{"id":107119,"date":"2023-03-06T12:48:15","date_gmt":"2023-03-06T10:48:15","guid":{"rendered":"https:\/\/prohoster.info\/?p=107119"},"modified":"2023-03-06T16:13:41","modified_gmt":"2023-03-06T14:13:41","slug":"dlya-izbavleniya-glibc-ot-problemy-2038-goda-predlozheno-prekratit-ispolzovanie-utmp","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/dlya-izbavleniya-glibc-ot-problemy-2038-goda-predlozheno-prekratit-ispolzovanie-utmp","title":{"rendered":"Pro odstran\u011bn\u00ed probl\u00e9mu roku 2038 v Glibc bylo navr\u017eeno p\u0159estat pou\u017e\u00edvat utmp","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Thorsten Kukuk, vedouc\u00ed skupiny pro rozvoj technologi\u00ed budoucnosti ve spole\u010dnosti SUSE, kter\u00e1 se v\u011bnuje openSUSE MicroOS a SLE Micro, a d\u0159\u00edve 10 let vedl projekt SUSE LINUX Enterprise Server, navrhl zcela se zbavit souboru \/var\/run\/utmp v distribuc\u00edch, aby se pln\u011b vy\u0159e\u0161il probl\u00e9m roku 2038 v Glibc. N\u00e1vrh je p\u0159en\u00e9st v\u0161echna aplikace vyu\u017e\u00edvaj\u00edc\u00ed utmp, wtmp a lastlog na z\u00edsk\u00e1v\u00e1n\u00ed seznamu u\u017eivatel\u016f pomoc\u00ed systemd-logind. <\/p>\n

19. ledna 2038 dojde k p\u0159ete\u010den\u00ed \u010dasov\u00fdch \u010d\u00edta\u010d\u016f epochy definovan\u00fdch 32bitov\u00fdm typem time_t. V knihovn\u011b Glibc, navzdory zaveden\u00ed 64bitov\u00e9ho typu time_t, se pro zachov\u00e1n\u00ed kompatibility se 32bitov\u00fdmi aplikacemi v n\u011bkter\u00fdch p\u0159\u00edpadech na 64bitov\u00fdch platform\u00e1ch st\u00e1le pou\u017e\u00edv\u00e1 32bitov\u00fd typ time_t. Jedn\u00edm z t\u011bchto p\u0159\u00edpad\u016f je soubor \/var\/run\/utmp, kter\u00fd uchov\u00e1v\u00e1 \u00fadaje o u\u017eivatel\u00edch aktu\u00e1ln\u011b pracuj\u00edc\u00edch v syst\u00e9mu. Pole s \u010dasem v utmp se nastavuje pomoc\u00ed 32bitov\u00e9 hodnoty time_t. <\/p>\n

Jednodu\u0161e vym\u011bnit \u010dasov\u00e9 pole v utmp z 32bitov\u00e9ho na 64bitov\u00fd typ nebude mo\u017en\u00e9, proto\u017ee by to vedlo ke zm\u011bn\u011b ABI Glibc (zm\u011bn\u00ed se typ v funkc\u00edch, jako jsou login(), getutid() a utmpname()) a naru\u0161ilo by to kompatibilitu s aplikacemi, kter\u00e9 pou\u017e\u00edvaj\u00ed utmp, mezi n\u011b\u017e pat\u0159\u00ed w, who, uptime, login, su, sudo, useradd, systemd, sysvinit, tcsh, xterm spr\u00e1vcov\u00e9 plochy, emacs, openssh, qemu, samba, rsyslog apod. Kv\u016fli mno\u017estv\u00ed mo\u017en\u00fdch \u00faskal\u00ed a n\u00e1ro\u010dnosti byla my\u0161lenka na zm\u011bnu rozli\u0161en\u00ed typu time_t v utmp v\u00fdvoj\u00e1\u0159i Glibc odm\u00edtnuta. Ze stejn\u00e9ho d\u016fvodu byl odm\u00edtnut n\u00e1vrh vyu\u017e\u00edt existuj\u00edc\u00ed voln\u00e9 m\u00edsto ve struktu\u0159e utmp k p\u0159id\u00e1n\u00ed dal\u0161\u00edho 64bitov\u00e9ho pole pro \u010das. <\/p>\n

Krom\u011b toho zm\u011bna velikosti typu v utmp ne\u0159e\u0161\u00ed dal\u0161\u00ed existuj\u00edc\u00ed probl\u00e9my, kter\u00fdch bychom se tak\u00e9 r\u00e1di zbavili. Nap\u0159\u00edklad pro z\u00e1pis do utmp jsou pot\u0159eba speci\u00e1ln\u00ed pr\u00e1va, co\u017e vy\u017eaduje poskytnut\u00ed dal\u0161\u00edm privileg\u00edm proces\u016fm. Dal\u0161\u00ed probl\u00e9m souvis\u00ed s t\u00edm, \u017ee architektura utmp umo\u017e\u0148uje m\u00edstn\u00edm u\u017eivatel\u016fm prov\u00e1d\u011bn\u00ed DoS \u00fatok\u016f, co\u017e m\u016f\u017ee v\u00e9st k naru\u0161en\u00ed \u010dinnosti slu\u017eby utmp skrze manipulace se z\u00e1mky na soubor, \u010d\u00edm\u017e nen\u00ed mo\u017en\u00e9 m\u00edt jistotu, \u017ee obsah utmp odr\u00e1\u017e\u00ed skute\u010dn\u00fd stav v syst\u00e9mu. Navrhovalo se pou\u017e\u00edt dal\u0161\u00ed pozad\u00ed proces pro zpracov\u00e1n\u00ed p\u0159\u00edstupu k utmp, ale pro podobn\u00e9 \u00fakoly ji\u017e existuje proces systemd-logind a spu\u0161t\u011bn\u00ed dal\u0161\u00edho specializovan\u00e9ho procesu nen\u00ed vhodn\u00e9 (aplikac\u00edm by bylo nutn\u00e9 p\u0159ed\u00e1vat data sou\u010dasn\u011b dv\u011bma zpracovatel\u016fm). <\/p>\n

I kdy\u017e probl\u00e9m s DoS \u00fatoky je vy\u0159e\u0161en, obsah utmp z\u016fst\u00e1v\u00e1 pouze informativn\u00ed a nezaru\u010duje odraz skute\u010dnosti. Nap\u0159\u00edklad r\u016fzn\u00e9 emul\u00e1tory a multiplexory termin\u00e1l\u016f zobrazuj\u00ed sv\u016fj stav r\u016fzn\u011b \u2014 spu\u0161t\u011bn\u00ed p\u011bti termin\u00e1l\u016f GNOME povede k zobrazen\u00ed jednoho u\u017eivatele v utmp, zat\u00edmco spu\u0161t\u011bn\u00ed p\u011bti termin\u00e1l\u016f konsole nebo xterm v KDE \u2014 \u0161esti. Podobn\u011b se li\u0161\u00ed chov\u00e1n\u00ed screen a tmux, v prvn\u00edm p\u0159\u00edpad\u011b je ka\u017ed\u00fd sezen\u00ed zaznamen\u00e1no jako samostatn\u00fd u\u017eivatel, zat\u00edmco ve druh\u00e9m je vid\u011bt pouze jeden u\u017eivatel pro v\u0161echna sezen\u00ed. <\/p>\n

V\u00fdsledkem je, \u017ee jako nejjednodu\u0161\u0161\u00ed \u0159e\u0161en\u00ed se navrhuje p\u0159ev\u00e9st v\u0161echny aplikace na vyu\u017e\u00edv\u00e1n\u00ed ji\u017e existuj\u00edc\u00ed alternativn\u00ed slu\u017eby systemd-logind a po odstran\u011bn\u00ed aktu\u00e1ln\u00edch program\u016f, kter\u00e9 se obracej\u00ed na utmp, p\u0159estat zapisovat do utmp. Pro nahrazen\u00ed wtmp je navr\u017eeno p\u0159ipravit softwarov\u00e9 rozhran\u00ed pro z\u00e1pis a \u010dten\u00ed informac\u00ed o u\u017eivatel\u00edch pomoc\u00ed systemd-journald. Nutn\u00e9 funkce pro poskytov\u00e1n\u00ed n\u00e1hradn\u00edch utmp dat p\u0159es libsystemd s pou\u017eit\u00edm API sd-login.h nebo p\u0159es DBUS ji\u017e byly zahrnuty do k\u00f3dov\u00e9 z\u00e1kladny dal\u0161\u00edho vyd\u00e1n\u00ed systemd 254.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0422\u043e\u0440\u0441\u0442\u0435\u043d \u041a\u0443\u043a\u0443\u043a (Thorsten Kukuk), \u043b\u0438\u0434\u0435\u0440 \u0433\u0440\u0443\u043f\u043f\u044b \u043f\u043e \u0440\u0430\u0437\u0432\u0438\u0442\u0438\u044e \u0442\u0435\u0445\u043d\u043e\u043b\u043e\u0433\u0438\u0439 \u0431\u0443\u0434\u0443\u0449\u0435\u0433\u043e \u0432 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 SUSE (Future Technology Team, \u0440\u0430\u0437\u0432\u0438\u0432\u0430\u0435\u0442 openSUSE MicroOS \u0438 SLE Micro), \u0440\u0430\u043d\u0435\u0435 10 \u043b\u0435\u0442 \u0440\u0443\u043a\u043e\u0432\u043e\u0434\u0438\u0432\u0448\u0438\u0439 \u043f\u0440\u043e\u0435\u043a\u0442\u043e\u043c SUSE LINUX Enterprise Server, \u043f\u0440\u0435\u0434\u043b\u043e\u0436\u0438\u043b \u0438\u0437\u0431\u0430\u0432\u0438\u0442\u044c\u0441\u044f \u043e\u0442 \u0444\u0430\u0439\u043b\u0430 \/var\/run\/utmp \u0432 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 \u0434\u043b\u044f \u043f\u043e\u043b\u043d\u043e\u0433\u043e \u0440\u0435\u0448\u0435\u043d\u0438\u044f \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b 2038 \u0433\u043e\u0434\u0430 \u0432 Glibc. \u0412\u0441\u0435 \u043f\u0440\u0438\u043b\u043e\u0436\u0435\u043d\u0438\u044f, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u044e\u0449\u0438\u0435 utmp, wtmp \u0438 lastlog, \u043f\u0440\u0435\u0434\u043b\u0430\u0433\u0430\u0435\u0442\u0441\u044f \u043f\u0435\u0440\u0435\u0432\u0435\u0441\u0442\u0438 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