Ofufuza ku yunivesite ya Birmingham, omwe kale ankadziwika kuti amapanga Plundervolt ndi VoltPillager, apeza chiopsezo (CVE-2022-43309) m'mabodi ena a seva omwe amatha kulepheretsa CPU popanda kuchira. Chiwopsezo, chomwe chili ndi codenamed PMFault, chingagwiritsidwe ntchito kuwononga ma seva omwe wowukira alibe mwayi wogwiritsa ntchito, koma ali ndi mwayi wogwiritsa ntchito makina ogwiritsira ntchito, omwe angapezeke, mwachitsanzo, chifukwa chogwiritsa ntchito chiwopsezo chosasinthika kapena kuletsa zidziwitso za oyang'anira.
Chofunikira cha njira yomwe yaperekedwa ndikugwiritsa ntchito mawonekedwe a PMBus, omwe amagwiritsa ntchito protocol ya I2C, kuti awonjezere magetsi omwe amaperekedwa kwa purosesa kuzinthu zomwe zimawononga chip. Mawonekedwe a PMBus nthawi zambiri amatsatiridwa mu VRM (Voltage Regulator Module), yomwe imatha kupezeka kudzera mukusintha kwa wolamulira wa BMC. Kuti muwukire matabwa omwe amathandizira PMBus, kuwonjezera pa ufulu wa olamulira mu makina ogwiritsira ntchito, muyenera kukhala ndi mwayi wopita ku BMC (Baseboard Management Controller), mwachitsanzo, kudzera pa IPMI KCS (Keyboard Controller Style) mawonekedwe, kudzera pa Ethernet, kapena kudzera mu kuwala kwa BMC kuchokera ku dongosolo lamakono.
Nkhani yomwe imalola kuwukira popanda kudziwa za magawo otsimikizira mu BMC yatsimikiziridwa mu Supermicro motherboards ndi IPMI thandizo (X11, X12, H11 ndi H12) ndi ASRock, koma ma seva ena omwe PMBus angapezeke nawonso amakhudzidwa. M'kati mwazoyesera, pamene magetsi adakwera kufika pa 2.84 volts, ma processor awiri a Intel Xeon adawonongeka pamatabwa awa. Kuti mupeze BMC popanda kudziwa magawo ovomerezeka, koma pokhala ndi mizu yogwiritsira ntchito makina ogwiritsira ntchito, chiwopsezo cha makina otsimikizira fimuweya chinagwiritsidwa ntchito, zomwe zinapangitsa kuti zitheke kutsitsa zosinthidwa za firmware kwa wolamulira wa BMC, komanso mwayi wopezeka mosavomerezeka kudzera pa IPMI KCS.
Njira yosinthira voteji kudzera pa PMBus itha kugwiritsidwanso ntchito pochita kuukira kwa Plundervolt, komwe kumalola, potsitsa voteji mpaka pamtengo wocheperako, kuwononga zomwe zili m'maselo a data mu CPU omwe amagwiritsidwa ntchito powerengera m'magawo a Intel SGX akutali ndikupanga zolakwika mu ma aligorivimu olondola poyambirira. Mwachitsanzo, ngati musintha mtengo womwe wagwiritsidwa ntchito pochulutsa panthawi ya kubisa, zotulukazo zimakhala zosavomerezeka. Potha kuyitanitsa wothandizira mu SGX kuti alembetse deta yawo, wowukira akhoza, poyambitsa zolephera, kudziunjikira ziwerengero za kusintha kwa ciphertext ndikubwezeretsanso mtengo wa kiyi yosungidwa mu SGX enclave.
Zida zowukira ma board a Supermicro ndi ASRock, komanso chida chofufuzira mwayi wofikira ku PMBus, zimasindikizidwa pa GitHub.
Source: opennet.ru