{"id":37225,"date":"2019-10-31T22:16:26","date_gmt":"2019-10-31T19:16:26","guid":{"rendered":"https:\/\/prohoster.info\/blog\/ataka-knob-pozvolyayushhaya-perehvatit-zashifrovannyj-trafik-bluetooth\/"},"modified":"2019-10-31T22:16:26","modified_gmt":"2019-10-31T19:16:26","slug":"ataka-knob-pozvolyayushhaya-perehvatit-zashifrovannyj-trafik-bluetooth","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/news\/ataka-knob-pozvolyayushhaya-perehvatit-zashifrovannyj-trafik-bluetooth","title":{"rendered":"KNOB-angreb, der muligg\u00f8r opsnapning af krypteret Bluetooth-trafik","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Afsl\u00f8rede<\/a><\/noindex> oplysninger<\/a><\/noindex> om angrebet KNOB<\/a><\/noindex> (Key Negotiation Of Bluetooth), der muligg\u00f8r interception og indspr\u00f8jtning af information i krypteret Bluetooth-trafik. Hvis angriberen har mulighed for at blokere den direkte transmission af pakker under Bluetooth-enhedernes forbindelsesforhandling, kan de opn\u00e5 brug af sessionn\u00f8gler, der kun indeholder 1 byte entropi, hvilket g\u00f8r det muligt at anvende en brute-force metode til at bestemme krypteringsn\u00f8glen. <\/p>\n

Problemet er for\u00e5rsaget af mangler (CVE-2019-9506) i Bluetooth BR\/EDR Core-specifikationen 5.1 og tidligere versioner, som tillader brug af alt for korte krypteringsn\u00f8gler og ikke forhindrer en angriber i at intervenere under forbindelsesforhandlingen for at falde tilbage til s\u00e5danne usikre n\u00f8gler (indspr\u00f8jtning af pakker kan udf\u00f8res af ikke-godkendte angribere). Angrebet kan udf\u00f8res under forbindelsesforhandlingen mellem enheder (allerede etablerede sessioner kan ikke angribes) og er kun effektivt for forbindelser i BR\/EDR tilstande (Bluetooth Basic Rate\/Enhanced Data Rate), hvis begge enheder er s\u00e5rbare. I tilf\u00e6lde af en vellykket n\u00f8glegennembrud kan angriberen dekryptere de overf\u00f8rte data og diskret udf\u00f8re indspr\u00f8jtning i trafikken af vilk\u00e5rlig krypteret tekst.<\/p>\n

Ved etablering af en forbindelse mellem to Bluetooth-controllere A og B kan controller A efter autentificering via forbindelsestasten (link key) foresl\u00e5 at bruge 16 byte entropi til krypteringsn\u00f8glen (encryption key), og controller B kan acceptere dette v\u00e6rdi eller angive en lavere v\u00e6rdi, hvis den ikke har mulighed for at danne en n\u00f8gle af den foresl\u00e5ede st\u00f8rrelse. I svaret kan controller A acceptere det modtagne forslag og aktivere den krypterede kommunikationskanal. P\u00e5 dette tidspunkt anvendes der ikke kryptering under parametre-signering, hvilket giver angriberen mulighed for at intervere i dataudvekslingen mellem controllere og inds\u00e6tte en pakke med den foresl\u00e5ede entropist\u00f8rrelse. Da den acceptable n\u00f8glest\u00f8rrelse varierer fra 1 til 16 byte, vil den anden controller acceptere dette v\u00e6rdi og sende sin bekr\u00e6ftelse med angivelse af en tilsvarende st\u00f8rrelse.<\/p>\n

\"KNOB-angreb,<\/a><\/noindex><\/center><\/p>\n

For at genskabe s\u00e5rbarheden under laboratorieforhold (angriberens aktivitet blev emuleret p\u00e5 en af enhederne) er der foresl\u00e5et
\net prototypev\u00e6rkt\u00f8j<\/a><\/noindex> til at udf\u00f8re et angreb.
\nFor et reelt angreb skal angriberen befinde sig inden for r\u00e6kkevidde af ofrenes enheder og have mulighed for midlertidigt at blokere signalet fra hver enhed, hvilket foresl\u00e5s at opn\u00e5 ved at manipulere signalet eller ved aktiv st\u00f8jundertryk. <\/p>\n

Bluetooth SIG-organisationen, som er ansvarlig for udviklingen af Bluetooth-standarder, offentliggjorde<\/a><\/noindex> tilpasning af specifikationen under nummer 11838, hvori der foresl\u00e5s foranstaltninger til producenterne for at lukke sikkerhedshullerne (den minimale st\u00f8rrelse af krypteringsn\u00f8glen er forh\u00f8jet fra 1 til 7). Problemet optr\u00e6der<\/a><\/noindex> ligger i af alle<\/a><\/noindex> de relevante Bluetooth-stakke og Bluetooth-chipfirmwares, herunder produkter Intel<\/a><\/noindex>, Broadcom, Lenovo<\/a><\/noindex>, Apple<\/a><\/noindex>, Microsoft<\/a><\/noindex>, Qualcomm, Linux, Android<\/a><\/noindex>, Blackberry<\/a><\/noindex> og Cisco<\/a><\/noindex> (af 14 testede chips var alle s\u00e5rbare). I Linux-kernens Bluetooth-stak er implementeret<\/a><\/noindex> rettelsen, der muligg\u00f8r \u00e6ndring af den minimale st\u00f8rrelse af krypteringsn\u00f8glen. <\/p>\n

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

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

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