{"id":82266,"date":"2020-05-20T19:42:07","date_gmt":"2020-05-20T17:42:07","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/udalyonno-ekspluatiruemaya-uyazvimost-v-pochtovom-servere-qmail"},"modified":"2020-05-20T19:42:07","modified_gmt":"2020-05-20T17:42:07","slug":"udalyonno-ekspluatiruemaya-uyazvimost-v-pochtovom-servere-qmail","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sq\/blog\/news\/udalyonno-ekspluatiruemaya-uyazvimost-v-pochtovom-servere-qmail","title":{"rendered":"Vulnerabiliteti i shfryt\u00ebzuesh\u00ebm n\u00eb distanc\u00eb n\u00eb serverin e post\u00ebs qmail","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

K\u00ebrkuesit e siguris\u00eb nga kompania Qualys treguan<\/a><\/noindex> mund\u00ebsia shfryt\u00ebzimin<\/a><\/noindex> t\u00eb metat n\u00eb serverin e post\u00ebs qmail, i njohur<\/a><\/noindex> q\u00eb nga viti 2005 (CVE-2005-1513), por q\u00eb ka mbetur e pakorrigjuar, pasi autori i qmail pretendoi se krijimi i nj\u00eb eksploituesi funksional q\u00eb mund t\u00eb p\u00ebrdoret p\u00ebr t\u00eb sulmuar sistemet n\u00eb konfigurimin e tij t\u00eb paracaktuar ishte jorealiste. N\u00eb Qualys u arrit t\u00eb p\u00ebrgatitet nj\u00eb eksploit q\u00eb e p\u00ebrg\u00ebnjeshtron k\u00ebt\u00eb supozim dhe lejon iniciimin e ekzekutimit t\u00eb kodit n\u00eb server p\u00ebrmes d\u00ebrgimit t\u00eb nj\u00eb mesazhi t\u00eb formuar n\u00eb m\u00ebnyr\u00eb t\u00eb ve\u00e7ant\u00eb.<\/p>\n

Problemi \u00ebsht\u00eb shkaktuar nga mbushja e skajshme e numrave t\u00eb plot\u00eb n\u00eb funksionin stralloc_readyplus(), e cila mund t\u00eb ndodh\u00eb kur p\u00ebrpunoni nj\u00eb mesazh shum\u00eb t\u00eb madh. P\u00ebr t\u00eb shfryt\u00ebzuar k\u00ebt\u00eb, ishte k\u00ebrkuar nj\u00eb sistem 64-bit me nj\u00eb volum t\u00eb kujtes\u00ebs virtuale m\u00eb shum\u00eb se 4GB. N\u00eb analiz\u00ebn fillestare t\u00eb t\u00eb met\u00ebs n\u00eb vitin 2005, Daniel Bernstein, pretendonte se supozimi i pranish\u00ebm n\u00eb kod q\u00eb do t\u00eb thoshte se madh\u00ebsia e mas\u00ebs s\u00eb alokuar gjithmon\u00eb do t\u00eb binte brenda nj\u00eb vlere 32-bit ishte bazuar n\u00eb faktin se askush nuk jep gigabajt\u00eb e kujtes\u00ebs p\u00ebr \u00e7do proces. Gjat\u00eb 15 vit\u00ebve t\u00eb fundit, sistemet 64-bit n\u00eb server\u00eb kan\u00eb z\u00ebvend\u00ebsuar ato 32-bit, duke rritur ndjesh\u00ebm sasin\u00eb e memories s\u00eb ofruar dhe kapacitetin e rrjeteve. <\/p>\n

Paketat shoq\u00ebruese me qmail kan\u00eb pasur parasysh v\u00ebrejtjen e Bernstein dhe kur niste procesi qmail-smtpd, ata kufizuan memorien e disponueshme (p.sh., n\u00eb Debian 10 vendoset nj\u00eb kufi prej 7MB). Por inxhinier\u00ebt nga Qualys zbuluan se kjo nuk ishte e mjaftueshme dhe p\u00ebrve\u00e7 qmail-smtpd, nj\u00eb sulm n\u00eb distanc\u00eb mund t\u00eb b\u00ebhej edhe ndaj procesit qmail-local, i cili n\u00eb t\u00eb gjitha paketat e kontrolluara kishte mbetur pa kufizim. Si prov\u00eb, u p\u00ebrgatit nj\u00eb prototip eksploiti i p\u00ebrshtatsh\u00ebm p\u00ebr sulm ndaj paket\u00ebs q\u00eb ofrohet n\u00eb Debian me konfigurimin e saj t\u00eb paracaktuar.
\nP\u00ebr organizimin e ekzekutimit t\u00eb kodit n\u00eb distanc\u00eb gjat\u00eb sulmit k\u00ebrkohet q\u00eb serveri t\u00eb ket\u00eb 4GB hap\u00ebsir\u00eb t\u00eb lir\u00eb n\u00eb disk dhe 8GB RAM.
\nEksploitimi lejon ekzekutimin e \u00e7do komande shell me t\u00eb drejtat e \u00e7do p\u00ebrdoruesi n\u00eb sistem, p\u00ebrve\u00e7 root dhe p\u00ebrdoruesve sistemor\u00eb q\u00eb nuk kan\u00eb nj\u00eb n\u00ebnkatror n\u00eb katalogun \"\\\/home\" (procesi qmail-local ekzekutohet me t\u00eb drejtat e p\u00ebrdoruesit lokal, t\u00eb cilit i b\u00ebhet dor\u00ebzimi).<\/p>\n

Sulmi realizohet
\nn\u00ebp\u00ebrmjet d\u00ebrgimit t\u00eb nj\u00eb mesazhi shum\u00eb t\u00eb madh t\u00eb post\u00ebs elektronike, q\u00eb p\u00ebrfshin disa rreshta n\u00eb titull, me nj\u00eb madh\u00ebsi rreth 4GB dhe 576MB. Procesimi i nj\u00eb rreshti t\u00eb till\u00eb n\u00eb qmail-local shkakton nj\u00eb tepric\u00eb t\u00eb numrave t\u00eb plot\u00eb gjat\u00eb p\u00ebrpjekjes p\u00ebr t\u00eb dor\u00ebzuar mesazhin te p\u00ebrdoruesi lokal. Teprica e numrave t\u00eb plot\u00eb m\u00eb pas \u00e7on n\u00eb nj\u00eb tepric\u00eb t\u00eb tampon\u00ebve gjat\u00eb kopjimit t\u00eb t\u00eb dh\u00ebnave dhe mund\u00ebsin\u00eb p\u00ebr t\u00eb mbingarkuar faqet e memories me kodin libc. N\u00ebp\u00ebrmjet manipulimeve me p\u00ebrb\u00ebrjen e t\u00eb dh\u00ebnave t\u00eb d\u00ebrguara, \u00ebsht\u00eb e mundur gjithashtu t\u00eb shkruhet adresa e funksionit \"open()\", duke e z\u00ebvend\u00ebsuar at\u00eb me adres\u00ebn e funksionit \"system()\". <\/p>\n

M\u00eb pas, gjat\u00eb procesit t\u00eb thirrjes qmesearch() n\u00eb qmail-local, hapet skedari \".qmail-extension\" p\u00ebrmes funksionit open(), q\u00eb \u00e7on n\u00eb ekzekutimin e funksionit
\nsystem(\".qmail-extension\"). Por duke qen\u00eb se pjesa e skedarit \"extension\" krijohet n\u00eb baze t\u00eb adres\u00ebs s\u00eb marr\u00ebsit (p.sh. \"localuser-extension@localdomain\"), sulmuesit mund t\u00eb organizojn\u00eb transferimin e komand\u00ebs p\u00ebr ekzekutim, duke specifikuar p\u00ebrdoruesin \"localuser-;command;@localdomain\" si marr\u00ebs t\u00eb mesazhit. <\/p>\n

Gjat\u00eb analiz\u00ebs s\u00eb kodit, u identifikuan gjithashtu dy vulnerabilitete n\u00eb patch-in shtes\u00eb qmail-verify, q\u00eb b\u00ebn pjes\u00eb n\u00eb paketin p\u00ebr Debian. Vulnerabiliteti i par\u00eb (CVE-2020-3811<\/a><\/noindex>) lejon t\u00eb anashkalohet verifikimi i adres\u00ebs s\u00eb email-it, nd\u00ebrsa i dyti (CVE-2020-3812<\/a><\/noindex>) \u00e7on n\u00eb rrjedhjen e informacionit lokal. N\u00eb ve\u00e7anti, vulnerabiliteti i par\u00eb lejon kalimin e verifikimit t\u00eb sakt\u00ebsis\u00eb s\u00eb adres\u00ebs, e cila p\u00ebrdoret n\u00eb eksploit p\u00ebr d\u00ebrgimin e komand\u00ebs (verifikimi nuk funksionon p\u00ebr adresat pa domene, t\u00eb tilla si \"localuser-;command;\"). Vulnerabiliteti i dyt\u00eb mund t\u00eb p\u00ebrdoret p\u00ebr t\u00eb kontrolluar ekzistenc\u00ebn e skedar\u00ebve dhe katalog\u00ebve n\u00eb sistem, duke p\u00ebrfshir\u00eb ato q\u00eb jan\u00eb t\u00eb disponuesh\u00ebm vet\u00ebm p\u00ebr root (qmail-verify ekzekutohet me t\u00eb drejtat e root), p\u00ebrmes nj\u00eb qasje t\u00eb drejtp\u00ebrdrejt\u00eb te trajtuesi lokal.<\/p>\n

P\u00ebr t\u00eb zgjidhur k\u00ebt\u00eb problem, Bernstein rekomandoi t\u00eb nisen proceset qmail me vendosjen e nj\u00eb kufiri t\u00eb p\u00ebrbashk\u00ebt p\u00ebr memorien e disponueshme (\"softlimit -m12345678\"), dhe n\u00eb k\u00ebt\u00eb rast problemi bllokohet. Si nj\u00eb m\u00ebnyr\u00eb alternative mbrojtjeje, p\u00ebrmendet gjithashtu kufizimi i madh\u00ebsis\u00eb maksimale t\u00eb mesazhit t\u00eb p\u00ebrpunuar p\u00ebrmes skedarit \"control\/databytes\" (me default nuk krijohet dhe me konfigurimet standarde qmail mbetet i ekspozuar). P\u00ebr m\u00eb tep\u00ebr, \"control\/databytes\" nuk mbron nga sulmet lokale nga p\u00ebrdoruesit e sistemit, pasi kufizimi merret parasysh vet\u00ebm n\u00eb qmail-smtpd.<\/p>\n

Problemi prek paketin netqmail<\/a><\/noindex>, i p\u00ebrfshir\u00eb n\u00eb depozitat Debian. P\u00ebr k\u00ebt\u00eb paket\u00eb \u00ebsht\u00eb p\u00ebrgatitur nj\u00eb grup patch-esh q\u00eb eliminojn\u00eb jo vet\u00ebm vulnerabilitetet e vjetra nga viti 2005 (n\u00ebp\u00ebrmjet shtimit n\u00eb kodin e funksionit alloc() t\u00eb kufizimeve t\u00eb forta p\u00ebr memorien), por gjithashtu \u00e7\u00ebshtje t\u00eb reja n\u00eb qmail-verify. Ve\u00e7mas \u00ebsht\u00eb p\u00ebrgatitur<\/a><\/noindex> varianti i azhurnuar i patch-it qmail-verify. Zhvilluesit dega<\/a><\/noindex> notqmail<\/a><\/noindex> p\u00ebrgatit\u00ebn patch-et e tyre p\u00ebr bllokimin e problemeve t\u00eb vjetra, dhe gjithashtu filluan pun\u00ebn p\u00ebr t'i eliminuar t\u00eb gjitha mbushjet e mundshme t\u00eb numrave n\u00eb kod.<\/p>\n

<\/a><\/noindex><\/p>\n

Burimi: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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