Umphandi wezokhuseleko ngeGitHub yazise kutshanje uchonge ukuba sesichengeni (CVE-2020-16125) kwiGNOME Display Manager (GDM), inoxanduva lokubonisa isikrini sokungena.
Idityaniswe nolunye ubungozi kwinkonzo yokulandelela iakhawunti (iakhawunti-daemon), ingxaki ivumela ikhowudi ukuba isebenze njengengcambu. Ukuba semngciphekweni kunxulunyaniswa nokumiliselwa okungalunganga kwesixhobo sokuqala sokumisela ukuba akunakwenzeka ukufikelela kwinkonzo yedemon yedemon nge-DBus.
Malunga nokuba sesichengeni
Umsebenzisi ongenasiphelo unokuphazamisa inkqubo yeakhawunti-yedemon okanye uxhome, yintoni eza kudala iimeko Ukusetyenziselwa i-gnome-initial-setup ukuba iqhutywe kwi-GDM, apho umsebenzisi omtsha angabhalisa njengelungu leqela le-sudo, oko kukuthi, banakho ukuqhuba iinkqubo njengengcambu.
Ngokwesiqhelo I-GDM ibiza i-gnome-yokuqala-ukuseta ukuseta umsebenzisi wokuqala ukuba akukho zi-akhawunti kwinkqubo. Ukuqinisekiswa kobukho beakhawunti kwenziwa ngokunxibelelana neeakhawunti-daemon. Ukuba inkqubo ekhankanyiweyo iyasilela, i-GDM ithatha ukuba iiakhawunti zilahlekile kwaye iqala inkqubo yokuseta yokuqala.
Umphandi uchonge iindlela ezimbini zokuphazamisa inkqubo yeakhawunti ye-daemon-Iyokuqala (i-CVE-2020-16126) kungenxa yokuseta kwakhona ngokuchanekileyo kunye neyesibini (CVE-2020-16127) ngempazamo ngelixa kusenziwa ifayile ".pam_envelo".
Kwakhona, obunye ubungozi bufunyenwe kwiiakhawunti zeakhawunti (I-CVE-2018-14036) kubangelwe kukungachazeki kwendlela yefayile kunye nokuvumela umxholo wefayile ukuba ufundwe kwinkqubo.
Ukuba semngciphekweni kwiiakhawunti-iidemon kubangelwa lutshintsho olwenziwe ngabaphuhlisi be-Ubuntu kwaye aluveli kwiiakhawunti eziphambili-ikhowudi yeedemon yeprojekthi yeFreeDesktop kunye nephakheji yeDebian.
Umcimbi we-CVE-2020-16127 okhoyo kwisiqwengana esongezwe ku-Ubuntu esisebenzisa is_in_pam_envelo Umsebenzi, ofunda imixholo yefayile .pam_envelo kwifayile yomsebenzisi yekhaya. Ukuba ubeka ikhonkco lokomfuziselo ku / dev / zero endaweni yale fayile, inkqubo yeakhawunti yedemon ixhomeke kwimisebenzi yokufunda engapheliyo kwaye iyeke ukuphendula kwizicelo nge-DBus.
Kuyinto engaqhelekanga ukuba sesichengeni kwenkqubo yokusebenza yale mihla kube lula ukuyisebenzisa. Ngamanye amaxesha, ndibhale amawaka emigca yekhowudi ukuxhaphaza ubungozi.
Uninzi lwezixhaphazo zale mihla zibandakanya amaqhinga anzima, njengokusebenzisa inkohliso kwimemori yokuba sesichengeni sokuphamba izinto ezingezizo kwimfumba, okanye ukubuyisela ifayile nge-symlink kwi-microsecond ngokuchanekileyo ukuxhaphaza ubungozi be-TOCTOU.
Ke kwezi ntsuku kunqabile ukuba semngciphekweni wokungafuneki kwezakhono zokufaka iikhowudi. Ndikwacinga ukuba ukuba semngciphekweni kulula ukuyiqonda, nokuba awunalo ulwazi lwangaphambili malunga nokuba uBuntu usebenza njani okanye amava kuphando lwezokhuseleko.
Ubungozi be-CVE-2020-16126 bubangelwa lelinye iqhosha ebeka kwakhona amalungelo omsebenzisi wangoku ngelixa kusenziwa ezinye iifowuni ze-DBus (umzekelo, org.freedesktop.Accounts.User.SetLanguage).
Inkqubo yedayemon yeakhawunti isebenza ngesiqhelo njengengcambu, ethintela umsebenzisi oqhelekileyo ekuthumeleni imiqondiso.
Kodwa enkosi kwisiqwengana esongeziweyo, amalungelo enkqubo anokuphinda usethwe kwakhona kwaye umsebenzisi angayiphelisa le nkqubo ngokuthumela umqondiso. Ukwenza uhlaselo, yenza nje iimeko zokususa amalungelo (RUID) kwaye uthumele isignali ye-SIGSEGV okanye ye-SIGSTOP kwinkqubo yedemon yeakhawunti.
Umsebenzisi uphelisa iseshoni yemizobo kwaye uye kwikhonkco lombhalo (ICtrl-Alt-F1).
Emva kokuba iseshoni yemizobo iphelile, i-GDM izama ukubonisa isikrini sokungena, kodwa iyaxhoma xa uzama ukufumana impendulo kwiakhawunti-daemon.
Iimpawu ze-SIGSEGV kunye ne-SIGCONT zithunyelwa zisuka kwikhonsoli ukuya kwinkqubo yeakhawunti yedemon, ibangela ukuba ixhomeke.
Ungathumela imiqondiso ngaphambi kokuphuma kwiseshoni yemizobo, kodwa kuya kufuneka uyenze ngokulibaziseka ukufumana ixesha lokugqiba iseshoni kwaye ngaphambi kokuba kuthunyelwe isiginali i-GDM ibinexesha lokuqalisa.
Isicelo kwiakhawunti daemon kwi-GDM siyasilela kwaye i-GDM ibiza into eluncedo yokuqalisa-ukuseta, ekunxibelelaneni kwayo kwanele ukwenza iakhawunti entsha.
Umngcipheko ulungiswe kwi-GNOME 3.36.2 kunye ne-3.38.2. Ukusetyenziswa komngcipheko kuqinisekisiwe ku-Ubuntu nakwiziphumo zayo.
Umthombo: https://securitylab.github.com