Boka revaongorori kubva kuTechnical University yeGraz (Austria) uye Helmholtz Center yeRuzivo Chengetedzo (CISPA), () vheta nyowani yekushandisa padivi-chiteshi kurwisa (L1TF), iyo inokutendera kuti utore data kubva mundangariro yeIntel SGX enclaves, SMM (System Management Mode), nzvimbo dzekurangarira dzeOS kernel uye chaiwo michina mumasisitimu ekuona. Kusiyana nekurwisa kwekutanga kwakarongwa muna 2018 Musiyano mutsva hauna kunangana neIntel processors uye unobata maCPU kubva kune vamwe vagadziri vakaita seArM, IBM uye AMD. Uye zvakare, iyo nyowani nyowani haidi kuita kwepamusoro uye kurwiswa kunogona kuitwa kunyangwe nekumhanyisa JavaScript neWebAssembly muwebhu browser.
Kurwiswa kweForeshadow kunotora mukana wekuti kana ndangariro yasvika padhirowa inokonzeresa kusarudzika (terminal peji kukanganisa), processor inoverengera kero yemuviri uye inotakura iyo data kana iripo muL1 cache. Kuwanikwa kwekufungidzira kunoitwa kusati kwaitwa ndangariro yepeji yekutsvaga tafura yapedzwa uye zvisinei nemamiriro eiyo memory peji rekupinda tafura (PTE), i.e. usati watarisa kuvepo kwedata mundangariro yemuviri uye kuverenga kwayo. Mushure mekunge cheki yekuwanikwa kwendangariro yapedzwa, mukushaikwa kwePresent flag muPTE, kuvhiyiwa kunoraswa, asi iyo data inoramba iri mucheki uye inogona kudzoserwa uchishandisa nzira dzekuona zviri mukati mecache kuburikidza nedivi chiteshi (nekuongorora shanduko munguva yekuwana. kune cached uye isina kuvharwa data).
Vatsvagiri vakaratidza kuti nzira dziripo dzekudzivirira kubva kuForeshadow hadzina kushanda uye dzinoitwa nekududzirwa kusiri kwedambudziko. Kusagadzikana
Foreshadow inogona kushandiswa zvisinei nekernel kuchengetedza nzira dzaimbonzi dzakakwana. Nekuda kweizvozvo, vaongorori vakaratidza mukana wekuita Foreshadow kurwisa masisitimu ane kernels yakare, umo ese aripo Foreshadow ekudzivirira modes anogoneswa, pamwe nemakernels matsva, umo chete Specter-v2 chengetedzo yakavharwa (uchishandisa. iyo Linux kernel sarudzo nospectre_v2).
Zvakawanikwa kuti haina hukama nesoftware prefetch mirairo kana hardware maitiro
prefetch panguva yekuwana ndangariro, asi inoitika kana fungidziro yekufungidzira yemushandisi nzvimbo inonyoresa mukernel. Kududzirwa zvisizvo kwechikonzero chekusagadzikana kwekutanga kwakatungamira kufungidziro yekuti kuburitswa kwedata muForeshadow kunogona kungoitika kuburikidza neL1 cache, nepo kuvapo kwemamwe macode snippets (prefetch gadgets) mukernel kunogona kubatsira mukudonha kwedata kunze kweL1 cache, semuenzaniso, muL3 cache.
Iyo yakatarwa ficha inovhurawo mukana wekugadzira kurwiswa kutsva kwakanangana nemaitiro ekushandura kero chaidzo kuva dzenyama munzvimbo dziri kure uye kuona kero uye data yakachengetwa mumareji eCPU. Sechiratidziro, vaongorori vakaratidza mukana wekushandisa iyo yakaonekwa kuburitsa data kubva kune imwe nzira kuenda kune imwe nekuita kweanosvika gumi mabhiti pasekondi pane system ine Intel Core i10-7U CPU. Iko mukana wekudonhedza zvirimo kubva kuIntel SGX enclave inoratidzwa zvakare (zvakatora maminetsi gumi nemashanu kuona kukosha kwemakumi matatu neshanu kwakanyorerwa 6500-bit rejista). Mamwe marudzi ekurwiswa akave anokwanisika kuita muJavaScript neWebAssembly, semuenzaniso, zvaigoneka kuona kero yenzvimbo yeJavaScript inoshanduka uye kuzadza 32-bit marejista ane kukosha kunodzorwa neanorwisa.
Kuvhara iyo Foreshadow kurwiswa kuburikidza neL3 cache, iyo Specter-BTB (Bazi Target Buffer) nzira yekudzivirira inoshandiswa mune retpoline chigamba set inoshanda. Nekudaro, vaongorori vanotenda kuti zvakakosha kusiya retpoline ichigoneswa kunyangwe pane masisitimu ane maCPU matsva atove nedziviriro kubva mukusagadzikana kunozivikanwa muCPU yekufungidzira execution mechanism. Panguva imwecheteyo, vamiriri veIntel vakataura kuti havaronge kuwedzera mamwe matanho ekudzivirira kubva kuForeshadow kune processors uye vanoiona yakakwana kusanganisira dziviriro kubva kuSpecter V2 uye L1TF (Foreshadow) kurwiswa.
Source: opennet.ru