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Co-authored-by: Lorenzo Fontana <lo@linux.com> Co-authored-by: Leonardo Di Donato <leodidonato@gmail.com> Signed-off-by: Leonardo Di Donato <leodidonato@gmail.com>
114 lines
4.1 KiB
Markdown
114 lines
4.1 KiB
Markdown
# gRPC Falco Output
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<!-- toc -->
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- [Summary](#summary)
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- [Motivation](#motivation)
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* [Goals](#goals)
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* [Non-Goals](#non-goals)
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- [Proposal](#proposal)
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* [Use cases](#use-cases)
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* [Diagrams](#diagrams)
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* [Design Details](#design-details)
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<!-- tocstop -->
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## Summary
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We intend to build a simple gRPC server and SDKs - eg., [falco#785](https://github.com/falcosecurity/falco/issues/785) - to allow users receive and consume the alerts regarding the violated rules.
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## Motivation
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The most valuable information that Falco can give to its users are the alerts.
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An alert is an "output" when it goes over a transport, and it is emitted by Falco every time a rule is matched.
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At the current moment, however, Falco can deliver alerts in a very basic way, for example by dumping them to standard output.
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For this reason, many Falco users asked, with issues - eg., [falco#528](https://github.com/falcosecurity/falco/issues/528) - or in the [slack channel](https://sysdig.slack.com) if we can find a more consumable way to implement Falco outputs in an extensible way.
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The motivation behind this proposal is to design a new output implementation that can meet our user's needs.
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### Goals
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- To decouple the outputs from the Falco code base
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- To design and implement an additional output mode by mean of a gRPC **streaming** server
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- To keep it as simple as possible
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- To have a simple contract interface
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- To only have the responsibility to route Falco output requests and responses
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- To continue supporting the old output formats by implementing their same interface
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- To be secure by default (**mutual TLS** authentication)
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- To be **asynchronous** and **non-blocking**
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- To implement a Go SDK
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### Non-Goals
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- To substitute existing outputs (stdout, syslog, etc.)
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- To support different queing systems than the default (round-robin) one
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- To support queuing mechanisms for message retransmission
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- Users can have a local gRPC relay server along with Falco that multiplexes connections and handles retires and backoff
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- To change the output format
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- To make the message context (text, fields, etc.) and format configurable
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- Users can already override rules changing their output messages
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- To act as an orchestrator for Falco instances
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## Proposal
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### Use cases
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- Receive Falco events with a well-defined contract over wire
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- Integrate Falco events with existing alerting/paging mechanisms
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- Integrate Falco events with existing monitoring infrastructures/tools
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- Falco outputs SDKs for different languages
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### Diagrams
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The following sequence diagram illustrates the flow happening for a single rule being matched and the consequent alert through the gRPC output client.
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### Design Details
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Here is the proto3 contracts definitions for the client and the server SDK.
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```proto3
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syntax = "proto3";
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import "google/protobuf/timestamp.proto";
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import "schema.proto";
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package falco.output;
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option go_package = "github.com/falcosecurity/client-go/pkg/api/output";
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// The `subscribe` service defines the RPC call
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// to perform an output `request` which will lead to obtain an output `response`.
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service service {
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rpc subscribe(request) returns (stream response);
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}
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// The `request` message is the logical representation of the request model.
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// It is the input of the `subscribe` service.
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// It is used to configure the kind of subscription to the gRPC streaming server.
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message request {
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bool keepalive = 1;
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// string duration = 2; // TODO(leodido, fntlnz): not handled yet but keeping for reference.
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// repeated string tags = 3; // TODO(leodido, fntlnz): not handled yet but keeping for reference.
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}
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// The `response` message is the logical representation of the output model.
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// It contains all the elements that Falco emits in an output along with the
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// definitions for priorities and source.
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message response {
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google.protobuf.Timestamp time = 1;
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falco.schema.priority priority = 2;
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falco.schema.source source = 3;
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string rule = 4;
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string output = 5;
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map<string, string> output_fields = 6;
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// repeated string tags = 7; // TODO(leodido,fntlnz): tags not supported yet, keeping for reference
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}
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```
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---
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