Ukukhishwa kwe-OpenSSH 8.5

Ngemva kwezinyanga ezinhlanu zokuthuthukiswa, ukukhishwa kwe-OpenSSH 8.5, ukuqaliswa okuvulekile kweklayenti kanye neseva yokusebenza phezu kwezivumelwano ze-SSH 2.0 ne-SFTP, kwethulwa.

Onjiniyela be-OpenSSH basikhumbuze ngokuyekiswa okuzayo kwama-algorithms kusetshenziswa i-SHA-1 hashes ngenxa yokwanda kokusebenza kahle kokuhlaselwa kokushayisana ngesiqalo esinikeziwe (izindleko zokukhetha ukungqubuzana zilinganiselwa cishe ku-$50 XNUMX). Kokunye okuzayo, bahlela ukukhubaza ngokuzenzakalela ikhono lokusebenzisa i-algorithm yesiginesha yedijithali yokhiye womphakathi "ssh-rsa", eshiwo ku-RFC yasekuqaleni yephrothokholi ye-SSH futhi isalokhu isabalele ekusebenzeni.

Ukuze uhlole ukusetshenziswa kwe-ssh-rsa kumasistimu akho, ungazama ukuxhuma nge-ssh ngenketho ethi “-oHostKeyAlgorithms=-ssh-rsa”. Ngesikhathi esifanayo, ukukhubaza amasiginesha edijithali "ssh-rsa" ngokuzenzakalelayo akusho ukuyeka ngokuphelele ukusetshenziswa kokhiye be-RSA, njengoba ngaphezu kwe-SHA-1, iphrothokholi ye-SSH ivumela ukusetshenziswa kwamanye ama-algorithms okubala we-hashi. Ikakhulukazi, ngaphezu kwe-"ssh-rsa", kuzohlala kungenzeka ukusebenzisa izinqwaba ze-"rsa-sha2-256" (RSA/SHA256) kanye ne-"rsa-sha2-512" (RSA/SHA512).

Ukuze kusheleleke ukushintshela kuma-algorithms amasha, i-OpenSSH 8.5 inesilungiselelo se-UpdateHostKeys esinikwe amandla ngokuzenzakalela, okuvumela amaklayenti ukuthi ashintshele ngokuzenzakalelayo kuma-algorithms athembeke kakhudlwana. Ngokusebenzisa lesi silungiselelo, isandiso sephrothokholi esikhethekile sinikwe amandla “[i-imeyili ivikelwe]", okuvumela iseva, ngemva kokufakazela ubuqiniso, ukwazisa iklayenti ngabo bonke okhiye bosokhaya abatholakalayo. Iklayenti lingabonisa laba khiye kufayela layo elithi ~/.ssh/known_hosts, elivumela okhiye bomsingathi ukuthi babuyekezwe futhi kwenze kube lula ukushintsha okhiye kuseva.

Ukusetshenziswa kwe-UpdateHostKeys kukhawulelwe izexwayiso ezimbalwa ezingase zisuswe esikhathini esizayo: ukhiye kufanele ukhonjwe ku-UserKnownHostsFile futhi ungasetshenziswa ku-GlobalKnownHostsFile; ukhiye kufanele ube ngaphansi kwegama elilodwa kuphela; isitifiketi sikakhiye wokusingatha akufanele sisetshenziswe; kumaski_abasingathi abaziwayo ngegama lomsingathi akufanele asetshenziswe; isilungiselelo se-VerifyHostKeyDNS kufanele sikhutshazwe; Ipharamitha ye-UserKnownHostsFile kufanele isebenze.

Ama-algorithms anconyiwe okuthutha ahlanganisa i-rsa-sha2-256/512 esekelwe ku-RFC8332 RSA SHA-2 (isekelwa kusukela ku-OpenSSH 7.2 futhi isetshenziswa ngokuzenzakalela), i-ssh-ed25519 (isekelwa kusukela ku-OpenSSH 6.5) kanye ne-ecdsa-sha2-nistp256/384 based ku-RFC521 ECDSA (isekelwa kusukela ku-OpenSSH 5656).

Ezinye izinguquko:

• Izinguquko zokuphepha:
  • Ukuba sengozini okudalwe ukukhulula kabusha indawo yenkumbulo esivele ikhululiwe (i-double-free) ilungisiwe ku-ejenti ye-ssh. Inkinga ibilokhu ikhona kusukela kwakhululwa i-OpenSSH 8.2 futhi ingase isetshenziswe uma umhlaseli ekwazi ukufinyelela isokhethi ye-ssh-ejenti kusistimu yendawo. Okwenza ukuxhashazwa kube nzima kakhulu ukuthi yimpande kuphela nomsebenzisi wangempela okwazi ukufinyelela isokhethi. Isimo sokuhlasela okungenzeka kakhulu ukuthi umenzeli uqondiswa kabusha ku-akhawunti elawulwa umhlaseli, noma kumsingathi lapho umhlaseli enokufinyelela okuyimpande.
  • I-sshd yengeze ukuvikeleka ekudluliseni amapharamitha amakhulu kakhulu ngegama lomsebenzisi kusistimu engaphansi ye-PAM, ekuvumela ukuthi uvimbele ubungozi kumamojula wesistimu we-PAM (Pluggable Authentication Module). Isibonelo, uguquko luvimba i-sshd ukuthi isetshenziswe njengevekhtha ukuze isebenzise ubungozi bezimpande ezisanda kutholwa e-Solaris (CVE-2020-14871).
• Izinguquko ezingase ziphule ukusebenzisana:
  • В ssh и sshd переработан экспериментальный метод обмена ключами, стойкий к подбору на квантовом компьютере. Квантовые компьютеры кардинально быстрее решают задачу разложения натурального числа на простые множители, которая лежит в основе современных асимметричных алгоритмов шифрования и эффективно не решаема на классических процессорах. Используемый метод основан на алгоритме NTRU Prime, разработанном для постквантумных криптосистем, и методе обмена ключами на базе эллиптических кривых X25519. Вместо [i-imeyili ivikelwe] метод теперь идентифицируется как [i-imeyili ivikelwe] (i-algorithm ye-sntrup4591761 ithathelwe indawo yi-sntrup761).
  • Ku-ssh naku-sshd, uhlelo okumenyezelwa ngalo ama-algorithms wesiginesha yedijithali lushintshiwe. I-ED25519 manje isinikezwa kuqala esikhundleni se-ECDSA.
  • Ku-ssh naku-sshd, ukusetha ikhwalithi ye-TOS/DSCP yamapharamitha wesevisi kumaseshini asebenzisanayo manje kwenziwa ngaphambi kokusungula uxhumano lwe-TCP.
  • Ukusekelwa kwe-Cipher kunqanyuliwe ku-ssh naku-sshd [i-imeyili ivikelwe], efana ne-aes256-cbc futhi yasetshenziswa ngaphambi kokugunyazwa kwe-RFC-4253.
  • Ngokuzenzakalelayo, ipharamitha ye-CheckHostIP ikhutshaziwe, inzuzo yakhona ayinalutho, kodwa ukusetshenziswa kwayo kwenza kube nzima kakhulu ukuzungezisa okubalulekile kubabungazi abalandela izilinganisi zomthwalo.
• Izilungiselelo ze-PerSourceMaxStartups kanye ne-PerSourceNetBlockSize zengezwe ku-sshd ukuze kukhawulwe ukuqina kwezibambi zokuqalisa ngokusekelwe ekhelini leklayenti. Le mingcele ikuvumela ukuthi ulawule kahle umkhawulo ekuqalisweni kwenqubo, uma kuqhathaniswa nesilungiselelo esivamile se-MaxStartups.
• Isilungiselelo esisha se-LogVerbose sengeziwe ku-ssh naku-sshd, okukuvumela ukuthi ukhuphule ngamandla izinga lolwazi lokususa iphutha olulahlwe kulogi, unekhono lokuhlunga ngezifanekiso, imisebenzi namafayela.
• Ku-ssh, lapho wamukela ukhiye omusha wokusingathwa, wonke amagama omethuleli namakheli e-IP ahlobene nokhiye ayaboniswa.
• ssh ivumela i-UserKnownHostsFile=ayikho inketho yokukhubaza ukusetshenziswa kwefayela le-known_hosts lapho uhlonza okhiye bosokhaya.
• Isilungiselelo se-KnowHostsCommand sengezwe ku-ssh_config ye-ssh, okukuvumela ukuthi uthole idatha ye-known_hosts ekuphumeni komyalo oshiwo.
• Kwengezwe inketho ye-PermitRemoteOpen ku-ssh_config ye-ssh ukukuvumela ukuthi ukhawulele indawo lapho usebenzisa inketho ye-RemoteForward nge-SOCKS.
• Ku-ssh kokhiye be-FIDO, isicelo se-PIN esiphindiwe sinikezwa uma kwenzeka umsebenzi we-digital wehluleka ngenxa ye-PIN engalungile kanye nomsebenzisi engatshelwanga nge-PIN (isibonelo, lapho idatha elungile ye-biometric ingatholakalanga futhi idivayisi iwele emuva ekufakweni kwe-PIN okwenziwa ngesandla).
• I-sshd yengeza usekelo lwezingcingo zesistimu ezengeziwe kunqubo yokuhlukanisa i-seccomp-bpf-based ku-Linux.
• Insiza ye-contrib/ssh-copy-id ibuyekeziwe.

Source: opennet.ru