Munguva pfupi yapfuura AMD yakazivisa basa rayakaita simba gadzirisa huwandu hwekukuvara izvo zvinokanganisa zvigadzirwa zvako. Izvo zvinokuvadza zvaive yakawanikwa nemuongorori wezvekuchengetedza Danny Odler, iyo mumushumo wayo inoburitsa pachena kuti zvikanganiso zvinogara mu AMD Mini PC iyo inogona kubvumidza varwisi kuti vashandise firmware yakachengeteka uye vaite kodhi yekumanikidza.
Iyi nhevedzano yekushushikana yaive anonzi "SMM Callout" (CVE-2020-12890) uye kuferefetwa kwetsikidzi kunoratidza kushandiswa kwakazara kwe1 kweiyo 3 kudzvinyirira iyo ivo vakawanikwa mumufananidzo weEFI.
SMM Kudana inokutendera iwe kuwana kutonga pamusoro peEFI firmware uye kumhanya kodhi padanho reSMM (System manejimendi maitiro). Kurwiswa kunoda kuwanikwa kwecomputer kana kuwana kune system nekodzero dzemutungamiri.
Kana ukabudirira kurwisa, anorwisa anogona kushandisa iyo AGESA interface (Yakajairwa AMD Encapsulated Software Architecture) kuita kodhi yekumanikidza haigone kuonekwa kubva kuhurongwa hwekushandisa.
Izvo zvinokuvadza zviripo mune kodhi inosanganisirwa muEFI firmware, yakaitwa muSMM modhi (Ring -2), iyo ine yepamusoro yepamusoro kupfuura iyo hypervisor modhi uye zero yekudzivirira mhete, uye iyo ine risingaperi mukana kune ese ndangariro yeiyo system.
Kana kodhi ikamhanya muSMM, ndangariro dzese dzenyama dzinogona kuwanikwa uye hapana chinogona kukutadzisa kunyora pasi zvakanyanya data rakakosha pamapeji epanyama eiyo kernel kana hypervisor. Iyo SMM kodhi inoshanda senge mhando yeiyo mini OS: ine I / O masevhisi, ndangariro mepu services, kugona mepu yakavanzika nzvimbo, SMM kukanganisa manejimendi, zviitiko zvezviitiko, nezvimwe.
Kupfupisa: SMM kodhi ndiyo yakanyanya kodhi kodhi yakaitwa paCPU, kodhi yacho yakavanzwa zvachose kubva kune inomhanya inoshanda sisitimu, haigone kuchinjwa nekernel uye kunyangwe nemidziyo yeDMA uye yakanyanya kukosha SMM kodhi inogona kuwana chero epanyama ndangariro.
Somuenzaniso, mushure mekuwana mukana kune inoshanda sisitimu semhedzisiro yekushandisa kumwe kushomeka kana nzira dzeinjiniya yemagariro, anorwisa Unogona kushandisa kusagadzikana naSMM Kudana kudarika nzira yakachengeteka yebhoti (UEFI Yakachengeteka Boot), kuunza yakaipa code kana rootkits isingaonekwe kune iyo system muSPI Flash, uye zvakare yekurwisa kune hypervisors e kupfuura nzira dzekutendeseka dzekutarisisa enharaunda.
"AMD inoziva nezve kutsvagurudza kutsva kwakanangana nekukanganisa mukana kweiyo AMD software tekinoroji yakapihwa kune mamaboardboard vagadziri kuti vashandise mune yavo Unified Extensible Firmware Interface (UEFI) zvivakwa uye zvirongwa zvekupedzisa kuburitswa kweshanduro dzakagadziridzwa dzakagadzirirwa kudzikisira dambudziko pakupera kwe Chikumi 2020. »inoverenga chiziviso che AMD.
"Kurwiswa kwakanangwa kunotsanangurwa mukutsvagurudza kunoda mukana wemuviri kana wehutongi kuwana kune system inoenderana neiyo AMD Laptop kana maprosesa akapinza. Kana iri danho rekuwana rikawanikwa, anorwisa anogona kushandisa AMD's Generic Encapsulated Software Architecture (AGESA) kuti aite kodhi yekumanikidza pasina kuwanikwa nehurongwa hwekushanda.
Izvo zvinokuvadza zvinokonzerwa kune kukanganisa mune iyo SMM kodhi nekuda kwe kune kushomeka kwekutarisa kwekero yeiyo buffer target Kana iyo SmmGetVariable () basa rodaidzwa mune iyo SMI 0xEF inobata.
Nekuda kweichi chipenga, anorwisa anogona kunyora zvisina tsarukano kune yemukati yeSMM memory (SMRAM) uye oiita sekodhi nekodzero dzeSMM. AMD yakacherekedza kuti vamwe chete ma processor yakavhurwa pakati pe2016 na2019 ivo vanokanganiswa nenjodzi.
"SMM ndiyo kodhi yakanyanya kukudzwa iyo inogona kumhanya pane x86 CPU, ichiibvumira kurwisa chero chikamu chepasi, kusanganisira Kernel neHypervisor." verenga ongororo yakaburitswa naOdler.
Iye mutengesi wechipu atoendesa kare mazhinji emhando dzakavandudzwa dzeAGESA kune vamwe vayo. AMD inokurudzira vashandisi kuti vachengetedze masystem avo kusvika pari zvino nekuisa iwo ekupedzisira matches.
Kana iwe uchida kuziva zvakawanda nezvazvo, unogona kubvunza chirevo nekuenda kunotevera chinongedzo.
mabviro: https://medium.com