Automatic Trigger Generation for Rule-based Smart Homes ACM - - PowerPoint PPT Presentation

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Automatic Trigger Generation for Rule-based Smart Homes ACM - - PowerPoint PPT Presentation

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Automatic Trigger Generation for Rule-based Smart Homes ACM SIGPLAN PLAS, Vienna, Austria 10-24-2016 Chandrakana Nandi, Michael D. Ernst UW Seattle, USA 2 3 Common architecture OR 4 How to control your home? 5 How to control your home?

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Automatic Trigger Generation for Rule-based Smart Homes

Chandrakana Nandi, Michael D. Ernst UW Seattle, USA

ACM SIGPLAN PLAS, Vienna, Austria 10-24-2016

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Common architecture

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OR

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How to control your home?

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Automation rules:

when I come home then turn lights on

How to control your home?

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Automation rules are easy and useful

Ur+ CHI 2014, 2016 Ur+ HUPS 2014 Dey+ Pervasive 2006

How to control your home?

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Writing correct automation rules is hard How to control your home?

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Huang+ Ubicomp 2015

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Writing correct automation rules is hard How to control your home?

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Huang+ Ubicomp 2015

mental model actual rule

rule “start laundry” when Item laundry_machine changed then if (laundry_machine == FULL) { sendCommand(laundry_machine, “ON”) } end

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Effects of wrong rules

  • Likely unexpected behavior
  • Security vulnerabilities

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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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Rule Example

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Rule Example

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Rule Example

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

trigger block

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Rule Example

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

trigger item trigger item trigger block

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Rule Example

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

action block

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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State_Away = ON State_Sleeping = ON

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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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Possible mistakes in rules

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Wrong trigger block

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rule "Away rule" when Item State_Roomheater changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Wrong trigger block

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Wrong trigger block

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rule "Away rule" when Item trigger_1 changed Item trigger_2 changed Item trigger_n changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Conflicts

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rule “rule 1” when Item owner_entering_home changed then if (owner_entering_home == true) { sendCommand (hall_light, “ON”) } end rule “rule 2” when Item past_midnight changed then if (past_midnight == true) { sendCommand (hall_light, “OFF”) } end

(owner_entering_home == true && past_midnight == true)

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  • Wrong trigger blocks
  • Conflicts

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  • Wrong trigger blocks
  • Conflicts

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Why is it bad?

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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!(State_Away = ON && State_Sleeping = ON)

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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Both states can be set to true!

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rule "Visitor notification system rule" when Item State_Sleeping changed then if (State_Sleeping.state == ON) { postUpdate (Notification_System , OFF) } else { postUpdate (Notification_System , ON) } end

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Example Attack

rule "Visitor notification system rule" when Item State_Sleeping changed then if (State_Sleeping.state == ON) { postUpdate (Notification_System , OFF) } else { postUpdate (Notification_System , ON) } end rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end 40

Wrongly deactivates notification system

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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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rule "Away rule" when Item State_Away changed then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

Solution

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rule "Away rule" when Item State_Away changed

  • r Item State_Sleeping changed // Fix

then if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

Solution

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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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TrigGen: automatically infer triggers from actions using static analysis

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Idea: live items must be triggers

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Idea: live items must be triggers

Items that are read from before being written to, at the beginning of the action block

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rule "Away rule" when Item State_Away changed then State_Notify = ON if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

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rule "Away rule" when Item State_Away changed then State_Notify = ON if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

  • Identify all items in the

action block AST ○ potential triggers

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rule "Away rule" when Item State_Away changed then State_Notify = ON if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

  • Identify all items in the

action block AST ○ potential triggers

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rule "Away rule" when Item State_Away changed then State_Notify = ON if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

  • Identify all items in the

action block AST ○ potential triggers

  • eliminate those that are

not live ○ redundant triggers ■ State_Notify

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rule "Away rule" when Item State_Away changed then State_Notify = ON if (State_Away.state == ON) { if (State_Sleeping.state != OFF) { postUpdate (State_Sleeping, OFF) } } end

  • Identify all items in the

action block AST ○ potential triggers

  • eliminate those that are

not live ○ redundant triggers ■ State_Notify

  • State_Away,

State_Sleeping: live

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Implementation

item repository rule identify all potential triggers eliminate redundant triggers by live variable analysis

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rule "Rule 1" when trigger then action end

State_Notify State_Away State_Sleeping State_Away State_Sleeping Comparer State_Away Laundry_Machine State_Sleeping Laundry_Machine wrong/extra missing end-user written

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Overview

  • Background on automation rules
  • Problem statement
  • Solution
  • Algorithm and tool development
  • Experiments
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Experiments

  • 96 real end-user written rules for openHAB
  • Action block size: 1 - 220 LOC
  • Featuring categories such as

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Experiments

  • Ground truth

○ Set of necessary and sufficient triggers, i.e. all non-redundant triggers ○ Verified by ■ contacting the end user ■ manual inspection of rules

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Trigger generation

TrigGen suggested a set of necessary and sufficient triggers 91 (95%) False positives False negatives 5 (5%)

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Missing triggers detected 77 (80%)

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Number of missing triggers

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Number of missing triggers

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55%

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Conflicts

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Total conflicts detected 18 True positives 11 (61%) False negatives

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More in the paper

Conflict resolution Group enumeration Proving non-live triggers as redundant

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Remarks

  • TrigGen is applicable to any domain that

has trigger based rules

  • We aimed at home automation involving

○ end users ○ different deployments: every home is different!

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Conclusions

TrigGen automatically generates a set of necessary and sufficient triggers so that rules don’t have:

  • likely unexpected behavior
  • certain security vulnerabilities

TrigGen found 80% real rules used for experimentation to have insufficient triggers

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