{"id":93917,"date":"2020-09-11T01:41:59","date_gmt":"2020-09-10T23:41:59","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh"},"modified":"2020-09-11T01:41:59","modified_gmt":"2020-09-10T23:41:59","slug":"uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sq\/blog\/news\/uyazvimost-v-tls-dopuskayushhaya-opredelenie-klyucha-dlya-soedinenij-na-baze-shifrov-dh","title":{"rendered":"Nj\u00eb dob\u00ebsi n\u00eb TLS, e cila lejon p\u00ebrcaktimin e \u00e7el\u00ebsit p\u00ebr lidhjet bazuar n\u00eb kriptimin DH","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Zbulimi<\/a><\/noindex> informacione mbi nj\u00eb mang\u00ebsive<\/a><\/noindex> (CVE-2020-1968) n\u00eb protokollin TLS, i njohur si
\nRaccoon<\/a><\/noindex> dhe q\u00eb lejon, n\u00eb rrethana t\u00eb rralla, p\u00ebrcaktimin e \u00e7el\u00ebsit fillestar (pre-master), i cili mund t\u00eb p\u00ebrdoret p\u00ebr t\u00eb dekriptuar lidhje TLS, p\u00ebrfshir\u00eb HTTPS, gjat\u00eb kapjes s\u00eb trafikut n\u00eb tranzit (MITM). Sh\u00ebnohet se sulmi \u00ebsht\u00eb shum\u00eb i komplikuar p\u00ebr t'u realizuar praktikisht dhe ka nj\u00eb karakter m\u00eb shum\u00eb teorik. P\u00ebr t\u00eb kryer sulmin k\u00ebrkohet nj\u00eb konfigurim specifik i serverit TLS dhe mund\u00ebsia e matjes shum\u00eb t\u00eb sakt\u00eb t\u00eb koh\u00ebs s\u00eb procesimit nga serveri.<\/p>\n

Problemi \u00ebsht\u00eb i pranish\u00ebm direkt n\u00eb specifikimin TLS dhe ndikon vet\u00ebm n\u00eb lidhjet q\u00eb p\u00ebrdorin kodet t\u00eb bazuara n\u00eb protokollin e shk\u00ebmbimit t\u00eb \u00e7el\u00ebsit DH (Diffie-Hellman, TLS_DH_*). Me kodet ECDH, problemi nuk shfaqet dhe ato mbeten t\u00eb sigurta. Vet\u00ebm protokollet TLS deri n\u00eb versionin 1.2 p\u00ebrfshir\u00eb jan\u00eb t\u00eb ndjesh\u00ebm, nd\u00ebrsa protokolli TLS 1.3 nuk \u00ebsht\u00eb i ekspozuar ndaj k\u00ebsaj probleme. Ndjeshm\u00ebria shfaqet n\u00eb implementimet TLS q\u00eb rip\u00ebrdorin \u00e7el\u00ebsin sekret DH n\u00eb lidhje t\u00eb ndryshme TLS (nj\u00eb sjellje e till\u00eb v\u00ebrehet n\u00eb rreth 4.4% t\u00eb server\u00ebve nga renditja Alexa Top 1M).<\/p>\n

N\u00eb OpenSSL 1.0.2e dhe versionet m\u00eb t\u00eb hershme, \u00e7el\u00ebsi primar DH rip\u00ebrdoret n\u00eb t\u00eb gjitha lidhjet e serverit, n\u00ebse nuk \u00ebsht\u00eb eksplicitisht e vendosur opsioni SSL_OP_SINGLE_DH_USE. Duke filluar nga OpenSSL 1.0.2f, \u00e7el\u00ebsi primar DH rip\u00ebrdoret vet\u00ebm kur p\u00ebrdoren kodet DH statike (\"DH-*\", p\u00ebr shembull \"DH-RSA-AES256-SHA\"). N\u00eb OpenSSL 1.1.1, ndjeshm\u00ebria nuk shfaqet, pasi n\u00eb k\u00ebt\u00eb deg\u00eb \u00e7el\u00ebsi primar DH nuk p\u00ebrdoret dhe nuk aplikohet kodet DH statike. <\/p>\n

Kur p\u00ebrdoret metoda e shk\u00ebmbimit t\u00eb \u00e7el\u00ebsit DH, t\u00eb dyja pal\u00ebt e lidhjes gjenerojn\u00eb \u00e7el\u00ebsa t\u00eb rast\u00ebsish\u00ebm t\u00eb mbyllur (t\u00eb njohur si \u00e7el\u00ebsi \"a\" dhe \u00e7el\u00ebsi \"b\"), mbi baz\u00ebn e t\u00eb cil\u00ebve llogariten dhe d\u00ebrgohen \u00e7el\u00ebsa publik\u00eb (ga mod p dhe gb mod p). Pas marrjes s\u00eb \u00e7el\u00ebsave publik\u00eb nga secila pal\u00eb, llogaritet \u00e7el\u00ebsi primar i p\u00ebrbashk\u00ebt (gab mod p), i cili p\u00ebrdoret p\u00ebr t\u00eb formuar \u00e7el\u00ebsa seanc\u00eb. Sulmi Raccoon lejon p\u00ebrcaktimin e \u00e7el\u00ebsit primar p\u00ebrmes analiz\u00ebs s\u00eb informacionit p\u00ebrmes kanaleve t\u00eb tjera, duke u mb\u00ebshtetur n\u00eb faktin se n\u00eb specifikimet TLS deri n\u00eb versionin 1.2 parashihet q\u00eb t\u00eb hidhen t\u00eb gjitha bajt\u00ebt fillestar\u00eb zero t\u00eb \u00e7el\u00ebsit primar p\u00ebrpara se t\u00eb kryhen llogaritjet me t\u00eb.<\/p>\n

P\u00ebrfshir\u00eb nj\u00eb \u00e7el\u00ebs primar t\u00eb reduktuar kalon n\u00eb funksionin e gjenerimit t\u00eb \u00e7el\u00ebsit t\u00eb sesionit, i bazuar n\u00eb funksione hash me vonesa t\u00eb ndryshme gjat\u00eb p\u00ebrpunimit t\u00eb t\u00eb dh\u00ebnave t\u00eb ndryshme. Matjet e sakta t\u00eb koh\u00ebs s\u00eb operacioneve t\u00eb kryera nga serveri me \u00e7el\u00ebsin lejojn\u00eb sulmuesin t\u00eb p\u00ebrcaktoj\u00eb sugjerime (oracle), q\u00eb ofrojn\u00eb mund\u00ebsin\u00eb t\u00eb gjykohet n\u00ebse \u00e7el\u00ebsi primar fillon me zero apo jo. P\u00ebr shembull, sulmuesi mund t\u00eb kap\u00eb \u00e7el\u00ebsin publik t\u00eb d\u00ebrguar nga klienti (ga), ta p\u00ebrcjell\u00eb s\u00ebrish at\u00eb n\u00eb server dhe t\u00eb p\u00ebrcaktoj\u00eb
\nn\u00ebse \u00e7el\u00ebsi primar rezultues fillon me zero.<\/p>\n

Vet\u00ebm p\u00ebrcaktimi i nj\u00eb bajti t\u00eb \u00e7el\u00ebsit nuk jep asgj\u00eb, por duke kapur vler\u00ebn e \"ga\" t\u00eb d\u00ebrguar gjat\u00eb pajtimit t\u00eb lidhjes nga klienti, sulmuesi mund t\u00eb formoj\u00eb nj\u00eb grup vlerash t\u00eb tjera q\u00eb lidhen me \"ga\" dhe t'i d\u00ebrgoj\u00eb ato n\u00eb server n\u00eb seanca t\u00eb ndryshme pajtimi t\u00eb lidhjes. Duke formuar dhe d\u00ebrguar vlerat \"gri*ga\", sulmuesi mund, p\u00ebrmes analiz\u00ebs s\u00eb ndryshimeve n\u00eb vonesat e p\u00ebrgjigjeve t\u00eb serverit, t\u00eb p\u00ebrcaktoj\u00eb vlerat q\u00eb \u00e7ojn\u00eb n\u00eb marrjen e \u00e7el\u00ebsave primar\u00eb q\u00eb fillojn\u00eb me zero. Duke p\u00ebrcaktuar vlera t\u00eb tilla, sulmuesi mund t\u00eb krijoj\u00eb nj\u00eb grup ekuacionesh p\u00ebr zgjidhjen<\/a><\/noindex> e problemi t\u00eb numrave t\u00eb fshehur<\/a><\/noindex> dhe t\u00eb llogaris\u00eb \u00e7el\u00ebsin primar origjinal. <\/p>\n

\"Nj\u00eb<\/center><\/p>\n

N\u00eb OpenSSL, dob\u00ebsit\u00eb i \u00ebsht\u00eb caktuar<\/a><\/noindex> nivel i ul\u00ebt rreziku, dhe korrigjimi u reduktua n\u00eb zhvendosjen n\u00eb versionin 1.0.2w t\u00eb cifrave problematike «TLS_DH_*» n\u00eb kategorin\u00eb e \u00e7ifrave me nivele t\u00eb pamjaftueshme mbrojtjeje q\u00eb \u00ebsht\u00eb e \u00e7aktivizuar si projektimi i parazgjedhur («weak-ssl-ciphers»). Po ashtu vepruan zhvilluesit e Mozilla-s, t\u00eb cil\u00ebt \u00e7aktivizuan<\/a><\/noindex> n\u00eb bibliotek\u00ebn NSS, e p\u00ebrdorur n\u00eb Firefox, grupet e kriptimit DH dhe DHE. Duke filluar nga Firefox 78, algoritmet problematike jan\u00eb \u00e7aktivizuar. N\u00eb Chrome, mb\u00ebshtetja p\u00ebr DH u nd\u00ebrpre p\u00ebrs\u00ebri n\u00eb vitin 2016. Bibliotekat BearSSL, BoringSSL, Botan, Mbed TLS dhe s2n nuk jan\u00eb t\u00eb prekura nga problemi, pasi nuk mb\u00ebshtesin algoritmet DH ose variantet statike t\u00eb algoritmeve DH. <\/p>\n

Ve\u00e7an\u00ebrisht theksohen problemet shtes\u00eb (CVE-2020-5929<\/a><\/noindex>) n\u00eb stek\u00ebt TLS t\u00eb pajisjeve F5 BIG-IP, duke e b\u00ebr\u00eb sulmin m\u00eb realista. N\u00eb ve\u00e7anti, jan\u00eb identifikuar devijime n\u00eb sjelljen e pajisjeve kur ka nj\u00eb bajt t\u00eb zer\u00ebs n\u00eb fillim t\u00eb \u00e7el\u00ebsit primar, t\u00eb cilat mund t\u00eb p\u00ebrdoren n\u00eb vend t\u00eb matjes s\u00eb sakt\u00eb t\u00eb koh\u00ebs s\u00eb vones\u00ebs gjat\u00eb llogaritjeve.<\/p>\n

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

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

\u0420\u0430\u0441\u043a\u0440\u044b\u0442\u044b \u0441\u0432\u0435\u0434\u0435\u043d\u0438\u044f \u043e \u043d\u043e\u0432\u043e\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 (CVE-2020-1968) \u0432 \u043f\u0440\u043e\u0442\u043e\u043a\u043e\u043b\u0435 TLS, \u043f\u043e\u043b\u0443\u0447\u0438\u0432\u0448\u0435\u0439 \u043a\u043e\u0434\u043e\u0432\u043e\u0435 \u0438\u043c\u044f Raccoon \u0438 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 \u043f\u0440\u0438 \u0440\u0435\u0434\u043a\u043e\u043c \u0441\u0442\u0435\u0447\u0435\u043d\u0438\u0438 \u043e\u0431\u0441\u0442\u043e\u044f\u0442\u0435\u043b\u044c\u0441\u0442\u0432 \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0438\u0442\u044c \u043f\u0440\u0435\u0434\u0432\u0430\u0440\u0438\u0442\u0435\u043b\u044c\u043d\u044b\u0439 \u043f\u0435\u0440\u0432\u0438\u0447\u043d\u044b\u0439 \u043a\u043b\u044e\u0447 (pre-master), \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043c\u043e\u0436\u043d\u043e \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u044c \u0434\u043b\u044f \u0440\u0430\u0441\u0448\u0438\u0444\u0440\u043e\u0432\u043a\u0438 TLS-\u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u0439, \u0432 \u0442\u043e\u043c \u0447\u0438\u0441\u043b\u0435 HTTPS, \u043f\u0440\u0438 \u043f\u0435\u0440\u0435\u0445\u0432\u0430\u0442\u0435 \u0442\u0440\u0430\u043d\u0437\u0438\u0442\u043d\u043e\u0433\u043e \u0442\u0440\u0430\u0444\u0438\u043a\u0430 (MITM). \u041e\u0442\u043c\u0435\u0447\u0430\u0435\u0442\u0441\u044f, \u0447\u0442\u043e \u0430\u0442\u0430\u043a\u0430 \u043e\u0447\u0435\u043d\u044c \u0441\u043b\u043e\u0436\u043d\u0430 \u0434\u043b\u044f \u043f\u0440\u0430\u043a\u0442\u0438\u0447\u0435\u0441\u043a\u043e\u0439 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u0438 \u0438 \u0431\u043e\u043b\u044c\u0448\u0435 \u043d\u043e\u0441\u0438\u0442 \u0442\u0435\u043e\u0440\u0435\u0442\u0438\u0447\u0435\u0441\u043a\u0438\u0439 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