specific "top" branch would mean merging that branch down, once in each downstream branch. This would make history a terrible mess. The alternative would be to merge only on the last one, effectively turning the chained but independent branches into one big PR behind the scenes. † I can see some ways to work around that, like merge-preserving rebasing only the last one, then |
In Appsec, there has to be some transformation when the remote configuration client is going to merge existing information with the provided by the agent.
The agent can provide multiple pieces of information regarding new rules data, rules override, or entirely new rules set.
Before being able to instantiate a new
AppSec::Processorwe need to make sure the rules payload has the correct format.The correct format is:
There is also some merging logic we need to account for when merging
rules_dataWhen combining rules data with the same id, type and value, we need to keep the one with the highest expiration or if no expiration is provided.