{"id":105257,"date":"2022-10-06T15:36:38","date_gmt":"2022-10-06T13:36:38","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/proekt-llvm-razvivaet-sredstva-dlya-bezopasnoj-raboty-s-buferami-v-c"},"modified":"2022-10-06T15:36:38","modified_gmt":"2022-10-06T13:36:38","slug":"proekt-llvm-razvivaet-sredstva-dlya-bezopasnoj-raboty-s-buferami-v-c","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/proekt-llvm-razvivaet-sredstva-dlya-bezopasnoj-raboty-s-buferami-v-c","title":{"rendered":"Projekt LLVM vyv\u00edj\u00ed n\u00e1stroje pro bezpe\u010dnou pr\u00e1ci s buffery v C++.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V\u00fdvoj\u00e1\u0159i projektu LLVM navrhli \u0159adu zm\u011bn, kter\u00e9 maj\u00ed za c\u00edl pos\u00edlit bezpe\u010dnost kritick\u00fdch projekt\u016f v jazyce C++ a poskytnout prost\u0159edky pro odstran\u011bn\u00ed chyb zp\u016fsoben\u00fdch p\u0159ekro\u010den\u00edm povolen\u00fdch limit\u016f buffer\u016f. Pr\u00e1ce je zam\u011b\u0159ena na dv\u011b oblasti: poskytov\u00e1n\u00ed v\u00fdvojov\u00e9ho modelu, kter\u00fd umo\u017e\u0148uje bezpe\u010dnou pr\u00e1ci s buffery, a pos\u00edlen\u00ed ochrany standardn\u00ed knihovny funkc\u00ed libc++. <\/p>\n

Navrhovan\u00fd model bezpe\u010dn\u00e9ho programov\u00e1n\u00ed pro C++ p\u0159edpokl\u00e1d\u00e1 pou\u017eit\u00ed t\u0159\u00edd poskytovan\u00fdch standardn\u00ed knihovnou p\u0159i pr\u00e1ci s buffery m\u00edsto manipulace s hol\u00fdmi ukazateli. Nap\u0159\u00edklad se navrhuje pou\u017e\u00edvat t\u0159\u00eddy std::array, std::vector a std::span, do kter\u00fdch bude p\u0159id\u00e1na kontrola p\u0159ekro\u010den\u00ed hranic p\u0159id\u011blen\u00e9 pam\u011bti prov\u00e1d\u011bn\u00e1 za b\u011bhu. <\/p>\n

Aby se bojovalo proti nebezpe\u010dn\u00fdm programovac\u00edm praktik\u00e1m v clang, navrhuje se generovat varov\u00e1n\u00ed p\u0159eklada\u010de pro v\u0161echny aritmetick\u00e9 operace s ukazateli, podobn\u00e1 varov\u00e1n\u00edm linteru clang-tidy, kter\u00e1 se zobrazuj\u00ed p\u0159i pou\u017eit\u00ed flagu «cppcoreguidelines-pro-bounds-pointer-arithmetic», jeho\u017e podpora se objev\u00ed ve verzi LLVM 16. K aktivaci t\u011bchto varov\u00e1n\u00ed bude do clang p\u0159id\u00e1n samostatn\u00fd flag, kter\u00fd nebude ve v\u00fdchoz\u00edm nastaven\u00ed aktivov\u00e1n. <\/p>\n

V libc++ je pl\u00e1nov\u00e1na realizace voliteln\u00e9ho re\u017eimu pos\u00edlen\u00e9 ochrany, p\u0159i jeho\u017e zapnut\u00ed budou b\u011bhem b\u011bhu zachycov\u00e1ny n\u011bkter\u00e9 situace vedouc\u00ed k nejednozna\u010dn\u00e9mu chov\u00e1n\u00ed. Nap\u0159\u00edklad v t\u0159\u00edd\u00e1ch std::span a std::vector bude sledov\u00e1no p\u0159\u00edstupov\u00e1n\u00ed za hranice p\u0159id\u011blen\u00e9 oblasti pam\u011bti, co\u017e p\u0159i zji\u0161t\u011bn\u00ed povede k hav\u00e1rii programu. V\u00fdvoj\u00e1\u0159i se domn\u00edvaj\u00ed, \u017ee p\u0159id\u00e1n\u00ed takov\u00fdch zm\u011bn udr\u017e\u00ed libc++ v souladu se standardy C++, proto\u017ee volba metody zpracov\u00e1n\u00ed p\u0159\u00edpad\u016f nejednozna\u010dn\u00e9ho chov\u00e1n\u00ed le\u017e\u00ed na v\u00fdvoj\u00e1\u0159\u00edch knihovny, kte\u0159\u00ed mohou nejednozna\u010dn\u00e9 chov\u00e1n\u00ed interpretovat jako selh\u00e1n\u00ed, kter\u00e9 vy\u017eaduje ukon\u010den\u00ed programu. <\/p>\n

Kontroly prov\u00e1d\u011bn\u00e9 za b\u011bhu v libc++ pl\u00e1nuj\u00ed rozd\u011blit do kategori\u00ed, kter\u00e9 budou mo\u017en\u00e9 zap\u00ednat samostatn\u011b. N\u011bkter\u00e9 z navrhovan\u00fdch kontrol, kter\u00e9 nevedou ke zkroucen\u00ed operac\u00ed nebo zm\u011bn\u011b ABI, ji\u017e byly realizov\u00e1ny v r\u00e1mci bezpe\u010dn\u00e9ho re\u017eimu libc++ (safe mode). <\/p>\n

D\u00e1le se pl\u00e1nuje p\u0159ipravit n\u00e1stroje pro \u00fapravu k\u00f3du, kter\u00e9 umo\u017e\u0148uj\u00ed nahrazovat prom\u011bnn\u00e9 s hol\u00fdmi ukazateli kontejnery a aplikovat alternativn\u00ed zpracovatele v situac\u00edch, kdy kontejner nem\u016f\u017ee p\u0159\u00edmo nahradit ukazatel (nap\u0159\u00edklad konstrukce «if(array_pointer)» m\u016f\u017ee b\u00fdt p\u0159evedena na «if(span.data()»). \u00dapravy mohou b\u00fdt aplikov\u00e1ny nejen na lok\u00e1ln\u00ed prom\u011bnn\u00e9, ale tak\u00e9 na parametry typ\u016f s ukazateli.
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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