{"id":181666,"date":"2026-05-22T18:25:08","date_gmt":"2026-05-22T16:25:08","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/iz-af_alg-v-linux-ubirayut-zero-copy-iz-soobrazhenij-bezopasnosti"},"modified":"2026-05-22T18:25:08","modified_gmt":"2026-05-22T16:25:08","slug":"iz-af_alg-v-linux-ubirayut-zero-copy-iz-soobrazhenij-bezopasnosti","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/iz-af_alg-v-linux-ubirayut-zero-copy-iz-soobrazhenij-bezopasnosti","title":{"rendered":"Z AF_ALG v Linuxu odstra\u0148uj\u00ed zero-copy z bezpe\u010dnostn\u00edch d\u016fvod\u016f","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

V subsyst\u00e9mu kryptografie Linux se p\u0159ipravuje odstran\u011bn\u00ed podpory zero-copy<\/strong> z rozhran\u00ed AF_ALG<\/strong> pro typy algoritm\u016f SKCIPHER<\/strong> a AEAD<\/strong>. Zm\u011bna ji\u017e je v stromu cryptodev a o\u010dek\u00e1v\u00e1 se odesl\u00e1n\u00ed do slou\u010den\u00ed Linux 7.2<\/strong>, kter\u00e9 by m\u011blo b\u00fdt otev\u0159eno v \u010dervnu. Podn\u011btem se staly rostouc\u00ed obavy o bezpe\u010dnost zero-copy mechanizm\u016f v j\u00e1d\u0159e, zvl\u00e1\u0161t\u011b po ned\u00e1vn\u00fdch zranitelnostech v kryptografick\u00e9m k\u00f3du Linuxu.<\/p>\n

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AF_ALG<\/strong> \u2014 to je u\u017eivatelsk\u00e9 rozhran\u00ed<\/a> kryptografick\u00e9ho API j\u00e1dra Linux. P\u0159es n\u011bj mohou programy p\u0159istupovat k implementac\u00edm \u0161ifrov\u00e1n\u00ed, hash\u016f a AEAD algoritm\u016f v j\u00e1d\u0159e jako k soket\u016fm. Dokumentace Linuxu zvl\u00e1\u0161\u0165 popisuje pro AF_ALG zero-copy re\u017eim p\u0159es splice() a vmsplice(), kdy se j\u00e1dro sna\u017e\u00ed vyhnout zbyte\u010dn\u00e9mu kop\u00edrov\u00e1n\u00ed dat do pam\u011bti j\u00e1dra.<\/p>\n

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Probl\u00e9m je v tom, \u017ee v p\u0159\u00edpad\u011b AF_ALG se takov\u00fd zisk v\u00fdkonnosti uk\u00e1zal jako nep\u0159\u00edli\u0161 d\u016fle\u017eit\u00fd a rizika jsou p\u0159\u00edli\u0161 velk\u00e1. Autor zm\u011bny, v\u00fdvoj\u00e1\u0159 kryptografick\u00e9 subsyst\u00e9my Linuxu Eric Biggers z Google, uvedl<\/a>, \u017ee zero-copy umo\u017e\u0148uje u\u017eivatelsk\u00e9mu prostoru spou\u0161t\u011bt kryptografick\u00e9 operace p\u0159\u00edmo nad str\u00e1nkami page cache soubor\u016f, nap\u0159\u00edklad bin\u00e1rn\u00edho souboru su, a tak\u00e9 vytv\u00e1\u0159\u00ed podm\u00ednky pro TOCTOU zranitelnosti, kdy se pam\u011b\u0165 m\u016f\u017ee m\u011bnit sou\u010dasn\u011b s operac\u00ed nad n\u00ed.<\/p>\n

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Jin\u00fdmi slovy, mechanismus u\u017eite\u010dn\u00fd v s\u00ed\u0165ov\u00e9m nebo souborov\u00e9m vstupu-v\u00fdstupu, v AF_ALG vypad\u00e1 jako p\u0159\u00edli\u0161 nebezpe\u010dn\u00e1 optimalizace. Samotn\u00fd AF_ALG, podle v\u00fdvoj\u00e1\u0159e, je nyn\u00ed v\u011bt\u0161inou udr\u017eov\u00e1n pro zp\u011btnou kompatibilitu s mal\u00fdm mno\u017estv\u00edm program\u016f, nap\u0159\u00edklad iwd, kter\u00e9 je\u0161t\u011b nebyly p\u0159evedeny na kryptografii v u\u017eivatelsk\u00e9m prostoru. P\u016fvodn\u011b byl AF_ALG navr\u017een i pro p\u0159\u00edstup k hardwarov\u00fdm kryptoprocesory, ale v praxi se uk\u00e1zal jako ne p\u0159\u00edli\u0161 efektivn\u00ed rozhran\u00ed pro tento \u00fakol.<\/p>\n

Je d\u016fle\u017eit\u00e9, \u017ee nejde o \u00fapln\u00e9 odstran\u011bn\u00ed splice() nebo sendfile() pro AF_ALG. Zm\u011bna je pops\u00e1na jako \"m\u011bkk\u00e9 poru\u0161en\u00ed\" kompatibility: p\u0159enos dat v po\u017eadavc\u00edch AF_ALG p\u0159es splice() a sendfile() bude i nad\u00e1le fungovat, ale j\u00e1dro nyn\u00ed bude prov\u00e1d\u011bt intern\u00ed stabiln\u00ed kopii dat p\u0159ed kryptografickou operac\u00ed. V\u00fdkon v n\u011bkter\u00fdch p\u0159\u00edpadech m\u016f\u017ee klesnout, ale u\u017eivatelsk\u00e9 API se form\u00e1ln\u011b nezhrout\u00ed.<\/p>\n

Z\u00e1rove\u0148 se zd\u016fraz\u0148uje, \u017ee zat\u00edm se zero-copy odstra\u0148uje z skcipher<\/strong> a aead<\/strong>. Podpora pro typ hash<\/strong> bude zva\u017eov\u00e1na zvl\u00e1\u0161\u0165.<\/p>\n

<\/p>\n

Kontext zm\u011bny je nep\u0159\u00edjemn\u00fd. Na konci dubna byla odhalena zranitelnost Chyba kop\u00edrov\u00e1n\u00ed<\/a><\/strong> (CVE-2026-31431<\/strong>) v algif_aead, co\u017e je p\u0159esn\u011b v u\u017eivatelsk\u00e9m kryptointerface AF_ALG. Badatel\u00e9 uk\u00e1zali, \u017ee kombinace AF_ALG, splice() a zvl\u00e1\u0161tnost\u00ed AEAD zpracov\u00e1n\u00ed umo\u017e\u0148ovala neprivilegovan\u00e9mu u\u017eivateli po\u0161kozovat vyrovn\u00e1vac\u00ed pam\u011b\u0165 str\u00e1nky, v\u010detn\u011b str\u00e1nek odpov\u00eddaj\u00edc\u00edch setuid bin\u00e1rk\u00e1m, a z\u00edsk\u00e1vat zv\u00fd\u0161en\u00ed privilegi\u00ed na \u00farove\u0148 root.<\/p>\n

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\n<\/p>\n

Objeven\u00ed Chyba kop\u00edrov\u00e1n\u00ed<\/a> bylo spojeno s optimalizac\u00ed z roku 2017, kter\u00e1 p\u0159evedla operace AEAD na zpracov\u00e1n\u00ed \u201ena m\u00edst\u011b\u201c; p\u0159i p\u0159enosu souboru p\u0159es splice() v AF_ALG j\u00e1dro pracovalo ne s kopi\u00ed, ale s odkazy na str\u00e1nky vyrovn\u00e1vac\u00ed pam\u011bti str\u00e1nky. V d\u016fsledku toho se \u010d\u00e1st dat, kter\u00e1 byla pova\u017eov\u00e1na pouze za vstupn\u00ed, mohla ocitnout v zapisovateln\u00e9m scatterlistu.<\/p>\n

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Odstran\u011bn\u00ed zero-copy z AF_ALG nen\u00ed jen jednor\u00e1zov\u00e1 oprava jedn\u00e9 zranitelnosti. Sp\u00ed\u0161e to je pokus odstranit cel\u00fd typ riskantn\u00edch sc\u00e9n\u00e1\u0159\u016f z m\u00e1lo pou\u017e\u00edvan\u00e9ho UAPI, kde zisk z optimalizace neospravedl\u0148uje slo\u017eitost a potenci\u00e1ln\u00ed n\u00e1sledky. Pro b\u011b\u017en\u00e9 u\u017eivatele pravd\u011bpodobn\u011b zm\u011bna z\u016fstane bez pov\u0161imnut\u00ed; pro vz\u00e1cn\u00e9 programy, kter\u00e9 aktivn\u011b pou\u017e\u00edvaj\u00ed AF_ALG p\u0159es splice() nebo sendfile(), m\u016f\u017ee doj\u00edt k poklesu v\u00fdkonu kv\u016fli dodate\u010dn\u00e9mu kop\u00edrov\u00e1n\u00ed.<\/p>\n

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

\u0412 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 \u043a\u0440\u0438\u043f\u0442\u043e\u0433\u0440\u0430\u0444\u0438\u0438 Linux \u0433\u043e\u0442\u043e\u0432\u0438\u0442\u0441\u044f \u0443\u0434\u0430\u043b\u0435\u043d\u0438\u0435 \u043f\u043e\u0434\u0434\u0435\u0440\u0436\u043a\u0438 zero-copy \u0438\u0437 \u0438\u043d\u0442\u0435\u0440\u0444\u0435\u0439\u0441\u0430 AF_ALG \u0434\u043b\u044f \u0442\u0438\u043f\u043e\u0432 \u0430\u043b\u0433\u043e\u0440\u0438\u0442\u043c\u043e\u0432 SKCIPHER \u0438 AEAD. \u0418\u0437\u043c\u0435\u043d\u0435\u043d\u0438\u0435 \u0443\u0436\u0435 \u043d\u0430\u0445\u043e\u0434\u0438\u0442\u0441\u044f \u0432 \u0434\u0435\u0440\u0435\u0432\u0435 cryptodev \u0438 \u043e\u0436\u0438\u0434\u0430\u0435\u0442\u0441\u044f \u043a \u043e\u0442\u043f\u0440\u0430\u0432\u043a\u0435 \u0432 \u043e\u043a\u043d\u043e \u0441\u043b\u0438\u044f\u043d\u0438\u044f Linux 7.2, \u043a\u043e\u0442\u043e\u0440\u043e\u0435 \u0434\u043e\u043b\u0436\u043d\u043e \u043e\u0442\u043a\u0440\u044b\u0442\u044c\u0441\u044f \u0432 \u0438\u044e\u043d\u0435. \u041f\u043e\u0432\u043e\u0434\u043e\u043c \u0441\u0442\u0430\u043b\u0438 \u0440\u0430\u0441\u0442\u0443\u0449\u0438\u0435 \u043e\u043f\u0430\u0441\u0435\u043d\u0438\u044f \u0432\u043e\u043a\u0440\u0443\u0433 \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 zero-copy-\u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u043e\u0432 \u0432 \u044f\u0434\u0440\u0435, \u043e\u0441\u043e\u0431\u0435\u043d\u043d\u043e \u043f\u043e\u0441\u043b\u0435 \u043d\u0435\u0434\u0430\u0432\u043d\u0438\u0445 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 \u043a\u0440\u0438\u043f\u0442\u043e\u0433\u0440\u0430\u0444\u0438\u0447\u0435\u0441\u043a\u043e\u043c \u043a\u043e\u0434\u0435 Linux. AF_ALG […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-181666","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Z AF_ALG v Linuxu se odstra\u0148uje zero-copy z bezpe\u010dnostn\u00edch d\u016fvod\u016f | ProHoster","description":"V subsyst\u00e9mu kryptografie Linuxu se p\u0159ipravuje odstran\u011bn\u00ed podpory zero-copy z rozhran\u00ed AF_ALG pro typy algoritm\u016f SKCIPHER a AEAD.","canonical_url":"https:\/\/prohoster.info\/cs\/blog\/news\/iz-af_alg-v-linux-ubirayut-zero-copy-iz-soobrazhenij-bezopasnosti","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"cs_CZ","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u0418\u0437 AF_ALG \u0432 Linux \u0443\u0431\u0438\u0440\u0430\u044e\u0442 zero-copy \u0438\u0437 \u0441\u043e\u043e\u0431\u0440\u0430\u0436\u0435\u043d\u0438\u0439 \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 | ProHoster","og:description":"\u0412 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0435 \u043a\u0440\u0438\u043f\u0442\u043e\u0433\u0440\u0430\u0444\u0438\u0438 Linux \u0433\u043e\u0442\u043e\u0432\u0438\u0442\u0441\u044f \u0443\u0434\u0430\u043b\u0435\u043d\u0438\u0435 \u043f\u043e\u0434\u0434\u0435\u0440\u0436\u043a\u0438 zero-copy \u0438\u0437 \u0438\u043d\u0442\u0435\u0440\u0444\u0435\u0439\u0441\u0430 AF_ALG \u0434\u043b\u044f \u0442\u0438\u043f\u043e\u0432 \u0430\u043b\u0433\u043e\u0440\u0438\u0442\u043c\u043e\u0432 SKCIPHER \u0438 AEAD.","og:url":"https:\/\/prohoster.info\/cs\/blog\/news\/iz-af_alg-v-linux-ubirayut-zero-copy-iz-soobrazhenij-bezopasnosti","og:image":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:secure_url":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:width":350,"og:image:height":350,"article:published_time":"2026-05-22T16:25:08+00:00","article:modified_time":"2026-05-22T16:25:08+00:00","article:publisher":"https:\/\/www.facebook.com\/prohoster","article:author":"https:\/\/www.facebook.com\/prohoster"},"aioseo_meta_data":[],"gt_translate_keys":[{"key":"link","format":"url"}],"_links":{"self":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts\/181666","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/comments?post=181666"}],"version-history":[{"count":0,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts\/181666\/revisions"}],"wp:attachment":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/media?parent=181666"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/categories?post=181666"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/tags?post=181666"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}