{"id":100784,"date":"2021-07-17T22:22:35","date_gmt":"2021-07-17T20:22:35","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare"},"modified":"2021-07-17T22:22:35","modified_gmt":"2021-07-17T20:22:35","slug":"uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/news\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","title":{"rendered":"S\u00e5rbarhed i cdnjs, der gjorde det muligt at udf\u00f8re kode p\u00e5 Cloudflare-servere.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I det netv\u00e6rk af indholdlevering, som Cloudflare tilbyder gennem cdnjs, der er designet til at fremskynde levering af JavaScript-biblioteker, er der blevet fundet en kritisk s\u00e5rbarhed, der muligg\u00f8r udf\u00f8relse af vilk\u00e5rlig kode p\u00e5 CDN-servere. Problemet forv\u00e6rres af det faktum, at omkring 12,7% af alle hjemmesider p\u00e5 internettet bruger tjenesten til at indl\u00e6se JavaScript-biblioteker, og en kompromittering af infrastrukturen muligg\u00f8r, at bibliotekerne, der leveres af disse hjemmesider, kan blive \u00e6ndret. <\/p>\n

Tjenesten cdnjs henter pakker fra Git eller NPM-repositoriet og giver enhver hjemmeside mulighed for gratis at drage fordel af Cloudflares content delivery network for at fremskynde indl\u00e6sningen af JavaScript-biblioteker. Ved gennemgang af koden til cdnjs-komponenterne, publiceret p\u00e5 GitHub, blev det opdaget, at der anvendes den indbyggede archive\/tar-modul p\u00e5 Go-sprog til at udpakkede NPM-pakker i tgz-arkiver, som returnerer filerne som de er, uden normalisering af stier. I tilf\u00e6lde af at scriptet udpakker indholdet baseret p\u00e5 den udleverede liste, kan tilstedev\u00e6relsen af filer i arkivet som \u00ab.. \/ .. \/ .. \/ .. \/ .. \/ .. \/ .. \/ tmp \/ test\u00bb f\u00f8re til overskrivning af vilk\u00e5rlige filer i systemet, afh\u00e6ngigt af adgangsrettighederne. <\/p>\n

Det blev antaget, at en angriber kan ans\u00f8ge om at tilf\u00f8je sin bibliotek til cdnjs og uploade et specielt tilrettelagt arkiv til NPM-repositoriet, der indeholder filer med tegnene \u00ab.. \/\u00bb i stien. P\u00e5 cdnjs-serverne udf\u00f8res operationen \u00abautoupdate\u00bb periodisk, hvor h\u00e5ndtereren downloader nye versioner af det foresl\u00e5ede bibliotek og udpakkede indholdet. Ved hj\u00e6lp af filer med stierne \u00ab.. \/\u00bb kan angriberen opn\u00e5 overskrivning af filer med service-scripts og udf\u00f8re sin kode p\u00e5. serveren<\/a> den, hvor udpakkingen fandt sted. <\/p>\n

I tilf\u00e6lde af opdateringer fra Git blev det p\u00e5vist, at den handler, der indl\u00e6ser opdateringer, ikke tog h\u00f8jde for symbolske links, n\u00e5r filer blev kopieret fra Git. Denne funktionalitet gjorde det muligt at l\u00e6se vilk\u00e5rlige filer med server<\/a> ved at tilf\u00f8je symbolske links til Git. <\/p>\n

Eksperimenter med at demonstrere angreb p\u00e5 cdnjs for at opn\u00e5 bel\u00f8nning p\u00e5 HackerOne blev besluttet at starte med at teste hypotesen om l\u00e6sning af filer. Der blev tilf\u00f8jet et symbolsk link test.js til Git-repositoriet for den JavaScript-bibliotek, der blev leveret via CDN, som pegede p\u00e5 filen \/proc\/self\/maps. Efter offentligg\u00f8relsen af en ny version af biblioteket behandlede opdateringshandleren dette repository og offentliggjorde den angivne fil i cdnjs (test.js blev oprettet som et symbolsk link, og ved anmodning om denne fil blev indholdet af \/proc\/self\/maps vist). <\/p>\n

Ved at s\u00e6tte et symbolsk link til filen \/proc\/self\/environ bem\u00e6rkede forskeren, at der indeni de returnerede data var v\u00e6rdierne for milj\u00f8variablerne GITHUB_REPO_API_KEY og WORKERS_KV_API_TOKEN. Den f\u00f8rste variabel indeholdt en API-n\u00f8gle til skriverettigheder i repositoryet robocdnjs p\u00e5 GitHub. I den anden variabel var der en token til KV-lageret i cdnjs. Ved at udnytte de opn\u00e5ede oplysninger kunne angriberen foretage \u00e6ndringer i cdnjs og fuldst\u00e6ndig kompromittere infrastrukturen.
\n
Kilde: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u043f\u0440\u0435\u0434\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u043c\u043e\u0439 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0435\u0439 Cloudflare \u0441\u0435\u0442\u0438 \u0434\u043e\u0441\u0442\u0430\u0432\u043a\u0438 \u043a\u043e\u043d\u0442\u0435\u043d\u0442\u0430 cdnjs, \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u043d\u043e\u0439 \u0434\u043b\u044f \u0443\u0441\u043a\u043e\u0440\u0435\u043d\u0438\u044f \u0434\u043e\u0441\u0442\u0430\u0432\u043a\u0438 JavaScript-\u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u043a\u0440\u0438\u0442\u0438\u0447\u0435\u0441\u043a\u0430\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0438\u0442\u044c \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u043b\u044c\u043d\u044b\u0439 \u043a\u043e\u0434 \u043d\u0430 \u0441\u0435\u0440\u0432\u0435\u0440\u0430\u0445 CDN. \u041e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u044c \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0443\u0441\u0443\u0433\u0443\u0431\u043b\u044f\u0435\u0442\u0441\u044f \u0442\u0435\u043c, \u0447\u0442\u043e \u0434\u043b\u044f \u0437\u0430\u0433\u0440\u0443\u0437\u043a\u0438 JavaScript-\u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a \u0441\u0435\u0440\u0432\u0438\u0441\u043e\u043c \u043f\u043e\u043b\u044c\u0437\u0443\u0435\u0442\u0441\u044f \u043e\u043a\u043e\u043b\u043e 12.7% \u0432\u0441\u0435\u0445 \u0441\u0430\u0439\u0442\u043e\u0432 \u0432 \u0438\u043d\u0442\u0435\u0440\u043d\u0435\u0442\u0435 \u0438 \u043a\u043e\u043c\u043f\u0440\u043e\u043c\u0435\u0442\u0430\u0446\u0438\u044f \u0438\u043d\u0444\u0440\u0430\u0441\u0442\u0440\u0443\u043a\u0442\u0443\u0440\u044b \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u043f\u043e\u0434\u043c\u0435\u043d\u0438\u0442\u044c \u0431\u0438\u0431\u043b\u0438\u043e\u0442\u0435\u043a\u0438, \u043e\u0442\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u0435 \u043b\u044e\u0431\u044b\u043c \u0438\u0437 \u044d\u0442\u0438\u0445 \u0441\u0430\u0439\u0442\u043e\u0432. \u0421\u0435\u0440\u0432\u0438\u0441 cdnjs \u043e\u0441\u0443\u0449\u0435\u0441\u0442\u0432\u043b\u044f\u0435\u0442 \u0437\u0430\u0433\u0440\u0443\u0437\u043a\u0443 \u043f\u0430\u043a\u0435\u0442\u043e\u0432 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