{"id":35396,"date":"2019-10-31T22:04:04","date_gmt":"2019-10-31T19:04:04","guid":{"rendered":"https:\/\/prohoster.info\/blog\/uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii\/"},"modified":"2019-10-31T22:04:04","modified_gmt":"2019-10-31T19:04:04","slug":"uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hu\/blog\/news\/uyazvimosti-v-tcp-stekah-linux-i-freebsd-privodyashhie-k-udalyonnomu-otkazu-v-obsluzhivanii","title":{"rendered":"Linux \u00e9s FreeBSD TCP-stack sebezhet\u0151s\u00e9gek, amelyek t\u00e1voli szolg\u00e1ltat\u00e1smegszak\u00edt\u00e1shoz vezetnek","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Netflix c\u00e9g felt\u00e1rta<\/a><\/noindex> t\u00f6bb kritikus sebezhet\u0151s\u00e9get<\/a><\/noindex> Linux \u00e9s FreeBSD TCP-stackjeiben, amelyek lehet\u0151v\u00e9 teszik a mag \u00f6sszeoml\u00e1s\u00e1t vagy a forr\u00e1sok t\u00falzott felhaszn\u00e1l\u00e1s\u00e1t speci\u00e1lisan form\u00e1zott TCP-csomagok (packet-of-death) feldolgoz\u00e1sa sor\u00e1n. A probl\u00e9m\u00e1k a k\u00f6vetkez\u0151kb\u0151l ad\u00f3dnak<\/a><\/noindex> a TCP-csomagok maxim\u00e1lis blokkm\u00e9ret\u00e9nek (MSS, Maximum Segment Size) \u00e9s a kapcsolatok szelekt\u00edv elismer\u00e9s\u00e9nek (SACK, TCP Selective Acknowledgement) feldolgoz\u00f3iban l\u00e9v\u0151 hib\u00e1kb\u00f3l.<\/p>\n

  • CVE-2019-11477<\/a><\/noindex> (SACK Panic) \u2014 A probl\u00e9ma a Linux kerneljeiben a 2.6.29 verzi\u00f3t\u00f3l kezdve jelentkezik, \u00e9s lehet\u0151v\u00e9 teszi, hogy a kernel \u00f6sszeomoljon (panic) egy sor SACK-csomag k\u00fcld\u00e9s\u00e9vel, amelyet egy eg\u00e9sz sz\u00e1m t\u00falcsordul\u00e1s okoz a feldolgoz\u00f3ban. A t\u00e1mad\u00e1shoz elegend\u0151, ha a TCP-kapcsolat MSS \u00e9rt\u00e9k\u00e9t 48 byte-ra \u00e1ll\u00edtjuk (als\u00f3 hat\u00e1r, amely 8 byte-os szegmensm\u00e9retet hat\u00e1roz meg), \u00e9s egy bizonyos m\u00f3don \u00f6ssze\u00e1ll\u00edtott SACK-csomagsorozatot k\u00fcld\u00fcnk.\n

    A v\u00e9dekez\u00e9s lehets\u00e9ges m\u00f3djak\u00e9nt le lehet tiltani a SACK feldolgoz\u00e1st (0-t \u00edrva a \/proc\/sys\/net\/ipv4\/tcp_sack f\u00e1jlba) vagy blokkolni<\/a><\/noindex> a alacsony MSS-sel rendelkez\u0151 kapcsolatokat (ez csak akkor m\u0171k\u00f6dik, ha a sysctl net.ipv4.tcp_mtu_probing \u00e9rt\u00e9k\u00e9t 0-ra \u00e1ll\u00edtj\u00e1k, \u00e9s esetleg megzavarhat norm\u00e1l kapcsolatokat alacsony MSS-sel);<\/p>\n

  • CVE-2019-11478<\/a><\/noindex> (SACK Slowness) \u2014 A SACK mechanizmus m\u0171k\u00f6d\u00e9s\u00e9nek zavar\u00e1t okozza (Linux kernel 4.15 el\u0151tti verzi\u00f3k haszn\u00e1lata eset\u00e9n), vagy t\u00falzott er\u0151forr\u00e1s-felhaszn\u00e1l\u00e1st id\u00e9z el\u0151. A probl\u00e9ma a k\u00fcl\u00f6nlegesen form\u00e1zott SACK-csomagok feldolgoz\u00e1sa sor\u00e1n jelentkezik, amiket a TCP retransmission sorozat fragment\u00e1l\u00e1s\u00e1ra lehet haszn\u00e1lni. A v\u00e9delmi megker\u00fcl\u00e9si m\u00f3dszerek hasonl\u00f3ak az el\u0151z\u0151 sebezhet\u0151s\u00e9ghez;\n
  • CVE-2019-5599<\/a><\/noindex> (SACK Slowness) \u2014 Lehet\u0151v\u00e9 teszi a k\u00fcld\u00f6tt csomagok t\u00e9rk\u00e9p\u00e9nek fragment\u00e1l\u00e1s\u00e1t egy SACK-speci\u00e1lis sorozat feldolgoz\u00e1sa sor\u00e1n az egyes TCP-kapcsolatokban, \u00e9s er\u0151forr\u00e1s-ig\u00e9nyes lista\u00e1tf\u00e9s\u00fcl\u00e9si m\u0171veletek v\u00e9grehajt\u00e1s\u00e1t okozhatja. A probl\u00e9ma a FreeBSD 12-vel fordul el\u0151 a RACK csomagveszt\u00e9s-\u00e9szlel\u0151 mechanizmus\u00e1val. Megker\u00fcl\u00e9si megold\u00e1sk\u00e9nt a RACK modult ki lehet kapcsolni;\n
  • CVE-2019-11479<\/a><\/noindex> \u2014 A t\u00e1mad\u00f3 a Linux kernelben v\u00e1laszok t\u00f6bb TCP-szegmensre val\u00f3 feloszt\u00e1s\u00e1t id\u00e9zheti el\u0151, mindegyik 8 byte adatot tartalmaz, ami jelent\u0151s forgalomn\u00f6veked\u00e9st, CPU-terhel\u00e9s n\u00f6veked\u00e9s\u00e9t \u00e9s a kommunik\u00e1ci\u00f3s csatorna tel\u00edtetts\u00e9g\u00e9t okozhatja. Javasolt v\u00e9delmi elj\u00e1r\u00e1sk\u00e9nt blokkolni<\/a><\/noindex> alacsony MSS-sel rendelkez\u0151 kapcsolatokkal.\n<\/ul>\n

    A Linux kernelben a probl\u00e9m\u00e1k orvosl\u00e1sa a 4.4.182, 4.9.182, 4.14.127, 4.19.52 \u00e9s 5.1.11 verzi\u00f3kban t\u00f6rt\u00e9nt. A FreeBSD jav\u00edt\u00e1sa el\u00e9rhet\u0151 patch form\u00e1j\u00e1ban<\/a><\/noindex>. A disztrib\u00faci\u00f3k csomagfriss\u00edt\u00e9sei m\u00e1r kiadt\u00e1k a kernelhez Debian<\/a><\/noindex>, RHEL<\/a><\/noindex>, SUSE\/openSUSE<\/a><\/noindex>. A jav\u00edt\u00e1s el\u0151k\u00e9sz\u00edt\u00e9se folyamatban van Ubuntu<\/a><\/noindex>, Fedora<\/a><\/noindex> \u00e9s Arch Linux<\/a><\/noindex>.<\/p>\n

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

    Forr\u00e1s: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

    \u041a\u043e\u043c\u043f\u0430\u043d\u0438\u044f Netflix \u0432\u044b\u044f\u0432\u0438\u043b\u0430 \u043d\u0435\u0441\u043a\u043e\u043b\u044c\u043a\u043e \u043a\u0440\u0438\u0442\u0438\u0447\u0435\u0441\u043a\u0438\u0445 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 TCP-\u0441\u0442\u0435\u043a\u0430\u0445 Linux \u0438 FreeBSD, \u043a\u043e\u0442\u043e\u0440\u044b\u0435 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0442 \u0443\u0434\u0430\u043b\u0451\u043d\u043d\u043e \u0438\u043d\u0438\u0446\u0438\u0438\u0440\u043e\u0432\u0430\u0442\u044c \u043a\u0440\u0430\u0445 \u044f\u0434\u0440\u0430 \u0438\u043b\u0438 \u0432\u044b\u0437\u0432\u0430\u0442\u044c \u0447\u0440\u0435\u0437\u043c\u0435\u0440\u043d\u043e\u0435 \u043f\u043e\u0442\u0440\u0435\u0431\u043b\u0435\u043d\u0438\u0435 \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432 \u043f\u0440\u0438 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u0441\u043f\u0435\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u043e\u0444\u043e\u0440\u043c\u043b\u0435\u043d\u043d\u044b\u0445 TCP-\u043f\u0430\u043a\u0435\u0442\u043e\u0432 (packet-of-death). \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432\u044b\u0437\u0432\u0430\u043d\u044b \u043e\u0448\u0438\u0431\u043a\u0430\u043c\u0438 \u0432 \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430\u0445 \u043c\u0430\u043a\u0441\u0438\u043c\u0430\u043b\u044c\u043d\u043e\u0433\u043e \u0440\u0430\u0437\u043c\u0435\u0440\u0430 \u0431\u043b\u043e\u043a\u0430 \u0434\u0430\u043d\u043d\u044b\u0445 \u0432 TCP-\u043f\u0430\u043a\u0435\u0442\u0435 (MSS, Maximum segment size) \u0438 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u0432\u044b\u0431\u043e\u0440\u043e\u0447\u043d\u043e\u0433\u043e \u043f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u0438\u044f \u0441\u043e\u0435\u0434\u0438\u043d\u0435\u043d\u0438\u0439 (SACK, TCP Selective Acknowledgement). CVE-2019-11477 (SACK Panic) […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-35396","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Sebezhet\u0151s\u00e9geket tal\u00e1lt a Linux \u00e9s FreeBSD TCP-stackjeiben, amelyek t\u00e1voli szolg\u00e1ltat\u00e1smegtagad\u00e1shoz vezethetnek | ProHoster","description":"A Netflix t\u00f6bb 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