{"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\/da\/blog\/news\/dlya-izbavleniya-glibc-ot-problemy-2038-goda-predlozheno-prekratit-ispolzovanie-utmp","title":{"rendered":"For at fjerne Glibc's problem med \u00e5r 2038 foresl\u00e5s det at stoppe brugen af utmp","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Thorsten Kukuk, leder af Future Technology Team hos SUSE, der udvikler openSUSE MicroOS og SLE Micro, og tidligere leder af SUSE LINUX Enterprise Server i 10 \u00e5r, har foresl\u00e5et at fjerne filen \/var\/run\/utmp fra distributionerne for fuldst\u00e6ndig at l\u00f8se 2038-problemet i Glibc. Det foresl\u00e5s, at alle applikationer, der bruger utmp, wtmp og lastlog, overg\u00e5r til at hente brugerlisten via systemd-logind. <\/p>\n

Den 19. januar 2038 vil der ske et overflow af epoch-t\u00e6llere, defineret af den 32-bit type time_t. I Glibc-biblioteket, p\u00e5 trods af introduktionen af 64-bit type time_t, bliver den 32-bit type time_t i visse tilf\u00e6lde fortsat brugt p\u00e5 64-bit platforme for at bevare kompatibiliteten med 32-bit applikationer. Et af disse tilf\u00e6lde er filen \/var\/run\/utmp, der gemmer data om brugere, der i \u00f8jeblikket arbejder i systemet. Tidsfeltet i utmp er defineret ved hj\u00e6lp af et 32-bit time_t-v\u00e6rdi. <\/p>\n

Det er ikke muligt blot at \u00e6ndre tidsfeltet i utmp fra 32-bit til 64-bit type, da det vil medf\u00f8re en \u00e6ndring af ABI i Glibc (typen vil \u00e6ndre sig i funktioner som login(), getutid() og utmpname()) og bryde kompatibiliteten med applikationer, der bruger utmp, herunder w, who, uptime, login, su, sudo, useradd, systemd, sysvinit, tcsh, xterm display managers, emacs, openssh, qemu, samba, rsyslog osv. P\u00e5 grund af de mange mulige faldgruber og det kr\u00e6vende arbejde blev ideen om at \u00e6ndre bitdybden af time_t i utmp forkastet af Glibc-udviklerne. Af samme grund blev muligheden for at bruge det frie rum i utmp-strukturen til at tilf\u00f8je et ekstra 64-bit tidsfelt ogs\u00e5 forkastet. <\/p>\n

Derudover l\u00f8ser \u00e6ndringen af typen i utmp ikke de andre eksisterende problemer, som vi ogs\u00e5 gerne vil fjerne. For eksempel kr\u00e6ver registrering i utmp s\u00e6rlige rettigheder, hvilket kr\u00e6ver, at processer gives ekstra privilegier. En anden problematik er, at arkitekturen i utmp tillader lokale brugere at udf\u00f8re DoS-angreb, hvilket f\u00f8rer til forstyrrelse af utmp-tjenesten gennem manipulation med filens l\u00e5sninger, hvilket skaber usikkerhed om, at indholdet af utmp afspejler den virkelige tilstand i systemet. Der var forslag om at bruge en ekstra baggrundsproces til at h\u00e5ndtere adgangen til utmp, men til s\u00e5danne opgaver eksisterer systemd-logind allerede, og det ville ikke v\u00e6re fornuftigt at starte endnu en specialiseret proces (applikationer ville skulle sende data til to h\u00e5ndteringsprocesser samtidig). <\/p>\n

Selv n\u00e5r man l\u00f8ser problemer med DoS-angreb, forbliver indholdet i utmp kun informativt og garanterer ikke en \u00e5rlig virkelighed. For eksempel afspejler forskellige emulatorer og terminalmultiplexere deres tilstand forskelligt \u2014 opstart af fem GNOME-terminaler f\u00f8rer til, at utmp viser \u00e9n bruger, mens opstart af fem terminaler i konsole eller xterm i KDE viser seks. Adf\u00e6rden er ogs\u00e5 forskellig for screen og tmux; i f\u00f8rstn\u00e6vnte t\u00e6lles hver session som en separat bruger, mens der i sidstn\u00e6vnte kun vises en bruger for alle sessioner. <\/p>\n

Som det mest enkle l\u00f8sninger foresl\u00e5s det at overf\u00f8re alle applikationer til at bruge den allerede eksisterende alternative tjeneste systemd-logind, og n\u00e5r der ikke l\u00e6ngere er aktuelle programmer, der henvender sig til utmp, oph\u00f8re med at registrere i utmp. For at erstatte wtmp foresl\u00e5s det at forberede programmeringsgr\u00e6nseflader til at skrive og l\u00e6se oplysninger om brugere via systemd-journald. De n\u00f8dvendige funktioner til at levere erstatning av utmp-data gennem libsystemd med brug af API sd-login.h eller via DBUS er allerede inkluderet i kodebasen for den n\u00e6ste version af systemd 254.
\n
Kilde: 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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