{"id":111506,"date":"2023-11-14T21:10:14","date_gmt":"2023-11-14T19:10:14","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/vossozdanie-rsa-klyuchej-cherez-analiz-ssh-soedinenij-k-sbojnym-serveram"},"modified":"2023-11-14T21:10:14","modified_gmt":"2023-11-14T19:10:14","slug":"vossozdanie-rsa-klyuchej-cherez-analiz-ssh-soedinenij-k-sbojnym-serveram","status":"publish","type":"post","link":"https:\/\/prohoster.info\/ro\/blog\/news\/vossozdanie-rsa-klyuchej-cherez-analiz-ssh-soedinenij-k-sbojnym-serveram","title":{"rendered":"Recrearea cheilor RSA prin analiza conexiunilor SSH la servere cu erori","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Un grup de cercet\u0103tori de la Universitatea din California, San Diego, a demonstrat posibilitatea reconstruc\u021biei cheilor RSA private ale serverelor SSH prin analiza pasiv\u0103 a traficului SSH. Atacul poate fi realizat asupra serverelor care, din cauza circumstan\u021belor sau ac\u021biunilor atacatorului, sufer\u0103 erori \u00een timpul calculului semn\u0103turii digitale la stabilirea unei conexiuni SSH. Erorile pot fi at\u00e2t software (executarea incorect\u0103 a opera\u021biunilor matematice, deteriorarea memoriei), c\u00e2t \u0219i hardware (erori \u00een func\u021bionarea NVRAM \u0219i DRAM sau erori cauzate de \u00eentreruperile de alimentare). <\/p>\n

Una dintre modalit\u0103\u021bile de stimulare a erorilor ar putea fi atacurile de tip RowHammer, care imprim\u0103, printre altele, capacitatea de a provoca distorsiuni \u00een con\u021binutul unor bi\u021bi de memorie prin citirea intens\u0103 \u0219i ciclic\u0103 a datelor din celule adiacente, fie de la distan\u021b\u0103, fie prin procesarea codului JavaScript \u00een browser. O alt\u0103 modalitate de provocare a erorilor ar putea fi exploatarea vulnerabilit\u0103\u021bilor care duc la suprascrierea memoriei \u0219i deteriorarea datelor cu cheile \u00een memorie. <\/p>\n

Studiul publicat arat\u0103 c\u0103, atunci c\u00e2nd se folosesc semn\u0103turi digitale \u00een SSH bazate pe algoritmul RSA, atacurile de reconstruc\u021bie a cheilor RSA folosind metoda Lattice (Fault Attack) sunt aplicabile parametrelor semn\u0103turii digitale, \u00een cazul \u00een care apar erori software sau hardware \u00een timpul procesului de calcul al semn\u0103turii. Esen\u021ba metodei este c\u0103, compar\u00e2nd semn\u0103turile digitale RSA corecte \u0219i defecte, se poate determina cel mai mare divizor comun pentru a ob\u021bine unul dintre numerele prime utilizate la formarea cheii. <\/p>\n

La baza cript\u0103rii RSA st\u0103 opera\u021bia de ridicare la putere modulo unui num\u0103r mare. \u00cen cheia public\u0103 se afl\u0103 modul \u0219i puterea. Modulul este format din dou\u0103 numere prime aleatorii, cunoscute doar proprietarului cheii private. Atacul poate fi aplicat implement\u0103rilor RSA care utilizeaz\u0103 Teorema Chinez\u0103 a Resturilor \u0219i scheme de umplere determinate, cum ar fi PKCS#1 v1.5. <\/p>\n

Pentru a efectua un atac, este suficient s\u0103 urm\u0103re\u0219ti \u00een mod pasiv conexiunile legitime la serverul SSH p\u00e2n\u0103 c\u00e2nd se identific\u0103 \u00een trafic o semn\u0103tur\u0103 digital\u0103 defectuoas\u0103, care poate fi utilizat\u0103 ca surs\u0103 de informa\u021bii pentru a recrea cheia RSA privat\u0103. Dup\u0103 ce cheia RSA a gazdei este recreat\u0103, atacatorul poate redirec\u021biona f\u0103r\u0103 a fi observat cererile c\u0103tre un gazd\u0103 fals\u0103 care se pretinde a fi un server SSH compromis \u0219i poate intercepta datele transmise pe aceasta. serverul<\/a> de date. <\/p>\n

\u00cen urma studiului unei colec\u021bii de date de re\u021bea interceptate, care include aproximativ 5,2 miliarde de \u00eenregistr\u0103ri legate de utilizarea protocolului SSH, cercet\u0103torii au identificat aproximativ 3,2 miliarde de chei de gazd\u0103 deschise \u0219i semn\u0103turi digitale utilizate \u00een timpul negocierii sesiunii SSH. Dintre acestea, 1,2 miliarde (39,1%) au fost generate folosind algoritmul RSA. \u00cen 593671 de cazuri (0,048%), semn\u0103tura RSA a fost compromis\u0103 \u0219i nu a trecut verificarea. Pentru 4962 de semn\u0103turi defectuoase, a fost aplicat\u0103 metoda de factorizare a re\u021belelor pentru a determina cheia privat\u0103 pe baza cheii publice cunoscute, ceea ce a dus \u00een final la recrearea a 189 de perechi unice de chei RSA (\u00een multe cazuri, pentru generarea diferitelor semn\u0103turi defectuoase au fost utilizate acelea\u0219i chei \u0219i dispozitive defectuoase). Recrearea cheilor a necesitat aproximativ 26 de ore de timp de procesor.

\"Recrearea<\/center> <\/p>\n

Problema afecteaz\u0103 doar implement\u0103rile specifice ale protocolului SSH, utilizate \u00een principal pe dispozitive \u00eencorporate. Printre exemplele de dispozitive cu implement\u0103ri problematice ale SSH se num\u0103r\u0103 produsele Zyxel, Cisco, Mocana \u0219i Hillstone Networks. OpenSSH nu este afectat de aceast\u0103 problem\u0103, deoarece utilizeaz\u0103 pentru generarea cheilor biblioteca OpenSSL (sau LibreSSL), care are protec\u021bie \u00eempotriva atacurilor bazate pe analiza defectelor (Fault Attack) din 2001. Mai mult, \u00een OpenSSH, schema de semn\u0103turi digitale ssh-rsa (bazat\u0103 pe sha1) a fost declarat\u0103 \u00eenvechit\u0103 \u00eencep\u00e2nd cu 2020 \u0219i a fost dezactivat\u0103 \u00een versiunea 8.8 (se men\u021bin schemele rsa-sha2-256 \u0219i rsa-sha2-512). Poten\u021bial, atacul ar putea fi aplicabil \u0219i pentru protocolul IPsec, dar cercet\u0103torii nu aveau suficiente date experimentale pentru a confirma un astfel de atac \u00een practic\u0103.
\n
Sursa: opennet.ro<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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[…]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":111507,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-111506","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\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\n","aioseo_head_json":{"title":"\ud83e\udd47Recrearea cheilor RSA prin analiza conexiunilor SSH c\u0103tre serverele e\u0219uate | ProHoster","description":"Un grup de cercet\u0103tori de la Universitatea din California, San Diego, a demonstrat posibilitatea recre\u0103rii cheilor secret RSA ale gazdei serverului SSH, utiliz\u00e2nd analiza pasiv\u0103 a traficului 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