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Label and Event Processes in Asbestos

Explore Mandatory Access Control, covert channels, contamination levels, declassification, and event processes in the Asbestos system implementation example. Learn about Asbestos labels, privilege levels, and dynamic department creation.

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Label and Event Processes in Asbestos

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  1. Label and Event Processes in Asbestos Af Troels Munk Haar

  2. Oversigt Mandatory Access Control Asbestos overordnet Asbestos labels Asbestos event proces Covert chanels Implementeringseksempel

  3. Mandatory Access Control • Grundlæggende • Sikkerhedsniveauer og kategorier • Foruddefinerede kategorier • *-egenskaben

  4. MAC forts. *-egenskaben Q Unclassified information P Adgang: U,S,T R Adgang: U,S Unclassified information Adgang: U

  5. Asbestos • Dynamiske oprettelse af afdelinger • Bypass af *-egenskaben • Kommunikationsporte til beskeder • Pipe- og filtilgang via porte • Asynkrone og upålidelige beskeder • Mulig pålidelighed i praksis

  6. Asbestos labels • Labels som funktioner • MAC skemaer • Contamination • Separate send/modtag labels • Privilegier [*,0,1,2,3] • Notation

  7. File Server Eksempel U: Shell User u UT: Terminal User u US = {uT3,1} UR = {uT3,2} UTS = {uT3,1} UTR = {uT3,2} FS File Server Users u and v V: Shell User v VS = {vT3,1} VR = {vT3,2}

  8. Contamination levels • Hæve contamination level • Defaultværdier • Brugerinformation (uT3) • Send og modtag • Alternativ • Flerniveaupolitiker U: Shell User u UT: Terminal User u Us = {vT2,uT2,1} UR = {uT2,2} Us = {uT2,1} UR = {uT2,2} UTs = {uT2,1} UTR = {vT1,2} FS File Server Users u and v V: Shell User v Vs = {vT2,1} VR = {vT2,2}

  9. Declassification & decontamination • PS(h) = * • Filserveren • FSS = {uT*,vT*,1} • FSR = {uT3,vT3,2} • Decontaminate send / modtag DS og DR • Kræver decontamination rettigheder for h

  10. Integritet • FS - Skriveadgang • Grant handle uG • PS(uG) ≤ 0 • Asbestos: Verifikations label V • V = {uG0,3}, V(uG) ≤ 0 • Obligatorisk integritet

  11. Forhindring af contamination • Mailprogram • Porte (port label pR) • Proces styrer egne port labels (default 0) • Bevilling af portrettigheder • DS = {p*,3} Mail prog Attachment reader High taint

  12. Event Processer • Akkumulering af contamination • Forking: Lav ydelse • Threads: Ingen isolering • Event dispatch loop: Klassisk dispatch loop: Asbestos dispatch loop:

  13. Event Processer • Delprocestilstand pr. bruger • Kernen begrænser privilegier • Base proces > Event proces • ep_checkpoint • ep_yield • Kernen skedulerer event processer • Begrænset samtidighed og skedulerings-overhead

  14. Covert Channels • Timing channels • A påvirker ressource, der indvirker på B • Afhjælpes ved at begrænse præcision • Storage channels • A påvirker en tilstand, B kan observere • Afhjælpes ved at forhindre fork

  15. Send exploit A C B0 B1

  16. Web Server Port: uC Port label uCR: {uC0,2} Port: uC Port label uCR: {uC0,uT3,2} u’s TCP connection netd Grant uw*; read/write Grant uC* Grant uT* Lookup UN/PW idd ok-demux Worker W Grant uC*,uG*, Contaminate uT3 Grant uG*,uT* Create W[u]

  17. Web Server • Web sessions • Managing identities • Database interaction • ok-dbproxy • Evaluering

  18. Asbestos • Spørgsmål?

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