[Stage 0/1] Initial draft for IO fieldset RFC

rfcs/text/0033-tty-output.md

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+# 0000: Process IO events
+<!-- Leave this ID at 0000. The ECS team will assign a unique, contiguous RFC number upon merging the initial stage of this RFC. -->
+
+- Stage: **0 (strawperson)** <!-- Update to reflect target stage. See https://elastic.github.io/ecs/stages.html -->
+- Date: **TBD** <!-- The ECS team sets this date at merge time. This is the date of the latest stage advancement. -->
+
+<!--
+As you work on your RFC, use the "Stage N" comments to guide you in what you should focus on, for the stage you're targeting.
+Feel free to remove these comments as you go along.
+-->
+
+<!--
+Stage 0: Provide a high level summary of the premise of these changes. Briefly describe the nature, purpose, and impact of the changes. ~2-5 sentences.
+-->
+
+The goal of the RFC is to introduce new fields to the process fieldset to track input and output data from processes. The initial implementation will be focused on capturing TTY output from processes. Each event will contain some number of bytes of output data (configurable) along with context on which tty, entry_leader, session_leader and process generated the output. This 'io' event will be used to drive new visualizations in Kibana as well as give security analysts another avenue for investigation and rule creation.
+
+<!--
+Stage 1: If the changes include field additions or modifications, please create a folder titled as the RFC number under rfcs/text/. This will be where proposed schema changes as standalone YAML files or extended example mappings and larger source documents will go as the RFC is iterated upon.
+-->
+
+see: 0033/io.yml
+
+<!--
+Stage X: Provide a brief explanation of why the proposal is being marked as abandoned. This is useful context for anyone revisiting this proposal or considering similar changes later on.
+-->
+
+## Fields
+
+<!--
+Stage 1: Describe at a high level how this change affects fields. Include new or updated yml field definitions for all of the essential fields in this draft. While not exhaustive, the fields documented here should be comprehensive enough to deeply evaluate the technical considerations of this change. The goal here is to validate the technical details for all essential fields and to provide a basis for adding experimental field definitions to the schema. Use GitHub code blocks with yml syntax formatting, and add them to the corresponding RFC folder.
+-->
+
+- process.io (object)
+- process.io.source (keyword)
+- process.io.data (array of objects)
+- process.io.data.raw (keyword)
+
+<!--
+Stage 2: Add or update all remaining field definitions. The list should now be exhaustive. The goal here is to validate the technical details of all remaining fields and to provide a basis for releasing these field definitions as beta in the schema. Use GitHub code blocks with yml syntax formatting, and add them to the corresponding RFC folder.
+-->
+
+## Usage
+
+<!--
+Stage 1: Describe at a high-level how these field changes will be used in practice. Real world examples are encouraged. The goal here is to understand how people would leverage these fields to gain insights or solve problems. ~1-3 paragraphs.
+-->
+
+These fields will primarily be used to replay and visualize TTY output for a linux session. Since the output is captured raw, terminal sequence control codes et al, we'll be making use of xtermjs.org to render these output messages over time. This will give security analysts a new means with which to investigate linux sessions.
+
+Because the data is flowing in as UTF-8 encoded chars, it will be possible to write rules against TTY output. This will allow Session View to decorate the output viewer with the location of alerts and other important info like the process writing to the TTY device.
+
+## Source data
+
+<!--
+Stage 1: Provide a high-level description of example sources of data. This does not yet need to be a concrete example of a source document, but instead can simply describe a potential source (e.g. nginx access log). This will ultimately be fleshed out to include literal source examples in a future stage. The goal here is to identify practical sources for these fields in the real world. ~1-3 sentences or unordered list.
+-->
+
+```
+  {
+    event: {
+      kind: 'event',
+      action: 'io'
+    },
+    process: {
+      args: ['ls'],
+      executable: '/bin/ls',
+      ...other_process_details,
+
+      entry_leader: <entry_context>,
+      session_leader: <session_context>,
+
+      tty: {
+        major: 1
+        minor: 128
+      },
+
+      io: {
+        source: 'tty',
+        data: [
+          // using an array of objects to future proof ability to include meta information for each chunk of io (like a timestamp)
+          { raw: 'hello world' },
+          { raw: '#!/bin/bash' },
+          { raw: 'goodbye world' }
+        ]
+      }
+    }
+  }
+```
+
+<!--
+Stage 2: Included a real world example source document. Ideally this example comes from the source(s) identified in stage 1. If not, it should replace them. The goal here is to validate the utility of these field changes in the context of a real world example. Format with the source name as a ### header and the example document in a GitHub code block with json formatting, or if on the larger side, add them to the corresponding RFC folder.
+-->
+
+<!--
+Stage 3: Add more real world example source documents so we have at least 2 total, but ideally 3. Format as described in stage 2.
+-->
+
+## Scope of impact
+
+<!--
+Stage 2: Identifies scope of impact of changes. Are breaking changes required? Should deprecation strategies be adopted? Will significant refactoring be involved? Break the impact down into:
+ * Ingestion mechanisms (e.g. beats/logstash)
+ * Usage mechanisms (e.g. Kibana applications, detections)
+ * ECS project (e.g. docs, tooling)
+The goal here is to research and understand the impact of these changes on users in the community and development teams across Elastic. 2-5 sentences each.
+-->
+
+## Concerns
+
+<!--
+Stage 1: Identify potential concerns, implementation challenges, or complexity. Spend some time on this. Play devil's advocate. Try to identify the sort of non-obvious challenges that tend to surface later. The goal here is to surface risks early, allow everyone the time to work through them, and ultimately document resolution for posterity's sake.
+-->
+
+1. Data exfiltration. TTY output is a sensitive surface area to expose. It definitely should be featured gated, and an opt in for customers. At least until we implement some robust "regex scrubbing" mechanisms.
+2. Per event batch size should be considered. If batch size is too big, alerting on IO data becomes fuzzy, as rules are evaluated on the document level, not on an individual line of output. This could make it a challenge to figure out what part of the message triggered the alert. Also, some performance benchmarking should be done to see how rule evaluation performs on process.io.data.raw when data.length > X
+
+<!--
+Stage 2: Document new concerns or resolutions to previously listed concerns. It's not critical that all concerns have resolutions at this point, but it would be helpful if resolutions were taking shape for the most significant concerns.
+-->
+
+<!--
+Stage 3: Document resolutions for all existing concerns. Any new concerns should be documented along with their resolution. The goal here is to eliminate risk of churn and instability by ensuring all concerns have been addressed.
+-->
+
+## People
+
+The following are the people that consulted on the contents of this RFC.
+
+* @mitodrummer | author
+* @m-sample | subject matter expert
+* @norrietaylor| subject matter expert
+* @mattnite | subject matter expert
+* @tabell | subject matter expert
+
+<!--
+Who will be or has been consulted on the contents of this RFC? Identify authorship and sponsorship, and optionally identify the nature of involvement of others. Link to GitHub aliases where possible. This list will likely change or grow stage after stage.
+
+e.g.:
+
+* @Yasmina | author
+* @Monique | sponsor
+* @EunJung | subject matter expert
+* @JaneDoe | grammar, spelling, prose
+* @Mariana
+-->
+
+
+## References
+
+<!-- Insert any links appropriate to this RFC in this section. -->
+
+### RFC Pull Requests
+
+<!-- An RFC should link to the PRs for each of it stage advancements. -->
+
+* Stage 0: https://github.com/elastic/ecs/pull/NNN
+
+<!--
+* Stage 1: https://github.com/elastic/ecs/pull/NNN
+...
+-->

rfcs/text/0033/process.yml

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+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# 	http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+---
+- name: process
+  fields:
+
+    # minor typo fix in description for this field. "pts/0 -> "pts/0"
+    - name: tty.char_device.major
+      description: >
+        The major number identifies the driver associated with the device. The character device's major and minor numbers can be algorithmically combined to produce the more familiar terminal identifiers such as "ttyS0" and "pts/0". For more details, please refer to the Linux kernel documentation.
+
+    # new 'io' properties for tracking tty output
+    - name: io
+      level: extended
+      type: object
+      short: Fields describing a batch of input or output (IO) data produced by a process.
+      description: >
+        Fields describing a batch of input or output (IO) data produced by a process.
+
+        These fields should only appear on the top level process object when event.action is 'io'
+
+    - name: io.source
+      level: extended
+      type: keyword
+      short: Source of the process IO
+      description: >
+         Source of the process IO
+
+         e.g tty
+
+    - name: io.data
+      level: extended
+      type: object
+      description: >
+        A time ordered array of objects containing process input/output chunks encoded as UTF-8.
+
+        For 'tty' sources, each entry in the array is a "best effort" line of TTY output. Note: Not all entries will be complete lines due to batching and timeout constraints.
+      normalize: array
+
+    - name: io.data.raw
+      level: extended
+      type: keyword
+      short: A chunk of raw process IO encoded as UTF-8
+      description: >
+        A chunk of raw process IO encoded as UTF-8
+
+        Output is captured raw, and so can contain escaped terminal control codes. ASCII formatting and color escape codes can cause unexpected characters to appear between words, so care should be taken when writing rules or filters against process.io.data.raw.