Gulu la ofufuza ochokera ku Graz University of Technology (Austria), yomwe kale idadziwika kuti ikupanga njira zowukira , , ΠΈ , adachita kafukufuku wokhudza kukhathamiritsa kwa hardware kwa ma processor a AMD ndi Njira ziwiri zatsopano zowukira mayendedwe am'mbali zomwe zimagwiritsa ntchito kutayikira kwa data panthawi yogwiritsa ntchito njira yolosera za LXNUMX cache ya ma processor a AMD. Njirazi zitha kugwiritsidwa ntchito kuchepetsa chitetezo cha ASLR, kubwezeretsanso makiyi pakukhazikitsa kwa AES kosatetezeka, ndikuwonjezera mphamvu ya Specter attack.
Mavuto adadziwika pakukhazikitsa njira yolosera zam'tsogolo (njira yolosera) mu cache ya data yoyamba ya CPU (L1D), yomwe imagwiritsidwa ntchito kulosera kuti ndi njira yanji yomwe ili ndi adilesi inayake. Kukhathamiritsa komwe kumagwiritsidwa ntchito mu mapurosesa a AMD kumachokera pakuwunika ma ΞΌ-tag (ΞΌTag). ΞΌTag imawerengedwa pogwiritsa ntchito hashi yeniyeni ku adilesi yeniyeni. Pakugwira ntchito, injini yolosera zamakina imagwiritsa ntchito ΞΌTag kudziwa njira yosungira patebulo. Choncho, ΞΌTag imalola purosesa kuti adzichepetse yekha kuti apeze njira yeniyeni, popanda kufufuza njira zonse, zomwe zimachepetsa kwambiri kugwiritsa ntchito mphamvu za CPU.
Panthawi yosinthira njira yolosera njira yolosera njira m'mibadwo yosiyanasiyana ya mapurosesa a AMD omwe adatulutsidwa kuyambira 2011 mpaka 2019, njira ziwiri zatsopano zowukira m'mbali zidadziwika:
- Collide+Probe - imalola wowukirayo kuti azitha kuyang'anira momwe angakumbukire njira zomwe zikuyenda pakatikati pa CPU. Chofunikira cha njirayi ndikugwiritsa ntchito maadiresi omwe amayambitsa kugundana mu ntchito ya hashi yomwe imagwiritsidwa ntchito kuwerengera ΞΌTag kutsata kukumbukira kukumbukira. Mosiyana ndi kuukira kwa Flush + Reload ndi Prime + Probe komwe kumagwiritsidwa ntchito pa ma Intel processors, Collide + Probe sigwiritsa ntchito kukumbukira komwe mudagawana ndipo imagwira ntchito popanda kudziwa maadiresi.
- Lowetsani + Reload - imakupatsani mwayi wodziwa bwino kwambiri zolowera pamakumbukidwe pamtundu womwewo wa CPU. Njirayi imachokera pa mfundo yakuti selo lokumbukira thupi likhoza kukhala mu cache ya L1D kamodzi. Iwo. kulowa mu cell yokumbukira imodzimodzi pa adilesi yosiyana kumapangitsa kuti seloyo itulutsidwe mu cache ya L1D, kulola mwayi wokumbukira kutsata. Ngakhale kuwukiraku kumadalira kukumbukira komwe kugawana nawo, sikumatsegula mizere yosungira, zomwe zimalola kuti anthu aziwukira mobisa zomwe sizimachotsa deta kuchokera pagawo lomaliza.
Kutengera njira za Collide+Probe ndi Load+Reload, ofufuza awonetsa zochitika zingapo zowukira m'mbali:
- Kuthekera kogwiritsa ntchito njira zopangira njira yolumikizirana yobisika pakati pa njira ziwiri, kulola kusamutsa deta pa liwiro la 588 kB pamphindikati, kukuwonetsedwa.
- Pogwiritsa ntchito kugunda mu ΞΌTag, zinali zotheka kuchepetsa entropy pamitundu yosiyanasiyana ya ASLR (Address Space Layout Randomization) ndikudutsa chitetezo cha ASLR mu kernel pa Linux yosinthidwa kwathunthu. Kuthekera kochita chiwembu kuti muchepetse ASLR entropy kuchokera ku mapulogalamu a ogwiritsa ntchito ndikugwiritsa ntchito JavaScript code yochitidwa mu sandbox malo ndi kachidindo kamene kamayendera malo ena a alendo akuwonetsedwa.
- Kutengera njira ya Collide+Probe, kuwukira kudakhazikitsidwa kuti abwezeretse kiyi yobisa kuchokera pakukhazikitsa kosavutikira (kutengera ) AES encryption.
- Pogwiritsa ntchito njira ya Collide + Probe monga njira yopezera deta, Specter attack inatha kuchotsa deta yachinsinsi kuchokera ku kernel popanda kugwiritsa ntchito kukumbukira komwe kumagwirizana.
Chiwopsezochi chimachitika pa mapurosesa a AMD kutengera ma microarchitectures
Bulldozer, Piledriver, Steamroller, Zen (Ryzen, Epic), Zen+ ndi Zen2.
AMD idadziwitsidwa za nkhaniyi pa Ogasiti 23, 2019, koma mpaka pano ndi chidziwitso choletsa kusatetezeka. Malinga ndi ofufuzawo, vutoli litha kutsekedwa pamlingo wosinthira ma microcode popereka ma MSR bits kuti aletse njira yolosera zam'tsogolo, zofanana ndi zomwe Intel adachita kuti aletse kuyimitsa njira zolosera nthambi.
Source: opennet.ru